Electrostatic self-assembly of pFe3O4 nanoparticles on graphene oxide: A co-dispersed nanosystem reinforces PLLA scaffolds

Tetracalcium phosphate/porous iron synergistically improved the mechanical, degradation and biological properties of polylactic acid scaffolds

Synergistically improving the mechanical and degradable properties of polylactic acid (PLA) scaffolds and endowing them with bioactivity are urgent problems to be solved in deepening their application in tissue engineering. In this work, tetracalcium phosphate (TTCP) and porous iron (pFe) were compounded by stirring and vacuum negative pressure, and then they were blended with polylactic acid and a porous scaffold (named TTCP@pFe/PLA) was prepared by selective laser sintering. On the one hand, molten polylactic acid penetrates the pores of porous iron to form an interlocking network, thereby achieving mechanical strengthening. On the other hand, the alkaline environment generated by the dissolution of tetracalcium phosphate can effectively catalyze the hydrolysis of polylactic acid to accelerate the degradation. Meanwhile, the dissolution of tetracalcium phosphate forms a local calcium-rich microenvironment, which rapidly induces apatite formation, that is, confers bioactivity on scaffolds. As a result, the TTCP@pFe/PLA scaffold exhibited a notable enhancement in mechanical strength, being 2.2 times stronger compared to the polylactic acid scaffold. More importantly, MC3T3E1 cells exhibit good adhesion, stretching, and proliferation on the composite scaffold, demonstrating good cytocompatibility. All these good properties of the TTCP@pFe/PLA scaffold indicate that it has potential applications as a novel alternative in bone tissue regeneration.

Bioactives and Biomaterial Construction for Modulating Osteoclast Activities

Bone tissue constitutes 15-20% of human body weight and plays a crucial role in supporting the body, coordinating movement, regulating mineral homeostasis, and hematopoiesis. The maintenance of bone homeostasis relies on a delicate balance between osteoblasts and osteoclasts. Osteoclasts, as the exclusive "bone resorbers" in the human skeletal system, are of paramount significance yet often receive inadequate attention. When osteoclast activity becomes excessive, it frequently leads to various bone metabolic disorders, subsequently resulting in secondary bone injuries, such as fractures. This not only reduces life quality of patients, but also imposes a significant economic burden on society. In response to the pressing need for biomaterials in the treatment of osteoclast dysregulation, there is a surge of research and investigations aimed at osteoclast regulation. Promising progress is achieved in this domain. This review seeks to provide a comprehensive understanding of how to modulate osteoclast activities. It summarizes bioactive substances that influence osteoclasts and elucidates strategies for constructing related biomaterial systems. It offers practical insights and ideas for the development and application of biomaterials and tissue engineering, with the hope of guiding the clinical treatment of osteoclast-related bone diseases using biomaterials in the future.

Wearable Magnetoelectric Stimulation for Chronic Wound Healing by Electrospun CoFe2O4@CTAB/PVDF Dressings

Magnetoelectric stimulation is a promising therapy for various disorders due to its high efficacy and safety. To explore its potential in chronic skin wound treatment, we developed a magnetoelectric dressing, CFO@CTAB/PVDF (CCP), by electrospinning cetyltrimethylammonium bromide-modified CoFe2O4 (CFO) particles with polyvinylidene fluoride. Cetyltrimethylammonium bromide (CTAB) serves as a dispersion surfactant for CFO, with its quaternary ammonium cations imparting antibacterial and hydrophilic properties to the dressing. Electrospinning polarizes polyvinylidene fluoride (PVDF) molecules and forms a fibrous membrane with flexibility and breathability. With a wearable electromagnetic induction device, a dynamic magnetic field is established to induce magnetostrictive deformation of CFO nanoparticles. Consequently, a piezoelectric potential is generated on the surface of PVDF nanofibers to enhance the endogenous electrical field in the wound, achieving a cascade coupling of electric-magnetic-mechanical-electric effects. Bacteria and cell cultures show that 2% CTAB effectively balances antibacterial property and fibroblast activity. Under dynamic magnetoelectric stimulation, the CCP dressing demonstrates significant upregulation of TGF-β, FGF, and VEGF, promoting L929 cell adhesion and proliferation. Moreover, it facilitates the healing of diabetic rat skin wounds infected with Staphylococcus aureus within 2 weeks. Histological and molecular biology evaluations confirm the anti-inflammatory effect of CTAB and the accelerated formation of collagen and vessel by electrical stimulation. This work provides insights into the application of magnetoelectric stimulation in the healing of chronic wounds.

Improved cell growth on additively manufactured Ti64 substrates with varying porosity and nanofibrous coating

3T3 Swiss albino mouse cells are often used in biotechnological applications. These cells can grow adherently on suitable surfaces. In our study, they were grown on different titanium substrates, comparing commercially available titanium sheets of grade 1 and grade 2, respectively, with Ti64 which was 3D printed with different porosity in order to identify potential substitutes for common well-plates, which could - in case of 3D printed substrates - be produced in various shapes and dimensions and thus broaden the range of substrates for cell growth in biotechnology and tissue engineering. In addition, thin layers of poly(acrylonitrile) (PAN) nanofibers were electrospun on these substrates to add a nanostructure. The common titanium sheets showed lower cell cover factors than common well plates, which could not be improved by the thin nanofibrous coating. However, the Ti sheets with nanofiber mat coatings showed higher cell adhesion and proliferation than pure PAN nanofiber mats. The 3D printed Ti64 substrates prepared by laser metal fusion, on the other hand, enabled significantly higher proliferation of (66 ± 8)% cover factor after three days of cell growth than well plates which are usually applied as the gold standard for cell cultivation ((48 ± 11)% cover factor under identical conditions). Especially the Ti64 samples with higher porosity showed high cell adhesion and proliferation. Our study suggests investigating such porous Ti64 samples further as a potential future optimum for cell adhesion and proliferation.

