AMENDMENT NO. 3 TO REVOLVING/TERM CREDIT AND SECURITY AGREEMENT

Exhibit 10.1

AMENDMENT NO. 3 TO

REVOLVING/TERM CREDIT AND SECURITY AGREEMENT

THIS AMENDMENT NO. 3 TO REVOLVING/TERM CREDIT AND SECURITY AGREEMENT (this “Amendment”), dated as of October 3, 2005, is entered into by and among the financial institutions listed on the signature pages hereof (individually, a “Lender” and collectively, the “Lenders”), UNION BANK OF CALIFORNIA, N.A., as Administrative Agent, BROWN BROTHERS HARRIMAN & CO., as Collateral Agent, and SERACARE LIFE SCIENCES, INC., a California corporation (the “Borrower”), with reference to the following facts:

RECITALS

A. The Borrower, the Lenders, the Administrative Agent and the Collateral Agent are parties to the Revolving/Term Credit and Security Agreement, dated as of September 14, 2004, as amended (collectively, the “Credit Agreement”), pursuant to which the Lenders have provided the Borrower with a revolving loan, a term loan and a letter of credit facility.

B. The Borrower the Lenders, the Administrative Agent and the Collateral Agent wish to amend the Credit Agreement to increase the Aggregate Revolving Loan Commitment by $15,000,000, from $10,000,000 to $25,000,000, to add a swing line facility in the amount of $2,000,000, and to make certain other modifications, all as set forth below.

NOW, THEREFORE, the parties hereby agree as follows:

1. Defined Terms . Any and all initially-capitalized terms used in this Amendment (including, without limitation, in the recitals hereto) without definition shall have the respective meanings specified in the Credit Agreement.

2. Increase in Revolving Credit Facility .

A. Amendment to Definition of “Aggregate Revolving Loan Commitment” . Section 1.1 of the Credit Agreement is hereby amended such that the definition of “ Aggregate Revolving Loan Commitment ” shall read in full as follows:

“‘ Aggregate Revolving Loan Commitment ’: The sum of the Revolving Loan Commitments set forth on the signature pages hereof, which is, as of the effective date of the Third Amendment, US $25,000,000.”

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B. Addition of Definition of Third Amendment . Section 1.1 of the Credit Agreement is hereby further amended and supplemented by adding therein a new definition of “Third Amendment” as follows:

“‘ Third Amendment ’ means Amendment No. 3 to Revolving/Term Credit and Security Agreement, dated as of October 3, 2005, by and among the Borrower, the Lenders, the Administrative Agent and the Collateral Agent.”

3. Addition of Swing Line Facility .

A. Addition of Swing Line-Related Definitions . Section 1.1 of the Credit Agreement is hereby amended and supplemented by adding the following new definitions therein:

“ Swing Line ” means the revolving line of credit established by the Swing Line Lender in favor of the Borrower pursuant to Section 2.1A.

“ Swing Line Commitment ” means an amount equal to the lesser of (i) $2,000,000 or (ii) the then applicable Available Revolving Loan Commitment.

“ Swing Line Lender ” means UBOC or any successor swing line lender hereunder.

“ Swing Line Loan ” means a loan which bears interest at a rate per annum equal to interest payable on Prime Rate Loan and made by the Swing Line Lender to the Borrower under the Swing Line.

“ Swing Line Note ” means the promissory note made by the Borrower to the Swing Line Lender, substantially in the form of Exhibit L , either as originally executed or as the same may from time to time be supplemented, modified, amended, renewed, extended or supplanted.

“ Swing Line Outstandings ” means, as of any date of determination, the aggregate principal amount of Swing Line Loans then outstanding.

B. Amendment to Revolving Loan Provision to Incorporate Swing Line Loan . Section 2.1(a) of the Credit Agreement is hereby amended to read in full as follows:

“(a) Subject to the terms and conditions hereof, each Lender shall, pro rata, according to such Lender’s pro rata share of the then applicable Aggregate Revolving Loan Commitment, (i) make loans on a revolving credit basis to the Borrower from time to time from and including the Closing Date to but excluding the Maturity Date (each a ‘ Revolving Loan’ , and collectively, the ‘ Revolving Loans’ ) in accordance with the terms of this Agreement and (ii) issue Letters of Credit for the account of the Borrower pursuant to Section 2.2 below from time to time from and including the Closing Date to but excluding the Maturity Date; provided , however , that (A) the sum of (1) the aggregate principal amount of all Revolving Loans outstanding, (2) the aggregate principal amount of all Swing Line Loans outstanding, (3) the aggregate Letter of Credit Amount of all

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Letters of Credit outstanding and (4) the aggregate amount of unreimbursed drawings under all Letters of Credit shall not exceed the lesser of (x) the Aggregate Revolving Loan Commitment or (y) the Borrowing Base at any time and (B) the sum of (1) the aggregate Letter of Credit Amount of all Letters of Credit outstanding and (2) the aggregate amount of unreimbursed drawings under all Letters of Credit shall not exceed $1,000,000 at any time. Within the limits of each Lender’s Revolving Loan Commitment and the Borrowing Base, the Borrower may borrow, have Letters of Credit issued for the Borrower’s account, prepay Revolving Loans, reborrow Revolving Loans, and have additional Letters of Credit issued for the Borrower’s account after the expiration of previously issued Letters of Credit.”

C. Addition of Swing Line Provisions . Section 2 of the Credit Agreement is hereby amended and supplemented by adding therein:

“2.1A Swing Line

(a) The Swing Line Lender shall from time to time prior to the Maturity Date make Swing Line Loans to the Borrower in such amounts as the Borrower may request; provided , however , that (i) after giving effect to such Swing Line Loan, the Swing Line Outstandings shall not exceed the Swing Line Commitment, and (ii) without the consent of the Lenders and the Swing Line Lender, no Swing Line Loan shall be made during the continuation of an Event of Default. Unless notified to the contrary by the Swing Line Bank, advances under the Swing Line may be made in amounts of at least $100,000 and integral multiples of $25,000 in excess thereof. Each request by the Borrower for a Swing Line Loan shall be made pursuant to a Loan Request (or telephonic request for Loan promptly confirmed by telecopier) received by the Administrative Agent, at the Administrative Agent’s office, not later than 9:00 a.m., California time, on the date (which must be a Business Day) such Swing Line Loan is to be made. Each repayment of a Swing Line Loan shall be in an amount which is an integral multiple of $25,000 or the remaining outstanding principal amount of Swing Line Loans.

(b) The Swing Line Loans shall bear interest at a fluctuating rate per annum equal to the rate of interest payable on Prime Rate Loans payable on such dates, not more frequently than monthly, as may be specified by the Swing Line Lender and in any event on the Maturity Date. Interest on Swing Line Loans shall be payable upon demand of the Swing Line Lender, and the Swing Line Lender shall be responsible for invoicing the Borrower for such interest. The interest payable on Swing Line Loans is solely for the account of the Swing Line Lender.

(c) The principal amount of the Swing Line Loans shall be payable not later than three (3) days following demand made by the Swing Line Lender and in any event on the Maturity Date.

(d) Upon the making of each Swing Line Loan by the Swing Line Lender, each Lender shall be deemed to have purchased from the Swing Line Bank a participatio