Polyvinyl alcohol/chitosan quaternary ammonium salt composite hydrogel with directional macroporous structure for photothermal synergistic antibacterial and wound healing promotion

After skin tissue trauma, wound infections caused by bacteria posed a great threat to skin repair. However, resistance to antibiotics, the current treatment of choice for bacterial infections, greatly affected the efficiency of anti-infection and wound healing. Therefore, there has been a critical need for the development of novel antimicrobial materials and advanced therapeutic methods to aid in skin repair. In this paper, rGO-PDA@ZIF-8 nanofillers were prepared by coating graphene oxide (GO) with dopamine (DA), followed by in situ growth of zeolite imidazolate framework-8 (ZIF-8). Using polyvinyl alcohol (PVA) and chitosan quaternary ammonium salt (CS) as matrix materials, along with polyethylene glycol (PEG) as a pore-forming agent, and rGO-PDA@ZIF-8 as an antimicrobial nano-filler, we successfully prepared rGO-PDA@ZIF-8/PVA/CS composite hydrogels with a directional macroporous structure using bidirectional freezing method and phase separation technique. This hydrogel exhibited excellent mechanical properties, good solubility and water retention capabilities. In addition, the hydrogel demonstrated excellent biocompatibility. Most notably, it not only exhibited excellent bactericidal effect against E. coli and S. aureus (99.1 % and 99.0 %, respectively) under the synergistic effect of intrinsic antibacterial activity and photothermal antibacterial, but also exhibited the ability to promote wound healing, making it a promising candidate for wound healing applications.

Surface functionalization of polyurethanes: A critical review

Synthetic polymers, particularly polyurethanes (PUs), have revolutionized bioengineering and biomedical devices due to their customizable mechanical properties and long-term stability. However, the inherent hydrophobic nature of PU surfaces arises common issues such as high friction, strong protein adsorption, and thrombosis, especially in the physiological environment of blood contact. To overcome these issues, researchers have explored various modification techniques to improve the surface biofunctionality of PUs. In this review, we have systematically summarized several typical surface modification methods including surface plasma modification, surface oxidation-induced grafting polymerization, isocyanate-based chemistry coupling, UV-induced surface grafting polymerization, adhesives-assisted attachment strategy, small molecules-bridge grafting, solvent evaporation technique, and hydrogen bonding interaction. Correspondingly, the advantages, limitations, and future prospects of these surface modification methods were discussed. This review provides an important guidance or tool for developing surface functionalized PUs in the fields of bioengineering and medical devices.

In Situ Growth of Zeolitic Imidazolate Framework-L in Macroporous PVA/CMC/PEG Composite Hydrogels with Synergistic Antibacterial and Rapid Hemostatic Functions for Wound Dressing

Although many advances have been made in medicine, traumatic bleeding and wound infection are two of the most serious threats to human health. To achieve rapid hemostasis and prevent infection by pathogenic microbes, the development of new hemostatic and antibacterial materials has recently gained significant attention. In this paper, safe, non-toxic, and biocompatible polyvinyl alcohol (PVA); carboxymethyl cellulose (CMC), which contains several carboxyl and hydroxyl groups; and polyethylene glycol (PEG), which functions as a pore-forming agent, were used to prepare a novel PVA/CMC/PEG-based composite hydrogel with a macroporous structure by the freeze-thaw method and the phase separation technique. In addition, a PVA/CMC/PEG@ZIF-L composite hydrogel was prepared by the in situ growth of zeolitic imidazolate framework-L (ZIF-L). ZIF-L grown in situ on hydrogels released Zn²⁺ and imidazolyl groups. They elicited a synergistic antibacterial effect in hemostasis with PVA and CMC, rendering the PVA/CMC/PEG@ZIF-L hydrogel with a good antibacterial effect against Staphylococcus aureus. At the same time, the macroporous structure enabled the rapid release of Zn²⁺ and imidazolyl groups in ZIF-L and promoted cell proliferation at an early stage, enhancing the coagulation efficiency. A rat liver injury model was used to confirm its rapid hemostasis capacity.

Toward endothelialization via vascular endothelial growth factor immobilization on cell-repelling functional polyurethanes

We screened a family of nonspecific cell-repelling polyurethanes (PUs) whose backbones are attached with epoxy group-terminated polyethylene glycol (PEG) side chains. Water incubation of the PU films (with 9.2-31.1 wt % PEG) caused a surface enrichment of PEG chains where vascular endothelial growth factor (VEGF) was grafted by forming secondary amine linkages between VEGF molecules and the PEG spacer. These linkages are still ionizable similar to original primary amines in VEGF, thereby retaining the original charge distribution on VEGF macromolecules. This charge conservation together with PEG steric repulsion helped to preserve VEGF conformation and bioactivity. The PU substrates with suitable hard segments contents and VEGF surface densities can selectively induce endothelial cells (ECs) adhesion and proliferation toward endothelialization. Moreover, the PU substrates, even grafted with fibrinogen (Fg), cannot trigger platelet adhesion and deformation, suggesting an inactive conformation of the grafted Fg. Thus enough antithrombogenicity of the PU substrates could be expected before full endothelialization. These PU materials might be applied onto the lumens of vascular grafts, potentially stimulating luminal endothelialization in vivo. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 965-977, 2019.

