N-halamine-based multilayers on titanium substrates for antibacterial application

ROS-responsive hydrogel coating modified titanium promotes vascularization and osteointegration of bone defects by orchestrating immunomodulation

Ideal titanium implants are required to participate in bone repair actively to improve in situ osteointegration. However, the traditional surface functionalization methods of titanium implants are difficult to both achieve the active regulation and long-term stability of bioactive components. Here, a novel functionalized titanium which loaded with thymosin β4 (Tβ4) and covered by a hydrogel coating was designed and evaluated. A strong adhesion between the coating and the titanium substrate was realized by the synergistic action of borate ester bonds and surface topological structure. The hydrogel coating also achieved an in vivo adhesion between implant and tissue through hydrogen bonds and borate bonds. In addition, based on the ROS response property of borate bonds, the implant can release Tβ4 in response to the immune reaction of bone healing by regulating the polarization of macrophages, thereby reducing the fibrosis formation around the implant interface and promoting vascularization and osteointegration of bone defects.

Antimicrobial coating strategy to prevent orthopaedic device-related infections: recent advances and future perspectives

The rapid development of multidrug-resistant (MDR) bacteria and biofilm-related infections (BRIs) has urgently called for new strategies to combat severe orthopaedic device-related infections (ODRIs). Antimicrobial coating has emerged as a promising strategy in halting the incidence of ODRIs and treating ODRIs in long term. With the advancement of material science and biotechnology, numerous antimicrobial coatings have been reported in literature, showing superior antimicrobial and osteogenic functions. This review has specifically discussed the currently developed antimicrobial coatings in the perspective of drug release from the coating system, focusing on their realization of controlled and on demand antimicrobial agents release, as well as multi-functionality. Acknowledging the multidisciplinary nature of antimicrobial coating, the conceptual design, the deposition method and the therapeutic effect of the antimicrobial coatings have been described in detail and discussed critically. Particularly, the challenges and opportunities on the way toward the clinical translation of antimicrobial coatings have been highlighted.

Gallium (Ga)-strontium (Sr) layered double hydroxide composite coating on titanium substrates for enhanced osteogenic and antibacterial abilities

Bacterial infection and poor osteogenic capacity can result in the loosing or failure of titanium (Ti)-based implants in the clinic. Therefore, it is urgent to design an effective approach to enhance the osteogenic property and restrict bacterial activity. In this study, a layered double hydroxide (LDH) composed of Ga and Sr ions on Ti substrates by a hydrothermal method, then calcined in 250°C and denoted as LDH250. The scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were confirmed that the LDH films were successfully formed on the Ti substrates. Importantly, the obtained LDH films can induce an alkaline microenvironment around the Ti surface and regulate the behaviors of osteogenic cells and bacteria. In vitro cellular experiments, the LDH250 can enhance the differentiation of both MC3T3-E1 cells and osteoblasts, stimulate alkaline phosphatase activity (ALP), collagen secretion, and mineralization levels. Meanwhile, antimicrobial assay against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) demonstrated that the LDH250 samples had strong antibacterial abilities, which attributed to the release profile of Ga³⁺ could act as a "Trojan horse" to destroy the bacterial iron metabolism, inducing of local alkaline environment, and producing reactive oxygen species. Hence, this study provides an effective method for reducing antibacterial infection and enhancing the bone integrative capacity of Ti-based implants for orthopedic applications.

