Synthesis of a mace-like cellulose nanocrystal@Ag nanosystem via in-situ growth for antibacterial activities of poly-L-lactide scaffold

Photonic hydrogels combining the slow photon effect and NO gas therapy for synergetic enhanced photodynamic antibacterial therapy

Photodynamic therapy (PDT) offers potential for combating bacterial infections through the generation of reactive oxygen species (ROS). However, the antibacterial efficiency of PDT is largely impeded by the limited photon absorption of photosensitizers and the short diffusion length and lifespan of ROS. Herein, we present a light-harvesting platform based on l-arginine-modified photonic hydrogels loaded with new indocyanine green (PG@Arg/IR820) for synergizing the slow photon effect with NO gas therapy to enhance PDT antibacterial efficiency. Upon near-infrared (NIR) light irradiation, PG@Arg/IR820 can maximize the utilization of photons via the slow photon effect to generate sufficient ROS, which not only acts as the primary bactericidal agent in PDT but also triggers l-arginine to generate NO. NO exhibits a long diffusion distance and lifespan and can freely diffuse to inhibit distant bacterial growth, demonstrating a vital complementary advantage in bacterial inactivation by ROS. The synergistic effect of the slow photon effect combined with NO gas therapy allows PG@Arg/IR820 to intensify bacterial destruction and enhance PDT antibacterial efficiency. This antibacterial system sheds light on an advisable design principle for efficient antibacterial activities in photodynamic inactivation.

Nanostructure-Mediated Photothermal Effect for Reinforcing Physical Killing Activity of Nanorod Arrays

The physical killing of bacteria based on surface topography has attracted much attention due to the sustainable and safe prevention of biofilm formation. However, the antibacterial efficiency of biomedical implants derived solely from nanostructures or microstructures is insufficient to combat bacteria against common infections, such as methicillin-resistant Staphylococcus aureus with thick cell walls. Herein, photothermal therapy is carried out in the presence of nanorod arrays to mitigate infection of biomedical implants. Different from traditional photothermal therapy relying on a photosensitizer, the photothermal effect is mediated by light traps rendered by the nanorod arrays, and consequently, the photosensitizer is not needed. Finite element simulations and experiments are performed to elucidate the light-to-thermal conversion mechanism. This photothermal platform, in conjunction with thermosensitive nitric oxide therapy, is applied to treat titanium implant infection. The nanostructure-mediated photothermal effect destroys bacterial cell walls by inhibiting peptidoglycan synthesis and increasing the membrane permeability by affecting fatty acid synthesis. Furthermore, the nanorods synergistically puncture the bacterial membrane easily as demonstrated by experiments and transcriptome analysis. The results provide insights into the development of efficient antibacterial treatment of implants by combining nanostructures and photothermal therapy.

Electrospun zeolitic imidazole framework-8 loaded silk fibroin/polycaprolactone nanofibrous scaffolds for biomedical application

The development of electrospun nanofibrous scaffolds (NFSs) have aroused much attraction in the field of biomedical engineering, due to their small fiber diameter, high specific surface area, and excellent extracellular matrix comparability. The main focus of this study is to design and fabricate novel zeolitic imidazole framework-8 (ZIF-8)-loaded silk fibrin/polycaprolactone (SF/PCL) nanofiber composite scaffolds by using the electrospinning strategy. Firstly, ZIF-8 was synthesized and characterized, which showed remarkable features in terms of shape, size, chemical and physical properties. Then, three different amounts of ZIF-8 were encapsulated into SF/PCL nanofibers during electrospinning, to investigate how the addition of ZIF-8 affected the morphology, and structure, as well as physical, mechanical, and biological properties of the nanofiber composite scaffolds. It was found that the addition of ZIF-8 didn't change the nanofibrous morphology of the composite scaffold, and no bead-like structure were found for the SF/PCL composite scaffolds loading with or without ZIF-8. The appropriate addition of ZIF-8 could significantly increase the mechanical properties of SF/PCL NFSs. The SF/PCL NFS containing 5% ZIF-8 showed high ultimate stress and initial modulus, which were 40.31 ± 2.31 MPa, and 569.19 ± 21.38 MPa, respectively. Furthermore, the MTT assay indicated that the pure SF/PCL scaffold and one with 1% ZIF-8 exhibited nearly identical cell compatibility toward human dermal fibroblast (HDF) cells, but some obvious cytotoxicity was observed with the increase of ZIF-8 content. However, the incorporation of ZIF-8 into SF/PCL NFSs was found to have excellent antibacterial rate against both E. coli and S. aureus. In all, the incorporation of 1% ZIF-8 could impart the SF/PCL NFS with balanced bio-function, making it a promising candidate for diverse biomedical applications such as tissue engineering and wound healing.

