Hydroxyapatite-filled osteoinductive and piezoelectric nanofibers for bone tissue engineering

Unidirectional Polyvinylidene/Copper-Impregnated Nanohydroxyapatite Composite Membrane Prepared by Electrospinning with Piezoelectricity and Biocompatibility for Potential Ligament Repair

Ligament tears can strongly influence an individual's daily life and ability to engage in physical activities. It is essential to develop artificial scaffolds for ligament repairs in order to effectively restore damaged ligaments. In this experiment, the objective was to evaluate fibrous membranes as scaffolds for ligament repair. These membranes were created through electrospinning using piezoelectric polyvinylidene fluoride (PVDF) composites, which contained 1 wt.% and 3 wt.% of copper-impregnated nanohydroxyapatite (Cu-nHA). The proposed electrospun membrane would feature an aligned fiber structure achieved through high-speed roller stretching, which mimics the properties of biomimetic ligaments. Nanoparticles of Cu-nHA had been composited into PVDF to enhance the pirzoelectric β-phase of the PVDF crystallines. The study assessed the physicochemical properties, antibacterial activity, and biocompatibility of the membranes in vitro. A microstructure analysis revealed that the composite membrane exhibited a bionic structure with aligned fibers resembling human ligaments. The piezoelectric performance of the experimental group containing 3 wt.% Cu-nHA was significantly improved to 25.02 ± 0.68 V/g·m-2 compared with that of the pure PVDF group at 18.98 ± 1.18 V/g·m-2. Further enhancement in piezoelectric performance by 31.8% was achieved by manipulating the semicrystalline structures. Antibacterial and cytotoxicity tests showed that the composite membrane inherited the antibacterial properties of Cu-nHA nanoparticles without causing cytotoxic reactions. Tensile tests revealed that the membrane's flexibility of strain was adequate for use as artificial scaffolds for ligaments. In particular, the mechanical properties of the two experimental groups containing Cu-nHA were significantly enhanced compared with those of the pure PVDF group. The favorable piezoelectric and flexible properties are highly beneficial for ligament tissue regeneration. This study successfully developed PVDF/Cu-nHA piezoelectric fibers for a biocompatible, unidirectional piezoelectric membrane with potential applications as ligament repair scaffolds.

Advanced Piezoelectric Materials, Devices, and Systems for Orthopedic Medicine

Harnessing the robust electromechanical couplings, piezoelectric materials not only enable efficient bio-energy harvesting, physiological sensing and actuating but also open enormous opportunities for therapeutic treatments through surface polarization directly interacting with electroactive cells, tissues, and organs. Known for its highly oriented and hierarchical structure, collagen in natural bones produces local electrical signals to stimulate osteoblasts and promote bone formation, inspiring the application of piezoelectric materials in orthopedic medicine. Recent studies showed that piezoelectricity can impact microenvironments by regulating molecular sensors including ion channels, cytoskeletal elements, cell adhesion proteins, and other signaling pathways. This review thus focuses on discussing the pioneering applications of piezoelectricity in the diagnosis and treatment of orthopedic diseases, aiming to offer valuable insights for advancing next-generation medical technologies. Beginning with an introduction to the principles of piezoelectricity and various piezoelectric materials, this review paper delves into the mechanisms through which piezoelectric materials accelerated osteogenesis. A comprehensive overview of piezoelectric materials, devices, and systems enhancing bone tissue repair, alleviating inflammation at infection sites, and monitoring bone health is then provided, respectively. Finally, the major challenges faced by applications of piezoelectricity in orthopedic conditions are thoroughly discussed, along with a critical outlook on future development trends.

Role of in-situ electrical stimulation on early-stage mineralization and in-vitro osteogenesis of electroactive bioactive glass composites

Bioactive glass (BAG) has emerged as an effective bone graft substitute due to its diverse qualities of biocompatibility, bioactivity, osteoblast adhesion and enhanced revascularization. However, inferior osteogenic capacity of BAG compared to autologous bone grafts continues to limiting it's wide-spread clinical applications towards repairing of bone fractures and healing. In this study, we have fabricated BAG composites with 0.5 to 2 wt% bismuth ferrite (BF, a multiferroic material) with an aim to generate in-situ electrical charges pertinent to early-stage bone regeneration thus mimicking natural bone, which is a piezoelectric material. The fabricated BAG composites were characterised in terms of microstructures, phase analysis, remanent polarization, wettability and subsequently evaluated for in vitro cell proliferation and osteogenesis with and without magnetic field exposure (200 mT, 30 min./day). Pre-osteoblast cells from mice (MC3T3-E1) seeded on these composites exhibited excellent cell growth without any cytotoxicity, which is further supported by FITC/DAPI staining and a live/dead assay. The results of Alizarin Red S assay and increased levels of Alkaline Phosphatase (ALP) activity, at 21 days of culture, suggest that the BAG-BF composites promote in vitro osteogenic differentiation of pre-osteoblast cells. The enhanced osteogenesis of BAG-BF composites was also confirmed through qRT-PCR analysis, which showed rapid upregulation of osteoblastogenic specific genes namely RunX-2, Collagen-1, Bone Sialo Protein, and ALP after 21 days. Additionally, the osteogenic differentiation was assessed by the Western Blot technique, which revealed significantly higher band intensity of osteogenic markers in BAG-1.5 BF and BAG-2 BF composites than pure BAG. These findings clearly demonstrate that in-situ electrical stimulation and osteoconductive capacity of BF reinforced BAG composites have positive impact on osteoblast cell development, bone formation, and healing.