Fabrication of PLCL Block Polymer with Tunable Structure and Properties for Biomedical Application

Biodegradable materials are pivotal in the biomedical field, where how to precisely control their structure and performance is critical for their translational application. In this study, poly(L-lactide-b-ε-caprolactone) block copolymers (bPLCL) with well-defined segment structure are obtained by a first synthesis of poly(ε-caprolactone) soft block, followed by ring opening polymerization of lactide to form poly(L-lactide acid)  hard block. The pre-polymerization allows for fabrication of bPLCL with the definite compositions of soft/hard segment while preserving the individual segment of their special soft or hard segment. These priorities make the bPLCL afford biodegradable polymer with better mechanical and biodegradable controllability than the random poly(L-lactide-co-ε-caprolactone) (rPLCL) synthesized via traditional one-pot polymerization. 10 mol% ε-caprolactone introduction can result in a formation of an elastic polymer with elongation at break of 286.15% ± 55.23%. Also, bPLCL preserves the unique crystalline structure of the soft and hard segments to present a more sustainable biodegradability than the rPLCL. The combinative merits make the pre-polymerization technique a promising strategy for a scalable production of PLCL materials for potential biomedical application.

Advanced 3D Magnetic Scaffolds for Tumor-Related Bone Defects

The need for bone substitutes is a major challenge as the incidence of serious bone disorders is massively increasing, mainly attributed to modern world problems, such as obesity, aging of the global population, and cancer incidence. Bone cancer represents one of the most significant causes of bone defects, with reserved prognosis regarding the effectiveness of treatments and survival rate. Modern therapies, such as hyperthermia, immunotherapy, targeted therapy, and magnetic therapy, seem to bring hope for cancer treatment in general, and bone cancer in particular. Mimicking the composition of bone to create advanced scaffolds, such as bone substitutes, proved to be insufficient for successful bone regeneration, and a special attention should be given to control the changes in the bone tissue micro-environment. The magnetic manipulation by an external field can be a promising technique to control this micro-environment, and to sustain the proliferation and differentiation of osteoblasts, promoting the expression of some growth factors, and, finally, accelerating new bone formation. By incorporating stimuli responsive nanocarriers in the scaffold's architecture, such as magnetic nanoparticles functionalized with bioactive molecules, their behavior can be rigorously controlled under external magnetic driving, and stimulates the bone tissue formation.

Physiology-Inspired Multilayer Nanofibrous Membranes Modulating Endogenous Stem Cell Recruitment and Osteo-Differentiation for Staged Bone Regeneration

Bone regeneration involves a cascade of sophisticated, multiple-staged cellular and molecular events, where early-phase stem cell recruitment mediated by chemokines and late-phase osteo-differentiation induced by pro-osteogenic factors play the crucial roles. Herein, enlightened by a bone physiological and regenerative mechanism, the multilayer nanofibrous membranes (PLLA@SDF-1α@MT01) consisting of PLLA/MT01 micro-sol electrospun nanofibers as intima and PLLA/PEG/SDF-1α electrospun nanofibers as adventitia are fabricated through micro-sol electrospinning and manual multi-layer stacking technologies. In vitro releasing profiles show that PLLA@SDF-1α@MT01 represents the rapid release of stromal cell-derived SDF-1α (SDF-1α) in the outer layers, while with long-term sustained release of MT01 in the inner layer. Owing to interconnected porosity like the natural bone extracellular matrix and improved hydrophilia, PLLA@SDF-1α@MT01 manifests good biocompatibility both in vitro and in vivo. Furthermore, PLLA@SDF-1α@MT01 can promote bone marrow mesenchymal stem cells (BMSCs) migration by amplifying the SDF-1α/CXCR4 axis and stimulating BMSCs osteo-differentiation via activating the MAPK pathway in vitro. PLLA@SDF-1α@MT01, with a programmed dual-delivery system, exhibits the synergetic promotion of bone regeneration and vascularization by emulating key characteristics of the staged bone repair in vivo. Overall, PLLA@SDF-1α@MT01 that mimics the endogenous cascades of bone regeneration can enrich the physiology-mimetic staged regenerative strategy and represent a promising tissue-engineered scaffold for the bone defect.

Highly Stable Iron- and Carbon-Based Electrodes for Li-Ion Batteries: Negative Fading and Fast Charging within 12 Min

Lithium-ion batteries (LIBs) with high energy density and safety under fast-charging conditions are highly desirable for electric vehicles. However, owing to the growth of Li dendrites, increased temperature at high charging rates, and low specific capacity in commercially available anodes, they cannot meet the market demand. In this study, a facile one-pot electrochemical self-assembly approach has been developed for constructing hybrid electrodes composed of ultrafine Fe₃ O₄ particles on reduced graphene oxide (Fe₃ O₄ @rGO) as anodes for LIBs. The rationally designed Fe₃ O₄ @rGO electrode containing 36 wt % rGO exhibits an increase in specific capacity as cycling progresses, owing to improvements in the active sites, electrochemical kinetics, and catalytic behavior, leading to a high specific capacity of 833 mAh g^-1 and outstanding cycling stability over 2000 cycles with a capacity loss of only 0.127 % per cycle at 5 A g^-1 , enabling the full charging of batteries within 12 min. Furthermore, the origin of this abnormal improvement in the specific capacity (called negative fading), which exceeds the theoretical capacity, is investigated. This study opens up new possibilities for the commercial feasibility of Fe₃ O₄ @rGO anodes in fast-charging LIBs.

Magnetic nanocomposites for biomedical applications

Tissue engineering and regenerative medicine have solved numerous problems related to the repair and regeneration of damaged organs and tissues arising from aging, illnesses, and injuries. Nanotechnology has further aided tissue regeneration science and has provided outstanding opportunities to help disease diagnosis as well as treat damaged tissues. Based on the most recent findings, magnetic nanostructures (MNSs), in particular, have emerged as promising materials for detecting, directing, and supporting tissue regeneration. There have been many reports concerning the role of these nano-building blocks in the regeneration of both soft and hard tissues, but the subject has not been extensively reviewed. Here, we review, classify, and discuss various synthesis strategies for novel MNSs used in medicine. Advanced applications of magnetic nanocomposites (MG-NCs), specifically magnetic nanostructures, are further systematically reviewed. In addition, the scientific and technical aspects of MG-NC used in medicine are discussed considering the requirements for the field. In summary, this review highlights the numerous opportunities and challenges associated with the use of MG-NCs as smart nanocomposites (NCs) in tissue engineering and regenerative medicine.

