Facile and Versatile Surface Functional Polyetheretherketone with Enhanced Bacteriostasis and Osseointegrative Capability for Implant Application

Functionalized BP@(Zn+Ag)/EPLA Nanofibrous Scaffolds Fabricated by Cryogenic 3D Printing for Bone Tissue Engineering

This study fabricates a functionalized scaffold by cryogenic three-dimensional (3D) printing using an aminated poly-L-lactic acid (EPLA) solution containing nanosilver/zinc-coated black phosphorus (BP@(Zn+Ag)) nanocomposites. The nanocomposites are prepared by a green method of in situ photodeposition of silver and zinc nanoparticles (AgNPs and ZnNPs) on BP nanosheets (BPNs) under visible light irradiation without any chemical reductant. Scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS) confirm the uniform distribution of BP@(Zn+Ag) nanoparticles in the EPLA nanofibrous matrix. The in vitro tests show that the fabricated BP@(Zn+Ag)/EPLA nanofibrous scaffold exhibits excellent antibacterial activity (over 96%) against E. coli and S. aureus, as well as enhanced cell viability and osteogenic activity to facilitate the growth and differentiation of osteoblasts. The in vivo rat calvarial defect model also demonstrates that the BP@(Zn+Ag)/EPLA nanofibrous scaffold promotes new bone tissue formation around the implant site. Therefore, the prepared multifunctional 3D printed BP@(Zn+Ag)/EPLA nanofibrous scaffold has great potential for bone tissue engineering (BTE) applications.

Strategies to improve the performance of polyetheretherketone (PEEK) as orthopedic implants: from surface modification to addition of bioactive materials

Polyetheretherketone (PEEK), as a high-performance polymer, is widely used for bone defect repair due to its homogeneous modulus of elasticity of human bone, good biocompatibility, excellent chemical stability and projectability. However, the highly hydrophobic surface of PEEK is biologically inert, which makes it difficult for cells and proteins to attach, and is accompanied by the development of infections that ultimately lead to failure of PEEK implants. In order to further enhance the potential of PEEK as an orthopedic implant, researchers have explored modification methods such as surface modification by physical and chemical means and the addition of bioactive substances to PEEK-based materials to enhance the mechanical properties, osteogenic activity and antimicrobial properties of PEEK. However, these current modification methods still have obvious shortcomings in terms of cost, maneuverability, stability and cytotoxicity, which still need to be explored by researchers. This paper reviews some of the modification methods that have been used to improve the performance of PEEK over the last three years in anticipation of the need for researchers to design PEEK orthopedic implants that better meet clinical needs.

Antimicrobial peptides in bone regeneration: mechanism and potential

INTRODUCTION

Antimicrobial peptides (AMPs) are small-molecule peptides with a unique antimicrobial mechanism. Other notable biological activities of AMPs, including anti-inflammatory, angiogenesis, and bone formation effects, have recently received widespread attention. These remarkable bioactivities, combined with the unique antimicrobial mechanism of action of AMPs, have led to their increasingly important role in bone regeneration.

AREAS COVERED

In this review, on the one hand, we aimed to summarize information about the AMPs that are currently used for bone regeneration by reviewing published literature in the PubMed database. On the other hand, we also highlight some AMPs with potential roles in bone regeneration and their possible mechanisms of action.

EXPERT OPINION

The translation of AMPs to the clinic still faces many problems, but their unique antimicrobial mechanisms and other conspicuous biological activities suggest great potential. An in-depth understanding of the structure and mechanism of action of AMPs will help us to subsequently combine AMPs with different carrier systems and perform structural modifications to reduce toxicity and achieve stable release, which may be a key strategy for facilitating the translation of AMPs to the clinic.

Synergistic Effect of Nano Strontium Titanate Coating and Ultraviolet C Photofunctionalization on Osteogenic Performance and Soft Tissue Sealing of poly(ether-ether-ketone)

