Ag modified mesoporous bioactive glass nanoparticles for enhanced antibacterial activity in 3D infected skin model

Bioactive Glass in Tissue Regeneration: Unveiling Recent Advances in Regenerative Strategies and Applications

Bioactive glass (BG) is a class of biocompatible, biodegradable, multifunctional inorganic glass materials, which is successfully used for orthopedic and dental applications, with several products already approved for clinical use. Apart from exhibiting osteogenic properties, BG is also known to be angiogenic and antibacterial. Recently, BG's role in immunomodulation has been gradually revealed. While the therapeutic effect of BG is mostly reported in the context of bone and skin-related regeneration, its application in regenerating other tissues/organs, such as muscle, cartilage, and gastrointestinal tissue, has also been explored recently. The strategies of applying BG have also expanded from powder or cement form to more advanced strategies such as fabrication of composite polymer-BG scaffold, 3D printing of BG-loaded scaffold, and BG-induced extracellular vesicle production. This review presents a concise overview of the recent applications of BG in regenerative medicine. Various regenerative strategies of BG will be first introduced. Next, the applications of BG in regenerating various tissues/organs, such as bone, cartilage, muscle, tendon, skin, and gastrointestinal tissue, will be discussed. Finally, summarizing clinical applications of BG for tissue regeneration will conclude, and outline future challenges and directions for the clinical translation of BG.

Gold Nanoparticles Confined in Mesoporous Bioactive Glass for Periodontitis Therapy

Periodontitis is a chronic disease caused by bacterial infection and is characterized with alveolar bone resorption. Bone regeneration in periodontitis remains a critical challenge because bacterial infection induced an unfavorable microenvironment for osteogenesis. Therefore, it is necessary to design proper therapeutic platforms to control bacterial infection and promote bone regeneration. Herein, mesoporous bioactive glass (MBG) with different pore sizes (3.0, 4.3, and 12.3 nm) was used as an in situ reactor to confine the growth of gold nanoparticles (Au NPs), forming MBG@Au hybrids which combine the osteoconductivity of MBG and antibacterial properties of Au NPs. Upon near-infrared (NIR) irradiation, the MBG@Au NPs showed efficient antibacterial properties both in vitro and in vivo. Besides, the osteogenesis properties of MBG@Au also improved under NIR irradiation. Furthermore, the in vivo results demonstrated that MBG@Au can effectively promote alveolar bone regeneration and realize the healing of serious periodontitis.

Oxidized alginate-gelatin (ADA-GEL)/silk fibroin/Cu-Ag doped mesoporous bioactive glass nanoparticle-based hydrogels for potential wound care treatments

The present work focuses on developing 5% w/v oxidized alginate (alginate di aldehyde, ADA)-7.5% w/v gelatin (GEL) hydrogels incorporating 0.25% w/v silk fibroin (SF) and loaded with 0.3% w/v Cu-Ag doped mesoporous bioactive glass nanoparticles (Cu-Ag MBGNs). The microstructural, mechanical, and biological properties of the composite hydrogels were characterized in detail. The porous microstructure of the developed ADA-GEL based hydrogels was confirmed by scanning electron microscopy, while the presence of Cu-Ag MBGNs in the synthesized hydrogels was determined using energy dispersive x-ray spectroscopy. The incorporation of 0.3% w/v Cu-Ag MBGNs reduced the mechanical properties of the synthesized hydrogels, as investigated using micro-tensile testing. The synthesized ADA-GEL loaded with 0.25% w/v SF and 0.3% w/v Cu-Ag MBGNs showed a potent antibacterial effect againstEscherichia coliandStaphylococcus aureus. Cellular studies using the NIH3T3-E1 fibroblast cell line confirmed that ADA-GEL films incorporated with 0.3% w/v Cu-Ag MBGNs exhibited promising cellular viability as compared to pure ADA-GEL (determined by WST-8 assay). The addition of SF improved the biocompatibility, degradation rate, moisturizing effects, and stretchability of the developed hydrogels, as determinedin vitro. Such multimaterial hydrogels can stimulate angiogenesis and exhibit desirable antibacterial properties. Therefore further (in vivo) tests are justified to assess the hydrogels' potential for wound dressing and skin tissue healing applications.

Osteogenic-angiogenic coupled response of cobalt-containing mesoporous bioactive glasses in vivo

The incorporation of cobalt ions into the composition of bioactive glasses has emerged as a strategy of interest for bone regeneration purposes. In the present work, we have designed a set of bioactive mesoporous glasses SiO2-CaO-P2O5-CoO (Co-MBGs) with different amounts of cobalt. The physicochemical changes introduced by the Co2+ ion, the in vitro effects of Co-MBGs on preosteoblasts and endothelial cells and their in vivo behaviour using them as bone grafts in a sheep model were studied. The results show that Co2+ ions neither destroy mesoporous ordering nor inhibit in vitro bioactive behaviour, exerting a dual role as network former and modifier for CoO concentrations above 3 % mol. On the other hand, the activity of Co-MBGs on MC3T3-E1 preosteoblasts and HUVEC vascular endothelial cells is dependent on the concentration of CoO present in the glass. For low Co-MBGs concentrations (1mg/ml) cell viability is not affected, while the expression of osteogenic (ALP, RUNX2 and OC) and angiogenic (VEGF) genes is stimulated. For Co-MBGs concentration of 5 mg/ml, cell viability decreases as a function of the CoO content. In vivo studies show that the incorporation of Co2+ ions to the MBGs improves the bone regeneration activity of these materials, despite the deleterious effect that this ion has on bone-forming cells for any of the Co-MBG compositions studied. This contradictory effect is explained by the marked increase in angiogenesis that takes place inside the bone defect, leading to an angiogenesis-osteogenesis coupling that compensates for the partial decrease in osteoblast cells. STATEMENT OF SIGNIFICANCE: The development of new bone grafts implies to address the need for osteogenesis-angiogenesis coupling that allows bone regeneration with viable tissue in the long term. In this sense the incorporation of cobalt ions into the composition of bioactive glasses has emerged as a strategy of great interest in this field. Due to the potential cytotoxic effect of cobalt ions, there is an important controversy regarding the suitability of their incorporation in bone grafts. In this work, we address this controversy after the implantation of cobalt-doped mesoporous bioactive glasses in a sheep model. The incorporation of cobalt ions in bioactive glasses improves the bone regeneration ability of these bone grafts, due to enhancement of the angiogenesis-osteogenesis coupling.

Bone-like apatite formation in biocompatible phosphate-crosslinked bacterial cellulose-based hydrogels for bone tissue engineering applications

Addressing major bone injuries is a challenge in bone regeneration, necessitating innovative 3D hydrogel-based therapeutic approaches to enhance scaffold properties for better bioactivity. Bacterial cellulose (BC) is an excellent scaffold for bone tissue engineering due to its biocompatibility, high porosity, substantial surface area, and remarkable mechanical strength. However, its practical application is limited due to a lack of inherent osteogenic activity and biomineralization ability. In this study, we synthesized bone-like apatite in biocompatible BC hydrogel by introducing phosphate groups. Hydrogels were prepared using fibrous BC, acrylamide (AM), and bis [2-methacryloyloxy] ethyl phosphate (BMEP) as a crosslinker through free radical polymerization (P-BC-PAM). P-BC-PAM hydrogels exhibited outstanding compressive mechanical properties, highly interconnected porous structures, good swelling, and biodegradable properties. BMEP content significantly influenced the physicochemical and biological properties of the hydrogels. Increasing BMEP content enhanced the fibrous structure, porosity from 85.1 % to 89.5 %, and compressive mechanical strength. The optimized hydrogel (2.0P-BC-PAM) displayed maximum compressive stress, toughness, and elastic modulus at 75 % strain: 221 ± 0.08 kPa, 24,674.2 ± 978 kPa, and 11 ± 0.47 kPa, respectively. P-BC-PAM hydrogels underwent biomineralization in simulated body fluid (SBF) for 14 days, forming bone-like apatite with a Ca/P ratio of 1.75, similar to hydroxyapatite. Confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM), this suggests their potential as scaffolds for bone tissue engineering. MC3T3-E1 osteoblast cells effectively attached and proliferated on P-BC-PAM. In summary, this study contributes insights into developing phosphate-functionalized BC-based hydrogels with potential applications in bone tissue engineering.

