Preparation, properties and antibacterial applications of medical nano-metals and their oxides: a review / 生物工程学报

Antibiotics are playing an increasingly important role in clinical antibacterial applications. However, their abuse has also brought toxic and side effects, drug-resistant pathogens, decreased immunity and other problems. New antibacterial schemes in clinic are urgently needed. In recent years, nano-metals and their oxides have attracted wide attention due to their broad-spectrum antibacterial activity. Nano-silver, nano-copper, nano-zinc and their oxides are gradually applied in biomedical field. In this study, the classification and basic properties of nano-metallic materials such as conductivity, superplasticity, catalysis, and antibacterial activities were firstly introduced. Secondly, the common preparation techniques, including physical, chemical and biological methods, were summarized. Subsequently, four main antibacterial mechanisms, such as cell membrane, oxidative stress, DNA destruction and cell respiration reduction, were summarized. Finally, the effect of size, shape, concentration and surface chemical characteristics of nano-metals and their oxides on antibacterial effectiveness and the research status of biological safety such as cytotoxicity, genotoxicity and reproductive toxicity were reviewed. At present, although nano-metals and their oxides have been applied in medical antibacterial, cancer treatment and other clinical fields, some issues such as the development of green preparation technology, the understanding of antibacterial mechanism, the improvement of biosafety, and the expansion of application fields, require further exploration.

The toxicity of ZnO and CuO nanoparticles on biological wastewater treatment and its detoxification: a review / 生物工程学报

The wide use of ZnO and CuO nanoparticles in research, medicine, industry, and other fields has raised concerns about their biosafety. It is therefore unavoidable to be discharged into the sewage treatment system. Due to the unique physical and chemical properties of ZnO NPs and CuO NPs, it may be toxic to the members of the microbial community and their growth and metabolism, which in turn affects the stable operation of sewage nitrogen removal. This study summarizes the toxicity mechanism of two typical metal oxide nanoparticles (ZnO NPs and CuO NPs) to nitrogen removal microorganisms in sewage treatment systems. Furthermore, the factors affecting the cytotoxicity of metal oxide nanoparticles (MONPs) are summarized. This review aims to provide a theoretical basis and support for the future mitigating and emergent treatment of the adverse effects of nanoparticles on sewage treatment systems.

Rapid green synthesis of silver nano particles from Ziziphus mauritianaand antibacterial activity against human pathogens

A novel green source Ziziphus mauritiana fresh young leaves was opted to synthesize silver nanoparticles and analyze its antibacterial activity. The bioactive compounds present in the plant extracts reduced silver ions to NPs, indicated by change in colorfrom red to dark brown. In this study, we have successfully synthesized nanoparticles using Z.mauritiana aqueous leaf extract as a reducing agent and the reaction process of synthesized nanoparticles was monitored by UV-Vis spectroscopy. The UV-Vis absorption peak showed maximum adsorption at 420 nm confirmed the silver nanoparticles synthesis. Further characterization was carried out by FTIR and the results recorded a downward shift of absorption the bands between 400 to 4000 cm-1indicates the formationof silver nanoparticles. Finally, the present research was exploited to study the antibacterial activity of synthesized nanoparticles produced Z.mauritiana was studied using different pathogenic bacteria such as Salmonellasp., Proteus sp., Bacillus sp., Klebsiella pneumonia and E.colifrom the well diffusion results, the synthesized silver nanoparticles displayed the best antibacterial property as compared to the antibiotic has been reported in this paper. To the best of our knowledge, this is the first report that the Z.mauritiana aqueous extract facilitate the synthesis of silver nanoparticles and also exhibits antibacterial activity.

