Biologically synthesized silver nanoparticles as potent antibacterial effective against multidrug-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most worrisome infectious bacteria due to its intrinsic and acquired resistance against several antibiotics and the recalcitrance of its infections; hence, the development of novel antimicrobials effective against multidrug‐resistant P. aeruginosa is mandatory. In this work, silver nanoparticles obtained by green synthesis using a leaf extract and fungi were tested against a battery of clinical strains from cystic fibrosis, pneumonia and burnt patients, some of them with multidrug resistance. Both nanoparticles showed a potent antibacterial effect, causing severe damage to the cell wall, membrane and DNA, and inducing the production of reactive oxygen species. Moreover, the nanoparticles derived from fungi showed synergistic antibacterial effects with the antibiotics meropenem and levofloxacin for some clinical strains and both kinds of nanoparticles were nontoxic for larvae of the moth Galleria mellonella, encouraging further research for their implementation in the treatment of P. aeruginosa infections.

Gel dressing based on type I collagen modified with oligourethane and silica for skin wound healing

Cutaneous wound healing is a complex process that leads the skin reparation with the formation of scar tissue that typically lacks skin appendages. This fact drives us to find new strategies to improve regenerative healing of the skin. This study outlines, the contribution of colloidal silica particles and oligourethane crosslinking on the collagen material properties and the effect on skin wound healing in rats. We characterized the gel properties that are key forin-situgelation, which is accomplished by the latent reactivity of oligourethane bearing blocked isocyanate groups to crosslink collagen while entrapping silica particles. The swelling/degradation behavior and the elastic modulus of the composite gel were consistent with the modification of collagen type I with oligourethane and silica. On the other hand, these gels were characterized as scaffold for murine macrophages and human stem cells. The application of a composite gel dressing on cutaneous wounds showed a histological appearance of the recovered skin as intact skin; featured by the epidermis, hair follicles, sebaceous glands, subcutaneous adipose layer, and dermis. The results suggest that the collagen-based composite dressings are promising modulators in skin wound healing to achieve a regenerative skin closure with satisfactory functional and aesthetic scars.

[Cancer stem cells in oral squamous cell carcinoma. Literature review]

Objective

To perform a literature review on oral squamous cell carcinoma, the presence of cancer stem cells; their association with the course of the disease and therapeutic applications.

Methods

: A search was performed in the PubMed database by entering the following algorithm: ((((neoplastic stem cells [MeSH Terms ]) OR (Cancer stem cells [Text Word ])) AND (Squamous Cell Carcinoma of Head and Neck [MeSH Terms])) AND (Oral squamous cell carcinoma [Text Word ]), to find articles in english published between 2012 and 2022. The PRISMA diagram was used to identify and select the articles.

Results

A result of 49 articles was obtained; of which 27 were chosen according to the title and abstract in their association with the topic. In addition, 8 additional articles suggested by their relationship with the information previously searched were included. In total, 35 articles were evaluated. There has been found that tumoral cells in squamous oral carcinoma are heterogeneous since they include cancer stem cells wich possess characteristics of stem and neoplasic cells; which possess characteristics of stem cells as well as neoplastic cells; they have been associated with disease progression, recurrence, and metastasis and have been considered to be a key mechanism of therapy failure.

Conclusions

The expression of stem cell markers in oral squamous cell carcinomas has been demonstrated and has contributed to their identification in oral squamous cell carcinomas and has been implicated in the behavior of cancer cells. New therapeutic measures aimed at eliminating cancer stem cells have been proposed and developed.

2D Nanosheets-A New Class of Therapeutic Formulations against Cancer

Researchers in cancer nanomedicine are exploring a revolutionary multifaceted carrier for treatment and diagnosis, resulting in the proposal of various drug cargos or "magic bullets" in this past decade. Even though different nano-based complexes are registered for clinical trials, very few products enter the final stages each year because of various issues. This prevents the formulations from entering the market and being accessible to patients. In the search for novel materials, the exploitation of 2D nanosheets, including but not limited to the highly acclaimed graphene, has created extensive interest for biomedical applications. A unique set of properties often characterize 2D materials, including semiconductivity, high surface area, and their chemical nature, which allow simple decoration and functionalization procedures, structures with high stability and targeting properties, vectors for controlled and sustained release of drugs, and materials for thermal-based therapies. This review discusses the challenges and opportunities of recently discovered 2D nanosheets for cancer therapeutics, with special attention paid to the most promising design technologies and their potential for clinical translation in the future.