A biomimetic multi-layer scaffold with collagen and zinc doped bioglass as a skin-regeneration agent in full-thickness injuries and its effects in vitro and in vivo

Due to the multilayer structure of skin tissue, the fabrication of a 3-layer scaffold could result in planned dermal regeneration. Herein, polyurethane (PU) and polycaprolactone (PCL), as a function of their mechanical stability and collagen due to its arginine-glycine-aspartic acid sequences, zinc ions because of overcoming the common problems of biological factors were employed. The scaffolds' physical, mechanical, and biological properties were examined by SEM, FTIR, contact angle, mechanical tensile, bacteriocidal efficacy, and hemolysis. Also, after L-929 fibroblast seeding, their biological activity was determined by SEM, DAPI, and MTT assays. Then, the cell-seeded scaffolds were implanted in full-thickness wounds of rats and evaluated by wound closure, histological, and molecular techniques. The in vivo studies showed better wound closure with the composite scaffold containing zinc ions. While its dermal re-organization was retarded in the presence of zinc ions compared to the composite scaffold containing non-doped bioglass. Despite this, the doped composite scaffold indicated better observations with the histological evaluations than the nontreated and bare scaffold groups. Real-time PCR confirmed the higher expression of FGF2 and FGFR genes in rats treated with the zinc-doped composite scaffold. In conclusion, PU/PCL-collagen/PCL-collagen containing the doped or non-doped nanoparticles showed better potential to heal dermal injuries.

Wound healing performance of electrospun PVA/70S30C bioactive glass/Ag nanoparticles mats decorated with curcumin: In vitro and in vivo investigations

Biocompatible fibrous scaffold containing polyvinyl alcohol (PVA), 70S30C bioactive glass (BG), silver (Ag) nanoparticles and curcumin (Cur) was fabricated through electrospinning method. Scanning electron microscope (SEM) and Field emission scanning electron microscopy (FESEM) were employed to investigate the morphological characteristics of the scaffolds. In addition, biodegradability, hydrophilicity, and contact angle were studied as criteria for evaluating physical properties of the scaffolds. Tensile strength was reported to be 0.971 ± 0.093 MPa. Also, the viability of fibroblasts after 7 days of cell culture was 93.58 ± 1.36 %. The antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria was illustrated using inhibition zones of 13.12 ± 0.69 and 14.21 ± 1.37 mm, respectively. Histological results revealed that tissue regeneration after 14 days of surgery was much higher for the dressing group compared to the blank group. According to the obtained results, the authors introduce the PVA-BG-Ag-Cur scaffold as a promising candidate for skin tissue engineering applications.

Borophosphate glasses as active agents for antimicrobial hydrogels

Herein we report the synthesis of transition-metal-free potassium borophosphate glasses and their application as bactericidal and bacteriostatic material. The antimicrobial activity was achieved through a simple change in the molar ratio of boron and phosphorus atoms, making borophosphate glass soluble in water. The glasses were analyzed by X-ray powder diffraction, Raman spectroscopy, laser-induced breakdown spectroscopy, and water absorption. The addition of a boron compound is required to obtain potassium-based phosphate glasses. Moreover, the change in the phosphorus and boron molar ratio (P/B), 2, 1 or 0.5 affects the glass solubilization in water, which increases with the phosphorus content. The glass materials were submitted to tests of biological activity against the bacteria Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. These water-soluble borophosphate glasses were employed in the development of hydrogel formulations using Carbopol®. Phosphorous-rich samples at a concentration of 15 % (w/w) in hydrogel showed better antimicrobial activity against S. aureus and E. coli, when compared to other samples, including commercial alcohol hand sanitizer gel, with an average size of the inhibition halo of 24.02±1.43 and 19.24±1.63mm, respectively.

Non-Coding-RNA-Activated Core/Chitosan Shell Nanounits Coated with Polyetheretherketone for Promoting Bone Regeneration and Osseointegration via Osteoimmunology

Bone implant outcome and bone regeneration properties can be improved by the immunomodulation of exosomes (Exos) derived from bone marrow mesenchymal stem cells (BMSCs), which contain cytokines, signaling lipids, and regulatory miRNAs. Analysis of miRNAs in BMSCs-derived exosomes showed that miR-21a-5p exhibited the highest expression and was associated with the NF-κB pathway. Hence, we developed an implant with miR-21a-5p functionality to promote bone incorporation by immunoregulation. Mediated by the potent interaction between tannic acid (TA) and biomacromolecules, the tannic acid modified mesoporous bioactive glass nanoparticles coated with miR-21a-5p (miR-21a-5p@T-MBGNs) were reversibly attached to TA-modified polyetheretherketone (T-PEEK). Cocultured cells could phagocytose miR-21a-5p@T-MBGNs slowly released from miR-21a-5p@T-MBGNs loaded T-PEEK (miMT-PEEK). Moreover, miMT-PEEK boosted macrophage M2 polarization via the NF-κB pathway to increase BMSCs osteogenic differentiation. In vivo testing of miMT-PEEK in the rat air-pouch model and rat femoral drilling model indicated effective macrophage M2 polarization, new bone formation, and excellent osseointegration. Overall, the osteoimmunomodulation of the miR-21a-5p@T-MBGNs-functionalized implant promoted osteogenesis and osseointegration.

Cellular Uptake of Modified Mesoporous Bioactive Glass Nanoparticles for Effective Intracellular Delivery of Therapeutic Agents

Introduction

There has recently been a surge of interest in mesoporous bioactive glass nanoparticles (MBGNs) as multi-functional nanocarriers for application in bone-reconstructive and -regenerative surgery. Their excellent control over their structural and physicochemical properties renders these nanoparticles suitable for the intracellular delivery of therapeutic agents to combat degenerative bone diseases, such as bone infection, or bone cancer. Generally, the therapeutic efficacy of nanocarriers strongly depends on the efficacy of their cellular uptake, which is determined by numerous factors including cellular features and the physicochemical characteristics of nanocarriers, particularly surface charge. In this study, we have systematically investigated the effect of the surface charge of MBGNs doped with copper as a model therapeutic agent on cellular uptake by both macrophages and pre-osteoblast cells involved in bone healing and bone infections to guide the future design of MBGN-based nanocarriers.

Methods

Cu-MBGNs with negative, neutral, and positive surface charges were synthesized and their cellular uptake efficiency was assessed. Additionally, the intracellular fate of internalized nanoparticles along with their ability to deliver therapeutic cargo was studied in detail.

Results

The results showed that both cell types internalized Cu-MBGNs regardless of their surface charge, indicating that cellular uptake of nanoparticles is a complex process influenced by multiple factors. This similarity in cellular uptake was attributed to the formation of a protein corona surrounding the nanoparticles when exposed to protein-rich biological media, which masks the original nanoparticle surface. Once internalized, the nanoparticles were found to mainly colocalize with lysosomes, exposing them to a more compartmentalized and acidic environment. Furthermore, we verified that Cu-MBGNs released their ionic components (Si, Ca, and Cu ions) in both acidic and neutral environments, leading to the delivery of these therapeutic cargos intracellularly.

Conclusion

The effective internalization of Cu-MBGNs and their ability to deliver cargos intracellularly highlight their potential as intracellular delivery nanocarriers for bone-regenerative and -healing applications.

Mesoporous Bioactive Nanoparticles for Bone Tissue Applications

Research in nanomaterials with applications in bone regeneration therapies has experienced a very significant advance with the development of bioactive mesoporous nanoparticles (MBNPs). These nanomaterials consist of small spherical particles that exhibit chemical properties and porous structures that stimulate bone tissue regeneration, since they have a composition similar to that of conventional sol-gel bioactive glasses and high specific surface area and porosity values. The rational design of mesoporosity and their ability to incorporate drugs make MBNPs an excellent tool for the treatment of bone defects, as well as the pathologies that cause them, such as osteoporosis, bone cancer, and infection, among others. Moreover, the small size of MBNPs allows them to penetrate inside the cells, provoking specific cellular responses that conventional bone grafts cannot perform. In this review, different aspects of MBNPs are comprehensively collected and discussed, including synthesis strategies, behavior as drug delivery systems, incorporation of therapeutic ions, formation of composites, specific cellular response and, finally, in vivo studies that have been performed to date.

