Optimized Bioactive Glass: the Quest for the Bony Graft

Therapeutic Potential of Nano-Sustained-Release Factors for Bone Scaffolds

Research on nano-sustained-release factors for bone tissue scaffolds has significantly promoted the precision and efficiency of bone-defect repair by integrating biomaterials science, nanotechnology, and regenerative medicine. Current research focuses on developing multifunctional scaffold materials and intelligent controlled-release systems to optimize the spatiotemporal release characteristics of growth factors, drugs, and genes. Nano slow-release bone scaffolds integrate nano slow-release factors, which are loaded with growth factors, drugs, genes, etc., with bone scaffolds, which can significantly improve the efficiency of bone repair. In addition, these drug-loading systems have also been extended to the fields of anti-infection and anti-tumor. However, the problem of heterotopic ossification caused by high doses has led to a shift in research towards a low-dose multi-factor synergistic strategy. Multiple Phase II clinical trials are currently ongoing, evaluating the efficacy and safety of nano-hydroxyapatite scaffolds. Despite significant progress, this field still faces a series of challenges: the immunity risks of the long-term retention of nanomaterials, the precise matching of multi-factor release kinetics, and the limitations of the large-scale production of personalized scaffolds. Future development directions in this area include the development of responsive sustained-release systems, biomimetic sequential release design, the more precise regeneration of injury sites through a combination of gene-editing technology and self-assembled nanomaterials, and precise drug loading and sustained release through microfluidic and bioprinting technologies to reduce the manufacturing cost of bone scaffolds. The progress of these bone scaffolds has gradually changed bone repair from morphology-matched filling regeneration to functional recovery, making the clinical transformation of bone scaffolds safer and more universal.

Functional poly(ether-ketone-ketone) composite scaffold with enhanced cell-material interaction, anti-inflammatory and osteogenesis for facilitating osteointegration and bone regeneration

Bone defects resulting from trauma or disease remain a significant challenge in clinical practice, often requiring prolonged treatment. Poly(ether-ketone-ketone) (PEKK) is a commonly used implant material due to its excellent biocompatibility and mechanical properties, which are similar to those of bone. However, its biological inertness leads to poor anti-inflammatory and osteointegration properties, significantly hindering the bone repair process. In this study, a cryogel filled - PEKK/bioglass (BG) composite scaffold (SPBC) was prepared via 3D printing to provide immunomodulatory and bone integration performance. Compared with untreated PEKK, SPBC exhibited significant enhancements in surface properties, including higher hydrophilicity and roughness. Additionally, SPBC enhanced the adsorption of fibronectin and vitronectin on the scaffold surface and regulated the maturation of cytoskeleton and adhesion plaques by increasing the phosphorylation level of FAK at Y397, thereby promoting cell adhesion and spreading. Due to the release of bioactive ions, SPBC can significantly promote the polarization of RAW264.7 cells towards M2 and the secretion of anti-inflammatory cytokines, while also enhancing the proliferation and differentiation of rat mesenchymal stem cells (rMSCs) in vitro. Furthermore, the in vivo results confirmed the enhanced anti-inflammatory properties and the integration of SPBC with the host tissue. In summary, after surface modification and cryogel filling, SPBC demonstrated excellent anti-inflammatory and bone integration abilities, presenting potential for clinical application as an orthopedic implant scaffold.

Enhancing Bone Regeneration and Osteogenic Quality by n-HA Internalized Osteoblasts Synergized with ON Protein: Mechanistic Insights

Bone scaffolds offer hope for oral jawbone repair, yet improving their osteogenic performance remains a clinical challenge. This study investigates a novel approach to enhance early bone formation and osteogenic quality by coloading hydroxyapatite (HA)─internalized osteoblasts (OHA) and osteonectin (ON) onto various scaffolds. Our findings demonstrated that the OHA could effectively facilitate the early bone regeneration by providing rapid calcium and phosphorus ion release via lysosome-mediated HA degradation, while the ON protein helps in ion deposition, cell proliferation, and matrix mineralization. When the PHA (PCL+HA) scaffold was incorporated with both the OHA and ON, the scaffold exhibited superior pro-osteogenic performance, driven by synergistic effects of rapid ion release from the OHA, slow ion release from the PHA, and upregulation of osteogenesis-related genes. The analyses of mechanisms revealed that the OHA activated MAPK and PI3K-Akt pathways, while ON stimulated calcium and Wnt signaling, collectively promoting the osteogenic potential. The strategy presented in this study paves a promising way for the development of advanced bone scaffolds to improve the bone regeneration quality.