A Bacterial Capturing, Neural Network-Like Carbon Nanotubes/Prussian Blue/Puerarin Nanocomposite for Microwave Treatment of Staphylococcus Aureus-Infected Osteomyelitis

Staphylococcus aureus (S. aureus)-infected osteomyelitis is a deep tissue infection that cannot be effectively treated with antibiotics. Microwave (MW) thermal therapy (MTT) and MW dynamic therapy (MDT) based on MW-responsive materials are promising for the therapy of bacteria-infected osteomyelitis occurring in deep tissues that cannot be effectively treated with antibiotics. In this work, the MW-responsive system of carbon nanotubes (CNTs)/Prussian blue (PB)/puerarin (Pue) with stable network-like structures is constructed. The PB is grown in situ on the CNTs, and its introduction not only reduces the aggregation of the network-like structures of the CNTs, but the large specific surface area and mesoporous structure can also provide many active sites for the adsorption of oxygen and polar molecules. Pue is a natural anti-inflammatory material that reduces inflammation at the infection site. The composite of the CNTs and PB avoids the skin effect and thus can improve dielectric and reflection losses. The MW thermal response of CNTs/PB/Pue is mainly due to the occurrence of reflection loss, dielectric loss, multiple reflections and scattering, interface polarization, and dipole polarization. In addition, under MW irradiation, the CNTs/PB/Pue can produce reactive oxygen species (ROS), such as singlet oxygen (1O2), hydroxyl radical (·OH).

Multiple-Effect Combined Hydrogels: "Temporal Regulation" Treatment of Osteosarcoma-Associated Bone Defects with Switchable Hyperthermia and Bioactive Agents

Achieving the clinically staged treatment of osteosarcoma-associated bone defects encounters the multiple challenges of promptly removing postoperative residual tumor cells and bacterial infection, followed by bone reconstruction. Herein, a core/shell hydrogel with multiple-effect combination is designed to first exert antitumor and antibacterial activities and then promote osteogenesis. Specifically, doxorubicin (DOX) is loaded by magnesium-iron-based layered double hydroxide (LDH) to prepare LDOX, which is introduced into a thermo-sensitive hydrogel to serve as an outer shell of the core/shell hydrogel, meanwhile, LDH-contained liquid crystal hydrogel, abbreviated as LCgel-L, is served as an inner core. At the early stage of treatment, the dissociation of the outer shell triggered by moderate hyperthermia led to the thermo-sensitive release of LDOX, which can be targeted for the release of DOX within tumor cells, thereby promptly removing postoperative residual tumor cells based on the synergistic effect of photothermal therapy (PTT) and DOX, and postoperative bacterial infection can also be effectively prevented by PTT simultaneously. More importantly, the dissociation of the outer shell prompted the full exposure of the inner core, which will exert osteogenic activity based on the synergy of liquid crystal hydrogel as well as LDH-induced mild hyperthermia and ion effects, thereby enabling "temporal regulation" treatment of osteosarcoma-associated bone defects. This study provides a valuable insight for the development of osteosarcoma-associated bone repair materials.

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

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

LAPONITE® nano-silicates potentiate the angiogenic effects of FG-4592 and osteogenic effects of BMP-2

LAPONITE®-based drug delivery systems offer many advantages due to the unique ionic and physical properties of LAPONITE®. The high ionicity and large surface area of LAPONITE® nanoparticles enable the intercalation and dissolution of biomolecules. In this study, we explored the potential of LAPONITE® as a carrier for FG-4592 to support angiogenesis and as a carrier for bone morphogenic protein-2 (BMP-2) to support osteogenesis. Interestingly, we found that LAPONITE® promoted the FG-4592 induced upregulation of vascular endothelial growth factor (VEGF) gene expression of human umbilical cord endothelial cells (HUVECs). Additionally, we observed that LAPONITE® could provide a sustained release of BMP-2 and significantly potentiate the osteogenic effects of BMP-2 on adipose derived mesenchymal stem cells (AMSCs). Overall, current findings on the LAPONITE®-drug/protein model system provide a unique way to potentiate the angiogenic activities of FG-4592 on HUVECs and osteogenic effects of BMP-2 on AMSCs for tissue engineering application. Future studies will be directed towards gaining a deeper understanding of these effects on a co-culture system of HUVECs and AMSCs.

Application of decalcified bone matrix in Salmon bone for tibial defect repair in rat model

AIM

The optimal preparation conditions of Salmon decalcified bone matrix (S-DBM) were explored, and the properties of S-DBM bone particles and bone powder were studied respectively. The therapeutic effect of S-DBM on tibial defect in female Sprague Dawley (SD) rats was preliminarily verified.