Unraveling the mechanisms of inhibition of silver-doped bioactive glass-ceramic particles

Infections are a major concern in orthopedics. Antibacterial agents such as silver ions are of great interest as broad-spectrum biocides and have been incorporated into bioactive glass-ceramic particles to control the release of ions within a therapeutic concentration and provide tissue regenerative properties. In this work, the antibacterial capabilities of silver-doped bioactive glass (Ag-BG) microparticles were explored to reveal the unedited mechanisms of inhibition against methicillin-resistant Staphylococcus aureus (MRSA). The antibacterial properties were not limited to the delivery of silver ions but rather a combination of antibacterial degradation by-products. For example, nano-sized debris punctured holes in bacteria membranes, osmotic effects, and reactive oxygen species causing oxidative stress and almost 40% of the inhibition. Upon successive Ag-BG treatments, MRSA underwent phenotypic and genomic mutations which were not only insufficient to develop resistance but instead, the clones became more sensitive as the treatment was re-delivered. Additionally, the unprecedented restorative functionality of Ag-BG allowed the effective use of antibiotics that MRSA resists. The synergy mechanism was mainly identified for combinations targeting cell-wall activity and their action was proven in biofilm-like and virulent conditions. Unraveling these mechanisms may offer new insights into how to tailor healthcare materials to prevent or debilitate infections and join the fight against antibiotic resistance in clinical cases.

Scaffolds in the microbial resistant era: Fabrication, materials, properties and tissue engineering applications

Due to microbial infections dramatically affect cell survival and increase the risk of implant failure, scaffolds produced with antimicrobial materials are now much more likely to be successful. Multidrug-resistant infections without suitable prevention strategies are increasing at an alarming rate. The ability of cells to organize, develop, differentiate, produce a functioning extracellular matrix (ECM) and create new functional tissue can all be controlled by careful control of the extracellular microenvironment. This review covers the present state of advanced strategies to develop scaffolds with antimicrobial properties for bone, oral tissue, skin, muscle, nerve, trachea, cardiac and other tissue engineering applications. The review focuses on the development of antimicrobial scaffolds against bacteria and fungi using a wide range of materials, including polymers, biopolymers, glass, ceramics and antimicrobials agents such as antibiotics, antiseptics, antimicrobial polymers, peptides, metals, carbon nanomaterials, combinatorial strategies, and includes discussions on the antimicrobial mechanisms involved in these antimicrobial approaches. The toxicological aspects of these advanced scaffolds are also analyzed to ensure future technological transfer to clinics. The main antimicrobial methods of characterizing scaffolds’ antimicrobial and antibiofilm properties are described. The production methods of these porous supports, such as electrospinning, phase separation, gas foaming, the porogen method, polymerization in solution, fiber mesh coating, self-assembly, membrane lamination, freeze drying, 3D printing and bioprinting, among others, are also included in this article. These important advances in antimicrobial materials-based scaffolds for regenerative medicine offer many new promising avenues to the material design and tissue-engineering communities.

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Antibacterial, antifungal and antibiofilm scaffolds.

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Antimicrobial scaffold fabrication techniques.

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Antimicrobial biomaterials for tissue engineering applications.

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Antimicrobial characterization methods of scaffolds.

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Bone, oral tissue, skin, muscle, nerve, trachea, cardiac, among other applications.

Achievements in Mesoporous Bioactive Glasses for Biomedical Applications

Nowadays, mesoporous bioactive glasses (MBGs) are envisaged as promising candidates in the field of bioceramics for bone tissue regeneration. This is ascribed to their singular chemical composition, structural and textural properties and easy-to-functionalize surface, giving rise to accelerated bioactive responses and capacity for local drug delivery. Since their discovery at the beginning of the 21st century, pioneering research efforts focused on the design and fabrication of MBGs with optimal compositional, textural and structural properties to elicit superior bioactive behavior. The current trends conceive MBGs as multitherapy systems for the treatment of bone-related pathologies, emphasizing the need of fine-tuning surface functionalization. Herein, we focus on the recent developments in MBGs for biomedical applications. First, the role of MBGs in the design and fabrication of three-dimensional scaffolds that fulfil the highly demanding requirements for bone tissue engineering is outlined. The different approaches for developing multifunctional MBGs are overviewed, including the incorporation of therapeutic ions in the glass composition and the surface functionalization with zwitterionic moieties to prevent bacterial adhesion. The bourgeoning scientific literature on MBGs as local delivery systems of diverse therapeutic cargoes (osteogenic/antiosteoporotic, angiogenic, antibacterial, anti-inflammatory and antitumor agents) is addressed. Finally, the current challenges and future directions for the clinical translation of MBGs are discussed.

Facile post modification synthesis of copper-doped mesoporous bioactive glass with high antibacterial performance to fight bone infection

Successful treatment of infected bone defects caused by multi-drug resistant bacteria (MDR) has become a major clinical challenge, stressing the urgent need for effective antibacterial bone graft substitutes. Mesoporous bioactive glass nanoparticles (MBGNs), a rapidly emerging class of nanoscale biomaterials, offer specific advantages for the development of biomaterials to treat bone infection due to endowed antibacterial features. Herein, we propose a facile post-modification sol-gel strategy to synthesize effective antibacterial MBGNs doped with copper ions (Cu-PMMBGNs). In this strategy, amine functional groups as chelating agents were introduced to premade mesoporous silica nanoparticles (MSNs) which further facilitate the incorporation of high content of calcium (∼17 mol%) and copper ions (∼8 mol%) without compromising nanoparticle shape, mesoporosity, and homogeneity. The resulting nanoparticles were degradable and showed rapidly induce abundant deposition of apatite crystals on their surface upon soaking in simulated body fluids (SBF) after 3 days. Cu-PMMBGNs exhibited a dose-dependent inhibitory effect on Methicillin-resistant Staphylococcus aureus (MRSA) bacteria, which are common pathogens causing severe bone infections. Most importantly, the nanoparticles containing 5 mol% copper ions at concentrations of 500 and 1000 μg.mL^-1 showed highly effective antibacterial performance as reflected by a 99.9 % reduction of bacterial viability. Nanoparticles at a concentration of 500 μg.mL^-1 showed no significant cytotoxicity toward preosteoblast cells (∼85-89 % cell viability) compared to the control group. In addition, the nanoscale properties of synthesized Cu-PMMBGNs (∼100 nm in size) facilitated their internalization into preosteoblast cells, which highlights their potential as intracellular carriers in combating intracellular bacteria. Therefore, these copper-doped nanoparticles hold strong promise for use as an antibacterial component in antibacterial bone substitutes such as hydrogels, nanocomposites, and coatings.

Triple-Networked Hybrid Hydrogels Reinforced with Montmorillonite Clay and Graphene Nanoplatelets for Soft and Hard Tissue Regeneration

Hydrogel is a three-dimensional (3D) soft and highly hydrophilic, polymeric network that can swell in water and imbibe a high amount of water or biological fluids. Hydrogels have been used widely in various biomedical applications. Hydrogel may provide a fluidic tissue-like 3D microenvironment by maintaining the original network for tissue engineering. However, their low mechanical performances limit their broad applicability in various functional tissues. This property causes substantial challenges in designing and preparing strong hydrogel networks. Therefore, we report the triple-networked hybrid hydrogel network with enhanced mechanical properties by incorporating dual-crosslinking and nanofillers (e.g., montmorillonite (MMT), graphene nanoplatelets (GNPs)). In this study, we prepared hybrid hydrogels composed of polyacrylamide, poly (vinyl alcohol), sodium alginate, MMT, and MMT/GNPs through dynamic crosslinking. The freeze-dried hybrid hydrogels showed good 3D porous architecture. The results exhibited a magnificent porous structure, interconnected pore-network surface morphology, enhanced mechanical properties, and cellular activity of hybrid hydrogels.

Using Copper-Doped Mesoporous Bioactive Glass Nanospheres to Impart Anti-Bacterial Properties to Dental Composites

Experimental dental resin composites containing copper-doped mesoporous bioactive glass nanospheres (Cu-MBGN) were developed to impart anti-bacterial properties. Increasing amounts of Cu-MBGN (0, 1, 5 and 10 wt%) were added to the BisGMA/TEGDMA resin matrix containing micro- and nano-fillers of inert glass, keeping the resin/filler ratio constant. Surface micromorphology and elemental analysis were performed to evaluate the homogeneous distribution of filler particles. The study investigated the effects of Cu-MBGN on the degree of conversion, polymerization shrinkage, porosity, ion release and anti-bacterial activity on S. mutans and A. naeslundii. Experimental materials containing Cu-MBGN showed a dose-dependent Cu release with an initial burst and a further increase after 28 days. The composite containing 10% Cu-MBGN had the best anti-bacterial effect on S. mutans, as evidenced by the lowest adherence of free-floating bacteria and biofilm formation. In contrast, the 45S5-containing materials had the highest S. mutans adherence. Ca release was highest in the bioactive control containing 15% 45S5, which correlated with the highest number of open porosities on the surface. Polymerization shrinkage was similar for all tested materials, ranging from 3.8 to 4.2%, while the degree of conversion was lower for Cu-MBGN materials. Cu-MBGN composites showed better anti-bacterial properties than composites with 45S5 BG.

