Sensitive absorption-based laser wave-mixing spectroscopic methods in microsystems for biomedical applications

Absorption-based laser wave mixing is presented as a sensitive detection method for the study of biomolecules in microsystems. Wave mixing offers many important advantages including detection in very small probe volumes, effective use of low-power lasers, and small sample requirements. These features allow easy coupling with microcapillaries, microarrays, and microchips.; Ultrasensitive detection of proteins and cancer-related antibodies flowing in a microcapillary is performed. A chromophore is used to detect proteins by an optical absorption shift. Preliminary detection limits of 3.4 x 10-19 M (1.7 x 10-22 mol) and 6.4 x 10-14 M (2.6 x 10-17 mol) are determined for BSA and HPV antibody, respectively.; Trypsin and proteinase K enzyme activities are analyzed using casein protein labeled with BODIPY dye molecules. The activity of trypsin and proteinase K are compared using wave-mixing and fluorescence methods. Preliminary concentration detection limit of 6.34 x 10-14 M (1.51 pg/mL) is determined for trypsin.; Wave mixing is investigated as a novel method for measurement of fluorescence resonance energy transfer. End-to-end distances of DNA strands are determined by measuring energy transfer between a fluorophore and a quencher molecule attached to the 5' ends of DNA strands.; For the first time, wave mixing is used for detection and imaging of DNA and cytokine antibody microarrays. Intra-spot resolution is obtained using a focused laser beam diameter of 32 mum. For the DNA microarray, preliminary concentration detection limits of 7.4 x 10-16 M and 8.7 x 10-16 M are determined for a marker spot and an oligonucleotide spot, respectively. For the antibody/protein microarray, preliminary detection limits of 0.05 pg/mL are determined for cytokines.; Laser wave mixing is presented as an effective detection method for biometals in a capillary electrophoresis microchip system. Preliminary concentration detection limits of 0.15 ppb or 2.6 x 10-9 M and 5.4 ppb or 8.5 x 10-8 M are determined for Ni and Cu, respectively.