Design and Improvement of Bone Adhesive in response to Clinical Needs

Fracture represents one of the most common diagnoses in contemporary medical practice, with the majority of cases traditionally addressed through metallic device fixation. However, this approach is marred by several drawbacks, including prolonged operative durations, considerable expenses, suboptimal applicability to comminuted fractures, increased infection risks, and the inevitable requirement for secondary surgery. The inherent advantages of bone adhesives in these fields have garnered the attention of orthopedic surgeons, who have commenced utilizing biocompatible and biodegradable bone adhesives to bond and stabilize bone fragments. Regrettably, the current bone adhesives generally exhibit insufficient adhesive strength in vivo environments, and it is desirable for them to possess effective osteogenesis to facilitate fracture healing. Consequently, aligning bone adhesives with practical clinical demands remains a significant hurdle, which has catalyzed a surge in research endeavors. Within this review, the conceptual framework, characteristics, and design ideas of bone adhesives based on clinical needs are delineated. Recent advancements in this domain, specifically focusing on the enhancement of two pivotal characteristics-adhesive strength and osteogenic potential are also reviewed. Finally, a prospective analysis of the future advancements in bone adhesives, offering new insights into solutions for diverse clinical problems is presented.

Application of advanced surface modification techniques in titanium-based implants: latest strategies for enhanced antibacterial properties and osseointegration

Titanium-based implants, renowned for their excellent mechanical properties, corrosion resistance, and biocompatibility, have found widespread application as premier implant materials in the medical field. However, as bioinert materials, they often face challenges such as implant failure caused by bacterial infections and inadequate osseointegration post-implantation. Thus, to address these issues, researchers have developed various surface modification techniques to enhance the surface properties and bioactivity of titanium-based implants. This review aims to outline several key surface modification methods for titanium-based implants, including acid etching, sol-gel method, chemical vapor deposition, electrochemical techniques, layer-by-layer self-assembly, and chemical grafting. It briefly summarizes the advantages, limitations, and potential applications of these technologies, presenting readers with a comprehensive perspective on the latest advances and trends in the surface modification of titanium-based implants.

Cell-free chitosan/silk fibroin/bioactive glass scaffolds with radial pore for in situ inductive regeneration of critical-size bone defects

Tissue-engineered is an effective method for repairing critical-size bone defects. The application of bioactive scaffold provides artificial matrix and suitable microenvironment for cell recruitment and extracellular matrix deposition, which can effectively accelerate the process of tissue regeneration. Among various scaffold properties, appropriate pore structure and distribution have been proven to play a crucial role in inducing cell infiltration differentiation and in-situ tissue regeneration. In this study, a chitosan (CS) /silk fibroin (SF) /bioactive glass (BG) composite scaffold with distinctive radially oriented pore structure was constructed. The composite scaffolds had stable physical and chemical properties, a unique pore structure of radial arrangement from the center to the periphery and excellent mechanical properties. In vitro biological studies indicated that the CS/SF/BG scaffold could promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and the expression of related genes due to the wide range of connected pore structures and released active elements. Furthermore, in vivo study showed CS/SF/BG scaffold with radial pores was more conducive to the repair of skull defects in rats with accelerated healing speed during the bone tissue remodeling process. These results demonstrated the developed CS/SF/BG scaffold would be a promising therapeutic strategy for the repair of bone defects regeneration.

Synthesis of pure and doped nano-calcium phosphates using different conventional methods for biomedical applications: a review

The applications of calcium phosphates (hydroxyapatite, tetracalcium phosphate, tricalcium phosphate (alpha and beta), fluorapatite, di-calcium phosphate anhydrous, and amorphous calcium-phosphate) are increasing day by day. Calcium hydroxyapatite, commonly known as hydroxyapatite (HAp), represents a mineral form of calcium apatite. Owing to its close molecular resemblance to the mineral constituents of bones, teeth, and hard tissues, HAp is often employed in the biomedical domain. In addition, it is extensively employed in various sectors such as the remediation of water, air, and soil pollution. The key advantage of HAp lies in its potential to accommodate a wide variety of anionic and cationic substitutions. Nevertheless, HAp and tricalcium phosphate (TCP) syntheses typically involve the use of chemical precursors containing calcium and phosphorus sources and employ diverse techniques, such as solid-state, wet, and thermal methods or a combination of these processes. Researchers are increasingly favoring natural sources such as bio-waste (eggshells, oyster shells, animal bones, fish scales, etc.) as viable options for synthesizing HAp. Interestingly, the synthesis route significantly influences the morphology, size, and crystalline phase of calcium phosphates. In this review paper, we highlight both dry and wet methods, which include six commonly used synthesis methods (i.e. solid-state, mechano-chemical, wet-chemical precipitation, hydrolysis, sol-gel, and hydrothermal methods) coupled with the variation in source materials and their influence in modifying the structural morphology from a bulky state to nanoscale to explore the applications of multifunctional calcium phosphates in different formats.