Electroactive polymeric nanocomposite BC-g-(Fe3O4/GO) materials for bone tissue engineering: in vitro evaluations

Tissue engineering is a cutting-edge approach for using advanced biomaterials to treat defective bone to get desired clinical results. In bone tissue engineering, the scaffolds must have the desired physicochemical and biomechanical natural properties in order to regenerate complicated defective bone. For the first time, polymeric nanocomposite material was developed using cellulose and co-dispersed nanosystem (Fe₃O₄/GO) by free radical polymerization to fabricate porous polymeric scaffolds via freeze drying. Various characterizations techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM)/energy dispersive X-ray (EDX), and universal testing machine (UTM) were used to investigate structural, morphological, and mechanical properties. Swelling, biodegradation, and wetting analysis were also performed to evaluate their physicochemical behavior. Intercalation of Fe₃O₄ nanoparticles into GO-sheets promoted their dispersion into the polymeric matrix. All porous scaffolds possessed a well-interconnected porous structure, while the synergistic effect of Fe₃O₄/GO reinforces the mechanical strength of porous scaffolds. The compressive strength and Young's modulus were increased by increasing Fe₃O₄ amount, and maximum mechanical strength was found in HFG-4 and least in HFG-1. However, these porous scaffolds have different swelling and biodegradation behavior due to the variable Fe₃O₄ intercalations into GO-sheets. Antibacterial activities of porous scaffolds were studied against severe Gram-positive and Gram-negative pathogens and increased Fe₃O₄ amount in nanosystem increased the antibacterial activities. The cell viability and morphology of pre-osteoblast (MC3T3-E1) cell lines were studied against porous scaffolds and increased cell viability and proliferation were observed from HFG-1 to HFG-4. Hence, the electroactive material could be the potential material for bone tissue engineering.

Development of Graphene-Based Materials in Bone Tissue Engineaering

Bone regeneration-related graphene-based materials (bGBMs) are increasingly attracting attention in tissue engineering due to their special physical and chemical properties. The purpose of this review is to quantitatively analyze mass academic literature in the field of bGBMs through scientometrics software CiteSpace, to demonstrate the rules and trends of bGBMs, thus to analyze and summarize the mechanisms behind the rules, and to provide clues for future research. First, the research status, hotspots, and frontiers of bGBMs are analyzed in an intuitively and vividly visualized way. Next, the extracted important subjects such as fabrication techniques, cytotoxicity, biodegradability, and osteoinductivity of bGBMs are presented, and the different mechanisms, in turn, are also discussed. Finally, photothermal therapy, which is considered an emerging area of application of bGBMs, is also presented. Based on this approach, this work finds that different studies report differing opinions on the biological properties of bGBMS due to the lack of consistency of GBMs preparation. Therefore, it is necessary to establish more standards in fabrication, characterization, and testing for bGBMs to further promote scientific progress and clinical translation.

Exploring electroactive microenvironments in polymer-based nanocomposites to sensitize bacterial cells to low-dose embedded silver nanoparticles

The search for alternative antimicrobial strategies capable of avoiding resistance mechanisms in bacteria are highly needed due to the alarming emergence of antimicrobial resistance. The application of physical stimuli as a mean of sensitizing bacteria for the action of antimicrobials on otherwise resistant bacteria or by allowing the action of low quantity of antimicrobials may be seen as a breakthrough for such purpose. This work proposes the development of antibacterial nanocomposites using the synergy between the electrically active microenvironments, created by a piezoelectric polymer (poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)), with green-synthesized silver nanoparticles (AgNPs). The electrical microenvironment is generated via mechanical stimulation of piezoelectric PVDF-TrFE/AgNPs films using a lab-made mechanical bioreactor. The generated material's electrical response further translates to bacterial cells, namely Escherichia coli and Staphylococcus epidermidis which in combination with AgNPs and the specific morphological features of the material induce important antibacterial and antibiofilm activity. Both porous and non-porous PVDF composites have shown antibacterial characteristics when stimulated at a mechanical frequency of 4 Hz being the effect boosted when AgNPs were incorporated in the nanocomposite, reducing in more than 80% the S. epidermidis bacterial growth in planktonic and biofilm form. The electroactive environments sensitize the bacteria allowing the action of a low dose of AgNPs (1.69% (w/w)). Importantly, the material did not compromise the viability of mammalian cells, thus being considered biocompatible. The piezoelectric stimulation of PVDF-based polymeric films may represent a breakthrough in the development of antibacterial coatings for devices used at hospital setting, taking advantage on the use of mechanical stimuli (pressure/touch) to exert antibacterial and antibiofilm activity. STATEMENT OF SIGNIFICANCE: The application of physical methods in alternative to the common chemical ones is seen as a breakthrough for avoiding the emergence of antimicrobial resistance. Antimicrobial strategies that take advantage on the capability of bacteria to sense physical stimuli such as mechanical and electrical cues are scarce. Electroactive nanocomposites comprised of poly(vinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) and green-synthesized silver nanoparticles (AgNPs) were developed to obtain material able to inhibit the colonization of microorganisms. By applying a mechanical stimuli to the nanocomposite, which ultimately mimics movements such as walking or touching, an antimicrobial effect is obtained, resulting from the synergy between the electroactive microenvironments created on the surface of the material and the AgNPs. Such environments sensitize the bacteria to low doses of antimicrobials.

Evaluation of graphene-derived bone scaffold exposure to the calvarial bone_in-vitro and in-vivo studies

Graphene is a novel material which has recently been gaining great interest in the biomedical fields. Our previous study observed that graphene-derived particles help induce bone formation in a murine calvarial model. Here, we further developed a blended graphene-contained polycaprolactone (PCL/G) filament for application in a 3D-printed bone scaffold. Since implants are expected to be for long-term usage, in vitro cell culture and in vivo scaffold implants were evaluated in a critical-size bone defect calvarial model for over 60 weeks. Graphene greatly improved the mechanical strength by 30.2% compared to pure PCL. The fabricated PCL/G scaffolds also showed fine cell viability. In animal model, an abnormal electroencephalogram power spectrum and early signs of aging, such as hair graying and hair loss, were found in the group with a PCL/G scaffold compared to pure PCL scaffold. Neither of the abnormal symptoms caused death of all animals in both groups. The long-term use of graphene-derived biomaterials for in-vivo implants seems to be safe. But the comprehensive biosafety still needs further evaluation.

