Molecular gates in mesoporous bioactive glasses for the treatment of bone tumors and infection

Innovative Biomaterials for Bone Tumor Treatment and Regeneration: Tackling Postoperative Challenges and Charting the Path Forward

Surgical resection of bone tumors is the primary approach employed in the treatment of bone cancer. Simultaneously, perioperative interventions, particularly postoperative adjuvant anticancer strategies, play a crucial role in achieving satisfactory therapeutic outcomes. However, the occurrence of postoperative bone tumor recurrence, metastasis, extensive bone defects, and infection are significant risks that can result in unfavorable prognoses or even treatment failure. In recent years, there has been significant progress in the development of biomaterials, leading to the emergence of new treatment options for bone tumor therapy and bone regeneration. This progress report aims to comprehensively analyze the strategic development of unique therapeutic biomaterials with inherent healing properties and bioactive capabilities for bone tissue regeneration. These composite biomaterials, classified into metallic, inorganic non-metallic, and organic types, are thoroughly investigated for their responses to external stimuli such as light or magnetic fields, internal interventions including chemotherapy or catalytic therapy, and combination therapy, as well as their role in bone regeneration. Additionally, an overview of self-healing materials for osteogenesis is provided and their potential applications in combating osteosarcoma and promoting bone formation are explored. Furthermore, the safety concerns of integrated materials and current limitations are addressed, while also discussing the challenges and future prospects.

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.

Nanostructured bioactive glasses: A bird's eye view on cancer therapy

Bioactive glasses (BGs) arewell known for their successful applications in tissue engineering and regenerative medicine. Recent experimental studies have shown their potential usability in oncology, either alone or in combination with other biocompatible materials, such as biopolymers. Direct contact with BG particles has been found to cause toxicity and death in specific cancer cells (bone-derived neoplastic stromal cells) in vitro. Nanostructured BGs (NBGs) can be doped with anticancer elements, such as gallium, to enhance their toxic effects against tumor cells. However, the molecular mechanisms and intracellular targets for anticancer compositions of NBGs require further clarification. NBGs have been successfully evaluated for use in various well-established cancer treatment strategies, including cancer hyperthermia, phototherapy, and anticancer drug delivery. Existing results indicate that NBGs not only enhance cancer cell death, but can also participate in the regeneration of lost healthy tissues. However, the application of NBGs in oncology is still in its early stages, and numerous unanswered questions must be addressed. For example, the impact of the composition, biodegradation, size, and morphology of NBGs on their anticancer efficacy should be defined for each type of cancer and treatment strategy. Moreover, it should be more clearly assessed whether NBGs can shrink tumors, slow/stop cancer progression, or cure cancer completely. In this regard, the use of computational studies (in silico methods) is highly recommended to design the most effective glass formulations for cancer therapy approaches and to predict, to some extent, the relevant properties, efficacy, and outcomes. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Development of Photonic Multi-Sensing Systems Based on Molecular Gates Biorecognition and Plasmonic Sensors: The PHOTONGATE Project

This paper presents the concept of a novel adaptable sensing solution currently being developed under the EU Commission-founded PHOTONGATE project. This concept will allow for the quantification of multiple analytes of the same or different nature (chemicals, metals, bacteria, etc.) in a single test with levels of sensitivity and selectivity at/or over those offered by current solutions. PHOTONGATE relies on two core technologies: a biochemical technology (molecular gates), which will confer the specificity and, therefore, the capability to be adaptable to the analyte of interest, and which, combined with porous substrates, will increase the sensitivity, and a photonic technology based on localized surface plasmonic resonance (LSPR) structures that serve as transducers for light interaction. Both technologies are in the micron range, facilitating the integration of multiple sensors within a small area (mm2). The concept will be developed for its application in health diagnosis and food safety sectors. It is thought of as an easy-to-use modular concept, which will consist of the sensing module, mainly of a microfluidics cartridge that will house the photonic sensor, and a platform for fluidic handling, optical interrogation, and signal processing. The platform will include a new optical concept, which is fully European Union Made, avoiding optical fibers and expensive optical components.

Delivery of miR-200c-3p Using Tumor-Targeted Mesoporous Silica Nanoparticles for Breast Cancer Therapy

Despite advances in breast cancer treatment, it remains the leading cause of cancer-related death in women worldwide. In this context, microRNAs have emerged as potential therapeutic targets but still present some limitations for in vivo applications. Particularly, miR-200c-3p is a well-known tumor suppressor microRNA that inhibits tumor progression and metastasis in breast cancer through downregulating ZEB1 and ZEB2. Based on the above, we describe the design and validation of a nanodevice using mesoporous silica nanoparticles for miR-200c-3p delivery for breast cancer treatment. We demonstrate the biocompatibility of the synthesized nanodevices as well as their ability to escape from endosomes/lysosomes and inhibit tumorigenesis, invasion, migration, and proliferation of tumor cells in vitro. Moreover, tumor targeting and effective delivery of miR-200c-3p from the nanoparticles in vivo are confirmed in an orthotopic breast cancer mouse model, and the therapeutic efficacy is also evidenced by a decrease in tumor size and lung metastasis, while showing no signs of toxicity. Overall, our results provide evidence that miR-200c-3p-loaded nanoparticles are a potential strategy for breast cancer therapy and a safe and effective system for tumor-targeted delivery of microRNAs.

