Zhirong Xin

A hierarchical polymer brush coating with dual-function antibacterial capability

Bacterial infections are problematic in many healthcare-associated devices. Antibacterial surfaces integrating the strength of bacteria repellent and bactericidal functions exhibit an encouraging efficacy in tackling this problem. Herein, a hierarchical dual-function antibacterial polymer brush coating that integrates an antifouling bottom layer with a bactericidal top layer is facilely constructed via living photograft polymerization. Excellent resistance to bacterial attachment is correlated with the antifouling components, and good bactericidal activity is afforded by the bactericidal components, and therefore the hierarchical coating shows an excellent long-term antibacterial capability. In addition, due to the presence of the hydrophilic background layer, the hierarchical surface has the greatly improved biocompatibility, as shown by the suppression of platelet adhesion and activation, the inhibition of erythrocyte adhesion and damage, and low toxicity against mammalian cells. The hierarchical polymer brush system provides the basis for the development of long-term antibacterial and biocompatible surfaces.

Capturing red blood cells from the blood by lectin recognition on a glycopolymer-patterned surface

A newly glycopolymer-patterned surface for capturing red blood cells (RBCs) is demonstrated. Our strategy is based on the surface-initiated photopolymerization of 2-acryl-amido-2-methylpropane sulfonic acid (AMPS) on a thermoplastic elastomer, the patterning of poly(d-gluconamidoethyl methacrylate) (PGAMA, glycopolymer) micro-domains on the PAMPS layer with photomask-assisted photolithography, followed by the generation of a phytohemagglutinin (PHA) array on the patterned surface through lectin-carbohydrate recognition. We demonstrate that the bi-component polymer-patterned surface with high lateral resolution is successfully fabricated; the PAMPS layer with patterned glycopolymer domains remains hydrophilic to resist non-specific plasma protein adsorption and cell adhesion; the PHA array on the patterned PGAMA domains induces nearly no platelet adhesion on the patterned surface, but shows high capability for capturing RBCs in the blood, and in addition, the captured RBCs maintain cellular integrity and function. Our work presented herein not only paves a new way for capturing RBCs from the blood, but also establishes a basic principle to capture non-adherent cells in the blood or biological fluid without damage.

Cell-inspired biointerfaces constructed from patterned smart hydrogels for immunoassays in whole blood

Immunoassays have shown great advances in the fields of biomedical diagnosis. However, successful immunoassays in blood plasma or whole blood based on the designed biointerfaces are still rare. Here, a newly cell-inspired biointerface for immunoassays in blood is demonstrated. Inspired by the high resistance to protein and cell adhesion and extraordinary biological recognition of stem cells, the biointerfaces are constructed by patterning smart hydrogels (PNIPAAm-co-PNaAc) on hydrophilic layers (PEG), followed by immobilization of antibodies on the patterned hydrogels. The hierarchical biointerfaces are hydrophilic to resist blood plasma and blood cell adhesion, but exhibit high affinity to the target antigens. As a result, successful immunoassays in blood are achieved. In addition, the detection signal is further enhanced by the manipulation of the phase transition of the smart hydrogels with temperature, and the sensitivity is higher than that of the widely-used poly(acrylic acid)/(polyacrylate) platform. The biointerface is versatile and effective in antibody-antigen recognition, which offers a potential new approach for developing highly sensitive immunoassays in blood.

On properties of graft copolymers of LLDPE and novel fluorine surfactants obtained via reactive extrusion

A series of nonionic fluorin surfactants containing poly(ethylene glycol) (PEG) and their acrylates were synthesized using PEGs of different molecular weight (Mw 600, 1000, 1500, 2000, 4600 g/mol), TDI, acryloyl chloride, and pentadecafluorooctanoic chloride as the main starting materials. Their chemical structures were characterized by means of FTIR and 1H NMR. The surface tension (γ) of the fluorine surfactants were evaluated by drop weight method. The γ value was found to increase with the length of PEG chains. The acrylates were adopted as functionalizing monomers and grafted onto linear low-density polyethylene (LLDPE) through a melt reactive extrusion procedure. The graft degrees of LLDPE were determined by FTIR. Five graft LLDPE samples with grafting degrees of 0.79% (A-I), 0.72% (A-II), 0.68% (A-III), 0.63% (A-IV), and 0.57% (A-V) were prepared. Their surface properties were characterized by measuring contact angles with water and by X-ray Photoelectron Spectroscopy (XPS). Thermal properties of graft LLDPE samples were studied using differential scanning calorimetry. Crystallization rates of graft LLDPEs were faster than that of plain LLDPE at a given crystallization temperature because graft chains could act as nucleating agents. The isothermal crystallization behavior of grafted LLDPE was in accordance with the Avrami model only in the first stage of the process, and deviated from the model by increasing the crystallization time.

Synthesis and characterization of hyperbranched poly(ester-amine) by Michael addition polymerization

Abstract A series of tertiary amine-based hyperbranched poly(amine-ester)s have been synthesized by Michael addition polymerization of trifunctional monomer, TMEA and difunctional monomer, diacylates in chloroform, and the resultant polymers were subsequently treated with mercaptoethenol or 1-dodecanethiol for improving stability in storage. The caption efficiency of mercaptoethanol is much better than that of 1-dodecanthiol. Kinetic study reveals that the thiol group is consumed faster than the acrylate group when the polymerization with feed molar ratio of diacrylate/TMEA = 2/1 was carried out. At initial polymerization, monomer conversion increases fast, but the molecular weights increase slowly and sharp increase of the molecular weight occurs at the final polymerization. The hyperbranched polymers were well characterized by 1H NMR spectra and TD-SEC, and DBs of the polymers obtained are between 0.6 and 0.82, as well as the molar ratios of diacrylate/TMEA in the hyperbranched polymers are between 1.60 and 1.82. The fluorescence efficiency and quantum yields of HypET20, HypHT24 and HypDT24 has the following sequence: HypET20 > HypHT24 > HypDT24.

Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer via covalent immobilization of nonionic sugar-based Gemini surfactants

Gemini surfactants (GS) with sugar-containing head-groups and different alkyl chains were successfully prepared. Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer was grafted with glycidyl methacrylate (GMA) by means of UV-induced graft polymerization, and then the pGMA-grafted film was chemically immobilized with the GS. The surface graft polymerization was confirmed by ATR-FTIR and XPS. The wettability and hemocompatibility of the modified surface were characterized by means of water contact angle, protein adsorption, and platelet adhesion assays. The results showed that amphiphilic surfactant-containing polymer surfaces presented protein-resistant behavior and anti-platelet adhesion after functionalization with GS, GS1 and GS2. Besides, the hemocompatibility of the modified surface deteriorated as the length of hydrophobic chain of GS increased.

Multiple microarrays of non-adherent cells on a single 3D stimuli-responsive binary polymer-brush pattern

We have developed a 3D smart binary polymer-brush pattern on the polymer substrate for inducing multiple cell microarrays aided by a lectin and temperature. The binary polymer-brush pattern composed of poly(N-isopropylacrylamide) (PNIPAM) and poly(d-gluconamidoethyl methacrylate) (PGAMA) brushes is fabricated by combining the photolithography technique with a surface-initiated photo-polymerization (SIPP) method. We demonstrate that well-defined binary polymer-brush patterns with high resolution are fabricated using this facile method. The patterned hierarchical PNIPAM brushes exhibit reversible switching to the adhesion of red blood cells (RBCs) induced by thermo-responsiveness. The PGAMA brush domains resist adhesion of RBCs but bind specifically with concanavalin A (Con A), forming a lectin pattern to capture RBCs in a site-specific manner. Therefore, multiple cell microarrays on a single platform are generated with the aid of Con A and temperature. This novel platform composed of a smart binary polymer-brush pattern is versatile and specific, which opens up pathways to potential applications such as microsensors, biochips and bioassays.

A Biomimetic Surface for Infection-resistance through Assembly of Metal-phenolic Networks

Despite the fact that numerous infection-resistant surfaces have been developed to prevent bacterial colonization and biofilm formation, developing a stable, highly antibacterial and easily produced surface remains a technical challenge. As a crucial structural component of biofilm, extracellular DNA (eDNA) can facilitate initial bacterial adhesion, subsequent development, and final maturation. Inspired by the mechanistic pathways of natural enzymes (deoxyribonuclease), here we report a novel antibacterial surface by employing cerium (Ce(IV)) ion to mimic the DNA-cleavage ability of natural enzymes. In this process, the coordination chemistry of plant polyphenols and metal ions was exploited to create an in situ metal-phenolic film on substrate surfaces. Tannic acid (TA) works as an essential scaffold and Ce(IV) ion acts as both a cross-linker and a destructor of eDNA. The Ce(IV)-TA modified surface exhibited highly enhanced bacteria repellency and biofilm inhibition when compared with those of pristine or Fe(III)-TA modified samples. Moreover, the easily produced coatings showed high stability under physiological conditions and had nontoxicity to cells for prolonged periods of time. This as-prepared DNA-cleavage surface presents versatile and promising performances to combat biomaterial-associated infections.

Hemocompatibility Evaluation of Polyurethane Film with Surface-Grafted Sugar-Based Amphipathic Compounds

Sugar-based amphipathic compounds (BA-CnAG) were successfully prepared. Polyurethane (PU) was grafted with glycidyl methacrylate (GMA) by the means of UV irradiation, and further modified with the BA-CnAG based on the ring opening of the epoxy groups. The surface graft polymerization was confirmed by ATR-FTIR and XPS. Water contact angle, protein adsorption, and platelet adhesion measurements were used to evaluate the hydrophilicity and hemocompatibility of the films. The results demonstrated that amphiphilic surfactant-containing polymer surfaces presented protein-resistant behavior and anti-platelet adhesion after functionalization with BA-CnAG. Besides, the hemocompatibility of the modified surface deteriorated as the length of hydrophobic chain of BA-CnAG increased.

Hierarchical polymer coating for optimizing the antifouling and bactericidal efficacies

Abstract The bacteria-repellent and bactericidal functionalities in a single system are generally need to be carefully optimized in order to obtain the highest antibacterial performance. In this study, the controlled SI-PIMP strategy was developed for creating hierarchical polymer brushes possessing the bacteria-repellent and bactericidal functionalities. To obtain a bactericidal surface with minimal interference to its nonfouling property, optimization studies were conducted by facilely tailoring the surface density of the quaternary ammonium compound moieties through control over the monomer concentration. An optimal hierarchical polymer coating showed potent protein and bacteria repellence as well as certain bactericidal property. The longlasting antibacterial performance was also achieved due to the good balance between the dual functionalities. The tenability of the hierarchical polymer coating is applicable to surface chemistries for biosensors, molecular imaging, and biomedical applications. Graphical abstract