Construction of antibacterial bone implants and their application in bone regeneration

Bacterial infection represents a prevalent challenge during the bone repair process, often resulting in implant failure. However, the extensive use of antibiotics has limited local antibacterial effects at the infection site and is prone to side effects. In order to address the issue of bacterial infection during the transplantation of bone implants, four types of bone scaffold implants with long-term antimicrobial functionality have been constructed, including direct contact antimicrobial scaffold, dissolution-penetration antimicrobial scaffold, photocatalytic antimicrobial scaffold, and multimodal synergistic antimicrobial scaffold. The direct contact antimicrobial scaffold involves the physical penetration or disruption of bacterial cell membranes by the scaffold surface or hindrance of bacterial adhesion through surface charge, microstructure, and other factors. The dissolution-penetration antimicrobial scaffold releases antimicrobial substances from the scaffold's interior through degradation and other means to achieve local antimicrobial effects. The photocatalytic antimicrobial scaffold utilizes the absorption of light to generate reactive oxygen species (ROS) with enhanced chemical reactivity for antimicrobial activity. ROS can cause damage to bacterial cell membranes, deoxyribonucleic acid (DNA), proteins, and other components. The multimodal synergistic antimicrobial scaffold involves the combined use of multiple antimicrobial methods to achieve synergistic effects and effectively overcome the limitations of individual antimicrobial approaches. Additionally, the biocompatibility issues of the antimicrobial bone scaffold are also discussed, including in vitro cell adhesion, proliferation, and osteogenic differentiation, as well as in vivo bone repair and vascularization. Finally, the challenges and prospects of antimicrobial bone implants are summarized. The development of antimicrobial bone implants can provide effective solutions to bacterial infection issues in bone defect repair in the foreseeable future.

Critical-size defects reconstruction with four different bone grafts associated with e-PTFE membrane: A histomorphometric experimental in vivo study

OBJECTIVES

The goal of this study was to assess the newly formed bone and the remnant biomaterial by comparing four different bone grafts used to treat critical-size defects, associated or not with the non-resorbable membrane.

MATERIALS AND METHODS

Two calvaria critical-size bone defects were created in 50 male Wistar rats. They were divided into blood (G1), autogenous (G2), bioglass (G3), hydroxyapatite (G4), and xenograft (G5) groups, associated or not with e-PTFE. The experimental periods were 15 and 45 days. Sections were prepared for histomorphometric assessment. All data were analyzed by the mixed-effects model with multiple comparisons (significance level, p < .05).

RESULTS

A similar level of new bone was observed for all groups, associated with a high level of vascularization. G1 and G2 ensured sovereignty over the greater quantity of new bone. A non-significant result was reported comparing groups with and without membranes. No significant result was found between the experimental synthetic biomaterials (G3 and G4). G5L achieved 22.0% of new bone after 45 days (p > .05). All groups had a stable volume of biomaterial kept in the short term (p > .05). G2 was the best material for new bone formation and final volume of biomaterial, followed by G4 < G5 < G3. Thus, it is possible that G4 had a better degradation profile among the experimental groups.

CONCLUSIONS

The best results were found in the autogenous group, with higher resorption and integration; non-significative new bone was found among the experimental groups; and the regeneration of critical bone defects using an e-PTFE barrier did not present significant results on new bone formation.

Flexible Fabrication and Hybridization of Bioactive Hydrogels with Robust Osteogenic Potency

Osteogenic scaffolds reproducing the natural bone composition, structures, and properties have represented the possible frontier of artificially orthopedic implants with the great potential to revolutionize surgical strategies against the bone-related diseases. However, it is difficult to achieve an all-in-one formula with the simultaneous requirement of favorable biocompatibility, flexible adhesion, high mechanical strength, and osteogenic effects. Here in this work, an osteogenic hydrogel scaffold fabricated by inorganic-in-organic integration between amine-modified bioactive glass (ABG) nanoparticles and poly(ethylene glycol) succinimidyl glutarate-polyethyleneimine (TSG-PEI) network was introduced as an all-in-one tool to flexibly adhere onto the defective tissue and subsequently accelerate the bone formation. Since the N-hydroxysuccinimide (NHS)-ester of tetra-PEG-SG polymer could quickly react with the NH2-abundant polyethyleneimine (PEI) polymer and ABG moieties, the TSG-PEI@ABG hydrogel was rapidly formed with tailorable structures and properties. Relying on the dense integration between the TSG-PEI network and ABG moieties on a nano-scale level, this hydrogel expressed powerful adhesion to tissue as well as durable stability for the engineered scaffolds. Therefore, its self-endowed biocompatibility, high adhesive strength, compressive modulus, and osteogenic potency enabled the prominent capacities on modulation of bone marrow mesenchymal stem cell (BMSCs) proliferation and differentiation, which may propose a potential strategy on the simultaneous scaffold fixation and bone regeneration promotion for the tissue engineering fields.

