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                                                                     EXHIBIT 9.1

                             VOTING TRUST AGREEMENT

         THIS AGREEMENT, dated December __________, 2001, by and between
Sentigen Holding Corporation, a Delaware corporation ("Sentigen"), D.H. Blair
Investment Banking Corporation, a Delaware corporation, and its controlling
persons and affiliates, who are identified on Exhibit A attached hereto and made
a part hereof (collectively, "D.H. Blair"), and Frederick R. Adler, a person not
affiliated with and independent of D.H. Blair ("Voting Trustee").

         WHEREAS, D.H. Blair owns or has voting and investment power over
1,124,859 shares ("Shares") of Sentigen's common stock, par value $.01 per share
("Common Stock"), which number of Shares includes Shares held by D.H. Blair
Investment Banking Corporation and by the persons listed on Exhibit A;

         WHEREAS, Sentigen and D.H. Blair deem it necessary, advisable and in
their best interests for D.H. Blair to deposit such Shares and any and all
shares of Common Stock hereafter acquired by D.H. Blair with the Voting Trustee;

         WHEREAS, D.H. Blair has agreed to vest its voting rights in the Shares
and other rights pertaining to the Shares in the Voting Trustee for the period
and upon the terms hereinafter provided; and

         WHEREAS, the Voting Trustee has consented to act under this Agreement
for the purposes herein provided.

         NOW THEREFORE, it is mutually agreed as follows:

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         1.       D. H. Blair hereby appoints Frederick R. Adler, and he hereby
accepts such appointment, as the Voting Trustee under the terms and conditions
set forth herein.

         2.       D. H. Blair represents that the 1,124,859 Shares referred to
above and set forth on Exhibit A attached hereto represent its total direct or
indirect ownership interest in Sentigen. D. H. Blair further covenants that for
the term of this Agreement, it shall not acquire additional shares of Common
Stock or other securities convertible into Common Stock or convertible into the
common stock of any Sentigen subsidiary now existing or established hereafter
unless such acquisition results from a dividend paid on such Shares, a stock
split affecting such Shares, or a rights offering with respect to such shares.

         3.       D. H. Blair represents, to the best of its knowledge, that,
other than its ownership of Common Stock set forth in Paragraph 2 of this
Agreement and Exhibit A attached hereto, no entity which it controls conducts
any business with or has any agreements with Sentigen that are material to
either party, and covenants that for the term of this Agreement it will not
enter into any such arrangements or agreements.

         4.       Simultaneous with the execution of this Agreement, D. H. Blair
shall deposit with the Voting Trustee certificates representing the Shares, duly
endorsed for the transfer thereof to the Voting Trustee, and to the extent D.H.
Blair acquires additional shares of Common Stock as a result of a dividend paid
on the Shares, stock split affecting the Shares, or the exercise of rights in a
right offering with respect to the Shares, it agrees to deposit such additional
shares with the Voting Trustee. The certificates representing the Shares
transferred and delivered to the Voting Trustee

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hereunder shall be immediately surrendered to Sentigen by the Voting Trustee.
Sentigen shall immediately cancel such certificates and issue a new certificate
representing the Shares in the name of "Frederick R. Adler, as Voting Trustee
under a Voting Trust Agreement dated as of April 13, 2001." Upon receipt by the
Voting Trustee of the certificate for the Shares in his name, the Voting Trustee
shall hold the same subject to the terms and conditions hereof and shall
thereupon issue and deliver a voting trust certificate to D. H. Blair, in the
form attached hereto as Exhibit B, for the Shares deposited by D. H. Blair.

         5.       The voting trust certificate shall be transferable only in
accordance with all applicable securities laws. The voting trust certificate
issued hereunder and any additional voting trust certificates shall be issued,
received and held subject to all of the terms and conditions hereof. The Voting
Trustee shall keep the transfer books and records for the voting trust
certificates at the address of the Voting Trustee set forth in Paragraph 17 of
this Agreement, or at such other address as the Voting Trustee may from time to
time designate by written notice thereof to D. H. Blair and Sentigen. If a
voting trust certificate is lost, stolen, mutilated or destroyed, the Voting
Trustee, in his discretion, may issue a duplicate of such certificate upon
receipt of (i) evidence of such fact reasonably satisfactory to him, and (ii)
indemnity reasonably satisfactory to him.