Synthesis techniques, characterization and mechanical properties of natural derived hydroxyapatite scaffolds for bone implants: a review

Hydroxyapatite (HAp) with good mechanical properties is a promising material meant for a number of useful bids in dentistry and orthopedic for biomedical engineering applications for drug delivery, bone defect fillers, bone cements, etc. In this paper, a comprehensive review has been done, by reviewing different literatures related to synthesis techniques, mechanical properties and property testing, method of calcination and characterization of hydroxyapatite which are product of catfish and bovine bones. The discussion is in relations of the obligatory features vital to attain the best properties for the envisioned bid of bone graft. The process approaches that are capable of fabricating the essential microstructure and the ways to advance the mechanical properties of natural mined HAp are reviewed. The standard values for tensile strength were found to be within the range of 40–300 MPa, compressive strength was 400–900 MPa, while Elastic modulus was 80–120 GPa and fracture toughness was 0.6–1 MPa m1/2 (Ramesh et al. in Ceram Int 44(9):10525–10530, 2018; Landi et al. in J Eur Ceram Soc 20(14–15):2377–2387, 2000; Munar et al. in Dent Mater J 25(1):51–58, 2006). Also, the porosity range was 70–85% (Yang et al. in Am Ceram Soc Bull 89(2):24–32, 2010), density is 3.16 g/cm3 and relative density is 95–99.5% (Ramesh et al. 2018; Landi et al. 2000; Munar et al. 2006). The literature revealed that CaP ratio varies in relation to the source and sintering temperature. For example, for bovine bone, a CaP ratio of 1.7 (Mezahi et al. in J Therm Anal Calorim 95(1):21–29, 2009) and 1.65 (Barakat et al. in J Mater Process Technol 209(7):3408–3415, 2009) was obtained at 1100 °C and 750 °C respectively. Basic understanding on the effect of adding foreign material as a strengthening agent to the mechanical properties of HAp is ground factor for the development of new biomaterial (Natural hydroxyapatite, NHAp). Therefore, it is inferred that upon careful combination of main parameters such as compaction pressures, sintering temperatures, and sintering dwell times for production natural HAp (NHAp), mechanical properties can be enhanced.

Graphic abstract

Chromium Oxide Nanoparticle Impaired Osteogenesis and Cellular Response to Mechanical Stimulus

Background

Release of metallic wear particles from hip replacement implants is closely associated with aseptic loosening that affects the functionality and survivorship of the prostheses. Chromium oxide nanoparticles (CrNPs) are the dominant form of the wear particles found in the periprosthetic tissues. Whether CrNPs play a role in the clinically observed particle-induced osteolysis, tissue inflammatory reactions and functional activities of human mesenchymal stem cells (MSCs) remain unknown.

Methods

A tibia-defect rat model, cytotoxicity assays and flow cytometry were applied to study the effect of CrNPs on MSCs survival and macrophage inflammatory response. Also, oscillatory fluid flow stimulation was used to analyse the osteogenic differentiation of MSCs while treated by CrNPs. In addition, the influence of CrNPs on MSC biomechanical properties was determined via atomic force microscope (AFM) and fluorescence microscopy.

Results

It was found that implantation of CrNPs significantly decreased bone formation in vivo. CrNPs had no obvious effects on inflammatory cytokines release of U937 macrophages. Additionally, CrNPs did not interfere with MSCs osteogenic differentiation under static culture. However, the upregulated osteogenic differentiation of MSCs due to fluid flow stimulation was reduced by CrNPs in a dose-dependent manner. Moreover, osteogenic gene expression of OPN, Cox2 and Rnux2 after mechanical stimulation was also decreased by CrNPs treatments. Furthermore, cell elasticity and adhesion force of MSCs were affected by CrNPs over 3 days of exposure. We further verified that these effects of CrNPs could be associated with its interruption on cell mechanical properties.

Conclusion

The results demonstrated that CrNPs impaired cellular response to mechanical stimulus and osteogenesis without noticeable effects on the survival of the human MSCs.

Apatite Formation Induced by Chitosan/Gelatin Hydrogel Coating Anchored on Poly(aryl ether nitrile ketone) Substrates to Promote Osteoblastic Differentiation

Bone-like apatite is a promising coating of poly(ether ether ketone) (PEEK) for bone implantation. Poly(aryl ether nitrile ketone) containing phthalazinone moiety (PPENK) is a novel alternative for its easy synthesis. Here, chitosan/gelatin hybrid hydrogel coating is applied to induce the formation of apatite on the surface of PPENK substrate through biomineralization to improve its biocompatibility and osteogenic property. PPENK possessing allyl groups (PPENK-d) are synthesized and spin-coated on PPENK substrate to impart reactive groups. The hydrogel coating is prepared by the ultraviolet crosslinking of gelatin methacrylate (GelMA) and chitosan methacrylate (CSMA) on PPENK substrate. PPENK-d, GelMA, and CSMA are characterized by ¹ H-NMR to confirm the designed structures. The presence of chitosan increases the chelation of calcium ions and thus induces the nucleation of apatite. The microstructural and compositional results reveal that the chitosan-containing hydrogel coating induced apatite coating yields a higher apatite quantity compared to the gelatin hydrogel coating. The apatite coatings on PPENK substrate promote the cytocompatibility and osteogenesis of MC3T3-E1 preosteoblasts in vitro.

