The Study Of The Colorimetric Immunoassay Based On Transition-metal-substituted Polyoxometalates

The key point of cancer treatment is the accurate diagnosis at early stages.Traditional diagnostic methods in early diagnosis of cancer are unsensitive, time-consuming and expensive. So it is not available for large numbers of people. Dopamine(DA) is a kind of neurotransmitter, which plays an important role in regulating effect in body. Therefore, the rapid and high sensitive detection of tumor cells and dopamine is of great significance. The colorimetric immunoassay of biological enzymes is the important detection method, but the enzymes often lose their activities when denatured. The development and research of mimic enzymes have become a new research hot spot.Polyoxometalates(POMs) are discrete anionic metal-oxygen clusters which exhibit remarkably rich redox properties and have important applications in the O2, H2O2 or other oxidants facilitating the oxidation of organic substrates. Among them, The peroxidase-like activities of the active H2O2 have become a research hot spot in the domain of catalytic oxidation based on POMs. The redox properties of POMs can be adjusted by changing their compositions and structures, so the design and synthesis of peroxidase-like mimic enzyme based on POMs are of theoretical significance. At the same time, the fast and effective detection of H2O2 concentration is important in food detection, clinical and environmental analysis. Therefore, we synthesized a series of transition metal monosubstituted, disubstituted and trisubstituted POMs, and studied the catalytic activities in facilitating the oxidation of organic substrate. Moreover, we established the relationship between the catalytic activities and performances of POMs, and constructed a rapid detection method for tumor cells and dopamine. The studies were as follows:1. Preparation of monosubstituted polyoxotungstate: K5[PW11MO39(H2O)](PW11M, M =Co2+, Ni2+, Cu2+, Mn2+), and were characterized on structure and redox properties by IR、UV、CV、XRD et al. We studied the catalytic activities of PW11 M in facilitating the oxidation of substrate TMB, and explored their peroxidase-like activities. Furthermore,we constructed the relationship between the catalytic activities and their redox properties.The results showed that PW11 Cu presented the best activity and was used to detect concentration of H2O2.The linear range was 2.20×10-5 ~ 8.96×10-7 mol/L.2. Preparation of FA functionalized FA-PW11 Cu O39(H2O)(FA-PW11Cu) composite, and FA-PW11 Cu nanoparticles were characterized by IR、UV、CV、XRD、TEM、EDAX etal. We found that the nanoparticles were Keggin structures which the partical size was 20-30 nm. In the detection of tumor cells in vitro, the results showed the nanoparticles can rapidly target tumor cells to detect them under the effect of FA, which is an amimic peroxidase can substitut biological enzymes.3. Preparation of monosubstituted, disubstituted and trisubstituted tungstosilicate POMs:[Si W11M(H2O)O39]n-(Si W11M) 、 [(Fe OH2)2Si W10O36]n-(Si W10M2) and [Si W9O37{M(H2O)}3]n-(Si W9M3, M = Co2+, Fe3+, Cu2+, Mn2+) were characterized. Westudied the relationship between the redox properties of POMs and the species of substituted metal ions as well as the number of the substituted metal ions. Moreover, we constructed the relationship between the catalytic activities of oxidizing H2O2 and their redox properties. The results showed that Si W9Co3 presented the best activity and was used to detect the concentration of DA. The linear range was 1.08×10-4~ 5.38×10-6mol/L.