Multifunctional antibiotic- and zinc-containing mesoporous bioactive glass scaffolds to fight bone infection

Tailoring of bioactive glass and glass-ceramics properties for in vitro and in vivo response optimization: a review

Bioactive glasses are inorganic biocompatible materials that can find applications in many biomedical fields. The main application is bone and dental tissue engineering. However, some applications in contact with soft tissues are emerging. It is well known that both bulk (such as composition) and surface properties (such as morphology and wettability) of an implanted material influence the response of cells in contact with the implant. This review aims to elucidate and compare the main strategies that are employed to modulate cell behavior in contact with bioactive glasses. The first part of this review is focused on the doping of bioactive glasses with ions and drugs, which can be incorporated into the bioceramic to impart several therapeutic properties, such as osteogenic, proangiogenic, or/and antibacterial ones. The second part of this review is devoted to the chemical functionalization of bioactive glasses using drugs, extra-cellular matrix proteins, vitamins, and polyphenols. In the third and final part, the physical modifications of the surfaces of bioactive glasses are reviewed. Both top-down (removing materials from the surface, for example using laser treatment and etching strategies) and bottom-up (depositing materials on the surface, for example through the deposition of coatings) strategies are discussed.

Mesoporous zinc oxide-based drug delivery system offers an antifungal and immunoregulatory strategy for treating keratitis

Fungal keratitis is a refractory eye disease that is prone to causing blindness. Fungal virulence and inflammatory responses are two major factors that accelerate the course of fungal keratitis. However, the current antifungal drugs used for treatment usually possess transient residence time on the ocular surface and low bioavailability deficiencies, which limit their therapeutic efficacy. In this work, natamycin (NATA)-loaded mesoporous zinc oxide (Meso-ZnO) was synthesized for treating Aspergillus fumigatus keratitis with excellent drug-loading and sustained drug release capacities. In addition to being a carrier for drug delivery, Meso-ZnO could restrict fungal growth in a concentration-dependent manner, and the transcriptome analysis of fungal hyphae indicated that it inhibited the mycotoxin biosynthesis, oxidoreductase activity and fungal cell wall formation. Meso-ZnO also promoted cell migration and exhibited anti-inflammatory role during fungal infection by promoting the activation of autophagy. In mouse models of fungal keratitis, Meso-ZnO/NATA greatly reduced corneal fungal survival, alleviated tissue inflammatory damage, and reduced neutrophils accumulation and cytokines expression. This study suggests that Meso-ZnO/NATA can be a novel and effective treatment strategy for fungal keratitis.

Engineering mesoporous bioactive glasses for emerging stimuli-responsive drug delivery and theranostic applications

Mesoporous bioactive glasses (MBGs), which belong to the category of modern porous nanomaterials, have garnered significant attention due to their impressive biological activities, appealing physicochemical properties, and desirable morphological features. They hold immense potential for utilization in diverse fields, including adsorption, separation, catalysis, bioengineering, and medicine. Despite possessing interior porous structures, excellent morphological characteristics, and superior biocompatibility, primitive MBGs face challenges related to weak encapsulation efficiency, drug loading, and mechanical strength when applied in biomedical fields. It is important to note that the advantageous attributes of MBGs can be effectively preserved by incorporating supramolecular assemblies, miscellaneous metal species, and their conjugates into the material surfaces or intrinsic mesoporous networks. The innovative advancements in these modified colloidal inorganic nanocarriers inspire researchers to explore novel applications, such as stimuli-responsive drug delivery, with exceptional in-vivo performances. In view of the above, we outline the fabrication process of calcium-silicon-phosphorus based MBGs, followed by discussions on their significant progress in various engineered strategies involving surface functionalization, nanostructures, and network modification. Furthermore, we emphasize the recent advancements in the textural and physicochemical properties of MBGs, along with their theranostic potentials in multiple cancerous and non-cancerous diseases. Lastly, we recapitulate compelling viewpoints, with specific considerations given from bench to bedside.