Mesoporous Bioactive Nanoparticles for Bone Tissue Applications

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

Bioactive Glasses as Carriers of Cancer-Targeted Drugs: Challenges and Opportunities in Bone Cancer Treatment

The treatment of bone cancer involves tumor resection followed by bone reconstruction of the defect caused by the tumor using biomaterials. Additionally, post-surgery protocols cover chemotherapy, radiotherapy, or drug administration, which are employed as adjuvant treatments to prevent tumor recurrence. In this work, we reviewed new strategies for bone cancer treatment based on bioactive glasses as carriers of cancer-targeted and other drugs that are intended for bone regeneration in conjunction with adjuvant treatments. Drugs used in combination with bioactive glasses can be classified into cancer-target, osteoclast-target, and new therapies (such as gene delivery and bioinorganic). Microparticulated, nanoparticulated, or mesoporous bioactive glasses have been used as drug-delivery systems. Additionally, surface modification through functionalization or the production of composites based on polymers and hydrogels has been employed to improve drug-release kinetics. Overall, although different drugs and drug delivery systems have been developed, there is still room for new studies involving kinase inhibitors or antibody-conjugated drugs, as these drugs have been poorly explored in combination with bioactive glasses.

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.

Clinical and radiological comparison of bioactive glass and poly-L-lactic acid/hydroxyapatite bioabsorbable interference screws for tibial graft fixation in anterior cruciate ligament reconstruction

BACKGROUND

Ligament reconstruction is still the main treatment modality for patients with a complete ligament rupture. The semitendinosus tendon, alone quadrupled or double folded and combined with the gracilis tendon, is still the most frequently used autologous graft for a reconstructive procedure. Absorbable interference screw usage has gained popularity in the past decade because they create less artifacts during MR imaging and tend to osteointegrate over the years, arguably leading to a more anatomic fixation. The purpose of this study was to compare the 5-year radiological and clinical results of two different tibial graft fixation screws.

HYPOTHESIS

We hypothesized that bioabsorbable interference screws made of bioactive glass would lead to higher rates of osteointegration, better overall clinical results, less foreign body reaction rates and less tibial tunnel widening when compared to the poly-L-lactic acid/hydroxyapatite (PLLA-HA) screws.

PATIENTS AND METHODS

Fifty-one patients treated with an anatomic single bundle ACL reconstruction between June 2015 and July 2016 at our institution were included in the study. The tibial graft was fixed with a bioactive glass screw in 24, and with a PLLA-HA in 27 patients. Tibial tunnel widening, foreign body reaction, osteointegration and resorption rates were evaluated and compared on a magnetic resonance scan at a minimum of 5 year postoperatively. Overall clinical results and side-to-side difference on KT-1000 were also analyzed in-between groups.

RESULTS

Tibial tunnel widening was similar for both groups. Foreign body reaction, while not statistically significant, was less aggressive when bioactive glass screws were used. Osteointegration and resorption rates of the bioactive glass screws were significantly higher than the PLLA-HA group (p=0.000). While all patients showed an overall improvement on postoperative scores (p=0.000), patients with a bioactive glass interference screw had statistically higher translational stability with KT-1000, compared to the poly-L-lactic acid/hydroxyapatite group (p=0.001).

DISCUSSION

At a minimum of 5 years, compared to conventional PLLA-HA interference screws, 45S5 bioactive glass screw provide higher resorption rates, are more highly biodegradable and provide overall good clinical results.

LEVEL OF EVIDENCE

III.

Fluorogenic Detection of Human Serum Albumin Using Curcumin-Capped Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles loaded with rhodamine B and capped with curcumin are used for the selective and sensitive fluorogenic detection of human serum albumin (HSA). The sensing mesoporous silica nanoparticles are loaded with rhodamine B, decorated with aminopropyl moieties and capped with curcumin. The nanoparticles selectively release the rhodamine B cargo in the presence of HSA. A limit of detection for HSA of 0.1 mg/mL in PBS (pH 7.4)-acetonitrile 95:5 v/v was found, and the sensing nanoparticles were used to detect HSA in spiked synthetic urine samples.

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.

