Shifang Luan

Antibacterial and Hemocompatibility Switchable Polypropylene Nonwoven Fabric Membrane Surface

In this article, a facile approach to fabricate a biofunctional polypropylene nonwoven fabric membrane (PP NWF) with a switchable surface from antibacterial property to hemocompatibility is presented. In the first step, a cationic carboxybetaine ester monomer, [(2-(methacryboxy) ethyl)]-N,N-dimethylamino-ethylammonium bromide, methyl ester (CABA-1-ester) was synthesized. Subsequently, this monomer was introduced on the PP NWF surface via plasma pretreatment and a UV-induced graft polymerization technique. Finally, a switchable surface from antibacterial property to hemocompatibility was easily realized by hydrolysis of poly(CABA-1-ester) moieties on the PP NWF surface under mild conditions. Surface hydrolysis behaviors under different pH conditions were investigated. These PP NWFs grafted with poly(CABA-1-ester) segments can cause significant suppression of S. aureus proliferation; after hydrolysis, these surfaces covered by poly[(2-(methacryloxy) ethyl)] carboxybetaine (poly(CABA)) chains exhibited obvious reduction in protein adsorption and platelet adhesion, and remarkably enhanced antithrombotic properties. This strategy demonstrated that a switchable PP NWF surface from antibacterial property to hemocompatibility was easily developed by plasma pretreatment and UV-induced surface graft polymerization and that this surface may become an attractive platform for a range of biomedical applications.

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

Poly(N-vinyl pyrrolidone) (PNVP) was covalently grafted onto the surface of biomedical poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) elastomer via a technique of UV-induced graft polymerization combined with plasma pre-treatment. The surface graft polymerization of N-vinyl pyrrolidone (NVP) was confirmed by ATR-FTIR and XPS. Effect of the parameters of graft polymerization, i.e., the initiator concentration, the UV irradiation time and the monomer concentration on the grafting density was investigated. The morphology and the wettability of the PNVP-modified surfaces were characterized by AFM and DSA, respectively. Protein adsorption and platelet adhesion were obviously suppressed after PNVP was grafted onto the SEBS substrates.

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.

Core/shell rubber toughened polyamide 6: an effective way to get good balance between toughness and yield strength

We have recently shown that by adding 10 to 30 wt% core/shell toughener with a low density polyethylene (LDPE) core and a polybutadiene-g-maleic anhydride (PB-g-MAH) rubber shell to polyamide 6 (PA6), the impact strength of PA6 matrix can be significantly increased by 600–1000%. However, this is at the expense of quite large losses in elastic modulus of 10–25% and tensile yield strength of 30–55%, especially at high core/shell rubber loading (e.g., 30 wt%). In this study, we have redressed this problem by replacing the LDPE core with a polypropylene (PP) core, which has both higher elastic modulus and yield strength than that of LDPE, forming a new core/shell (PP/PB-g-MAH) toughener. When this core/shell toughener containing 5 wt% PB-g-MAH is blended with PA6 in the weight ratios of 10/90 and 30/70, the Izod impact strengths are 390 and 480 J m−1 (which are 330 and 550% increases compared to neat PA6), and the modulus are 2.37 and 2.13 GPa, and yield strength are 60.2 and 54 MPa, respectively (which represent only 6 and 15% loss of modulus, and 5 and 13% decrease in yield strength relative to neat PA6). These improved results confirm that although the decrease of tensile modulus cannot be avoided with increasing impact strength, increasing the elastic modulus and yield strength of the core material in the rigid core/soft rubber shell toughener is an effective way to obtain a good balance of elastic modulus, tensile yield strength and impact strength.

Liquid-Infused Poly(styrene-b-isobutylene-b-styrene) Microfiber Coating Prevents Bacterial Attachment and Thrombosis

Infection and thrombosis associated with medical implants cause significant morbidity and mortality worldwide. As we know, current technologies to prevent infection and thrombosis may cause severe side effects. To overcome these complications without using antimicrobial and anticoagulant drugs, we attempt to prepare a liquid-infused poly(styrene-b-isobutylene-b-styrene) (SIBS) microfiber coating, which can be directly coated onto medical devices. Notably, the SIBS microfiber was fabricated through solution blow spinning. Compared to electrospinning, the solution blow spinning method is faster and less expensive, and it is easy to spray fibers onto different targets. The lubricating liquids then wick into and strongly adhere the microfiber coating. These slippery coatings can effectively suppress blood cell adhesion, reduce hemolysis, and inhibit blood coagulation in vitro. In addition, Pseudomonas aeruginosa (P. aeruginosa) on the lubricant infused coatings slides readily, and no visible residue is left after tilting. We furthermore confirm that the lubricants have no effects on bacterial growth. The slippery coatings are also not cytotoxic to L929 cells. This liquid-infused SIBS microfiber coating could reduce the infection and thrombosis of medical devices, thus benefiting human health.