Strontium and Zinc Co-Doped Mesoporous Bioactive Glass Nanoparticles for Potential Use in Bone Tissue Engineering Applications

Mesoporous bioactive glass nanoparticles (MBGNs) have attracted significant attention as multifunctional nanocarriers for various applications in both hard and soft tissue engineering. In this study, multifunctional strontium (Sr)- and zinc (Zn)-containing MBGNs were successfully synthesized via the microemulsion-assisted sol-gel method combined with a cationic surfactant (cetyltrimethylammonium bromide, CTAB). Sr-MBGNs, Zn-MBGNs, and Sr-Zn-MBGNs exhibited spherical shapes in the nanoscale range of 100 ± 20 nm with a mesoporous structure. Sr and Zn were co-substituted in MBGNs (60SiO2-40CaO) to induce osteogenic potential and antibacterial properties without altering their size, morphology, negative surface charge, amorphous nature, mesoporous structure, and pore size. The synthesized MBGNs facilitated bioactivity by promoting the formation of an apatite-like layer on the surface of the particles after immersion in Simulated Body Fluid (SBF). The effect of the particles on the metabolic activity of human mesenchymal stem cells was concentration-dependent. The hMSCs exposed to Sr-MBGNs, Zn-MBGNs, and Sr-Zn-MBGNs at 200 μg/mL enhanced calcium deposition and osteogenic differentiation without osteogenic supplements. Moreover, the cellular uptake and internalization of Sr-MBGNs, Zn-MBGNs, and Sr-Zn-MBGNs in hMSCs were observed. These novel particles, which exhibited multiple functionalities, including promoting bone regeneration, delivering therapeutic ions intracellularly, and inhibiting the growth of Staphylococcus aureus and Escherichia coli, are potential nanocarriers for bone regeneration 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.

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.

Enhancing Osteoblastic Cell Cultures with Gelatin Methacryloyl, Bovine Lactoferrin, and Bioactive Mesoporous Glass Scaffolds Loaded with Distinct Parsley Extracts

The increasing interest in innovative solutions for addressing bone defects has driven research into the use of Bioactive Mesoporous Glasses (MBGs). These materials, distinguished by their well-ordered mesoporous structure, possess the capability to accommodate plant extracts with well-established osteogenic properties, including bovine lactoferrin (bLF), as part of their 3D scaffold composition. This harmonizes seamlessly with the ongoing advancements in the field of biomedicine. In this study, we fabricated 3D scaffolds utilizing MBGs loaded with extracts from parsley leaves (PL) and embryogenic cultures (EC), rich in bioactive compounds such as apigenin and kaempferol, which hold potential benefits for bone metabolism. Gelatin Methacryloyl (GelMa) served as the polymer, and bLF was included in the formulation. Cytocompatibility, Runx2 gene expression, ALP enzyme activity, and biomineralization were assessed in preosteoblastic MC3T3-E1 cell cultures. MBGs effectively integrated PL and EC extracts with loadings between 22.6 ± 0.1 and 43.6 ± 0.3 µM for PL and 26.3 ± 0.3 and 46.8 ± 0.4 µM for EC, ensuring cell viability through a release percentage between 28.3% and 59.9%. The incorporation of bLF in the 3D scaffold formulation showed significant differences compared to the control in all assays, even at concentrations below 0.2 µM. Combinations, especially PL + bLF at 0.19 µM, demonstrated additive potential, with superior biomineralization compared to EC. In summary, this study highlights the effectiveness of MBGs in incorporating PL and EC extracts, along with bLF, into 3D scaffolds. The results underscore cytocompatibility, osteogenic activity, and biomineralization, offering exciting potential for future in vivo applications.

Micelle encapsulated curcumin and piperine-laden 3D printed calcium phosphate scaffolds enhance in vitro biological properties

Limitations in the current clinical management of critical-sized osseous defects have driven the need for multifunctional bone constructs. The ideal bone scaffold should possess advanced microarchitecture, well-defined pore interconnectivity, and supply biological signals, which actively guide and control tissue regeneration while simultaneously preventing post-implantation complications. Here, a natural medicine-based localized drug delivery from 3D printed scaffold is presented, which offers controlled release of curcumin, piperine from nano-sized polymeric micelles, and burst release of antibacterial carvacrol from the coating endowing the scaffold with their distinct, individual biological properties. This functionalized scaffold exhibits improved osteoblast (hFOB) cell attachment, 4-folds higher hFOB proliferation, and 73% increased hFOB differentiation while simultaneously providing cytotoxicity towards osteosarcoma cells with 61% lesser viability compared to control. In vitro, early tube formation (p < 0.001) indicates that the scaffolds can modulate the endothelial cellular network, critical for faster wound healing. The scaffold also exhibits 94% enhanced antibacterial efficacy (p < 0.001) against gram-positive Staphylococcus aureus, the main causative bacteria for osteomyelitis. Together, the multifunctional scaffolds provide controlled delivery of natural biomolecules from the nano-sized micelle-loaded 3D printed matrix for significant improvement in osteoblast proliferation, endothelial formation, osteosarcoma, and bacterial inhibition, guiding better bone regeneration for post-traumatic defect repair.

