Broad-spectrum bactericidal activity of a new bioactive grafting material (F18) against clinically important bacterial strains

Mitigating jaw osteonecrosis: bioactive glass and pericardial membrane combination in a rat model

Objectives

Bisphosphonates (BFs) show clinical effectiveness in managing osteoporosis and bone metastases but pose risks of bisphosphonate-related jaw osteonecrosis (BRONJ). With no established gold standard for BRONJ treatment, our focus is on symptom severity reduction. We aimed to assess the preventive effects of bioactive glass and/or pericardial membrane in a preclinical BRONJ model, evaluating their potential to prevent osteonecrosis and bone loss post-tooth extractions in zoledronic acid (ZA)-treated animals.

Methods

Rats, receiving ZA or saline biweekly for four weeks, underwent 1st and 2nd lower left molar extractions. Pericardial membrane alone or with F18 bioglass was applied post-extractions. Microarchitecture analysis and bone loss assessment utilized computerized microtomography (CT) and positron emission tomography (PET) with 18F-FDG and 18F-NaF tracers. Histological analysis evaluated bone injury.

Results

Exclusive alveolar bone loss occurred post-extraction in the continuous ZA group, inducing osteonecrosis, osteolysis, osteomyelitis, and abscess formation. Concurrent pericardial membrane with F18 bioglass application prevented these outcomes. Baseline PET/CT scans showed no discernible uptake differences, but post-extraction 18F-FDG tracer imaging revealed heightened glucose metabolism at the extraction site in the ZA-treated group with membrane, contrasting the control group.

Conclusion

These findings suggest pericardial membrane with F18 bioglass effectively prevents BRONJ in the preclinical model.

Final irrigation with bioglass solution in regenerative endodontic procedure induces tissue formation inside the root canals, collagen maturation, proliferation cell and presence of osteocalcin

AIM

To evaluate the influence of an experimental solution of cobalt-doped F18 bioactive glass (F18Co) on tissue repair following regenerative endodontic procedure (REP) in rat molars.

METHODOLOGY

The F18Co solution was prepared at a ratio of 1:5 F18Co powder to distilled water. The right or left upper first molars of 12 Wistar rats were used, where the pulps were exposed, removed, and irrigated with 2.5% sodium hypochlorite (NaOCl), followed by 17% ethylenediaminetetraacetic acid (EDTA) (5 min each). Subsequently, the molars were divided into two groups (n = 6): REP-SS and REP-F18Co, where they received a final irrigation (5 min) with saline solution (SS) or F18Co solution, respectively. Then, intracanal bleeding was induced, and the tooth was sealed. Untreated molars were used as controls (n = 3). At 21 days, the rats were euthanized, and the specimens were processed for analysis of mineralized tissue and soft tissue formation inside the root canal using haematoxylin-eosin. The presence and maturation of collagen were evaluated by Masson's trichrome and picrosirius red staining. Immunolabelling analyses of proliferating cell nuclear antigen (PCNA) and osteocalcin (OCN) were performed. The data were submitted to the Mann-Whitney U-test (p < .05).

RESULTS

There was a similar formation of mineralized tissue in thickness and length in REP-SS and REP-F18Co groups (p > .05). Regarding the presence of newly formed soft tissue, most specimens of the REP-F18Co had tissue formation up to the cervical third of the canal, whilst the REP-SS specimens showed formation up to the middle third (p < .05), and there was higher maturation of collagen in REP-F18Co (p < .05). The number of PCNA-positive cells found in the apical third of the root canal was significantly higher in the F18Co group, as well as the OCN immunolabelling, which was severe in most specimens of REP-F18Co, and low in most specimens of REP-SS.

CONCLUSION

The final irrigation with F18Co bioactive glass solution in REP did not influence mineralized tissue formation but induced soft tissue formation inside the root canals, with higher collagen maturation, and an increase in PCNA-positive cells and OCN immunolabelling.

Effect of bioactive Biosilicate® /F18 glass scaffolds on osteogenic differentiation of human adipose stem cells

This study evaluated the gene expression profile of the human adipose-derived stem cells (hASCs) grown on the Biosilicate^® /F18 glass (BioS-2P/F18) scaffolds. hASCs were cultured using the osteogenic medium (control), the scaffolds, and their ionic extract. We observed that ALP activity was higher in hASCs grown on the BioS-2P/F18 scaffolds than in hASCs cultured with the ionic extract or the osteogenic medium on day 14. Moreover, the dissolution product group and the control exhibited deposited calcium, which peaked on day 21. Gene expression profiles of cell cultured using the BioS-2P/F18 scaffolds and their extract were evaluated in vitro using the RT² Profiler polymerase chain reaction (PCR) microarray on day 21. Mineralizing tissue-associated proteins, differentiation factors, and extracellular matrix enzyme expressions were measured using quantitative PCR. The gene expression of different proteins involved in osteoblast differentiation was significantly up-regulated in hASCs grown on the scaffolds, especially BMP1, BMP2, SPP1, BMPR1B, ITGA1, ITGA2, ITGB1, SMAD1, and SMAD2, showing that both the composition and topographic features of the biomaterial could stimulate osteogenesis. This study demonstrated that gene expression of hASCs grown on the scaffold surface showed significantly increased gene expression related to hASCs cultured with the ionic extract or the osteogenic medium, evidencing that the BioS-2P/F18 scaffolds have a substantial effect on cellular behavior of hASCs.