Bifunctional poly (l-lactic acid)/hydrophobic silica nanocomposite layer coated on magnesium stents for enhancing corrosion resistance and endothelial cell responses

Biodegradable magnesium (Mg)-based vascular stents can overcome the limitations of conventional permanent metallic stents, such as late in-stent restenosis and thrombosis, but still have difficulty retarding degradation while providing adequate mechanical support to the blood vessel. We incorporated silica nanoparticles surface-functionalized with hexadecyltrimethoxysilane (mSiNP) into a poly (l-lactic acid) (PLLA) coating as a physical barrier to disturb the penetration of the corrosive medium as well as a bioactive source that releases silicon ions capable of stimulating endothelial cells. The corrosion resistance and biocompatibility of this bifunctional PLLA/mSiNP nanocomposite coating were investigated using different weight ratios of mSiNP. The nanocomposite coating containing more than 10 wt% of the mSiNP (PLLA/10mSiNP and PLLA/20mSiNP) significantly delayed the corrosion of the Mg substrate and exhibited favorable endothelial cell responses, compared to the pure PLLA coating. Specifically, the calculated corrosion rates of PLLA/10mSiNP and PLLA/20mSiNP decreased by half, indicating the durability of the coating after immersion in simulated body fluid for 12 days. Based on the in vitro cellular response, the incorporation of the mSiNPs into the PLLA coating significantly improved the endothelial cell responses to the Mg substrate, showing better initial cell surface coverage, migration, and proliferation rate than those of pure PLLA. These results indicate that the PLLA/mSiNP nanocomposite coatings have significant potential to improve the corrosion resistance and vascular compatibility of biodegradable Mg-based vascular stents.

Advances in the occurrence and biotherapy of osteoporosis

Osteoporosis (OP) is a bone metabolic disease, is characterized by degeneration of bone structure and decreased bone mass. It happens in more than 1/3 women and 1/5 men of over than 50 years old, which affects the health and lives of people. The main mechanism of OP is mainly that the dynamic balance between the bone formation and resorption is broken, so that bone resorption is more than bone formation. It is prone to result in bone metabolism disorder. There are many precipitating factor such as elder age, low hormone level, genetic factors and bad hobbies. At the same time, the occurrence of the OP and its complications has different degrees of impact on people's quality of life. Based on the current understanding of the OP, we summarized the etiology, current clinical drugs and potential targeting therapy for OP. Although the research have made many progress in explore what is the novel mechanism and how to improve the effect, there are still many problems in the treatment method that limit its application prospects and need to be solved. In this review, we mainly focus on the mechanism of OP and related research on the targeted treatment of OP. Hopefully, our summary will provide a reference to develop some novel strategies for the target therapy of OP.

A three-dimensional-printed SPION/PLGA scaffold for enhanced palate-bone regeneration and concurrent alteration of the oral microbiota in rats

Scaffold implantation for the repair of oral bone defects involves an interplay between the scaffold biomaterial and the microenvironment. However, previous studies on this subject have only considered the effects of the immune system and largely ignored those of the oral microbiota. Accordingly, in the present study, we prepared composite scaffolds comprising a three-dimensional poly(l-lactide-co-glycolide) matrix with a superparamagnetic iron oxide nanoparticle (SPION) coating and used a rat model to evaluate their palate-bone-regenerating effects and their interaction with the oral microbiota. It was found that the SPION coated scaffold induced better bone regeneration than that achieved by the controls. Furthermore, it significantly decreased the operational taxonomic units (OTU) numbers as determined by 16 s rRNA gene sequencing, and also resulted in decreased Chao and ACE alpha diversity indexes compared with those of the controls. However, it had no effect on beta diversity. SPION coated scaffolds caused a shift in oral bacterial composition characterized by a decrease in the Clostridium spp. population, and the dominant flora being Proteobacteria. Furthermore, SPION coated scaffolds upregulated the concentration of serum iron, hepcidin, and P1NP. Thus, SPION coated scaffolds enhanced bone regeneration, and this effect was partly related to alteration of the oral microbiota by the antibacterial effects of SPION. Our findings provide a better understanding of the role of oral microbiota in oral bone regeneration and how SPION coated scaffolds can be used to enhance it.

PEI-modified diatomite/chitosan composites as bone tissue engineering scaffold for sustained release of BMP-2

The bone healing defects resulting from bone disease remain a significant clinical challenge. The bone tissue engineering scaffolds combined with osteoinductive compounds represent an effective approach to overcome this challenge. In this study, a novel chitosan-based scaffold was prepared by incorporating modified natural diatomite (DE) as filler and adsorption element. Specifically, modified-diatomite (MDE) was synthesized by grafting polyethyleneimine (PEI) on the surface of diatomite via hydroxyl groups. The physicochemical characteristics of MDE, including chemical composition, zeta potential, and adsorption behavior, were investigated successively. Further, the mechanical strength, drug release, cytotoxicity and osteogenic activity analyses were carried out for the scaffold material. The FTIR and zeta potential analyses exhibited that the amino groups (-NH₂) were grafted on MDE, and the surface potential of diatomite altered from -24 mV to 55 mV. Subsequently, the protein adsorption capacity and cytocompatibility of MDE were observed to be improved as compared to DE. The compressive strength was observed to be enhanced due to the addition of MDE. Besides, the composite scaffold loaded with rhBMP-2 demonstrated a more positive impact on proliferation and osteogenic differentiation of the bone mesenchymal stem cells, thus, indicating an optimal bone regeneration capacity. The findings obtained in this study reveal that the MDE-rhBMP-2/CS composite scaffold can be potentially used to promote the bone tissue regeneration.