Desing and comparison of bone substitutes. Study of in vivo behavior in a rabbit model

AIM

Compare bone formation capacity in vivo of two types of biomaterials designed as bone substitutes with respect to iliac crest autograft, one based on carbonate hydroxyapatites and the other one on bioactive mesoporous glass.

MATERIALS AND METHODS

Experimental study consisting on 14 adult female New Zeland rabbits where a critical defect was made in the rabbit radius bone. The sample was divided into four groups: defect without material, with iliac crest autograft, with carbonatehydroxyapatite support, and with bioactive mesoporous glass support. Serial X-ray studies were carried out at 2, 4, 6 and 12 weeks and a microCT study at euthanasia at 6 and 12 weeks.

RESULTS

In the X-ray study, autograft group showed the highest bone formation scores. Both groups of biomaterials presented bone formation similar and greater than the defect without material, but always less than in the autograft group. The results of the microCT study showed the largest bone volume in the study area in the autograft group. The groups with bone substitutes presented greater bone volume than the group without material but always less than in the autograft group.

CONCLUSION

Both supports seem to promote bone formation but are not capable of reproducing the characteristics of autograft. Due to their different macroscopic characteristics, each one could be suitable for a different type of defect.

[Translated article] Design and comparison of bone substitutes. Study of in vivo behaviour in a rabbit model

AIM

To compare the in vivo bone formation capacity of of biomaterials designed as bone substitutes with respect to iliac crest autograft, one based on carbonate hydroxiapatite and the other one on bioactive mesoporous glass.

MATERIALS AND METHODS

Experimental study consisting on 14 adult female New Zeland rabbits where a critical defect was made in the rabbit radius bone. The sample was divided into four groups: defect without material, with iliac crest autograft, with carbonatehydroxyapatite scaffold, and with bioactive mesoporous glass scaffold. Serial X-ray studies were carried out at 2, 4, 6 and 12 weeks and a microCT study at euthanasia at 6 and 12 weeks.

RESULTS

In the X-ray study, autograft group showed the highest bone formation scores. Both groups of biomaterials presented bone formation similar and greater than the defect without material, but always less than in the autograft group. The results of the microCT study showed the largest bone volume in the study area in the autograft group. The groups with bone substitutes presented greater bone volume than the group without material but always less than the autograft group.

CONCLUSION

Both scaffolds seem to promote bone formation but are not capable of reproducing the characteristics of autograft. Due to their different macroscopic characteristics, each one could be suitable for a different type of defect.

Multifunctional Zn and Ag co-doped bioactive glass nanoparticles for bone therapeutic and regeneration

Bone cancer has traditionally been treated using surgery, radiotherapy, and/or chemotherapy. The nonspecific distribution of chemotherapy and implantable infections are significant risk factors for the failure of the bone to heal. Multifunctional zinc and silver co-doped bioactive glass nanoparticles (yAg-xZn-BGNPs) with a diameter of 150 ± 30 nm were successfully synthesized using modified sol-gel and two-step post-functionalization processes, tailored to provide antibacterial and anticancer activity whilst maintaining osteogenesis ability. Co-doped BGNPs with Zn and Ag did not significantly alter physicochemical properties, including size, morphology, glass network, and amorphous nature. Apatite-like layer was observed on the surface of yAg-xZn-BGNPs and resorbed in the simulated body fluid solution, which could increase their bioactivity. Human fetal osteoblast cell line (hFOB 1.19) treated with particles showed calcified tissue formation and alkaline phosphatase activity in the absence of osteogenic supplements in vitro, especially with 0.5Ag-1Zn-BGNPs. Moreover, these particles preferentially disrupted the metabolic activity of bone cancer cells (MG-63) and had an antibacterial effect against B. subtilis, E. coli, and S. aureus via the disc diffusion method. This novel 0.5Ag-1Zn-BGNP and 1Ag-1Zn-BGNPs, with wide-ranging ability to stimulate bone regeneration, to inhibit bone cancer cell proliferation, and to prevent bacterial growth properties, may provide a feasible strategy for bone cancer treatment. The 0.5Ag-1Zn-BGNPs and 1Ag-1Zn-BGNPs can be applied for the preparation of scaffolds or filler composites using in bone tissue engineering.