Simultaneously stimulated osteogenesis and anti-bacteria of physically cross-linked double-network hydrogel loaded with MgO-Ag2O nanocomposites

Hydrogels, with a three-dimensional network of water-soluble polymer and water, could simulate the critical properties of extracellular matrix, which has been widely used in bone tissue engineering. However, most of conventional hydrogels for bone regeneration are fragile and have poor osteogenic activity, which restricts their applications. In this work, a novel nanoparticle-hydrogel composite consisting of physically cross-linked double-network loaded with MgO-Ag₂O nanocomposites was developed by the sol-gel method. The Mg²⁺ released from MgO-Ag₂O nanocomposites was used as an ionic cross-linking site of sodium alginate (SA), while the hydrophobic micelles in the polyacrylamide (PAAM) network is acted as another crosslinking point. The results indicated that the novel nanoparticle-hydrogel composites had good self-recovery ability and excellent mechanical properties compared with the conventional sodium alginate (SA)/polyacrylamide (PAAM) hydrogels. Additionally, it showed a slow release of Mg and Ag ions due to the dual function of the embedding effect of hydrogels and the increasing pH of the solution induced by the hydrolysis of sodium alginate. In terms of in vitro tests, the nanoparticle-hydrogel composites showed significantly stimulatory effects on the proliferation and differentiation of SaOS-2 cells. In addition, the antibacterial effects of the nanoparticle-hydrogel composites were gradually enhanced with the increase of MgO-Ag₂O content.

Bioactive inorganic particles-based biomaterials for skin tissue engineering

The challenge for treatment of severe cutaneous wound poses an urgent clinical need for the development of biomaterials to promote skin regeneration. In the past few decades, introduction of inorganic components into material system has become a promising strategy for improving performances of biomaterials in the process of tissue repair. In this review, we provide a current overview of the development of bioactive inorganic particles-based biomaterials used for skin tissue engineering. We highlight the three stages in the evolution of the bioactive inorganic biomaterials applied to wound management, including single inorganic materials, inorganic/organic composite materials, and inorganic particles-based cell-encapsulated living systems. At every stage, the primary types of bioactive inorganic biomaterials are described, followed by citation of the related representative studies completed in recent years. Then we offer a brief exposition of typical approaches to construct the composite material systems with incorporation of inorganic components for wound healing. Finally, the conclusions and future directions are suggested for the development of novel bioactive inorganic particles-based biomaterials in the field of skin regeneration.

In Vitro Models of Biological Barriers for Nanomedical Research

Nanoconstructs developed for biomedical purposes must overcome diverse biological barriers before reaching the target where playing their therapeutic or diagnostic function. In vivo models are very complex and unsuitable to distinguish the roles plaid by the multiple biological barriers on nanoparticle biodistribution and effect; in addition, they are costly, time-consuming and subject to strict ethical regulation. For these reasons, simplified in vitro models are preferred, at least for the earlier phases of the nanoconstruct development. Many in vitro models have therefore been set up. Each model has its own pros and cons: conventional 2D cell cultures are simple and cost-effective, but the information remains limited to single cells; cell monolayers allow the formation of cell–cell junctions and the assessment of nanoparticle translocation across structured barriers but they lack three-dimensionality; 3D cell culture systems are more appropriate to test in vitro nanoparticle biodistribution but they are static; finally, bioreactors and microfluidic devices can mimicking the physiological flow occurring in vivo thus providing in vitro biological barrier models suitable to reliably assess nanoparticles relocation. In this evolving context, the present review provides an overview of the most representative and performing in vitro models of biological barriers set up for nanomedical research.

Injectable Mesoporous Bioactive Nanoparticles Regenerate Bone Tissue under Osteoporosis Conditions

The osteogenic capability of mesoporous bioactive nanoparticles (MBNPs) in the SiO₂-CaO system has been assessed in vivo using an osteoporotic rabbit model. MBNPs have been prepared using a double template method, resulting in spherical nanoparticles with a porous core-shell structure that has a high surface area and the ability to incorporate the anti-osteoporotic drug ipriflavone. In vitro expression of the pro-inflammatory genes NF-κB1, IL-6, TNF-α, P38 and NOS2 in RAW-264.7 macrophages, indicates that these nanoparticles do not show adverse inflammatory effects. An injectable system has been prepared by suspending MBNPs in a hyaluronic acid-based hydrogel, which has been injected intraosseously into cavitary bone defects in osteoporotic rabbits. The histological analyses evidenced that MBNPs promote bone regeneration with a moderate inflammatory response. The incorporation of ipriflavone into these nanoparticles resulted in a higher presence of osteoblasts and enhanced angiogenesis at the defect site, but without showing significant differences in terms of new bone formation. STATEMENT OF SIGNIFICANCE: Mesoporous bioactive glass nanoparticles have emerged as one of the most interesting materials in the field of bone regeneration therapies. For the first time, injectable mesoporous bioactive nanoparticles have been tested in vivo using an osteoporotic animal model. Our findings evidence that MBG nanoparticles can be loaded with an antiosteoporotic drug, ipriflavone, and incorporated in hyaluronic acid to make up an injectable hydrogel. The incorporation of MBG nanoparticles promotes bone regeneration even under osteoporotic conditions, whereas the presence of IP enhances angiogenesis as well as the presence of osteoblast cells lining in the newly formed bone. The injectable device presented in this work opens new possibilities for the intraosseous treatment of osteoporotic bone using minimally invasive surgery.

Hybrid Nanosystems Based on Nicotinate-Functionalized Mesoporous Silica and Silver Chloride Nanoparticles Loaded with Phenytoin for Preventing Pseudomonas aeruginosa Biofilm Development

Pseudomonas aeruginosa (PA) is one of the most common bacteria isolated from chronic wounds and burns. Its treatment is a challenge due to antimicrobial drug resistance and biofilm formation. In this context, this study aimed to perform the synthesis and full characterization of hybrid nanosystems based on mesoporous silica nanoparticles (MSNs) functionalized with a nicotinic ligand and silver chloride nanoparticles, both phenytoin sodium (Ph)-loaded and unloaded, to evaluate the antibacterial properties against three different strains of PA (including two clinical strains) in a planktonic state and as biofilms. Ph is a well-known proliferative agent, which was incorporated into the hybrid nanomaterials to obtain an effective material for tissue healing and prevention of infection caused by PA. The Ph-loaded materials promoted a quasi-complete inhibition of bacterial growth in wound-like medium and biofilm development, with values of 99% and 96%, respectively, with selectivity indices above the requirements for drugs to become promising agents for the topic preventive treatment of chronic wounds and burns.

The interplay of collagen/bioactive glass nanoparticle coatings and electrical stimulation regimes distinctly enhanced osteogenic differentiation of human mesenchymal stem cells

Increasing research has incorporated bioactive glass nanoparticles (BGN) and electric field (EF) stimulation for bone tissue engineering and regeneration applications. However, their interplay and the effects of different EF stimulation regimes on osteogenic differentiation of human mesenchymal stem cells (hMSC) are less investigated. In this study, we introduced EF with negligible magnetic field strength through a well-characterized transformer-like coupling (TLC) system, and applied EF disrupted (4/4) or consecutive (12/12) regime on type I collagen (Col) coatings with/without BGN over 28 days. Additionally, dexamethasone was excluded to enable an accurate interpretation of BGN and EF in supporting osteogenic differentiation. Here, we demonstrated the influences of BGN and EF on collagen topography and maintaining coating stability. Coupled with the release profile of Si ions from the BGN, cell proliferation and calcium deposition were enhanced in the Col-BGN samples after 28 days. Further, osteogenic differentiation was initiated as early as d 7, and each EF regime was shown to activate distinct pathways. The disrupted (4/4) regime was associated with the BMP/Smad4 pathways that up-regulate Runx2/OCN gene expression on d 7, with a lesser effect on ALP activity. In contrast, the canonical Wnt/β-Catenin signaling pathway activated through mechanotransduction cues is associated with the consecutive (12/12) regime, with significantly elevated ALP activity and Sp7 gene expression reported on d 7. In summary, our results illustrated the synergistic effects of BGN and EF in different stimulation regimes on osteogenic differentiation that can be further exploited to enhance current bone tissue engineering and regeneration approaches. STATEMENT OF SIGNIFICANCE: The unique release mechanisms of silica from bioactive glass nanoparticles (BGN) were coupled with pulsatile electric field (EF) stimulation to support hMSC osteogenic differentiation, in the absence of dexamethasone. Furthermore, the interplay with consecutive (12/12) and disrupted (4/4) stimulation regimes was investigated. The reported physical, mechanical and topographical effects of BGN and EF on the collagen coating, hMSC and the distinct progression of osteogenic differentiation (canonical Wnt/β-Catenin and BMP/Smad) triggered by respective stimulation regime were not explicitly reported previously. These results provide the fundamentals for further exploitations on BGN composites with metal ions and rotation of EF regimes to enhance osteogenic differentiation. The goal is sustaining continual osteogenic differentiation and achieving a more physiologically-relevant state and bone constructs in vitro.

