The Role of Surface Chemistry in the Osseointegration of PEEK Implants

Enhanced osteogenesis and antibacterial activity of dual-functional PEEK implants via biomimetic polydopamine modification with chondroitin sulfate and levofloxacin

Polyetheretherketone (PEEK) implants have emerged as a clinically favored alternative to titanium alloy implants for cranial bone substitutes due to their excellent mechanical properties and biocompatibility. However, the biological inertness of PEEK has hindered its clinical application. To address this issue, we developed a dual-functional surface modification method aimed at enhancing both osteogenesis and antibacterial activity, which was achieved through the sustained release of chondroitin sulfate (CS) and levofloxacin (LVFX) from a biomimetic polydopamine (PDA) coating on the PEEK surface. CS was introduced to promote cell adhesion and osteogenic differentiation. Meanwhile, incorporation of antibiotic LVFX was essential to prevent infections, which are a critical concern in bone defect repairing. To our delight, experiment results demonstrated that the SPKD/CS-LVFX specimen exhibited enhanced hydrophilicity and sustained drug release profiles. Furthermore, in vitro experiments showed that cell growth and adhesion, cell viability, and osteogenic differentiation of mouse calvaria-derived osteoblast precursor (MC3T3-E1) cells were significantly improved on the SPKD/CS-LVFX coating. Antibacterial assays also confirmed that the SPKD/CS-LVFX specimen effectively inhibited the growth of Escherichia coli and Staphylococcus aureus, attributable to the antibiotic LVFX released from the PDA coating. To sum up, this dual-functional PEEK implant showed a promising potential for clinical application in bone defects repairing, providing excellent osteogenic and antibacterial properties through a synergistic approach.

Surface bioactivation of Polyetheretherketone (PEEK) by magnesium chondroitin sulfate (MgCS) as orthopedic implants for reconstruction of skeletal defects

Polyether-ether-ketone (PEEK) is clinically used as a bio-implant for the healing of skeletal defects. However, the osseointegration of clinical-sized bone grafts remains limited. In this study, surface-porous PEEK was created by using a sulfonation method and a metal-polysaccharide complex MgCS was introduced on the surface of sulfonated PEEK to form MgCS@SPEEK. The as-prepared MgCS@SPEEK was found to have a porous surface with good hydrophilicity and bioactivity. This was followed by an investigation into whether MgCS loaded onto sulfonated PEEK surfaces could promote osseointegration and angiogenesis. The in vitro results showed that MgCS@SPEEK had a positive effect on reducing the expression levels of inflammatory genes and promoting osteogenesis and angiogenesis-related genes expression levels. Furthermore, porous MgCS@SPEEK was implanted in critical-sized rat tibial defects for in vivo evaluation of osseointegration. The micro-computed tomography evaluation results revealed substantial bone formation at 4 and 8 weeks. Collectively, these findings indicate that MgCS@SPEEK could provide improved osseointegration and an attractive strategy for orthopaedic applications.

Performance characterization and biocompatibility assessment of silicone polyurethanes for polymer heart valve applications

Silicone polyurethanes have gained widespread application in the biomedical field due to their excellent biocompatibility. This study comprehensively investigates four silicone polyurethane materials suitable for polymer heart valves, each exhibiting distinct chemical compositions and structural characteristics, leading to significant differences, particularly in mechanical performance and biocompatibility. Surface analysis reveals an elevated surface silicon element content in all materials compared to the bulk, indicating a migration of silicon elements towards the surface, providing a structural basis for enhancing biological stability and biocompatibility. However, higher silicon content leads to a decrease in mechanical performance, potentially resulting in mechanical failure and rupture in artificial heart valves. Concerning biocompatibility, an increase in silicone content diminishes the material's adsorption capability for cells and proteins, consequently improving its biocompatibility and biological stability. In summary, while high silicone content leads to a reduction in mechanical performance, the formation of a "silicon protective layer" on the material surface mitigates cell and protein adsorption, thereby enhancing biocompatibility and biological stability. Through comprehensive testing of the four silicone polyurethane materials, this study aims to provide insightful perspectives and methods for selecting materials suitable for polymer heart valves. Additionally, the thorough performance exploration of these materials serves as a crucial reference for the performance assessment and biocompatibility research of polymeric artificial heart valve materials.

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.

Biomimetic mineralization of platelet lysate/oxidized dextran cryogel as a macroporous 3D composite scaffold for bone repair

Scaffold development approaches using autologous sources for tissue repair are of great importance in obtaining bio-active/-compatible constructs. Platelet-rich plasma (PRP) containing various growth factors and platelet lysate (PL) derived from PRP are autologous products that have the potential to accelerate the tissue repair response by inducing a transient inflammatory event. Considering the regenerative capacity of PRP and PL, PRP/PL-based scaffolds are thought to hold great promise for tissue engineering as a natural source of autologous growth factors and a provider of mechanical support for cells. Here, a bio-mineralized PRP-based scaffold was developed using oxidized dextran (OD) and evaluated for future application in bone tissue engineering. Prepared PL/OD scaffolds were incubated in simulated body fluid (SBF) for 7, 14 and 21 d periods. Mineralized PL/OD scaffolds were characterized using Fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, porosity and compression tests. SEM and energy-dispersive x-ray spectroscopy analyses revealed mineral accumulation on the PL/OD scaffold as a result of SBF incubation.In vitrocytotoxicity andin vitrohemolysis tests revealed that the scaffolds were non-toxic and hemocompatible. Additionally, human osteoblasts (hOBs) exhibited good attachment and spreading behavior on the scaffolds and maintained their viability throughout the culture period. The alkaline phosphatase activity assay and calcium release results revealed that PL/OD scaffolds preserved the osteogenic properties of hOBs. Overall, findings suggest that mineralized PL/OD scaffold may be a promising scaffold for bone tissue engineering.

