<PAGE>   1
EXHIBIT *(10.28)

                          TRADEMARK SECURITY AGREEMENT

      This Trademark Security Agreement ("Agreement") is made as of the 29th day
of October, 1999 by IMMUNOGENETICS, INC. ("Grantor"), a Delaware corporation
having a mailing address at Wheat Road and Lincoln Avenue, Buena, NJ 08310, and
delivered to FLEET CAPITAL CORPORATION, a Rhode Island corporation having a
mailing address at 200 Glastonbury Blvd., Glastonbury, CT 06033 ("Lender").


                                   BACKGROUND

      A. This Agreement is being executed contemporaneously with that certain
Loan and Security Agreement of even date herewith among Grantor, IGI, Inc.,
IGEN, Inc., and Blood Cells, Inc. (collectively, "Borrowers") and Lender (as it
may hereafter be supplemented, restated, amended, superseded or replaced from
time to time, the "Loan Agreement"), under which, inter alia, Borrower is
granting Lender a lien on and security interest in certain assets of Borrower
associated with or relating to products leased or sold or services provided
under Borrower's trademarks and the goodwill associated therewith as security
for the payment and performance of all the Obligations (as defined in the Loan
Agreement) of all the Borrowers under the Loan Agreement, and under which Lender
is entitled to foreclose or otherwise deal with such assets, trademarks, service
marks and tradenames under the terms and conditions set forth therein.
Capitalized terms not defined herein shall have the meanings given to such terms
in the Loan Agreement.

      B. Grantor has adopted, used and is using (or has filed applications for
the registration of) the trademarks, servicemarks and tradenames listed on
SCHEDULE "A" attached hereto and made part hereof (all such marks or names
hereinafter referred to as the "Trademarks").

      C. Pursuant to the Loan Agreement, Lender is acquiring a lien on, security
interest in, and license to use (which license is conditioned upon the
occurrence and continuance of an Event of Default) the Trademarks, together with
all the goodwill of Grantor associated therewith and represented thereby, as
security for all of the Obligations, and desires to have its security interest
in such Trademarks confirmed by a document identifying same and in such form
that it may be recorded in the United States Patent and Trademark Office.

      NOW THEREFORE, with the foregoing Background hereinafter deemed
incorporated by reference and made a part hereof, and in consideration of the
premises and mutual promises herein contained, the parties hereto, intending to
be legally bound hereby, covenant and agree as follows:

      1. In consideration of and pursuant to the terms of the Loan Documents,
and for other good, valuable and sufficient consideration, the receipt of which
is hereby acknowledged, and to secure the payment and performance of all the
Obligations of all Borrowers under the Loan Agreement, Grantor grants a lien and
security interest to Lender in all of its present and future right, title and
interest in and to the Trademarks, together with all the goodwill of Grantor
associated with and represented by the Trademarks, and the registration thereof
and the right (but not the obligation) to sue for past, present and future
infringements, and the proceeds thereof, including, without limitation, license
royalties and proceeds of infringement suits, (collectively the "Collateral").


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<PAGE>   2
      2. Grantor hereby covenants and agrees to maintain the Trademarks in full
force and effect and otherwise perform all of its obligations and undertakings
under this Agreement until all of the Obligations are indefeasibly paid and
satisfied in full and the Loan Agreement has been terminated.

      3. Grantor represents, warrants and covenants that:

            (a)   The Trademarks are subsisting and have not been adjudged
invalid or unenforceable;

            (b) Each of the Trademarks is registered (or in the process of
application for registration), and, to the best of Grantor's knowledge, is valid
and enforceable;

            (c) Grantor is the sole and exclusive owner of the entire and
unencumbered right, title and interest in and to each of the Trademarks, and
except for Liens permitted under Section 8.2.5 of the Loan Agreement, each of
the Trademarks is free and clear of any liens, claims, charges and encumbrances,
including, without limitation, pledges, assignments, options, and covenants by
Grantor not to sue third persons;

            (d) Grantor has the unqualified right, power and authority to enter
into this Agreement and perform its terms;

            (e) Grantor has complied with, and will continue for the duration of
this Agreement to comply with, the requirements set forth in 15 U.S.C.
Section 1051-1127 and any other applicable statutes, rules and regulations in
connection with its use of the Trademarks;

            (f) Grantor has used and will continue to use for the duration of
this Agreement consistent standards of quality in services or products leased or
sold under the Trademarks, and hereby grants to Lender and its employees and
agents the right (with no obligation of any kind upon Lender to do so) to visit
Grantor's affiliates, franchises or management locations and to inspect the use
of the Trademarks and quality control records relating thereto at reasonable
times during regular business hours to ensure Grantor's compliance with this
paragraph 3(f); and

            (g) Grantor has no notice of any suits or actions commenced or
threatened against it, or notice of claims asserted or threatened against it,
with reference to the Trademarks.

