Optical biosensors for immunoassays: the fluorescence capillary-fill device

Abstract

This paper reports, for the first time, details of a novel type of optical biosensor for immunoassays, the fluorescence capillary-fill device (FCFD). This is based on a straightforward adaptation of the technology used to mass manufacture liquid-crystal display (LCD) cells to give cheap disposable immunosensors. These merely require contact by the sample to give a result in about a minute, and use certain principles of optical fibres and waveguides to avoid the need for operator attention, for physical separation methods or for washing steps. After a very brief introductory review and classification of optical biosensors, the main features of the FCFD and its associated instrumentation are described. The optical characteristics of the FCFD are then described, followed by accounts of the immunoassay method, the measurement system used in the experiments, the fabrication of FCFD sensors and a detailed description of the design of a competitive immunoassay for human immunoglobulin G (hIgG). The experimental details and the results of a first attempt at such an assay are then presented and discussed. It is concluded that the demonstration of this assay is a significant achievement, because the format of the FCFD, its manufacturing process and its instrumentation are completely novel. Certain problem areas have been identified and quantified; intended further work on these is outlined.

A mathematical model of a biosensor

“…A typical medical product based on this antigen/antibody technology is a particular kind of pregnancy kit. A full description of the fluorescent capillary fill device can be found in Badley et al [1].…”

Integrated optic sensors

“…The method uses specific binding reactions of biological molecules to immobilise sample material at the sensor surface (Badley et al, 1987;and see, for examples, chapter 7). Figure 2.19 shows an example of a biosensor which uses a waveguide and molecules immobilised on the surface to study a binding reaction (Zhou et al, 1990).…”

Fluorescence‐Based Biosensors

“…A controlled volume of the sample is introduced by capillary action, and the presence of the buffer causes the doped film to release the reagents so that they are able to compete with the analyte for sites in the immunosurface. 84 Using such a device, species such as serum rubella antibody, 85 human chorionic gonadotropin 86 and prostate-specific antigen 87 have been detected, even in whole blood, with LODs ranging from 1.1 ð 10 9 to 3.3 ð 10 12 M.…”