Tailoring bisphosphonate-doped titanium films to optimally couple cellular responses and antibacterial activity for biomedical applications.

Titanium (Ti) is widely utilized as an implant material; nonetheless, its integration with bone tissue faces limitations due to a patient's comorbidities. To address this challenge, we employed a strategic approach involving the growth of thin films by spin-coating and surface functionalization with etidronate (ETI), alendronate (ALE), and risedronate (RIS). Our methodology involved coating of Ti cp IV disks with thin films of TiO2, hydroxyapatite (HA), and their combinations (1:1 and 1:2 v/v), followed by surface functionalization with ETI, ALE, and RIS. Bisphosphonate-doped films were evaluated in terms of surface morphology and physical-chemical properties by techniques such as electron microscopy, confocal microscopy, and x-ray photoelectron spectroscopy. The antibacterial potential of bisphosphonates alone or functionalized onto the Ti surface was tested against Staphylococcus aureus biofilms. Primary human bone mesenchymal stem cells were used to determine in vitro cell metabolism and mineralization. Although RIS alone did not demonstrate any antibacterial effect as verified by minimum inhibitory concentration assay, when Ti surfaces were functionalized with RIS, partial inhibition of Staphylococcus aureus growth was noted, probably because of the physical-chemical surface properties. Furthermore, samples comprising TiO2/HA (1:1 and 1:2 v/v) showcased an enhancement in the metabolism of nondifferentiated cells and can potentially enhance the differentiation of osteoblastic precursors. All samples demonstrated cell viability higher than 80%. Addition of hydroxyapatite and presence of bisphosphonates increase the metabolic activity and the mineralization of human bone mesenchymal cells. While these findings hold promise, it is necessary to conduct further studies to evaluate the system's performance in vivo and ensure its long-term safety. This research marks a significant stride toward optimizing the efficacy of titanium implants through tailored surface modifications.

Insight into the role of copper-based materials against the coronaviruses MHV-3, a model for SARS-CoV-2, during the COVID-19 pandemic.

Coating high-touch surfaces with inorganic agents, such as metals, appears to be a promising long-term disinfection strategy. However, there is a lack of studies exploring the effectiveness of copper-based products against viruses. In this study, we evaluated the cytotoxicity and virucidal effectiveness of products and materials containing copper against mouse hepatitis virus (MHV-3), a surrogate model for SARS-CoV-2. The results demonstrate that pure CuO and Cu possess activity against the enveloped virus at very low concentrations, ranging from 0.001 to 0.1% (w/v). A greater virucidal efficacy of CuO was found for nanoparticles, which showed activity even against viruses that are more resistant to disinfection such as feline calicivirus (FCV). Most of the evaluated products, with concentrations of Cu or CuO between 0.003 and 15% (w/v), were effective against MHV-3. Cryomicroscopy images of an MHV-3 sample exposed to a CuO-containing surface showed extensive damage to the viral capsid, presumably due to the direct or indirect action of copper ions.

Combination of in silico and cell culture strategies to predict biomaterial performance: Effects of sintering temperature on the biological properties of hydroxyapatite.

Advances in methodologies to evaluate biomaterials brought an explosive growth of data, ensuing computational challenges to better analyzing them and allowing for high-throughput profiling of biological systems cost-efficiently. In this sense, we have applied bioinformatics tools to better understand the biological effect of different sintering temperatures of hydroxyapatite (abbreviated HA; at 1100, 1150, and 1250°C) on osteoblast performance. To do, we have better analyzed an earlier deposited study, in which the access code is E-MTAB-7219, which the authors have explored different in silico tools on this purpose. In this study, differential gene expression analyses were performed using the gene set variation analysis (GSVA) algorithm from the transcriptomes respecting the thermal changes of HA, which were validated using exclusively in vitro strategies. Furthermore, in silico approaches elected biomarkers during cell behavior in response to different sintering temperatures of HA, and it was further validated using cell culture and qPCR technologies. Altogether, the combination of those strategies shows the capacity of sintered HA at 1250°C to present a better performance in organizing an adequate microenvironment favoring bone regeneration, angiogenesis and material resorption stimulus once it has promoted higher involvement of genes such as CDK2, CDK4 (biomarkers of cell proliferation), p15, Osterix gene (related with osteogenic differentiation), RANKL (related with osteoclastogenesis), VEGF gene (related with angiogenesis), and HIF1α (related with hypoxia microenvironment). Altogether, the combination of in silico and cell culture strategies shows the capacity of sintered HA at 1250°C in guaranteeing osteoblast differentiation and it can be related in organizing an adequate microenvironment favoring bone regeneration, angiogenesis, and material resorption stimulus.