This study aimed to evaluate the bioactivity of poly(ether ether ketone) (PEEK) after surface modification by persistent photoconductive strontium titanate (SrTiO3) magnetron sputtering and ultraviolet (UV) C irradiation. According to the different modifications, the PEEK specimens were randomly divided into five groups (n = 38/group): PEEK, Sr100-PEEK, Sr200-PEEK, UV/PEEK, and UV/Sr200-PEEK. Then, the specimens of Sr100-PEEK and Sr200-PEEK groups were, respectively, coated with 100 and 200 nm thickness photocatalyst SrTiO3 on the PEEK surface by magnetron sputtering. Subsequently, UV-C light photofunctionalized the specimens of PEEK and Sr200-PEEK groups to form UV/PEEK and UV/Sr200-PEEK groups. The specimens were characterized by a step meter, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and a water contact angle meter. The release test of the Sr ion was performed by inductively coupled plasma mass spectrometry (ICP-MS). In vitro study, osteogenic activity (MC3T3-E1 osteoblast-like cells) and epithelial and connective tissue attachment (gingival epithelial cells GE1 and fibroblasts NIH3T3) were analyzed in five groups. Surface morphology of the specimens was changed after coating, and the Sr content on the Sr-PEEK surface was increased with increasing coating thickness. In addition, the contact angle was increased significantly after magnetron sputtering. After UV-C photofunctionalization, the content of surface elements changed and the contact angle was decreased. The release of Sr ion was sustained, and the final cumulative release amount did not exceed the safety limit. In vitro experiments showed that SrTiO3 improved the cell activity of MC3T3-E1 and UV-C irradiation further enhanced the osteogenic performance of PEEK. Besides, UV-C irradiation also significantly promoted the cell viability, development, and expression of adhesion proteins of GE1 and NIH3T3 on PEEK. The present investigation demonstrated that nano SrTiO3 coating with UV-C photofunctionalization synergistically enhanced the osteogenic properties and soft tissue sealing function of PEEK in vitro.

Peptide-Based Biomaterials for Bone and Cartilage Regeneration

The healing of osteochondral defects (OCDs) that result from injury, osteochondritis, or osteoarthritis and bear lesions in the cartilage and bone, pain, and loss of joint function in middle- and old-age individuals presents challenges to clinical practitioners because of non-regenerative cartilage and the limitations of current therapies. Bioactive peptide-based osteochondral (OC) tissue regeneration is becoming more popular because it does not have the immunogenicity, misfolding, or denaturation problems associated with original proteins. Periodically, reviews are published on the regeneration of bone and cartilage separately; however, none of them addressed the simultaneous healing of these tissues in the complicated heterogeneous environment of the osteochondral (OC) interface. As regulators of cell adhesion, proliferation, differentiation, angiogenesis, immunomodulation, and antibacterial activity, potential therapeutic strategies for OCDs utilizing bone and cartilage-specific peptides should be examined and investigated. The main goal of this review was to study how they contribute to the healing of OCDs, either alone or in conjunction with other peptides and biomaterials.

Photoelectrons Sequentially Regulate Antibacterial Activity and Osseointegration of Titanium Implants

Titanium implants are widely used ; however, implantation occasionally fails due to infections during the surgery or poor osseointegration after the surgery. To solve the problem, an intelligent functional surface on titanium implant that can sequentially eradicate bacteria biofilm at the initial period and promote osseointegration at the late period of post-surgery time is designed. Such surfaces can be excited by near infrared light (NIR), with rare earth nanoparticles to upconvert the NIR light to visible range and adsorb by Au nanoparticles, supported by titanium oxide porous film on titanium implants. Under NIR irradiation, the implant converts the energy of phonon to hot electrons and lattice vibrations, while the former flows directly to the contact substance or partially reacts with the surrounding to generate reactive oxygen species, and the latter leads to the local temperature increase. The biofilm or microbes on the implant surface can be eradicated by NIR treatment in vitro and in vivo. Additionally, the surface exhibits superior biocompatibility for cell survival, adhesion, proliferation, and osteogenic differentiation, which provides the foundation for osseointegration. In vivo implantation experiments demonstrate osseointegration is also promoted. This work thus demonstrates NIR-generated electrons can sequentially eradicate biofilms and regulate the osteogenic process, providing new solutions to fabricate efficient implant surfaces.

Surface Treatments of PEEK for Osseointegration to Bone

Polymers, in general, and Poly (Ether-Ether-Ketone) (PEEK) have emerged as potential alternatives to conventional osseous implant biomaterials. Due to its distinct advantages over metallic implants, PEEK has been gaining increasing attention as a prime candidate for orthopaedic and dental implants. However, PEEK has a highly hydrophobic and bioinert surface that attenuates the differentiation and proliferation of osteoblasts and leads to implant failure. Several improvements have been made to the osseointegration potential of PEEK, which can be classified into three main categories: (1) surface functionalization with bioactive agents by physical or chemical means; (2) incorporation of bioactive materials either as surface coatings or as composites; and (3) construction of three-dimensionally porous structures on its surfaces. The physical treatments, such as plasma treatments of various elements, accelerated neutron beams, or conventional techniques like sandblasting and laser or ultraviolet radiation, change the micro-geometry of the implant surface. The chemical treatments change the surface composition of PEEK and should be titrated at the time of exposure. The implant surface can be incorporated with a bioactive material that should be selected following the desired use, loading condition, and antimicrobial load around the implant. For optimal results, a combination of the methods above is utilized to compensate for the limitations of individual methods. This review summarizes these methods and their combinations for optimizing the surface of PEEK for utilization as an implanted biomaterial.