Novel coatings for the continuous repair of human bone defects

Bone defects are the second most common tissue grafts after blood. However, bone grafts face several problems, such as bone scaffolds, which have low bioactivity and are prone to corrosion. Much of the current research on bone scaffolds is focused on the mechanical aspects such as structure and strength. Surface modification of the bone scaffold is carried out in terms of the mechanical structure or structural design of the bone scaffold with reference to a bionic structure. However, with the development of mechanical designs, materials science, and medicine, many studies have reported that promoting bone growth by modifying the structure of the scaffold or coating is not possible. Therefore, the application of a bioactive coating to the surface of the bone scaffold is particularly important to generate a synergistic effect between the structure and active coating. In this article, we present several perspectives to improve the bioactivity of bone scaffolds, including corrosion resistance, loading of bioactive coatings or drugs on bone scaffolds, improved adhesion to the surface of the bone scaffolds, immune response modulation, and drawing on bionic structures during manufacturing.

Antibacterial effect of 3D printed mesoporous bioactive glass scaffolds doped with metallic silver nanoparticles

The development of new biomaterials for bone tissue regeneration with high bioactivity abilities and antibacterial properties is being intensively investigated. We have synthesized nanocomposites formed by mesoporous bioactive glasses (MBGs) in the ternary SiO₂, CaO and P₂O₅ system doped with metallic silver nanoparticles (AgNPs) that were homogenously embedded in the MBG matrices. Ag/MBG nanocomposites have been directly synthesized and silver species were spontaneously reduced to metallic AgNPs by high temperatures (700 °C) obtained of last MBG synthesis step. Three-dimensional silver-containing mesoporous bioactive glass scaffolds were fabricated showing uniformly interconnected ultrapores, macropores and mesopores. The manufacture method consisted of a combination of a single-step sol-gel route in the mesostructure directing agent (P123) presence and a biomacromolecular polymer such as (hydroxypropyl)methyl cellulose (HPMC) as the macrostructure template, followed by rapid prototyping (RP) technique. Biological properties of Ag/MBG nanocomposites were evaluated by MC3T3-E1 preosteoblastic cells culture tests and bacterial (E. coli and S. aureus) assays. The results showed that the MC3T3-E1 cells morphology was not affected while preosteoblastic proliferation decreased when the presence of silver increased. Antimicrobial assays indicated that bacterial growth inhibition and biofilm destruction were directly proportional to the increased presence of AgNPs in the MBG matrices. Furthermore, in vitro co-culture of MC3T3-E1 cells and S. aureus bacteria confirmed that AgNPs presence was necessary for antibacterial activity, and AgNPs slightly affected cell proliferation parameters. Therefore, 3D printed scaffolds with hierarchical pore structure and high antimicrobial capacity have potential applications in bone tissue regeneration. STATEMENT OF SIGNIFICANCE: This study combines three key scientific aspects for bone tissue engineering: (i) materials with high bioactivity to repair and regenerate bone tissue that (ii) contain antibacterial agents to reduce the infection risk (iii) in the form of three-dimensional scaffolds with hierarchical porosity. Innovative methodology is described here: sol-gel method, which is employed to obtain mesoporous bioactive glass matrices doped with metallic silver nanoparticles where different polymer templates facilitate the different size scales presence, and rapid prototyping technique that provides ultra-large macroporosity according to computer-aided design. The dual scaffolds obtained are biocompatible and deliver active doses of silver capable of combating bone infections, which represent one of the most serious complications associated to surgical treatments of bone diseases and fractures.

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.

In Vitro and In Vivo Response of Zinc-Containing Mesoporous Bioactive Glasses in a Sheep Animal Model

Zinc-enriched mesoporous bioactive glasses (MBGs) are bioceramics with potential antibacterial and osteogenic properties. However, few assays have been performed to study these properties in animal models. In this study, MBGs enriched with up to 5% ZnO were synthesized, physicochemically characterized, and evaluated for their osteogenic activity both in vitro and in vivo. The ZnO MBGs showed excellent textural properties despite ZnO incorporation. However, the release of Zn²⁺ ions inhibited the mineralization process when immersed in simulated body fluid. In vitro assays showed significantly higher values of viability and expression of early markers of cell differentiation and angiogenesis in a ZnO-content-dependent manner. The next step was to study the osteogenic potential in a sheep bone defect model. Despite their excellent textural properties and cellular response in vitro, the ZnO MBGs were not able to integrate into the bone tissue, which can be explained in terms of inhibition of the mineralization process caused by Zn²⁺ ions. This work highlights the need to develop nanostructured materials for bone regeneration that can mineralize to interact with bone tissue and induce the processes of implant acceptance, cell colonization by osteogenic cells, and regeneration of lost bone tissue.