Polyvinylpyrrolidone Nanofibers Incorporating Mesoporous Bioactive Glass for Bone Tissue Engineering

Composite biomaterials that combine osteoconductive and osteoinductive properties are a promising approach for bone tissue engineering (BTE) since they stimulate osteogenesis while mimicking extracellular matrix (ECM) morphology. In this context, the aim of the present research was to produce polyvinylpyrrolidone (PVP) nanofibers containing mesoporous bioactive glass (MBG) 80S15 nanoparticles. These composite materials were produced by the electrospinning technique. Design of experiments (DOE) was used to estimate the optimal electrospinning parameters to reduce average fiber diameter. The polymeric matrices were thermally crosslinked under different conditions, and the fibers' morphology was studied using scanning electron microscopy (SEM). Evaluation of the mechanical properties of nanofibrous mats revealed a dependence on thermal crosslinking parameters and on the presence of MBG 80S15 particles inside the polymeric fibers. Degradation tests indicated that the presence of MBG led to a faster degradation of nanofibrous mats and to a higher swelling capacity. The assessment of in vitro bioactivity in simulated body fluid (SBF) was performed using MBG pellets and PVP/MBG (1:1) composites to assess if the bioactive properties of MBG 80S15 were kept when it was incorporated into PVP nanofibers. FTIR and XRD analysis along with SEM-EDS results indicated that a hydroxy-carbonate apatite (HCA) layer formed on the surface of MBG pellets and nanofibrous webs after soaking in SBF over different time periods. In general, the materials revealed no cytotoxic effects on the Saos-2 cell line. The overall results for the materials produced show the potential of the composites to be used in BTE.

Hydroxyapatite microbeads containing BMP-2 and quercetin fabricated via electrostatic spraying to encourage bone regeneration

BACKGROUND

Hydroxyapatite (HAp) possesses osteoconductive properties, and its granular form can serve as an effective drug delivery vehicle for bone regeneration. Quercetin (Qct), a plant-derived bioflavonoid, is known to promote bone regeneration; however, its comparative and synergistic effects with the commonly used bone morphogenetic protein-2 (BMP-2) have not been investigated.

METHODS

We examined the characteristics of newly formed HAp microbeads using an electrostatic spraying method and analyzed the in vitro release pattern and osteogenic potential of ceramic granules containing Qct, BMP-2, and both. In addition, HAp microbeads were transplanted into a rat critical-sized calvarial defect and the osteogenic capacity was assessed in vivo.

RESULTS

The manufactured beads had a microscale size of less than 200 μm, a narrow size distribution, and a rough surface. The alkaline phosphatase (ALP) activity of osteoblast-like cells cultured with the BMP-2-and-Qct-loaded HAp was significantly higher than that of either Qct- or BMP-2-loaded HAp groups. The mRNA levels of osteogenic marker genes such as ALP and runt-related transcription factor 2 were found to be upregulated in the HAp/BMP-2/Qct group compared to the other groups. In micro-computed tomographic analysis, the amount of newly formed bone and bone surface area within the defect was significantly higher in the HAp/BMP-2/Qct group, followed by the HAp/BMP-2 and HAp/Qct groups, which is consistent with the histomorphometrical results.

CONCLUSIONS

These results imply that electrostatic spraying can be an efficient strategy to produce homogenous ceramic granules and that the BMP-2-and-Qct-loaded HAp microbeads can serve as effective implants for bone defect healing.

Preparation and evaluation of stingray skin collagen/oyster osteoinductive composite scaffolds

The regeneration of bone defects is a major challenge for clinical orthopaedics. Herein, we designed and prepared a new type of bioactive material, using stingray skin collagen and oyster shell powder (OSP) as raw materials. A stingray skin collagen/oyster osteoinductive composite scaffold (Col-OSP) was prepared for the first time by genipin cross-linking, pore-forming and freeze-drying methods. These scaffolds were characterized by ATR-FTIR, SEM, compression, swelling, cell proliferation, cell adhesion, alkaline phosphatase activity, alizarin red staining and RT-PCR etc. The Col-OSP scaffold had an interconnected three-dimensional porous structure, and the mechanical properties of the Col-OSP composite scaffold were enhanced compared with Col, combining with the appropriate swelling rate and degradation rate, the scaffold was more in line with the requirements of bone tissue engineering scaffolds. The Col-OSP scaffold was non-toxic, promoted the proliferation, adhesion, and differentiation of MC3T3-E1 cells, and stimulated the osteogenesis-related genes expressions of osteocalcin (OCN), collagen type I (COL-I) and RUNX2 of MC3T3-E1 cells.