         6.       (a)      Except as set forth in subparagraph (d) below, the
Voting Trustee shall promptly pay to the holder of each voting trust certificate
all cash dividends and distributions, if any, received by the Voting Trustee on
account of the underlying Shares represented by such voting trust certificate.

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                  (b)      If any dividend paid on the Shares is paid in whole
or in part in shares of Sentigen voting stock, or if as a result of a stock
split affecting the Shares or the exercise of rights in a rights offering with
respect to the Shares any additional shares of Sentigen voting stock are issued,
the Voting Trustee shall hold the certificates for shares he receives on account
of such dividend or stock split subject to the terms of this Agreement, and the
holder of each voting trust certificate representing such additional shares
shall be entitled to receive a voting trust certificate for the number of shares
of stock received as a result of such dividend or stock split.

                  (c)      The holders entitled to receive the additional shares
provided for in subparagraph (b) above shall be those registered as such on the
transfer books of the Voting Trustee at the close of business on the day fixed
by Sentigen for the taking of a record to determine those holders of its stock
entitled to receive such shares.

                  (d)      In lieu of receiving dividends and distributions for
the Shares and paying the same to the holders of the voting trust certificates
pursuant to the provisions of subparagraph (a) above, the Voting Trustee may, in
writing, instruct Sentigen to pay the same directly to the holders of such
voting trust certificates. Upon receipt of such written instructions, Sentigen
shall pay the same directly to the holders of the voting trust certificates.

         7.       In the event of the dissolution and liquidation of Sentigen,
whether voluntary or involuntary, the Voting Trustee shall receive the monies,
securities, rights or property to which the holders of the Shares deposited
hereunder are entitled and shall promptly distribute the same among the holders
of voting trust certificates in proportion to their interests as shown on the
books of the Voting Trustee.

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         8.       In the event that Sentigen is merged into or consolidated with
another corporation, or if all or substantially all of the assets of Sentigen
are transferred to another corporation, the Voting Trustee shall receive and
hold under this Agreement any voting stock of any successor corporation which
has been received for the capital stock of Sentigen held by the Voting Trustee
hereunder, and the term "Sentigen" for all purposes of this Agreement shall be
deemed to include such successor corporation.

         9.       (a)      Except as provided in Section 9(b) herein, the Voting
Trustee shall (i) vote the Shares delivered to him hereunder in the same manner
as the public, on a pro rata basis, excluding the votes of officers, directors
and stockholders who own beneficially greater than ten percent of Sentigen's
outstanding voting securities, (ii) have the exclusive right to give waivers of
notice, or to give written consents in lieu of voting, in person or by proxy, at
any meeting of the stockholders of Sentigen, for whatever purpose called in any
manner he deems appropriate and in any proceedings, whether at a meeting of
stockholders or otherwise, where the vote or written consent of the stockholders
may be required or authorized by law.

                  (b)      Notwithstanding anything to the contrary contained
herein, with respect to a vote or consent in connection with either (i) a "Rule
13e-3 Transaction" (as such term is defined in Rule 13e-3 promulgated under the
Securities Exchange Act of 1934) or (ii) a transaction in which stockholders are
afforded appraisal rights pursuant to Section 262 of the Delaware General
Corporation Law, the Voting Trustee shall vote as directed in writing by the
holders of the voting trust certificates.

                  (c)      The Voting Trustee shall not be liable for an error
in judgment or mistake of law or other mistake, nor for anything save his own
willful

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misconduct, recklessness or gross negligence and shall not be required to give a
bond or other security for the faithful performance of his duties, provided,
however, this limitation of liability shall not apply to the obligations of the
Voting Trustee under Sections 6(a), 7, 9(a)(i) and 16 hereof.