Antibiofilm Activity of Biocide Metal Ions Containing Bioactive Glasses (BGs): A Mini Review

One of the major clinical issues during the implantation procedure is the bacterial infections linked to biofilms. Due to their tissue localization and the type of bacteria involved, bacterial infections at implant sites are usually difficult to treat, which increases patient morbidity and even mortality. The difficulty of treating biofilm-associated infections and the emergence of multidrug-resistant bacteria are further challenges for the scientific community to develop novel biomaterials with excellent biocompatibility and antibacterial properties. Given their ability to stimulate bone formation and have antibacterial properties, metal ion-doped bioactive glasses (BGs) have received considerable research. This mini review aims to be successful in presenting the developments made about the role of biocide metal ions incorporated into BGs against the development of bacterial biofilms and the spread of nosocomial diseases.

Effects of Zinc, Magnesium, and Iron Ions on Bone Tissue Engineering

Large-sized bone defects are a great challenge in clinics and considerably impair the quality of patients' daily life. Tissue engineering strategies using cells, scaffolds, and bioactive molecules to regulate the microenvironment in bone regeneration is a promising approach. Zinc, magnesium, and iron ions are natural elements in bone tissue and participate in many physiological processes of bone metabolism and therefore have great potential for bone tissue engineering and regeneration. In this review, we performed a systematic analysis on the effects of zinc, magnesium, and iron ions in bone tissue engineering. We focus on the role of these ions in properties of scaffolds (mechanical strength, degradation, osteogenesis, antibacterial properties, etc.). We hope that our summary of the current research achievements and our notifications of potential strategies to improve the effects of zinc, magnesium, and iron ions in scaffolds for bone repair and regeneration will find new inspiration and breakthroughs to inspire future research.

Novel functionalized selenium nanowires as antibiotic adjuvants in multiple ways to overcome drug resistance of multidrug-resistant bacteria

Methicillin-resistant Staphylococcus (MRS) is a multi-drug resistant bacteria that pose a serious threat to human health. Antibacterial nanomaterials are becoming a promising antibiotic substitute or antibiotic adjuvants. In this work, selenium nanowires were modified with nano‑silver (Ag NPs) with antibacterial activity and [Ru(bpy)₂dppz]²⁺ with fluorescent labeling of DNA (SRA), and the antibacterial activity, antibacterial mechanism and biological toxicity of SRA synergistic antibiotics were studied. In vitro, antibacterial results show that SRA (12 μg/mL) improves the antibacterial activity of various antibiotics against resistant bacteria and significantly slows the development of bacterial resistance to antibiotics. Studies on antibacterial mechanisms have shown that SRA synergistic antibiotics destroy drug-resistant bacteria through a combination of physical (physical damage) and chemical pathways (destruction of biofilm, membrane depolarization, cell membrane destruction, adenosine triphosphate consumption and reactive oxygen species production). Transcriptomics analysis found that SRA affects bacterial activity by affecting bacterial biosynthesis, ATP synthesis and biofilm formation. Furthermore, SRA synergistic antibiotics can accelerate wound healing of bacterial infection by reducing the inflammatory response. The toxicity evaluation results show that SRA has extremely low cellular and in vivo toxicity. SRA has the potential of clinical application as multiple antibiotic adjuvants to deal with resistant bacterial infections.

Inorganic Nanoparticles in Bone Healing Applications

Modern biomedicine aims to develop integrated solutions that use medical, biotechnological, materials science, and engineering concepts to create functional alternatives for the specific, selective, and accurate management of medical conditions. In the particular case of tissue engineering, designing a model that simulates all tissue qualities and fulfills all tissue requirements is a continuous challenge in the field of bone regeneration. The therapeutic protocols used for bone healing applications are limited by the hierarchical nature and extensive vascularization of osseous tissue, especially in large bone lesions. In this regard, nanotechnology paves the way for a new era in bone treatment, repair and regeneration, by enabling the fabrication of complex nanostructures that are similar to those found in the natural bone and which exhibit multifunctional bioactivity. This review aims to lay out the tremendous outcomes of using inorganic nanoparticles in bone healing applications, including bone repair and regeneration, and modern therapeutic strategies for bone-related pathologies.

