<PAGE>


                                                                 Exhibit 10.15

                                INVESTMENT AGREEMENT


     THIS AGREEMENT is entered into as of June 16, 1998, by and among
BIONEBRASKA, INC., a Delaware corporation (the "Company"), and MEDTRONIC, INC.,
a Minnesota corporation ("Medtronic").


                                     RECITALS:

     A.   The Company desires to issue and sell to Medtronic, and Medtronic
desires to purchase from the Company, upon the terms and subject to the
conditions set forth in this Agreement, shares of the Company's Series G
Convertible Preferred Stock, par value $.01 per share ("Series G Preferred"), as
provided for in Section 2.1 hereof.

     B.   As a condition to Medtronic's investment described above, the Company
is willing to grant to Medtronic certain rights as set forth in this Agreement
and the Registration Rights Agreement (as defined below).

     NOW, THEREFORE, in consideration of the respective representations,
warranties, covenants, and agreements contained herein, and for other valuable
consideration, the receipt and adequacy of which is hereby acknowledged, the
parties hereto agree as follows:


                                     ARTICLE 1
                                    DEFINITIONS

     1.1  SPECIFIC DEFINITIONS.  As used in this Agreement, the following terms
shall have the meanings set forth or as referenced below:

"AFFILIATE" of a specified person (natural or juridical) means a person that
directly, or indirectly through one or more intermediaries, controls, or is
controlled by, or is under common control with, the person specified.  "Control"
shall mean ownership of more than 50% of the shares of stock entitled to vote
for the election of directors in the case of a corporation, and more than 50% of
the voting power in the case of a business entity other than a corporation.

"AGREEMENT" means this Agreement and all Exhibits and Schedules hereto.

"BOARD" means the Company's Board of Directors.

"CAPITAL STOCK" means any of the authorized shares of the Company.

"cGMP" means current Good Manufacturing Practices.


                                        1


<PAGE>


[***]

"CLOSING" shall have the meaning set forth in Section 2.3.

"COMMON STOCK" means the shares of Common Stock of the Company, par value $.01
per share.

"CONFIDENTIAL INFORMATION" means know-how, trade secrets, and unpublished
information disclosed (whether before or during the term of this Agreement) by
one of the parties (the "disclosing party") to the other party (the "receiving
party") or generated under this Agreement, excluding information that:

          (a)  was already in the possession of the receiving party prior to its
     receipt from the disclosing party or has been independently developed by
     the receiving party without breach of this Agreement or use of any
     Confidential Information of the other party (provided that the receiving
     party is able to provide the disclosing party with reasonable documentary
     proof thereof);

          (b)  is or becomes part of the public domain by reason of acts not
     attributable to the receiving party;

          (c)  is or becomes available to the receiving party from a source
     other than the disclosing party, which source, to the best of the receiving
     party's knowledge, has rightfully obtained such information and has no
     obligation of nondisclosure or confidentiality to the disclosing party with
     respect thereto;

          (d)  is made available by the disclosing party to a third party
     unaffiliated with the disclosing party on an unrestricted basis; or

          (e)  has been or must be publicly disclosed by reason of legal,
     accounting, or regulatory requirements beyond the reasonable control, and
     despite the reasonable efforts, of the receiving party.

     All Confidential Information disclosed by one party to the other under this
Agreement shall be in writing and bear a legend stating "Proprietary,"
"Confidential," or words of similar import or, if disclosed in any manner other
than writing, shall be preceded by an oral statement indicating that the
information is Company proprietary or confidential, and shall be followed by
transmittal of a reasonably detailed written summary of the information provided
to the receiving party within 30 days and identified as Confidential Information
bearing the legend described above.

"EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended, and all
regulations promulgated thereunder.


*  Confidential portions of this document indicated by [***] have been omitted
and filed separately with the Commission.

                                        2


<PAGE>

"FDA" means the United States Food and Drug Administration.

"FIELD" [***]

[***]

"INTELLECTUAL PROPERTY" means letters patent and patent applications;
trademarks, service marks and registrations thereof and applications therefor;
copyrights and copyright registrations and applications; all discoveries, ideas,
inventions, technology, know-how, trade secrets, processes, formulas, drawings
and designs, notebooks, computer programs and software, and licenses; and all
amendments, modifications, and improvements to any of the foregoing.

"KNOWLEDGE" means actual knowledge of a fact or the knowledge that such person
could reasonably be expected to have based on reasonable inquiry.  The knowledge
of an entity shall include the knowledge of such entity's executive officers.

"LIENS" means liens, mortgages, charges, security interests, claims, voting
trusts, pledges, encumbrances, options, assessments, restrictions, or
third-party or spousal interests of any nature.

"PREFERRED STOCK" means shares of the Company's Series A Preferred Stock, Series
B Convertible Preferred Stock, Series C Convertible Preferred Stock, Series D
Convertible Preferred Stock, Series E Convertible Preferred Stock, Series F
Convertible Preferred Stock, and Series G Convertible Preferred Stock.

"PURCHASED SHARES" means the shares of Series G Preferred purchased by Medtronic
pursuant to Section 2.1.

"REGISTRATION RIGHTS AGREEMENT" means the Registration Rights Agreement of even
date herewith between Medtronic and the Company.

"SEC" shall mean the Securities and Exchange Commission or any other federal
agency at the time administering the Securities Act.

"SECURITIES ACT" means the Securities Act of 1933, as amended, and all
regulations promulgated thereunder.

     1.2  DEFINITIONAL PROVISIONS.

          (a)  The words "hereof," "herein," and "hereunder" and words of
     similar import, when used in this Agreement, shall refer to this Agreement
     as a whole and not to any particular provisions of this Agreement.

          (b)  Terms defined in the singular shall have a comparable meaning
     when used in the plural, and vice versa.