Poly(L-lactide)/nano-hydroxyapatite piezoelectric scaffolds for tissue engineering

The development of bone tissue engineering, a field with significant potential, requires a biomaterial with high bioactivity. The aim of this manuscript was to fabricate a nanofibrous poly(L-lactide) (PLLA) scaffold containing nano-hydroxyapatite (nHA) to investigate PLLA/nHA composites, particularly the effect of fiber arrangement and the addition of nHA on the piezoelectric phases and piezoelectricity of PLLA samples. In this study, we evaluated the effect of nHA particles on a PLLA-based electrospun scaffold with random and aligned fiber orientations. The addition of nHA increased the surface free energy of PLLA/nHA (42.9 mN/m) compared to PLLA (33.1 mN/m) in the case of aligned fibers. WAXS results indicated that at room temperature, all the fibers are in an amorphous state indicated by a lack of diffraction peaks and amorphous halo. DSC analysis showed that all samples located in the amorphous/disordered alpha' phase crystallize intensively at temperatures just above the Tg and recrystallize on further heating, achieving significantly higher crystallinity for pure PLLA than for doped nHA, 70 % vs 40 %, respectively. Additionally, PLLA/nHA fibers show a lower heat capacity for PLLA in the amorphous state, indicating that nHA reduces the molecular mobility of PLLA. Moreover, piezoelectric constant d33 was found to increase with the addition of nHA and for the aligned orientation of the fibers. In vitro tests confirmed that the addition of nHA and the aligned orientation of nanofibers increased osteoblast proliferation.

Vasculo-osteogenic keratin-based nanofibers containing merwinite nanoparticles and sildenafil for bone tissue regeneration

Vascularization of bone tissue constructs plays a pivotal role in facilitating nutrient transport and metabolic waste removal during the processes of osteogenesis and bone regeneration in vivo. In this study, a sildenafil (Sil)-loaded nanofibrous scaffold of keratin/Soluplus/merwinite (KS.Me.Sil) was fabricated through electrospinning and the effectiveness of the scaffold was assessed for bone tissue engineering applications. The KS.Me.Sil nanofibrous scaffold exhibited notably enhanced ultimate tensile strength (3.38 vs 2.61 MPa) and elastic modulus (69.83 vs 46.27 MPa) compared to the KS scaffold. The in vitro release of Ca2+, Si4+ and Mg2+ ions and the release of Sil from the nanofibers as well as biodegradability and bioactivity were evaluated for 14 days. Protein adsorption capability and cytocompatibility of the scaffolds were tested. Alkaline phosphatase activity test, Alizarin red staining and qRT-PCR analysis demonstrated that the KS.Me.Sil nanofibers had the best osteogenic activity among other samples. Also, the results of the chorioallantoic membrane assay showed an almost threefold increase in blood vessel density in the group treated with the KS.Me.Sil nanofibers extract compared to the KS. In conclusion, our findings suggest that the electrospun KS.Me.Sil nanofibrous scaffold offers a robust structure with exceptional osteogenic and angiogenic characteristics, making it a promising candidate for bone tissue engineering applications.

Clinical Effectiveness of Bee Venom Acupuncture for Bone Fractures and Potential Mechanisms: A Narrative Overview

Bee venom acupuncture, a type of herbal acupuncture, combines the pharmacological actions of bioactive compounds from bee venom with the mechanical stimulation of meridian points. Bee venom acupuncture is gaining popularity, particularly in the Republic of Korea, primarily for pain relief of various conditions. This study aimed to summarize and evaluate the available evidence on the use of bee venom acupuncture for recovery after bone fractures. Electronic literature searches for experimental studies and clinical trials were conducted using the PubMed, China Academic Journals (CAJ), and OASIS databases. The search revealed 31 studies, of which six met our criteria. These studies demonstrated that bee venom acupuncture can be effective in treating bone fractures, suggesting a promising area for future research. However, evidence supporting its efficacy in this context is limited. Rigorous trials with large sample sizes and robust designs are needed to clarify the role of bee venom acupuncture for these indications. In addition, future studies should explore the optimal dosage and concentration of bee venom acupuncture.