Revisiting the hydroxylation phenomenon of SiO2: a study through "hard-hard" and "soft-soft" interactions.

Surface hydroxylation has been extensively studied over the years for a variety of applications, and studies involving hydroxylation of different silica surfaces are still carried out due to the interesting properties obtained from those modified surfaces. Although a number of theoretical studies have been employed to evaluate details on the hydroxylation phenomenon on silica (SiO2) surfaces, most of these studies are based on computationally expensive models commonly based on extended systems. In order to circumvent such an aspect, here we present a low-cost theoretical study on the SiO2 hydroxylation process aiming to evaluate aspects associated with water-SiO2 interaction. Details about local reactivity, chemical softness, and electrostatic potential were evaluated for SiO2 model substrates in the framework of the density functional theory (DFT) using a molecular approach. The obtained results from this new and promising approach were validated and complemented by fully atomistic reactive molecular dynamics (FARMD) simulations. Furthermore, the implemented approach proves to be a powerful tool that is not restricted to the study of hydroxylation, opening a promising route for low computational cost to analyze passivation and anchoring processes on a variety of oxide surfaces.

Biomimetic Growth of Metal-Organic Frameworks for the Stabilization of the Dentin Matrix and Control of Collagenolysis.

The dentin matrix is a collagenous scaffold structurally involved in anchoring resin-based materials to the tooth. Time-dependent degradation of this scaffold at the resin-dentin interface remains a core problem in adhesive dentistry, limiting the service life of dental fillings. This study explored the use of emergent materials termed metal-organic frameworks (MOFs)─formed by the self-assembly of metal ions and organic building blocks─to safeguard the collagen integrity in the functional dentin matrix. We demonstrate that collagen fibrils (from demineralized human dentin) can induce the biomimetic growth of MOF crystals as protective coatings to strengthen and stabilize the fibrils. Zeolitic imidazolate framework-8 (ZIF-8), a zinc-based microporous MOF, was used to fabricate the MOF composites via a "one-pot" reaction in water. The ZIF-modified dentin matrix presented superior mechanical strength and resistance to proteolysis, which can positively affect the longevity of collagen as an anchoring substrate. This work identifies a potential biomedical application of biomimetically synthesized MOFs in repairing dental tissues critical to restorative therapies.

Surface-Directed Mineralization of Fibrous Collagen Scaffolds in Simulated Body Fluid for Tissue Engineering Applications.

The use of polymer additives that stabilize fluidic amorphous calcium phosphate is key to obtaining intrafibrillar mineralization of collagen in vitro. On the other hand, this biomimetic approach inhibits the nucleation of mineral crystals in unconfined extrafibrillar spaces, that is, extrafibrillar mineralization. The extrafibrillar mineral content is a significant feature to replicate from hard connective tissues such as bone and dentin as it contributes to the final microarchitecture and mechanical stiffness of the biomineral composite. Herein, we report a straightforward route to produce densely mineralized collagenous composites via a surface-directed process devoid of the aid of polymer additives. Simulated body fluid (1×) is employed as a biomimetic crystallizing medium, following a preloading procedure on the collagen surface to quickly generate the amorphous precursor species required to initiate matrix mineralization. This approach consistently leads to the formation of extrafibrillar bioactive minerals in bulk collagen scaffolds, which may offer an advantage in the production of osteoconductive collagen-apatite materials for tissue engineering and repair purposes.

Titanium-Based Alloy Surface Modification with TiO2 and Poly(sodium 4-styrenesulfonate) Multilayers for Dental Implants.