      4. Grantor further covenants that:

            (a) Until all of the Obligations have been indefeasibly paid and
satisfied in full and the Revolving Credit has been terminated, Grantor will not
enter into any agreement which is inconsistent with Grantor's obligations under
this Agreement or which restrict or impair Agent's right or priorities
hereunder.

            (b) If Grantor acquires rights to any new trademarks, the provisions
of this Agreement shall automatically apply thereto and such trademarks shall be
deemed part of the Trademarks. Grantor shall give Lender written notice promptly
upon its first use thereof along with an amended SCHEDULE "A".


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<PAGE>   3
      5. So long as this Agreement is in effect and so long as Grantor has not
received notice from Lender that an Event of Default has occurred and is
continuing under the Loan Agreement and that Lender has elected to exercise its
rights hereunder, Grantor shall continue to have the right to use the Trademarks
and Lender shall have no right to use the Trademarks or issue any exclusive or
non-exclusive license with respect thereto, or assign, pledge or otherwise
transfer title in the Trademarks to anyone else.

      6. Grantor agrees not to sell, grant any option, assign or further
encumber its rights and interest in the Trademarks without prior written consent
of Lender or as may be expressly permitted under the Loan Agreement.
Notwithstanding the foregoing, and providing that no Default or Event of Default
has occurred and is outstanding, Grantor shall be entitled to license any
Trademarks in exchange for fair market consideration in the exercise of its
reasonable business judgment.

      7. Following the occurrence and during the continuance of an Event of
Default under the Loan Agreement, Lender, as the holder of a security interest
under the Uniform Commercial Code, as now or hereafter in effect in the State
whose law governs the interpretation of the Loan Agreement, may take such action
permitted under the Loan Documents, hereunder or under any law, in its exclusive
discretion, to foreclose upon or otherwise exercise its rights against the
Trademarks covered hereby. For such purposes, Grantor authorizes and empowers
Lender, its successors and assigns, and any officer or agent of Lender as Lender
may select, in its exclusive discretion, as Grantor's true and lawful
attorney-in-fact, with the power to endorse Grantor's name on all applications,
assignments, documents, papers and instruments necessary for Lender to use the
Trademarks or to grant or issue any exclusive or non-exclusive license under the
Trademarks to anyone else, or necessary for Lender to assign, pledge, convey or
otherwise transfer title in or dispose of the Trademarks to anyone else
including, without limitation, the power to execute on Grantor's behalf a
trademark assignment in the form attached hereto as EXHIBIT I. Grantor hereby
ratifies all that such attorney shall lawfully do or cause to be done by virtue
hereof and in accordance with the terms hereof, except for the gross negligence
or willful misconduct of such attorney. This power of attorney shall be
irrevocable for the life of this Agreement, the Loan Documents, and until all
the Obligations are indefeasibly paid and satisfied in full and the Loan
Agreement is terminated.

      8. This Agreement shall not be modified without the written consent of the
parties hereto.

      9. All rights and remedies herein granted to Lender shall be in addition
to any rights and remedies granted under the Loan Documents and shall be
cumulative. In the event of an inconsistency between this Agreement and the Loan
Agreement, the language of the Loan Agreement shall control.

      10. Upon full and unconditional satisfaction of all of the Obligations and
termination of the Revolving Credit, Lender shall execute and deliver to Grantor
all documents reasonably necessary to terminate Lender's security interest in
the Trademarks.

      11. Any and all reasonable fees, costs and expenses, of whatever kind or
nature, including the reasonable attorneys' fees and legal expenses incurred by
Lender in connection with the preparation and execution of this Agreement and
all other documents relating hereto, the filing or recording of any documents
(including all taxes in connection therewith) in public offices, the payment or
discharge of any taxes, reasonable counsel fees, maintenance fees, encumbrances
or costs otherwise incurred in protecting, maintaining, preserving the
Trademarks, or in defending or prosecuting any actions or


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<PAGE>   4
proceedings arising out of or related to the Trademarks, or defending,
protecting or enforcing Lender's rights hereunder, in each case in accordance
with the terms of this Agreement, shall be borne and paid by Grantor on demand
by Lender and until so paid shall be added to the principal amount of the
Obligations and shall bear interest at the highest rate applicable to Revolving
Credit Loans from time to time under the Loan Agreement.

