A green single-step procedure to synthesize Ag-containing nanocomposite coatings with low cytotoxicity and efficient antibacterial properties

Fabrication of Biodegradable and Biocompatible Functional Polymers for Anti-Infection and Augmenting Wound Repair

The problem of bacteria-induced infections threatens the lives of many patients. Meanwhile, the misuse of antibiotics has led to a significant increase in bacterial resistance. There are two main ways to alleviate the issue: one is to introduce antimicrobial agents to medical devices to get local drug releasing and alleviating systemic toxicity and resistance, and the other is to develop new antimicrobial methods to kill bacteria. New antimicrobial methods include cationic polymers, metal ions, hydrophobic structures to prevent bacterial adhesion, photothermal sterilization, new biocides, etc. Biodegradable biocompatible synthetic polymers have been widely used in the medical field. They are often used in tissue engineering scaffolds as well as wound dressings, where bacterial infections in these medical devices can be serious or even fatal. However, such materials usually do not have inherent antimicrobial properties. They can be used as carriers for drug delivery or compounded with other antimicrobial materials to achieve antimicrobial effects. This review focuses on the antimicrobial behavior, preparation methods, and biocompatibility testing of biodegradable biocompatible synthetic polymers. Degradable biocompatible natural polymers with antimicrobial properties are also briefly described. Finally, the medical applications of these polymeric materials are presented.

Antimicrobial peptide GL13K immobilized onto SLA-treated titanium by silanization: antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA)

Infection is the main reason for implant failure, and the incidence of drug-resistant bacterial infection has increased in recent years. Further, methicillin-resistant Staphylococcus aureus (MRSA)-related implant infection has become a serious worldwide threat. New strategies, other than antibiotics, to tackle drug-resistance, are of high clinical significance. Antimicrobial peptides show clear superiority over conventional antibiotics in inhibiting drug-resistant bacteria. In the present study, we combined the antimicrobial peptide, GL13K, with sandblasting and acid-etching (SLA)-treated titanium using a silane coupling agent. Field emission scanning electron microscopy images showed the morphology of the coating. Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results confirmed loading of GL13K, and the hydrophilicity of the SLA-GL13K coating was evaluated by water contact angle analysis. The releasing study of samples showed that the coating has a sustained releasing profile. SLA-GL13K coating exhibited strong contact- and release-killing abilities against MRSA, E. coli, and S. aureus. Meanwhile, Cell Counting Kit 8 analysis and examination of cell morphology demonstrated that the SLA-GL13K coating had good cytocompatibility at antibacterial concentrations. Overall, all these results suggest that SLA-GL13K coating can be successfully fabricated using silanization, and is a promising candidate for controlling MRSA-induced implant-related infection.

Electrophoretic Deposition and Characterization of Functional Coatings Based on an Antibacterial Gallium (III)-Chitosan Complex

Despite their broad biomedical applications in orthopedics and dentistry, metallic implants are still associated with failures due to their lack of surface biofunctionality, leading to prosthesis-related microbial infections. In order to address this issue, the current study focuses on the fabrication and characterization of a novel type of antibacterial coating based on gallium (III)-chitosan (Ga (III)-CS) complex layers deposited on metallic substrates via electrophoretic deposition (EPD). Aiming for the production of homogeneous and monophasic coatings, a two step-procedure was applied: the first step involved the synthesis of the Ga (III)-CS complex, followed by EPD from suitable solutions in an acetic acid–aqueous solvent. The influence of Ga (III) concentration on the stability of the suspensions was evaluated in terms of zeta potential. Fourier transform infrared (FTIR) and energy dispersive X-ray (EDX) spectroscopic analyses indicated the chelation of CS with Ga (III) within the coatings, while scanning electron microscopy (SEM) confirmed that no additional metallic gallium deposited during EPD. Furthermore, the results demonstrated that the wettability, mechanical properties, swelling ability, and enzymatic degradation of the coatings were affected by the quantity of Ga (III) ions. Colony forming unit (CFU) tests showed a strong synergistic effect between CS and Ga (III) in inhibiting Escherichia coli strain growth compared to control CS samples. An in vitro study with MG-63 cells showed that Ga (III)-containing coatings were not toxic after 24 h of incubation.

