| Polysaccharides, such as heparin and chondroitin sulfate, widely exist in the body of human and animal. In recent years, owing to its biological activities, it has been attracted great interest in food, cosmetics, and medical applications. Therefore, accurate detection of the concentrations of polysaccharides is very important. Mercury ions act as severe environmental pollutants and can cause a number of severe health problems even at low concentrations. Therefore, it is important to determine the concentration of mercury ions. Resonance scattering spectral methods, resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS), have become known for their high sensitivity, simplicity, and rapidity in performance as new analytical techniques in recent years. Up to now, this technique has been applied to the study of biomacromolecules, such as nucleic acids and proteins, saccharides, trace amounts of metals, surfactants, antibiotics, even in the determination of some physicochemical parameters such as the inclusion constant ofβ-cyclodextrin and the critical micelle concentration of surfactant. With the development of nano-materials, different nanomaterials have been used as RRS probes, such as gold nanoparticles, silver nanoparticles, and quantum dots (QDs). In this paper, the interactions of gemini surfactant (dodecyl polyoxyethylene ether biquaternary ammonium salt, DPBAS) with polysaccharide (heparin and chondroitin sulfate) and of gold nanopartical with mercury ions have been studied. The spectral characteristics, influencing factors, and reaction mechanism were investigated. The main contents are as follows:1. The determination of critical micelle concentration of conventional surfactants and gemini surfactant by the resonance scattering spectral methods.The critical concentrations of surfactants were determined without any probes by resonance RRS, SOS and FDS. The RRS, SOS and FDS signals exhibited a similar variation with surfactant concentration. In the IRRsmax-c ISOSmax-c and IFDSmax-c curves, the critical micelle concentrations are inferred from a rather unprecedented drop in the signal intensity. The values of critical premicelle concentration (CPMC) and critical micelle concentration (CMC) of conventional surfactants (sodium dodecyl sulfate, SDS and cetyltrimethylammonium bromide, CTAB) are in good agreement with values of literatures and conductivity method, meanwhile, the value of CMC of DPBAS is in good agreement with the value of conductivity method. Thus, the RRS SOS and FDS methods can be applied to determine the CMC values of surfactants in a sensitive, accurate and no probe way.2. Gemini surfactant applied to the heparin assay at the nanogram level by resonance Rayleigh scattering methodIt was found that DPBAS could react with anionic heparin to form an ion-association complex, which induced the enhancement of RRS intensity and the appearance of a new RRS spectrum in Britton-Robinson buffer (pH 5.5). The RRS spectral characteristics of the heparin-DPBAS system, the optimum conditions of the reaction, and the influencing factors have been investigated. Under the optimum conditions, the enhanced RRS intensity was proportional to the concentration of heparin in the range of 0.05-0.6μg/mL. The method has high sensitivity, and the detection limit for heparin is 4.3 ng/mL. The proposed method has been successfully applied for the determination of heparin in pharmaceutical samples. Furthermore, the mechanism of the interaction between heparin and DPBAS was explored using RRS and conductivity methods, indicating that the gemini surfactant reacting with heparin mainly exists in the form of micellar-type aggregates. This method has been successfully applied for the determination of heparin in drug formulations.3. Study on the interaction of chondroitin sulfate (A) with cationic gemini surfactant by resonance scattering spectral methodsAt pH 4.0 BR buffer medium, cationic gemini surfactant, dodecyl polyoxyethylene ether biquaternary ammonium salt (DPBAS), could react with anionic chondroitin sulfate A (CSA) to form complexes which could enhance the RRS, SOS and FDS intensities strongly. The characteristics of RRS, SOS and FDS spectra of the CSA-DPBAS system, the factors of influence, and the optimum conditions of the assay were investigated. Under the optimum conditions, the increase of scattering intensity (ΔI) was in proportion to the concentrations of CSA in the range of 0.05 to 3.0μg/mL (RRS),0.05 to 4.0μg/mL (SOS) and 0.05 to 4.0μg/mL (FDS), respectively. The proposed three methods have high sensitivity with the detection limits of 1.2,3.6,4.5 ng/mL, respectively, and have been successfully applied to determine CSA in pharmaceutical samples.4. Detection of mercury ions (Ⅱ) based on non-cross-linking aggregation of double-stranded DNA-capped gold nanoparticles by resonance Rayleigh scatteringWe present a simple and rapid sensor for Hg2+ detection with high selectivity and sensitivity, which is based on the non-crosslinking aggregation of double-stranded DNA-carrying gold nanoparticles by the formation of strong and stable T-Hg2+ -T base pairs. The non-crosslinking aggregation is formed only in the presence of Hg2+ and it causes the great enhancement of the intensities of RRS. Under the optimum conditions, the enhanced RRS intensity was in proportion to the concentration of Hg2+ in the range of 2.5-60.0 nM with a detection limit of 1.9 nM. In our work, because of the small amount of double-stranded DNA-capped gold nanoparticles, there was no changs in color and UV-Vis absorption. Thus, this method has high sensitivity. We designed a RRS method for detection of Hg2+, based on the combination of non-crosslinking aggregation of double-stranded DNA-carrying gold nanoparticles, which was the first time used in RRS method. |
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