A 3D Printed Bone Tissue Engineering Scaffold Composed of Alginate Dialdehyde-Gelatine Reinforced by Lysozyme Loaded Cerium Doped Mesoporous Silica-Calcia Nanoparticles

A novel biomaterial comprising alginate dialdehyde-gelatine (ADA-GEL) hydrogel augmented by lysozyme loaded mesoporous cerium doped silica-calcia nanoparticles (Lys-Ce-MSNs) was 3D printed to create bioactive scaffolds. Lys-Ce-MSNs raised the mechanical stiffness of the hydrogel composite scaffold and induced surface apatite mineralization, when the scaffold was immersed in simulated body fluid (SBF). Moreover, the scaffolds could co-deliver bone healing (Ca and Si) and antioxidant ions (Ce), and Lys to achieve antibacterial (and potentially anticancer) properties. The nanocomposite hydrogel scaffolds could hold and deliver Lys steadily. Based on the in vitro results, the hydrogel nanocomposite containing Lys assured improved pre-osteoblast cell (MC3T3-E1) proliferation, adhesion, and differentiation, thanks to the biocompatibility of ADA-GEL, bioactivity of Ce-MSNs, and the stabilizing effect of Lys on the scaffold structure. On the other hand, the proliferation level of MG63 osteosarcoma cells decreased, likely due to the anticancer effect of Lys. Last but not least, cooperatively, alongside gentamicin (GEN), Lys brought about a proper antibacterial efficiency to the hydrogel nanocomposite scaffold against gram-positive and gram-negative bacteria. Taken together, ADA-GEL/Lys-Ce-MSN nanocomposite holds great promise for 3D printing of multifunctional hydrogel BTE scaffolds, able to induce bone regeneration, address infection, and potentially inhibit tumor formation and growth. This article is protected by copyright. All rights reserved.

Fabrication of ZnO@Plant Polyphenols/Cellulose as Active Food Packaging and Its Enhanced Antibacterial Activity

To investigate the efficient use of bioresources and bioproducts, plant polyphenol (PPL) was extracted from larch bark and further applied to prepare ZnO@PPL/Cel with cellulose to examine its potential as an active package material. The structure and morphology were fully characterized by XRD, SEM, FTIR, XPS and Raman spectra. It was found that PPL is able to cover ZnO and form a coating layer. In addition, PPL cross-links with cellulose and makes ZnO distribute evenly on the cellulose fibers. Coating with PPL creates a pinecone-like morphology in ZnO, which is constructed by subunits of 50 nm ZnO slices. The interactions among ZnO, PPL and cellulose have been attributed to hydrogen bonding, which plays an important role in guiding the formation of composites. The antibacterial properties against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were tested by the inhibition zone method. Our composite ZnO@PPL/Cel has superior antibacterial activity compared to ZnO/Cel. The antibacterial mechanism has also been elaborated on. The low cost, simple preparation method and good performance of ZnO@PPL/Cel suggest the potential for it to be applied as active food packaging.

Bioactive Properties of Composites Based on Silicate Glasses and Different Silver and Gold Structures

Using an ideal biomaterial to treat injured bones can accelerate the healing process and simultaneously exhibit antibacterial properties; thus protecting the patient from bacterial infections. Therefore, the aim of this work was to synthesize composites containing silicate-based bioactive glasses and different types of noble metal structures (i.e., AgI pyramids, AgIAu composites, Au nanocages, Au nanocages with added AgI). Bioactive glass was used as an osteoconductive bone substitute and Ag was used for its antibacterial character, while Au was included to accelerate the formation of new bone. To investigate the synergistic effects in these composites, two syntheses were carried out in two ways: AgIAu composites were added in either one step or AgI pyramids and Au nanocages were added separately. All composites showed good in vitro bioactivity. Transformation of AgI in bioactive glasses into Ag nanoparticles and other silver species resulted in good antibacterial behavior. It was observed that the Ag nanoparticles remained in the Au nanocages, which was also beneficial in terms of antibacterial properties. The presence of Au nanoparticles contributed to the composites achieving high cell viability. The most outstanding result was obtained by the consecutive addition of noble metals into the bioactive glasses, resulting in both a high antibacterial effect and good cell viability.

Antibacterial approaches in tissue engineering using metal ions and nanoparticles: From mechanisms to applications

Bacterial infection of implanted scaffolds may have fatal consequences and, in combination with the emergence of multidrug bacterial resistance, the development of advanced antibacterial biomaterials and constructs is of great interest. Since decades ago, metals and their ions had been used to minimize bacterial infection risk and, more recently, metal-based nanomaterials, with improved antimicrobial properties, have been advocated as a novel and tunable alternative. A comprehensive review is provided on how metal ions and ion nanoparticles have the potential to decrease or eliminate unwanted bacteria. Antibacterial mechanisms such as oxidative stress induction, ion release and disruption of biomolecules are currently well accepted. However, the exact antimicrobial mechanisms of the discussed metal compounds remain poorly understood. The combination of different metal ions and surface decorations of nanoparticles will lead to synergistic effects and improved microbial killing, and allow to mitigate potential side effects to the host. Starting with a general overview of antibacterial mechanisms, we subsequently focus on specific metal ions such as silver, zinc, copper, iron and gold, and outline their distinct modes of action. Finally, we discuss the use of these metal ions and nanoparticles in tissue engineering to prevent implant failure.

Bio-inspired hydrogel-based bandage with robust adhesive and antibacterial abilities for skin closure

Although conventional suturing techniques are commonly used in assisting wound closure, they do pose limited conduciveness and may lead to secondary injury to wound tissues. Inspired by marine organism mussels, we designed and manufactured a bio-inspired hydrogel-based bandage with tough wet tissue adhesion to substitute traditional surgical suture, accelerate wound healing and avoid infection. Poly(γ-glutamic acid) was modified with 3,4-dihydroxyphenylalanine and glycidyl methacylate, then introduced into the acrylic acid-co-acrylamide hydrogel matrix with robust mechanical properties. The hydrogel bandage showed strong chemical linkage adhesion (70 ± 2.1 kPa), which is 2.8 times that of commercial tissue adhesive fibrin glue (25 ± 2.2 kPa). The hydrogel bandage can not only maintain the self-stability, but is also capable of self-tuning adhesive strength in the range of 14-70 kPa to achieve different adhesion effects by tuning constituent ratio. The bandage has desirable compression properties (0.7 ± 0.11 MPa) and tensile elongation (about 25 times), which ensures its resistance to damages, especially in joint spaces. Secondly, the bandage was endowed with antioxidant and endogenous broad-spectrum antibacterial properties with its catechol structure. Results also demonstrated excellent cell compatibility and blood compatibility, certifying its eligible biological safety profile. In a rat full-thickness cutaneous deficiency model, we can clearly observe that the bandage possesses the ability to promote wound healing (only need 6 days). Above all, this research provides a new strategy for the emergency treatment of liver hemostasis and myocardial repair during disaster rescue.

SUPPLEMENTARY INFORMATION

Experimental details and supporting data are available in the online version of the paper10.1007/s40843-021-1724-8.

