Shunjie Yan

Fabricating a Cycloolefin Polymer Immunoassay Platform with a Dual-Function Polymer Brush via a Surface-Initiated Photoiniferter-Mediated Polymerization Strategy

The development of technologies for a biomedical detection platform is critical to meet the global challenges of various disease diagnoses. In this study, an inert cycloolefin polymer (COP) support was modified with two-layer polymer brushes possessing dual functions, i.e., a low fouling poly[poly(ethylene glycol) methacrylate] [p(PEGMA)] bottom layer and a poly(acrylic acid) (PAA) upper layer for antibody loading, via a surface-initiated photoiniferter-mediated polymerization strategy for fluorescence-based immunoassay. It was demonstrated through a confocal laser scanner that, for the as-prepared COP-g-PEG-b-PAA-IgG supports, nonspecific protein adsorption was suppressed, and the resistance to nonspecific protein interference on antigen recognition was significantly improved, relative to the COP-g-PAA-IgG references. This strategy for surface modification of a polymeric platform is also applicable to the fabrication of other biosensors.

Nuclease-Functionalized Poly(Styrene-b-isobutylene-b-styrene) Surface with Anti-Infection and Tissue Integration Bifunctions

Hydrophobic thermoplastic elastomers, e.g., poly(styrene-b-isobutylene-b-styrene) (SIBS), have found various in vivo biomedical applications. It has long been recognized that biomaterials can be adversely affected by bacterial contamination and clinical infection. However, inhibiting bacterial colonization while simultaneously preserving or enhancing tissue-cell/material interactions is a great challenge. Herein, SIBS substrates were functionalized with nucleases under mild conditions, through polycarboxylate grafts as intermediate. It was demonstrated that the nuclease-modified SIBS could effectively prevent bacterial adhesion and biofilm formation. Cell adhesion assays confirmed that nuclease coatings generally had no negative effects on L929 cell adhesion, compared with the virgin SIBS reference. Therefore, the as-reported nuclease coating may present a promising approach to inhibit bacterial infection, while preserving tissue-cell integration on polymeric biomaterials.

Facile Fabrication of Lubricant-Infused Wrinkling Surface for Preventing Thrombus Formation and Infection

Despite the advanced modern biotechniques, thrombosis and bacterial infection of biomedical devices remain common complications that are associated with morbidity and mortality. Most antifouling surfaces are in solid form and cannot simultaneously fulfill the requirements for antithrombosis and antibacterial efficacy. In this work, we present a facile strategy to fabricate a slippery surface. This surface is created by combining photografting polymerization with osmotically driven wrinkling that can generate a coarse morphology, and followed by infusing with fluorocarbon liquid. The lubricant-infused wrinkling slippery surface can greatly prevent protein attachment, reduce platelet adhesion, and suppress thrombus formation in vitro. Furthermore, E. coli and S. aureus attachment on the slippery surfaces is reduced by ∼98.8% and ∼96.9% after 24 h incubation, relative to poly(styrene-b-isobutylene-b-styrene) (SIBS) references. This slippery surface is biocompatible and has no toxicity to L929 cells. This surface-coating strategy that effectively reduces thrombosis and the incidence of infection will greatly decrease healthcare costs.

Nonleaching Bacteria-Responsive Antibacterial Surface Based on a Unique Hierarchical Architecture

Bacteria-responsive surfaces popularly exert their smart antibacterial activities by bacteria-triggered delivery of antibacterial agents; however, the antibacterial agents should be additionally reloaded for the renewal of these surfaces. Herein, a reversible, nonleaching bacteria-responsive antibacterial surface is prepared by taking advantage of a hierarchical polymer brush architecture. In this hierarchical surface, a pH-responsive poly(methacrylic acid) (PMAA) outer layer serves as an actuator modulating the surface behavior on demand, while antimicrobial peptides (AMP) are covalently immobilized on the inner layer. The PMAA hydration layer renders the hierarchical surface resistant to initial bacterial attachment and biocompatible under physiological conditions. When bacteria colonize the surface, the bacteria-triggered acidification allows the outermost PMAA chains to collapse, therefore exposing the underlying bactericidal AMP to on-demand kill bacteria. In addition, the dead bacteria can be released once the PMAA chains resume their hydrophilicity because of the environmental pH increase. The functionality of the nonleaching surface is reversible without additional reloading of the antibacterial agents. This approach provides a new methodology for the development of smart surfaces in a variety of practical biomedical applications.

