抄録
Upconversion (UC) phosphors are expected to be used as new photonic probes for biologically-benign systems. To apply the UC phosphors for the bio-photonic devices, chemical durability, dispersion stability in physiological saline and specific interaction with a target substance must be introduced to the UC nanophosphors. We modified the surface of Er-doped Y2O3: nanoparticles, one of the UC phosphors, using the bi-layer of poly(acrylic acid) (PAAc) and biotinyl-poly(ethylene glycol)-block-poly[2-(N,N-dimethyl amino)ethyl methacrylate] (biotinyl-PEG-b-PAMA), which has a biofunctional block possessing biotinyl group at PEG chain end. The bi-layer modification was confirmed by FT-IR and zeta potential analyses. The amount of the polymers on the surface was estimated by a TGA. The particles modified with the hi-layered polymers did not erode in highly acidic solution, while those without modification completely did at a pH=6.4. The modified particles also could be dispersed in a physiological salt solution for more than 20 h. Due to the specific interaction between biotin and avidin, plate assay experiments on plates with avidin and bovine serum albumin (BSA) resulted in a specific binding of the modified particles only with the plate with avidin.
