Microchip-based fluorescence detection

Huang, Z., Munro N., Huhmer, A.F.R., and Landers, J.P, Acousto-optical deflection-based laser beam scanning for fluorescence detection on multichannel electrophoretic microchips, Anal. Chem. 71, 5309, 1999. 

Monoclonal antibody-binding affinity was determined by microchip-based capillary electrophoresis with LIF detection (33). The mixing was carried out off-chip, and the on-chip separations were performed in less than 60 s (Fig. 9). A Scatchard plot analysis resulted in an affinity constant for the monoclonal anti-BSA antibody to fluorescently labeled BSA (BSA ) of... 

Sanders, J.C., Huang, Z.L., Landers, J.P., Acousto-optical deflection-based whole channel scanning for microchip isoelectric focusing with laser-induced fluorescence detection. Labchip 2001, 1, 167-172. 

Renzi et al. demonstrated a hand-held microchip-based analytical instrument for detection of proteins [41]. Recently, a portable microfluidic flow cytometer with simultaneously detection of fluorescence and impedance was reported for cell analysis [42]. This system exploited an LED for excitation and detected fluorescent emission with a solid-state photomultiplier (SSPM). 

LIF detection is the most sensitive optical method so far, but is hard to miniaturize in order to satisfy the ultimate goal of a microfluidic chip that assembles all analytical processes within one micrometerscale microstructure. Therefore, how to achieve the miniaturization of fluorescence detection on microdevices is becoming an active field for lab-on-a-chip research. Several examples demonstrate recent advances in miniaturized LIF detection on the microchip. In 2005, Renzi et al. designed a hand-held microchip-based analytical instrument that combines fluidic, optics, electrical power, and interface modules and integrates the functions of fluidics, microseparation, lasers, power supplies etc., into an... 

Amino acids and peptides are easily labeled with fluorescent dyes. CZE, CGE, or MEKC in capillary or microchip-based SCCE can typically resolve these analytes. Microchip-based SCCE offers higher sensitivity for very small samples, and higher electric field strengths can be used without Joule heating problems. Capillary-based SCCE offers a much higher peak capacity and the use of UV absorbance detection of unlabeled analytes. 

Resolution of the enantiomers in a racemic mixture will require the use of a chiral selector such as a cyclodextrin. Fluorescently labeled analytes can be detected at very low concentration using microchip-based SCCE, and unlabeled analytes can be easily detected with UV absorption using capillary-based SCCE. The long separation times available with capillary-based SCCE allows the use of less than optimal chiral resolving agents, whereas a more selective chiral selector is needed in microchip-based SCCE. 

Munro et al. showed separation and detection of amino acids on microchips using an indirect fluorescence detection method. Figure 36.10 shows application of this method to urine samples with no pretreatment other than dilution in the appropriate separation buffer. Abnormal amounts of amino acids can easily be detected in the two patient samples compared to the healthy control sample. An absorbance detection based approach was utilized for the clinical analysis of calcium ion in serum, which is important in the regulation of a number of physiological processes. Beads with an immobilized calcium reactive dye were placed into the detection region, and the samples mobilized past the beads using electrophoretic flow. While a true separation was not intended, the interference... 

Hofmann O et al (2005) Towards microalbuminuria determination on a disposable diagnostic microchip with integrated fluorescence detection based on thin-fihn organic light emitting diodes. Lab Chip 5 863-868... 

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