Surface modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) elastomer via UV-induced graft polymerization of N-vinyl pyrrolidone

ADVANCES IN TECHNIQUES AND APPLICATIONS OF RUBBER SURFACE GRAFTING MODIFICATION

To meet the requirement in the application of medical devices, composites, biomaterials, corrosion resistance, and selective adsorptions, rubber surface modification is usually indispensable. Grafting treatment is one of most significate treatment methods. In this paper, we focus on rubber surface grafting modification, including grafting techniques and applications. Different grafting methods—including monomer grafting polymerization and coupling reaction—are covered and compared briefly. The related applications of surface grafting modification techniques, such as improving compatibility of waste rubber as fillers, hydrophobicity and lipophilicity of sponge rubber for oil–water separation, biocompatibility of rubber in the medical field, and forming surface patterns, are demonstrated in detail. The new research directions of surface grafting techniques as well as main challenges in application are also discussed.

Bottlebrush-like highly efficient antibacterial coating constructed using α-helical peptide dendritic polymers on the poly(styrene-b-(ethylene-co-butylene)-b-styrene) surface

Infectious diseases induced by pathogenic bacteria are the major causes for the failure of medical implants. Meanwhile, the drug-resistance is steadily developed because of the large and even inappropriate use of antibiotics. Therefore, the development of antibacterial coating with non-antibiotic-based agents on the surfaces of medical implants and devices has been an urgent need. Herein, we propose a bottlebrush-like antibacterial coating on a poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer surface by UV-induced graft polymerization of poly(ethylene glycol) (PEG) acrylate terminated poly(lysine dendrimer). This PEG-conjugated antibacterial polymer possessed a substructure of α-helical backbone and cation dendrimer side chains stretching in the radial directions of the helix. The introduction of lysine peptide dendrimers endowed the prepared antibacterial polymer with precisely controlled characteristics of its local cation density, amphipathic composition as well as three-dimensional (3D) conformation to improve interactions with bacterial membranes. The antimicrobial assay and biocompatibility assay results showed that 96.83% of S. aureus and 99.99% of E. coli were killed after being in contact with the antibacterial coating, while no toxicity to mammalian cells or no hemolysis was detected. This antimicrobial activity was further confirmed by the molecular dynamics simulation results, which demonstrated that the employment of lysine peptide dendrimers enhanced the electrostatic interaction and hydrogen bonding between the brush and bacterial membranes remarkably. Such bottlebrush-like antibacterial coating constructed using α-helical peptide dendritic polymers may become an effective strategy for manufacturing antibacterial products for biomedical uses.

Studies of the Sulfonated Hydrogenated Styrene-Isoprene-Styrene Block Copolymer and Its Surface Properties, Cytotoxicity, and Platelet-Contacting Characteristics

Styrenic thermoplastic elastomers (TPEs) consist of styrenic blocks. They are connected with other soft segments by a covalent linkage and are widely used in human life. However, in biomedical applications, TPEs need to be chemically hydrogenated in advance to enhance their properties such as strong UV/ozone resistance and thermal-oxidative stability. In this study, films composed of sulfonated hydrogenated TPEs were evaluated. Hydrogenated tert-butyl styrene–styrene–isoprene block copolymers were synthesized and selectively sulfonated to different degrees by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tert-butyl styrene–styrene–isoprene block copolymer and acetyl sulfate, sulfonated films were optimized to demonstrate sufficient mechanical integrity in water as well as good biocompatibility. The thermal plastic sulfonated films were found to be free of cytotoxicity and platelet-compatible and could be potential candidates in biomedical film applications such as wound dressings.

Antifouling and Antibacterial Properties Constructed by Quaternary Ammonium and Benzyl Ester Derived from Lysine Methacrylamide

Hemocompatibility and antibacterial property are essential for blood contact devices and medical intervention materials. In this study, positively charged quaternary ammonium (QAC) and hydrophobic benzyl group (OBzl) were introduced onto hydrophilic lysine methacrylamide (LysAAm) to obtain two monomers LysAAm-QAC and LysAAm-OBzl, respectively. The structure characterizations of LysAAm-QAC and LysAAm-OBzl were determined by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry. LysAAm-QAC and LysAAm-OBzl were cografted onto a silicon wafer with different feeding ratios to construct antifouling and antibacterial properties. The results of fibrinogen adsorption and platelet adhesion proved that the modified sample with the feeding ratio of 3:7 had superior antifouling property. Furthermore, an antimicrobial test with both 2 and 24 h indicated that the modified sample with the feeding ratio of 3:7 had antibacterial ability. The antifouling property was provided by the high surface coverage of LysAAm-QAC and LysAAm-OBzl (91.49%) and the hydrophilic main structure LysAAm on LysAAm-QAC and LysAAm-OBzl (water contact angle was 43.6°). The antibacterial property was improved with the proportion of LysAAm-OBzl (43.6-58.5%) because the increasing hydrophobic OBzl enhanced the ability to insert into the membrane of bacteria and raise the bactericidal efficiency. In application, LysAAm-QAC and LysAAm-OBzl with the feeding ratio of 3:7 were grafted onto the surface of poly(styrene-b-(ethylene-co-butylene)-b-styrene), and a bifunctional surface with antifouling and antibacterial properties was fabricated, which had promising applications in blood contact devices and medical intervention materials.