Enhanced biocompatibility of biostable poly(styrene-b-isobutylene-b-styrene) elastomer via poly(dopamine)-assisted chitosan/hyaluronic acid immobilization

The biostable poly(styrene-b-isobutylene-b-styrene) (SIBS) elastomers are well-known for their large-scale in vivo application as drug-eluting coatings in coronary stents. In this study, the SIBS elastomers were modified with a poly(dopamine) (PDA) adherent layer, followed by integrating both chitosan (CS) and hyaluronic acid (HA) onto their surfaces. The as-prepared samples (SIBS-CS-g-HA) presented excellent cytocompatibility because CS facilitates cell attachment and HA enhances cell proliferation. The initial adhesion test of E. coli on SIBS-CS-g-HA showed effective antiadhesive properties. The in vitro antibacterial test confirmed that SIBS-CS-g-HA has good antibacterial activity.

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.

Chitosan/hydroxyapatite (HA)/hydroxypropylmethyl cellulose (HPMC) spongy scaffolds-synthesis and evaluation as potential alveolar bone substitutes

Alveolar bone loss is associated with infections and its augmentation is a pre-requisite for the success of dental implants. In present study, we aim to develop and evaluate novel freeze dried doxycycline loaded chitosan (CS)/hydroxyapatite (HA) spongy scaffolds where hydroxypropylmethyl cellulose (HPMC) was added as a crosslinker. Scaffolds displayed compressive strength of 14MPa/cm3 and 0.34 as elastic response. The interconnected pore diameter was 41-273μm, favorably provided the template supporting cells and transport. An overall 10% degradation was seen after 14days studies at pH 7.4 in PBS. Doxycycline hyclate, a frequently used drug to counter oral infections, demonstrated an initial burst release (6-8h), followed by a sustain release profile for the remaining 64h. CS/HA/HPMC scaffolds were nontoxic and promoted pre-osteoblast cell viability as seen with live/dead calcein staining after 24h where scaffolds with 10% and 25% HPMC by weight of scaffold had more viable cells. Scaffolds with 10%, 20% and 25% HPMC by weight of scaffold showed efficient cellular adhesion as seen in scanning electron microscopy images (day 8) indicating that pre-osteoblast cells were able to adhere well on the surface and into the porous structure via cytoplasmic extensions. Hoechst 33258 nuclear staining at day 2 and 8 indicated cell proliferation which was further supported byMTT assay at day 2, 4 and 8. Although all scaffolds supported pre-osteoblast cell viability, alkaline phosphatase (ALP) staining demonstrated that upon induction, differentiation was pronounced in case of scaffolds with 10% HMPC scaffolds. Conclusively, these materials having all the required mechanical and biological properties are potential candidates for alveolar bone regeneration.

Synthesis of amphiphilic poly(cyclooctene)-graft-poly(ethylene glycol) copolymersviaROMP and its surface properties

Macromonomer cyclooctene-poly(ethylene glycol) (cyclooctene-PEG) was first synthesized before being copolymerized with cyclooctene by ring opening metathesis polymerization (ROMP) to obtain an amphiphilic graft copolymer (poly(cyclooctene)-g-PEG) with polycyclooctene as the hydrophobic trunk chain and PEG as hydrophilic side chains. The structure of poly(cyclooctene)-g-PEG copolymer was characterized by FTIR and 1H-NMR. The surface properties of poly(cyclooctene)-g-PEG film were evaluated through water contact angle and X-ray photoelectron spectroscopy (XPS). Water contact angle decreased from 87.7° to 65.8° along with increasing the content of PEG. Protein adsorption results showed that poly(cyclooctene)-g-PEG copolymers had significant effect on preventing bovine serum albumin (BSA) from absorbing onto the polymer surface.

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.