Gold nanoparticles stabilized by thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM-AuNPs) were prepared by surface grafting of thiol-terminated PNIPAM onto citrate-stabilized AuNPs. The color change of the PNIPAM-AuNPs solution from red to blue-purple without precipitation when the solution was heated to 40 °C, above the lower critical solution temperature (LCST) of PNIPAM, indicated the thermoresponsive property of the synthesized AuNPs. PNIPAM-AuNPs were used to detect proteins by chemical nose approach based on fluorescence quenching of fluorophore by AuNPs. An array-based sensing platform for detection of six proteins, namely bovine serum albumin, lysozyme, fibrinogen, concanavalin A, hemoglobin, holo-transferrin human can be successfully developed from the PNIPAM-AuNPs having different molecular weights (4 and 8 kDa) and conformation (varied heat treatment from 25 to 40 °C) in combination with a tricationic branched phenylene-ethynylene fluorophore. From principal component analysis (PCA) followed by linear discriminant analysis (LDA), 100% accuracy of protein classification using a leave-one-out (LOO) approach can be achieved by using only two types of PNIPAM-AuNPs.

In this study, we have fabricated robust patterned surfaces that contain biocompatible and antifouling stripes, which cause microorganisms to consolidate into bare silicon spaces. Copolymers of methacryloyloxyethyl phosphorylcholine (MPC) and a methacrylate-substituted dihydrolipoic acid (DHLA) were spin-coated onto silicon substrates. The MPC units contributed biocompatibility and antifouling properties, while the DHLA units enabled crosslinking and the formation of robust thin films. Photolithography enabled the formation of 200 μm wide poly(MPC-DHLA) stripped patterns that were characterized using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and rhodamine 6G staining. Regardless of the spacing between the poly(MPC-DHLA) stripes (10, 50, or 100 μm) Escherichia coli (E. coli) rapidly adhered to the bare silicon gaps that lacked the copolymer, confirming the antifouling nature of MPC. Overall, this work provides a surface modification strategy to generate alternating bio-fouling and non-fouling surface structures that are potentially applicable for researchers studying cell biology, drug screening, and biosensor technology.

No abstract

Novel constrained Schiff-base ligands (inden) were developed based on the well-known salen ligands. Chromium complexes supported by the constrained inden ligands were successfully synthesized and used as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO 2 ). The catalyst having tert-butyl ( t Bu) groups as substituents in combination with tetrabutylammonium bromide (TBAB) as a cocatalyst exhibited very high catalytic activity with a turnover frequency of up to 14800 h −1 for the conversion of CO 2 and propylene oxide into propylene carbonate exclusively at 100 °C and 300 psi of CO 2 under solvent-free conditions. The catalyst was found to be highly active for various epoxide substrates to produce terminal cyclic carbonates in 100% selectivity.

Patterned poly(acrylic acid) (PAA) brushes was successfully generated via photolithography and surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid as verified by water contact angle measurements and FT-IR analysis. The carboxyl groups of PAA brushes can act as reducing moieties for in situ synthesis of gold nanoparticles (AuNPs), without the use of additional reducing agent. The formation of AuNPs was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. The glass surface-modified by PAA brushes and immobilized with AuNPs (AuNPs-PAA) can be used as a substrate for SALDI-MS analysis, which is capable of detecting both small peptides having m/z ≤ 600 (glutathione) and large peptides having m/z ≥ 1000 (bradykinin, ICNKQDCPILE) without the interference from matrix signal suggesting that AuNPs were stably trapped within the PAA brushes and the carboxyl groups of PAA can serve as internal proton source. By employing AuNPs as the capture probe, the AuNPs-PAA substrate can selectively identify thiol-containing peptides from the peptide mixtures with LOD as low as 0.1 and 0.05 nM for glutathione and ICNKQDCPILE, respectively. An ability to selectively detect ICNKQDCPILE in a diluted human serum is also demonstrated. The patterned format together with its high sensitivity and selectivity render this newly developed substrate a potential platform for high-throughput analysis of other biomarkers, especially those with low molecular weight in complex biological samples.

Hospital‐acquired infections are often caused by bacterial biofilms on medical devices. To prevent biofilm formation, herein, a universal coating of an antifouling polymer that inhibits the initial adhesion of bacteria is developed. This copolymer is made of methacryloyloxyethyl phosphorylcholine (MPC) and a methacrylate‐substituted dihydrolipoic acid (DHLA) (poly(MPC‐DHLA)). The MPC units provide the antifouling property, while the DHLA units offer cross‐linkable sites via thiol‐ene reactions to form the stable coated copolymer film. Without the requirement for covalent surface grafting, the poly(MPC‐DHLA) coating on various biomedically relevant substrates is investigated, where X‐ray photoelectron spectroscopy, water contact angle measurements, atomic force microscopy, and ellipsometry are used to confirm the success of the surface coating. Moreover, to mimic an actual clinical use, the copolymer coating is applied on a titanium dental substrate and the ability to inhibit biofilm formation by Staphylococcus aureus is quantified and visualized by crystal violet staining and scanning electron microscopy, respectively. As compared with the bare substrate, an effective reduction in bacterial adhesion and suppression of the subsequent biofilm formation is observed on the copolymer‐modified substrate. These features are maintained for up to 7 d indicating the durability as well as universal applicability of this coating approach.

No abstract

In article number 1900286 by Voravee P. Hoven and co‐workers, a stable, biocompatible zwitterionic poly(MPC‐DHLA) film is coated on various biomedically relevant substrates. A universal substrate‐independent antifouling coating is successfully achieved and confirmed by X‐ray photoelectron spectroscopy, water contact angle measurements, atomic force microscopy, and ellipsometry. The poly(MPC‐DHLA) coating is also applied on titanium dental substrate. Its antibiofilm activity is maintained for up to 7 days.