Cerium-titanium-based Nanomaterials For Telomerase And Metal Ion Detection

Ceriun-titanium-based nanomaterials have received extensive attention in the fields of biosensing and catalytic oxidation due to a large number of binding defects on their surfaces and the conversion of two oxidation states.In addition,the excellent biocompatibility and photochemical stability of cerium-titanium-based nanomaterials have great application potential in electrochemical and spectral detection In this thesis,a series of new preparation methods of cerium-titanium-based nanomaterials were proposed and successfully applied to the detection of telomerase and metal ions.The main research contents are as follows:1.A new method for preparing porous cerium oxide-titanium oxide nanorods(CeO2-TiO2NRs)was proposed,and for the first time applied the interaction between Janus DNA structure(one side are bases and the other side are phosphate groups)and nanomaterials to construct an electrochemical sensor for the detection of telomerase activity.When active telomerase was present in the system,the primer DNA of telomerase can continuously extend the single strand in the substrate solution of deoxynucleotide triphosphates(dNTPs),and the extended DNA can be combined with hairpin DNA containing complementary bases to form double strands.Exonuclease ?(Exo ?)recognized the double-stranded DNA to initiate cyclic anplification,releasing a large number of adenine-rich single-stranded DNA(polyA-DNA),which were modified on the gold electrode(AuE)through the interaction of adenine and gold.At the same time,the phosphate group of polyA-DNA further adsorbed CeO2-TiO2NRs on the AuE to make a sandwich structured CeO2-TiO2NRs/DNA/AuE sensor.The electrochemical signals of[Fe(CN)6]3-/4-were output based on the strong electrostatic repulsion to achieve label-free detection of telomerase activity in cancer cell extracts.2.A method for preparing cerium-based metal organic framework(CeO2NRs-MOF))based on sacrificial template method was proposed and used to construct a colorimetric method for highly sensitive detection of hexavalent chromium.Cerium dioxide nanorods(CeO2NRs)with nanozyme activity were used as templates to provide cerium ions as the metal center.After the organic ligand terephthalic acid was added,nucleation growth of the metal-organic framework on the surface of CeO2NRs was initiated.Finally,the rod-like morphology of CeO2NRs was retained.The prepared CeO2NRs-MOF has stronger oxidase activity than other Ce-based nanomaterials and can oxidize the substrate 3,3',5,5'-tetramethylbenzidine(TMB)-Meanwhile it can selectively adsorb hexavalent chromium ions(Cr(VI))and reduce it to trivalent state with lower toxicity.Cr(VI)and TMB can form a redox cycle by replacing the common hydrogen peroxide.As the concentration of Cr(VI)increases,more TMB is oxidized,and the blue color gradually deepens,and the UV-vis absorption peak at 650 nm increases linearly.The colorimetric platform is efficiently and quickly for the detection of Cr(VI)in environmental water samples.3.A new method of turn-off mode to detect the concentration of Cu2+ was proposed based on the titanium-based metal organic frameworks(Ti-MOF)has the oxidase-like activity under ultraviolet light and the inhibitory effect of Cu2+ on the activity of Ti-MOF.Under light excitation,Ti-MOF prepared by tetrabuty1 titanate providing titanium ions as metal center and 2-aminoterephthalic acid as organic ligand undergoes the electron-hole separation,promoting the reduction of tetrovalent titanium(Ti4+)and the generation of reactive oxygen species,which can catalyze the oxidation of TMB.The comparison experiments show that the mechanism of Cu2+promoting photoactive nanozyme activity of Cu2+doped Ti-MOF(Cu2+-Ti-MOF)is different from the undoped Ti-MOF.When Cu2+is added into the Ti-MOF/TMB mixture,which can become an "electron trap" and capture photo-generated electrons to inhibit the color development of TMB.With the increase of the concentration of Cu2+,the color of TMB gradually changes from dark blue to colorless,and the UV-vis characteristic absorption peak of oxidation product at 652 nm weakens linearly.Based on the Ti-MOF/TMB lighting system,a colorimetric platform for Cu2+ detection was constructed,which has a broad prospect in practical analysis.