METHODS

This study assessed the structural and functional similarities of Salmon bone DBM (S-DBM). The biocompatibility assessment was conducted using both in vivo and in vitro experiments, establishing an animal model featuring tibial defects in rats and on the L929 cell line, respectively. The control group, bovine DBM (bDBM), was compared to the S-DBM-treated tibial defect rats. Imaging and histology were used to study implant material changes, defect healing, osteoinductive repair, and degradation.

RESULTS

The findings of our study indicate that S-DBM exhibits favorable repairing effects on bone defects, along with desirable physicochemical characteristics, safety, and osteogenic activity.

CONCLUSIONS

The S-DBM holds significant potential as a medical biomaterial for treating bone defects, effectively fulfilling the clinical demands for materials used in bone tissue repair engineering.

Biomolecule-grafted GO enhanced the mechanical and biological properties of 3D printed PLA scaffolds with TPMS porous structure

Graphene oxide (GO) exhibits excellent mechanical strength and modulus. However, its effectiveness in mechanically reinforcing polymer materials is limited due to issues with interfacial bonding and dispersion arising from differences in the physicochemical properties between GO and polymers. Surface modification using coupling agents is an effective method to improve the bonding problem between polymer and GO, but there may be biocompatibility issues when used in the biomedical field. In this study, the biomolecule L-lysine, was applied to improve the interfacial bonding and dispersion of GO in polylactic acid (PLA) without compromising biocompatibility. The PLA/L-lysine-modified GO (PLA/L-GO) bone scaffold with triply periodic minimal surface (TPMS) structure was prepared using fused deposition modeling (FDM). The FTIR results revealed successful grafting of L-lysine onto GO through the reaction between their -COOH and -NH2 groups. The macroscopic and microscopic morphology characterization indicated that the PLA/L-GO scaffolds exhibited an characteristics of dynamic diameter changes, with good interlayer bonding. It was noteworthy that the L-lysine modification promoted the dispersion of GO and the interfacial bonding with the PLA matrix, as characterized by SEM. As a result, the PLA/0.1L-GO scaffold exhibited higher compressive strength (13.2 MPa) and elastic modulus (226.8 MPa) than PLA/0.1GO. Moreover, PLA/L-GO composite scaffold exhibited superior biomineralization capacity and cell response compared to PLA/GO. In summary, L-lysine not only improved the dispersion and interfacial bonding of GO with PLA, enhancing the mechanical properties, but also improved the biological properties. This study suggests that biomolecules like L-lysine may replace traditional modifiers as an innovative bio-modifier to improve the performance of polymer/inorganic composite biomaterials.

Effect of Heat Treatment on the Material Property and Cell Viability of Wire Arc Additively Manufactured Ti6Al4 V

Wire arc additive manufacturing (WAAM) holds promise for producing medium to large industrial components. Application of WAAM in the manufacturing of biomedical materials has not yet been evaluated. The current study addresses two key research questions: first, the suitability of the WAAMed Ti6Al4V alloy for biomedical applications, and second, the effect of Ti6Al4V's constituents (α and β phases) on the cell viability. The WAAMed Ti6Al4V alloy was fabricated (as-deposited: AD) using a metal inert gas (MIG)-based wire arc system using an in-house designed shielding chamber filled with argon. Subsequently, samples were subjected to solution treatment (950 °C for 1 h), followed by aging at 480 °C (T1), 530 °C (T2), and 580 °C (T3) for 8 h and subsequent normalization to ambient conditions. Microstructural analysis revealed ∼45.45% of α'-Ti colonies in the as-deposited samples, reducing to 23.26% postaging at 580 °C (T3). The α-lath thickness and interstitial oxygen content in the sample were observed to be proportional to the aging temperature, peaking at 580 °C (T3). Remarkably, during tribocorrosion analysis in simulated body fluid, the 580 °C-aged T3 sample displayed the lowest corrosion rate (7.9 μm/year) and the highest coefficient of friction (CoF) at 0.58, showing the effect of increasing oxygen content in the alloy matrix. Cell studies showed significant growth at 530 and 580 °C by day 7, correlated with higher oxygen content, while other samples had declining cell density. Additionally, optimal metallurgical property ranges were identified to enhance the Ti6Al4V alloy's biocompatibility, providing crucial insights for biomedical implant development.

