Bifunctional Bioactive Polymer Surfaces with Micrometer and Submicrometer-sized Structure: The Effects of Structure Spacing and Elastic Modulus on Bioactivity

Merging strain-release and copper catalysis: the selective ring-opening cross-coupling of 1,2-oxazetidines with boronic acids

An unprecedented ring-opening cross-coupling of 1,2-oxazetidines with readily available arylboronic acids is achieved for the first time by copper catalysis. Unlike the known electrophilic oxygen reactivity in coupling with organometallic reagents, 1,2-oxazetidines were utilized as formaldimine precursors in this protocol. Remarkable features of this reaction include simple operation, inexpensive catalyst, broad scope and high regioselectivity, delivering a wide array of aminomethylation products. The practicality of this reaction was validated in the one-step downstream transformation of the obtained products into synthetically important molecules and late-stage modification of bioactive acids.

UV-Assisted Li+-Catalyzed Radical Grafting Polymerization of Vinyl Ethers: A New Strategy for Creating Hydrolysis-Resistant and Long-Lived Polymer Brushes as a "Smart" Surface Coating

A facile synthetic route was developed to prepare a surface-grafted brush layer of poly(vinyl ethers) (PVEs) directly by a radical mechanism, with the "naked" Li⁺ acting as a catalyst. Density functional theory calculations suggested that complexation of naked Li⁺ to VEs significantly reduced the highest unoccupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap from 5.08 to 0.68 eV, providing a better prospect for electron transfer. The structure, morphology, and surface properties of grafted polymer layers were characterized using attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and dynamic water contact angle (DCA). Moreover, ellipsometry data indicated that the thickness of the polymer brushes was in the range of 20-60 nm, which corresponds to the grafting densities of 0.65-1.15 chain/nm², and DCA decreased from 84.4 to 45.3°. Most importantly, no hydrolysis was observed for the modified surface after 30 days of exposure to phosphate-buffered saline solution, 0.1 mol/L NaOH(eq) and 0.1 mol/L HCl(eq), demonstrating excellent hydrolysis resistance with long service life. In addition, as a proof of concept, the side hydroxyl groups of grafted PVEs provide active sites for efficient fixation of bioactive molecules, e.g., glycosaminoglycan and serum protein.

Stimulus-Responsive Polyzwitterionic Surfaces Made from Itaconic Acid: Self-Triggered Antimicrobial Activity, Protein Repellency, and Cell Compatibility

A functional monomer carrying a carboxylate and a protected primary ammonium group is synthesized from itaconic acid. When copolymerized with dimethyl acrylamide and 4-methacryloyloxybenzophenone, cross-linkable polyzwitterions are obtained. These are converted to surface-attached polyzwitterion networks by simultaneous UV-triggered C,H insertion reactions. The resulting polyzwitterion-coated substrates were studied by surface plasmon resonance spectroscopy measurements, ζ potential and various biological assays. They were (expectedly) protein repellent, yet at the same time (and unexpectedly) cell-adhesive and antimicrobially active. This was attributed to stimulus-responsiveness of the polyzwitterion (confirmed by the ζ potential measurements), which enables charge adjustment at different pH values. When protonated, the polyzwitterions become amphiphilic polycations and, in this state, kill bacteria upon contact like their parent structures (polymer-based synthetic mimics of antimicrobial peptides, SMAMPs).