Bioactive glass-based organic/inorganic hybrids: an analysis of the current trends in polymer design and selection

Bioactive glass-based organic/inorganic hybrids are a family of materials holding great promise in the biomedical field. Developed from bioactive glasses following recent advances in sol-gel and polymer chemistry, they can overcome many limitations of traditional composites typically used in bone repair and orthopedics. Thanks to their unique molecular structure, hybrids are often characterized by synergistic properties that go beyond a mere combination of their two components; it is possible to synthesize materials with a wide variety of mechanical and biological properties. The polymeric component, in particular, can be tailored to prepare tough, load-bearing materials, or rubber-like elastomers. It can also be a key factor in the determination of a wide range of interesting biological properties. In addition, polymers can also be used within hybrids as carriers for therapeutic ions (although this is normally the role of silica). This review offers a brief look into the history of hybrids, from the discovery of bioactive glasses to the latest developments, with a particular emphasis on polymer design and chemistry. First the benefits and limitations of hybrids will be discussed and compared with those of alternative approaches (for instance, nanocomposites). Then, key advances in the field will be presented focusing on the polymeric component: its chemistry, its physicochemical and biological advantages, its drawbacks, and selected applications. Comprehensive tables summarizing all the polymers used to date to fabricate sol-gel hybrids for biomedical applications are also provided, to offer a handbook of all the available candidates for hybrid synthesis. In addition to the current trends, open challenges and possible avenues of future development are proposed.

Facile Construction of Hybrid Hydrogels with High Strength and Biocompatibility for Cranial Bone Regeneration

The significant efforts being made towards the utilization of artificial soft materials holds considerable promise for developing tissue engineering scaffolds for bone-related diseases in clinics. However, most of these biomaterials cannot simultaneously satisfy the multiple requirements of high mechanics, good compatibility, and biological osteogenesis. In this study, an osteogenic hybrid hydrogel between the amine-functionalized bioactive glass (ABG) and 4-armed poly(ethylene glycol) succinimidyl glutarate-gelatin network (SGgel) is introduced to flexibly adhere onto the defective tissue and to subsequently guide bone regeneration. Relying on the rapid ammonolysis reaction between amine groups (-NH₂) of gelatin and ABG components and N-hydroxysuccinimide (NHS)-ester of tetra-PEG-SG polymer, the hydrogel networks were formed within seconds, offering a multifunctional performance, including easy injection, favorable biocompatibility, biological and mechanical properties (compressive strength: 4.2 MPa; storage modulus: 10⁴ kPa; adhesive strength: 56 kPa), which could facilitate the stem cell viability, proliferation, migration and differentiation into osteocytes. In addition, the integration between the SGgel network and ABG moieties within a nano-scale level enabled the hybrid hydrogel to form adhesion to tissue, maintain the durable osteogenesis and accelerate bone regeneration. Therefore, a robust approach to the simultaneously satisfying tough adhesion onto the tissue defects and high efficiency for bone regeneration on a mouse skull was achieved, which may represent a promising strategy to design therapeutic scaffolds for tissue engineering in clinical applications.

Enhanced formation of bioactive and strong silk-bioglass hybrid materials through organic-inorganic mutual molecular nucleation induction and templating

Materials based on silk fibroin (SF) are important for many biomedical applications due to their excellent biocompatibility and tunable biodegradability. However, the insufficient mechanical strength and low bioactivity of these materials have limited their applications. For silk hydrogels, slow gelation is also a crucial problem. In this work, a simple approach is developed to address these challenging problems all at once. By mixing SF solution with bioglass (BG) sol, instant gelation of silk is induced, the storage modulus of the hydrogel and the compressive modulus of the aerogel are significantly enhanced. The formation of a complex of SF and tetraethyl orthosilicate (TEOS), either through hydrogen bonding or TEOS condensation on SF, facilitated the aggregation of SF and, on the other hand, created active sites for the condensation of TEOS and BG formation on the surface of silk nanofibrils. The resultant hybrid gels have much higher capacity for biomineralization, indicating their higher bioactivity, compared with the pristine silk gels. This organic (SF)-inorganic (BG) mutual nucleation induction and templating can be used for a general approach to produce bioactive silk materials of various formats not limited to gels and may also inspire the formation of other functional protein-BG hybrid materials.

Osteogenic Effect of Fisetin Doping in Bioactive Glass/Poly(caprolactone) Hybrid Scaffolds

Treating large bone defects or fragile patients may require enhancing the bone regeneration rate to overcome a weak contribution from the body. This work investigates the osteogenic potential of nutrient fisetin, a flavonoid found in fruits and vegetables, as a doping agent inside the structure of a SiO₂-CaO bioactive glass-poly(caprolactone) (BG-PCL) hybrid scaffold. Embedded in the full mass of the BG-PCL hybrid during one-pot synthesis, we demonstrate fisetin to be delivered sustainably; the release follows a first-order kinetics with active fisetin concentration being delivered for more than 1 month (36 days). The biological effect of BG-PCL-fisetin-doped scaffolds (BG-PCL-Fis) has been highlighted by in vitro and in vivo studies. A positive impact is demonstrated on the adhesion and the differentiation of rat primary osteoblasts, without an adverse cytotoxic effect. Implantation in critical-size mouse calvaria defects shows bone remodeling characteristics and remarkable enhancement of bone regeneration for fisetin-doped scaffolds, with the regenerated bone volume being twofold that of nondoped scaffolds and fourfold that of a commercial trabecular bovine bone substitute. Such highly bioactive materials could stand as competitive alternative strategies involving biomaterials loaded with growth factors, the use of the latter being the subject of growing concerns.

