Disposable optical sensor chip for medical diagnostics: New ways in bioanalysis

An optical sensor system is described which is particularly well suited for medical point-of-care diagnostics. The system allows for all kinds of immu nochemical assay formats and consists of a disposable sensor chip and an op tical readout device. The chip is built up from a ground and cover plate wi th in- and outlet and, between, of an adhesive film with a capillary apertu re of 50 mu m. The ground plate serves as a solid phase for the immobilizat ion of biocomponents, In the readout device, an evanescent held is generate d at the surface of the ground plate by total internal reflection of a lase r beam. This field is used for the excitation of fluorophor markers. The ge nerated fluorescence light is detected by a simple optical setup using a ph otomultiplier tube. Because of the evanescent field excitation, washing or separation steps can be avoided. With this system the pregnancy hormone cho rionic gonadotropin (hCG) could be determined in human serum with a detecti on limit of 1 ng/mL, Recovery values were 86, 106, and 102% for 5, 50, and 100 ng/mL hCG, respectively. The SD in repeated measurements (n = 10) was 5 .6%, Furthermore, the feasibility of the system in competitive-type immunoa ssays was demonstrated for serum theophylline. A linear calibration curve o f signal vs theophylline between 1 and 50 mg/L was obtained. Recovery value s varied between 118% (10 mg/L) and 81.0% (20 mg/L).