Arabic gum plus colistin coated moxifloxacin-loaded nanoparticles for the treatment of bone infection caused by Escherichia coli

Osteomyelitis is an inflammatory process of bone and bone marrow that may even lead to patient death. Even though this disease is mainly caused by Gram-positive organisms, the proportion of bone infections caused by Gram-negative bacteria, such as Escherichia coli, has significantly increased in recent years. In this work, mesoporous silica nanoparticles have been employed as platform to engineer a nanomedicine able to eradicate E. coli- related bone infections. For that purpose, the nanoparticles have been loaded with moxifloxacin and further functionalized with Arabic gum and colistin (AG+CO-coated MX-loaded MSNs). The nanosystem demonstrated high affinity toward E. coli biofilm matrix, thanks to AG coating, and marked antibacterial effect because of the bactericidal effect of moxifloxacin and the disaggregating effect of colistin. AG+CO-coated MX-loaded MSNs were able to eradicate the infection developed on a trabecular bone in vitro and showed pronounced antibacterial efficacy in vivo against an osteomyelitis provoked by E. coli. Furthermore, AG+CO-coated MX-loaded MSNs were shown to be essentially non-cytotoxic with only slight effect on cell proliferation and mild hepatotoxicity, which might be attributed to the nature of both antibiotics. In view of these results, these nanoparticles may be considered as a promising treatment for bone infections caused by enterobacteria, such as E. coli, and introduce a general strategy against bone infections based on the implementation of antibiotics with different but complementary activity into a single nanocarrier. STATEMENT OF SIGNIFICANCE: In this work, we propose a methodology to address E.coli bone infections by using moxifloxacin-loaded mesoporous silica nanoparticles coated with Arabic gum containing colistin (AG+CO-coated MX-loaded MSNs). The in vitro evaluation of this nanosystem demonstrated high affinity toward E. coli biofilm matrix thanks to the Arabic gum coating, a disaggregating and antibacterial effect of colistin, and a remarkable antibiofilm action because of the bactericidal ability of moxifloxacin and colistin. This anti-E. coli capacity of AG+CO-coated MX-loaded MSNs was brought out in an in vivo rabbit model of osteomyelitis where the nanosystem was able to eradicate more than 90% of the bacterial load within the infected bone.

Mesoporous Bioactive Glasses in Cancer Diagnosis and Therapy: Stimuli-Responsive, Toxicity, Immunogenicity, and Clinical Translation

Cancer is one of the top life-threatening dangers to the human survival, accounting for over 10 million deaths per year. Bioactive glasses have developed dramatically since their discovery 50 years ago, with applications that include therapeutics as well as diagnostics. A new system within the bioactive glass family, mesoporous bioactive glasses (MBGs), has evolved into a multifunctional platform, thanks to MBGs easy-to-functionalize nature and tailorable textural properties-surface area, pore size, and pore volume. Although MBGs have yet to meet their potential in tumor treatment and imaging in practice, recently research has shed light on the distinguished MBGs capabilities as promising theranostic systems for cancer imaging and therapy. This review presents research progress in the field of MBG applications in cancer diagnosis and therapy, including synthesis of MBGs, mechanistic overview of MBGs application in tumor diagnosis and drug monitoring, applications of MBGs in cancer therapy ( particularly, targeted delivery and stimuli-responsive nanoplatforms), and immunological profile of MBG-based nanodevices in reference to the development of novel cancer therapeutics.

Effective Actions of Ion Release from Mesoporous Bioactive Glass and Macrophage Mediators on the Differentiation of Osteoprogenitor and Endothelial Progenitor Cells

Due to their specific mesoporous structure and large surface area, mesoporous bioactive glasses (MBGs) possess both drug-delivery ability and effective ionic release to promote bone regeneration by stimulating osteogenesis and angiogenesis. Macrophages secrete mediators that can affect both processes, depending on their phenotype. In this work, the action of ion release from MBG-75S, with a molar composition of 75SiO2-20CaO-5P2O5, on osteogenesis and angiogenesis and the modulatory role of macrophages have been assessed in vitro with MC3T3-E1 pre-osteoblasts and endothelial progenitor cells (EPCs) in monoculture and in coculture with RAW 264.7 macrophages. Ca2+, phosphorous, and silicon ions released from MBG-75S were measured in the culture medium during both differentiation processes. Alkaline phosphatase activity and matrix mineralization were quantified as the key markers of osteogenic differentiation in MC3T3-E1 cells. The expression of CD31, CD34, VEGFR2, eNOS, and vWF was evaluated to characterize the EPC differentiation into mature endothelial cells. Other cellular parameters analyzed included the cell size and complexity, intracellular calcium, and intracellular content of the reactive oxygen species. The results obtained indicate that the ions released by MBG-75S promote osteogenesis and angiogenesis in vitro, evidencing a macrophage inhibitory role in these processes and demonstrating the high potential of MBG-75S for the preparation of implants for bone regeneration.

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.