Electrophoretic Deposition of Copper(II)-Chitosan Complexes for Antibacterial Coatings

Bacterial infection associated with medical implants is a major threat to healthcare. This work reports the fabrication of Copper(II)–Chitosan (Cu(II)–CS) complex coatings deposited by electrophoretic deposition (EPD) as potential antibacterial candidate to combat microorganisms to reduce implant related infections. The successful deposition of Cu(II)–CS complex coatings on stainless steel was confirmed by physicochemical characterizations. Morphological and elemental analyses by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy verified the uniform distribution of copper in the Chitosan (CS) matrix. Moreover, homogeneous coatings without precipitation of metallic copper were confirmed by X-ray diffraction (XRD) spectroscopy and SEM micrographs. Controlled swelling behavior depicted the chelation of copper with polysaccharide chains that is key to the stability of Cu(II)–CS coatings. All investigated systems exhibited stable degradation rate in phosphate buffered saline (PBS)–lysozyme solution within seven days of incubation. The coatings presented higher mechanical properties with the increase in Cu(II) concentration. The crack-free coatings showed mildly hydrophobic behavior. Antibacterial assays were performed using both Gram-positive and Gram-negative bacteria. Outstanding antibacterial properties of the coatings were confirmed. After 24 h of incubation, cell studies of coatings confirms that up to a certain threshold concentration of Cu(II) were not cytotoxic to human osteoblast-like cells. Overall, our results show that uniform and homogeneous Cu(II)–CS coatings with good antibacterial and enhanced mechanical stability could be successfully deposited by EPD. Such antibiotic-free antibacterial coatings are potential candidates for biomedical implants.

Electrodeposition of Polysaccharide and Protein Hydrogels for Biomedical Applications

In the last few decades, polysaccharide and protein hydrogels have attracted significant attentions and been applied in various engineering fields. Polysaccharide and protein hydrogels with appealing physical and biological features have been produced to meet different biomedical applications for their excellent properties related to biodegradability, biocompatibility, nontoxicity, and stimuli responsiveness. Numerous methods, such as chemical crosslinking, photo crosslinking, graft polymerization, hydrophobic interaction, polyelectrolyte complexation and electrodeposition have been employed to prepare polysaccharide and protein hydrogels. Electrodeposition is a facile way to produce different polysaccharide and protein hydrogels with the advantages of temporal and spatial controllability. This paper reviews the recent progress in the electrodeposition of different polysaccharide and protein hydrogels. The strategies of pH induced assembly, Ca2+ crosslinking, metal ions induced assembly, oxidation induced assembly derived from electrochemical methods were discussed. Pure, binary blend and ternary blend polysaccharide and protein hydrogels with multiple functionalities prepared by electrodeposition were summarized. In addition, we have reviewed the applications of these hydrogels in drug delivery, tissue engineering and wound dressing.

Antibacterial effects of silver incorporated zeolite coatings on 3D printed porous stainless steels

Functionalization of porous metals with antibacterial coatings is hotly pursued in recent decade. Here we fabricated a highly porous stainless steel component by selective laser melting and then coated with silver incorporated zeolite by in situ hydrothermal crystallization method. The morphology of their surface was investigated by scanning electron microscopy. The inhibition of Escherichia coli and Staphylococcus aureus were identified by bacterial viability studies after 24 h of incubation. More importantly, the obtained coatings show better osteointegration by spreading bone marrow stromal cells (BMSCs) after cultured with different scaffold extract solutions for 1, 3, and 5 days. These results suggest that silver incorporated zeolite coatings on 3D printed porous stainless steels exhibit better antibacterial activity and biocompatibility, showing potential application in the field of medical implant materials.

Unravelling the detrimental effect of water in the polyol synthesis of ultrathin silver nanowires

Generation of particle by-products during the synthesis of ultrathin silver nanowires can be suppressed via eliminating water in a precursor mixing step.

Electrophoretic deposition of dexamethasone-loaded gelatin nanospheres/chitosan coating and its dual function in anti-inflammation and osteogenesis

Surface modification of metallic implants with bioactive and biodegradable coatings could be a promising approach for bone regeneration. The objective of this study was to prepare chitosan/gelatin nanospheres (GNs) composite coating for the delivery of dexamethasone (DEX). GNs with narrow size distribution and negative surface charge were firstly prepared by a two-step desolvation method. Homogeneous and stable gelatin nanospheres/chitosan (GNs/CTS) composite coatings were formed by electrophoretic deposition (EPD). Drug loading, encapsulation efficiency and in vitro release of DEX were estimated using high performance liquid chromatography (HPLC). The anti-inflammatory effect of DEX-loaded coatings on macrophage RAW 264.7 cells was assessed by the secretion of tumour necrosis factor (TNF) and inducible nitric oxide synthase (iNOS). Osteogenic differentiation of MC3T3-E1 osteoblasts on DEX-loaded coatings was investigated by osteogenic gene expression and mineralization. The DEX in GNs/CTS composite coating showed a two-stage release pattern could not only suppress inflammation during the burst release period, but also promote osteogenic differentiation in the sustained release period. This study might offer a feasible method for modifying the surface of metallic implants in bone regeneration.

Glucuronoxylan-mediated silver nanoparticles: green synthesis, antimicrobial and wound healing applications

Hydrogel forming polysaccharides are attracting attention for the design of diverse nature silver nanoparticles (Ag NPs) with potential biological applications.