[New Advances in the Application of Bacterial Cellulose Composite Materials in the Field of Bone Tissue Engineering]

Bacterial cellulose (BC) is a type of extracellular polymeric nanomaterial secreted by microorganisms over the course of their growth. It has gained significant attention in the field of bone tissue engineering due to its unique structure of three-dimensional fibrous network, excellent biocompatibility, biodegradability, and exceptional mechanical properties. Nevertheless, BC still has some weaknesses, including low osteogenic activity, a lack of antimicrobial properties, small pore size, issues with the degradation rate, and a mismatch in bone tissue regeneration, limiting its standalone use in the field of bone tissue engineering. Therefore, the modification of BC and the preparation of BC composite materials have become a recent research focus. Herein, we summarized the relationships between the production, modification, and bone repair applications of BC. We introduced the methods for the preparation and the modification of BC. Additionally, we elaborated on the new advances in the application of BC composite materials in the field of bone tissue engineering. We also highlighted the existing challenges and future prospects of BC composite materials.

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.

Recent advances in cellulose nanocrystals-based antimicrobial agents

Over the past five years, there has been growing interest in the design of modified cellulose nanocrystals (CNCs) as nanoscale antimicrobial agents in potential end-user applications such as food preservation/packaging, additive manufacturing, biomedical and water purification. The interest of applying CNCs-based antimicrobial agents arise due to their abilities to be derived from renewable bioresources and their excellent physicochemical properties including rod-like morphologies, large specific surface area, low toxicity, biocompatibility, biodegradability and sustainability. The presence of ample surface hydroxyl groups further allows easy chemical surface modifications for the design of advanced functional CNCs-based antimicrobial materials. Furthermore, CNCs are used to support antimicrobial agents that are subjected to instability issues. The current review summarizes recent progress in CNC-inorganic hybrid-based materials (Ag and Zn nanoparticles, other metal/metal oxide) and CNC-organic hybrid-based materials (polymers, chitosan, simple organic molecules). It focuses on their design, syntheses and applications with a brief discussion on their probable modes of antimicrobial action whereby the roles of CNCs and/or the antimicrobial agents are highlighted.

Properties and antimicrobial activity of wheat-straw nanocellulose-arabinoxylan acetate composite films incorporated with silver nanoparticles

In the current study, the novel eco-friendly and biodegradable nanocomposite films (NC-AXAc) were prepared from wheat-straw NC and AXAc with improved functional properties. NC derived from wheat-straw cellulose has a fibre-like structure with mean-particle size in the 340-520 nm range. AX derived AXAc was prepared with Degree of Substitution (DS) in the range of 1.85-1.89. Furthermore, to enhance antimicrobial properties, AgNPs were prepared via the reduction method using NaBH4 and added into the concentration of 4 × 10-4M into the emulsion forming composite films. The silver nanoparticles (AgNPs) incorporated in the composite exhibited an average size of 40-70 nm and a surface plasmon resonance (SPR) absorption peak at 395 nm. The high-resolution XPS spectrum of the Ag element showed that the two peaks at around 374.2 eV (Ag3d3/2) and 368.2 eV (Ag3d5/2) clearly revealed the metallic Ag existence in composite films. SEM analysis revealed the coarse and heterogeneous morphology of AgNPs incorporated films. The AgNPs incorporated composites exhibited good mechanical, thermal stability, and antimicrobial activity. The results suggested that AgNPs incorporated NC-AXAc composites could be used as a potential biodegradable antimicrobial nanocomposite in active food packaging systems for shelf-life extension of perishable commodities.

Rapid and persistent bactericidal cotton fabrics finished facilely with reactive N-halamine

Cotton fabrics (CFs) with persistent and rapid bactericidal capability would be of great significance for daily health protection because CFs are very suitable for the growth and reproduction of microorganisms. Herein, we developed a reactive N-halamine compound, 3-(3-hydroxypropyl diisocyanate)-5,5-dimethylhydantoin (IPDMH), that can be covalently bound to a CF to generate a bactericidal CF after chlorination (CF-DMF-Cl) without damaging its surface morphology. The antibacterial rates of CF-DMF-Cl (0.5 wt% IPDMH) against the gram-negative bacterium Escherichia coli (E. coli) and gram-positive bacterium Staphylococcus aureus (S. aureus) reached 99.99 % and were maintained at 90 % (against E. coli) and 93.5 % (against S. aureus) after 50 laundering cycles. The combination of contact killing and release killing mechanisms by CF-PDM-Cl leads to its rapid and persistent bactericidal activity. In addition, CF-DMF-Cl exhibits adequate biocompatibility, well-maintained mechanical properties, air/water vapor permeability and whiteness. Therefore, the proposed CF-DMF-Cl has great potential applications as a bactericidal CF for use in medical textiles, sportswear, home dressings, and so on.