*  Confidential portions of this document indicated by [***] have been omitted
and filed separately with the Commission.

                                        3


<PAGE>

          (c)  References to an "Exhibit" or to a "Schedule" are, unless
     otherwise specified, to one of the Exhibits or Schedules attached to or
     referenced in this Agreement, and references to an "Article" or a "Section"
     are, unless otherwise specified, to one of the Articles or Sections of this
     Agreement.

          (d)  The term "person" includes any individual, partnership, joint
     venture, corporation, trust, unincorporated organization or government or
     any department or agency thereof.


                                     ARTICLE 2
                        PURCHASE OF SERIES G PREFERRED STOCK

     2.1  PURCHASE AND SALE OF SHARES; PURCHASE PRICE.  At or before the
Closing, the Company shall adopt and file with the Secretary of State of
Delaware a Certificate of Designation relating to the Series G Preferred in the
form attached hereto as EXHIBIT A.  Subject to the terms and conditions hereof,
the Company shall issue and deliver to Medtronic, and Medtronic shall purchase
from the Company, 50,000 shares of Series G Preferred (the "Purchased Shares"),
which shall have a face value and purchase price of $100 per share and an
aggregate purchase price of $5,000,000.  As described in the Certificate of
Designation, the Purchased Shares shall initially be convertible into shares of
Common Stock based on a price per share of Common Stock of $7.75.  Certificates
representing the Purchased Shares shall be issued on the Closing Date in form
acceptable to Medtronic and its counsel.

     2.2  PAYMENT OF PURCHASE PRICE.  Medtronic shall pay the Purchase Price to
the Company on the Closing Date via wire transfer of funds to an account
designated by the Company.

     2.3  CLOSING.  The consummation of the transactions contemplated by this
Agreement (the "Closing") shall take place, following the satisfaction or waiver
of all of the conditions to Closing contained in this Agreement, at 10:00 a.m.
on June 16, 1998, or at such other time as shall be agreed upon by Medtronic and
the Company (the "Closing Date").  The Closing shall take place (i) at the
office of Fredrikson & Byron, P.A. in Minneapolis, Minnesota, or (ii) on the
mutual agreement of the parties, by delivery via facsimile transmission (with
originals sent by overnight courier service) of the documents to be delivered at
the Closing, or (iii) at such other place or in such other manner as the parties
mutually agree.

     2.4  USE OF PROCEEDS.  The Company and Medtronic agree that the proceeds
received by the Company from the sale of the Purchased Shares hereunder shall be
used by the Company for [***]

*  Confidential portions of this document indicated by [***] have been omitted
and filed separately with the Commission.

                                        4


<PAGE>



                                     ARTICLE 3
                 MEDTRONIC RIGHTS OF FIRST OFFER AND FIRST REFUSAL

     3.1  RIGHT OF FIRST REFUSAL ON NEW ISSUANCES.

          (a)  The Company hereby grants to Medtronic a right of first refusal
     to purchase all or part of its pro rata share of any New Securities (as
     defined below) that the Company may, from time to time, propose to sell and
     issue, subject to the terms and conditions set forth below.  Medtronic's
     pro rata share, for purposes of this Section 3.1, shall equal a fraction,
     the numerator of which is the number of issued and outstanding shares of
     Common Stock then held by Medtronic or into which the shares of Preferred
     Stock then held by Medtronic are convertible and the denominator of which
     is the total number of shares of Common Stock then issued and outstanding
     and/or into which the shares of all preferred stock of the Company then
     issued and outstanding are convertible.

          (b)  "New Securities" means any Capital Stock, whether or not now
     authorized, and rights, options, or warrants to purchase Capital Stock, and
     securities of any kind whatsoever that are, or may become, convertible into
     Capital Stock; provided, however, that the term "New Securities" does not
     include:

               (i)   Shares of Common Stock issuable upon conversion of
          outstanding shares of Preferred Stock;

               (ii)  Shares of Series F Convertible Preferred Stock currently
          being offered to investors by the Company, any warrants to purchase
          Common Stock issued to any agents in connection with such offering,
          and any shares of Common Stock issued to any agent in lieu of
          commissions in connection with such offering;

               (iii) Shares of Common Stock issuable to officers, directors, or
          employees of or consultants to the Company granted pursuant to the
          Company's 1993 Stock Plan, as it has been, and may be, amended from
          time to time;

               (iv)  Shares of Common Stock issued or issuable upon exercise of
          warrants to purchase shares of Common Stock outstanding on the date
          hereof;

               (v)   Shares of Common Stock issued upon conversion of the
          Company's bridge notes outstanding on the date hereof;

               (vi)  Shares of Common Stock sold to the public pursuant to a
          registration statement filed under the Securities Act; or


                                        5


<PAGE>



               (vii) Securities issued as a result of any stock split, stock
          dividend, or reclassification of Common Stock, distributable on a pro
          rata basis to all holders of Common Stock.

          (c)  In the event the Company intends to issue New Securities, it
     shall give Medtronic written notice of such intention, describing the type
     of New Securities to be issued, the price thereof, the proposed offeree(s),
     and the general terms upon which the Company proposes to effect such
     issuance.  Medtronic shall have 15 days from the date of receipt of such
     notice to agree to purchase all or part of its pro rata share of such New
     Securities for the price and upon the general terms and conditions
     specified in the Company's notice by giving written notice to the Company
     stating the quantity of New Securities to be so purchased.

          (d)  In the event that Medtronic fails to exercise the foregoing right
     of first refusal with respect to any New Securities within such 15-day
     period, the Company may within 120 days thereafter sell any or all of such
     New Securities not agreed to be purchased by Medtronic, at a price and upon
     general terms no more favorable to the purchaser(s) thereof than specified
     in the notice given to Medtronic pursuant to paragraph (c) above.  In the
     event that the Company does not sell such New Securities within such
     120-day period, the Company shall not thereafter issue or sell any New
     Securities without first offering such New Securities to Medtronic in the
     manner described above.