Bacteria-Assisted Transport of Nanomaterials to Improve Drug Delivery in Cancer Therapy

Currently, the design of nanomaterials for the treatment of different pathologies is presenting a major impact on biomedical research. Thanks to this, nanoparticles represent a successful strategy for the delivery of high amounts of drugs for the treatment of cancer. Different nanosystems have been designed to combat this pathology. However, the poor penetration of these nanomaterials into the tumor tissue prevents the drug from entering the inner regions of the tumor. Some bacterial strains have self-propulsion and guiding capacity thanks to their flagella. They also have a preference to accumulate in certain tumor regions due to the presence of different chemo-attractants factors. Bioconjugation reactions allow the binding of nanoparticles in living systems, such as cells or bacteria, in a simple way. Therefore, bacteria are being used as a transport vehicle for nanoparticles, facilitating their penetration and the subsequent release of the drug inside the tumor. This review would summarize the literature on the anchoring methods of diverse nanosystems in bacteria and, interestingly, their advantages and possible applications in cancer therapy.

Mesoporous Bioglasses Enriched with Bioactive Agents for Bone Repair, with a Special Highlight of María Vallet-Regí’s Contribution

Throughout her impressive scientific career, Prof. María Vallet-Regí opened various research lines aimed at designing new bioceramics, including mesoporous bioactive glasses for bone tissue engineering applications. These bioactive glasses can be considered a spin-off of silica mesoporous materials because they are designed with a similar technical approach. Mesoporous glasses in addition to SiO₂ contain significant amounts of other oxides, particularly CaO and P₂O₅ and therefore, they exhibit quite different properties and clinical applications than mesoporous silica compounds. Both materials exhibit ordered mesoporous structures with a very narrow pore size distribution that are achieved by using surfactants during their synthesis. The characteristics of mesoporous glasses made them suitable to be enriched with various osteogenic agents, namely inorganic ions and biopeptides as well as mesenchymal cells. In the present review, we summarize the evolution of mesoporous bioactive glasses research for bone repair, with a special highlight on the impact of Prof. María Vallet-Regí´s contribution to the field.

Composite Bioinks With Mesoporous Bioactive Glasses-A Critical Evaluation of Results Obtained by In Vitro Experiments

Besides osteoconductivity and a high degradation rate, mesoporous bioactive glasses (MBGs) are specific for their highly ordered channel structure and high specific surface area, making them suitable as drug and/or growth factor delivery systems. On the other hand, the mesoporous channel structure and MBG composition can have an effect on common cell evaluation assays, leading to inconclusive results. This effect is especially important when MBG is mixed in composite bioinks, together with cells. Additionally, the hydrogel component of the ink can influence the degradation of MBG, leading to different ion releases, which can additionally affect the analyses. Hence, our aim here was to show how the MBG structure and composition influence common cell viability and differentiation assays when calcium (Ca)- or magnesium (Mg)-containing glass is part of an alginate-based composite bioink. We suggested pre-labeling of cells with DiI prior to bioprinting and staining with calcein-AM to allow identification of metabolically active cells expressing signals in both green and red channels, allowing the use of fluorescence imaging for cell viability evaluations in the presence of high amounts (7 wt %) of MBGs. The release and uptake of ions during degradation of CaMBG and MgMBG were significantly changed by alginate in the composite bioinks, as confirmed by higher release and uptake from bulk glasses. Additionally, we detected a burst release of Mg2+ from composites only after 24 h of incubation. Furthermore, we demonstrated that released ions and the mesoporous channel structure affect the measurement of lactate dehydrogenase (LDH) and alkaline phosphatase activity (ALP) in bioprinted composite scaffolds. Measured LDH activity was significantly decreased in the presence of CaMBG. On the other hand, the presence of MgMBG induced increased signal measured for the ALP. Taken together, our findings show how composite bioinks containing MBGs can interfere with common analyses, obtaining misleading results.

A versatile multicomponent mesoporous silica nanosystem with dual antimicrobial and osteogenic effects

