In this work, binary mixed polymer brushes based on poly[(2-methyl-2-oxazoline)-random-glycidyl methacrylate] (PMOXA-r-GMA) and poly(glycidyl methacrylate)-block-poly(N-isopropyl acrylamide)-block-polystyrene (PGMA-b-PNIPAM-b-PSt) were used as thermoresponsive coating to control protein adsorption. Firstly, PMOXA-r-GMA was synthesized via cationic ring opening polymerization of 2-methyl-2-oxazoline followed by its copolymerization with glycidyl methacrylate (GMA); PGMA-b-PNIPAM-b-PSt was synthesized by reversible addition–fragmentation chain transfer polymerization of GMA, N-isopropyl acrylamide, and styrene sequentially. Then the mixed brushes were fabricated successfully by spin coating the mixture of PMOXA-r-GMA and PGMA-b-PNIPAM-b-PSt solutions onto silicon or glass substrates followed by an annealing protocol using GMA segments as an anchor. Afterwards, the investigation for adjusting the hydrophobic property of mixed brushes was performed. The results showed that when the environmental temperature is lower than the lower critical solution temperature (LCST) of PNIPAM, the tethered PNIPAM blocks are swollen and could bring the hydrophobic PSt block with optimum molar mass to the surface; when the environmental temperature is higher than the LCST of PNIPAM, the PNIPAM blocks collapse and could bring the hydrophobic block inside the hydrophilic PMOXA grafted polymer layer. Finally, the protein adsorption on mixed polymer brushes was investigated using a fluorescein isothiocyanate-labelled protein assay and ellipsometrys. The results showed that under the optimum molar mass of PSt block, mixed brushes could adsorb proteins in large quantities below the LCST of PNIPAM, and display resistance to protein adsorption above the LCST of PNIPAM.

Polydopamine fluorescent organic nanomaterials present unique physicochemical and biological properties, which have great potential application in bio-imaging and chemical sensors. Here, folic acid (FA) adjustive polydopamine (PDA) fluorescent organic nanoparticles (FA-PDA FONs) were prepared by a facile one-pot self-polymerization strategy using dopamine (DA) and FA as precursors under mild conditions. The as-prepared FA-PDA FONs had an average size of 1.9 ± 0.3 nm in diameter with great aqueous dispersibility, and the FA-PDA FONs solution exhibit intense blue fluorescence under 365 nm UV lamp, and the quantum yield is ~8.27%. The FA-PDA FONs could be stable in a relatively wide pH range and high ionic strength salt solution, and the fluorescence intensities are constant. More importantly, here we developed a method for rapidly selective and sensitive detection of mercury ions (Hg²⁺) within 10 s using FA-PDA FONs based probe, the fluorescence intensities of FA-PDA FONs presented a great linear relationship to Hg²⁺ concentration, the linear range and limit of detection (LOD) were 0–18 µM and 0.18 µM, respectively. Furthermore, the feasibility of the developed Hg²⁺ sensor was verified by determination of Hg²⁺ in mineral water and tap water samples with satisfactory results.

In this work, the comb-like poly(2-methyl-2-oxazoline) copolymer, poly(2-aminoethyl methacrylate-random-poly(2-methyl-2-oxazoline) (PMOXA-r-AEMA, PMA) is synthesized, and the CuSO₄/H₂O₂-triggered dopamine/PMA co-deposition process is investigated. Ellipsometry, water contact angle (WCA), and X-ray photoelectron spectroscopy (XPS) are used to characterize the thickness, hydrophilicity, and surface composition of PMA-based coatings. PMA is facilely anchored to substrates within 60 min with the assistance of dopamine/polydopamine triggered by CuSO₄/H₂O₂, and the coating thickness can achieve about 13 nm. Anti-protein adsorption and anti-blood platelet adhesion measurements are also studied to verify their antifouling properties. The adsorption capacity of FITC-BSA can be reduced to 5% of the original surface, and PMA-based coatings present excellent protein-resistant properties (∼95% reduction relative to gold surface) according to surface plasmon resonance (SPR) measurement, and it can resist adhesion of almost all blood platelets. Moreover, it is applied to a capillary inner wall for surface modification. An alkaline protein mixture and egg white proteins are successfully separated, and present excellent stability. The relative standard deviation (RSD) of migration time is lower than 0.71%. The practicability of this promising PMA-based coatings with this preparation strategy can be used for further proteomics analysis.

A fast, facile and selective fluorescence detection method for Bi ³⁺ was developed based on poly(tannic acid) nanoparticles.