Bacteria cultured from the gut of Meccus pallidipennis (Hemiptera: Reduviidae), a triatomine species endemic to Mexico

The study of intestinal microbiota in vector insects like triatomines is paramount in parasitology because many parasitic species inhabit the vector's gut. Although knowledge on the gut microbiota in various vectors of the parasitic flagellate Trypanosoma cruzi has grown, research efforts have focused on South American triatomines. This study reports the isolation of bacterial microbiota in the anterior and posterior gut of Meccus pallidipennis (a triatomine species endemic to Mexico) by culture, as well as its identification by phenotypic and biochemical tests and its quantification by counting colony-forming units. The study was performed on fifth-instar nymph and adult specimens of M. pallidipennis, either laboratory-bred or collected in the field and either infected or not with T. cruzi. Overall, 17 bacterial species were identified, with the genera Bacillus and Staphylococcus being the most prevalent regardless of the origin of the insects. No differences were observed in the number of bacterial species in the gut of laboratory-bred and field-collected insects, neither with respect to life stage or infection status. In general, the Shannon-Weaver diversity index was higher in non-infected insects than in infected ones. Further studies using non-culture methods are required to determine whether bacterial species diversity is modified by laboratory breeding.

Biological and physico-mechanical properties of poly(methyl methacrylate) enriched with graphene oxide as a potential biomaterial

Objective: To determine the cytotoxicity and effects of graphene oxide (GO) on cellular proliferation of gingival-fibroblasts, pulpdental cells and human osteoblasts in culture, and to determine the physical, mechanical and biological properties of poly (methyl methacrylate) (PMMA) enriched with GO. Material and Methods: T he G O w as c haracterized with SEM. Cytotoxicity and cell proliferation were determined by the MTT bioassay. The physical-mechanical tests (flexural strength and elastic modulus) were carried out with a universal testing machine. Sorption and solubility were determined by weighing before and after drying and immersion in water. Porosity was evaluated by visual inspection. Data were analyzed with Student's t-test and Tukey's post-hoc ANOVA. Results: The GO has a heterogeneous morphology and a particle size of 66.67±64.76 μm. GO has a slight to no-cytotoxicity (>50-75% viability) at 1-30 days, and at 24 hours incubation of PMMA with GO significantly stimulates osteoblasts (45±8%, p<0.01). The physical and mechanical properties of PMMA with GO increase considerably without altering sorption, solubility and porosity. Conclusion: GO alone or with PMMA has an acceptable biocompatibility, could contribute to cell proliferation, cell regeneration and improve the physical-mechanical properties of PMMA.

Antibacterial properties of phenothiazine derivatives against multidrug-resistant Acinetobacter baumannii strains

AIM

As options to treat recalcitrant bacterial infections which are increasingly limited due to multidrug-resistant strains, searching for new, effective antibacterial compounds is necessary. One strategy is to generate treatment alternatives by drug repurposing.

METHODS AND RESULTS

In this work, phenotypic microarrays were used for the screening of miscellaneous compounds against the growth and biofilm formation of Acinetobacter baumannii, an important emergent multidrug-resistant opportunistic pathogen. The results showed that the phenothiazine derivatives, such as promethazine, trifluoperazine, thioridazine, and chlorpromazine, inhibited the growth of antibiotic-sensitive and multidrug-resistant strains (showing minimal inhibitory concentrations ranging from 0·05 to 0·6 g l^-1 and minimal bactericidal concentrations ranging from 0·1 to 2·5 g l^-1 ). All phenothiazine derivatives were active against biofilm cells (with minimal biofilm eradication concentrations ranging from 0·5 to >3 g l^-1 ). Chlorpromazine promoted reactive oxigen species (ROS) production, and cell membrane and DNA damage. Chlorpromazine showed synergy with antibiotics such as ceftazidime, meropenem, and colistin and was an effective treatment for experimentally infected Galleria mellonella when combined with ceftazidime.