Biofilm Formation and Expression of Virulence Genes of Microorganisms Grown in Contact with a New Bioactive Glass

Bioactive glass F18 (BGF18), a glass containing SiO2-Na2O-K2O-MgO-CaO-P2O5, is highly effective as an osseointegration buster agent when applied as a coating in titanium implants. Biocompatibility tests using this biomaterial exhibited positive results; however, its antimicrobial activity is still under investigation. In this study we evaluated biofilm formation and expression of virulence-factor-related genes in Candida albicans, Staphylococcus epidermidis, and Pseudomonas aeruginosa grown on surfaces of titanium and titanium coated with BGF18. C. albicans, S. epidermidis, and P. aeruginosa biofilms were grown on specimens for 8, 24, and 48 h. After each interval, the pH was measured and the colony-forming units were counted for the biofilm recovery rates. In parallel, quantitative real-time polymerase chain reactions were carried out to verify the expression of virulence-factor-related genes. Our results showed that pH changes of the culture in contact with the bioactive glass were merely observed. Reduction in biofilm formation was not observed at any of the studied time. However, changes in the expression level of genes related to virulence factors were observed after 8 and 48 h of culture in BGF18. BGF18 coating did not have a clear inhibitory effect on biofilm growth but promoted the modulation of virulence factors.

Bactericidal activity and biofilm inhibition of F18 bioactive glass against Staphylococcus aureus

Antimicrobial treatment failure has been increasing at alarming rates. In this context, the bactericidal properties of biocompatible antimicrobial agents have been widely studied. F18 is a recently developed bioactive glass that presents a much wider working range when compared to other bioactive glasses, a feature that allows it to be used for coating metallic implants, sintering scaffolds or manufacturing fibers for wound healing applications. The aim of this study was to investigate the in vitro bactericidal and anti-biofilm activity of F18 glass as a powder and as a coating on steel samples, and to explore the effects of its dissolution products at concentrations from 3 mg/mL to 50 mg/mL against the Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) biofilms. Furthermore, we intend to verify whether changes in the medium pH could influence the bactericidal activity of F18. The results indicated that F18 presented bactericidal activity in preformed S. aureus and MRSA biofilms, reducing more than 6 logs of the viable cells that remained in contact with 50 mg/mL for 24 h. Moreover, an anti-biofilm activity was observed after 12 h of direct contact, with a drop of more than 6 logs of the viable bacterial population. Neutralization of the F18 solution pH decreased its bactericidal efficacy. These results indicate that the F18 glass could be considered as an alternative material for controlling and treating infections by S. aureus.

Biomaterials for orthopedics: anti-biofilm activity of a new bioactive glass coating on titanium implants

This study evaluated adhesion and biofilm formation by Candida albicans, Pseudomonas aeruginosa and Staphylococcus epidermidis on surfaces of titanium (Ti) and titanium coated with F18 Bioactive Glass (BGF18). Biofilms were grown and the areas coated with biofilm were determined after 2, 4 and 8 h. Microscopy techniques were applied in order to visualize the structure of the mature biofilm and the extracellular matrix. On the BGF18 specimens, there was less biofilm formation by C. albicans and S. epidermidis after incubation for 8 h. For P. aeruginosa biofilm, a reduction was observed after incubation for 4 h, and it remained reduced after 8 h on BGF18 specimens. All biofilm matrices seemed to be thicker on BGF18 surface than on titanium surfaces. BGF18 showed significant anti-biofilm activity in comparison with Ti in the initial periods of biofilm formation; however, there was extensive biofilm after incubation for 48 h.

Electrospun F18 Bioactive Glass/PCL-Poly (ε-caprolactone)-Membrane for Guided Tissue Regeneration

Barrier membranes that are used for guided tissue regeneration (GTR) therapy usually lack bioactivity and the capability to promote new bone tissue formation. However, the incorporation of an osteogenic agent into polymeric membranes seems to be the most assertive strategy to enhance their regenerative potential. Here, the manufacturing of composite electrospun membranes made of poly (ε-caprolactone) (PCL) and particles of a novel bioactive glass composition (F18) is described. The membranes were mechanically and biologically tested with tensile strength tests and tissue culture with MG-63 osteoblast-like cell line, respectively. The PCL-F18 composite membranes demonstrated no increased cytotoxicity and an enhanced osteogenic potential when compared to pure PCL membranes. Moreover, the addition of the bioactive phase increased the membrane tensile strength. These preliminary results suggested that these new membranes can be a strong candidate for small bone injuries treatment by GTR technique.