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                                                                   EXHIBIT 10.28
 
                               PLEDGE AGREEMENT
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                               February 21, 1997


PLEDGOR:       Peter E. Oettinger ("Dr. Oettinger")
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COMPANY:       Photoelectron Corporation. ("Company")
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Relating to the Stock of the Company.

                                  INTRODUCTION
                                  ------------

    This Pledge Agreement is being made to secure the Secured Promissory Note of
Dr. Oettinger dated as of February 21, 1997 containing the promise to pay to the
Company the sum of $ 80,211.26, (referred to herein as "the Note").
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                              TERMS AND CONDITIONS
                              --------------------

1.   Certain Definitions.  As used in this Pledge Agreement, the following terms
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shall nave the following respective meanings:

     Pledged Shares:  25,000 shares of the Common Stock, $.01 par value, of the
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Company registered in the name of Dr. Oettinger (the "Shares").

     Events of Default: (a) The failure of Dr. Oettinger to make any payment of
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principal or interest on the Note as provided therein, or (b) the filing by Dr.
Oettinger of a petition under any bankruptcy or insolvency law or for the
appointment of a receiver or making a general assignment for the benefit of
creditors, or (c) the filing against Dr. Oettinger of an involuntary petition
under any bankruptcy or insolvency law and such petition is consented to by Dr.
Oettinger or is not dismissed or stayed within 60 days after the filing of such
petition

2.   Pledge of Stock.  Dr. Oettinger hereby pledges and assigns to the Company
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certificate(s) representing the Shares, which certificates, accompanied by an
assignment in blank duly executed by Dr. Oettinger, are herewith delivered to
the Company.  Dr. Oettinger represents that he is the owner of the Shares, free
and clear of liens, encumbrances or charge that might affect title to the
Shares, and that he has full power to transfer the Shares pursuant to this
Pledge Agreement.

3.  Security for Secured Obligations.  This Pledge Agreement is made by Dr.
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Oettinger for the benefit of the Company to secure the punctual payment and
performance of the Note.
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      4.  Remedies in Case of an Event of Default, etc,
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          4.1  In case an Event of Default shall have occurred and be
continuing, the Company shall be entitled, without limitation:

          (a) to exercise all voting rights in respect of the Shares and to give
all consents, waivers and ratifications in respect thereof and otherwise to act
with, respect thereto as though it were the outright owner thereof (Dr.
Oettinger Hereby irrevocably constitutes and appoints the Company and each
officer, director or designee of the Company, the proxy and attorney-in-fact of
Dr. Oettinger with full power of substitution, to do so);

          (b) to receive all amounts in respect of any of the Shares otherwise
payable to Dr. Oettinger;

          (c) to sell, assign and deliver all or, 1rom time to time, any of the
Shares or any interest in any part thereof, at any private sale or at public
auction, with or without demand or advertisement (but with not less than five
(5) days notice to Dr. Oettinger) of the time or place of sale or adjournment
thereof, or otherwise, for cash, on credit or for other property, for immediate
or future delivery, and for such price or prices and on such terms as the
Company in its uncontrolled discretion may determine.

     To the extent permitted by applicable law, Dr. Oettinger hereby waives and
releases all rights with respect to demand of performance, advertisement or
notice of intention to sell or of the time or place of sale or adjournment
thereof and any and all right or equity of redemption whether before or after
sale hereunder.  'The Company and any holder of the Note may bid for and
purchase the whole or any part of the Shares so sold, and shall upon any such
purchase, acquire good title to the Shares so purchased, 1ree of the lien of
this Pledge Agreement and free of any such right or equity of redemption.

          4.2  If and so long as an Event of Default shall have occurred and be
continuing, the Company shall apply all monies collected or received by it
hereunder in respect of the Shares as follows:

          First:  to the payment of all costs (including attorneys' fees)
incurred by the Company or any holder of the Note in connection with the
collection thereof (including, without limitation, stamp or other taxes in
respect of the transfer of any of tile Shares) or in connection with the
exercise or enforcement of the rights, powers or remedies hereunder (including
the expenses and disbursements of the Company, any Holder of the Note, and their
respective counsel);

          Second:  to the payment of all costs (including attorneys' fees)
incurred by the Company (and not reimbursed by Dr. Oettinger) reasonably
attributable to any registration or qualification of the Shares or compliance
with respect thereto under any

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federal or state securities laws, provided that the Company shall have no
obligation to incur any such costs unless the Company shall agree to do so in
its sole discretion;

          Third:   toward the payment of the whole amount then due and payable
on the Note, first to interest, then to principal; and

          Fourth:  any balance (if the Note shall have been paid in full) shall
be paid to Dr. Oettinger or as a court of competent jurisdiction may direct.


          4.3  Neither failure nor delay on the part of the Company or any
holder of the Note to exercise any right, power or remedy provided for herein or
by statute or at law or in equity shall operate as a waiver thereof, nor shall
any single or partial exercise of any such right, power or remedy preclude any
other further exercise thereof' or the exercise of any other right, power or
remedy.