Implant placement is an important repair method in dentistry and orthopedics. Increasing efforts have focused on optimizing the biocompatibility and osseointegration properties of titanium (Ti) and Ti-based alloys. In this work, Ti-based alloys were modified by the layer-by-layer (LbL) technique, which is a simple and versatile method for surface modification. The morphology and chemical structure of LbL films of poly(sodium 4-styrenesulfonate) (PSS) and Ti dioxide (TiO2) nanoparticles were first characterized employing ultraviolet-visible and Fourier-transform infrared spectroscopies as well as atomic force microscopy for further application in Ti-based alloy implants. The changes provoked by the LbL PSS/TiO2 film on the Ti-based alloy surfaces were then investigated by scanning electron microscopy and micro-Raman techniques. Finally, in vivo tests (immunolabeling and biomechanical analysis) performed with screw implants in rats suggested that PSS/TiO2 multilayers promote changes in both topography and chemical surface properties of the screw, providing beneficial effects for osteoblast activity. This simple and relatively low-cost growth process can open up possibilities to improve dental implants and, probably, bone implants in general.

MOF-Based Erodible System for On-Demand Release of Bioactive Flavonoid at the Polymer-Tissue Interface.

Plant-derived compounds incite applications virtually on every biomedical field due to the expedient antioxidant, anti-inflammatory and antimicrobial properties in conjunction with a natural character. Here, quercetin (QCT), a flavonoid with therapeutic potentials relevant to the oral environment, was encapsulated within metal-organic frameworks (MOFs) to address the concept of on-demand release of phytochemicals at the biointerface. We verified the applicability of a microporous MOF (ZIF-8) as a controlled-release system for QCT, as well as investigated the incorporation of QCT@ZIF-8 microparticles into a dental adhesive resin for desirable therapeutic capabilities at the tooth-restoration interface. QCT was encapsulated within the frameworks through a water-based, one-step synthetic process. The resulting QCT@ZIF-8 microparticles were characterized with respect to chemical composition, crystal structure, thermal behavior, micromorphology, and release profile under acidic and physiological conditions. A model dental adhesive formulation was enriched with the bioactive microparticles; both the degree of conversion (DC) of methacrylic double bonds and the polymer thermal behavior were accounted for. The results confirm that crystalline QCT@ZIF-8 microparticles with attractive loading capacities, submicron sizes, high thermal stability and responsiveness to environmental pH change were successfully manufactured. The concentration of QCT@ZIF-8 in the resin system was a key factor to maintain an optimal DC plateau and rate of polymerization. Essentially, one-step encapsulation of QCT in biocompatible ZIF-8 matrices can be easily achieved, and QCT@ZIF-8 microparticles proved as smart platforms to carry bioactive compounds with potential use to prevent microbial and enzymatic degradation of hard tissues and extracellular matrix components.

Exposure effects of endotoxin-free titanium-based wear particles to human osteoblasts.

Titanium-based materials are widely employed by the biomedical industry in orthopedic and dental implants. However, when placed into the human body, these materials are highly susceptible to degradation processes, such as corrosion, wear, and tribocorrosion. As a consequence, metallic ions or particles (debris) may be released, and although several studies have been conducted in recent years to better understand the effects of their exposure to living cells, a consensual opinion has not yet been obtained. In this work, we produced metallic-based wear particles by tribological tests carried out on Ti-6Al-4V and Ti-15Zr-15Mo alloys. They were posteriorly physicochemically characterized according to their crystal structure, size, morphology, and chemical composition and compared to Ti-6Al-4V commercially available particles. Finally, adsorbed endotoxins were removed (by applying a specific thermal treatment) and endotoxin-free particles were used in cell experiments to evaluate effects of their exposure to human osteoblasts (MG-63 and HOb), namely cell viability/metabolism, proinflammatory cytokine production (IL-6 and PGE2), and susceptibility to internalization processes. Our results indicate that tribologically-obtained wear particles exhibit fundamental differences in terms of size (smaller) and morphology (irregular shapes and rough surfaces) when compared to the commercial ones. Consequently, both Ti-6Al-4V and Ti-15Zr-15Mo particles were able to induce more pronounced effects on cell viability (decrease) and cytokine production (increase) than did Ti-6Al-4V commercial particles. Furthermore, both types of wear particles penetrated osteoblast membranes and were internalized by the cells. Influences on cytokine production by endotoxins were also demonstrated.

