Multi-photon nonlinear laser wave-mixing spectroscopy is presented as a highly sensitive absorption-based detection technique for a wide range of biomedical applications including ultrasensitive detection of neurotransmitters in the striatum, such as dopamine, adenosine, glutamate and ?-aminobutyric acid (GABA) that play important roles in therapies for the treatment of neurodegenerative diseases.  The analytical signal is a coherent laser-like beam and can be collected with virtually 100% collection efficiency and without optical background noise. The signal has a quadratic dependence on analyte concentration, and hence, wave mixing is effective for monitoring small changes in analyte at low concentration.  In a typical wave-mixing setup, two laser beams are focused and mixed inside a capillary where the analytes are separated and detected.  Capillary electrophoresis is used to separate and identify neurotransmitters.  Wave-mixing detection sensitivity levels often exceed those of widely used fluorescence detection methods and wave-mixing detection does not require the use of fluorescence labels and probes.  With proper wavelength tuning, many biomolecules can be detected in their native form. Wave mixing is inherently suitable for interfacing to microfluidics, microarrays, lab-on-a-chip and capillary electrophoresis separation systems in order to further enhance chemical selectivity levels. Nonlinear laser wave mixing is an ideal detection method for monitoring neurotransmitters using a relatively compact and portable detection system.

Ultrasensitive absorption-based detection of neurotransmitters by nonlinear laser wave mixing and capillary electrophoresis

248th National Meeting (2014)

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