Physiologic Response Evaluation of Human Foetal Osteoblast Cells within Engineered 3D-Printed Polylactic Acid Scaffolds

Large bone defect treatments have always been one of the important challenges in clinical practice and created a huge demand for more efficacious regenerative approaches. The bone tissue engineering (BTE) approach offered a new alternative to conventional bone grafts, addressing all clinical needs. Over the past years, BTE research is focused on the study and realisation of new biomaterials, including 3D-printed supports to improve mechanical, structural and biological properties. Among these, polylactic acid (PLA) scaffolds have been considered the most promising biomaterials due to their good biocompatibility, non-toxic biodegradability and bioresorbability. In this work, we evaluated the physiological response of human foetal osteoblast cells (hFOB), in terms of cell proliferation and osteogenic differentiation, within oxygen plasma treated 3D-printed PLA scaffolds, obtained by fused deposition modelling (FDM). A mechanical simulation to predict their behaviour to traction, flexural or torque solicitations was performed. We found that: 1. hFOB cells adhere and grow on scaffold surfaces; 2. hFOB grown on oxygen plasma treated PLA scaffolds (PLA_PT) show an improvement of cell adhesion and proliferation, compared to not-plasma treated scaffolds (PLA_NT); 3. Over time, hFOB penetrate along strands, differentiate, and form a fibrous matrix, tissue-like; 4. 3D-printed PLA scaffolds have good mechanical behaviour in each analysed configuration. These findings suggest that 3D-printed PLA scaffolds could represent promising biomaterials for medical implantable devices in the orthopaedic field.

3D printing of cellulose nanocrystals based composites to build robust biomimetic scaffolds for bone tissue engineering

Cellulose nanocrystals (CNC) are drawing increasing attention in the fields of biomedicine and healthcare owing to their durability, biocompatibility, biodegradability and excellent mechanical properties. Herein, we fabricated using fused deposition modelling technology 3D composite scaffolds from polylactic acid (PLA) and CNC extracted from Ficus thonningii. Scanning electron microscopy revealed that the printed scaffolds exhibit interconnected pores with an estimated average pore size of approximately 400 µm. Incorporating 3% (w/w) of CNC into the composite improved PLA mechanical properties (Young's modulus increased by ~ 30%) and wettability (water contact angle decreased by ~ 17%). The mineralization process of printed scaffolds using simulated body fluid was validated and nucleation of hydroxyapatite confirmed. Additionally, cytocompatibility tests revealed that PLA and CNC-based PLA scaffolds are non-toxic and compatible with bone cells. Our design, based on rapid 3D printing of PLA/CNC composites, combines the ability to control the architecture and provide improved mechanical and biological properties of the scaffolds, which opens perspectives for applications in bone tissue engineering and in regenerative medicine.

Magnetostrictive alloys: Promising materials for biomedical applications

Magnetostrictive alloys have attracted increasing attention in biomedical applications because of the ability to generate reversible deformation in the presence of external magnetic fields. This review focuses on the advances in magnetostrictive alloys and their biomedical applications. The theories of magnetostriction are systematically summarized. The different types of magnetostrictive alloys and their preparation methods are also reviewed in detail. The magnetostrictive strains and phase compositions of typical magnetostrictive alloys, including iron based, rare-earth based and ferrite materials, are presented. Besides, a variety of approaches to preparing rods, blocks and films of magnetostriction materials, as well as the corresponding methods and setups for magnetostriction measurement, are summarized and discussed. Moreover, the interactions between magnetostrictive alloys and cells are analyzed and emphasis is placed on the transduction and transformation process of mechanochemical signals induced by magnetostriction. The latest applications of magnetostrictive alloys in remote microactuators, magnetic field sensors, wireless implantable devices and biodegradable implants are also reviewed. Furthermore, future research directions of magnetostrictive alloys are prospected with focus on their potential applications in remote cell actuation and bone repair.

The management of bone defect using long non-coding RNA as a potential biomarker for regulating the osteogenic differentiation process

Tissue engineered bone brings hope to the treatment of bone defects, and the osteogenic differentiation of stem cells is the key link. Inducing osteogenic differentiation of stem cells may be a potential approach to promote bone regeneration. In recent years, lncRNA has been studied in the field increasingly, which is believed can regulate cell cycle, proliferation, metastasis, differentiation and immunity, participating in a variety of physiology and pathology processes. At present, it has been confirmed that certain lncRNAs regulate the osteogenesis of stem cells and take part in mediating signaling pathways including Wnt/β-catenin, MAPK, TGF-β/BMP, and Notch pathways. Here, we provided an overview of lncRNA, reviewed its researches in the osteogenic differentiation of stem cells, emphasized the importance of lncRNA in bone regeneration, and focused on the roles of lncRNA in signaling pathways, in order to make adequate preparations for applying lncRNA to bone tissue Engineering, letting it regulate the osteogenic differentiation of stem cells for bone regeneration.