          (e)  The rights of Medtronic described in this Section 3.1 shall
     terminate upon the closing of the sale of the Company's Common Stock in an
     underwritten public offering registered under the Securities Act that
     results in aggregate gross proceeds to the Company of not less than
     $7,000,000.

     3.2  [***]

          (a)  [***]

          (b)  [***]
               (i)   [***]

               (ii)  [***]

     [***]

          (c)  [***]

          (d)  [***]

*  Confidential portions of this document indicated by [***] have been omitted
and filed separately with the Commission.

                                        6


<PAGE>




                                     ARTICLE 4
                   REPRESENTATIONS AND WARRANTIES OF THE COMPANY

     Except as set forth on the attached Disclosure Schedule, the Company
represents and warrants to Medtronic as follows:

     4.1  ORGANIZATION, QUALIFICATION AND CORPORATE POWER. The Company is a
corporation duly incorporated, validly existing, and in good standing under the
laws of the State of Delaware and is duly licensed or qualified to transact
business as a foreign corporation and is in good standing in each jurisdiction
in which the nature of the business transacted by it or the character of the
properties owned or leased by it requires such licensing or qualification and
where the failure to be so licensed or qualified could have a material adverse
effect upon the Company or its business.  The Company has the corporate power
and authority to own and hold its properties and to carry on its business as now
conducted and as proposed to be conducted, to execute, deliver and perform this
Agreement, and to issue, sell, and deliver the Purchased Shares.

     4.2  AUTHORIZATION OF AGREEMENT, ETC.

          (a)  The execution and delivery by the Company of this Agreement, the
     performance by the Company of its obligations hereunder, and the issuance,
     sale, and delivery of the Purchased Shares have been duly authorized by all
     requisite corporate action and will not violate any provision of law, any
     order of any court or other agency of government, the Certificate of
     Incorporation or the Bylaws of the Company, as amended, or any provision of
     any indenture, agreement or other instrument to which the Company or any of
     its Affiliates, properties or assets is bound, or conflict with, result in
     a breach of or constitute (with due notice or lapse of time or both) a
     default under any such indenture, agreement or other instrument, or result
     in the creation or imposition of any lien, charge, restriction, claim or
     encumbrance of any nature whatsoever upon any of the properties or assets
     of the Company or its Affiliates.

          (b)  The Purchased Shares have been duly authorized and validly
     issued, and are fully paid and nonassessable shares of Series G Preferred
     with no personal liability attaching to the ownership thereof and are free
     and clear of all Liens imposed by or through the Company.  Neither the
     issuance nor the sale or delivery of the Purchased Shares is subject to any
     preemptive right of stockholders of the Company or to any right of first
     refusal or other right in favor of any person that has not been complied
     with or duly waived.  Assuming, and after taking into account, the sale and
     issuance of all of the shares of Capital Stock described in Section
     3.1(b)(ii) hereof, the Purchased Shares constitute approximately 6.5
     percent of the issued and outstanding shares of Common Stock of the
     Company, on an as-converted and fully-diluted basis.

     4.3  VALIDITY.  This Agreement has been duly executed and delivered by the
Company and constitutes the legal, valid, and binding obligations of the
Company, enforceable in accordance with its terms, subject, as to the
enforcement of remedies, to the discretion of the courts in awarding equitable
relief and to applicable bankruptcy, reorganization, insolvency, moratorium, and
similar laws affecting the rights of creditors generally.


                                        7


<PAGE>

     4.4  FINANCIAL STATEMENTS.  The Company has furnished to Medtronic (i) the
audited balance sheet of the Company as of December 31, 1997 (the "Balance
Sheet"), and the related statements of operations, shareholders' equity, and
cash flows of the Company for the year then ended, and (ii) the unaudited
balance sheet of the Company as of March 31, 1998 (the "March 31 Balance
Sheet"), and the related statements of operations, shareholders' equity, and
cash flows for the month then ended.  The Balance Sheet and related financial
statements for the year ended December 31, 1997 have been prepared in accordance
with generally accepted accounting principles consistently applied, and all of
the financial statements described in this Section 4.4 fairly present the
financial position of the Company as of the dates thereof and the results of its
operations for the periods then ended.  Since the date of the March 31 Balance
Sheet and except as disclosed on the Disclosure Schedule, (i) there has been no
change in the assets, liabilities or financial condition of the Company from
that reflected in the March 31 Balance Sheet except for changes in the ordinary
course of business that in the aggregate have not been materially adverse, and
(ii) none of the business, prospects, financial condition, operations, property
or affairs of the Company has been materially adversely affected by any
occurrence or development, individually or in the aggregate, whether or not
insured against.

     4.5  LITIGATION; COMPLIANCE WITH LAW.  There is no (i) action, suit, claim,
proceeding or investigation pending or, to the Company's knowledge, threatened
against or affecting the Company, at law or in equity, or before or by any
federal, state, municipal or other governmental department, commission, board,
bureau, agency or instrumentality, domestic or foreign, (ii) arbitration
proceeding relating to the Company pending under collective bargaining
agreements or otherwise, or (iii) governmental inquiry pending or, to the
Company's knowledge, threatened against or affecting the Company or its
Affiliates (including without limitation any inquiry as to the qualification of
the Company to hold or receive any license or permit), and there is no basis for
any of the foregoing.  The Company has complied with all laws, rules,
regulations, and orders applicable to its business, operations, properties,
assets, products, and services.  The Company has all necessary permits,
licenses, and other authorizations required to conduct its business as
conducted, and has no reason to believe that the Company will not obtain the
same with respect to its business as proposed to be conducted, which, if not
obtained, would have, either individually or in the aggregate, a material
adverse effect on the Company.

