Piezoelectric Sensing Of Chiral Amino Acids Based On Signal Amplification By Gold Nanoparticles

Molecular recognition is the common basis of the bio-system of nature. Chiralrecognition, an important and special recognition, is the basic model of molecularrecognition in the bio-system and one of the important fields of chemistry. A betterunderstanding of the interactions operating in chiral recognition is helpful in learningmany important life processes, interaction mechanism of chiral drugs and biologicalenzymes and in understanding many developing new methods of asymmetric synthesisand chromatographic resolution of enantiomers.With the development of moderntechnology, analysis of chiral compounds is also evolving. Piezoelectric sensinganalysis of chiral recognition is a new detection method of chiral interaction to combinehigh sensitive piezoelectric mass sensing with recognition between chiral hosts andguests, with a high detection speed, high sensitivity, simple operation, real-timemonitoring and so on. In this paper, a new method for chiral recognition of cysteinewere studied, we constructed liquid phase device of piezoelectric chiral recognitionsensors and using self-assembled monolayer of cyclodextrin as chiral selectivity film onpiezoelectric sensor. On this basis, gold nanoparticles were used as a mass signalamplifier to increase the strength of chiral sensor signals of the enantiomer, and furtherimprove the detection sensitivity and the effect of chirality distinguish. The developedsensing method not only ahieve chiral recognition of enantiomeric sulfhydrylcompounds at low concentrations of micromolar level, but also greatly enhance thechiral recognition ability of the sensor. A series of significant studies were made basedon gold nanoparticles used as marker to amplify sensing signal in qualitative distinctionbetween cysteine enantiomers and quantitative detection enantiomeric purity.First, we constructed the QCM liquid sensing device based on functionalcyclodextrins self-assembled film. The device has good gas and liquid phase stability,can real time and online monitoring of the chiral recognition process in liquid phase.Mono-6-mercapto-β-cyclodextrin was fixed on the electrode as chiral selectivemembrane by self-assembly method. The formation of the self-assembled monolayerwere characterized and validated using in situ QCM test, show thatmercapto-β-cyclodextrin monolayer was successfully assembled to the gold electrodesurface, and deduce the mercapto-β-cyclodextrins on the electrode surface is arranged inthe form of the hexagonal closed packing. The influence of pH value on the quantity cyclodextrin modified was discussed. When the pH value reached10, the amount ofmodification is maximum and the surface density is8.06x10-11mol/cm2. Thepreparation process of SAM has good reproducibility. This chapter builds a goodreproducibility, high sensitivity of piezoelectric sensor platforms of the chiralrecognition.Second, the paper introduces a QCM device to study the chiral recognition processon the sensing surface combined with nano materials. Self-assembled film ofcyclodextrin was modified on the piezoelectric sensor for chiral selectivity,enantioselective recognition of cysteine were mainly studied. The results found thatcyclodextrin on electrode directly detect small molecules such as amino acid, thesensitivity is not high, signal strength is weak and chiral recognition factor is not high.According to the basic principle that the gold nanoparticles can increase its weight onsensing surface, we improve the sensing method of chiral recognition. Accordingly, weprepared gold nanoparticles marked cysteine molecules to make amino acid molecule"bigger" and then interact with cyclodextrin on the sensing surface, effectively increasethe sensing signal intensity of amino acids. The introduction of gold nanoparticles hasthe obvious function for the improvement of the sensor signal, the detection sensitivityand the effect of chiral distinction. Finally the signal amplification sensing method isapplied to the enantiomeric purity test of actual sample. The enantiomeric purity testingof cysteine by this method had high measurement accuracy that was not influenced bythe existence of other enantiomers. The QCM sensor system based on GNPs signalamplification can be used to effectively identify and distinguish between L-andD-cysteine, and rapid, real-time, in situ determination of enantiomeric purity. Theadvantage is the increased sensitivity and improved accuracy of the enantiomeric puritytest, lower detection limit and the reduced amount of sample for detection, thesystematic errors of instrument itself is also reduced.Finally, we discussed the problems existing in the piezoelectric sensing analysis ofchiral recognition based on the GNPs tag signal amplification method and forecast theprospects of application of the piezoelectric sensor combined with nanometertechnology in chiral recognition field.