Evaluation of the multifunctional activity of silver bionanocomposites in environmental remediation and inhibition of the growth of multidrug-resistant pathogens

Imperata cylindrica cellulose supported Ag bionanocomposites purified industrial water and controlled the contagious diseases with high potential activity.

A silver-functionalized metal–organic framework with effective antibacterial activity

A metal–organic framework with alkene-functional groups was constructed and postsynthetically modified with Ag(i) for antibacterial applications.

In situ synthesis of hydroxyapatite nanorods on graphene oxide nanosheets and their reinforcement in biopolymer scaffold

Introduction

It is urgently needed to develop composite bone scaffold with excellent mechanical properties and bioactivity in bone tissue engineering. Combining graphene oxide (GO) and hydroxyapatite (HAP) for the reinforcement of biopolymer bone scaffold has emerged as a promising strategy. However, the dispersion of GO and HAP remains to be a big challenge.

Objectives

In this present work, the mechanical properties of GO and the bioactivity of and HAP were combined respectively via in situ synthesis for reinforcing biopolymer bone scaffold.

Methods

GO nanosheets were employed to in situ synthesize GO-HAP nanocomposite via hydrothermal reaction, in which their abundant oxygen-containing groups served as anchor sites for the chelation of Ca2+ and then Ca2+ absorbed HPO42- via electrovalent bonding to form homogeneously dispersed HAP nanorods. Thereby, the GO-HAP nanocomposite was blended with biopolymer poly-L-lactic acid (PLLA) for fabricating biopolymer scaffold by selective laser sintering (SLS).

Results

GO nanosheets were uniformly decorated with HAP nanorods, which were about 60 nm in length and 5 nm in diameter. The compressive strength and modulus of PLLA/12%GO-HAP were significantly increased by 53.71% and 98.80% compared to the pure PLLA scaffold, respectively, explained on the base of pull out, crack bridging, deflection and pinning mechanisms. Meanwhile, the mineralization experiments indicated the PLLA/GO-HAP scaffold displayed good bioactivity by inducing the formation of apatite layer. Besides, cell culturing experiments demonstrated the favorable cytocompatibility of scaffold by promoting cell adhesion and proliferation.

Conclusions

The present findings show the potential of PLLA/GO-HAP composite scaffold via in situ synthesis in bone tissue engineering.

Advances in Filament Structure of 3D Bioprinted Biodegradable Bone Repair Scaffolds

Conventional bone repair scaffolds can no longer meet the high standards and requirements of clinical applications in terms of preparation process and service performance. Studies have shown that the diversity of filament structures of implantable scaffolds is closely related to their overall properties (mechanical properties, degradation properties, and biological properties). To better elucidate the characteristics and advantages of different filament structures, this paper retrieves and summarizes the state of the art in the filament structure of the three-dimensional (3D) bioprinted biodegradable bone repair scaffolds, mainly including single-layer structure, double-layer structure, hollow structure, core-shell structure and bionic structures. The eximious performance of the novel scaffolds was discussed from different aspects (material composition, ink configuration, printing parameters, etc.). Besides, the additional functions of the current bone repair scaffold, such as chondrogenesis, angiogenesis, anti-bacteria, and anti-tumor, were also concluded. Finally, the paper prospects the future material selection, structural design, functional development, and performance optimization of bone repair scaffolds.

Monetite addition into gelatin based freeze-dried scaffolds for improved mechanical and osteogenic properties

This study was aimed at fabricating monetite nanoparticles impregnated gelatin-based composite scaffold to improve the chemical, mechanical and osteogenic properties. Scaffolds were fabricated using a freeze-drying technique of the slurry containing a varying proportion of gelatin and monetite. The lyophilized scaffolds were cross-linked with 0.25 wt% glutaraldehyde solution to obtain a three-dimensional (3D) interconnected porous microstructure with improved mechanical strength and stability in a physiological environment. The fabricated scaffolds possessed >80% porosity having 3D interconnected pore size distribution varying between 65 and 270 μm as evident from field emission scanning electron microscopy analysis. The average pore size of the prepared scaffold decreased with monetite addition as reflected in values of 210 μm for pure gelatin GM₀scaffold and 118 μm registered by GM₂₀scaffold. On increase in monetite content up to 20 wt% of total polymer concentration, compressive strength of the prepared scaffolds was increased from 0.92 MPa in pure gelatin-based GM₀to 2.43 MPa in GM₂₀. Up to 20 wt% of monetite reinforced composite scaffolds exhibited higher bioactivity as compared to that observed in pure gelatin-based GM₀scaffold. Simulated body fluid (SBF) study and alizarin red assays confirmed higher bio-mineralization ability of GM₂₀as compared to that exhibited by GM₀. Human preosteoblast cells (MG-63) revealed higher degree of filopodia and lamellipodia extensions and excellent spreading behavior to anchor with GM₂₀matrix as compared to that onto GM₀and GM₁₀. MTT assay and alkaline phosphatase staining study indicated that MG-63 cells found a more conducive environment to proliferate and subsequently differentiate into osteoblast lineage when exposed to GM₂₀scaffolds rather than to GM₀and GM₁₀. This study revealed that up to 20 wt% monetite addition in gelatin could improve the performance of prepared scaffolds and serve as an efficient candidate to repair and regenerate bone tissues at musculoskeletal defect sites.