Avicularin alleviates osteoporosis-induced implant loosening by attenuating macrophage M1 polarization via its inhibitory effect on the activation of NF-κB

Currently, the failure rate for internal fixation in patients with osteoporosis can be reduced by antiosteoporosis therapy alone. However, the administration of anti-osteoporotic drugs is not a complete solution. Therefore, it is necessary to investigate other causes of surgical failure, such as inflammation. In recent years, the inflammation caused by macrophage M1 polarization has garnered wide attention. The purpose of this research is to explore the inhibitory effect of avicularin (AL) on macrophage M1 polarization, by which it ameliorates inflammation, thus alleviating implant instability. We established an osteoporosis mouse model of implant loosening. The mouse tissues were taken out for morphological analysis, staining analysis and bone metabolic index analysis. In in vitro experiments, bone marrow derived macrophages (BMDM) and RAW264.7 cells were polarized to M1 macrophages using lipopolysaccharide (LPS), and analyzed by immunofluorescence (IF) staining, Western blot (WB) and flow cytometry. WB was also used to analyze the nuclear factor kappa-B (NF-κB) pathway. In addition, the expression levels of inflammatory cytokines were detected in cell supernatant using ELISA kits. Through observation of this experiments, we found that AL can inhibit M1 polarization of macrophages. Moreover, it can significantly inhibit the release of inflammatory factors to improve multiple mouse femur parameters. Furthermore, AL inhibited the phosphorylation of IKBα and P65 in the NF-κB pathway. The above data indicate that AL ameliorates inflammatory responses by inhibiting macrophage M1 polarization via its inhibitory effect on the NF-κB pathway, thus alleviating the instability of implants in mice with osteoporosis.

Antimicrobial peptides for bone tissue engineering: Diversity, effects and applications

Bone tissue engineering has been becoming a promising strategy for surgical bone repair, but the risk of infection during trauma repair remains a problematic health concern worldwide, especially for fracture and infection-caused bone defects. Conventional antibiotics fail to effectively prevent or treat bone infections during bone defect repair because of drug-resistance and recurrence, so novel antibacterial agents with limited resistance are highly needed for bone tissue engineering. Antimicrobial peptides (AMPs) characterized by cationic, hydrophobic and amphipathic properties show great promise to be used as next-generation antibiotics which rarely induce resistance and show potent antibacterial efficacy. In this review, four common structures of AMPs (helix-based, sheet-based, coil-based and composite) and related modifications are presented to identify AMPs and design novel analogs. Then, potential effects of AMPs for bone infection during bone repair are explored, including bactericidal activity, anti-biofilm, immunomodulation and regenerative properties. Moreover, we present distinctive applications of AMPs for topical bone repair, which can be either used by delivery system (surface immobilization, nanoparticles and hydrogels) or used in gene therapy. Finally, future prospects and ongoing challenges are discussed.

Biofunctionalization of 3D Printed Porous Tantalum Using a Vancomycin-Carboxymethyl Chitosan Composite Coating to Improve Osteogenesis and Antibiofilm Properties

3D-printed porous tantalum scaffold has been increasingly used in arthroplasty due to its bone-matching elastic modulus and good osteoinductive ability. However, the lack of antibacterial ability makes it difficult for tantalum to prevent the occurrence and development of periprosthetic joint infection. The difficulty and high cost of curing periprosthetic joint infection (PJI) and revision surgery limit the further clinical application of tantalum. Therefore, we fabricated vancomycin-loaded porous tantalum scaffolds by combining the chemical grafting of (3-aminopropyl)triethoxysilane (APTES) and the electrostatic assembly of carboxymethyl chitosan and vancomycin for the first time. Our in vitro experiments show that the scaffold achieves rapid killing of initially adherent bacteria and effectively prevents biofilm formation. In addition, our modification preserves the original excellent structure and biocompatibility of porous tantalum and promotes the generation of mineralized matrix and osteogenesis-related gene expression by mesenchymal stem cells on the surface of scaffolds. Through a rat subcutaneous infection model, the composite bioscaffold shows efficient bacterial clearance and inflammation control in soft tissue and creates an immune microenvironment suitable for tissue repair at an early stage. Combined with the economic friendliness and practicality of its preparation, this scaffold has great clinical application potential in the treatment of periprosthetic joint infection.

Treatment methods toward improving the anti-infection ability of poly(etheretherketone) implants for medical applications

Due to its favorable chemical stability, biocompatibility, and mechanical properties, Poly(etheretherketone) (PEEK) is a promising material for repairing bone and dental hard tissue defects. However, there are critical disadvantages: PEEK is biologically and chemically inert, which influences osseointegration of implants and bonding strength of prostheses, and its mechanical properties still cannot meet the requirements for some medical applications. Furthermore, bacterial infections and inflammatory reactions often accompany bone defects caused by trauma or inflammation or teeth loss caused by periodontitis. Previous studies mainly focused on enhancing PEEK's bioactivity and mechanical performance, but PEEK also lacks effective anti-infection ability. Thus, it is necessary to improve its anti-infection ability, and this is considered in this paper from two aspects. The first is to inhibit the attachment and growth of bacteria on the material, and the second is to endow the material with immunoregulatory ability, which means mobilizing the host immune system to protect tissue from inflammation. In this review, we analyze and discuss the existing treatment methods to improve the antibacterial and immunomodulatory abilities of PEEK addressing their limitations, relevant future challenges, and required research efforts.

