Raman spectroscopy has advantages over infrared absorption spectroscopy. Combined with a novel multivariate technique, hybrid linear analysis (HLA), low prediction error is expected. A near-infrared (NIR) light source excited Raman... more
Raman spectroscopy has advantages over infrared absorption spectroscopy. Combined with a novel multivariate technique, hybrid linear analysis (HLA), low prediction error is expected. A near-infrared (NIR) light source excited Raman signals, and a charge coupled device (CCD) camera was used to collect the signal. Samples were collected from 69 individuals for 7 weeks. The standard multivariate calibration technique, partial least squares (PLS) and HLA were both used to analyze the collected spectra. A Clarke error grid was used to evaluate the usefulness of the glucose measurement in serum. The root mean squared error of prediction (RMSEP) for glucose in serum obtained with PLS is 21 mg/dL, and the RMSEP obtained with HLA is 17 mg/dL. In whole blood, the PLS RMSEP for glucose was 79 mg/dL, and HLA predictions had an RMSEP of 63 mg/dL. The measurement technique was robust over the 7-week period. HLA was shown to generate a lower prediction error than PLS. The predictions by both PLS and HLA were clinically acceptable. The result with whole blood requires further improvement.
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To obtain a coding system for multiplex detection, we have developed a method to synthesize a new type of nanomaterial called composite organic-inorganic nanoparticles (COINs). The method allows the incorporation of a broad range of... more
To obtain a coding system for multiplex detection, we have developed a method to synthesize a new type of nanomaterial called composite organic-inorganic nanoparticles (COINs). The method allows the incorporation of a broad range of organic compounds into COINs to produce surface enhanced Raman scattering (SERS)-like spectra that are richer in variety than fluorescence-based signatures. Preliminary data suggest that COINs can be used as Raman tags for multiplex and ultrasensitive detection of biomolecules.
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Achieving high signal amplification in surface-enhanced Raman scattering (SERS) is important for reaching single molecule level sensitivity and has been the focus of intense research efforts. We introduce a novel chemical enhancer,... more
Achieving high signal amplification in surface-enhanced Raman scattering (SERS) is important for reaching single molecule level sensitivity and has been the focus of intense research efforts. We introduce a novel chemical enhancer, lithium chloride, that provides an additional order of magnitude increase in SERS relative to previously reported enhancement results. We have duplicated single molecule detection of the DNA base adenine that has previously been reported, thereby providing independent validation of this important result. Building upon this work, we show that the chemical enhancer LiCl produces strong SERS signal under a wide range of experimental conditions, including multiple laser excitation wavelengths and target molecule concentrations, for nucleotides, nucleosides, bases, and dye molecules. This is significant because while selection of anions used in chemical enhancement is well known to affect the degree of amplification attained, cation selection has previously been reported to have no major effect on the magnitude of SERS enhancement. Our findings indicate that cation selection is quite important in ultra-sensitive SERS detection, opening the door to further discussion and theory development involving the role of cations in SERS.