Inhibitory effect of reduced graphene oxide-silver nanocomposite on progression of artificial enamel caries

Abstract The use of antimicrobial agents is an efficient method to prevent dental caries. Also, nanometric antibacterial agents with wide antibacterial spectrum and strong antibacterial effects can be applied for prevention of dental caries. Objectives: The aim of this study was to evaluate the inhibitory effect of reduced graphene oxide-silver nanoparticles (rGO/Ag) composite on the progression of artificial enamel caries in a Streptococcus mutans biofilm model. Material and Methods: Enamel specimens from bovine incisors were divided into eight treatment groups (n = 13), as follows: group 1 was inoculated with S. mutans grown in Brain Heart Infusion containing 1% sucrose (1% BHIS), as negative control; groups 2-4 were inoculated with S. mutans grown in the presence of different rGO/Ag concentrations (0.08, 0.12, 0.16 mg/mL) + 1% BHIS; group 5-7 were inoculated with S. mutans grown in the presence of different agents (0.16 mg/mL reduced graphene oxide, 0.16 mg/mL silver nanoparticles, 10 ppm NaF) + 1% BHIS; group 8 was mixed with 1% BHIS, without inoculation. Artificial enamel carious lesions were produced by S. mutans biofilm model for 7 days. Confocal laser scanning microscopy and atomic force microscopy were used to analyze roughness and morphology of the enamel surface. Polarized light microscopy and confocal laser scanning microscopy were employed to measure the lesion depth and the relative optical density (ROD) of the demineralized layer. Results: Compared with the control groups, the rGO/Ag groups showed: (a) reduced enamel surface roughness; (b) much smoother and less eroded surfaces; (c) shallower lesion depth and less mineral loss. Conclusion: As a novel composite material, rGO/Ag can be a promising antibacterial agent for caries prevention.

The Effect of Ferrous Nano-oxide Particles on Physiological Traits and Nutritional Compounds of Soybean ( Glycine max L) Seed

ABSTRACT Soybean (Glycine max L.) seed contains amounts of protein, lipid, carbohydrate and mineral elements, which protein and lipid have been known as a main part for soybean's trade value. In this study, in order to investigate the effect of ferrous nano-oxide particles on nutritional compounds of soybean seed, an experiment with 5 treatments and 3 replications was conducted as a randomized complete block design. Treatments were 5 concentrations of ferrous nano-oxide particles including 0, 0.25, 0.5, 0.75 and 1 g L-1 which were sprayed 3 times at 4 and 8 leaves stage and pod initiation. Lipid and protein contents, fatty acids profile, some of mineral elements such as Fe, Mg, Ca and P, chlorophyll a, b and total chlorophyll content were determined. Results showed that solution containing ferrous nano-oxide particles had significant effect on nutritional compounds of soybean seed (P<0.01) compared to control. The highest content of lipid and protein (25.4 and %33.8, respectively) observed by applying 0.75 g L-1 of ferrous nano-oxide and the lowest content was also in control. Changes in the trends of fatty acids profile (palmitic, oleic, linoleic and linolenic acids), some of mineral elements (Fe, Mg, Ca and P) and chlorophyll contents were similar to lipid and protein levels which by increasing in concentration of ferrous nano-oxide from 0 to 0.75 g L-1 all measured parameters also increased, but reduction in all parameters was observed in concentration from 0.75 to 1 g L-1. In conclusion, application of 0.75 to 1 g L-1 ferrous nano-oxide had the best effect on the nutrient composition of soybean seed.

AgNPs: The New Allies Against S. Mutans Biofilm - A Pilot Clinical Trial and Microbiological Assay

Abstract: The purpose of this study was to evaluate the antimicrobial properties of a new formulation containing silver nanoparticles, named Nano Silver Fluoride (NSF), to inhibit Streptococcus mutans biofilm formation on children's dental enamel. The variations in dental biofilm pH and in the Simplified-Oral-Hygiene-Index (OHI-S) also were evaluated after the treatment with NSF. This was a randomized, double-blind, crossover and prospective pilot clinical trial study in which 12 schoolchildren, aged between 7-8 years, had their dental enamel treated with two solutions: S1 - Nano Silver Fluoride and S2 - negative control (saline solution), in different experimental moments. The dental biofilm adhered to enamel treated with NSF had lower values of S. mutans viability (absorbance) and colony forming units (CFU) than the S0 (baseline) and S2. There was a statistically significant difference between the OHI-S mean values of S0 and S1. There were no differences between the biofilm pH (both before and after the use of the test substances) and among the different groups. These properties suggest that NSF has bactericidal effect against S. mutans biofilm and it may be used for clinical control and prevention of dental biofilm formation.