Application of biomolecules modification strategies on PEEK and its composites for osteogenesis and antibacterial properties

As orthopedic and dental implants, polyetheretherketone (PEEK) is expected to be a common substitute material of titanium (Ti) and its alloys due to its good biocompatibility, chemical stability, and elastic modulus close to that of bone tissue. It could avoid metal allergy and bone resorption caused by the stress shielding effect of Ti implants, widely studied in the medical field. However, the lack of biological activity is not conducive to the clinical application of PEEK implants. Therefore, the surface modification of PEEK has increasingly become one of the research hotspots. Researchers have explored various biomolecules modification methods to effectively enhance the osteogenic and antibacterial activities of PEEK and its composites. Therefore, this review mainly summarizes the recent research of PEEK modified by biomolecules and discusses the further research directions to promote the clinical transformation of PEEK implants.

Improving bactericidal performance of implant composite coatings by synergism between Melittin and tetracycline

Methicillin resistance Staphylococcus aureus bacteria (MRSA) are serious hazards of bone implants. The present study was aimed to use the potential synergistic effects of Melittin and tetracycline to prevent MRSA associated bone implant infection. Chitosan/bioactive glass nanoparticles/tetracycline composite coatings were deposited on hydrothermally etched titanium substrate. Melittin was then coated on composite coatings by drop casting method. The surfaces were analyzed by FTIR, XRD, and SEM instruments. Tetracycline in coatings revealed multifunctional behaviors include bone regeneration and antibacterial activity. Releasing ALP enzyme from MC3T3 cells increased by tetracycline, so it is suitable candidate as osteoinductive and antibacterial agent in orthopedic implants coatings. Melittin increased the proliferation of MC3T3 cells. Composite coatings with combination of tetracycline and Melittin eradicate all MRSA bacteria, while coatings with one of them could no t eradicate all of the bacteria. In conclusion, chitosan/bioactive glass/tetracycline/Melittin coating can be suggested as a multifunctional bone implant coating because of its osteogenic and promising antibacterial activity. Graphical abstract.

Approaches to Biofunctionalize Polyetheretherketone for Antibacterial: A Review

Due to excellent mechanical properties and similar elastic modulus compared with human cortical bone, polyetheretherketone (PEEK) has become one of the most promising orthopedic implant materials. However, implant-associated infections (IAIs) remain a challenging issue since PEEK is bio-inert. In order to fabricate an antibacterial bio-functional surface, modifications of PEEK had been widely investigated. This review summarizes the modification strategies to biofunctionalize PEEK for antibacterial. We will begin with reviewing different approaches, such as surface-coating modifications and controlled release of antimicrobials. Furthermore, blending modifications and 3D printing technology were discussed. Finally, we compare the effects among different approaches. We aimed to provide an in-depth understanding of the antibacterial modification and optimize the design of the PEEK orthopedic implant.

Regulating Macrophage Polarization in High Glucose Microenvironment Using Lithium-Modified Bioglass-Hydrogel for Diabetic Bone Regeneration

Diabetes mellitus is a chronic metabolic disease with a proinflammatory microenvironment, causing poor vascularization and bone regeneration. Due to the lack of effective therapy and one-sided focus on the direct angiogenic properties of biomaterials and osteogenesis stimulation, the treatment of diabetic bone defect remains challenging and complex. In this study, using gelatin methacryloyl (GelMA) as a template, a lithium (Li) -modified bioglass-hydrogel for diabetic bone regeneration is developed. It exhibits a sustained ion release for better bone regeneration under diabetic microenvironment. The hydrogel is shown to be mechanically adaptable to the complex shape of the defect. In vitro, Li-modified bioglass-hydrogel promoted cell proliferation, direct osteogenesis, and regulated macrophages in high glucose (HG) microenvironment, with the secretion of bone morphogenetic protein-2 and vascular endothelial growth factor to stimulate osteogenesis and neovascularization indirectly. In vivo, composite hydrogels containing GelMA and Li-MBG (GM/M-Li) release Li ions to relieve inflammation, providing an anti-inflammatory microenvironment for osteogenesis and angiogenesis. Applying Li-modified bioglass-hydrogel, significantly enhances bone regeneration in a diabetic rat bone defect. Together, both remarkable in vitro and in vivo outcomes in this study present an opportunity for diabetic bone regeneration on the basis of HG microenvironment.