Mesoporous Silica Nanoparticles and Mesoporous Bioactive Glasses for Wound Management: From Skin Regeneration to Cancer Therapy

Exploring new therapies for managing skin wounds is under progress and, in this regard, mesoporous silica nanoparticles (MSNs) and mesoporous bioactive glasses (MBGs) offer great opportunities in treating acute, chronic, and malignant wounds. In general, therapeutic effectiveness of both MSNs and MBGs in different formulations (fine powder, fibers, composites etc.) has been proved over all the four stages of normal wound healing including hemostasis, inflammation, proliferation, and remodeling. The main merits of these porous substances can be summarized as their excellent biocompatibility and the ability of loading and delivering a wide range of both hydrophobic and hydrophilic bioactive molecules and chemicals. In addition, doping with inorganic elements (e.g., Cu, Ga, and Ta) into MSNs and MBGs structure is a feasible and practical approach to prepare customized materials for improved skin regeneration. Nowadays, MSNs and MBGs could be utilized in the concept of targeted therapy of skin malignancies (e.g., melanoma) by grafting of specific ligands. Since potential effects of various parameters including the chemical composition, particle size/morphology, textural properties, and surface chemistry should be comprehensively determined via cellular in vitro and in vivo assays, it seems still too early to draw a conclusion on ultimate efficacy of MSNs and MBGs in skin regeneration. In this regard, there are some concerns over the final fate of MSNs and MBGs in the wound site plus optimal dosages for achieving the best outcomes that deserve careful investigation in the future.

Fabrication and Characterization of Cinnamaldehyde-Loaded Mesoporous Bioactive Glass Nanoparticles/PHBV-Based Microspheres for Preventing Bacterial Infection and Promoting Bone Tissue Regeneration

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is considered a suitable polymer for drug delivery systems and bone tissue engineering due to its biocompatibility and biodegradability. However, the lack of bioactivity and antibacterial activity hinders its biomedical applications. In this study, mesoporous bioactive glass nanoparticles (MBGN) were incorporated into PHBV to enhance its bioactivity, while cinnamaldehyde (CIN) was loaded in MBGN to introduce antimicrobial activity. The blank (PHBV/MBGN) and the CIN-loaded microspheres (PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20) were fabricated by emulsion solvent extraction/evaporation method. The average particle size and zeta potential of all samples were investigated, as well as the morphology of all samples evaluated by scanning electron microscopy. PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20 significantly exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli in the first 3 h, while CIN releasing behavior was observed up to 7 d. Human osteosarcoma cell (MG-63) proliferation and attachment were noticed after 24 h cell culture, demonstrating no adverse effects due to the presence of microspheres. Additionally, the rapid formation of hydroxyapatite on the composite microspheres after immersion in simulated body fluid (SBF) during 7 d revealed the bioactivity of the composite microspheres. Our findings indicate that this system represents an alternative model for an antibacterial biomaterial for potential applications in bone tissue engineering.

Multifunctional Injectable Hydrogel Loaded with Cerium-Containing Bioactive Glass Nanoparticles for Diabetic Wound Healing

Diabetic foot wound healing is a major clinical problem due to impaired angiogenesis and bacterial infection. Therefore, an effective regenerative dressing is desiderated with the function of promoting revascularization and anti-bacteria. Herein, a multifunctional injectable composite hydrogel was prepared by incorporation of the cerium-containing bioactive glass (Ce-BG) into Gelatin methacryloyl (GelMA) hydrogel. The Ce-BG was synthesized by combining sol-gel method with template method, which maintained spherical shape, chemical structure and phase constitution of bioactive glass (BG). The Ce-BG/GelMA hydrogels had good cytocompatibility, promoted endothelial cells migration and tube formation by releasing Si ion. In vitro antibacterial tests showed that 5 mol % CeO2-containing bioactive glass/GelMA (5/G) composite hydrogel exhibited excellent antibacterial properties. In vivo study demonstrated that the 5/G hydrogel could significantly improve wound healing in diabetic rats by accelerating the formation of granulation tissue, collagen deposition and angiogenesis. All in all, these results indicate that the 5/G hydrogel could enhance diabetic wound healing. Therefore, the development of multifunctional materials with antibacterial and angiogenic functions is of great significance to promote the repair of diabetic wound healing.

Metallic Ions Encapsulated in Electrospun Nanofiber for Antibacterial and Angiogenesis Function to Promote Wound Repair

Electrospun nanofiber is an attractive biomaterial for skin tissue engineering because it mimics the natural fibrous extracellular matrix structure and creates a physical structure suitable for skin tissue regeneration. However, endowing the nanofibrous membranes with antibacterial and angiogenesis functions needs to be explored. In the current study, we aimed to fabricate gelatin/polycaprolactone (GT/PCL) (GT/PCL-Ag-Mg) nanofibers loaded with silver (Ag) and magnesium (Mg) ions for antibacterial activity and pro-angiogenesis function for wound repair. The fabricated GT/PCL membranes had a nanofibrous structure with random arrangement and achieved sustained release of Ag and Mg ions. In vitro results indicated that the GT/PCL-Ag-Mg membranes presented satisfactory cytocompatibility with cell survival and proliferation. In addition, the membranes with Ag demonstrated good antibacterial capacity to both gram-positive and gram-negative bacteria, and the Mg released from the membranes promoted the tube formation of vascular endothelial cells. Furthermore, in vivo results demonstrated that the GT/PCL-Ag-Mg membrane presented an accelerated wound healing process compared with GT/PCL membranes incorporated with either Ag or Mg ions and pure GT/PCL alone. Superior epidermis formation, vascularization, and collagen deposition were also observed in GT/PCL-Ag-Mg membrane compared with the other membranes. In conclusion, a multifunctional GT/PCL-Ag-Mg membrane was fabricated with anti-infection and pro-angiogenesis functions, serving as a potential metallic ion-based therapeutic platform for applications in wound repair.

Cerium and gallium containing mesoporous bioactive glass nanoparticles for bone regeneration: Bioactivity, biocompatibility and antibacterial activity

In recent years, mesoporous bioactive glass nanoparticles (MBGNPs) have generated great attention in biomedical applications. In this study, cerium and gallium doped MBGNPs were prepared by microemulsion assisted sol-gel method in the binary SiO₂-CaO system. MBGNPs with spheroidal and pineal shaped morphology were obtained. Nitrogen sorption analysis elucidated the mesoporous structure of synthesized nanoparticles with high specific surface area. X-ray diffraction analysis confirmed the amorphous nature of the nanoparticles. The chemical compositions of all samples were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), which revealed that the contents of cerium and gallium could be tailored by adjusting the concentrations of the precursors used for the synthesis. All MBGNPs exhibited in vitro bioactivity when immersed in simulated body fluid, except the particles doped with higher amounts than 1 mol% of cerium. MBGNPs showed antibacterial activity against S. aureus and E. coli without exhibiting cytotoxicity towards MG-63 osteoblast-like cells. Mentioned features of the obtained Ce and Ga-doped MBGNPs make them useful for multifunctional applications such as drug delivery carriers or bioactive fillers for bone tissue engineering applications.

Synthesis and characterization of Ag@AgCl-reinforced cellulose composites with enhanced antibacterial and photocatalytic degradation properties

In the present work, Ag@AgCl-reinforced cellulose composites with enhanced antibacterial and photocatalytic degradation properties were successfully synthesized via oil bath heating method. During the process, zinc chloride (ZnCl₂) solution was used as both Cl⁻ resource to form AgCl and the solvent to dissolve cellulose. The samples were synthesized with different temperatures, times, and concentrations of ZnCl₂ solution. The morphology, microstructure and phase of the as-prepared samples were analyzed with X-ray powder diffraction (XRD), fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), photocatalytic activity studies and inhibition zone experiments. Results showed that dye solution could be completely degraded by the materials in 1 h, and higher concentrations of ZnCl₂ solution favored for larger inhibition zones (higher to 10.8 mm). This synthetic strategy displayed here offers more possibilities to high value-added applications of cellulose.

Hydroxyapatite mineralization of chitosan-tragacanth blend/ZnO/Ag nanocomposite films with enhanced antibacterial activity

Biocompatible nanocomposites (NCs) with antibacterial activity containing organic matrix and inorganic nanoparticles (NPs) are vital for providing a suitable substrate for hydroxyapatite (HA) formation. Therefore, we fabricated a series of biocompatible NCs of chitosan (CS) and tragacanth gum (TG) and different percentages of ZnO NPs and ZnO@Ag NPs as fillers into the CS-TG blend. The characteristics of the NCs were distinguished with the field-emission scanning electron microscope (FE-SEM), X-Ray diffraction, Fourier transform infrared, and transmission electron microscopy (TEM). The CS-TG/ZnO@Ag(1:0.500) NC 8 wt% showed a rough surface according to FE-SEM. Moreover, the TEM image of CS-TG/ZnO NC 8 wt% depicted a uniform dispersion of NPs into the matrix. The biocompatibility of these NCs was evaluated by the formation of HA on their surfaces. The outcomes depicted the deposition of HA on the surface of all NCs. Also, CS-TG/ZnO@Ag(1:0.500) NC 8 wt% exhibited the most HA deposition on its surface. The antibacterial activity of these NCs toward Staphylococcus aureus and Escherichia coli bacteria was evaluated. The CS-TG/ZnO@Ag(1:0.500) NC 8 wt% exhibited a higher inhibition zone diameter in comparison to the ZnO@Ag (1:0.500) NPs for the S. aureus bacteria. Generally, antibacterial activity of the NCs containing ZnO@Ag NPs are more than NCs containing ZnO NPs.