The immunogenic reaction and bone defect repair function of ε-poly-L-lysine (EPL)-coated nanoscale PCL/HA scaffold in rabbit calvarial bone defect

Tissue engineering is a promising strategy for bone tissue defect reconstruction. Immunogenic reaction, which was induced by scaffolds degradation or contaminating microorganism, influence cellular activity, compromise the efficiency of tissue engineering, or eventually lead to the failure of regeneration. Inhibiting excessive immune response through modulating scaffold is critical important to promote tissue regeneration. Our previous study showed that ε-poly-L-lysine (EPL)-coated nanoscale polycaprolactone/hydroxyapatite (EPL/PCL/HA) composite scaffold has enhanced antibacterial and osteogenic properties in vitro. However, the bone defect repair function and immunogenic reaction of EPL/PCL/HA scaffolds in vivo remains unclear. In the present study, three nanoscale scaffolds (EPL/PCL/HA, PCL and PCL/HA) were transplanted into rabbit paraspinal muscle pouches, and T helper type 1 (Th1), T helper type 2 (Th2), T helper type 17 (Th17), and macrophage infiltration were analyzed after 1 week and 2 weeks to detect their immunogenic reaction. Then, the different scaffolds were transplanted into rabbit calvarial bone defect to compare the bone defect repair capacities. The results showed that EPL/PCL/HA composite scaffolds decreased pro-inflammatory Th1, Th17, and type I macrophage infiltration from 1 to 2 weeks, and increased anti-inflammatory Th2 infiltration into the regenerated area at 2 weeks in vivo, when compared to PCL and PCL/HA. In addition, EPL/PCL/HA showed an enhanced bone repair capacity compared to PCL and PCL/HA when transplanted into rabbit calvarial bone defects at both 4 and 8 weeks. Hence, our results suggest that EPL could regulate the immunogenic reaction and promote bone defect repair function of PCL/HA, which is a promising agent for tissue engineering scaffold modulation.

Gene-Directed Enzyme Prodrug Therapy by Dendrimer-Like Mesoporous Silica Nanoparticles against Tumor Cells

We report herein a gene-directed enzyme prodrug therapy (GDEPT) system using gated mesoporous silica nanoparticles (MSNs) in an attempt to combine the reduction of side effects characteristic of GDEPT with improved pharmacokinetics promoted by gated MSNs. The system consists of the transfection of cancer cells with a plasmid controlled by the cytomegalovirus promoter, which promotes β-galactosidase (β-gal) expression from the bacterial gene lacZ (CMV-lacZ). Moreover, dendrimer-like mesoporous silica nanoparticles (DMSNs) are loaded with the prodrug doxorubicin modified with a galactose unit through a self-immolative group (DOXO-Gal) and modified with a disulfide-containing polyethyleneglycol gatekeeper. Once in tumor cells, the reducing environment induces disulfide bond rupture in the gatekeeper with the subsequent DOXO-Gal delivery, which is enzymatically converted by β-gal into the cytotoxic doxorubicin drug, causing cell death. The combined treatment of the pair enzyme/DMSNs-prodrug are more effective in killing cells than the free prodrug DOXO-Gal alone in cells transfected with β-gal.

pH-Dependent Molecular Gate Mesoporous Microparticles for Biological Control of Giardia intestinalis

Giardiasis is a parasitism produced by the protozoa Giardia intestinalis that lives as trophozoite in the small intestine (mainly in the duodenum) attached to the intestinal villus by means of billed discs. The first line treatment is metronidazole, a drug with high bioavailability, which is why to obtain therapeutic concentrations in duodenum, it is necessary to administer high doses of drug to patients with the consequent occurrence of side effects. It is necessary to developed new therapeutical approaches to achieve a local delivery of the drug. In this sense, we have developed gated mesoporous silica microparticles loaded with metronidazole and with a molecular gate pH dependent. In vitro assays demonstrated that the metronidazole release is practically insignificant at acidic pHs, but in duodenum conditions, the metronidazole delivery from the microparticles is effective enough to produce an important parasite destruction. In vivo assays indicate that this microparticulate system allows to increase the concentration of the drug in duodenum and reduce the concentration in plasma avoiding systemic effects. This system could be useful for other intestinal local treatments in order to reduce doses and increase drug availability in target tissues.

An Evolution of Shoulder Periprosthetic Infections Management: MicroDTTect, Bioactive Glass and Tantalum Cones Employment

Periprosthetic joint infections of the shoulder (PJIS) are the major cause for revision within the first two post-operative years, and are challenging both to diagnose and treat. Success depends on early identification of microorganisms, appropriate surgical procedures and efficient antibiotic administration. The peculiar microbiology of the shoulder may render the criteria for hip/knee PJI management inappropriate. In addition, later cases with clinically subtle signs often present diagnostic challenges. In recent years, specific issues of PJIS have been managed through the use of new instruments, such as MicroDTTect in pathogen detection and Bioactive Glass and tantalum cones in humeral bone loss. In the literature to date, no reports have been found that discuss the application in shoulder revisions and infections. The early identification of the microorganisms that cause infection may help improve both treatment strategies and the efficacy of therapy. MicroDTTect proved to be more efficient than swab collection for bacterial identification in orthopedic surgery, thus reducing analysis costs. The increasing number of shoulder arthroplasties is associated with an increase in the number of revisions. In cases of massive metaphyseal humeral bone loss, several techniques have been described; no reports have been reported regarding tantalum in humeral bone loss management. In some cases the tantalum cones required adaptation for femoral diaphysis in the augmentation of the humerus metaphysis and bone loss management improvement. Obtaining stable osseointegration of prosthetic implants is one of the greatest issues in orthopedic surgery, and even more crucial in revisions. Bioactive glasses demonstrated good regenerative and osseointegration properties, and an excellent candidate as a bone graft, scaffold and antibiotics deliverer. The Bioactive glasses were used to increase prosthesis-bone interface stability and fill bone defects in PJIS revision surgeries, contributing to the prevention of re-infection. Longer-term follow-up will be necessary to determine if construction durability is improved in the long term.

