Disposable Optical Sensor Chip for Medical Diagnostics:  New Ways in Bioanalysis

Abstract

An optical sensor system is described which is particularly well suited for medical point-of-care diagnostics. The system allows for all kinds of immunochemical assay formats and consists of a disposable sensor chip and an optical readout device. The chip is built up from a ground and cover plate with in- and outlet and, between, of an adhesive film with a capillary aperture of 50 microns. The ground plate serves as a solid phase for the immobilization of biocomponents. In the readout device, an evanescent field is generated at the surface of the ground plate by total internal reflection of a laser beam. This field is used for the excitation of fluorophor markers. The generated fluorescence light is detected by a simple optical setup using a photomultiplier tube. Because of the evanescent field excitation, washing or separation steps can be avoided. With this system the pregnancy hormone chorionic gonadotropin (hCG) could be determined in human serum with a detection 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 immunoassays was demonstrated for serum theophylline. A linear calibration curve of signal vs theophylline between 1 and 50 mg/L was obtained. Recovery values varied between 118% (10 mg/L) and 81.0% (20 mg/L).

Fabrication of free-standing lithium niobate nanowaveguides down to 50 nm in width

“…It is further unique to the presented approach that the resulting nanowaveguide structures are free-standing and can be easily detached from the substrate. Eventually, the fabrication scheme was used to produce LiNbO 3 nanowaveguides that have been successfully tested optically and clearly showed efficient SHG [24]. In terms of size, free-standing geometry, and due to the sufficiently large frequency conversion efficiency, these waveguides can be understood as counterparts to chemically synthesized nanowires [34,50,51].…”

Trends and Perspectives in Immunosensors

“…It has a maximum intensity at the surface, which is reduced with increasing distance from the surface [92]. These sensors demonstrate high sensitivity and can avoid separation and extraction steps from complex matrices such as body fluids [93,94]. As an example, studies were carried out using TIRF immunosensors to evaluate the concentration of bovine progesterone, a reproductive hormone present in raw milk [95,96].…”

Single Molecular Detection via Micro-Scale Polymeric Opto-Electro-Mechanical Systems

“…Based on TIR, disposable plastic prisms integrated on biochips [61] with several different types of evanescent waveguides, including fiber [62], channel [63], and planar [64,65] waveguides, have been proposed to address the requirements for ultra-sensitive, high-throughput platforms. In all of these systems, the excitation laser beam comes from the side of the chip, which requires highly precise aligned at a specified angle to achieve efficient light coupling and to create a strong evanescent field.…”