     5.  Manner of Sale.  Dr. Oettinger recognizes that registration of the
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Shares may be impractical because of the expenses or delays involved in the
registration process and that in the absence of such registration the Company
may be unable to effect a public sale of all or any part of the Shares, but may
be compelled to resort to one or more private sales to a restricted group of
purchasers who will be obliged to agree, among other things, to acquire such
Shares for their own accounts, for investment and not with a view to [lie
distribution or resale thereof.  Dr. Oettinger understands that private sales so
made may be at prices and on other terms less favorable to the seller than if
the Shares were sold at public sale.  Dr. Oettinger agrees that the Company has
no obligation to delay sale of' any Such Shares for the period of time necessary
to permit such Shares to be registered for public sale under the Securities Act
of 1933 or any applicable Blue Sky or other state Securities laws, or to incur
any expenses necessary to eflect such registration.  Dr. Oettinger agrees that
no such private sales shall be deemed to have been made ill a commercially
unreasonable manner by virtue of any less favorable terms resulting from the
private nature of such sales.


     6.  Statement as to Default.  Dr. Oettinger acknowledges to and agrees with
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any purchaser of the Shares at a sale pursuant to this Agreement that any
written statement by the Company or any person representing the Company
asserting the occurrence of an Event of Default as the authorization for the
exercise of the rights of tile Company hereunder shall be conclusively presumed
to be true with respect to such purchaser without, however, waiving any rights
which such Dr. Oettinger may have against the Company or its representative.


     7.  Obligation Not Affected.  The obligations of Dr. Oettinger under this
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Pledge Agreement are absolute and unconditional, shall remain in full force and
effect without regard to, and shall not be released, discharged or in any way
impaired or affected by: (a) any assignment or transfer of the Note; (b) any
exercise or non-exercise by any holder of the Note or by the Company of any
right, power or remedy under or in respect of this Pledge Agreement or the Note,
or any assignment or transfer of any

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thereof, or any waiver of any such right, power or remedy; (c) any waiver,
consent, extension, indulgence or other action or inaction in respect to of this
Pledge Agreement or the Note; or (d) any bankruptcy, insolvency, reorganization,
arrangement, readjustment, composition, liquidation, or the like, of the
Company; whether or not Dr. Oettinger shall leave notice or knowledge of any of
the foregoing.

     8.  Termination.  Upon the earlier of (i) any discharge, cancellation,
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substitution, replacement, exchange, amendment or modification of the Note or
(ii) the acceptance by the Company of alternative security for the Note, this
Pledge Agreement shall terminate. The Company shall promptly assign, transfer,
deliver and release the Shares to Dr. Oettinger, and shall execute such
instruments and documents as may reasonably be requested by Dr. Oettinger to
effect same.

     9.  Transfer, etc.  Dr. Oettinger will not sell, assign, transfer or
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otherwise dispose of, grant any option with respect to, or pledge or otherwise
encumber (except pursuant to this Pledge Agreement) any of the Shares or any
interest therein.

     10.  Further Assistance.  Dr. Oettinger from time to time will execute and
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deliver all such instruments and take all such action as the Company or the
Holder of the Note at the time outstanding may request in order further to
effectuate the purposes of this Pledge Agreement and to carry out the terms
hereof.

     11.  Notices, etc.  All notices and other communications hereunder shall be
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in writing and shall be deemed adequately given if personally delivered or
mailed, certified mail, return receipt requested, to any party at the address
specified above for such party, or such other address as any such party may from
time to time designate for itself by notice given in writing to all other
parties hereto.

     12.  Miscellaneous.
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          12.1  This Pledge Agreement may be amended only by a writing signed
by, Dr. Oettinger and by the Company.  No waiver of any term of this Pledge
Agreement shall be effective unless in writing and signed by the party waiving
such term.

          12.2  This Pledge Agreement shall be binding upon and inure to the
benefit of and be enforceable by the respective heirs, successors and assigns of
the parties hereto, whether so expressed or not, and, in particular, shall inure
to the benefit of and be enforceable by any holder of the Note.

          12.3.  The headings in this Pledge Agreement are for purposes of
reference only and shall not limit or otherwise affect the meaning hereof.

          12.4 This Pledge Agreement shall be construed and enforced in
accordance with the laws of the Commonwealth of Massachusetts.



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         12.5  The provisions of this Pledge Agreement are severable and if
for any reason any provision of this Pledge Agreement is held to be void or
unenforceable by a court of competent jurisdiction, the same shall not affect
the remaining provisions hereof.



EXECUTED as a sealed instrument on the date first above written.



Pledgor:



                                    Company:

                                    PHOTOELECTRON CORPORATION


Peter E. Oettinger                  Peter M. Nomikos
                                    President and Chief Executive Officer