Material-Assisted Strategies for Osteochondral Defect Repair

The osteochondral (OC) unit plays a pivotal role in joint lubrication and in the transmission of constraints to bones during movement. The OC unit does not spontaneously heal; therefore, OC defects are considered to be one of the major risk factors for developing long-term degenerative joint diseases such as osteoarthritis. Yet, there is currently no curative treatment for OC defects, and OC regeneration remains an unmet medical challenge. In this context, a plethora of tissue engineering strategies have been envisioned over the last two decades, such as combining cells, biological molecules, and/or biomaterials, yet with little evidence of successful clinical transfer to date. This striking observation must be put into perspective with the difficulty in comparing studies to identify overall key elements for success. This systematic review aims to provide a deeper insight into the field of material-assisted strategies for OC regeneration, with particular considerations for the therapeutic potential of the different approaches (with or without cells or biological molecules), and current OC regeneration evaluation methods. After a brief description of the biological complexity of the OC unit, the recent literature is thoroughly analyzed, and the major pitfalls, emerging key elements, and new paths to success are identified and discussed.

Tailored therapeutic release from polycaprolactone-silica hybrids for the treatment of osteomyelitis: antibiotic rifampicin and osteogenic silicates

The treatment of osteomyelitis, a destructive inflammatory process caused by bacterial infections to bone tissue, is one of the most critical challenges of orthopedics and bone regenerative medicine. The standard treatment consists of intense antibiotic therapies combined with tissue surgical debridement and the application of a bone defect filler material. Unfortunately, commercially available candidates, such as gentamicin-impregnated polymethylmethacrylate cements, possess very poor pharmacokinetics (i.e., 24 hours burst release) and little to no regenerative potential. Fostered by the intrinsic limitations associated with conventional treatments, alternative osteostimulative biomaterials with local drug delivery have recently started to emerge. In this study, we propose the use of a polycaprolactone-silica sol-gel hybrid material as carrier for the delivery of rifampicin, an RNA-polymerase blocker often used to treat bone infections, and of osteostimulative silicate ions. The release of therapeutic agents from the material is dual, offering two separate and simultaneous effects, and decoupled, meaning that the kinetics of rifampicin and silicate releases are independent from each other. A series of hybrid formulations with increasing amounts of rifampicin was prepared. The antibiotic loading efficacy, as well as the release profiles of rifampicin and silicates were measured. The characterization of cell viability and differentiation of rat primary osteoblasts and antibacterial performance were also performed. Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli were selected due to their high occurrence in bone infections. Results confirmed that rifampicin can be successfully loaded within the hybrids without significant degradation and that it is possible to tailor the antibiotic release according to need. Once in a physiological environment, the rapid release of silicates was associated with optimal cell proliferation and the overexpression of osteoblastic differentiation. Simultaneously, rifampicin is delivered over the course of several weeks with significant inhibition of all tested strains. In particular, the materials caused a growth reduction of 7-10 orders of magnitude in Staphylococcus aureus, the major strain responsible for osteomyelitis worldwide. Our data strongly suggest that PCL/silica hybrids are a very promising candidate to develop bone fillers with superior biological performance compared to currently available options. Thanks to their unique synthesis route and their dual tailored release they can promote bone regeneration while reducing the risk of infection for several weeks upon implantation.

Calcium phosphate and silicate-based nanoparticles: history and emerging trends

Bulk calcium phosphates and silicate-based bioglasses have been extensively studied since the early 1970s due to their unique capacity to bind to host bone, which led to their clinical translation and commercialization in the 1980s. Since the mid-1990s, researchers have synthesized nanoscale calcium phosphate and silicate-based particles of increased specific surface area, chemical reactivity and solubility which offer specific advantages as compared to their bulk counterparts. This review provides a critical perspective on the history and emerging trends of these two classes of ceramic nanoparticles. Their synthesis and functional properties in terms of particle composition, size, shape, charge, dispersion, and toxicity are discussed as a function of relevant processing parameters. Specifically, emerging trends such as the influence of ion doping and mesoporosity on the biological and pharmaceutical performance of these nanoparticles are reviewed in more detail. Finally, a broad comparative overview is provided on the physicochemical properties and applicability of calcium phosphate and silicate-based nanoparticles within the fields of i) local delivery of therapeutic agents, ii) functionalization of biomaterial scaffolds or implant coatings, and iii) bio-imaging applications.

Functional Macromolecular Adhesives for Bone Fracture Healing

Compared with traditional internal fixation devices, bone adhesives are expected to exhibit remarkable advantages, such as improved fixation of comminuted fractures and maintained spatial location of fractured scattered bone pieces in treating bone injuries. In this review, different bone adhesives are summarized from the aspects of bone tissue engineering, and the applications of bone adhesives are emphasized. The concepts of "liquid scaffold" and "liquid plate" are proposed to summarize two different research directions of bone adhesives. Furthermore, significant advances of bone adhesives in recent years in mechanical strength, osseointegration, osteoconductivity, and osteoinductivity are discussed. We conclude this topic by providing perspectives on the state-of-the-art research progress and future development trends of bone adhesives. We hope this review will provide a comprehensive summary of bone adhesives and inspire more extensive and in-depth research on this subject.