Biomaterials against Bone Infection

Chronic bone infection is considered as one of the most problematic biofilm-related infections. Its recurrent and resistant nature, high morbidity, prolonged hospitalization, and costly medical care expenses have driven the efforts of the scientific community to develop new therapies to improve the standards used today. There is great debate on the management of this kind of infection in order to establish consistent and agreed guidelines in national health systems. The scientific research is oriented toward the design of anti-infective biomaterials both for prevention and cure. The properties of these materials must be adapted to achieve better anti-infective performance and good compatibility, which allow a good integration of the implant with the surrounding tissue. The objective of this review is to study in-depth the antibacterial biomaterials and the strategies underlying them. In this sense, this manuscript focuses on antimicrobial coatings, including the new technological advances on surface modification; scaffolding design including multifunctional scaffolds with both antimicrobial and bone regeneration properties; and nanocarriers based on mesoporous silica nanoparticles with advanced properties (targeting and stimuli-response capabilities).

Influence of the Surface Functionalization on the Fate and Performance of Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles have been broadly applied as drug delivery systems owing to their exquisite features, such as excellent textural properties or biocompatibility. However, there are various biological barriers that prevent their proper translation into the clinic, including: (1) lack of selectivity toward tumor tissues, (2) lack of selectivity for tumoral cells and (3) endosomal sequestration of the particles upon internalization. In addition, their open porous structure may lead to premature drug release, consequently affecting healthy tissues and decreasing the efficacy of the treatment. First, this review will provide a comprehensive and systematic overview of the different approximations that have been implemented into mesoporous silica nanoparticles to overcome each of such biological barriers. Afterward, the potential premature and non-specific drug release from these mesoporous nanocarriers will be addressed by introducing the concept of stimuli-responsive gatekeepers, which endow the particles with on-demand and localized drug delivery.

Mesoporous Silica Nanoparticles for the Treatment of Complex Bone Diseases: Bone Cancer, Bone Infection and Osteoporosis

Bone diseases, such as bone cancer, bone infection and osteoporosis, constitute a major issue for modern societies as a consequence of their progressive ageing. Even though these pathologies can be currently treated in the clinic, some of those treatments present drawbacks that may lead to severe complications. For instance, chemotherapy lacks great tumor tissue selectivity, affecting healthy and diseased tissues. In addition, the inappropriate use of antimicrobials is leading to the appearance of drug-resistant bacteria and persistent biofilms, rendering current antibiotics useless. Furthermore, current antiosteoporotic treatments present many side effects as a consequence of their poor bioavailability and the need to use higher doses. In view of the existing evidence, the encapsulation and selective delivery to the diseased tissues of the different therapeutic compounds seem highly convenient. In this sense, silica-based mesoporous nanoparticles offer great loading capacity within their pores, the possibility of modifying the surface to target the particles to the malignant areas and great biocompatibility. This manuscript is intended to be a comprehensive review of the available literature on complex bone diseases treated with silica-based mesoporous nanoparticles-the further development of which and eventual translation into the clinic could bring significant benefits for our future society.

Mesoporous bioactive glass/ɛ-polycaprolactone scaffolds promote bone regeneration in osteoporotic sheep

Macroporous scaffolds made of a SiO2-CaO-P2O5 mesoporous bioactive glass (MBG) and ɛ-polycaprolactone (PCL) have been prepared by robocasting. These scaffolds showed an excellent in vitro biocompatibility in contact with osteoblast like cells (Saos 2) and osteoclasts derived from RAW 264.7 macrophages. In vivo studies were carried out by implantation into cavitary defects drilled in osteoporotic sheep. The scaffolds evidenced excellent bone regeneration properties, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, thick trabeculae, high vascularization and high presence of osteoblasts and osteoclasts. In order to evaluate the effects of the local release of an antiosteoporotic drug, 1% (%wt) of zoledronic acid was incorporated to the scaffolds. The scaffolds loaded with zoledronic acid induced apoptosis in Saos 2 cells, impeded osteoclast differentiation in a time dependent manner and inhibited bone healing, promoting an intense inflammatory response in osteoporotic sheep. STATEMENT OF SIGNIFICANCE: In addition to an increase in bone fragility and susceptibility to fracture, osteoporosis also hinders the clinical success of endosseous implants and grafting materials for the treatment of bone defects. For the first time, macroporous scaffolds made of mesoporous bioactive glass and ε-caprolactone have been evaluated in a sheep model that mimics the osteoporosis conditions in humans. These implants fostered bone regeneration, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, showing thick trabeculae and a high vascularization degree. Our results indicate that macroporous structures containing highly bioactive mesoporous glasses could be excellent candidates for the regenerative treatment of bone defects in osteoporotic patients.

