Electroactive Biomaterials Regulate the Electrophysiological Microenvironment to Promote Bone and Cartilage Tissue Regeneration

The incidence of large bone and articular cartilage defects caused by traumatic injury is increasing worldwide; the tissue regeneration process for these injuries is lengthy due to limited self‐healing ability. Endogenous bioelectrical phenomenon has been well recognized to play an important role in bone and cartilage homeostasis and regeneration. Studies have reported that electrical stimulation (ES) can effectively regulate various biological processes and holds promise as an external intervention to enhance the synthesis of the extracellular matrix, thereby accelerating the process of bone and cartilage regeneration. Hence, electroactive biomaterials have been considered a biomimetic approach to ensure functional recovery by integrating various physiological signals, including electrical, biochemical, and mechanical signals. This review will discuss the role of endogenous bioelectricity in bone and cartilage tissue, as well as the effects of ES on cellular behaviors. Then, recent advances in electroactive materials and their applications in bone and cartilage tissue regeneration are systematically overviewed, with a focus on their advantages and disadvantages as tissue repair materials and performances in the modulation of cell fate. Finally, the significance of mimicking the electrophysiological microenvironment of target tissue is emphasized and future development challenges of electroactive biomaterials for bone and cartilage repair strategies are proposed.

A 3D-printed orthopedic implant with dual-effect synergy based on MoS2 and hydroxyapatite nanoparticles for tumor therapy and bone regeneration

Treatments for malignant bone tumors are urgently needed to be developed due to the dilemma of precise resection of tumor tissue and subsequent bone defects. Although polyether-ether-ketone (PEEK) has widely attracted attention in the orthopedic field, its bioinertness and poor osteogenic properties significantly restrict its applications in bone tumor treatment. To tackle the daunting issue, we use a hydrothermal technique to fabricate novel PEEK scaffolds modified with molybdenum disulfide (MoS₂) nanosheets and hydroxyapatite (HA) nanoparticles. Our dual-effect synergistic PEEK scaffolds exhibit perfect photothermal therapeutic (PTT) property dependent on molybdous ion (Mo²⁺) concentration and laser power density, superior to conventional PEEK scaffolds. Under near-infrared (NIR) irradiation, the viability of MG63 osteosarcoma cells is significantly reduced by modified PEEK scaffolds, indicating a tumor-killing potential in vitro. Furthermore, the incorporation of HA nanoparticles on the surface of PEEK bolsters proliferation and adherence of MC3T3-E1 cells, boosting mineralization for further bone defect repair. The results of micro-computed tomography (micro-CT) and histological analysis of 4-week treated rat femora demonstrate the preeminent photothermal and osteogenesis capacity of 3D-printed modified scaffolds in vivo. In conclusion, the dual-effect synergistic orthopedic implant with photothermal anticancer property and osteogenic induction activity strikes a balance between tumor treatment and bone development promotion, offering a promising future therapeutic option.

Bioactivity Enhancement of Plasma-Sprayed Hydroxyapatite Coatings through Non-Contact Corona Electrical Charging

Atmospheric plasma spray (APS) remains the only certified industrial process to produce hydroxyapatite (Hap) coatings on orthopaedic and dental implants intended for commercialization. Despite the established clinical success of Hap-coated implants, such as hip and knee arthroplasties, a concern is being raised regarding the failure and revision rates in younger patients, which are increasing rapidly worldwide. The lifetime risk of replacement for patients in the 50-60 age interval is about 35%, which is significantly higher than 5% for patients aged 70 or older. Improved implants targeted at younger patients are a necessity that experts have been alerted to. One approach is to enhance their bioactivity. For this purpose, the method with the most outstanding biological results is the electrical polarization of Hap, which remarkably accelerates implant osteointegration. There is, however, the technical challenge of charging the coatings. Although this is straightforward on bulk samples with planar faces, it is not easy on coatings, and there are several problems regarding the application of electrodes. To the best of our knowledge, this study demonstrates, for the first time, the electrical charging of APS Hap coatings using a non-contact, electrode-free method: corona charging. Bioactivity enhancement is observed, establishing the promising potential of corona charging in orthopedics and dental implantology. It is found that the coatings can store charge at the surface and bulk levels up to high surface potentials (>1000 V). The biological in vitro results show higher Ca²⁺ and P⁵⁺ intakes in charged coatings compared to non-charged coatings. Moreover, a higher osteoblastic cellular proliferation is promoted in the charged coatings, indicating the promising potential of corona-charged coatings when applied in orthopedics and dental implantology.