     4.6  PROPRIETARY INFORMATION OF THIRD PARTIES. To the Company's knowledge,
no third party has claimed or has reason to claim that any person employed by or
affiliated with the Company or its Affiliates has (a) violated or may be
violating any of the terms or conditions of his or her employment,
noncompetition or nondisclosure agreement with such third party, (b) disclosed
or may be disclosing or utilized or may be utilizing any trade secret or
proprietary information or documentation of such third party, or (c) interfered
or may be interfering in the employment relationship between such third party
and any of its present or former employees.

     4.7  TITLE TO PROPERTIES.  The Company has good and marketable title to its
properties and assets reflected on the March 31 Balance Sheet or acquired by it
since the date of the March 31 Balance Sheet (other than properties and assets
disposed of in the ordinary course of business since the date of the March 31
Balance Sheet), and all such properties and assets are free and clear of all
Liens, except for liens for current taxes not yet due and payable and minor


                                        8


<PAGE>


imperfections of title, if any, not material in nature or amount and not
materially detracting from the value or impairing the use of the property
subject thereto or impairing the operations or proposed operations of the
Company.

     4.8  LEASEHOLD INTERESTS.  Each material lease or agreement to which the
Company is a party under which it is a lessee of any property, real or personal,
is a valid and existing agreement without any default of the Company thereunder
and, to the Company's knowledge, without any default thereunder of any other
party thereto.  No event has occurred and is continuing that, with due notice or
lapse of time or both, would constitute a default or event of default by the
Company under any such material lease or agreement or, to the Company's
knowledge, by any other party thereto.

     4.9  TAXES.  The Company has filed all tax returns, federal, state, county,
and local, required to be filed by it, and the Company has paid all taxes shown
to be due by such returns as well as all other taxes, assessments, and
governmental charges that have become due or payable, including without
limitation all taxes that the Company is obligated to withhold from amounts
owing to employees, creditors, and third parties.  All such taxes with respect
to which the Company has become obligated pursuant to elections made by the
Company in accordance with generally accepted practice have been paid and
adequate reserves have been established for all taxes accrued but not yet
payable.  The federal income tax returns of the Company have never been audited
by the Internal Revenue Service.  No deficiency assessment with respect to or
proposed adjustment of the Company's federal, state, county or local taxes is
pending or, to the Company's knowledge, threatened.

     4.10 NO DEFAULTS.  The Company and, to the Company's knowledge, each other
party thereto have in all material respects performed all the obligations
required to be performed by them to date, have received no notice of default and
are not in default (with due notice or lapse of time or both) under any lease,
agreement or contract now in effect to which the Company is a party or by which
it or its property may be bound.  The Company has no present expectation or
intention of not fully performing all its obligations under each such lease,
contract or other agreement, and the Company has no knowledge of any breach or
anticipated breach by the other party to any contract or commitment to which the
Company is a party.  The Company is in full compliance with all of the terms and
provisions of its Certificate of Incorporation and Bylaws, as amended.

     4.11 PATENTS, TRADEMARKS, ETC.  To the Company's knowledge, the Company
owns or possesses licenses or other rights to use all Intellectual Property
necessary or desirable to the conduct of its business as conducted and as
proposed to be conducted, and no claim is pending or threatened to the effect
that the operations of the Company infringe upon or conflict with the asserted
rights of any other person under any Intellectual Property, and there is no
basis for any such claim.  No claim is pending or threatened to the effect that
any such Intellectual Property owned or licensed by the Company, or which the
Company otherwise has the right to use, is invalid or unenforceable by the
Company, and there is no basis for any such claim (whether or not pending or
threatened).  To the Company's knowledge, all technical information developed by
and belonging to the Company that has not been patented has been kept
confidential.

                                        9


<PAGE>



     4.12 BROKERS.  The Company has no contract, arrangement or understanding
with any broker, finder or similar agent with respect to the transactions
contemplated by this Agreement.

     4.13 TRANSACTIONS WITH AFFILIATES.  No director, officer, employee or
stockholder of the Company, or member of the family of any such person, or any
corporation, partnership, trust or other entity in which any such person, or any
member of the family of any such person, has a substantial interest or is an
officer, director, trustee, partner or holder of more than 5% of the outstanding
capital stock thereof, is a party to any transaction with the Company, including
any contract, agreement or other arrangement providing for the employment of,
furnishing of services by, rental of real or personal property from or otherwise
requiring payments to any such person or firm.

     4.14 DISCLOSURE.  Neither this Agreement, nor any other statements,
documents, certificates or other items prepared or supplied by the Company with
respect to the transactions contemplated hereby contains an untrue statement of
a material fact or omits a material fact necessary to make the statements
contained therein not misleading.  There is no fact that the Company has not
disclosed to Medtronic and its counsel in writing and of which the Company is
aware that materially and adversely affects or could materially and adversely
affect the business, prospects, financial condition, operations, property or
affairs of the Company.


                                     ARTICLE 5
                    REPRESENTATIONS AND WARRANTIES OF MEDTRONIC

     Medtronic represents and warrants to the Company as follows:

     5.1  PURCHASE OF SHARES.  Medtronic is an "accredited investor" within the
meaning of Rule 501 under the Securities Act and was not organized for the
specific purpose of acquiring the Purchased Shares.  Medtronic has sufficient
knowledge and experience in investing in companies similar to the Company in
terms of the Company's stage of development so as to be able to evaluate the
risks and merits of Medtronic's investment in the Company, and Medtronic is able
financially to bear the risks thereof.  Medtronic has had an opportunity to
discuss the Company's business, management, and financial affairs with the
Company's management.  The Purchased Shares are being acquired for Medtronic's
own account for the purpose of investment and not with a view to or for sale in
connection with any distribution thereof.  Medtronic understands that (i) the
Purchased Shares have not been registered under the Securities Act by reason of
their issuance in a transaction exempt from the registration requirements of the
Securities Act pursuant to Section 4(2) thereof or Rule 505 or 506 promulgated
under the Securities Act, (ii) the Purchased Shares must be held indefinitely
unless a subsequent disposition thereof is registered under the Securities Act
or is exempt from such registration, (iii) the Purchased Shares will bear a
legend to such effect, and (iv) the Company will make a notation on its transfer
books to such effect.