Vanadium ionic species from degradation of Ti-6Al-4V metallic implants: In vitro cytotoxicity and speciation evaluation.

Among the metallic materials used in biomedical industry, the most common choice for orthopedics and dental implants is titanium (Ti) and its alloys, mainly due to their superior corrosion and tribocorrosion resistance and biocompatibility. Under different conditions in vivo, such as different pH levels, composition of body fluid and mechanical loads, metallic materials may suffer from degradation, resulting in the release of undesired wear particles and ions. In particular, the Ti-6Al-4V system represents almost half of the production of Ti as a biomaterial and many concerns have been raised about titanium, aluminum and vanadium ions releasing. This work evaluates the cytotoxic effects of vanadium ionic species generated from Ti-6Al-4V surfaces regarding mouse pre-osteoblasts and fibroblasts. In our cell viability tests, we noticed a significant decrease in the fibroblasts' cell viability with vanadium concentrations (23 µM) close to those previously reported to be observed in vivo in patients with poor functioning of their medical devices based on Ti-6Al-4V (30 µM). Speciation modelling was carried-out, for the first time, to this system. Results of the modelling reveal that vanadates(V), namely H2VO4- and HVO42-, are the main species present in cell culture media. Otherwise, in synovial fluids of individuals with poorly functioning implants, wherein the concentration of vanadium may go up to ca. 30 µM, the tentative theoretical speciation data indicates a high occurrence probability for VV- and VIV-species bound to albumin and hyaluronic acid. In conclusion, even though relatively low concentrations of vanadium may be released from Ti-6Al-4V implants in vivo, the continuous contact with peri-implant cells for long periods of time may represent a potentially hazardous situation.

Bone repair with raloxifene and bioglass nanoceramic composite in animal experiment.

OBJECTIVE: This study proposes to evaluate, by means of microtomographic analysis, the topical potential of raloxifene combined with BioGran® through the sonochemical method in the repair of critical bone defects in the calvaria of rats. The hypothesis was that the homogenization of Raloxifene to Biogran at the 20% concentration would improve the bone repair at the grafted site. MATERIALS AND METHODS: A 5-mm calvaria bone defect was induced in three groups: CTR (100% BioGran®); RAL10 (90% BioGran® and 10% raloxifene), and RAL20 (80% BioGran® and 20% raloxifene). The animals were euthanized after 30 days and the microCT analysis was then performed to evaluate the parameters bone volume (BV), bone volume percentage (BV/TV), trabecular bone thickness (Tb.Th), and the separation and number of trabeculae (Tb.Sp and Tb.N). The obtained results were compared using ANOVA and Tukey test (p < 0.05). RESULTS: The best results were found for the CTR and RAL20 groups, in which the BV, BV/TV, Tb.Sp, and Tb.N parameters were statistically significant in comparison with RAL10 (p < 0.05). CONCLUSIONS: In view of the results obtained in this experiment, we can conclude that BioGran® alone or in an 80/20 mass concentration with raloxifene can lead to favorable bone formation.

Titanium surface bio-functionalization using osteogenic peptides: Surface chemistry, biocompatibility, corrosion and tribocorrosion aspects.

Titanium (Ti) is widely used in biomedical devices due to its recognized biocompatibility. However, implant failures and subsequent clinical side effects are still recurrent. In this context, improvements can be achieved by designing biomaterials where the bulk and the surface of Ti are independently tailored. The conjugation of biomolecules onto the Ti surface can improve its bioactivity, thus accelerating the osteointegration process. Ti was modified with TiO2, two different spacers, 3-(4-aminophenyl) propionic acid (APPA) or 3-mercaptopropionic acid (MPA) and dentin matrix protein 1 (DMP1) peptides. X-ray photoelectron spectroscopy analysis revealed the presence of carbon and nitrogen for all samples, indicating a success in the functionalization process. Furthermore, DMP1 peptides showed an improved coverage area for the samples with APPA and MPA spacers. Biological tests indicated that the peptides could modulate cell affinity, proliferation, and differentiation. Enhanced results were observed in the presence of MPA. Moreover, the immobilization of DMP1 peptides through the spacers led to the formation of calcium phosphate minerals with a Ca/P ratio near to that of hydroxyapatite. Corrosion and tribocorrosion results indicated an increased resistance to corrosion and lower mass loss in the functionalized materials, showing that this new type of functional material has attractive properties for biomaterials application.