An Up-to-Date Review of Materials Science Advances in Bone Grafting for Oral and Maxillofacial Pathology

Bone grafting in oral and maxillofacial surgery has evolved significantly due to developments in materials science, offering innovative alternatives for the repair of bone defects. A few grafts are currently used in clinical settings, including autografts, xenografts, and allografts. However, despite their benefits, they have some challenges, such as limited availability, the possibility of disease transmission, and lack of personalization for the defect. Synthetic bone grafts have gained attention since they have the potential to overcome these limitations. Moreover, new technologies like nanotechnology, 3D printing, and 3D bioprinting have allowed the incorporation of molecules or substances within grafts to aid in bone repair. The addition of different moieties, such as growth factors, stem cells, and nanomaterials, has been reported to help mimic the natural bone healing process more closely, promoting faster and more complete regeneration. In this regard, this review explores the currently available bone grafts, the possibility of incorporating substances and molecules into their composition to accelerate and improve bone regeneration, and advanced graft manufacturing techniques. Furthermore, the presented current clinical applications and success stories for novel bone grafts emphasize the future potential of synthetic grafts and biomaterial innovations in improving patient outcomes in oral and maxillofacial surgery.

Unlocking the potential of stimuli-responsive biomaterials for bone regeneration

Bone defects caused by tumors, osteoarthritis, and osteoporosis attract great attention. Because of outstanding biocompatibility, osteogenesis promotion, and less secondary infection incidence ratio, stimuli-responsive biomaterials are increasingly used to manage this issue. These biomaterials respond to certain stimuli, changing their mechanical properties, shape, or drug release rate accordingly. Thereafter, the activated materials exert instructive or triggering effects on cells and tissues, match the properties of the original bone tissues, establish tight connection with ambient hard tissue, and provide suitable mechanical strength. In this review, basic definitions of different categories of stimuli-responsive biomaterials are presented. Moreover, possible mechanisms, advanced studies, and pros and cons of each classification are discussed and analyzed. This review aims to provide an outlook on the future developments in stimuli-responsive biomaterials.

Direct coupled electrical stimulation towards improved osteogenic differentiation of human mesenchymal stem/stromal cells: a comparative study of different protocols

Electrical stimulation (ES) has been described as a promising tool for bone tissue engineering, being known to promote vital cellular processes such as cell proliferation, migration, and differentiation. Despite the high variability of applied protocol parameters, direct coupled electric fields have been successfully applied to promote osteogenic and osteoinductive processes in vitro and in vivo. Our work aims to study the viability, proliferation, and osteogenic differentiation of human bone marrow-derived mesenchymal stem/stromal cells when subjected to five different ES protocols. The protocols were specifically selected to understand the biological effects of different parts of the generated waveform for typical direct-coupled stimuli. In vitro culture studies evidenced variations in cell responses with different electric field magnitudes (numerically predicted) and exposure protocols, mainly regarding tissue mineralization (calcium contents) and osteogenic marker gene expression while maintaining high cell viability and regular morphology. Overall, our results highlight the importance of numerical guided experiments to optimize ES parameters towards improved in vitro osteogenesis protocols.

3D Printed Piezoelectric BaTiO3/Polyhydroxybutyrate Nanocomposite Scaffolds for Bone Tissue Engineering

Bone defects are a significant health problem worldwide. Novel treatment approaches in the tissue engineering field rely on the use of biomaterial scaffolds to stimulate and guide the regeneration of damaged tissue that cannot repair or regrow spontaneously. This work aimed at developing and characterizing new piezoelectric scaffolds to provide electric bio-signals naturally present in bone and vascular tissues. Mixing and extrusion were used to obtain nanocomposites made of polyhydroxybutyrate (PHB) as a matrix and barium titanate (BaTiO3) nanoparticles as a filler, at BaTiO3/PHB compositions of 5/95, 10/90, 15/85 and 20/80 (w/w%). The morphological, thermal, mechanical and piezoelectric properties of the nanocomposites were studied. Scanning electron microscopy analysis showed good nanoparticle dispersion within the polymer matrix. Considerable increases in the Young's modulus, compressive strength and the piezoelectric coefficient d31 were observed with increasing BaTiO3 content, with d31 = 37 pm/V in 20/80 (w/w%) BaTiO3/PHB. 3D printing was used to produce porous cubic-shaped scaffolds using a 90° lay-down pattern, with pore size ranging in 0.60-0.77 mm and good mechanical stability. Biodegradation tests conducted for 8 weeks in saline solution at 37 °C showed low mass loss (∼4%) for 3D printed scaffolds. The results obtained in terms of piezoelectric, mechanical and chemical properties of the nanocomposite provide a new promising strategy for vascularized bone tissue engineering.