In this manuscript, we propose a simple and versatile methodology to design nanosystems based on biocompatible and multicomponent mesoporous silica nanoparticles (MSNs) for infection management. This strategy relies on the combination of antibiotic molecules and antimicrobial metal ions into the same nanosystem, affording a significant improvement of the antibiofilm effect compared to that of nanosystems carrying only one of these agents. The multicomponent nanosystem is based on MSNs externally functionalized with a polyamine dendrimer (MSN-G3) that favors internalization inside the bacteria and allows the complexation of multiactive metal ions (MSN-G3-Mⁿ⁺). Importantly, the selection of both the antibiotic and the cation may be done depending on clinical needs. Herein, levofloxacin and Zn²⁺ ion, chosen owing to both its antimicrobial and osteogenic capability, have been incorporated. This dual biological role of Zn²⁺ could have and adjuvant effect thought destroying the biofilm in combination with the antibiotic as well as aid to the repair and regeneration of lost bone tissue associated to osteolysis during infection process. The versatility of the nanosystem has been demonstrated incorporating Ag⁺ ions in a reference nanosystem. In vitro antimicrobial assays in planktonic and biofilm state show a high antimicrobial efficacy due to the combined action of levofloxacin and Zn²⁺, achieving an antimicrobial efficacy above 99% compared to the MSNs containing only one of the microbicide agents. In vitro cell cultures with MC3T3-E1 preosteoblasts reveal the osteogenic capability of the nanosystem, showing a positive effect on osteoblastic differentiation while preserving the cell viability. STATEMENT OF SIGNIFICANCE: A simple and versatile methodology to design biocompatible and multicomponent MSNs based nanosystems for infection management is proposed. These nanosystems, containing two antimicrobial agents, levofloxacin and Zn²⁺, have been synthetized by external functionalization of MSNs with a polycationic dendrimer (MSNs-G3), which favours its internalization inside the bacteria and lead the complexation with metal ions through the amines of the dendrimer. The nanosystems offer a notable improvement of the antibiofilm effect (above 99%) than both components separately as well as osteogenic capability with positive effect on the osteoblastic differentiation and preserved cell viability.

Design of 3D Scaffolds for Hard Tissue Engineering: From Apatites to Silicon Mesoporous Materials

Advanced bioceramics for bone regeneration constitutes one of the pivotal interests in the multidisciplinary and far-sighted scientific trajectory of Prof. Vallet Regí. The different pathologies that affect osseous tissue substitution are considered to be one of the most important challenges from the health, social and economic point of view. 3D scaffolds based on bioceramics that mimic the composition, environment, microstructure and pore architecture of hard tissues is a consolidated response to such concerns. This review describes not only the different types of materials utilized: from apatite-type to silicon mesoporous materials, but also the fabrication techniques employed to design and adequate microstructure, a hierarchical porosity (from nano to macro scale), a cell-friendly surface; the inclusion of different type of biomolecules, drugs or cells within these scaffolds and the influence on their successful performance is thoughtfully reviewed.

Multi-functional silica-based mesoporous materials for simultaneous delivery of biologically active ions and therapeutic biomolecules

Mesoporous silica-based materials, especially mesoporous bioactive glasses (MBGs), are being highly considered for biomedical applications, including drug delivery and tissue engineering, not only because of their bioactivity and biocompatibility but also due to their tunable composition and potential use as drug delivery carriers owing to their controllable nanoporous structure. Numerous researches have reported that MBGs can be doped with various therapeutic ions (strontium, copper, magnesium, zinc, lithium, silver, etc.) and loaded with specific biomolecules (e.g., therapeutic drugs, antibiotics, growth factors) achieving controllable loading and release kinetics. Therefore, co-delivery of ions and biomolecules using a single MBG carrier is highly interesting as this approach provides synergistic effects toward improved therapeutic outcomes in comparison to the strategy of sole drug or ion delivery. In this review, we discuss the state-of-the-art in the field of mesoporous silica-based materials used for co-delivery of ions and therapeutic drugs with osteogenesis/cementogenesis, angiogenesis, antibacterial and anticancer properties. The analysis of the literature reveals that specially designed mesoporous nanocarriers can release multiple ions and drugs at therapeutically safe and relevant levels, achieving the desired biological effects (in vivo, in vitro) for specific biomedical applications. It is expected that this review on the ion/drug co-delivery concept using MBG carriers will shed light on the advantages of such co-delivery systems for clinical use. Areas for future research directions are identified and discussed. STATEMENT OF SIGNIFICANCE: Many studies in literature focus on the potential of single drug or ion delivery by mesoporous silica-based materials, exploiting the bioactivity, biocompatibility, tunable composition and controllable nanoporosity of these materials. Recenlty, studies have adopted the "dual-delivery" concept, by designing multi-functional mesoporous silica-based systems which are capable to deliver both biologically active ions and biomolecules (growth factors, drugs) simultaneously in order to achieve synergy of their complementary therapeutic activities. This review summarizes the state of the art in the field, with focus on osteogenesis/cementogenesis, angiogenesis, antibacterial and anticancer properties, and discusses the challenges and prospects for further progress in this area, expecting to generate broader interest in the technology for applications in disease treatment and regenerative medicine.