Latest advances: Improving the anti-inflammatory and immunomodulatory properties of PEEK materials

Excellent biocompatibility, mechanical properties, chemical stability, and elastic modulus close to bone tissue make polyetheretherketone (PEEK) a promising orthopedic implant material. However, biological inertness has hindered the clinical applications of PEEK. The immune responses and inflammatory reactions after implantation would interfere with the osteogenic process. Eventually, the proliferation of fibrous tissue and the formation of fibrous capsules would result in a loose connection between PEEK and bone, leading to implantation failure. Previous studies focused on improving the osteogenic properties and antibacterial ability of PEEK with various modification techniques. However, few studies have been conducted on the immunomodulatory capacity of PEEK. New clinical applications and advances in processing technology, research, and reports on the immunomodulatory capacity of PEEK have received increasing attention in recent years. Researchers have designed numerous modification techniques, including drug delivery systems, surface chemical modifications, and surface porous treatments, to modulate the post-implantation immune response to address the regulatory factors of the mechanism. These studies provide essential ideas and technical preconditions for the development and research of the next generation of PEEK biological implant materials. This paper summarizes the mechanism by which the immune response after PEEK implantation leads to fibrous capsule formation; it also focuses on modification techniques to improve the anti-inflammatory and immunomodulatory abilities of PEEK. We also discuss the limitations of the existing modification techniques and present the corresponding future perspectives.

Implant surface physicochemistry affects keratinocyte hemidesmosome formation

Previous studies have shown hydrophilic/hydrophobic implant surfaces stimulate/hinder osseointegration. An analogous concept was applied here using common biological functional groups on a model surface to promote oral keratinocytes (OKs) proliferation and hemidesmosomes (HD) to extend implant lifespans through increased soft tissue attachment. However, it is unclear what physicochemistry stimulates HDs. Thus, common biological functional groups (NH2 , OH, and CH3 ) were functionalized on glass using silanization. Non-functionalized plasma-cleaned glass and H silanization were controls. Surface modifications were confirmed with X-ray photoelectron spectroscopy and water contact angle. The amount of bovine serum albumin (BSA) and fibrinogen, and BSA thickness, were assessed to understand how adsorbed protein properties were influenced by physicochemistry and may influence HDs. OKs proliferation was measured, and HDs were quantified with immunofluorescence for collagen XVII and integrin β4. Plasma-cleaned surfaces were the most hydrophilic group overall, while CH3 was the most hydrophobic and OH was the most hydrophilic among functionalized groups. Modification with the OH chemical group showed the highest OKs proliferation and HD expression. The OKs response on OH surfaces appeared to not correlate to the amount or thickness of adsorbed model proteins. These results reveal relevant surface physicochemical features to favor HDs and improve implant soft tissue attachment.

Polyetheretherketone development in bone tissue engineering and orthopedic surgery

Polyetheretherketone (PEEK) has been widely used in the medical field as an implant material, especially in bone tissue engineering and orthopedic surgery, in recent years. This material exhibits superior stability at high temperatures and is biosecured without harmful reactions. However, the chemical and biological inertness of PEEK still limits its applications. Recently, many approaches have been applied to improve its performance, including the modulation of physical morphology, chemical composition and antimicrobial agents, which advanced the osteointegration as well as antibacterial properties of PEEK materials. Based on the evolution of PEEK biomedical devices, many studies on the use of PEEK implants in spine surgery, joint surgery and trauma repair have been performed in the past few years, in most of which PEEK implants show better outcomes than traditional metal implants. This paper summarizes recent studies on the modification and application of biomedical PEEK materials, which provides further research directions for PEEK implants.

Bone ECM-inspired biomineralization chitin whisker liquid crystal hydrogels for bone regeneration

As a particular cell niche, natural bone extracellular matrix (ECM) is an organic-inorganic composite material formed by mineralization of liquid crystal (LC) collagen fiber network. However, designing bone repair materials that highly imitate the LC characteristic and composite components of natural bone ECM is a great challenge. Here, we report a novel kind of bone ECM-inspired biomineralization chitin whisker LC hydrogels. First, photocurable chitin whisker LC hydrogels with bone ECM-like chiral nematic LC state and viscoelasticity are created. Next, biomineralization, guided by LC hydrogels, is carried out to truly mimic the mineralization process of natural bone, so as to obtain the organic-inorganic composite materials with bone ECM-like microenvironment. The chitin whisker LC hydrogels exhibit superior biomineralization, protein adsorption and osteogenesis ability, more importantly, LC hydrogel with negatively charged -COOH groups is more conducive to biomineralization and shows more desirable osteogenic activity than that with positively charged -NH₂ groups. Notably, compared with the pristine LC hydrogels, the biomineralization LC hydrogels display more favorable osteogenesis ability due to their bone ECM-like LC texture and bone-like hydroxyapatite. This study opens an avenue toward the design of bone ECM-inspired biomineralization chitin whisker LC hydrogels for bone regeneration.