Resumo O objetivo do presente estudo foi avaliar as propriedades antimicrobianas de uma nova formulação composta por nanopartículas de prata, denominada nano silver fluoride (NSF), na inibição de biofilme de Streptococcus mutans sobre a superfície do esmalte dentário de crianças. Variações no pH do biofilme dental e nos valores do índice de Higiene Oral Simplificada (IHO-S) também foram avaliadas após o tratamento com NSF. Trata-se de um estudo piloto, randomizado, duplo cego, cruzado e prospectivo. A amostra foi composta por 12 crianças, de ambos os gêneros, com idades entre 7 e 8 anos, as quais utilizaram as duas soluções testes, S1- NSF e S2- controle negativo (solução salina). O biofilme dental tratado com NSF apresentou menores valores de viabilidade de S. mutans (absorbância) e de unidades formadoras de colônias (UFC) do que o biofilme baseline e o biofilme tratado com S2. Houve diferença estatisticamente significativa entre os valores médios de IHO-S dos grupos baseline e S1, com uma redução dos valores. Não houve qualquer variação nos valores de pH do biofilme dental, antes e depois do tratamento com S1 e S2 e entre os diferentes grupos. Estas propriedades sugerem que NSF possui efeito bactericida sobre o biofilme de S. mutans, podendo ser utilizado clinicamente para o controle e prevenção da formação do biofilme dentário.

Biosynthesized silver nanoparticles: are they effective antimicrobials?

BACKGROUND Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required. OBJECTIVES This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853. METHODS Culture conditions (AgNO3 concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy. FINDINGS The characteristic UV-visible absorbance peak was observed in the 420-430 nm range. Most of the particles were spherical in shape within a size range of 33-300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans. MAIN CONCLUSION As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

The effect of silver nanoparticles on composite shear bond strength to dentin with different adhesion protocols

Abstract In Dentistry, restorative materials and oral bacteria are believed to be responsible for restoration failure. To make long-lasting restorations, antibacterial agents should be made. Inorganic nanoparticles and their nano composites are applied as good antibacterial agents. Objective The purpose of this study was to investigate the effect of silver nanoparticles on composite shear bond strength using one etch and rinse and one self-etch adhesive systems. Material and Methods Silver nanoparticles were prepared. Transmission electron microscope and X-ray diffraction were used to characterize the structure of the particles. Nanoparticles were applied on exposed dentin and then different adhesives and composites were applied. All samples were tested by universal testing machine and shear bond strength was assesed. Results Particles with average diameter of about 20 nm and spherical shape were found. Moreover, it was shown that pretreatment by silver nanoparticles enhanced shear bond strength in both etch and rinse, and in self-etch adhesive systems (p≤0.05). Conclusions Considering the positive antibacterial effects of silver nanoparticles, using them is recommended in restorative dentistry. It seems that silver nanoparticles could have positive effects on bond strength of both etch-and-rinse and self-etch adhesive systems. The best results of silver nanoparticles have been achieved with Adper Single Bond and before acid etching.

Evaluation of methods for removal of filling material in endodontic retreatment and assessment of antimicrobial action of solutions used in final irrigation / Avaliação de métodos de desobturação do canal radicular no retratamento endodôntico e avaliação da ação antimicrobiana de soluções utilizadas na irrigação final