     5.2  CORPORATE AUTHORITY.  The execution, delivery, and performance by
Medtronic of this Agreement and the transactions contemplated hereby has been
duly and validly authorized and approved by all requisite corporate action on
the part of Medtronic, and the execution and

                                        10


<PAGE>


the delivery of this Agreement and consummation of the transactions
contemplated hereby and compliance with and fulfillment of the terms and
provisions hereof will not (i) conflict with or result in a breach of the
terms, conditions or provisions of or constitute a default under the Articles
of Incorporation or Bylaws of Medtronic, or (ii) require any affirmative
approval, consent, authorization or other order or action of any court,
governmental authority, regulatory body, creditor or any other person.
Medtronic has all requisite power and authority to do and perform all acts
and things required to be done by it under this Agreement and the agreements
contemplated hereby.  This Agreement constitutes the valid and binding
obligation of Medtronic enforceable in accordance with its terms except as
may be limited by laws affecting creditors' rights generally or by judicial
limitations on the right to specific performance.

                                     ARTICLE 6
                     CONDITIONS TO THE OBLIGATIONS OF MEDTRONIC

     The obligations of Medtronic to purchase and pay for the Purchased Shares
pursuant to Section 2.1 are, at its option, subject to the satisfaction on or
before the Closing Date of the conditions set forth in Sections 6.1 through 6.8
below, inclusive.  References in this Article 6 to the "Closing Date" shall mean
and refer to the date set forth in Section 2.4, unless the parties agree to
consummate the transactions contemplated by this Agreement as of a date other
than the date set forth therein.

     6.1  REPRESENTATIONS AND WARRANTIES TRUE AND CORRECT.  The representations
and warranties of the Company contained in Article 4 shall be true, complete,
and correct on and as of the Closing Date with the same effect as though such
representations and warranties had been made on and as of such date, and the
Chairman of the Board and the President of the Company shall have certified to
such effect to Medtronic in writing.

     6.2  PERFORMANCE.  The Company shall have performed and complied with all
agreements contained herein required to be performed or complied with by it
prior to or at the Closing Date, and the Chairman of the Board and the President
of the Company shall have certified to Medtronic in writing to such effect and
to the further effect that all of the conditions set forth in Section 6.1
through 6.8, inclusive, have been satisfied.

     6.3  ALL PROCEEDINGS TO BE SATISFACTORY.  All corporate and other
proceedings to be taken by the Company in connection with the transactions
contemplated hereby and all documents incident thereto shall be satisfactory in
form and substance to Medtronic and its counsel, and Medtronic and its counsel
shall have received all such counterpart originals or certified or other copies
of such documents as they reasonably may request.

     6.4  SUPPORTING DOCUMENTS.  Medtronic and its counsel shall have received
copies of the following documents:

          (a)  a certificate of the Secretary of State of the State of Delaware
     dated as of a date within five days prior to the Closing Date as to the
     good standing of the Company and the payment of all excise taxes by the
     Company and listing all documents of the

                                        11


<PAGE>


     Company on file with said Secretary of State, and evidence satisfactory
     to Medtronic of the filing of the Certificate of Designation described in
     Section 2.1;

          (b)  a certificate of the Secretary of the Company dated as of the
     Closing Date certifying: (i) that the Company's Certificate of
     Incorporation and Bylaws have not been amended since the date of the copies
     thereof previously delivered to Medtronic; (ii) that attached thereto is a
     true and complete copy of all resolutions adopted by the Board of Directors
     of the Company authorizing the execution, delivery, and performance of this
     Agreement and the issuance, sale, and delivery of the Purchased Shares, and
     that all such resolutions are in full force and effect and are all the
     resolutions adopted in connection with the transactions contemplated by
     this Agreement; and (iii) to the incumbency and specimen signature of each
     officer of the Company executing this Agreement, the stock certificates
     representing the Purchased Shares, and any certificate or instrument
     furnished pursuant hereto, and a certification by another officer of the
     Company as to the
     incumbency and signature of the officer signing the certificate referred to
     in this paragraph (b); and

          (c)  such additional supporting documents and other information with
     respect to the operations and affairs of the Company as Medtronic or its
     counsel reasonably may request.

     6.5  REQUIRED CONSENTS.  The Company shall have obtained the written
consent or approval of each person whose consent or approval Medtronic
reasonably believes is required in connection with this Agreement.

     6.6  LITIGATION AFFECTING CLOSING.  No suit, action or other proceeding
shall be pending or threatened by any third party or by or before any court or
governmental agency seeking to restrain or prohibit or to obtain damages or
other relief in connection with this Agreement, or the consummation of the
transactions contemplated hereby or thereby, and no investigation that might
result in any such suit, action or other proceeding shall be pending or
threatened.

     6.7  NO MATERIAL ADVERSE CHANGES.  Since the date hereof, no events shall
have occurred or circumstances arisen that are reasonably expected to have or
result in a material adverse effect upon the Company or its business or
prospects.  The Company shall fully cooperate to enable Medtronic to determine
that this condition has been satisfied.

     6.8  REGISTRATION RIGHTS AGREEMENT.  The Company shall have executed and
delivered to Medtronic the Registration Rights Agreement.