Surface tailoring for selective endothelialization and platelet inhibition via a combination of SI-ATRP and click chemistry using Cys-Ala-Gly-peptide

Surface tailoring is an attractive approach to enhancing selective endothelialization, which is a prerequisite for current vascular prosthesis applications. Here, we modified polycarbonate urethane (PCU) surface with both poly(ethylene glycol) and Cys-Ala-Gly-peptide (CAG) for the purpose of creating a hydrophilic surface with targeting adhesion of endothelial cells (ECs). In the first step, PCU-film surface was grafted with poly(ethylene glycol) methacrylate (PEGMA) to covalently tether hydrophilic polymer brushes via surface initiated atom transfer radical polymerization (SI-ATRP), followed by grafting of an active monomer pentafluorophenyl methacrylate (PFMA) by a second ATRP. The postpolymerization modification of the terminal reactive groups with allyl amine molecules created pendant allyl groups, which were subsequently functionalized with cysteine terminated CAG-peptide via photo-initiated thiol-ene click chemistry. The functionalized surfaces were characterized by water contact angle and XPS analysis. The growth and proliferation of human ECs or human umbilical arterial smooth muscle cells on the functionalized surfaces were investigated for 1, 3 and 7 day/s. The results indicated that these peptide functionalized surfaces exhibited enhanced EC adhesion, growth and proliferation. Furthermore, they suppressed platelet adhesion in contact with platelet-rich plasma for 2h. Therefore, these surfaces with EC targeting ligand could be an effective anti-thrombogenic platform for vascular tissue engineering application.

Nanoparticles complexed with gene vectors to promote proliferation of human vascular endothelial cells

Amphiphilic block copolymers containing biodegradable hydrophobic segments of depsipeptide based copolymers have been synthesized and explored as gene carriers for enhancing proliferation of endothelial cells in vitro. These polymers form nanoparticles (NPs) with positive charges on their surface, which could condense recombinant plasmids of enhanced green fluorescent protein plasmid and ZNF580 gene (pEGFP-ZNF580) and protect them against DNase I. ZNF580 gene is efficiently transported into EA.hy926 cells to promote their proliferation, whereby the transfection efficiency of NPs/pEGFP-ZNF580 is approximately similar to that of Lipofectamine 2000. These results indicate that the NPs might have potential as a carrier for pEGFP-ZNF580, which could support endothelialization of cardiovascular implants.

Antimicrobial surfaces grafted random copolymers with REDV peptide beneficial for endothelialization

Multifunctional surfaces have been created by surface modification and click reactions. These surfaces possess excellent hemocompatibility and endothelialization, as well as effective antimicrobial activity.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.

Grafting of phosphorylcholine functional groups on polycarbonate urethane surface for resisting platelet adhesion

In order to improve the resistance of platelet adhesion on material surface, 2-methacryloyloxyethyl phosphorylcholine (MPC) was grafted onto polycarbonate urethane (PCU) surface via Michael reaction to create biomimetic structure. After introducing primary amine groups via coupling tris(2-aminoethyl)amine (TAEA) onto the polymer surface, the double bond of MPC reacted with the amino group to obtain MPC modified PCU. The modified surface was characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results verified that MPC was grafted onto PCU surface by Michael reaction method. The MPC grafted PCU surface had a low water contact angle and a high water uptake. This means that the hydrophilic PC functional groups improved the surface hydrophilicity significantly. In addition, surface morphology of MPC grafted PCU film was imaged by atomic force microscope (AFM). The results showed that the grafted surface was rougher than the blank PCU surface. In addition, platelet adhesion study was evaluated by scanning electron microscopy (SEM) observation. The PCU films after treated with platelet-rich plasma demonstrated that much fewer platelets adhered to the MPC-grafted PCU surface than to the blank PCU surface. The antithrombogenicity of the MPC-grafted PCU surface was determined by the activated partial thromboplastin time (APTT). The result suggested that the MPC modified PCU may have potential application as biomaterials in blood-contacting and some subcutaneously implanted devices.

