Study Of Novel Electro-Sensing Materials And Polymeric Optodes Based On Upconverting Nanomaterials

Carrier-based chemical sensors are well developed in theory and always come out with expected experimental results. However, there are still some drawbacks of electrodes such as components leaching and undesirable water-layer formation, as well as biocompatibility issues. For optodes, to minimize the influence of background absorption and autofluorescence when utilizing in biomatters is still essential. In order to improve sensor properties, works have been done as follows:(1) Designed and fabricated optical thin films incorporating upconverting nanomaterials NaYF4:Er, Yb and chromoionophore ETH5418in hydrophobic PVC-DOS polymer matrixes for the first time to measure pH based on the ion-exchange mechanism. The upconverting nanorods capped with oleic acid were prepared via a hydrothermal method. Introduced as a second fluorescent probe, the nanorods could be well dispersed in hydrophobic environment provided by PVC-DOS matrix, without significant influence on binding constant of ionophores or chromoionophores. Heating effect brought by980nm excitation was negligible. The absorption spectra of protonated and deprotonated ETH5418overlap the two emission peaks of upconverting material, respectively, which makes the inert nanorods ion-sensitive. The proposed optodes exhibited excellent sensitivity and reproducibility towards pH, and the measuring range was from6to11. Because of excitation by the980nm laser source, detection in the near-infrared region at656nm, the sensors have been preliminarily demonstrated functional in whole blood measurements with minimized background absorption and sample autofluorescence.(2) Fabricated optodes incorporating NaYF4:Er, Yb upconverting nanorods and chromoionophores for metal ion sensing based on changes in the upconverting luminescence intensity induced from the absorption spectra change of the proton sensitive chromoionophores. Optodes containing nanorods and chromoionophore ETH5418together with different kinds of ionophores exhibited selective and reproducible response towards target ions Na+, K+, Ca2+and Cu2+at pH4.8. In order to achieve measurements at physiological pH (pH7.4), ETH5418was optimized to chromoionophore ETH5294which has a higher pATa. The measuring range of Na+, K+and Cl-lies in physiological range. The sodium, potassium and chloride levels of plasma and whole blood samples were determined simultaneously with proposed optodes. The results were in coincidence with those obtained by ICP-MS and ISEs, providing possibilities for further application in clinical diagnosis. Optodes based on upconverting nanorods and aza-BODIPY for hydrogen peroxide measurements were also fabricated.(3) Fabricated polymeric microspheres optodes via a solvent displacement process. Plasticized poly (vinyl chloride)(PVC) or plasticizer-free poly(n-butyl acrylate)(Poly-BA) along with the optode components and upconverting nanocrystals of two morphologies and sizes were dissolved in an organic solvent miscible with water, then injected into stirred or sonicated aqueous phase containing surfactant. Microspheres based on PVC-DOS matrix doped with hexagonal NaY4:Er, Yb nanorods obtained by magnetic stirring method were preliminarily demonstrated pH sensitive, with response range of8to12.(4) Triblock copolymer polystyrene-block-polybutadiene-block-polystyrene (PS-PB-PS, SBS) and its composites with ionic liquid have been applied for fabricating solid contact ion-selective potentiometric sensors for the first time. Both types of materials form hydrophobic membranes with excellent mechanical properties. The proposed sensors containing ionophore and ion-exchanger exhibited the fast and Nernstian response to the primary ions and good selectivity over various interfering ions. The self-plasticizing property of triblock SBS enables the fabrication of completely solvent-free ion sensors, with different kinds of ionophores, showed Nernstian response to Na+、K+、Ca2+、Cu2+、and Pb2+. Such membranes showed much improved lifetime than the ones containing ionic liquid as plasticizer because the leaching of the ionic liquid has been eliminated. The SBS membrane is more hydrophobic than traditional plasticized poly vinyl chloride membrane, which prevents the formation of the water layer between the metal electrode substrate and the sensing membrane.(5) Intravenous amperometric needle-type enzymatic lactate sensors intended for continuous monitoring were fabricated with a novel nitric oxide (NO) releasing layer to improve device biocompatibility. To create an underlying NO release coating, the sensors with immobilized lactate oxidase were prepared with a thin layer of poly(lactide-co-glycolide)(PLGA) loaded with diazeniumdiolate species that slowly release NO via a proton driven reaction. An outer layer of PurSil (polyurethane/dimethylsiloxane copolymer) limits the flux of lactate to the enzyme. The coating of PLGA and DBHD/N2O2can release NO at a physiologically relevant rate>1×10-10mol min-1cm-2after overnight soaking. With electropolymerized inner layer, the sensors exhibited high selectivity over interferences. Sensors implanted in the veins of rabbits for8h exhibited significantly enhanced biocompatibility for the NO release sensors vs. corresponding controls (without NO release in same animals), with greatly reduced thrombus formation on their surfaces and less noisy signal.