      12. Subject to any applicable terms of the Loan Agreement, Grantor shall
have the duty to prosecute diligently any trademark application with respect to
the Trademarks pending as of the date of this Agreement or thereafter to
preserve and maintain all rights in the Trademarks, and upon reasonable request
of Lender, Grantor shall make federal application on registrable but
unregistered trademarks belonging to Grantor. Any reasonable expenses incurred
in connection with such applications shall be borne by Grantor. Grantor shall
not abandon any Trademark without the prior written consent of the Lender, which
consent shall not unreasonably be withheld.

      13. Grantor shall have the right to bring suit in its own name to enforce
the Trademarks, in which event Lender may, if Grantor reasonably deems it
necessary, be joined as a nominal party to such suit if Lender shall have been
satisfied, in its sole discretion, that it is not thereby incurring any risk of
liability because of such joinder. Grantor shall promptly, upon demand,
reimburse and indemnify Lender for all damages, reasonable costs and expenses,
including attorneys' fees, incurred by Lender in the fulfillment of the
provisions of this paragraph.

      14. If an Event of Default is outstanding under the Loan Agreement, Lender
may, without any obligation to do so, complete any obligation of Grantor
hereunder, in Grantor's name or in Lender's name, but at Grantor's expense, and
Grantor hereby agrees to reimburse Lender in full for all reasonable costs and
expenses, including attorneys' fees, incurred by Lender in protecting, defending
and maintaining the Trademarks.

      15. No course of dealing between Grantor and Lender nor any failure to
exercise, nor any delay in exercising, on the part of Lender, any right, power
or privilege hereunder, shall operate as a waiver thereof, and all of Lender's
rights and remedies with respect to the Trademarks, whether established hereby
or by the Loan Documents, or by any other future agreements between Grantor and
Lender or by law, shall be cumulative and may be exercised singularly or
concurrently.

      16. The provisions of this Agreement are severable and the invalidity or
unenforceability of any provision herein shall not affect the remaining
provisions which shall continue unimpaired and in full force and effect.

      17. This Agreement shall inure to the benefit of and be binding upon the
respective successors and permitted assigns of the parties.

      18. This Agreement shall be governed by and construed in conformity with
the laws of the Commonwealth of Pennsylvania without regard to its otherwise
applicable principles of conflicts of laws.

      19. GRANTOR AND LENDER EACH WAIVE ANY AND ALL RIGHTS IT MAY HAVE TO A JURY
TRIAL IN CONNECTION WITH ANY LITIGATION, PROCEEDING OR COUNTERCLAIM ARISING WITH
RESPECT TO RIGHTS AND OBLIGATIONS OF THE PARTIES UNDER THIS AGREEMENT.


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                 [REMAINDER OF PAGE LEFT INTENTIONALLY BLANK]


                                      -5-
<PAGE>   6
      IN WITNESS WHEREOF, the parties hereto have executed this Trademark
Security Agreement the day and year first above written.


                              IMMUNOGENETICS, INC.



                              By:  /s/ Robert E. McDaniel
                                   ___________________________________________


                              Name:  Robert E. McDaniel
                                     ______________________________________

                              Title: Secretary
                                     ______________________________________


                                      S-1
<PAGE>   7
                            CORPORATE ACKNOWLEDGMENT


UNITED STATES OF AMERICA      :
STATE OF                      : SS
COUNTY OF                     :



      On this 29th of October, 1999, before me personally appeared
___________________, to me known and being duly sworn, deposes and says that
s/he is ________________________of IMMUNOGENETICS INC.; that s/he signed the
Agreement thereto as such officer pursuant to the authority vested in him by
law; that the within Agreement is the voluntary act of such corporation; and
s/he desires the same to be recorded as such.