Grafting of poly(ethylene glycol) monoacrylates on polycarbonateurethane by UV initiated polymerization for improving hemocompatibility

Poly(ethylene glycol) monoacrylates (PEGMAs) with a molecular weight between 400 and 1,000 g mol(-1) were grafted by ultraviolet initiated photopolymerization on the surface of polycarbonateurethane (PCU) for increasing its hydrophilicity and improving its hemocompatibility. The surface-grafted PCU films were characterized by Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle, scanning electron microscopy (SEM) and atomic force microscopy measurements. The surface properties of the modified films were studied in dry and wetted state. Blood compatibility of the surfaces was evaluated by platelet adhesion tests and adhered platelets were determined by SEM. The results showed that the hydrophilicity of the films had been increased significantly by grafting PEGMAs, and platelets adhesion onto the film surface was obviously suppressed. Furthermore, the molecular weight of PEGMAs had a great effect on the hydrophilicity and hemocompatibility of the PCU films after surface modification and increased with increasing molecular weight of PEGMAs.

Fabrication of PU/PEGMA crosslinked hybrid scaffolds by in situ UV photopolymerization favoring human endothelial cells growth for vascular tissue engineering

Poly(ethylene glycol) methacrylate (PEGMA) was introduced into a polyurethane (PU) solution in order to prepare electrospun scaffold with improving the biocompatibility by electrospinning technology for potential application as small diameter vascular scaffolds. Crosslinked electrospun PU/PEGMA hybrid nanofibers were fabricated by a reactive electrospinning process with N,N'-methylenebisacrylamide as crosslinker and benzophenone as photoinitiator. The photoinduced polymerization and crosslinking reaction took place simultaneously during the electrospinning process. The electrospinning solutions with various weight ratios of PU/PEGMA were successfully electrospun. No significant difference in the scaffold morphology was found by SEM when PEGMA content was <20 wt%. The crosslinked fibrous scaffolds of PU/PEGMA exhibited higher mechanical strength than the pure PU scaffold. The hydrophilicity of scaffolds was controlled by varying the PU/PEGMA weight ratio. The tissue compatibility of electrospun nanofibrous scaffolds were tested using human umbilical vein endothelial cells (HUVECs). Cell morphology and cell proliferation were measured by SEM, fluorescence microscopy and thiazolyl blue assay (MTT) after 1, 3, 7 days of culture. The results indicated that the cell morphology and proliferation on the crosslinked PU/PEGMA scaffolds were better than that on the pure PU scaffold. Furthermore, the appropriate hydrophilic surface with water contact angle in the range of 55-75° was favorable of improvement the HUVECs adhesion and proliferation. Cells seeded on the crosslinked PU/PEGMA (80/20) scaffolds infiltrated into the scaffolds after 7 days of growth. These results indicated the crosslinked electrospun PU/PEGMA nanofibrous scaffolds were potential substitutes for artificial vascular scaffolds.

Surface Modification of Polycarbonateurethane by Grafting Phosphorylcholine Glyceraldehydes for Improving Hemocompatibility

Phosphorylcholine glyceraldehyde (PCGA) was used as a phosphorylcholine (PC) group containing compound to graft onto the surface of polycarbonateurethane (PCU) film using 1,6-hexanediamine (HDA) or α,ω-diamino-poly(ethylene glycol) (APEG, Mn = 200) as a spacer, in order to introduce biomimetic structure onto the polymer surface. X-ray photoelectron spectroscopy (XPS) analysis shows that PCGA has been covalently linked to the PCU surface. Water contact angle test suggests that the surface hydrophilicity has been improved after PCGA is grafted onto the surface of PCU film. Scanning electron microscope (SEM) observation of the modified PCU films after contacting with plasma-rich plasma demonstrates that platelets rarely adhere but a large number of platelets adhere to the original PCU surface. The hemocompatibility of the PC modified PCU film has been improved obviously after grafting with PCGA with PEG spacer.

Grafting Sulfoammonium Zwitterionic Brushes onto Polycarbonateurethane Surface to Improve Hemocompatibility

Poly(3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate) (poly(DMAPS)) zwitterionic brushes were grafted onto the polycarbonateurethane (PCU) surface to improve its hydrophilicity and hemocompatibility by Ultraviolet (UV) polymerization. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle were used to characterize the chemical and physical properties of the modified PCU surface. DMAPS-grafted PCU films showed significantly high hydrophilicity owing to the high hydrophilic poly(DMAPS) zwitterionic brushes. The cytotoxicity tests revealed the sulfoammonium zwitterionic brushes modified PCU film had good cytocompatibility. In addition, the hemocompatibility of the modified PCU films was evaluated by hemolytic tests and platelet adhesion tests. The PCU films modified with zwitterionic brushes had a lower hemolytic index, showed effective resistance to platelet adhesion. Due to the fact that sulfoammonium zwitterionic brushes can improve the hemocompatibility of the PCU surface, this gives rise to its potential application as blood-contacting materials or devices.