Porous bioactive glass micro- and nanospheres with controlled morphology: developments, properties and emerging biomedical applications

In recent years, porous bioactive glass micro/nanospheres (PBGSs) have emerged as attractive biomaterials in various biomedical applications where such engineered particles provide suitable functions, from tissue engineering to drug delivery. The design and synthesis of PBGSs with controllable particle size and pore structure are critical for such applications. PBGSs have been successfully synthesized using melt-quenching and sol-gel based methods. The morphology of PBGSs is controllable by tuning the processing parameters and precursor characteristics during the synthesis. In this comprehensive review on PBGSs, we first overview the synthesis approaches for PBGSs, including both melt-quenching and sol-gel based strategies. Sol-gel processing is the primary technology used to produce PBGSs, allowing for control over the chemical compositions and pore structure of particles. Particularly, the influence of pore-forming templates on the morphology of PBGSs is highlighted. Recent progress in the sol-gel synthesis of PBGSs with sophisticated pore structures (e.g., hollow mesoporous, dendritic fibrous mesoporous) is also covered. The challenges regarding the control of particle morphology, including the influence of metal ion precursors and pore expansion, are discussed in detail. We also highlight the recent achievements of PBGSs in a number of biomedical applications, including bone tissue regeneration, wound healing, therapeutic agent delivery, bioimaging, and cancer therapy. Finally, we conclude with our perspectives on the directions of future research based on identified challenges and potential new developments and applications of PBGSs.

Ipriflavone-Loaded Mesoporous Nanospheres with Potential Applications for Periodontal Treatment

The incorporation and effects of hollow mesoporous nanospheres in the system SiO₂-CaO (nanoMBGs) containing ipriflavone (IP), a synthetic isoflavone that prevents osteoporosis, were evaluated. Due to their superior porosity and capability to host drugs, these nanoparticles are designed as a potential alternative to conventional bioactive glasses for the treatment of periodontal defects. To identify the endocytic mechanisms by which these nanospheres are incorporated within the MC3T3-E1 cells, five inhibitors (cytochalasin B, cytochalasin D, chlorpromazine, genistein and wortmannin) were used before the addition of these nanoparticles labeled with fluorescein isothiocyanate (FITC-nanoMBGs). The results indicate that nanoMBGs enter the pre-osteoblasts mainly through clathrin-dependent mechanisms and in a lower proportion by macropinocytosis. The present study evidences the active incorporation of nanoMBG-IPs by MC3T3-E1 osteoprogenitor cells that stimulate their differentiation into mature osteoblast phenotype with increased alkaline phosphatase activity. The final aim of this study is to demonstrate the biocompatibility and osteogenic behavior of IP-loaded bioactive nanoparticles to be used for periodontal augmentation purposes and to shed light on internalization mechanisms that determine the incorporation of these nanoparticles into the cells.

Best served small: nano battles in the war against wound biofilm infections

The global challenge of antimicrobial resistance is of increasing concern, and alternatives to currently used antibiotics or methods to improve their stewardship are sought worldwide. Microbial biofilms, complex 3D communities of bacteria and/or fungi, are difficult to treat with antibiotics for several reasons. These include their protective coats of extracellular matrix proteins which are difficult for antibiotics to penetrate. Nanoparticles (NP) are one way to rise to this challenge; whilst they exist in many forms naturally there has been a profusion in synthesis of these small (<100 nm) particles for biomedical applications. Their small size allows them to penetrate the biofilm matrix, and as well as some NP being inherently antimicrobial, they also can be modified by doping with antimicrobial payloads or coated to increase their effectiveness. This mini-review examines the current role of NP in treating wound biofilms and the rise in multifunctionality of NP.

A new strategy for synthesizing silver doped mesoporous bioactive glass fibers and their bioactivity, antibacterial activity and drug loading performance

A new strategy for preparing mesoporous metal-doped bioactive glass fibers (MBGFs) was designed, which included electrospinning and sulfonating mesoporous PS fibers, precipitating metal ions and bioactive glass sol-gel precursor into the mesoporous polystyrene (PS) fibers and calcinations. Silver-doped mesoporous BGFs (Ag-MBGFs) with a uniform diameter of 1-2 μm and a specific surface area of 40.22 m² g^-1 were prepared as an example and characterized by SEM, XRD, TG, ICP and FTIR. These Ag-MBGFs showed excellent bioactivity, antibacterial properties and drug loading and release performance due to their special mesoporous and fibrous structure. The concentration of Staphylococcus aureus decreased from 1 × 10⁸ colony-forming units per mL (CFU mL^-1) to 2.5 × 10⁶ CFU mL^-1 in 2 h and then to 2 × 10² CFU mL^-1 in 12 h when the concentration of the Ag-MBGFs reached 16 mg mL^-1. BGFs of different compositions and functions could be prepared by the same strategy in a mesoporous PS fiber template, which could enrich materials for constructing orthopedic implants.

Comprehensive Survey on Nanobiomaterials for Bone Tissue Engineering Applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering.

"Hard" ceramics for "Soft" tissue engineering: Paradox or opportunity?

Tissue engineering provides great possibilities to manage tissue damages and injuries in modern medicine. The involvement of hard biocompatible materials in tissue engineering-based therapies for the healing of soft tissue defects has impressively increased over the last few years: in this regard, different types of bioceramics were developed, examined and applied either alone or in combination with polymers to produce composites. Bioactive glasses, carbon nanostructures, and hydroxyapatite nanoparticles are among the most widely-proposed hard materials for treating a broad range of soft tissue damages, from acute and chronic skin wounds to complex injuries of nervous and cardiopulmonary systems. Although being originally developed for use in contact with bone, these substances were also shown to offer excellent key features for repair and regeneration of wounds and "delicate" structures of the body, including improved cell proliferation and differentiation, enhanced angiogenesis, and antibacterial/anti-inflammatory activities. Furthermore, when embedded in a soft matrix, these hard materials can improve the mechanical properties of the implant. They could be applied in various forms and formulations such as fine powders, granules, and micro- or nanofibers. There are some pre-clinical trials in which bioceramics are being utilized for skin wounds; however, some crucial questions should still be addressed before the extensive and safe use of bioceramics in soft tissue healing. For example, defining optimal formulations, dosages, and administration routes remain to be fixed and summarized as standard guidelines in the clinic. This review paper aims at providing a comprehensive picture of the use and potential of bioceramics in treatment, reconstruction, and preservation of soft tissues (skin, cardiovascular and pulmonary systems, peripheral nervous system, gastrointestinal tract, skeletal muscles, and ophthalmic tissues) and critically discusses their pros and cons (e.g., the risk of calcification and ectopic bone formation as well as the local and systemic toxicity) in this regard. STATEMENT OF SIGNIFICANCE: Soft tissues form a big part of the human body and play vital roles in maintaining both structure and function of various organs; however, optimal repair and regeneration of injured soft tissues (e.g., skin, peripheral nerve) still remain a grand challenge in biomedicine. Although polymers were extensively applied to restore the lost or injured soft tissues, the use of bioceramics has the potential to provides new opportunities which are still partially unexplored or at the very beginning. This reviews summarizes the state of the art of bioceramics in this field, highlighting the latest evolutions and the new horizons that can be opened by their use in the context of soft tissue engineering. Existing results and future challenges are discussed in order to provide an up-to-date contribution that is useful to both experienced scientists and early-stage researchers of the biomaterials community.

