<title>Fluorescent capillary fill device: a quantitative whole-blood assay system suited to point-of-care use</title>

Abstract

The Fluorescence Capillary Fill Device (FCFD) has previously been shown to be a candidate test vehicle for the point of care market and instrumentation suitable for commercialisation has now been developed. The FCFD instrumentation is a fluorimeter with custom optics to collect a given angular spread of light from the output edge of the device. Rigorous selection of fluorophore, light source, filters and detector (taking into account cost, availability in manufacturing quantity and the influence of inherent blood fluorescence) was undertaken when optimising the system. The instrument utilises allophycocyanin as a near-red fluorophore, an array of ultra-bright light emitting diodes and an inexpensive photomultiplier. Assay calibration is achieved by incorporating a light source movement mechanism that allows reference zones within the device to be interrogated individually. The resulting instrument has a footprint approximately 10 inches by 8 inches, requires no specialist operator training and is well suited to the point of care market. The capability of the system is illustrated by a whole blood assay for the cancer marker prostate specific antigen (PSA). This assay has a sensitivity of <O.5ng/mL and precision of<lO% between 5ng/mL and 5Ong/mL.