Development and Processing of New Composite Materials Based on High-Performance Semicrystalline Polyimide for Fused Filament Fabrication (FFF) and Their Biocompatibility

Samples of composite materials based on high-performance semicrystalline polyimide R-BAPB (based on the dianhydride R: 1,3-bis-(3′,4,-dicarboxyphenoxy)benzene and diamine BAPB: 4,4′-bis-(4″-aminophenoxy)diphenyl)) filled with carbon nanofibers and micron-sized discrete carbon fibers were obtained by FFF printing for the first time. The viscosity of melts of the composites based on R-BAPB, thermal, mechanical characteristics of the obtained composite samples, their internal structure, and biocompatibility were studied. Simultaneously with FFF printing, samples were obtained by injection molding. The optimal concentrations of carbon fillers in polyimide R-BAPB for their further use in FFF printing were determined. The effect of the incorporation of carbon fillers on the porosity of the printed samples was investigated. It was shown that the incorporation of carbon nanofibers reduces the porosity of the printed samples, which leads to an increase in deformation at break. Modification of polyimide with discrete carbon fibers increases the strength and Young’s modulus sufficiently but decreases the deformation at break. The cytotoxicity analysis showed that the obtained composite materials are bioinert.

Effect of Processing Temperature and the Content of Carbon Nanotubes on the Properties of Nanocomposites Based on Polyphenylene Sulfide

The study aimed to investigate the effect of processing temperature and the content of multi-wall carbon nanotubes (MWCNTs) on the rheological, thermal, and electrical properties of polyphenylene sulfide (PPS)/MWCNT nanocomposites. It was observed that the increase in MWCNT content influenced the increase of the complex viscosity, storage modulus, and loss modulus. The microscopic observations showed that with an increase in the amount of MWCNTs, the areal ratio of their agglomerates decreases. Thermogravimetric analysis showed no effect of processing temperature and MWCNT content on thermal stability; however, an increase in stability was observed as compared to neat PPS. The differential scanning calorimetry was used to assess the influence of MWCNT addition on the crystallization phenomenon of PPS. The calorimetry showed that with increasing MWCNT content, the degree of crystallinity and crystallization temperature rises. Thermal diffusivity tests proved that with an increase in the processing temperature and the content of MWCNTs, the diffusivity also increases and declines at higher testing temperatures. The resistivity measurements showed that the conductivity of the PPS/MWCNT nanocomposite increases with the increase in MWCNT content. The processing temperature did not affect resistivity.

Tribological, cytotoxicity and antibacterial properties of graphene oxide/carbon fibers/polyetheretherketone composite coatings on Ti-6Al-4V alloy as orthopedic/dental implants

In this work, graphene oxide/carbon fibers/polyetheretherketone (GO/CF/PEEK) composite coatings on Ti-6Al-4V (TC4) alloy were fabricated by electrostatic powder spraying method. The coatings with 0.02 wt% GO and 25 wt% CF were made to improve the wear resistance, cytocompatibility and antibacterial properties of the TC4 as orthopedic/dental implants. The physicochemical properties involving coating thickness, Vickers hardness, micromorphology, phase structures and contact angles were investigated. The results indicated that the GO/CF/PEEK coatings can significantly decrease the coefficient of friction (COF) (from 0.433 ± 0.017 to 0.085 ± 0.008) and enhance the wear resistance of TC4 alloy during the wet friction process in sliding contact with a Si₃N₄ ball. The results showed that few scratches appeared on the GO/CF/PEEK coating. As the in vitro cytotoxicity test by murine fibroblast L929 cells shown, the GO/CF/PEEK coating revealed good cytocompatibility. More importantly, GO/CF/PEEK coating exhibited excellent suppression toward Staphylococcus aureus (S. aureus) owing to the antibacterial nature of GO. Therefore, the GO/CF/PEEK composite coated TC4 could be considered as a prospective orthopedic/dental implant material for bone tissue engineering.

