<PAGE>   1
EXHIBIT *(10.36)

THE OBLIGATIONS EVIDENCED HEREBY ARE SUBORDINATE IN THE MANNER AND TO THE EXTENT
SET FORTH IN THAT CERTAIN SUBORDINATION AGREEMENT (THE "SUBORDINATION
AGREEMENT") DATED AS OF OCTOBER 29, 1999, AMONG FLEET CAPITAL CORPORATION,
AMERICAN CAPITAL STRATEGIES, LTD., IGI, INC., IGEN, INC., IMMUNOGENETICS, INC.,
AND BLOOD CELLS, INC., TO THE INDEBTEDNESS AND OTHER LIABILITIES OWED BY IGI,
INC., IGEN, INC., IMMUNOGENETICS, INC., AND BLOOD CELLS, INC. UNDER AND PURSUANT
TO THE LOAN AND SECURITY AGREEMENT DATED AS OF OCTOBER 29, 1999, AND EACH
RELATED "LOAN DOCUMENT" (AS DEFINED THEREIN), AND EACH HOLDER HEREOF, BY ITS
ACCEPTANCE HEREOF, ACKNOWLEDGES AND AGREES TO BE BOUND BY THE PROVISIONS OF THE
SUBORDINATION AGREEMENT.


       IGI, INC., IGEN, INC., IMMUNOGENETICS, INC., AND BLOOD CELLS, INC.
            SERIES A SENIOR SUBORDINATED NOTE DUE SEPTEMBER 30, 2006

No. SSN - 1                                                   October 29, 1999
$6,650,000

         FOR VALUE RECEIVED, the undersigned IGI, INC., a Delaware corporation,
("IGI"), IGEN, INC., a Delaware corporation ("Igen"), IMMUNOGENETICS, INC., a
Delaware corporation, ("ImmunoGenetics"), and BLOOD CELLS, INC., a Delaware
corporation ("Blood Cells") (IGI, Igen, ImmunoGenetics and Blood Cells are
referred to herein as the "Loan Parties"), hereby promise to pay to AMERICAN
CAPITAL STRATEGIES, LTD., or registered assigns (the "Holder"), the principal
sum of SIX MILLION SIX HUNDRED FIFTY THOUSAND DOLLARS ($6,650,000), with
interest thereon, on the terms and conditions set forth in the Purchase
Agreement (as defined herein).

         Payments of principal of, interest on and any premium with respect to
this Note are to be made in lawful money of the United States of America by
check mailed and addressed to the registered Holder hereof at the address shown
in the register maintained by the Loan Parties for such purpose, or, at the
option of the Holder, in such manner and at such other place in the United
States of America as the Holder hereof shall have designated to the Loan Parties
in writing.

         Notwithstanding any provision to the contrary in this Note, the
Purchase Agreement or any other agreement, the Loan Parties shall not be
required to pay, and the Holder shall not be permitted to contract for, take,
reserve, charge or receive, any compensation which constitutes interest under
applicable law in excess of the maximum amount of interest permitted by law.
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         This Note is one of a series of Series A Senior Subordinated Notes Due
September 30, 2006 (herein called the "Notes") issued pursuant to the Note and
Equity Purchase Agreement, dated as of October 29, 1999 (as from time to time
amended, the "Purchase Agreement"), between the Loan Parties and American
Capital Strategies, Ltd., a corporation organized and existing under the laws of
the State of Delaware, and is entitled to the benefits thereof. All terms used
herein shall have the meanings ascribed to them in the Purchase Agreement. Each
Holder of this Note will be deemed, by its acceptance hereof, to have agreed to
the provisions and to have made the representations and warranties set forth in
Article 6 of the Purchase Agreement.

         The Notes are issuable as registered notes. This Note is transferable
only by surrender hereof at the principal office of the Loan Parties at Wheat
Road and Lincoln Avenue, Buena (Atlantic County), New Jersey, duly endorsed or
accompanied by a written instrument of transfer duly executed by the registered
Holder of this Note.

         This Note is also subject to optional prepayment, in whole or in part
at the times and on the terms specified in the Purchase Agreement, but not
otherwise.

         If an Event of Default as defined in the Purchase Agreement occurs and
is continuing, the unpaid principal of this Note may be declared or otherwise
become due and payable in the manner, at the price (including any applicable
premium) and with the effect provided in the Purchase Agreement.

         Payments of principal, interest on and any premium with respect to this
Note are secured pursuant to the terms of the Security Documents.

         This Note and the rights and obligations of the parties hereto shall be
deemed to be contracts under the laws of the State of Maryland and for all
purposes shall be governed by and construed and enforced in accordance with the
laws of said State, except for its rules relating to the conflict of laws.

                                        IGI, INC.



                                        By: /s/ Paul Woitach
                                            ____________________________________
                                            Name: Paul Woitach
                                            Title: President


                                        IGEN, INC.



                                        By: /s/ Paul Woitach
                                            ____________________________________
                                            Name: Paul Woitach
                                                  President
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                                            Title:


                                        IMMUNOGENETICS, INC.



                                        By: /s/ Paul Woitach
                                           ____________________________________
                                            Name: Paul Woitach
                                            Title: President


                                        BLOOD CELLS, INC.



                                        By: /s/ Paul Woitach
                                           _____________________________________
                                            Name: Paul Woitach
                                            Title: President