Recent advances in functional nanostructured materials for bone-related diseases

Bone-related diseases seriously threaten people's health and research studies have been dedicated towards searching for new and effective treatment methods. Nanotechnologies have opened up a new field in recent decades and nanostructured materials, which exist in a variety of forms, are considered to be promising materials in this field. This article reviews the most recent progress in the development of nanostructured materials for bone-related diseases, including osteoporosis, osteoarthritis, bone metastasis, osteomyelitis, myeloma, and bone defects. We highlight the advantages and functions of nanostructured materials, including sustained release, bone targeting, scaffolding in bone tissue engineering, etc., in bone-related diseases. We also include the remaining challenges of these emerging materials.

Well-ordered mesoporous silica and bioactive glasses: promise for improved hemostasis

Mesoporous silica and bioactive glasses with unique textural properties are new generations of inorganic hemostats with efficient hemostatic ability.

Mesoporous Silica Materials as Drug Delivery: "The Nightmare" of Bacterial Infection

Mesoporous silica materials (MSM) have a great surface area and a high pore volume, meaning that they consequently have a large loading capacity, and have been demonstrated to be unique candidates for the treatment of different pathologies, including bacterial infection. In this text, we review the multiple ways of action in which MSM can be used to fight bacterial infection, including early detection, drug release, targeting bacteria or biofilm, antifouling surfaces, and adjuvant capacity. This review focus mainly on those that act as a drug delivery system, and therefore that have an essential characteristic, which is their great loading capacity. Since MSM have advantages in all stages of combatting bacterial infection; its prevention, detection and finally in its treatment, we can venture to talk about them as the "nightmare of bacteria".

Mesoporous Bioactive Glasses Equipped with Stimuli-Responsive Molecular Gates for Controlled Delivery of Levofloxacin against Bacteria

An increase of bone diseases incidence has boosted the study of ceramic biomaterials as potential osteo-inductive scaffolds. In particular, mesoporous bioactive glasses have demonstrated to possess a broad application in the bone regeneration field, due their osteo-regenerative capability and their ability to release drugs from the mesoporous structure. These special features have been studied as an option to fight against bone infection, which is one of the most common problems regarding bone regeneration therapies. In this work, a mesoporous bioglass functionalized with polyamines and capped with adenosine triphosphate (ATP) as the molecular gate was developed for the controlled release of the antibiotic levofloxacin. Phosphate bonds of ATP were hydrolyzed in the presence of acid phosphatase (APase), the concentration of which is significantly increased in bone infection due to the activation of bone resorption processes. The solid was characterized and tested successfully against bacteria. The final gated solid induced bacterial death only in the presence of acid phosphatase. Additionally, it was demonstrated that the solid is not toxic against human cells. The double function of the prepared material as a drug delivery system and bone regeneration enhancer confirms the possible development of a new approach in the tissue engineering field, in which controlled release of therapeutic agents can be finely tuned and, at the same time, osteoinduction is favored.

Mesoporous bioactive glasses: Promising platforms for antibacterial strategies

The control of bacterial infections is of particular importance in the field of tissue engineering. Recently, much attention has been addressed toward the use of mesoporous bioactive glasses (MBGs) for antibacterial strategies, primarily because of their capability of acting as carriers for the local release of antimicrobial agents. The incorporation of antibacterial metallic ions including silver (Ag⁺), zinc (Zn²⁺), copper (Cu⁺ and Cu²⁺), cerium (Ce³⁺ and Ce⁴⁺), and gallium (Ga³⁺) cations into the MBG structure and their controlled release is proposed as one of the most attractive strategies for inhibiting bacterial growth and reproduction. Moreover, the possibility of loading and delivering various antibacterial biomolecules (e.g., antibiotics) through the porous structure of MBGs makes them as ideal candidates for antibacterial applications. In this review, we aim to present a comprehensive evaluation of MBG potential regarding antibacterial activities. For this purpose, different types of antibacterial ion-doped and drug-loaded MBGs are introduced and discussed in the light of existing knowledge, along with the significant challenges ahead. STATEMENT OF SIGNIFICANCE: Prevention and treatment of infections is one of the today's greatest challenges in medical sciences, also considering the well-known issues related to increased bacterial resistance to antibiotics. The advent of mesoporous glasses led to the birth of a new class of multifunctional biomaterials acting as bioactive platforms for the local release of organic or inorganic agents eliciting an antimicrobial effect. This reviews summarizes the state of the art of MBGs in this field, highlighting the latest evolutions and the specific role played by metallic antimicrobial ions that can be incorporated in the glass composition and then properly released. Perspective for tissue engineering applications are also discussed to provide an up-to-date contribution that is useful to both experienced scientists and early-stage researchers.

