Prepararion And Application Of The Label-free Biosensors

In this paper, the finished major works are as follows,1. An label-free electrochemical DNA sensor for the detection of thrombin isproposed based on controlled fabrication of gold nanoparticles (GNPs) and DNAinside the pores of mesoporous silica (MPS). The MPS precursor was mixed withtrimethylchlorosilane (TMCS) firstly to block the external surface silanol groups, thencalcined to remove the template agent, afterwards the internal pore walls were graftedamino group by mixed with aminopropyltriethoxyl silane (APTS). The obtainedmodified mesoporous silicon was named as APTS-TMCS-MPS. The GNPs wereconfined inside the mesopores of APTS-TMCS-MPS by adding mesoporous siliconinto HAuCl4and NaBH4solution, The GNPs/APTS-TMCS-MPS were formed.HS-ssDNA could interact with the GNPs which were confined inside the mesopores ofAPTS-TMCS-MPS through Au-S bond, then DNA was assembled inside the channelof mesoporous silica, thus the label-free probe of DNA/GNPs/APTS-TMCS-MPS wasobtained. The prepared probes were used to modify glassy carbon electrode (GCE) toconstruct a label-free electrochemical aptamer sensor. After incubating the sensor intothe solution of thrombin, the nonconductive conjugates of DNA and thrombin wereformed on the surface of GCE, and the spatial block increased, result in the decrease ofcurrent signal. Thus, the detection of thrombin was achieved. The experimental resultsshow that, The GNPs inside the mesopores could promote the electron transportationthrough the pore channel. Under the optimal experimental conditions, the fabricatedaptamer sensor could detect thrombin in a linear range from1.0×10-8to1.0×10-6mol L-1with a detection limit of7.5×10-9mol L-1(3σ).2. A label-free chemiluminescent immunosensor for the determination ofα-fetoprotein(AFP) is proposed based on the chemiluminescence resonance enerfytransfer(CRET) system of Luminol-H2O2-horseradish peroxide(HRP) and CdSe.Synthesizing the CdSe quantum dots with carboxyl group in water phase, then theCdSe were confined inside the mesopores of APTS-TMCS-MPS by the interactionbetween carboxyl and amino group, the CdSe/APTS-TMCS-MPS were prepared.Monoclonal antibodies of AFP(anti-AFP) was immobilized inside the channels ofCdSe/APTS-TMCS-MPS to prepare the label-free immunoprobe for the detection of AFP. The solution of HRP、 H2O2and luminol were added into the immunoprobeturbid liquid respectively, after incubating the sample AFP with the immunoprobemixed solution, the immunoconjugates were formed in the mesopores and the spatialblock increased. The formed immunoconjugates overlapped the surface of CdSe,weaken the CRET system effect of Luminol-H2O2-HRP and CdSe, result in thedecrease of chemiluminiscence signal. As a result, the label-free detection of AFP wasachieved. Under the optimal conditions, linear range for AFP was5.0to100ng mL-1with a detection limit of1.0ng mL-1(3σ).