Long-lasting renewable antibacterial porous polymeric coatings enable titanium biomaterials to prevent and treat peri-implant infection

Peri-implant infection is one of the biggest threats to the success of dental implant. Existing coatings on titanium surfaces exhibit rapid decrease in antibacterial efficacy, which is difficult to promisingly prevent peri-implant infection. Herein, we report an N-halamine polymeric coating on titanium surface that simultaneously has long-lasting renewable antibacterial efficacy with good stability and biocompatibility. Our coating is powerfully biocidal against both main pathogenic bacteria of peri-implant infection and complex bacteria from peri-implantitis patients. More importantly, its antibacterial efficacy can persist for a long term (e.g., 12~16 weeks) in vitro, in animal model, and even in human oral cavity, which generally covers the whole formation process of osseointegrated interface. Furthermore, after consumption, it can regain its antibacterial ability by facile rechlorination, highlighting a valuable concept of renewable antibacterial coating in dental implant. These findings indicate an appealing application prospect for prevention and treatment of peri-implant infection.

Antibacterial and antibiofilm properties of graphene and its derivatives

Infections resulting from bacteria and biofilms have become a huge problem threatening human health. In recent years, the antibacterial and antibiofilm effects of graphene and its derivatives have been extensively studied. However, there continues to be some controversy over whether graphene and its derivatives can resist infection and biofilms. Moreover, the antibacterial mechanism and cytotoxicity of graphene and its derivatives are unclear. In the present review, antibacterial and antibiofilm abilities of graphene and its derivatives in solution, on the surface are reviewed, and their toxicity and possible mechanisms are also reviewed. Furthermore, we propose possible future development directions for graphene and its derivatives in antibacterial and antibiofilm applications.

A dual-functional implant with an enzyme-responsive effect for bacterial infection therapy and tissue regeneration

Biomaterial-associated bacterial infection is one of the major causes of implant failure. The treatment of such an implant infection typically requires the elimination of bacteria and acceleration of tissue regeneration around implants simultaneously. To address this issue, an ideal implanted material should have the dual functions of bacterial infection therapy and tissue regeneration at the same time. Herein, an enzyme-responsive nanoplatform was fabricated in order to treat implant-associated bacterial infection and accelerate tissue regeneration in vivo. Firstly, Ag nanoparticles were pre-encapsulated in mesoporous silica nanoparticles (MSNs) by a one-pot method. Then, poly-l-glutamic acid (PG) and polyallylamine hydrochloride (PAH) were assembled by the layer-by-layer (LBL) assembly technique on MSN-Ag to form LBL@MSN-Ag nanoparticles. Furthermore, the LBL@MSN-Ag nanoparticles were deposited on the surface of polydopamine-modified Ti substrates. PG is a homogeneous polyamide composed of an amide linkage, which can be degraded by glutamyl endonuclease secreted by Staphylococcus aureus. Inductively coupled plasma spectroscopy (ICP) results proved that the LBL@MSN-Ag particles show a significant enzyme responsive release of Ag ions. Furthermore, results of antibacterial experiments in vitro showed that the Ti substrates modified with an LBL@MSN-Ag nanocoating presented an excellent antibacterial effect. As for an animal experiment in vivo, in a bacterium infected femur-defect rat model, the modified Ti implants effectively treated bacterial infection. More importantly, the results of micro-CT, haematoxylin-eosin staining and Masson's trichrome staining demonstrated that the modified Ti implants significantly promoted the formation of new bone tissue after implantation for 4 weeks. The present system paves the way for developing the next generation of implants with the functions of treating bacterial infection and promoting tissue regeneration.

N-Halamine Hydantoin-Containing Chitosan: Synthesis, Characterization, Thermal and Photolytic Stability Studies