Potential of tailored amorphous multiporous calcium silicate glass for pulp capping regenerative endodontics-A preliminary assessment

INTRODUCTION/OBJECTIVE

The tailored amorphous multi-porous (TAMP) material fabrication technology has led to a new class of bioactive materials possessing versatile characteristics. It has not been tested for dental applications. Thus, we aimed to assess its biocompatibility and ability to regenerate dental mineral tissue.

METHODS

30CaO-70SiO₂ model TAMP discs were fabricated by a sol-gel method followed by in vitro biocompatibility testing with isolated human or mini-swine dental pulp stem cells (DPSCs). TAMP scaffolds were tested in vivo as a pulp exposure (pin-point, 1 mm, 2 mm, and entire pulp chamber roof) capping material in the molar teeth of mini-swine.

RESULTS

The in vitro assays showed that DPSCs attached well onto the TAMP discs with comparable viability to those attached to culture plates. Pulp capping tests on mini-swine showed that after 4.5 months TAMP material was still present at the capping site, and mineral tissue (dentin bridge) had formed in all sizes of pulp exposure underneath the TAMP material.

CONCLUSIONS

TAMP calcium silicate is biocompatible with both human and swine DPSCs in vitro and with pulp in vivo, it may help regenerate the dentin bridge after pulp exposure.

The effects of oyster shell/alpha-calcium sulfate hemihydrate/platelet-rich plasma/bone mesenchymal stem cells bioengineering scaffold on rat critical-sized calvarial defects

Engineering scaffolds combining natural biomineral and artificially synthesized material hold promising potential for bone tissue regeneration. We fabricated a bioengineering scaffold, oyster shell (OS) and alpha-calcium sulfate hemihydrate (α-CSH) as scaffold, platelet-rich plasma (PRP) as provider of growth factors and bone mesenchymal stem cells (BMSCs) as seed cells, and determined it could be applied as a new type of bone graft substitutes by rat calvarial defects repairing experiment in vitro and in vivo. SEM showed that the mean diameter of the pores was about 150 μm with a range of 50-200 μm, and scaffold's porosity was ~27.4% by Archimedes' Principle. In vitro, Scaffold + BMSCs + PRP group presented a higher ALP activity compared with other groups by ELISA (P < 0.05). But the expression of OC was not detectable on day 4 or 8. The MTT assay showed that the relative cell number of BMSCs+PRP group increased significantly (P < 0.05). In vivo, the smallest defect area of skull and highest volume of regenerated new bone were observed in Scaffold + PRP + BMSCs group by X-ray and Micro-CT analysis (P < 0.05). And the similar results also were observed in HE and Masson staining. The immunohistochemistry staining for osteogenic marker proteins ALP and OC showed that the most obvious positive staining was observed in Scaffold + PRP + BMSCs group (P < 0.05). The expression of inflammatory markers IL-6 and TNF-α was the lowest in control group (P < 0.05). In conclusion, a bioengineering scaffold based on OS, created by simply combining α-CSH and PRP and implanting with BMSCs, could be clinically useful and has marked advantages as a targeted, off-the-shelf, cell-loaded treatment option for the bone healing of critical-size calvarial defects.

Bioactive Glasses: A Promising Therapeutic Ion Release Strategy for Enhancing Wound Healing

The morbidity, mortality, and burden of burn victims and patients with severe diabetic wounds are still high, which leads to an extensively growing demand for novel treatments with high clinical efficacy. Biomaterial-based wound treatment approaches have progressed over time from simple cotton wool dressings to advanced skin substitutes containing cells and growth factors; however, no wound care approach is yet completely satisfying. Bioactive glasses are materials with potential in many areas that exhibit unique features in biomedical applications. Today, bioactive glasses are not only amorphous solid structures that can be used as a substitute in hard tissue but also are promising materials for soft tissue regeneration and wound healing applications. Biologically active elements such as Ag, B, Ca, Ce, Co, Cu, Ga, Mg, Se, Sr, and Zn can be incorporated in glass networks; hence, the superiority of these multifunctional materials over current materials results from their ability to release multiple therapeutic ions in the wound environment, which target different stages of the wound healing process. Bioactive glasses and their dissolution products have high potency for inducing angiogenesis and exerting several biological impacts on cell functions, which are involved in wound healing and some other features that are valuable in wound healing applications, namely hemostatic and antibacterial properties. In this review, we focus on skin structure, the dynamic process of wound healing in injured skin, and existing wound care approaches. The basic concepts of bioactive glasses are reviewed to better understand the relationship between glass structure and its properties. We illustrate the active role of bioactive glasses in wound repair and regeneration. Finally, research studies that have used bioactive glasses in wound healing applications are summarized and the future trends in this field are elaborated.