         10.      The Voting Trustee shall deliver to D.H. Blair copies of all
notices and other documents he receives as a result of being the record holder
of the Shares, other than proxy cards or other instruments which need to be
executed in order to vote the Shares.

         11.      (a)      The Voting Trustee may resign his position as Voting
Trustee by mailing to the registered holders of voting trust certificates a
written resignation, which shall be effective ten days after the mailing
thereof. The Voting Trustee shall have the right at the time of his resignation
to designate his successor as Voting Trustee under this Agreement, provided,
however, that (i) such successor Voting Trustee is not affiliated with and
independent from D.H. Blair and (ii) the designation of such successor Voting
Trustee is approved in advance and in writing by Sentigen and D.H. Blair. Such
designation, duly executed by the Voting Trustee, shall be made by filing an
instrument of appointment in the principal office of Sentigen. In the event the
Voting Trustee shall die while serving as Voting Trustee, Richard Phillips shall
serve as successor Voting Trustee. Mr. Phillips is a senior partner of the law
firm of Kirkpatrick & Lockhart LLP, with offices at Four Embarcadero Center, San
Francisco, California 94111.

                  (b)      Blair shall have the right to appoint a substitute
Voting Trustee, provided such substitute Voting Trustee is not affiliated with,
and is

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independent from D.H. Blair and is acceptable to the NASD and the Company. The
rights, powers, and privileges of the Voting Trustee hereunder shall be
possessed by the successor or substitute Voting Trustee as the case may be with
the same effect as though such successor had originally been a party to this
Agreement.

         12.      The Voting Trustee shall serve without compensation.

         13.      Sentigen and D.H. Blair shall jointly and severally indemnify
and hold harmless the Voting Trustee from and against all claims, losses,
damages, taxes, and liabilities (collectively, "Damages") that he may incur in
connection with or arising out of the performance of his duties under this
Agreement (other than with respect to actions for which the Voting Trustee may
be liable pursuant to Section 9(b) of this Agreement), including all reasonable
legal costs and expenses incurred in defending himself against any Damages.

         14.      This Agreement shall commence on the date that the Common
Stock is authorized for listing on the NASDAQ Stock Exchange, or any tier
thereof ("NASDAQ"), and terminate upon the earlier of: (i) ten years from the
date hereof; (ii) the de-listing of Sentigen or any successor entity from
NASDAQ; or (iii) the reduction of D.H. Blair's beneficial ownership of
Sentigen's voting stock to one percent or less.

         15.      Should D.H. Blair or a controlling person or an affiliate
listed on Exhibit A attached hereto sell, bequeath, gift, or otherwise transfer
the beneficial interest in its Shares or the Voting Trust Certificates issued
pursuant to this Agreement to another party, such transferred Shares shall
continue to be subject to this Agreement until sold in the open market or
through a private sale pursuant to Section 4(1) of the Securities Act of 1933 as
provided in Section 16 herein.

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         16.      Nothing in this Agreement shall limit D.H. Blair's ability to
(i) make public sales of the Shares in the open market pursuant to an effective
registration statement under the Securities Act of 1933 or pursuant to Rule 144
thereunder, or (ii) make private sales of the Shares pursuant to Section 4(1) of
the Securities Act of 1933, provided, however, that Shares sold in private sales
shall continue to be subject to this Agreement until such time as notice is
given to the Nasdaq Staff and the Staff determines that the purchaser is not
affiliated with D.H. Blair or J. Morton Davis and that Mr. Davis can no longer
exercise influence over those Shares. The Voting Trustee shall use his best
efforts to cooperate promptly upon a request by D.H. Blair to make such public
and private sales.

