A REAGENT DISPENSE VERIFICATION SYSTEM FOR A FULLY AUTOMATED, AMPLIFIED NUCLEIC ACID DIAGNOSTIC INSTRUMENT

摘要

Amplified nucleic acid diagnostics have brought extraordinarily powerful biochemical tools to bear on screening for and diagnosing infectious diseases. For example, current assays routinely permit the detection of 100 particles of human immunodeficiency virus or hepatitis C virus in one mL of blood. Such assays are used for screening the blood supply. To permit reliable automation of these complex and sensitive assays fluidic measurement and control systems are required. Such controls are needed to ensure that correct reagents are reliably dispensed into the reaction tubes. In this paper we will review the design and performance of a prototype Reagent Dispense Verification system for use on a fully-automated, amplified, nucleic acid diagnostic instrument. The system design utilizes hydraulic pressure drop and conductivity as the primary dispense parameters. In addition to the dispense verification function, the system provides a capacitive liquid level sensing function. The pipetting probe design and manufacturing process provide two conductive surfaces separated by an electrically insulating gap over which conductivity is measured. Hydraulic pressure drop is measured with an in-line, flow-through pressure transducer. The time-varying pressure and conductivity signals are used to classify each dispense operation as acceptable or not. Overall system performance data are presented demonstrating the viability of the design.