Detection and Imaging of Damages and Defects in Fibre-Reinforced Composites by Magnetic Resonance Technique

Defectively manufactured and deliberately damaged composite laminates fabricated with different continuous reinforcing fibres (respectively, carbon and glass) and polymer matrices (respectively, thermoset and thermoplastic) were inspected in magnetic resonance imaging equipment. Two pulse sequences were evaluated during non-destructive examination conducted in saline solution-immersed samples to simulate load-bearing orthopaedic implants permanently in contact with biofluids. The orientation, positioning, shape, and especially the size of translaminar and delamination fractures were determined according to stringent structural assessment criteria. The spatial distribution, shape, and contours of water-filled voids were sufficiently delineated to infer the amount of absorbed water if thinner image slices than this study were used. The surface texture of composite specimens featuring roughness, waviness, indentation, crushing, and scratches was outlined, with fortuitous artefacts not impairing the image quality and interpretation. Low electromagnetic shielding glass fibres delivered the highest, while electrically conductive carbon fibres produced the poorest quality images, particularly when blended with thermoplastic polymer, though reliable image interpretation was still attainable.

Ag and peptide co-decorate polyetheretherketone to enhance antibacterial property and osteogenic differentiation

Polyetheretherketone (PEEK) has been well concerned as a promising material for hard tissue repair because of its outstanding mechanical behavior and superior biocompatibility. However, its clinical application is limited by its biological inertness and the susceptibility to bacterial infection during implantation. To improve the original shortcomings, self-polymerized dopamine (PDA) was used to enrich silver ions on the PEEK surface. Moreover, a layer of carboxymethyl chitosan (CMC) film was formed on the PEEK surface by the spin-coating method, aiming to control the release of silver ions on the surface. At the same time, bone forming peptide (BFP) was modified onto the PEEK surface by 1-(3-dimethylaminopropyl)-3-ethylcarbonimide hydrochloride (EDC) / N-hydroxy succinimide (NHS). The characterization results showed that PEEK-Ag-CMC-BFP could be obtained successfully. The inhibition zone and bacterial kinetic curve showed a favorable inhibitory effect of the sliver-modified PEEK on gram-negative and gram-positive bacteria. In vitro experiments exhibited that PEEK-Ag-CMC-BFP had a better biological activity than that of PEEK, which could promote cell proliferation and osteogenic differentiation. It is expected that this dual-function material with antibacterial and bone-promoting properties has a vast potential applied in the field of hard tissue repair.

Electroactive poly (p-phenylene sulfide)/r-graphene oxide/chitosan as a novel potential candidate for tissue engineering

Designing novel biomaterials for tissue engineering purpose is an obvious necessary considering ever increasing need for appropriate biocompatibility and properties to achieve the maximum regeneration. In this research, a new type of biomaterial based on poly (phenylene sulfide) (PPS) and reduced graphene oxide (rGO) was synthesized and applied within chitosan based hydrogel to evaluate its performance as a wound dressing potentially. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM) and compression tests were performed to assess suitability of composite biomaterial. Thermal behavior of the PPS/rGO composite was evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The PPS/rGO composition of 90: 10 (w/w) was selected because of having the highest biocompatibility and utilized in chitosan hydrogel. Chitosan hydrogel swelling ratio was declined from 800 to 200% by PPS/rGO addition; likewise, water vapor transition rate (WVTR) was dropped. A proper biocompatibility and cell attachment was confirmed, where porosity of ca. 80% appeared promising for tissue engineering uses. Overall, the result confirmed the appropriateness of PPS/rGO for tissue engineering uses.