Titanium dioxide nanotubes addition to self-adhesive resin cement: Effect on physical and biological properties.

OBJECTIVES: This study has investigated the influence of Titanium dioxide nanotubes (TiO2-nt) addition to self-adhesive resin cement on the degree of conversion, water sorption, and water solubility, mechanical and biological properties. METHODS: A commercially available auto-adhesive resin cement (RelyX U200™, 3M ESPE) was reinforced with varying amounts of nanotubes (0.3, 0.6, 0.9wt%) and evaluated at different curing modes (self- and dual cure). The DC in different times (3, 6, 9, 12 and 15min), water sorption (Ws) and solubility (Sl), 3-point flexural strength (σf), elastic modulus (E), Knoop microhardness (H) and viability of NIH/3T3 fibroblasts were performed to characterize the resin cement. RESULTS: Reinforced self-adhesive resin cement, regardless of concentration, increased the DC for the self- and dual-curing modes at all times studied. The concentration of the TiO2-nt and the curing mode did not influence the Ws and Sl. Regarding σf, concentrations of both 0.3 and 0.9wt% for self-curing mode resulted in data similar to that of dual-curing unreinforced cement. The E increased with the addition of 0.9wt% for self-cure mode and H increased with 0.6 and 0.9wt% for both curing modes. Cytotoxicity assays revealed that reinforced cements were biocompatible. SIGNIFICANCE: TiO2-nt reinforced self-adhesive resin cement are promising materials for use in indirect dental restorations. Taken together, self-adhesive resin cement reinforced with TiO2-nt exhibited physicochemical and mechanical properties superior to those of unreinforced cements, without compromising their cellular viability.

Structural, optical, and magnetic properties of NiMoO4 nanorods prepared by microwave sintering.

We report on the structural, optical, and magnetic properties of α,ß-NiMoO4 nanorods synthesized by annealing the NiMoO4:nH2O precursor at 600°C for 10 minutes in a domestic microwave. The crystalline structure properties of α,ß-NiMoO4 were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman (FT-Raman) spectroscopies. The particle morphologies and size distributions were identified by field emission microscopy (FE-SEM). Experimental data were obtained by magnetization measurements for different applied magnetic fields. Optical properties were analyzed by ultraviolet-visible (UV-vis) and photoluminescence (PL) measurements. Our results revealed that the oxygen atoms occupy different positions and are very disturbed in the lattice and exhibit a particular characteristic related to differences in the length of the chemical bonds (Ni-O and Mo-O) of the cluster structure or defect densities in the crystalline α,ß-NiMoO4 nanorods, which are the key to a deeper understanding of the exploitable physical and chemical properties in this study.

In situ sonochemical synthesis of ZnO particles embedded in a thermoplastic matrix for biomedical applications.

Zinc oxide particles were synthesized and dispersed in situ in a polystyrene (PS) matrix using ultrasound. PS ultrasonic degradation was investigated at different polymer concentrations in organic solvent in contact with aqueous media prior to the particle synthesis. Decrease in weight-average molecular weight (Mw) was strongly dependent on polymer concentration in organic solvent and sonication time: degradation occurred less at higher polymer concentration, yet increased with longer times of more than 30min. The ZnO particles with a 800nm flower-like morphology were dispersed in the polystyrene matrix in situ; the composite presented both a lower average molecular weight (Mw) and lower number average molecular weight Mn when compared to pristine polystyrene, however thermal degradation temperature and Young's modulus were similar to the pristine polystyrene. The composite prepared in situ presented lower particle aggregation in comparison with ZnO commercially dispersed with ultrasound under the same conditions. Antibacterial activity of the ZnO/PS coating was tested against Escherichia coli (Gram-negative bacteria; DMS No. 10290) by evaluating bacterial growth inhibition after 20h on contact with the film surface. The results indicated that bacterial growth was inhibited in the medium in contact with the composite prepared in situ compared to the film of composite prepared by mixing and the pristine PS. This study showed the potential use of ZnO/PS composite prepared in situ as antibacterial coatings.