         17.      All notices, requests, demands, and other communications
hereunder must be in writing and will be deemed to have been duly given if
delivered by hand or mailed within the continental United States by first-class
certified mail, return receipt requested, postage prepaid, to the other party,
addressed as follows:

                  (i)     if to Sentigen to:

                          Joseph K. Pagano
                          590 Marshall Street
                          Phillipsburg, New Jersey 08865

                  (ii)    if to D.H. Blair to:

                          J. Morton Davis
                          D.H. Blair Investment Bank Corp
                          44 Wall Street
                          New York, New York 10005

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                  (iii)   if to the Voting Trustee to:

                          Frederick R. Adler, Esq.
                          Fulbright & Jaworski LLP
                          666 Fifth Avenue
                          New York, New York 10103

                  (iv)    if to the Nasdaq Staff to:

                          Nasdaq Listing Qualifications Department
                          9600 Blackwell Road
                          Rockville, Maryland 20850

         18.      This Agreement and the exhibits attached hereto express the
entire written Agreement between the parties with respect to the subject matter
hereof. This Agreement may not be modified or amended except by written
agreement of each party hereto. Copies of this Agreement and of any modification
or amendment hereunder shall be filed in the principal office of Sentigen and
shall be available for inspection during reasonable business hours by any
Sentigen stockholder or beneficiary of the trusts under this Agreement.

         19.      This Agreement may be executed by the parties hereto in
counterparts, each of which will be deemed to be an original, but all such
counterparts will constitute one and the same instrument, and all signatures
need not appear on any one counterpart.

         20.      In the event that any provision of this Agreement is held to
be illegal or invalid for any reason, the illegality or invalidity will not
affect the remaining parts of the Agreement, and the Agreement will be construed
and enforced as if the illegal or invalid provision had not been included.

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         21.      To the extent not preempted by the laws of the United States,
this Agreement shall be governed by and construed and enforced in accordance
with the laws of the State of Delaware, other than the conflict of law
provisions thereof.

         IN WITNESS WHEREOF, the undersigned parties have executed this
Agreement as of the day and year first written above.

                                         SENTIGEN HOLDING CORPORATION

                                         By:    /s/ Joseph K. Pagano
                                                --------------------------------
                                         Name:  Joseph K. Pagano
                                         Title: President, Chairman of the Board

                                         D.H. BLAIR INVESTMENT BANKING
                                                CORPORATION

                                         By:    /s/ J. Morton Davis
                                                --------------------------------
                                         Name:  J. Morton Davis
                                         Title: Chairman of the Board

                                         FREDERICK R. ADLER

                                         By:    /s/ Frederick R. Adler
                                                --------------------------------
                                                Voting Trustee

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                                    EXHIBIT A

   List of Controlling Persons and Affiliates of D.H. Blair Investment Banking
                     Corporation and their Addresses and the
  Number of Shares of Sentigen Holding Corporation Owned or Controlled by Each

<TABLE>
<S>                     <C>                                     <C>
J. Morton Davis         D.H. Blair Investment Banking Corp.     1,124,859 shares
                        44 Wall Street
                        New York, New York 10005
</TABLE>

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                                    EXHIBIT B

                                  [Front Side]

                            VOTING TRUST CERTIFICATE
                     Representing Shares of Common Stock of
                          SENTIGEN HOLDING CORPORATION

               (Organized under the laws of the State of Delaware)

No.________                                                       ________Shares

         This certifies that the undersigned has deposited _______________
shares of common stock of Sentigen Holding Corporation ("Sentigen"), $.01 par
value, with the Voting Trustee hereinafter named, under an agreement
("Agreement") dated as of ______________, 2001 among Frederick R. Adler ("Voting
Trustee"), Sentigen and D. H. Blair Investment Banking Corporation and its
controlling persons and affiliates.

         This voting trust certificate and the interest represented thereby is
transferable only on the books of said Voting Trustee upon the presentation and
surrender hereof.

         The holder of this certificate takes the same subject to all the terms
and conditions of the Agreement.

         IN WITNESS WHEREOF, the Voting Trustee has caused this certificate to
be signed this _____ day of _______________________, 2001.

Signature of Record Holder                    __________________________________
Name of Record Holder                         Frederick R. Adler, Voting Trustee

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                                 [Reverse Side]

The securities represented by this certificate have not been registered under
the Securities Act of 1933, as amended, or any state Blue Sky or securities
laws. These securities cannot be resold without registration under such Act or
applicable state securities laws or an exemption therefrom.

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