From Dermal Patch to Implants-Applications of Biocomposites in Living Tissues

Composites are composed of two or more materials, displaying enhanced performance and superior mechanical properties when compared to their individual components. The use of biocompatible materials has created a new category of biocomposites. Biocomposites can be applied to living tissues due to low toxicity, biodegradability and high biocompatibility. This review summarizes recent applications of biocomposite materials in the field of biomedical engineering, focusing on four areas-bone regeneration, orthopedic/dental implants, wound healing and tissue engineering.

Design, synthesis and characterization of hydroxyapatite-chitosan nanocomposite radiolabelled with 153Sm as radiopharmaceutical for use in radiosynovectomy

The aim of the present study was to introduction of hydroxyapatite/chitosan nanocomposite as a new radiosynovectomy agent with excellent properties. In this work, the nanocomposite was prepared through a reliable method and characterized using different techniques to elucidate its chemical structure and physiochemical properties. The prepared nanocomposite was successfully radiolabeled with 153Sm under optimal conditions and with high radiolabelling yield (99 %). The radiochemical purity of the prepared radiopharmaceutical was found to be >99 % as determined by ITLC technique. In vitro stability studies in saline solution and in human serum showed that the radiolabeled nanocomposite retained its stability for at least 6 days. The biodistribution and imaging studies in wild-type rats revealed high retention of the agent into the synovial joints of the knee even at 96 h post-injection, thereby indicating excellent in vivo stability of 153Sm labeled hydroxyapatite-chitosan nanocomposite. Therefore, the prepared radiopharmaceutical would be a potential therapeutic agent for use in radiosynovectomy procedure.

Fe/Zn-modified tricalcium phosphate (TCP) biomaterials: preparation and biological properties

Bone repairing materials play an essential role in the repair treatment of bone defects. The presence of calcium phosphate invertebrates is of significance for bone repairing processes. However, the mechanical properties and osteogenic activities of many current calcium phosphate materials are not ideal, which limit their biological applications. Therefore, it is an effective alternative strategy to study the modification of calcium phosphate biomaterials to address these limitations. In this research, in order to enhance the biological performance of tricalcium phosphate (β-TCP), metal species (Fe and Zn) modified β-TCP materials through the co-precipitation method were successfully developed. The physical, chemical and biological properties of the binary composites were carefully studied for the first time. The bioactivities of the Fe-TCP and Zn-TCP were evaluated by simulating body fluid (SBF) immersion experiments, blood compatibility, and cytotoxicity tests. The findings demonstrated that the metal-TCP with excellent cytocompatibility and osteogenic properties shows good potential in medical applications.

Fe/Zn-TCP biomaterials were prepared and their bioactivities to enhance the synthetic bone-repair materials were studied in comparison.

Comparing hydroxyapatite with osteogenic medium for the osteogenic differentiation of mesenchymal stem cells on PHBV nanofibrous scaffolds

Having advantageous biocompatibility and osteoconductive properties known to enhance the osteogenic differentiation of mesenchymal stem cells (MSCs), hydroxyapatite (HA) is a commonly used material for bone tissue engineering. What remains unclear, however, is whether HA holds a similar potential for stimulating the osteogenic differentiation of MSCs to that of a more frequently used osteogenic-inducing medium (OIM). To that end, we used PHBV electrospun nanofibrous scaffolds to directly compare the osteogenic capacities of HA with OIM over MSCs. Through the observation of cellular morphology, the staining of osteogenic markers, and the quantitative measuring of osteogenic-related genes, as well as microRNA analyses, we not only found that HA was as capable as OIM for differentiating MSCs down an osteogenic lineage; albeit, at a significantly slower rate, but also that numerous microRNAs are involved in the osteogenic differentiation of MSCs through multiple pathways involving the inhibition of cellular proliferation and stemness, chondrogenesis and adipogenesis, and the active promotion of osteogenesis. Taken together, we have shown for the first time that PHBV electrospun nanofibrous scaffolds combined with HA have a similar osteogenic-inducing potential as OIM and may therefore be used as a viable replacement for OIM for alternative in vivo-mimicking bone tissue engineering applications.