Current demand for new protective materials ensuring sterility is systematically growing. The purpose of this work was the synthesis of the biocidal N-halamine hydantoin-containing chitosan (CS-CMH-Cl) and characterization of its properties. The functionalization of the chitosan by 5-hydantoinacetic acid substitution leads to obtaining the CS-CMH polymer, which was chlorinated in next step to transform N-H into N-Cl bonds. In this study, the possibility of forming two biocidal N-Cl bonds in hydantoin ring, grafted onto chitosan chains, was proved. The structure and stability of the prepared material was confirmed by spectroscopic (FTIR, NMR, colorimetric test) and microscopic analyses (SEM, AFM). Surface properties were investigated based on contact-angle measurements. In addition, the thermal and photochemical stability of the obtained samples were determined as functional features, determining the range of potential use. It was found that both modified chitosan polymers (CS-CMH and CS-CMH-Cl) were characterized by the smaller thermal stability and more hydrophilic and rougher surface than unmodified CS. Photooxidative degradation of the obtained materials was observed mainly on the sample surface. After irradiation, the surfaces became more hydrophilic-especially in the case of the CS-CMH-Cl-which is advantageous from the point of view of the antibacterial properties. Antibacterial tests against S. aureus and E. coli confirmed the antibacterial activities of received CS-CMH-Cl material.

Functionalization of Ti substrate with pH-responsive naringin-ZnO nanoparticles for the reconstruction of large bony after osteosarcoma resection

After bone tumor resection, the large bony deficits are commonly reconstructed with Ti-based metallic endoprosthesis, which provide immediate stable fixation and allow early ambulation and weight bearing. However, when used in osteosarcoma resection, Ti implant-relative infection and tumor recurrence were recognized as the two critical factors for implantation failure. Hence, in this work, a novel zinc oxide nanoparticle decorating with naringin was prepared and immobilized onto Ti substrate. The drugs delivery profiles proved that in the bacterial infection and Warburg effect of osteosarcoma-induced acidic condition, naringin and Zn²⁺ can be released easily from the functional Ti substrate. The anti-osteosarcoma and antibacterial assay showed the delivered naringin and Zn²⁺ can induce a remarkable increase of oxidative stress in bacteria (Escherichia coli and Staphylococcus aureus) and osteosarcoma (Saos-2 cells) by producing reactive oxygen species (ROS). Accumulation of ROS results in damage of bacterial biofilm and bacterial membrane, leading to the leakage of bacterial RNA and DNA. Meanwhile, the increase of ROS induces osteosarcoma cell apoptosis by activating ROS/extracellular signal-regulated kinase signaling pathway. Furthermore, in vitro cellular experiments, including cell viability, alkaline phosphatase activity, collagen secretion, extracellular matrix mineralization level, indicated that the functional Ti substrate exhibited great potential for osteoblasts proliferation and differentiation. Hence, this study provides a simple and promising strategy of developing multifunctional Ti-based implants for the reconstruction of large bony after osteosarcoma resection.

Zn-incorporation with graphene oxide on Ti substrates surface to improve osteogenic activity and inhibit bacterial adhesion

The poor osseointegration and postoperative bacterial infection are prominently responsible for the failure of titanium (Ti)-based implant in clinic. To address above issues, methacryloyl modified graphene oxide (GOMA) as zinc ions (Zn²⁺ ) reservoir and release platform was fabricated on the Ti substrates with cathode electrophoresis deposition (EPD). Afterward, phenylboronic acid (PBA) functionalization methacryloyl-gelatin (GelMA-PBA) was reacting with GOMA through in situ free-radical polymerization to prepare GO-Zn/GelMA-PBA coating. The obtained coating was confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, and Zn ions release property, respectively. in vitro cellular experiments including cell activity, alkaline phosphatase, collagen secretion, extracellular matrix (ECM) mineralization, osteogenic genes and proteins, revealed that GO-Zn/GelMA-PBA coating was beneficial for enhancing the adhesion, proliferation, and differentiation of osteoblasts. The positive results were related to the existence of gelatin, formation of boronic ester between PBA groups, and carbohydrates of osteoblasts surface. Meanwhile, antibacterial assay against Staphylococcus aureus and Pseudomonas aeruginosa confirmed that GO-Zn/GelMA-PBA coating on Ti substrates had superior antibacterial capacity, availably inhibited the bacterial adhesion, and prevented formation of biofilm. Hence, the study provides a promising strategy for designing pro-osteogenesis and antibacterial coating on Ti substrates for orthopedic applications.