<PAGE>
                                                                   EXHIBIT 10.12


[COLORADO BUSINESS LEASING, INC. LETTERHEAD]

NOTE NO.: 9000228-001

$280,000.00                                               DATE: November 1, 2000

For value received, the undersigned and each thereof, promises to pay to
COLORADO BUSINESS LEASING, INC. or its order, at said company in Denver,
Colorado, TWO HUNDRED EIGHTY THOUSAND DOLLARS and NO CENTS with interest thereon
from the date hereof until maturity at a rate of 10.75 PERCENT, and after
maturity at the prime rate plus FIVE PERCENT. The makers and endorsers hereof,
and all persons who are or may become parties to this instrument, hereby waive
presentment for payment, protest, notice of nonpayment and of protest, and agree
to any extensions of time of payment and partial payments before, at, or after
maturity, to the addition or release of any party or person primarily or
secondarily liable, to the release or substitution of any or all collateral and
to any other indulgence granted by the holder to any party liable thereon.

The principal of this note is repayable as follows:

THIRTY-SIX monthly payments at $9,052.63 principal and interest beginning
NOVEMBER 1, 2000 and on the FIRST day of each month thereafter. The entire
balance shall be due on or before OCTOBER 1, 2003. If a payment is 10 DAYS OR
MORE LATE, Borrower will be charged an additional amount equal to 5% of the
payment.

Maturity of all principal and interest due hereunder shall at the option of the
holder be accelerated and such principal and interest be immediately due and
payable at the option of the holder without notice or demand upon the occurrence
of any of the following events of default: (a) Failure to pay when due any
installment of principal or interest; (b) default in the performance of any
other liability or undertaking to the holder of any maker, endorser or guarantor
hereof; including violation of the financial covenants noted below; (c) when the
holder hereof in good faith deems itself insecure or feels that the prospect of
payment of this note is impaired; (d) death, dissolution, insolvency (or the
occurrence of anything in the opinion of the holder evidencing insolvency),
termination of existence of, or the commencement of any proceedings under any
bankruptcy or insolvency laws by or against, any maker, endorser or guarantor
hereof. The undersigned will pay on demand all costs of collection of the
indebtedness due hereunder, including reasonable attorneys' fees, paid or
incurred by the holder, and the same shall constitute a part of the indebtedness
represented hereby and be secured by any and ail collateral securing this
promissory note.

Any deposits or other sums credited by or due from the holder to any maker,
endorser or guarantor hereof and any property of any maker, endorser or
guarantor in the holder's possession may at all times be held and treated as
collateral security for the payment hereof, and the holder may set off or apply
the same against any matured liability hereunder at any time.

No failure to exercise or delay in exercising any right hereunder of the holder
shall operate as a waiver of such right or of any other right hereunder, nor
shall any waiver by the holder be construed as a waiver of such right on any
future occasion. If executed by more than one maker, the obligation represented
hereby shall be joint and several. After default the holder may apply payment on
account hereof, however designated, to principal or interest in the holder's
discretion.

DURING THE TERM OF THIS PROMISSORY NOTE, OBLIGOR WILL MAINTAIN THE FOLLOWING
         FINANCIAL COVENANTS:
         MAINTAIN MINIMUM NET WORTH INCLUDING SUBORDINATED DEBT NOT LESS THAN
           $750,000.
         MAINTAIN MAXIMUM DEBT EXCLUDING SUBORDINATED TO NET WORTH INCLUDING
           SUBORDINATED OF LESS THAN 1.25:1.
         MAINTAIN CURRENT RATIO GREATER THAN 1.1.
         MAINTAIN MINIMUM TRADITIONAL CASH FLOW COVERAGE OF 5:1.

The laws of the State of Colorado shall govern this Promissory Note.

BORROWER:   AspenBio, Inc.


BY
  --------------------------------
      Roger Hurst, President