                                        12


<PAGE>

                                     ARTICLE 7
                   COVENANTS OF THE COMPANY AND THE SHAREHOLDERS

     So long as Medtronic is the legal or beneficial owner of at [***] of the
issued and outstanding shares of  Common Stock of the Company, on an
as-converted basis:

     7.1  FINANCIAL STATEMENTS, REPORTS, ETC.  The Company shall furnish to
Medtronic:

          (a)  within 120 days after the end of each fiscal year of the Company,
     a balance sheet of the Company as of the end of such fiscal year and the
     related consolidated statements of income, stockholders' equity, and cash
     flows for the fiscal year then ended, prepared in accordance with generally
     accepted accounting principles and certified by a firm of independent
     public accountants selected by the Board of Directors of the Company;

          (b)  within 30 days after the end of each month, an unaudited balance
     sheet of the Company and the related statement of income, prepared on a
     basis consistent with the Company's past practice and in accordance with
     its books and records;

          (c)  within 30 days prior to the start of each fiscal year, any
     Company-wide forecasts or budgets prepared by the Company in respect of
     such fiscal year, and forecasts or budgets [***];

          (d)  promptly after the commencement thereof, notice of all actions,
     suits, claims, proceedings, investigations, and inquiries that could
     materially adversely affect the Company;

          (e)  promptly upon sending, making available or filing the same, all
     press releases, reports, and financial statements that the Company sends or
     makes available to its stockholders or directors or files with the SEC, the
     NASD, or any national securities exchange; and

          (f)  promptly, from time to time, such other information regarding the
     Company's overall financial condition [***]as Medtronic reasonably may
     request.

     7.2  INSPECTION, CONSULTATION, AND ADVICE.  The Company shall permit and
cause any Affiliates of the Company to permit Medtronic and such persons as it
may designate, at Medtronic's expense, to visit and inspect any of the
properties of the Company and its Affiliates, examine their books and take
copies and extracts therefrom, discuss [***] the finances of the Company and its
Affiliates with their officers, employees, and public accountants (and the
Company hereby authorizes said accountants to discuss with Medtronic and such
designees such information), and consult with and advise the management of the
Company and its Affiliates as to the Company's finances and [***], all at
reasonable times and upon reasonable notice.  All such information shall be
subject to Section 9.2 hereof.

*  Confidential portions of this document indicated by [***] have been omitted
and filed separately with the Commission.

                                        13


<PAGE>

     7.3  TRANSACTIONS WITH AFFILIATES.  Except for transactions contemplated by
this Agreement or as otherwise approved by the Board of Directors, neither the
Company nor any of its subsidiaries shall enter into any transaction with any
director, officer, employee or holder of more than 5% of the outstanding capital
stock of any class or series of capital stock of the Company or any of its
subsidiaries, member of the family of any such person, or any corporation,
partnership, trust or other entity in which any such person, or member of the
family of any such person, is a director, officer, trustee, partner or holder of
more than 5% of the outstanding capital stock thereof, except for transactions
on customary terms related to such person's employment.

     7.4  BOARD MEETINGS.  The Company shall use its best efforts to ensure that
meetings of its Board of Directors are held at least four times each year and at
least once each quarter.

     7.5  MEDTRONIC BOARD OBSERVER.  Medtronic shall have the right to designate
an observer to the Company's Board.  Medtronic's designee shall receive all
notices, documents, and other information in the same time and manner as such
information is supplied to members of the Board.  All such information shall be
subject to Section 9.2 hereof.  The Company shall make reasonable efforts to
permit Medtronic's designee to participate or observe Board meetings by
telephone if such designee is unable to attend in person.  The parties agree
that Medtronic's observer to the Company's Board shall be present solely for the
purpose of observation and shall have no power to exert "control" on behalf of
Medtronic as that term is defined in Rule 405 under the Securities Act.

     7.6  PROPRIETARY INFORMATION AND EMPLOYEE INVENTIONS AGREEMENTS.  The
Company shall use its best efforts to obtain confidentiality and assignment of
inventions agreements from all officers, key employees, and other employees,
consultants or independent contractors who will have access to confidential
information of the Company.

     7.7  COMPLIANCE WITH LAWS.  The Company shall comply, and cause each
Affiliate to comply, with all applicable laws, rules, regulations, and orders,
noncompliance with which could materially adversely affect the Company's
business or condition, financial or otherwise.

     7.8  KEEPING OF RECORDS AND BOOKS OF ACCOUNT. The Company shall keep, and
cause each Affiliate to keep, adequate records and books of account, in which
complete entries will be made in accordance with generally accepted accounting
principles consistently applied, reflecting all financial transactions of the
Company and such subsidiary, and in which, for each fiscal year, all proper
reserves for depreciation, depletion, obsolescence, amortization, taxes, bad
debts, and other purposes in connection with its business shall be made.

     7.9  USE OF MEDTRONIC NAME.  Except for any joint public announcement
described in Section 9.8 and the information contained therein, the Company
shall not, except with the written consent of Medtronic, publicly use
Medtronic's name or disclose Medtronic's relationship with the Company.


                                        14


<PAGE>


                                     ARTICLE 8
                                  INDEMNIFICATION

     8.1  INDEMNIFICATION OF MEDTRONIC.  The Company shall indemnify, defend,
and hold harmless Medtronic and each of its subsidiaries, officers, directors,
shareholders, employees, agents, and affiliates (Medtronic and such other
indemnities are referred to in this Article 8 as "Medtronic") from and against
and in respect of any and all demands, claims, actions or causes of action,
assessments, losses, damages, liabilities, interest and penalties, costs, and
expenses (including, without limitation, reasonable legal fees and disbursements
incurred in connection therewith and in seeking indemnification therefor, and
any amounts or expenses required to be paid or incurred in connection with any
action, suit, proceeding, claim, appeal, demand, assessment or judgment)
("Indemnifiable Losses") resulting from, arising out of, or imposed upon or
incurred by any person to be indemnified hereunder by reason of any breach of
any representation, warranty, covenant or agreement of the Company contained in
this Agreement or any agreement, certificate or document executed and delivered
by the Company pursuant hereto or in connection with any of the transactions
contemplated by this Agreement.