Infection-resistant styrenic thermoplastic elastomers that can switch from bactericidal capability to anti-adhesion

Styrenic thermoplastic elastomers (STPEs), particularly for poly(styrene-b-isobutylene-b-styrene) (SIBS), have aroused great interest in the indwelling and implant applications. However, the biomaterial-associated infection is a great challenge for these hydrophobic elastomers. Here, benzyl chloride (BnCl) groups are initially introduced into the SIBS backbone via Friedel-Crafts chemistry, followed by reaction with methyl 3-(dimethylamino) propionate (MAP) to obtain a cationic carboxybetaine ester-modified elastomer. The as-prepared elastomer is able to kill bacteria efficiently, while upon the hydrolysis of carboxybetaine esters into zwitterionic groups, the resultant surface has antifouling performances against proteins, platelets, erythrocytes, and bacteria. This STPE that switches from bactericidal efficacy during storage to the antifouling property in service has great potential in biomedical applications, and is generally applicable to the other styrene-based polymers.

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.

Effect of polyethylene glycol on the antibacterial properties of polyurethane/carbon nanotube electrospun nanofibers

The discovery of antibacterial functions for carbon nanotubes (CNT) has triggered great interest because of the excellent antibacterial properties of CNT. However, there are two obstacles, i.e., cell toxicity and CNT aggregation in a polymer matrix, which greatly limit the antibacterial application of CNT in medical devices. In this study, a facile, cost-effective, time-saving and environmentally friendly approach was proposed to impart the antibacterial property to thermoplastic polyurethane (TPU) electrospun nanofibers with CNT. The ultrasonication technique was explored to in situ anchor the CNT onto the TPU electrospun nanofibers to achieve the bactericidal property. This effectively circumvented the aggregation of CNT when the TPU/CNT electrospun nanofibers were prepared. In addition, the anchor preparation was efficient taking only 10 min to complete and it was also non-toxic because the green solvent ethanol was used as the dispersion solvent. PEG was chemically grafted onto the TPU (TPU-g-PEG) electrospun nanofibers through UV photo-graft polymerization. Although CNT exhibit a good bactericidal property, they could be toxic to human cells. Incorporation of PEG could not only effectively reduce the toxicity of CNT to the human cells but also decrease bacterial attachment. The TPU-g-PEG/CNT nanofibers exhibited excellent hemocompatibility, including suppression of red blood cell adhesion, and lower hemolysis ratios. Importantly, the as-prepared nanofibers had better antibacterial properties due to the bacterial resistance of the grafted PEG and the bactericidal effect of CNT. Our facile approach has significant potential for the infection-resistant wound dressing.

Temperature-Responsive Hierarchical Polymer Brushes Switching from Bactericidal to Cell Repellency

Unlike conventional poly(N-isopropylacrylamide) (PNIPAM)-based surfaces switching from bactericidal activity to bacterial repellency upon decreasing temperature, we developed a hierarchical polymer architecture, which could maintain bactericidal activities at room temperature while presenting bacterial repellency at physiological temperature. In this architecture, a thermoresponsive bactericidal upper layer consisting of PNIPAM-based copolymer and vancomycin (Van) moieties was built on an antifouling poly(sulfobetaine methacrylate) (PSBMA) bottom layer via sequential surface-initiated photoiniferter-mediated polymerization. At room temperature below the lower critical solution temperature (LCST), the PNIPAM-based upper layer was stretchable, facilitating contact killing of bacteria by Van. At physiological temperature (above the LCST), the PNIPAM-based layer collapsed, thus leading to the burial of Van and exposure of bottom PSBMA brushes, finally displaying notable performances in bacterial inhibition, dead bacteria detachment, and biocompatibility, simultaneously. Our strategy provides a novel pathway in the rational design of temperature-sensitive switchable surfaces, which shows great advantages in the real-world infection-resistant applications.

Fouling-resistant behavior of liquid-infused porous slippery surfaces

Marine economy is seriously affected by marine biofouling, which has plagued people for thousands of years. Although various strategies have been developed to protect artificial surfaces against marine biofouling, cost-effective biofouling-resistant coating is still a goal in pursue. Herein, a cost-effective liquid-infused porous slippery surface (LIPSS) was facilely prepared by using poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer to form microsphere surfaces, followed by infusing fluorocarbon lubricants into the porous structure. The as-prepared slippery surfaces were characterized by static water contact angle, sliding velocity and sliding angle analysis. We also investigated the adhesion behavior of Escherichia coli (E. coli) and limnetic algae on different surfaces. It is confirmed that the slippery surfaces have better anti-biofouling properties than the porous SEBS reference. This cost-effective approach is feasible and easily produced, and may potentially be used as fouling-resistant surfaces.

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.