Series of In Situ Photoinduced Polymer Graftings for Sensitive Detection of Protein Biomarkers via Cascade Amplification of Liquid Crystal Signals

Developing of new polymeric materials for the sensitive and rapid detection of trace protein biomarkers has attracted increasing attention in biomedical fields. Herein, series of in situ photoinduced polymer graftings were developed for sensitive detection of protein biomarkers by using featured cascade amplification of liquid crystal (LC) signals. The limit-of-detection (LOD) for native bovine serum albumin (BSA) molecules is around 10 μg/mL in a LC biosensor before signal amplification. Upon the cascade amplification using surface-grafted polymers, poly[poly(ethylene glycol) methacrylate] grafting ( s-P(PEGMA)) exhibits superior amplification ability (10⁴-fold lower than native BSA) than the other two graftings of poly(2-hydroxyethyl methacrylate) ( s-PHEMA) and poly(methacrylic acid) ( s-PMAA; 10²-fold lower than native BSA). The contact angles of water and LC on the s-P(PEGMA) grafting show significant difference in comparison with s-PHEMA and s-PMAA graftings ( p < 0.05), implying interfacial energies of the grafted polymers may dictate the orientational transition of LCs. The clinical urine samples collected from the patients with proteinuria were also used to confirm the feasibility of the polymer-amplified LC sensors for practical protein assays. The present work reveals that in situ photoinduced polymer grafting is one promising method to amplify the signals of LC biosensors for the rapid and sensitive detection of trace protein biomarkers.

Opportunities and challenges for the development of polymer-based biomaterials and medical devices

Biomaterials and medical devices are broadly used in the diagnosis, treatment, repair, replacement or enhancing functions of human tissues or organs. Although the living conditions of human beings have been steadily improved in most parts of the world, the incidence of major human’s diseases is still rapidly growing mainly because of the growth and aging of population. The compound annual growth rate of biomaterials and medical devices is projected to maintain around 10% in the next 10 years; and the global market sale of biomaterials and medical devices is estimated to reach $400 billion in 2020. In particular, the annual consumption of polymeric biomaterials is tremendous, more than 8000 kilotons. The compound annual growth rate of polymeric biomaterials and medical devices will be up to 15–30%. As a result, it is critical to address some widespread concerns that are associated with the biosafety of the polymer-based biomaterials and medical devices. Our group has been actively worked in this direction for the past two decades. In this review, some key research results will be highlighted.

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

Infection-resistant styrenic thermoplastic elastomers that can switch from bactericidal capability to anti-adhesion are facilely chloromethylated, followed by quaternization with methyl 3-(dimethylamino) propionate.

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.

Facile fabrication of microsphere-polymer brush hierarchically three-dimensional (3D) substrates for immunoassays

A facile strategy was developed to create a microsphere-polymer brush hierarchically three-dimensional substrate for high signal and low noise in immunoassays.

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.

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.

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.

Surface modification of cycloolefin polymer via surface-initiated photoiniferter-mediated polymerization for suppressing bioadhesion

Cycloolefin polymer was modified via surface-initiated photoiniferter-mediated polymerization for suppressing bioadhesion.

Surface functionalization of styrenic block copolymer elastomeric biomaterials with hyaluronic acid via a "grafting to" strategy

As a biostable elastomer, the hydrophobicity of styrenic block copolymer (SBC) intensely limits its biomedical applications. In order to overcome such shortcoming, the SBC films were grafted with hyaluronic acid (HA) using a coupling agent. The surface chemistry of the modified films was examined by ATR-FTIR and XPS techniques, and the surface morphology was visually described by AFM. The biological performances of the HA-modified films were evaluated by a series of experiments, such as protein adsorption, platelet adhesion, and in vitro cytocompatibility. It was found that the HA-modified samples showed a low adhesiveness to fibroblast at the initial stage; however, it stimulated the growth of fibroblast. The L929 fibroblast growth presented a strong dependence on the molecular weight (MW) of HA. The samples modified with 17kDa HA exhibited the worst wettability and platelet adhesion, while providing the best results of supporting fibroblast proliferation.

Improved biocompatibility of poly (styrene-b-(ethylene-co-butylene)-b-styrene) elastomer by a surface graft polymerization of hyaluronic acid

Hyaluronic acid (HA) is an important component of extracellular matrix (ECM) in many tissues, providing a hemocompatible and supportive environment for cell growth. In this study, glycidyl methacrylate-hyaluronic acid (GMHA) was first synthesized and verified by proton nuclear magnetic resonance ((1)H NMR) spectroscopy. GMHA was then grafted to the surface of biomedical elastomer poly (styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) via an UV-initiated polymerization, monitored by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The further improvement of biocompatibility of the GMHA-modified SEBS films was assessed by platelet adhesion experiments and in vitro response of murine osteoblastic cell line MC-3T3-E1 with the virgin SEBS surface as the reference. It showed that the surface modification with HA strongly resisted platelet adhesion whereas improved cell-substrate interactions.