CONCLUSIONS

It was demonstrated that phenothiazine derivatives, especially chlorpromazine, are drugs with attractive antibacterial properties against nosocomial MDR strains of A. baumannii, by generating ROS and cell membrane and DNA damage.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study indicates that repurposing phenothiazine derivatives for treating recalcitrant infections by A. baumannii could be promising.

Copper nanoparticles as nanofillers in an adhesive resin system: An in vitro study

BACKGROUND

The incorporation of an antibacterial agent into an adhesive could improve its clinical performance. Some nanoparticles (NPs), including copper nanoparticles (Cu NPs), display an antibacterial effect. Therefore, Cu NPs could act as a nanofiller when added to an adhesive.

OBJECTIVES

The aim of this study was to evaluate the antibacterial activity, cytotoxicity and shear bond strength (SBS) of an experimental dental adhesive with Cu NPs.

MATERIAL AND METHODS

Different concentrations (0.0050 wt%, 0.0075 wt% and 0.0100 wt%) of Cu NPs were added to the adhesive. The distribution of Cu NPs in the polymer matrix was observed based on transmission electron microscope (TEM) images. The antimicrobial activity of the adhesive + Cu NPs was evaluated with the agar disk diffusion test against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Streptococcus mutans (S. mutans). The cytotoxicity assay was performed by means of the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method with human pulp cells (HPC). Additionally, the SBS tests were carried out (n = 31) and the modes of fracture were registered. The vestibular and lingual surfaces of each tooth were randomly assigned to the study groups (group I - control adhesive; group II - adhesive + 0.0100 wt% Cu NPs). The samples were statistically analyzed (p ≤ 0.05).

RESULTS

The adhesive + 0.0100 wt% Cu NPs showed inhibition zones against the strains under study that were similar to, or slightly smaller than, the halos produced by chlorhexidine (CHX) and specific drugs for each strain (30 μg of cefotaxime against S. mutans and S. aureus, and 1.25/3.75 μg of sulfamethoxazole/ trimethoprim against E. coli). The control adhesive was moderately cytotoxic (relative cell viability of 36.7 ±0.8%), being more cytotoxic than Cu NPs themselves (58.3 ±0.1%). A significantly higher SBS was obtained for the adhesive + 0.0100 wt% Cu NPs (6.038 ±2.95 MPa) than for the control group (3.278 ±1.75 MPa). The modes of fracture in group I were almost equally distributed between adhesive and cohesive failures whereas in group II, the failure was mainly cohesive.

CONCLUSIONS

The results of this study suggest that incorporating Cu NPs into an adhesive improves its SBS and provides it with antibacterial properties, without increasing its inherent cytotoxicity - 2 desirable characteristics for the dental adhesives of composites.

Anti-Inflammatory and Antibacterial Activity of the Chitosan/Chlorhexidine Gel Commercial Preparation for Postexodontia Treatment: An In Vitro Study

Objective  The present study aimed to assess in vitro the antibacterial activity, cytotoxicity, and the expression of prostaglandin E ₂ (PGE ₂ ) of Bexident post topical gel (BP).

Materials and Methods  The broth dilution test was performed to analyze the antimicrobial activity of BP against Staphylococcus aureus , Escherichia coli , and Streptococcus mutans . Minimal bactericidal concentrations (MBCs) and minimal inhibitory concentrations (MICs) were assessed. Cytotoxic activity was performed by the MTT (tetrazolium dye) method on human gingival fibroblast (HGF), human bone cells (HBC), and human pulp cells (HPC) (from primary cell culture) and HGF-1 from American Type Culture Collection. The expression of PGE ₂ produced by RAW 264.7 cells was determined by ELISA utilizing an Enzyme Immuno-Assay Kit.

Statistical Analysis  Shapiro–Wilks normality test and Mann–Whitney U test were performed for all data.