     8.2  INDEMNIFICATION OF THE COMPANY.  Medtronic shall indemnify, defend,
and hold harmless the Company and each of its subsidiaries, officers, directors,
shareholders, employees, agents, and affiliates (the Company and such other
indemnities referred to in this Article 8 as "the Company") from and against and
in respect of any and all demands, claims, actions or causes of action,
assessments, losses, damages, liabilities, interest and penalties, costs, and
expenses (including, without limitation, reasonable legal fees and disbursements
incurred in connection therewith and in seeking indemnification therefor, and
any amounts or expenses required to be paid or incurred in connection with any
action, suit, proceeding, claim, appeal, demand, assessment or judgment)
resulting from, arising out of, or imposed upon or incurred by any person to be
indemnified hereunder by reason of any breach of any representation, warranty,
covenant or agreement of Medtronic contained in this Agreement or any agreement,
certificate or document executed and delivered by Medtronic pursuant hereto or
in connection with the transactions contemplated by this Agreement.

     8.3  THIRD-PARTY CLAIMS.  If a claim by a third party is made against an
indemnified party and if the indemnified party intends to seek indemnity with
respect thereto under this Article 8, such indemnified party shall promptly
notify the indemnifying party of such claim; provided, however, that failure to
give timely notice shall not affect the rights of the indemnified party so long
as the failure to give timely notice does not adversely affect the indemnifying
party's ability to defend such claim against a third party.  The indemnifying
party or parties shall be entitled to settle or assume the defense of such
claim, including the employment of counsel reasonably satisfactory to the
indemnified party.  If the indemnifying party or parties elect(s) to settle or
defend such claim, the indemnifying party or parties shall notify the
indemnified party within 30 days (but in no event less than 20 days before any
pleading, filing or response on behalf of the indemnified party is due) of the
indemnifying party's or parties' intent to do so.  If the indemnifying party or
parties elect(s) not to settle or defend such claim or fail(s) to notify the
indemnified party of the election within 30 days  (or such shorter period
provided above) after receipt of the indemnified party's notice of a claim of
indemnity hereunder, the indemnified party shall have the right to contest,
settle or compromise the claim without prejudice to any


                                        15

<PAGE>

rights to indemnification hereunder.  Regardless of which party is
controlling the settlement of defense of any claim, (a) both the indemnified
party and indemnifying party or parties shall act in good faith, (b) the
indemnifying party or parties shall not thereby permit to exist any lien,
encumbrance or other adverse charge upon any asset of any indemnified party
or of its subsidiaries, (c) the indemnifying party or parties shall permit
the indemnified party to participate in such settlement or defense through
counsel chosen by the indemnified party, with all fees, costs, and expenses
of such counsel borne by the indemnifying party or parties, (d) no entry of
judgment or settlement of a claim may be agreed to without the written
consent of the indemnified party, and (e) the indemnifying party or parties
shall promptly reimburse the indemnified party for the full amount of such
claim and the related expenses as incurred by the indemnified party pursuant
to this Article 8.  So long as the indemnifying party or parties is (are)
reasonably contesting any such third party claim in good faith and the
foregoing clause (b) is being complied with, the indemnified party shall not
pay or settle any such claim.  The controlling party shall upon request
deliver, or cause to be delivered, to the other party copies of all
correspondence, pleadings, motions, briefs, appeals or other written
statements relating to or submitted in connection with the settlement or
defense of any such claim, and timely notices of any hearing or other court
proceeding relating to such claim.

     8.4  COOPERATION AS TO INDEMNIFIED LIABILITY.  Each party hereto shall
cooperate fully with the other parties with respect to access to books, records,
or other documentation within such party's control, if deemed reasonably
necessary or appropriate by any party in the defense of any claim that may give
rise to indemnification hereunder.


                                     ARTICLE 9
                                  OTHER PROVISIONS

     9.1  PURCHASE OF PURCHASED SHARES BY MEDTRONIC AFFILIATE.  Notwithstanding
any other provisions of this Agreement, Medtronic shall have the right at its
option to designate and permit an affiliate of Medtronic to acquire and hold the
Purchased Shares pursuant to this Agreement.  In the event that Medtronic elects
to do so, references in this Agreement to "Medtronic" shall, in the context of
the acquisition and ownership of the Purchased Shares, mean and refer to such
affiliate.

     9.2  NONDISCLOSURE.  Each party agrees not to disclose or use (except as
permitted or required for performance by the party receiving such Confidential
Information of its rights or duties hereunder) any Confidential Information of
the other party obtained during the during the term of this Agreement until, as
to any such Confidential Information, the date as of which such Confidential
Information has been in the possession of the receiving party, as a result of
disclosure under this Agreement, for a period of seven years.  Each party
further agrees to take appropriate measures to prevent any such prohibited
disclosure by its present and future employees, officers, agents, subsidiaries,
or consultants during such period.

     9.3  FURTHER ASSURANCES.  At such time and from time to time on and after
the date hereof upon request by Medtronic, the Company will execute,
acknowledge, and deliver, or will cause to be done, executed, acknowledged, and
delivered, all such further acts, certificates, and


                                        16


<PAGE>


assurances that may be required for the better conveying, transferring,
assigning, delivering, assuring, and confirming to Medtronic, or to its
respective successors and assigns, all of the Purchased Shares or to
otherwise carry out the purposes of this Agreement.