Ternary biogenic silica/magnetite/graphene oxide composite for the hyperactivation of Candida rugosa lipase in the esterification production of ethyl valerate

Oil palm leaves (OPL) silica (SiO₂) can replace the energy-intensive, commercially produced SiO₂. Moreover, the agronomically sourced biogenic SiO₂ is more biocompatible and cost-effective enzyme support, which properties could be improved by the addition of magnetite (Fe₃O₄) and graphene oxide (GO) to yield better ternary support to immobilize enzymes, i.e., Candida rugosa lipase (CRL). This study aimed to optimize the Candida rugosa lipase (CRL immobilization onto the ternary OPL-silica-magnetite (Fe₃O₄)-GO (SiO₂/Fe₃O₄/GO) support, for use as biocatalyst for ethyl valerate (EV) production. Notably, this is the first study detailing the CRL/SiO₂/Fe3O4/GO biocatalyst preparation for rapid and high yield production of ethyl valerate (EV). AFM and FESEM micrographs revealed globules of CRL covalently bound to GL-A-SiO₂/Fe₃O₄/GO; similar to Raman and UV-spectroscopy results. FTIR spectra revealed amide bonds at 3478 cm^-1 and 1640 cm^-1 from covalent interactions between CRL and GL-A-SiO₂/Fe₃O₄/GO. Optimum immobilization conditions were 4% (v/v) glutaraldehyde, 8 mg/mL CRL, at 16 h stirring in 150 mM NaCl at 30 °C, offering 24.78 ± 0.26 mg/g protein (specific activity = 65.24 ± 0.88 U/g). The CRL/SiO₂/Fe₃O₄/GO yielded 77.43 ± 1.04 % of EV compared to free CRL (48.75 ± 0.70 %), verifying the suitability of SiO₂/Fe₃O₄/GO to hyperactivate and stabilize CRL for satisfactory EV production.

Synthesis and Characterization of Silver-Coated Polymeric Scaffolds for Bone Tissue Engineering: Antibacterial and In Vitro Evaluation of Cytotoxicity and Biocompatibility

In bone tissue engineering, multifunctional composite materials are very challenging. Bone tissue engineering is an innovative technique to develop biocompatible scaffolds with suitable orthopedic applications with enhanced antibacterial and mechanical properties. This research introduces a polymeric nanocomposite scaffold based on arabinoxylan-co-acrylic acid, nano-hydroxyapatite (nHAp), nano-aluminum oxide (nAl2O3), and graphene oxide (GO) by free-radical polymerization for the development of porous scaffolds using the freeze-drying technique. These polymeric nanocomposite scaffolds were coated with silver (Ag) nanoparticles to improve antibacterial activities. Together, nHAp, nAl2O3, and GO enhance the multifunctional properties of materials, which regulate their physicochemical and biomechanical properties. Results revealed that the Ag-coated polymeric nanocomposite scaffolds had excellent antibacterial properties and better microstructural properties. Regulated morphological properties and maximal antibacterial inhibition zones were found in the porous scaffolds with the increasing amount of GO. Moreover, the nanosystem and the polymeric matrix have improved the compressive strength (18.89 MPa) and Young's modulus (198.61 MPa) of scaffolds upon increasing the amount of GO. The biological activities of the scaffolds were investigated against the mouse preosteoblast cell lines (MC3T3-E1) and increasing the quantities of GO helps cell adherence and proliferation. Therefore, our findings showed that these silver-coated polymeric nanocomposite scaffolds have the potential for engineering bone tissue.

Modulating the Biomechanical Properties of Engineered Connective Tissues by Chitosan-Coated Multiwall Carbon Nanotubes

Background

Under certain conditions, the physiological repair of connective tissues might fail to restore the original structure and function. Optimized engineered connective tissues (ECTs) with biophysical properties adapted to the target tissue could be used as a substitution therapy. This study aimed to investigate the effect of ECT enforcement by a complex of multiwall carbon nanotubes with chitosan (C-MWCNT) to meet in vivo demands.

Materials and Methods

ECTs were constructed from human foreskin fibroblasts (HFF-1) in collagen type I and enriched with the three different percentages 0.025, 0.05 and 0.1% of C-MWCNT. Characterization of the physical properties was performed by biomechanical studies using unidirectional strain.

Results

Supplementation with 0.025% C-MWCNT moderately increased the tissue stiffness, reflected by Young’s modulus, compared to tissues without C-MWCNT. Supplementation of ECTs with 0.1% C-MWCNT reduced tissue contraction and increased the elasticity and the extensibility, reflected by the yield point and ultimate strain, respectively. Consequently, the ECTs with 0.1% C-MWCNT showed a higher resilience and toughness as control tissues. Fluorescence tissue imaging demonstrated the longitudinal alignment of all cells independent of the condition.

Conclusion

Supplementation with C-MWCNT can enhance the biophysical properties of ECTs, which could be advantageous for applications in connective tissue repair.

Accelerated degradation of HAP/PLLA bone scaffold by PGA blending facilitates bioactivity and osteoconductivity

The incorporation of hydroxyapatite (HAP) into poly-l-lactic acid (PLLA) matrix serving as bone scaffold is expected to exhibit bioactivity and osteoconductivity to those of the living bone. While too low degradation rate of HAP/PLLA scaffold hinders the activity because the embedded HAP in the PLLA matrix is difficult to contact and exchange ions with body fluid. In this study, biodegradable polymer poly (glycolic acid) (PGA) was blended into the HAP/PLLA scaffold fabricated by laser 3D printing to accelerate the degradation. The results indicated that the incorporation of PGA enhanced the degradation rate of scaffold as indicated by the weight loss increasing from 3.3% to 25.0% after immersion for 28 days, owing to the degradation of high hydrophilic PGA and the subsequent accelerated hydrolysis of PLLA chains. Moreover, a lot of pores produced by the degradation of the scaffold promoted the exposure of HAP from the matrix, which not only activated the deposition of bone like apatite on scaffold but also accelerated apatite growth. Cytocompatibility tests exhibited a good osteoblast adhesion, spreading and proliferation, suggesting the scaffold provided a suitable environment for cell cultivation. Furthermore, the scaffold displayed excellent bone defect repair capacity with the formation of abundant new bone tissue and blood vessel tissue, and both ends of defect region were bridged after 8 weeks of implantation.

