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Two kinds of hydrophilic conjugated polymer, poly[9,9-bis((6-N,N,N-trimethylammonium)hexyl)fluorine-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole] (PFBD) with cationic groups and poly[9,9-bis(4′-sulfonatobutyl)fluorine-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)] sodium salt (PFSBT) with anionic groups, were prepared by Suzuki method. The as-prepared conjugated polymers were formed nanoparticles (NPs) with the diameter of ~20 nm in water. Under a 488 nm laser excitation, the PFBD shows an emission peak at 560 nm and with the quantum yield of ~26%, while the PFSBT shows an emission peak at 575 nm with the quantum yield of ~4%. We investigated the cellular uptake and cell viability of two conjugated polymer NPs (CPNPs) on human gastric adenocarcinoma (SGC-7901). Both of CPNPs show low cytotoxicity by MTT assay, even at the concentration of 40 ppm. Flow cytometers studies indicate that the fluorescence intensity of PFBD NPs is stronger than that of PFSBT NPs. These results would provide a basic experiment evidence in the fluorescence imaging field.

The authors describe a chemical sensor for dopamine (DA). It is based on the use of three-dimensional graphene oxide (3D rGO) loaded with varying amounts of AuPd bimetallic nanoparticles (3D rGO/AuPd NPs). The 3D rGO acts as an effective substrate providing a large surface area and allowing fast electron transfer. The interaction between 3D rGO and surface AuPd NPs increases the activity of the sensing material. These composites were fabricated as the active layer on an indium tin oxide for DA determination. The electrode showed the best performance at a working potential of 0.25 V (vs. the saturated calomel reference electrode) and a scan rate of 100 mVs−1. The best electrode exhibits good sensitivity (4670 μA·mM−1·cm−2), a wide linear response (0.5 μM to 135 μM), and a low detection limit (0.2 μM). It is also selective, easily reproducible, and stable. It was applied to the determination of DA in spiked human serum and in clinical DA hydrochloride injections. The excellent performance of this electrode is attributed to the efficient electron transfer and large specific surface area of 3D rGO and to the high electrocatalytic activity of AuPd NPs due to the synergistic effect between the 3D rGO substrate and the AuPd alloy NPs.

A new conjugated polymer, poly[{2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylphenylene)}-alt-co-{2,5-bis(N,N′-diphenylamino)-1,4-phenylene}] (DB-CN-PPV), with strong UV absorption and high fluorescence in red wavelength region, is self-assembled into nanoparticles (polymer dots, Pdots) in aqueous solution upon rapid mixing of the organic solution with water. Different-sized Pdots were obtained by varying the organic solvent percent in the mixture solution and further characterized by dynamic light scattering and transmission electron microscopy. Spectroscopic measurements indicate that the DB-CN-PPV Pdots exhibit a bright red-emitting and a quantum yield of ~27 %. Single-particle imaging and analyses indicate the brightness of DB-CN-PPV Pdots under 405 nm excitation is four times brighter than that of the well-known inorganic quantum dot probes, Qdot655, under same excitation light. The successful bioconjugation and cellular imaging suggest DB-CN-PPV Pdots have potential application for biological fluorescence imaging.