     9.4  ENTIRE AGREEMENT.  The Schedules and Exhibits to this Agreement shall
be construed as an integral part of this Agreement to the same extent as if they
had been set forth verbatim herein.  This Agreement and the Registration Rights
Agreement, and the Schedules and Exhibits hereto and thereto, constitute the
entire agreement between the parties hereto with respect to the subject matter
hereof and supersede all prior agreements whether written or oral relating
hereto, except for that certain Agreement for Mutual Exchange of Confidential
Information dated December 11, 1997, between the Company and Medtronic, which
shall remain in effect.

     9.5  SURVIVAL.  The representations, warranties, covenants, and agreements
contained herein shall survive the purchase of the Purchased Shares and remain
in full force and effect, except that the representations and warranties
contained in Articles 4 and 5 hereof shall expire on the date that is two years
after the date hereof.  No independent investigation of the Company by
Medtronic, its counsel, or any of its agents or employees shall in any way limit
or restrict the scope of the representations and warranties made by the Company
in this Agreement.

     9.6  WAIVER, DISCHARGE, AMENDMENT, ETC.  The failure of either party to
enforce at any time any of the provisions of this Agreement shall in no way be
construed to be a waiver of any such provision, nor in any way to affect the
validity of this Agreement or any part of it or the right of either party after
any such failure to enforce each and every such provision.  No waiver of any
breach of this Agreement shall be held to be a waiver of any other or subsequent
breach.  This Agreement may be amended only by the Company and Medtronic, by
mutual action approved by their respective Boards of Directors or their
respective officers authorized by such Board of Directors.  Any amendment to
this Agreement shall be in writing and signed by the Company and Medtronic.

     9.7  NOTICES.  All notices or other communications to a party required or
permitted hereunder shall be in writing and shall be delivered personally or by
telecopy (receipt confirmed) to such party (or, in the case of an entity, to an
executive officer of such party) or shall be sent by a reputable express
delivery service or by certified mail, postage prepaid with return receipt
requested, addressed as follows:

if to Medtronic to:

     Medtronic, Inc.
     Corporate Center
     7000 Central Avenue N.E.
     Minneapolis, Minnesota 55432
     FAX (612) 572-5404

     with separate copies thereof addressed to:
          Attention:     General Counsel


                                        17


<PAGE>


     and
          Attention:     Vice President, Corporate Development
                         and Associate General Counsel

if to the Company to:

     BioNebraska, Inc.
     3820 NW 46th Street
     Lincoln, Nebraska  68524
     FAX (402) 470-2345
     Attention:      Thomas R. Coolidge
                     Chairman of the Board and CEO

     Any party may change the above-specified recipient and/or mailing address
by notice to all other parties given in the manner herein prescribed.  All
notices shall be deemed given on the day when actually delivered as provided
above (if delivered personally or by telecopy) or on the day shown on the return
receipt (if delivered by mail or delivery service).

     9.8  PUBLIC ANNOUNCEMENT.  In the event any party proposes to issue any
press release or public announcement concerning any provisions of this Agreement
or the transactions contemplated hereby, such party shall so advise the other
parties hereto, and the parties shall thereafter use their best efforts to cause
a mutually agreeable release or announcement to be issued.  Neither party will
publicly disclose or divulge any provisions of this Agreement or the
transactions contemplated hereby without the other parties' written consent,
except as may be required by applicable law or stock exchange regulation, and
except for communications to employees.

     9.9  EXPENSES.  The Company and Medtronic shall each pay their own expenses
incident to this Agreement and the preparation for, and consummation of, the
transactions provided for herein.

     9.10 GOVERNING LAW.  This Agreement shall be governed by, and interpreted
and construed in accordance with, the laws of the State of Minnesota, without
giving effect to principles of conflict or choice of laws.

     9.11 TITLES AND HEADINGS; CONSTRUCTION.  The titles and headings to the
Articles and Sections herein are inserted for the convenience of reference only
and are not intended to be a part of or to affect the meaning or interpretation
of this Agreement.  This Agreement shall be construed without regard to any
presumption or other rule requiring construction hereof against the party
causing this Agreement to be drafted.

     9.12 BENEFIT.  Nothing in this Agreement, expressed or implied, is intended
to confer on any person other than the parties to this Agreement, or their
respective successors or assigns, any rights, remedies, obligations or
liabilities under or by reason of this Agreement.


                                        18


<PAGE>


     9.13 COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed as original and all of which
together shall constitute one instrument, and may be delivered in person or by
facsimile transmission.

     9.14 SEVERABILITY.  If any provision of this Agreement is held invalid by a
court of competent jurisdiction, the remaining provisions shall nonetheless be
enforceable according to their terms.  Further, if any provision is held to be
overbroad as written, such provision shall be deemed amended to narrow its
application to the extent necessary to make the provision enforceable according
to applicable law and shall be enforced as amended.

     9.15 PARTIES IN INTEREST.  All representations, covenants, and agreements
contained in this Agreement by or on behalf of any of the parties hereto shall
bind and inure to the benefit of the respective successors and assigns of the
parties hereto, whether so expressed or not.  Without limiting the generality of
the foregoing, all representations, covenants, and agreements benefiting
Medtronic shall inure to the benefit of any and all subsequent holders from time
to time of the Purchased Shares.



                                        19


<PAGE>


     IN WITNESS WHEREOF, each of the parties has caused this Investment
Agreement to be executed in the manner appropriate for each, and to be dated as
of the date first above written.

                              BIONEBRASKA, INC.


                              By:       /s/ Thomas R. Coolidge
                                 -------------------------------------------
                              Name:     Thomas R. Coolidge
                              Title:    Chairman of the Board and Chief
                                        Executive Officer


                              MEDTRONIC, INC.


                              By:  /s/ Michael D. Ellwein
                                 -------------------------------------------
                                   Its:  Vice President
                                       -------------------------------------


                                        20