| Gold nanorods attracted attention and developed rapidly owing to anisotropic configuration and unique optical properties, which can be widely exploited to recognize specific analytes such as amino acid, metal ion, antibody, DNA sequence and for cancer cell imaging and photothermal therapy, and to make different self-assembled mode. However, the application of plasmon resonance light scattering (PRLS) signals of gold nanorods is relatively ill explored, especially for quantitative analysis. In this paper, we prepared gold nanorods in aqueous solution, with a rather large yield, narrow size distribution and good reproducibility and applied to analyse of DNA hybridization and single nucleotide polymorphism and measurement of polysaccharides medicament heparin and chitosan with plasmon resonance light scattering (PRLS) signals of gold nanorods. The main content is as follows:1. A one-step label-free optical genosensing method has been developed by taking short DNA target with its sequence related to the human immunodeficiency virus type 1 as an example. By employing anisotropic nonspherical and positive-charged gold nanorods (Au-NRs) as the recognition platform of the short DNA sequence, which show high stability against aggregation under high ionic strength conditions without any additional stable reagent, we found that the addition of target DNA to the mixture of non-modified Au-NRs suspension and the label-free probe DNA in high ionic strength buffer leads up to color change from red to light purple in less than 5 minutes, displaying strong plasmon resonance light scattering (PRLS) signals. Mechanism investigations showed that the strong PRLS signals should be ascribed to the aggregation of Au-NRs caused by double-stranded oligonucleotides (dsDNA) owing to the hybridization of target DNA with the probe DNA. With the PRLS signals, we monitored the hybridization of a 21-mer single-stranded oligonucleotide (ssDNA) from the HIV-1 U5 long terminal repeat (LTR) sequence. It was found that a detection limit of 80 pM of HIV-1 DNA could be achievable, and single-base-pair mismatches are easily detected. It was demonstrated that the developed method in this work has simplicity, sensitivity, specificity, and reliability for sequence-specific DNA detection related to HIV gene.2. Experiments showed that gold nanorods have weak PRLS signals because they are dispersive in the solution. However, remarkable enhanced PRLS signals resulting from the aggregation of gold nanorods could be observed when they interact with polysaccharides medicament such as heparin and chitosan. The enhanced PRLS signals are certified to be proportional to the concentration of the polysaccharides medicament in a certain range, thus the mechanism of interaction between gold nanorods and polysaccharides medicament was studied and a new PRLS method based on the aggregation of gold nanorods was proposed to determine trace heparin and chitosan.(1) The electrostatic interaction of gold nanorods with heparin has been studied with the measurements of plasmon resonance light scattering (PRLS), plasmon resonance absorption, SEM and dynamic light scattering. Based on the PRLS method of gold nanorods, we can determine heparin in the range of 0.02～0.7μg/mL with the limit of determination (3a) of 8 ng/mL under the optimum conditions in BR buffer solution of pH 5.33 containing 60 mmol/L NaCl and 6.4×10-5 mol/L gold naonorods. The method has been applied to determine clinical heparin sodium injections with satisfactory results.(2) Experiments have indicated that chitosan could interact with gold nanorods by electrostatic interaction and amino group coordination interaction, resulting in strong enhanced plasmon resonance light scattering (PRLS). In Britton-Robinson buffer solution with pH value of 7.00, with gold nanorods concentration at 4.0×10-5 mol/L, 8.0×10-5mol/L, respectively, the linear ranges of the ones that determine the chitosan are 0.005-0.20μg/mL, 0.04-0.30μg /mL, and the limits of determination are 2.3 ng/mL, 4.0 ng/mL, respectively. This method is valuable in the determinenation of trace chitosan.
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