Results  The MBCs of BP for S. aureus , E. coli , and S. mutans were found at 25, 50, and 12.5%, respectively. The MICs for the same strains were found at 12.5, 25, and 3.125%. The CC ₅₀ of BP gel for HBC, HPC, and HGF, and HGF-1 were 12.5 ± 1.09, 0.37 ± 0.02, 0.35 ± 0.02, and 20.4 ± 0.02%, respectively. The levels of expression PGE ₂ produced by RAW 264.7 cells treated with IL-1β exhibit an inverse dose-dependent effect on the concentrations of BP gel used.

Conclusion  Our results indicate that the BP gel has a great antibacterial effect, adequate biocompatibility, showing a decrease in the expression of PGE ₂ on cells with previously induced inflammation. Due to the above, its use as a healing agent after oral surgery seems to be adequate.

Antifungal and Cytotoxic Evaluation of Photochemically Synthesized Heparin-Coated Gold and Silver Nanoparticles

Heparin-based silver nanoparticles (AgHep-NPs) and gold nanoparticles (AuHep-NPs) were produced by a photochemical method using silver nitrate and chloroauric acid as metal precursors and UV light at 254 nm. UV-Vis spectroscopy graphs showed absorption for AgHep-NPs and AuHep-NPs at 420 nm and 530 nm, respectively. TEM revealed a pseudospherical morphology and a small size, corresponding to 10-25 nm for AgHep-NPs and 1.5-7.5 nm for AuHep-NPs. Their antifungal activity against Candida albicans, Issatchenkia orientalis (Candida krusei), and Candida parapsilosis was assessed by the microdilution method. We show that AgHep-NPs were effective in decreasing fungus density, whereas AuHep-NPs were not. Additionally, the viability of human gingival fibroblasts was preserved by both nanoparticle types at a level above 80%, indicating a slight cytotoxicity. These results are potentially useful for applications of the described NPs mainly in dentistry and, to a lesser extent, in other biomedical areas.

Evaluation of in vitro bioactivity and in vitro biocompatibility of Polycaprolactone/Hyaluronic acid/Multiwalled Carbon Nanotubes/Extract from Mimosa tenuiflora composites

BACKGROUND

The development of biomaterial scaffolds and implementation of tissue engineering techniques are necessary. Therefore, Polycaprolactone/Sodium Hyaluronate/Multiwalled Carbon Nanotubes/Extract of Mimosa tenuiflora composites have been produced by a thermally-induced phase separation method.

OBJECTIVE

The objective of this research was to evaluate the in vitro bioactivity and in vitro biocompatibility of the composites.

METHODS

The in vitro bioactivity of the composites was assessed by soaking them in simulated body fluid for 7, 14, 21, and 28 days. The structure and composition of the composites were analyzed using scanning electron microscopy coupled with energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Also, the in vitro biocompatibility of the composites was evaluated by means of alkaline phosphatase activity of the osteoblasts and by measuring the metabolic activity of the cells using MTT assay.

RESULTS

The results show a porous and interconnected morphology with enhanced bioactivity. It was observed that the incorporation of Mimosa tenuiflora in the composites promotes increased viability of osteoblasts in the scaffolds.

CONCLUSIONS

The results show the efficiency of bioactive and biocompatible composites and their potential as candidates for tissue engineering applications.

Cytotoxicity of solutions recommended for the storage of avulsed teeth in cultures with periodontal ligament cells

Introduction

The medium for avulsed teeth storage until their reimplantation is key to the preservation of human periodontal ligament fibroblasts (HPLF).

Objective

Our purpose was to compare the cytotoxic effect of milk and isotonic solution, used for the storage of avulsed teeth, on the preservation of HPLF.

Method

A subculture of periodontal ligament fibroblasts was carried out with a density of 1:2 (3 ×10⁵ cells/mL) and was incubated for 48 hours. The cells were divided in two groups, which were placed either in milk or isotonic solution for 24 hours at 5% CO₂, 37 ºC and 95% humidity. The number of viable cells was determined with a colorimetric fast assay by the reduction of MTT and mitochondrial activity. Data were processed with the Shapiro-Wilk normality test, Student's t-test and paired Student's t-test (with significance set at 0.05).