2-Dodecylmalonic acid-mediated synthesis of mineralized hydroxyapatite amicable for bone cell growth on orthopaedic implant

The present study illustrates the use of 2-dodecylmalonic acid (MA) as a template in biomineralization-inspired synthesis of hydroxyapatite nanoparticles (HANPs). HANPs synthesized in presence of various concentrations of MA displayed varying particle size and shape. The smallest particle size (22-27 nm) was obtained for MA₂-HANP synthesized in presence of 37 µM MA. The critical micelle concentration (CMC) for MA at pH 9.0 relevant for mineralization was ∼35 µM. AFM analysis revealed that at a low concentration of 10 µM and pH 9.0, MA could generate oblong-shaped aggregates. At 40 µM, comparable to the concentration used to generate MA₂-HANP, the amphiphile self-assembled to form a spherical soft scaffold, which likely regulated spatial confinement of ions during mineralization and generated small size HANPs. Osteoblast-like MG-63 cells seeded on titanium wire (TW) coated with MA₂-HANP-incorporated collagen type I (H-TW) displayed enhanced cell proliferation, high expression of osteogenic differentiation marker genes (Col I, ALP, OCN and Runx2) and copious calcium mineral deposition after 14 days of growth. The nuanced role of the self-assembly process of an amphiphilic template in HANP mineralization unravelled in the present study can guide future scaffold design for biomineralization-inspired synthesis of HANPs tailored for bone tissue engineering applications.

Pre-oxidation induced in situ interface strengthening in biodegradable Zn/nano-SiC composites prepared by selective laser melting

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Zn/nano-SiC biocomposites were prepared via pre-oxidation and selective laser melting.

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In situ reaction improved the interface bonding between nano-SiC and the Zn matrix.

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The improved interfacial bonding enhanced the mechanical properties of the biocomposite.

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The biocomposite exhibited favorable biocompatibility on cell proliferation and adhesion.

Introduction

Nano-SiC has attracted great attention as ceramic reinforcement in metal matrix composites, but the weak interface bonding between them remains a bottleneck for efficient strengthening.

Objective

In this study, pre-oxidation treatments and selective laser melting (SLM) were employed to prepare Zn/nano-SiC biocomposites with strengthened interface bonding via in situ reaction.

Methods

Nano-SiC and Zn powders were pre-oxidized respectively, and then used to prepare Zn/nano-SiC biocomposites via SLM. The powder microstructure, and the interface characteristics and mechanical properties of the biocomposites were investigated. The degradation properties and cell response were analyzed to evaluate their feasibility for orthopedic applications.

Results

The results indicated that the pre-oxidation treatments generated a uniform oxide layer on the surface of both nano-SiC and Zn particles and the thickness of the oxide layer increased with pre-oxidation temperature. During the SLM process, the oxide layers not only improved the metal-ceramic wettability by reducing interface energy, but also induced in situ reaction to form chemical bonding between the Zn matrix and nano-SiC, thereby improving the interface bonding. Consequently, the Zn biocomposite reinforced by nano-SiC with a pre-oxidation temperature of 1000 °C (ZS1000 biocomposite) exhibited more transgranular fracture and significantly enhanced compressive yield strength of 171.5 MPa, which was 31.6% higher than that of the Zn biocomposite reinforced by nano-SiC without pre-oxidation. Moreover, the ZS1000 biocomposite presented slightly accelerated degradation which might be ascribed to the facilitated electron transfer by the interface product (Zn₂SiO₄). In addition, the ZS1000 biocomposite also showed appropriate biocompatibility for MG-63 cell adhesion, growth, and proliferation.

Conclusion

This study shows the potential practical applicability for the preparation of Zn-based biocomposites with strong interface bonding and mechanical properties for orthopedic applications.