                                          ____________________________________
                                          Notary Public

                                          My Commission Expires:


                                      -7-
<PAGE>   8
                                    Exhibit I

                              TRADEMARK ASSIGNMENT


      WHEREAS, IMMUNOGENETICS, INC. ("Grantor") is the registered owner of the
United States trademarks, tradenames and registrations listed on SCHEDULE "A"
attached hereto and made a part hereof (the "Trademarks"), which are registered
in the United States Patent and Trademark Office; and

      WHEREAS, _____________________________ ("Grantee"), having a place of
business at ___________________________________________________, is desirous
of acquiring said Trademarks;

      NOW THEREFORE, for good and valuable consideration, receipt of which is
hereby acknowledged, and intending to be legally bound hereby, Grantor, its
successors and assigns, does hereby transfer, assign and set over unto Grantee,
its successors, transferees and assigns, all of its present and future right,
title and interest in and to the Trademarks and all proceeds thereof and all
goodwill associated therewith issued under and pursuant to the Power of
Attorney.

      IN WITNESS WHEREOF, the undersigned has caused this Trademark Assignment
to be executed as of the 29th day of October, 1999.



                                    _______________________________________



                                    By:   _________________________________
                                                Attorney-in-fact


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<PAGE>   9
STATE OF                      :
                              :  S.S.
COUNTY OF                     :


      On this 29th day of October, 1999 before me, a Notary Public for the said
County and State, personally appeared known to me or satisfactorily proven to me
to be attorney-in-fact on behalf of IMMUNOGENETICS, INC. ("Grantor") and s/he
acknowledged to me that s/he executed the foregoing Trademark Assignment on
behalf of Grantor, and as the act and deed of Grantor for the purposes therein
contained.

      IN WITNESS WHEREOF, I hereunto set my hand and official seal.




                                          _____________________________________
                                                      Notary Public



My Commission Expires:

____________________________________


                                      -9-
<PAGE>   10
                                POWER OF ATTORNEY

      IMMUNOGENETICS, INC., ("Grantor"), hereby authorizes FLEET CAPITAL
CORPORATION, its successors and assigns, and any officer or agent thereof
(collectively, "Lender") as Grantor's true and lawful attorney-in-fact, with the
power to endorse Grantor's name on all applications, assignments, documents,
papers and instruments necessary for Grantee to enforce and effectuate its
rights under a certain Trademark Security Agreement between Grantor and Lender
dated the date hereof (as it may hereafter be supplemented, restated,
superseded, amended or replaced, the "Trademark Agreement"), including, without
limitation, the power to use the Trademarks (as defined in the Trademark
Agreement) and listed on SCHEDULE A attached hereto and made a part hereof, to
grant or issue any exclusive or nonexclusive license under the Trademarks to
anyone else, or to assign, pledge, convey or otherwise transfer title in or
dispose of the Trademarks, in each case subject to the terms of the Trademark
Agreement.

      This Power of Attorney is given and any action taken pursuant hereto is
intended to be so given or taken pursuant to and subject to the provisions of a
certain Loan and Security Agreement bearing even date herewith among Grantor and
Lender, as each document may be hereinafter supplemented, restated, superseded,
amended or replaced.

      Grantor hereby unconditionally ratifies all that such attorney shall
lawfully do or cause to be done by virtue hereof and in accordance with the
terms of the Trademark Agreement.

      This Power of Attorney shall be irrevocable for the life of the Trademark
Agreement.

      IN WITNESS WHEREOF, the Grantor has executed this Power of Attorney, this
29th day of October, 1999


                                    IMMUNOGENETICS, INC.



                              By:  /s/ Robert E. McDaniel
                                   ___________________________________________


                              Name:  Robert E. McDaniel
                                     ______________________________________

                              Title: Secretary
                                     ______________________________________



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<PAGE>   11
                            CORPORATE ACKNOWLEDGMENT


UNITED STATES OF AMERICA      :
STATE OF                      : SS
COUNTY OF                     :


      On this 29th of October, 1999 personally appeared ____________________, to
me known and being duly sworn, deposes and says that s/he is ______________of
IMMUNOGENETICS, INC., the Grantor corporation described in the foregoing Power
of Attorney; that s/he signed the Power of Attorney as such officer pursuant to
the authority vested in her/him by law; that the within Power of Attorney is the
voluntary act of such corporation; and s/he desires the same to be recorded as
such.





                                          _____________________________________
                                          Notary Public

                                          My Commission Expires:


                                      -11-
<PAGE>   12
                                  SCHEDULE "A"

                                   TRADEMARKS

<TABLE>
<CAPTION>
Name/Title              Registration Number                 Date of Registration
----------              -------------------                 --------------------
<S>                     <C>                                 <C>

</TABLE>


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