Mechanical properties and cytotoxicity of hierarchical carbon fiber-reinforced poly (ether-ether-ketone) composites used as implant materials

Weak mechanical properties affect the application of PEEK as an implant. Carbon fiber (CFR) reinforcement provides an excellent solution to improve the mechanical strength of PEEK and to provide perfect matching of elastic modulus between CFR-PEEK composites and human bone. To investigate the effect of carbon fiber content on the mechanical, thermal properties and cytotoxicity of CFR reinforced PEEK composites, a series of CFR-PEEK composites with different carbon fiber content (25 wt%, 30 wt%, 35 wt%, 40 wt%) was prepared in this work. Thermal decomposition behavior and melting temperature were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. Subsequently, mechanical properties including bending strength, compressive strength, impact strength and hardness were tested respectively. Afterwards, the fracture morphology of the bending test samples was observed by scanning electron microscopy (SEM). In addition, murine fibroblast L929 cells were adopted for cytotoxicity test by CCK-8 assay in vitro, and the morphology of cells was observed by inverted fluorescence microscope simultaneously, cell compatibility of CFR-PEEK composites was tested.

Synergistic combination of natural bioadhesive bael fruit gum and chitosan/nano-hydroxyapatite: A ternary bioactive nanohybrid for bone tissue engineering

In this work, we have explored the polysaccharide nature of bael fruit gum (BFG) motivated from the current findings about the substantial role of the polysaccharides in bone tissue engineering. The nanocomposite scaffold (CSH-BFG) was prepared by blending BFG, nano-hydroxyapatite (n-HA) and chitosan (CS) by co-precipitation approach and compared with n-HA and CS binary system (CSH). The analysis of different properties was carried out by SEM, TEM, FTIR, XRD and mechanical testing. The CSH-BFG scaffolds revealed a rough morphology and uniform distribution of particles along with strong chemical interactions among different components compared to the CSH scaffold. The incorporation of BFG in the scaffold resulted in significant increase of the compressive strength, compressive modulus, protein adsorption, biodegradation and swelling behaviour. The ternary system exhibited superior antibacterial activity against different bacterial pathogens compared to the binary system. The in vitro biomineralization ability was elucidated from the formation of thick apatite layer complementing the result of ARS study in the CSH-BFG nanocomposite. Our findings also revealed that BFG reinforced CSH nanocomposite exhibited enhanced cell adhesion and proliferation, osteogenic differentiation along with phenomenal cytocompatibility. Overall, our results signified that the fabricated CSH-BFG nanocomposite carries enormous potential to be applied in the bone remodelling procedures.

Effect of reaction solvent on hydroxyapatite synthesis in sol-gel process

Synthesis of hydroxyapatite (HA) through sol-gel process in different solvent systems is reported. Calcium nitrate tetrahydrate (CNTH) and diammonium hydrogen phosphate (DAHP) were used as calcium and phosphorus precursors, respectively. Three different synthesis reactions were carried out by changing the solvent media, while keeping all other process parameters constant. A measure of 0.5 M aqueous DAHP solution was used in all reactions while CNTH was dissolved in distilled water, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) at a concentration of 0.5 M. Ammonia solution (28-30%) was used to maintain the pH of the reaction mixtures in the 10-12 range. All reactions were carried out at 40 ± 2°C for 4 h. Upon completion of the reactions, products were filtered, washed and calcined at 500°C for 2 h. It was clearly demonstrated through various techniques that the dielectric constant and polarity of the solvent mixture strongly influence the chemical structure and morphological properties of calcium phosphate synthesized. Water-based reaction medium, with highest dielectric constant, mainly produced β-calcium pyrophosphate (β-CPF) with a minor amount of HA. DMF/water system yielded HA as the major phase with a very minor amount of β-CPF. THF/water solvent system with the lowest dielectric constant resulted in the formation of pure HA.