Metal-based nanoparticles for bone tissue engineering

Tissue is vital to the organization of multicellular organisms, because it creates the different organs and provides the main scaffold for body shape. The quest for effective methods to allow tissue regeneration and create scaffolds for new tissue growth has intensified in recent years. Tissue engineering has recently used some promising alternatives to existing conventional scaffold materials, many of which have been derived from nanotechnology. One important example of these is metal nanoparticles. The purpose of this review is to cover novel tissue engineering methods, paying special attention to those based on the use of metal-based nanoparticles. The unique physiochemical properties of metal nanoparticles, such as antibacterial effects, shape memory phenomenon, low cytotoxicity, stimulation of the proliferation process, good mechanical and tensile strength, acceptable biocompatibility, significant osteogenic potential, and ability to regulate cell growth pathways, suggest that they can perform as novel types of scaffolds for bone tissue engineering. The basic principles of various nanoparticle-based composites and scaffolds are discussed in this review. The merits and demerits of these particles are critically discussed, and their importance in bone tissue engineering is highlighted.

Development of novel microenvironments for promoting enhanced wound healing

PURPOSE OF REVIEW

Nonhealing wounds are a significant issue facing the healthcare industry. Materials that modulate the wound microenvironment have the potential to improve healing outcomes.

RECENT FINDINGS

A variety of acellular and cellular scaffolds have been developed for regulating the wound microenvironment, including materials for controlled release of antimicrobials and growth factors, materials with inherent immunomodulative properties, and novel colloidal-based scaffolds. Scaffold construction methods include electrospinning, 3D printing, decellularization of extracellular matrix, or a combination of techniques. Material application methods include layering or injecting at the wound site.

SUMMARY

Though these techniques show promise for repairing wounds, all material strategies thus far struggle to induce regeneration of features such as sweat glands and hair follicles. Nonetheless, innovative technologies currently in the research phase may facilitate future attainment of these features. Novel methods and materials are constantly arising for the development of microenvironments for enhanced wound healing.

Effects of Gelatin Methacrylate Bio-ink Concentration on Mechano-Physical Properties and Human Dermal Fibroblast Behavior

Gelatin-methacryloyl (GelMa) is a very versatile biomaterial widely used in various biomedical applications. The addition of methacryloyl makes it possible to have hydrogels with varying mechanical properties due to its photocuring characteristics. In addition, gelatin is obtained and derived from natural material; thus, it retains various cell-friendly motifs, such as arginine-glycine-aspartic acid, which then provides implanted cells with a friendly environment for proliferation and differentiation. In this study, we fabricated human dermal fibroblast cell (hDF)-laden photocurable GelMa hydrogels with varying physical properties (5%, 10%, and 15%) and assessed them for cellular responses and behavior, including cell spreading, proliferation, and the degree of extracellular matrix remodeling. Under similar photocuring conditions, lower concentrations of GelMa hydrogels had lower mechanical properties than higher concentrations. Furthermore, other properties, such as swelling and degradation, were compared in this study. In addition, our findings revealed that there were increased remodeling and proliferation markers in the 5% GelMa group, which had lower mechanical properties. However, it was important to note that cellular viabilities were not affected by the stiffness of the hydrogels. With this result in mind, we attempted to fabricate 5-15% GelMa scaffolds (20 × 20 × 3 mm3) to assess their feasibility for use in skin regeneration applications. The results showed that both 10% and 15% GelMa scaffolds could be fabricated easily at room temperature by adjusting several parameters, such as printing speed and extrusion pressure. However, since the sol-gel temperature of 5% GelMa was noted to be lower than its counterparts, 5% GelMa scaffolds had to be printed at low temperatures. In conclusion, GelMa once again was shown to be an ideal biomaterial for various tissue engineering applications due to its versatile mechanical and biological properties. This study showed the feasibility of GelMa in skin tissue engineering and its potential as an alternative for skin transplants.

Using MgO nanoparticles as a potential platform to precisely load and steadily release Ag ions for enhanced osteogenesis and bacterial killing

Bio-functional fillers including bio-ceramic, degradable metallic and composite particles are commonly introduced into bone tissue engineering (BTE) scaffolds to endow the materials with specific biological functions for enhanced bone defect therapy. In this work, MgO nanoparticles (NPs) were employed as a potential platform for precise loading and sustained release of Ag⁺. The results showed that MgO NPs possessed strong adsorption capacity (almost 100%) towards Ag⁺ in AgNO₃ solutions with different concentrations (0.1, 1 and 10 mM). After the adsorption of Ag⁺ in AgNO₃ solutions, cube-shaped MgO NPs transformed to lamella-structured nano-composites (NCs) composed of Mg(OH)₂ and Ag₂O, which were referred as MgO-xAg (x = 0.1, 1 or 10) NCs depending on the employed concentration of AgNO₃ solution. After being suspended in distilled water, as-prepared positively charged NCs underwent a fast degradation process during the initial 4 days. From day 4 and 14, steady release behaviors of Mg²⁺ and/or Ag⁺ from the NCs were noticed. With the lowest loading amount of Ag⁺, MgO-0.1Ag NCs did not exhibit significant modulatory effect on SaOS-2 cell response. On the contrary, MgO-10Ag NCs loaded with the highest amount of Ag⁺ showed significant cyto-toxicity towards SaOS-2 cells. With appropriate amount of Ag⁺ loading, MgO-1Ag NCs showed significantly stimulatory effects on SaOS-2 cell proliferation and differentiation. This is evidenced by the enhanced cell viability, alkaline phosphatase (ALP) activity and collagen (COL) production as well as the gene expressions of ALP, COL and osteoprotegerin (OPG) in MgO-1Ag group. Moreover, MgO-1Ag exhibited strong bactericidal capacity against both Escherichia coli and Staphylococcus aureus. Together, the results indicate that MgO could be employed as a potential platform for precise loading and sustained release of Ag⁺. MgO-1Ag NCs are promising to be used as bio-functional fillers in BTE scaffolds for simultaneously promoted osteogenesis and bacterial killing.

Electrospun Scaffolds Containing Silver-Doped Hydroxyapatite with Antimicrobial Properties for Applications in Orthopedic and Dental Bone Surgery

Preventing the development of osteomyelitis while enhancing bone regeneration is challenging, with relatively little progress to date in translating promising technologies to the clinic. Nanoscale hydroxyapatite (nHA) has been employed as a bone graft substitute, and recent work has shown that it may be modified with silver to introduce antimicrobial activity against known pathogens. The aim of this study was to incorporate silver-doped nHA into electrospun scaffolds for applications in bone repair. Silver-doped nHA was produced using a modified, rapid mixing, wet precipitation method at 2, 5, 10 mol.% silver. The silver-doped nHA was added at 20 wt.% to a polycaprolactone solution for electrospinning. Bacteria studies demonstrated reduced bacterial presence, with Escherichia coli and Staphylococcus aureus undetectable after 96 h of exposure. Mesenchymal stem cells (MSCs) were used to study both toxicity and osteogenicity of the scaffolds using PrestoBlue^® and alkaline phosphatase (ALP) assays. Innovative silver nHA scaffolds significantly reduced E. coli and S. aureus bacterial populations while maintaining cytocompatibility with mammalian cells and enhancing the differentiation of MSCs into osteoblasts. It was concluded that silver-doped nHA containing scaffolds have the potential to act as an antimicrobial device while supporting bone tissue healing for applications in orthopedic and dental bone surgery.

An in vitro Reconstructed Human Skin Equivalent Model to Study the Role of Skin Integration Around Percutaneous Devices Against Bacterial Infection

Percutaneous devices are a key technology in clinical practice, used to connect internal organs to external medical devices. Examples include prosthesis, catheters and electrical drivelines. Percutaneous devices breach the skin's natural barrier and create an entry point for pathogens, making device infections a widespread problem. Modification of the percutaneous implant surface to increase skin integration with the aim to reduce subsequent infection is attracting a great deal of attention. While novel surfaces have been tested in various in vitro models used to study skin integration around percutaneous devices, no skin model has been reported, for the study of bacterial infection around percutaneous devices. Here, we report the establishment of an in vitro human skin equivalent model for driveline infections caused by Staphylococcus aureus, the most common cause of driveline-related infections. Three types of mock drivelines manufactured using melt electrowriting (smooth or porous un-seeded and porous pre-seeded with human fibroblasts) were implanted in human skin constructs and challenged with S. aureus. Our results show a high and stable load of S. aureus in association with the skin surface and no signs of S. aureus-induced tissue damage. Furthermore, our results demonstrate that bacterial migration along the driveline surface occurs in micro-gaps caused by insufficient skin integration between the driveline and the surrounding skin consistent with clinical reports from explanted patient drivelines. Thus, the human skin-driveline infection model presented here provides a clinically-relevant and versatile experimental platform for testing novel device surfaces and infection therapeutics.