Load-bearing biodegradable PCL-PGA-beta TCP scaffolds for bone tissue regeneration

A biocompatible and biodegradable scaffold with load-bearing ability is required to enhance the repair of bone defects by facilitating the attachment, and proliferation of cells, and vascularization during new bone formation. However, it is challenging to maintain the porosity and biodegradability, as well as mechanical properties (especially compressive strength), at the same time. Therefore, in the present work, a biodegradable composite structure of poly(caprolactone) (PCL) was designed using compression molding with varying amounts of poly(glycolic acid) (PGA) (25, 50, 75 wt%) and fixed amount (20 wt%) of beta tricalcium phosphate (beta TCP). It was hypothesized that the fabricated composite structure will develop porosity during the degradation of the PGA and that the corresponding decrease in mechanical properties will be compensated by new bone formation and ingrowth, in vivo. Accordingly, we have systematically studied the effects of sample composition on time-dependent dissolution and mechanical properties of the PGA/beta TCP scaffolds. The compressive strength increased up to ~92 MPa at 50% compression of the designed PCL-PGA samples. Furthermore, the dissolution rate, as well as weight loss, was observed to increase with an increase in the PGA amount in PCL. Based on the mechanical properties and dissolution data, it is concluded that the PCL-PGA scaffolds with beta TCP can be suitable candidates for bone tissue engineering applications, specifically for the reconstruction of bone defects, where strength and biodegradation are both important characteristics.

CuO assisted borate 1393B3 glass scaffold with enhanced mechanical performance and cytocompatibility: An In vitro study

Herein, three dimensional porous 1393B3 borate-based glass (BBG) scaffold along with their CuO derivatives (C1BBG, C2BBG, and C3BBG) tailored with trabecular bones' architecture were prepared by melt-quench route followed by foam replica technique. The properties of 'CuO incorporated' scaffolds, as compared to 'as prepared' scaffold were analyzed by a series of In vitro investigations for enhancement in biological compatibility, bioactivity, and physicomechanical performances. The in vitro study demonstrates superior mechanochemical stability of CBBGs (CuO derived 1393B3) than the pure BBG, while causing no or minimal effect on bioactivity and cytocompatibility post CuO incorporation to the BBG. In fact, the biological compatibility examined through MTT, Live/Dead, and cell adhesion study using the L929 cell lines was enhanced in the CBBGs up to 1% CuO incorporated scaffolds (C1BBG and C2BBG) in most cases. However, the enhanced biological compatibility was observed in C1BBG in comparison to other BBGs. Thus, the CuO incorporation into BBG enhanced mechanochemical and biological performance without affecting the bioactivity of the scaffold; henceforth, CBBGs could be considered neo bone tissue regenerative biomaterials.

Long-term antibacterial composite via alginate aerogel sustained release of antibiotics and Cu used for bone tissue bacteria infection

Bone related-bacterial diseases including wound infections and osteomyelitis (OM) remain a serious problem accompanied with amputation in most severe cases. In this work, we report an exceptional effective antibacterial alginate aerogel, which consists of tigecycline (TGC) and octahedral Cu crystal as an organo-inorganic synergy platform for antibacterial and local infection therapy applications. The alginate aerogel could greatly prolong the release of copper ions and maintain effective antibacterial concentration over 18 days. The result of in-vitro experiments demonstrated that the alginate aerogel has an exceptional effective function on antibacterial activity. Cytotoxicity tests indicated that the alginate aerogel has low biological toxicity (average cell viability >75%). These remarkable results suggested that the alginate aerogel exhibits great potential for the treatment of OM, and has a prosperous future of application in bone tissue engineering.

Microstructure evolution and texture tailoring of reduced graphene oxide reinforced Zn scaffold

Zinc (Zn) possesses desirable degradability and favorable biocompatibility, thus being recognized as a promising bone implant material. Nevertheless, the insufficient mechanical performance limits its further clinical application. In this study, reduced graphene oxide (RGO) was used as reinforcement in Zn scaffold fabricated via laser additive manufacturing. Results showed that the homogeneously dispersed RGO simultaneously enhanced the strength and ductility of Zn scaffold. On one hand, the enhanced strength was ascribed to (i) the grain refinement caused by the pinning effect of RGO, (ii) the efficient load shift due to the huge specific surface area of RGO and the favorable interface bonding between RGO and Zn matrix, and (iii) the Orowan strengthening by the homogeneously distributed RGO. On the other hand, the improved ductility was owing to the RGO-induced random orientation of grain with texture index reducing from 20.5 to 7.3, which activated more slip systems and provided more space to accommodate dislocation. Furthermore, the cell test confirmed that RGO promoted cell growth and differentiation. This study demonstrated the great potential of RGO in tailoring the mechanical performance and cell behavior of Zn scaffold for bone repair.

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Zn/RGO composite scaffold was successfully fabricated by laser additive manufacturing.

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RGO refined the grains and significantly weakened the texture with random grain orientation.

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The uniformly distributed RGO simultaneously enhanced the strength and ductility of scaffold.

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The incorporated RGO exerted a positive effect on cell growth and differentiation.

In Situ Generation of Hydroxyapatite on Biopolymer Particles for Fabrication of Bone Scaffolds Owning Bioactivity

Hydroxyapatite (HAP) can endow a biopolymer scaffold with good bioactivity and osteoconductive ability, while the interfacial bonding is fairly weak between HAP and biopolymers. In this study, HAP was in situ generated on poly(l-lactic acid) (PLLA) particles, and then they were used to fabricate a scaffold by selective laser sintering. Detailedly, PLLA particles were first functionalized by dopamine oxide polymerization, which introduced abundance active catechol groups on the particle surface, and subsequently, the catechol groups concentrated Ca²⁺ ions by chelation in a simulated body fluid solution, and then, Ca²⁺ ions absorbed PO₄^3- ions through electrostatic interactions for in situ nucleation of HAP. The results indicated that HAP was homogeneously generated on the PLLA particle surface, and HAP and PLLA exhibited good interfacial bonding in the HAP/PLLA scaffolds. Meanwhile, the scaffolds displayed excellent bioactivity by inducing apatite precipitation and provided a good environment for human bone mesenchymal stem cell attachment, proliferation, and osteogenic differentiation. More importantly, the ingrowth of blood vessel and the formation of new bone could be stimulated by the scaffolds in vivo, and the bone volume fraction and bone mineral density increased by 44.44 and 41.73% compared with the pure PLLA scaffolds, respectively. Serum biochemical indexes fell within the normal range, which indicated that there was no harmful effect on the normal functioning of the body after implanting the scaffold.