Bioactive glass: A multifunctional delivery system

Bioactive glasses (BAGs) were invented five decades ago and have been widely used clinically in orthopedic and stomatology. However, in the past two decades, BAGs have been explored immensely by several researchers worldwide as a multifunctional delivery system for a multitude of therapeutics ranging from metal ions to small molecules (e.g., drugs) and macromolecules (e.g., DNA). The impetus for devising a BAG-based delivery system in the 21st century is based upon the facilitative properties it offers for entrapment of a wide range of therapeutic molecules and the tailorable controlled release kinetics to the target tissue site along with the biological activity of the ionic dissolution products in several pathological conditions such as osteoporosis, cancer, infection, and inflammation. This review comprises two parts: the first part discusses the need for a new delivery system and how the journey from melt quench progressed towards template-based sol-gel mesoporous. In the second part, we have comprehended the scientific advancements made so far, emphasizing BAGs as a delivery system ranging from therapeutic ions to phytopharmaceuticals. We have also highlighted a few loopholes that have prevented bench-to-bedside clinical translation of a plethora of elucidative researches done so far.

Mesoporous bioactive glasses for regenerative medicine

Stem cells are the central element of regenerative medicine (RM). However, in many clinical applications, the use of scaffolds fabricated with biomaterials is required. In this sense, mesoporous bioactive glasses (MBGs) are going to play an important role in bone regeneration because of their striking textural properties, quick bioactive response, and biocompatibility. As other bioactive glasses, MBGs are mainly formed by silicon, calcium, and phosphorus oxides whose ions play an important role in cell proliferation as well as in homeostasis and bone remodeling process. A common improvement of bioactive glasses for RM is by adding small amounts of oxides of elements that confer them additional biological capacities, including osteogenic, angiogenic, antibacterial, anti-inflammatory, hemostatic, or anticancer properties. Moreover, MBGs are versatile in terms of the different ways in which they can be processed, such as scaffolds, fibers, coatings, or nanoparticles. MBGs are unique because their textural properties are so high that they still exhibit outstanding bioactive responses even after adding extra inorganic ions or being processed as scaffolds or nanoparticles. Moreover, they can be further improved by loading with biomolecules, drugs, and stem cells. This article reviews the state of the art and future perspectives of MBGs in the field of RM of hard tissues.

Multifunctional Scaffolds and Synergistic Strategies in Tissue Engineering and Regenerative Medicine

The increasing demand for organ replacements in a growing world with an aging population as well as the loss of tissues and organs due to congenital defects, trauma and diseases has resulted in rapidly evolving new approaches for tissue engineering and regenerative medicine (TERM). The extracellular matrix (ECM) is a crucial component in tissues and organs that surrounds and acts as a physical environment for cells. Thus, ECM has become a model guide for the design and fabrication of scaffolds and biomaterials in TERM. However, the fabrication of a tissue/organ replacement or its regeneration is a very complex process and often requires the combination of several strategies such as the development of scaffolds with multiple functionalities and the simultaneous delivery of growth factors, biochemical signals, cells, genes, immunomodulatory agents, and external stimuli. Although the development of multifunctional scaffolds and biomaterials is one of the most studied approaches for TERM, all these strategies can be combined among them to develop novel synergistic approaches for tissue regeneration. In this review we discuss recent advances in which multifunctional scaffolds alone or combined with other strategies have been employed for TERM purposes.

Tailorable Zinc-Substituted Mesoporous Bioactive Glass/Alginate-Methylcellulose Composite Bioinks

Bioactive glasses have been used for bone regeneration applications thanks to their excellent osteoconductivity, an osteostimulatory effect, and high degradation rate, releasing biologically active ions. Besides these properties, mesoporous bioactive glasses (MBG) are specific for their highly ordered mesoporous channel structure and high specific surface area, making them suitable for drug and growth factor delivery. In the present study, calcium (Ca) (15 mol%) in MBG was partially and fully substituted with zinc (Zn), known for its osteogenic and antimicrobial properties. Different MBG were synthesized, containing 0, 5, 10, or 15 mol% of Zn. Up to 7 wt.% of Zn-containing MBG could be mixed into an alginate-methylcellulose blend (algMC) while maintaining rheological properties suitable for 3D printing of scaffolds with sufficient shape fidelity. The suitability of these composites for bioprinting applications has been demonstrated with immortalized human mesenchymal stem cells. Uptake of Ca and phosphorus (P) (phosphate) ions by composite scaffolds was observed, while the released concentration of Zn2+ corresponded to the initial amount of this ion in prepared glasses, suggesting that it can be controlled at the MBG synthesis step. The study introduces a tailorable bioprintable material system suitable for bone tissue engineering applications.

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.