Silver-doped bioglass modified scaffolds: A sustained antibacterial efficacy

Implant-related bacterial infection is a serious complication, which even causes implant failure. Silver (Ag) nanoparticles are broadly used antibacterial agents due to their excellent antibacterial ability and broad-spectrum bactericidal property. However, the significance of burst release cannot be entirely ignored. In this study, Ag doped mesoporous bioactive glasses (Ag-MBG) nanospheres were synthesized using modified Stöber method, then incorporated into poly L-lactic acid (PLLA) matrix to prepare the composite scaffolds via selective laser sintering (SLS) technology. Herein, Mesoporous bioactive glasses (MBG) sol had many negatively-charged silicon hydroxyl groups, which could adsorb positively-charged Ag ions by electrostatic interaction and eventually form Si-O-Ag bonds into MBG. Moreover, MBG promoted osteoblast colonization due to its continuous release of Si ions. The results showed the Ag-MBG/PLLA scaffold could sustainedly release Ag ions for 28 days, and exhibited significantly antibacterial ability against Escherichia coli, its bacterial inhibition rate was over 80%. In addition, the composite scaffold also showed good cytocompatibility. It may be concluded that the prepared Ag-MBG/PLLA scaffold has great potential to repair implant-associated bone infection.

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

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.

Polydopamine-decorated black phosphorous to enhance stability in polymer scaffold

Black phosphorous (BP) is recognized as an effective reinforcement for polymer scaffold because of its excellent mechanical property and biocompatibility. Nevertheless, its poor stability in physiological environment limits its application in bone repair. In this work, BP was modified with dopamine by self-polymerization approach (donated as BP@PDA) to improve its stability, and then was introduced into poly-L-lactic acid (PLLA) scaffold fabricated by selective laser sintering technology. Results showed the compressive and tensile strength of PLLA/BP@PDA scaffold were improved by 105% and 50%, respectively. The enhanced strength was ascribed to the increased stability of BP and the improved compatibility of BP@PDA with PLLA matrix after modifying with polydopamine. Simultaneously, the bioactivity of PLLA scaffold was significantly improved. It was attributed to that BP@PDA provided the sustained source ofPO43-ions which could capture Ca²⁺ions from physiological medium to facilitatein situbiomineralization, thereby promoting cell adhesion, proliferation and differentiation. This study demonstrated the great potential of BP@PDA in bone repair.

Construction of Fe3O4-Loaded Mesoporous Carbon Systems for Controlled Drug Delivery

Magnetite (Fe₃O₄) nanoparticles as drug carriers can achieve precise drug target due to their magnetic property. However, they are easy to aggregate in the physiological environment, which obviously limits their application in drug delivery. The development of the Fe-MIL-88B-derived method to construct the Fe₃O₄-loaded mesoporous carbon (Fe₃O₄/carbon) system is a feasible strategy to solve the issue. First, iron atoms evenly distribute in the organic links through coordination bonds in Fe-MIL-88B. After the carbonization of Fe-MIL-88B, mesoporous carbon acts as a barrier to prevent the aggregation of Fe₃O₄ nanoparticles. Herein, Fe-MIL-88B particles were fabricated by the hydrothermal method and then pyrolyzed to construct Fe₃O₄/carbon systems. Results showed that Fe₃O₄ nanoparticles uniformly in situ grew on mesoporous carbon generated by the carbonization of organic components. More encouragingly, the Fe₃O₄/carbon system loaded with DOX demonstrated pH-responsive DOX release, efficient delivery of DOX into cancer cells, and significant cancer cell killing ability. Therefore, the Fe₃O₄/carbon systems prepared by the Fe-MIL-88B-derived method might open up a way for targeted and controlled drug delivery.

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.

Constructing core-shell structured BaTiO3@carbon boosts piezoelectric activity and cell response of polymer scaffolds

Piezoelectric composites have shown great potential in constructing electrical microenvironment for bone healing since their integration of polymer flexibility and ceramic piezoelectric coefficient. Herein, core-shell structured BaTiO₃@carbon (BT@C) hybrid nanoparticles were prepared by in situ oxidative self-polymerization and template carbonization. Then the BT@C was introduced into polyvinylidene fluoride (PVDF) scaffolds manufactured by selective laser sintering. On one hand, the carbon shell could strengthen the local electric field loaded on BT in poling process owing to it served as a diffusion layer to provide space for charge transfer and accumulation. In this case, more electric domain within BT would be aligned along the polarization field direction and thus promoted the paly of BT's piezoelectric activity. On the other hand, the carbon shell could induce the formation of β phase due to the sp² hybrid-bonded carbon atoms in carbon shell forming electrostatic interaction with hydrogen atoms in PVDF chains, which further enhanced the piezoelectric response of the scaffolds. Results showed that the scaffold presented augmented piezoelectric performance with output voltage of 5.7 V and current of 79.8 nA. The improved electrical signals effectively accelerated cell proliferation and differentiation. Furthermore, the scaffold displayed improved mechanical performance due to rigid particle strengthen effect.