Micro Magnetic Field Produced by Fe3O4 Nanoparticles in Bone Scaffold for Enhancing Cellular Activity

The low cellular activity of poly-l-lactic acid (PLLA) limits its application in bone scaffold, although PLLA has advantages in terms of good biocompatibility and easy processing. In this study, superparamagnetic Fe₃O₄ nanoparticles were incorporated into the PLLA bone scaffold prepared by selective laser sintering (SLS) for continuously and steadily enhancing cellular activity. In the scaffold, each Fe₃O₄ nanoparticle was a single magnetic domain without a domain wall, providing a micro-magnetic source to generate a tiny magnetic field, thereby continuously and steadily generating magnetic stimulation to cells. The results showed that the magnetic scaffold exhibited superparamagnetism and its saturation magnetization reached a maximum value of 6.1 emu/g. It promoted the attachment, diffusion, and interaction of MG63 cells, and increased the activity of alkaline phosphatase, thus promoting the cell proliferation and differentiation. Meanwhile, the scaffold with 7% Fe₃O₄ presented increased compressive strength, modulus, and Vickers hardness by 63.4%, 78.9%, and 19.1% compared with the PLLA scaffold, respectively, due to the addition of Fe₃O₄ nanoparticles, which act as a nanoscale reinforcement in the polymer matrix. All these positive results suggested that the PLLA/Fe₃O₄ scaffold with good magnetic properties is of great potential for bone tissue engineering applications.

Acrylated epoxidized soybean oil/hydroxyapatite-based nanocomposite scaffolds prepared by additive manufacturing for bone tissue engineering

The mechanical properties and biocompatibility of nanocomposites composed of Acrylated Epoxidized Soybean Oil (AESO), nano-Hydroxyapatite (nHA) rods and either 2-Hydroxyethyl Acrylate (HEA) or Polyethylene Glycol Diacrylate (PEGDA) and 3D printed using extrusion-based additive manufacturing methods were investigated. The effects of addition of HEA or PEGDA on the rheological, mechanical properties and cell-biomaterial interactions were studied. AESO, PEGDA (or HEA), and nHA were composited using an ultrasonic homogenizer and scaffolds were 3D printed using a metal syringe on an extrusion-based 3D printer while simultaneously UV cured during layer-by-layer deposition. Nanocomposite inks were characterized for their viscosity before curing, and dispersion of the nHA particles and tensile mechanical properties after curing. Proliferation and differentiation of human bone marrow-derived mesenchymal stem cells (BM-MSCs) were studied by seeding cells onto the scaffolds and culturing in osteogenic differentiation medium for 7, 14 and 21 days. Overall, each of the scaffolds types demonstrated controlled morphology resulting from the printability of nanocomposite inks, well-dispersed nHA particles within the polymer matrices, and were shown to support cell proliferation and osteogenic differentiation after 14 and 21 days of culture. However, the nature of the functional groups present in each ink detectably affected the mechanical properties and cytocompatibility of the scaffolds. For example, while the incorporation of HEA reduced nHA dispersion and tensile strength of the final nanocomposite, it successfully enhanced shear yield strength, and printability, as well as cell adhesion, proliferation and osteogenic differentiation, establishing a positive effect perhaps due to additional hydrogen bonding.

Rod-like Eutectic Structure in Biodegradable Zn-Al-Sn Alloy Exhibiting Enhanced Mechanical Strength

Zn alloy is recognized as a promising biodegradable metal for bone implant applications because of its good biocompatibility and moderate degradation rate. Nevertheless, the insufficient strength limits its applications. In this study, a rod-like eutectic structure was fabricated in Zn-Al-Sn alloy with the addition of Sn via selective laser melting. It was found that the Al-enriched phase nucleated primarily during cooling and caused the rapid precipitation of Zn. This inevitably consumed the liquid Zn and increased the ratio of Sn to Zn in the liquid phase, resulting in the formation of the eutectic, which was composed of the Sn-enriched phase and the Zn-enriched phase. More importantly, the coupled growth of the Sn-enriched and Zn-enriched phases and their volume differences together led to a rod-like morphology of the eutectic according to the volume fraction theory. Consequently, the yield and ultimate compressive strengths were enhanced to 180 ± 18.8 and 325 ± 29.6 MPa for the Zn-Al-2Sn alloy, respectively. This could be attributed to the pinning effect of the rod-like eutectic, which could block dislocation motion and result in dislocation pile-up, thereby conducing to the mechanical reinforcement. In addition, the Zn-Al-Sn alloy also exhibited good biocompatibility and increased degradation rate because of the enhanced galvanic corrosion. This study showed the potential of rod-like eutectic for the mechanical enhancement of the biodegradable Zn alloy.

TiO2-Induced In Situ Reaction in Graphene Oxide-Reinforced AZ61 Biocomposites to Enhance the Interfacial Bonding

Graphene oxide (GO) can improve the degradation resistance of biomedical Mg alloy because of its excellent impermeability and outstanding chemical inertness. However, the weak interfacial bonding between GO and Mg matrix leads to easily detaching during degradation. In this study, in situ reaction induced by TiO₂ took place in the AZ61-GO biocomposite to enhance the interfacial bonding between GO and Mg matrix. For the specific process, TiO₂ was uniformly and tightly deposited onto the GO surface by hydrothermal reaction (TiO₂/GO) first and then used for fabricating AZ61-TiO₂/GO biocomposites by selective laser melting (SLM). Results showed that TiO₂ was in situ reduced by magnesiothermic reaction during SLM process, and the reduzate Ti, on the one hand, reacted with Al in the AZ61 matrix to form TiAl₂ and, on the other hand, reacted with GO to form TiC at the AZ61-GO interface. Owing to the enhanced interfacial bonding, the AZ61-TiO₂/GO biocomposite showed 12.5% decrease in degradation rate and 10.1% increase in compressive strength as compared with the AZ61-GO biocomposite. Moreover, the AZ61-TiO₂/GO biocomposite also showed good cytocompatibility because of the slowed degradation. These findings may provide guidance for the interfacial enhancement in GO/metal composites for biomedical applications.