Mg-Based Metallic Glass-Polymer Composites: Investigation of Structure, Thermal Properties, and Biocompatibility

In this work, the biomedical applicability and physical properties of magnesium-based metallic glass/polycaprolactone (PCL) composites are explored. The composites were fabricated via mechanical alloying and subsequent coextrusion. The coextrusion process was carried out at a temperature near to the supercooled liquid region of the metallic glass and the viscous region of the polymer. The structures, as well as thermal and mechanical properties of the obtained samples were characterized, and in vivo investigations were undertaken. The composite samples possess acceptable thermal and mechanical properties. Tensile tests indicate the ability of the composites to withstand more than 100% deformation. In vivo studies reveal that the composites are biologically compatible and could be promising for biomedical applications.

Pilot Experience on the Use of S54P4 Bioactive Glass in the Surgical Management of Diabetic Foot Osteomyelitis

To test safety and efficacy of bioactive glass, a novel material used to replace bone, able to completely bond itself to the host tissues on patients treated for osteomyelitis (OM) complicating a diabetic foot (DF). We evaluated a group of patients consecutively admitted in our department between September and December 2018, who underwent surgical DF procedures for OM and in whom the use of bioactive glass could limit the demolition phase of surgical procedure. Patients were treated with bioactive glass S53P4 on top of standard treatment directly in operating room. The patients were weekly controlled for 6 months or until complete healing. During follow-up, we analyzed primarily healing rate and secondarily time of healing, need for further debridement procedures, recurrences, and adverse or hypersensitivity reactions to study treatment. Ten DF patients were enrolled (male/female 6/4; mean age 56 ± 11 years; mean duration of diabetes 10.5 ± 4.7 years, mean hemoglobin A1c 7.2 ± 0.9%). Patients underwent surgical procedure during which, after an accurate debridement, bioactive glass was applied. A healing rate of 80% in a mean time of 34 ± 2 days, with only 1 patient who needed a second surgical look, was observed. Neither recurrences nor adverse events during follow-up were observed in treated patients. This pilot experience demonstrated that bioactive glass can be considered a useful tool for the surgical treatment of DF-related OM.

Effect of nanoscale bioactive glass with radial spherical particles on osteogenic differentiation of rat bone marrow mesenchymal stem cells

To validate the feasibility of two types of bioactive glass that contains spherical and radical spherical nano-sized particles in promoting bone repair, we hypothesize that radical spherical nano-sized particles have higher bone repair effectiveness than spherical one due to the physicochemical properties. We rigorously compared the physicochemical properties and bioactivities of these two types of bioactive glass. Specifically, we measured the size, surface morphology, concentration of ionic-dissolution products, bioactivity, and biological effects of two groups of bioactive glass on rat bone marrow mesenchymal stem cells (rBMSCs) and evaluate their effect on proliferation and osteogenic differentiation of rBMSCs in vitro. We observed that spherical nano-bioactive glass (SNBG) was spherical with smooth boundary, while the radial spherical nano-bioactive glass (RSNBG) had radial pore on the surface of particle boundary. When the two materials were immersed in simulated body fluid for 24 h, RSNBG produced more and denser hydroxyapatite carbonate than SNBG. The concentration of Ca and Si ions in RSNBG 24 h extract is higher than that of SNBG, while the concentration of P ions is lower. Proliferation, alkaline phosphatase (ALP) activity, intracellular Ca ion concentrations defined as the number of mineralized nodules produced, and the expression of osteogenic genes were significantly higher in rBMSCs co-cultured with 50 µg/mL RSNBG than SNBG. Overall, these results validated our hypothesis that RSNBG can provide better benefit than SNBG for inducing proliferation and osteogenic differentiation in rBMSCs, in turn suggested the feasibility of this RSNBG in further studies and utilization toward the ends of improved bone repair effectiveness.

Bioactive Pore-Forming Bone Adhesives Facilitating Cell Ingrowth for Fracture Healing

The effectiveness of commercial bone adhesives is known to be hampered by the weak efficacy of cell ingrowth. The strategy of macropore-forming, especially bioactive macropores, holds considerable promise to circumvent this problem, thereby promoting fracture healing. Herein, a class of bioactive glass-involved macropore-embedded bone adhesives is developed, which is capable of facilitating the migration of bone-derived mesenchymal stromal cells into the adhesive layer and differentiation into osteocytes. The integration of bioactive glass-particle-encapsulated porogens in the bone adhesives is key to this approach. A robust instant bonding on the bone adhesive and a high efficiency of bone regeneration on a mouse skull are observed, both of which are vital for clinical applications and personalized surgical procedures. This work represents a general strategy to design biomaterials with high cell-ingrowth efficacy.