Dedai Lu

Mussel-Inspired Thermoresponsive Polypeptide–Pluronic Copolymers for Versatile Surgical Adhesives and Hemostasis

Inspired by marine mussel adhesive proteins, polymers with catechol side groups have been extensively explored in industrial and academic research. Here, Pluronic L-31 alcoholate ions were used as the initiator to prepare a series of polypeptide-Pluronic-polypeptide triblock copolymers via ring-opening polymerization of l-DOPA-N-carboxyanhydride (DOPA-NCA), l-arginine-NCA (Arg-NCA), l-cysteine-NCA (Cys-NCA), and ε-N-acryloyl lysine-NCA (Ac-Lys-NCA). These copolymers demonstrated good biodegradability, biocompatibility, and thermoresponsive properties. Adhesion tests using porcine skin and bone as adherends demonstrated lap-shear adhesion strengths up to 106 kPa and tensile adhesion strengths up to 675 kPa. The antibleeding activity and tissue adhesive ability were evaluated using a rat model. These polypeptide-Pluronic copolymer glues showed superior hemostatic properties and superior effects in wound healing and osteotomy gaps. Complete healing of skin incisions and remodeling of osteotomy gaps were observed in all rats after 14 and 60 days, respectively. These copolymers have potential uses as tissue adhesives, antibleeding, and tissue engineering materials.

In situ formation of gold nanoparticles on magnetic halloysite nanotubes via polydopamine chemistry for highly effective and recyclable catalysis

In this study, we present a simple and green approach to fabricate a magnetic halloysite nanotube (MHNT) supported Au nanoparticle (NP) composite (MHNTs–PDA–Au) with a polydopamine functional coating for highly effective and recyclable catalysis. The fabrication of MHNTs–PDA–Au involves decoration of Fe3O4 NPs on HNTs via a one-step co-precipitation method, deposition of a polydopamine layer on the MHNTs and subsequent in situ reduction of Au NPs via polydopamine chemistry. All the processes are simple and eco-friendly without use of additional toxic reagents and complicated treatment. The obtained MHNTs–PDA–Au composite exhibits excellent and versatile catalytic activity toward the reduction of various nitrobenzene derivatives and methylene blue dye when only trace amounts of Au catalyst are used. In addition, the catalytic system can be easily recycled for several cycles based on its good magnetic properties. The synergistic combination of MHNTs, polydopamine coating and metal NPs offers a versatile platform for design of natural HNT based composite materials and will expand the applications of HNTs in heterogeneous catalysis, water purification and green chemistry.

The synthesis and tissue adhesiveness of temperature-sensitive hyperbranched poly(amino acid)s with functional side groups

The incorporation of L-3,4-dihydroxyphenylalanine (L-DOPA) residues in mussel-like biomimetic copolymers has drawn great attention due to their adhesive properties. In this work, a series of temperature-sensitive and hyperbranched poly(amino acid)s containing different functional side groups (catechol, guanidyl, mercapto and double bond) were designed and synthesized by the ring-opening polymerization of N-carboxy-α-amino acid anhydride (NCA), using a temperature-sensitive and multi-hydroxyl end pluronic L-31 as the initiator in this process. The tissue adhesive properties of these copolymers were evaluated by tensile strength tests on wet pork skin. We found that the topological structure, side groups of copolymers, adhesive temperature and cure time had influence on the wet adhesive strength, especially side groups. While only L-DOPA was incorporated into copolymeric chains, the wet adhesive strength was about 106 kPa. With guanidyl, mercapto and double bonds incorporated into copolymeric chains, an obvious increase in the wet adhesive strength was observed. Additionally, the wet adhesive strength improved by about 20 kPa at body temperature (37 °C) as compared to that at room temperature (25 °C). Meanwhile, we found that it has good biocompatibility and degradability through its cytotoxicity and degradation tests.

Fluorophore-functionalized graphene oxide with application in cell imaging

In this work, we fabricated a novel triphenylamine-derivative (DNDT)-modified nanographene oxide by following a simple gram-scale method. The product showed interesting optical properties and good potential for use in bioimaging applications. This fluorescent carbon material could be readily internalized by HepG2 cells and was clearly visualized to accumulate mainly in the nucleus.

Intriguingly tuning the fluorescence of AIEgen using responsive polyelectrolyte microspheres

In this study, we present a practical approach to tune the fluorescence of AIEgen (the luminogens exhibiting AIE attributes) based on counterion-sensitive polyelectrolyte microspheres. The tunable fluorescence is induced by counterion-driven interactions in polyelectrolyte microspheres by a simple exchange of the counterions. The effects of different types of opposite counterions on the fluorescent properties of a new polyelectrolyte tetraphenylethene-graft-poly[2-(methacryloyloxy)-ethyltrimethylammonium chloride] (TPE–PMETAC), which was synthesized by Atom Transfer Radical Polymerization (ATRP) using a TPE derivative containing four arms as an initiator, were systematically investigated. For cationic microspheres with quaternary ammonium groups, the fluorescence intensity progressively increased according to the counterion series Cl− < ClO4− < PF6− < TFSI−, which is in accord with the ability of exchanged hydrophilic Cl− by hydrophobic anions in the order of ClO4− < PF6− < TFSI−. The mechanism of tuning fluorescence was determined by dynamic light scattering (DLS), zeta-potentials and scanning electron microscopy (SEM). We proved that the size of the microspheres and electrostatic repulsive forces between the microspheres were decreased by the addition of counterions due to the hydrophobic-induced collapse of the surfaces of the microspheres. As a result, the obvious increase in the fluorescence of AIEgen was obtained based on the aggregation of microspheres.

A direct crossed polymerization of triphenylamines and cyclohexanones via CC bond formation: the method and its bioimaging application

The effective polymerization process is very desirable in the field of macromolecule science. In this study, we present a facile synthetic method via aldol addition and condensation (AAC) that leads to the formation of fluorescent linear and branched polymers by cross coupling triphenylamines (TPA) and cyclohexanones (CYC) via CC bond formation. The methodology has the advantage of easy operations, mild reaction conditions, and high yield. Via the analysis of NMR, FT-IR, GPC, PL, UV, SEM, and theoretical calculation, the structure, physical properties, and optical behaviors of both polymers were well-characterized. The understanding of cell transplantation, migration, division, fusion, and lysis is a very challenging task. In this study, the linear polymer (LP) exhibits excellent biocompatibility and low cytotoxicity, which can be readily internalized by living cells in a noninvasive manner. The images of MPC5 cells indicate that LP can be a promising emissive fluorescence probe for bioimaging application.