Antimicrobial activity of commercial calcium phosphate based materials functionalized with vanillin

Infections represent one of the most frequent causes of arthroplasty revision. Thus, design of new antimicrobial scaffolds to reduce implant rejections, bone infections and associated medical costs is highly desired. In recent years, essential oil components (EOCs) have merged as compounds with significant antimicrobial activity that can be attached to specific surfaces to enhance and prolong their antimicrobial effect. Herein calcium phosphate CaP regenerative materials have been coated with a vanillin derivative to combine its original bone regeneration properties with antimicrobial action of EOCs. Materials in form of microparticles and blocks were prepared and fully characterized. Clonogenic viability tests demonstrated that low concentrations of material (10 mg·mL^-1) resulted effective to kill 100% of E. coli DH5α bacteria. Additionally, vanillin containing scaffolds did not display any toxic effect over cells, yet they preserve the ability to express alkaline phosphatase (ALPL), collagen type 1, chain α1 (COL1A1) and bone gamma-carboxyglutamic acid-containing protein or osteocalcin (BGLAP), which are genes typically expressed by osteoblasts. These results demonstrate that commercially available scaffolds can be functionalized with EOCs, achieving antimicrobial activity and open up a new approach for the treatment and prevention of infection. STATEMENT OF SIGNIFICANCE: During the last years, the interest in bone regenerative materials with antibiotic properties has increased, since prosthesis infection is one of the most usual complications in implant surgery. In this work, we report a hybrid system composed by a calcium phosphate material (powders and scaffolds) functionalized with the derivative of an essential oil component (EOC). Our purpose was to provide the calcium phosphate material with antimicrobial activity without harming its bone regenerative capability. The obtained results were encouraging, which opens up the possibility of developing new modified materials for the prevention and treatment of bone infection.

The response of pre-osteoblasts and osteoclasts to gallium containing mesoporous bioactive glasses

Mesoporous bioactive glasses (MBGs) in the system SiO₂-CaO-P₂O₅-Ga₂O₃ have been synthesized by the evaporation induced self-assembly method and subsequent impregnation with Ga cations. Two different compositions have been prepared and the local environment of Ga(III) has been characterized using ²⁹Si, ⁷¹Ga and ³¹P NMR analysis, demonstrating that Ga(III) is efficiently incorporated as both, network former (GaO₄ units) and network modifier (GaO₆ units). In vitro bioactivity tests evidenced that Ga-containing MBGs retain their capability for nucleation and growth of an apatite-like layer in contact with a simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Finally, in vitro cell culture tests evidenced that Ga incorporation results in a selective effect on osteoblasts and osteoclasts. Indeed, the presence of this element enhances the early differentiation towards osteoblast phenotype while disturbing osteoclastogenesis. Considering these results, Ga-doped MBGs might be proposed as bone substitutes, especially in osteoporosis scenarios.

STATEMENT OF SIGNIFCANCE

Osteoporosis is the most prevalent bone disease affecting millions of patients every year. However, there is a lack of bone grafts specifically designed for the treatment of bone defects occurred because of osteoporotic fractures. The consequence is that osteoporotic bone defects are commonly treated with the same biomaterials intended for high quality bone tissue. In this work we have prepared mesoporous bioactive glasses doped with gallium, demonstrating osteoinductive capability by promoting the differentiation of pre-osteoblast toward osteoblasts and partial inhibition of osteoclastogenesis. Through a deep study of the local environment of gallium within the mesoporous matrix, this work shows that gallium release is not required to produce this effect on osteoblasts and osteoclasts. In this sense, the presence of this element at the surface of the mesoporous bioactive glasses would be enough to locally promote bone formation while reducing bone resorption.

Smart gated magnetic silica mesoporous particles for targeted colon drug delivery: New approaches for inflammatory bowel diseases treatment

Magnetic mesoporous silica microparticles were loaded with safranin O (S1) and with hydrocortisone (S2) and the outer surface functionalized with a bulky azo derivative bearing urea moieties. Aqueous suspensions of both solids at pH 7.4 showed negligible payload release whereas a marked delivery was observed in the presence of sodium dithionite due to the rupture of the azo bonds. Besides, a moderate cargo release was observed at acidic pH due to the hydrolysis of the urea bonds that linked the azo derivative onto the external surface of the inorganic scaffolds. In vitro digestion models showed that S1 and S2 microparticles could be used for the controlled release of payload in the reducing colon environment (in which azoreductase enzymes are present). On the other hand, in vivo pharmacokinetic studies in rats showed that safranine O release from S1 microparticles was concentrated in colon. The performance of S2 microparticles for the treatment of colitis in rats (induced by oral administration of a 2,4,6-trinitrobenzenesulfonic acid solution) was tested. The controlled release of hydrocortisone from S2 in the colon of injured rats induced marked reduction in colon/body weight ratio and in clinical activity score. Also, histological studies showed a marked decrease in inflammation followed by intensive regeneration and almost normal mucosal structure of the individuals treated with S2. Besides, the use of a magnetic belt increased the therapeutic performances of S2 due to an enhanced retention time of the particles in the colon.