Results

The cells exposed to milk for 24 hours showed statistically significant cytotoxicity at concentrations of 0.09, 0.39, 0.78, 1.56, 3.125, 6.25 and 50%. HPLFs exposed to isotonic solution showed no significant reduction in the number of cells at concentrations of 25 and 50%.

Conclusion

Isotonic solution appears to be better for HPLF 24-hour storage in comparison with whole milk.

Mineral trioxide aggregate enriched with iron disulfide nanostructures: an evaluation of their physical and biological properties

The purpose of this study was to characterize mineral trioxide aggregates (MTA) enriched with iron disulfide (FeS₂ ) nanostructures at different concentrations, and to investigate their storage modulus, radiopacity, setting time, pH, cytotoxicity, and antimicrobial activity. Iron disulfide nanostructures [with particle size of 0.357 ± 0.156 μm (mean ± SD)] at weight ratios of 0.2, 0.4, 0.6, 0.8, and 1.0 wt% were added to white MTA (wMTA). The radiopacity, rheological properties, setting time, and pH, as well as the cytotoxicity (assessed using the MTT assay) and antibacterial activity (assessed using the broth microdilution test) were determined for MTA/FeS₂ nanostructures. The nanostructures did not modify the radiopacity values of wMTA (~6 mm of aluminium); however, they reduced the setting time from 18.2 ± 3.20 min to 13.7 ± 1.8 min, and the storage modulus was indicative of a good stiffness. Whereas the wMTA/FeS₂ nanostructures did not induce cytotoxicity when in contact with human pulp cells (HPCs) and human gingival fibroblasts (HGFs), they showed bacteriostatic activity against Staphylococcus aureus, Escherichia coli, and Enterococcus faecalis. Adding FeS₂ nanostructures to MTA might be an option for improving the root canal sealing and antibacterial effects of wMTA in endodontic treatments.

Effects of ultraviolet irradiation on the bond strength of a composite resin adhered to stainless steel crowns

PURPOSE

A technique whereby the practitioner could improve the esthetic appearance of anterior stainless steel crowns (SSC) could provide a cost-effective alternative to more expensive commercially available preveneered SSCs, which may not be uniformly available. The purpose of this study was to evaluate the effects of ultraviolet (UV) irradiation of the metal crown surface on the shear bond strength of composite resin adhered to stainless steel crowns.

METHODS

Seventy extracted anterior bovine teeth randomly divided into 2 groups (n=35/group), were restored with primary maxillary left central incisor SSCs. Surface roughening with a green stone was performed on the labial surfaces, and the crowns of the experimental group were exposed to UV irradiation for 80 minutes. All samples were treated with metal-composite adhesive, followed by composite opaquer. Standardized composite blocks were bonded on the treated surfaces, and the shear bond strength was tested at 1 mm/minute. The values were recorded in MPa and statistically analyzed.

RESULTS

The mean value of shear bond strength was significantly higher for the experimental group (19.7 ± 4.3 MPa) than the control group (16.3 ± 4.5 MPa).

CONCLUSION

Ultraviolet irradiation of primary tooth stainless steel crowns significantly increased the shear bond strength of composite resin adhered to the facial surface.

Morphological features of osteoblasts cultured on ultraviolet-irradiated titanium plates

BACKGROUND

Although we have recently established optimal experimental conditions of ultraviolet (UV)-irradiation for titanium plates (e.g. wavelength and exposure time) which enhanced osteoblast adhesion to the plates, the effects of UV-irradiation on cell structure are still unclear.

MATERIALS AND METHODS

Digital stereomicroscopy was used to investigate morphological alterations of non-stained viable and hematoxylin-eosin (HE)-stained cells on UV-irradiated and non-UV-irradiated titanium plates for up to 24 hours.

RESULTS

In 24 hours, significant expansion of HE-stained cells (area, perimeter and sprouting processes) was observed on UV-irradiated plates. The sprouting processes appeared within 40 minutes of inoculation under both conditions, however, significant cell area expansion, which occurred in 5 minutes, was observed only on UV-irradiated plates.

CONCLUSION

UV-enhanced cell attachment was related to morphological alteration which occurred immediately after inoculation. Digital stereomicroscopic evaluation was able to define and quantify morphological alterations of viable cells in an opaque environment.