Recent Evidence on Bioactive Glass Antimicrobial and Antibiofilm Activity: A Mini-Review

Bone defects caused by trauma or pathological events are major clinical and socioeconomic burdens. Thus, the efforts of regenerative medicine have been focused on the development of non-biodegradable materials resembling bone features. Consequently, the use of bioactive glass as a promising alternative to inert graft materials has been proposed. Bioactive glass is a synthetic silica-based material with excellent mechanical properties able to bond to the host bone tissue. Indeed, when immersed in physiological fluids, bioactive glass reacts, developing an apatite layer on the granule’s surface, playing a key role in the osteogenesis process. Moreover, the contact of bioactive glass with biological fluids results in the increase of osmotic pressure and pH due to the leaching of ions from granules’ surface, thus making the surrounding environment hostile to microbial growth. The bioactive glass antimicrobial activity is effective against a wide selection of aerobic and anaerobic bacteria, either in planktonic or sessile forms. Furthermore, bioglass is able to reduce pathogens’ biofilm production. For the aforementioned reasons, the use of bioactive glass might be a promising solution for the reconstruction of bone defects, as well as for the treatment and eradication of bone infections, characterized by bone necrosis and destruction of the bone structure.

Magnetic nanoparticles modified-porous scaffolds for bone regeneration and photothermal therapy against tumors

For effectively treating tumor related-bone defects, design and fabrication of multifunctional biomaterials still remain a great challenge. Herein, we firstly fabricated magnetic SrFe₁₂O₁₉ nanoparticles modified-mesoporous bioglass (BG)/chitosan (CS) porous scaffold (MBCS) with excellent bone regeneration and antitumor function. The as-produced magnetic field from MBCS promoted the expression levels of osteogenic-related genes (OCN, COL1, Runx2 and ALP) and the new bone regeneration by activated BMP-2/Smad/Runx2 pathway. Moreover, the SrFe₁₂O₁₉ nanoparticles in MBCS improved the photothermal conversion property. Under the irradiation of near-infrared (NIR) laser, the elevated temperatures of tumors co-cultured with MBCS triggered tumor apoptosis and ablation. As compared with the pure scaffold group, MBCS/NIR group possessed the excellent antitumor efficacy against osteosarcoma via the hyperthermia ablation. Therefore, the multifunctional MBCS with excellent bone regeneration and photothermal therapy functions has a great application for treating the tumor-related bone defects.

Functional Magnetic Mesoporous Silica Microparticles Capped with an Azo-Derivative: A Promising Colon Drug Delivery Device

Magnetic micro-sized mesoporous silica particles were used for the preparation of a gated material able to release an entrapped cargo in the presence of an azo-reducing agent and, to some extent, at acidic pH. The magnetic mesoporous microparticles were loaded with safranin O and the external surface was functionalized with an azo derivative 1 (bearing a carbamate linkage) yielding solid S1. Aqueous suspensions of S1 at pH 7.4 showed negligible safranin O release due to the presence of the bulky azo derivative attached onto the external surface of the inorganic scaffold. However, in the presence of sodium dithionite (azoreductive agent), a remarkable safranin O delivery was observed. At acidic pH, a certain safranin O release from S1 was also found. The pH-triggered safranin O delivery was ascribed to the acid-induced hydrolysis of the carbamate moiety that linked the bulky azo derivatives onto the mesoporous inorganic magnetic support. The controlled release behavior of S1 was also tested using a model that simulated the gastro intestinal tract.

Lectin-gated and glycan functionalized mesoporous silica nanocontainers for targeting cancer cells overexpressing Lewis X antigen

Gated mesoporous silica nanoparticles can deliver payload upon the application of a predefined stimulus, and therefore are promising drug delivery systems. Despite their important role, relatively low emphasis has been placed on the design of gating systems that actively target carbohydrate tumor cell membrane receptors. We describe herein a new Lewis X (Le^x) antigen-targeted delivery system comprising mesoporous silica nanoparticles (MSNs) loaded with ATTO 430LS dye, functionalized with a Le^x derivative (1) and capped with a fucose-specific carbohydrate-binding protein (Aleuria aurantia lectin (AAL)). This design takes advantage of the affinity of AAL for Le^x overexpressed receptors in certain cancer cells. In the proximity of the cells, AAL is detached from MSNs to bind Le^x, and selectins in the cells bind Le^x in the gated MSNs, thereby inducing cargo delivery. Gated MSNs are nontoxic to colon cancer DLD-1 cells, and ATTO 430LS dye delivered correlated with the amount of Le^x antigen overexpressed at the DLD-1 cell surface. This is one of the few examples of MSNs using biologically relevant glycans for both capping (via interaction with AAL) and targeting (via interaction with overexpressed Le^x at the cell membrane).