When endodontic treatment fails, an alternative could be root canal retreatment. During this procedure, all filling material should be removed to allow a new root canal preparation and new obturation of the root canal system. Bacteria are the main cause of endodontic treatment failure, and persistent infection may be related to microorganism ability to penetrate into dentinal tubules. Therefore, this requires the use of irrigating solutions with antimicrobial action and low toxicity. The aim of this study was to evaluate the performance of instruments made of different alloys in root canal re-instrumentation during endodontic retreatment of lateral incisors with apical curvature, using computed microtomography and assessment of these samples by scanning electron microscopy after irrigant activation. Furthermore, the antimicrobial action of a root canal irrigant containing silver nanoparticles, 2% chlorhexidine and 2.5% sodium hypochlorite was evaluated against Enterococcus faecalis biofilm and dentin infected with this microorganism. Thirty extracted maxillary lateral incisors with apical curvature were selected. The teeth were instrumented, filled and divided into three different groups according to the protocol for removal of filling material: Group 1: re-instrumentation with Reciproc R25 instruments, Mtwo 40 and ProDesign Logic 50.01; Group 2: re-instrumentation with ProDesign R, ProDesign Logic 40 and ProDesign Logic 50.01; Group 3: re-instrumentation with Gates-Glidden drills and manual instruments K-file and Hedstroem files. For filling material removal analysis, the samples were scanned in a microtomograph device SkyScan 1174, for comparison of images taken before and after removing the root canal filling, and in each sample the volume was calculated at four levels (apical 1, apical 2, middle and cervical). These samples were split and analyzed by scanning electron microscopy to visualize filling material residues before and after irrigant activation with an ultrasonic device and with the EasyClean system used in continuous rotary motion. Statistical analyses were performed using Kruskal-Wallis, Friedman, Wilcoxon and Dunn tests. Furthermore, the minimum inhibitory concentration of an irrigating solution containing silver nanoparticles was determined against strains of Enterococcus faecalis, by using the microdilution method. Additionally, the antimicrobial activity of silver nanoparticle solution, 2% chlorhexidine and 2.5% sodium hypochlorite was tested against Enterococcus faecalis biofilm in vitro. For biofilm formation, bovine dentin blocks were placed in 24-well culture plates and Enterococcus faecalis biofilm was developed for 21 days. The dentin blocks were divided into 9 experimental groups of 5 blocks each, according to the irrigating solution used and the time in contact with the irrigant (5, 15 and 30 minutes). The samples were stained with Live/Dead reagent for analysis by confocal laser scanning microscopy (CLSM). Finally, the antimicrobial action of these solutions was tested after dentinal tubules were contaminated with Enterococcus faecalis. Dentin tubes were made from bovine incisors, taken to a centrifuge and infected with Enterococcus faecalis. The dentin tubes were treated with silver nanoparticle solution, 2% chlorhexidine and 2.5% sodium hypochlorite, and analyzed by CLSM to assess the antimicrobial activity of these solutions against bacteria in the dentinal tubules. The results showed that residues of filling material were found after root canal reinstrumentation in all groups. No significant difference was observed in removal of filling material between the reciprocating instruments Reciproc and ProDesign R and between rotary instruments Mtwo 40 and ProDesign Logic 40. The ProDesign Logic 50/.01 instrument significantly improved the removal of filling material compared with the use of Reciproc and ProDesign R instruments. The apical levels presented greater amount of remnant filling material compared with middle and cervical levels. After canal reinstrumentation, the passive ultrasonic irrigation and irrigant agitation with EasyClean significantly improved the removal of residual filling material in all root canal thirds. There was no significant difference between the performance of ultrasonics and EasyClean regarding the removal of residual filling material, as well no significant difference was observed in the removal of these residues when comparing apical, middle and cervical thirds. Regarding the action of the irrigating solutions against Enterococcus faecalis, the minimum inhibitory concentration of silver nanoparticle solution capable of eliminating this microorganism in broth and agar plates was 94 ppm. After the irrigation of Enterococcus faecalis biofilm, the silver nanoparticle solution was significantly less effective in killing bacteria compared with chlorhexidine when used for time of contact of 5 minutes. The sodium hypochlorite solution presented antimicrobial activity significantly higher compared with the silver nanoparticle solution and chlorhexidine. This solution also presented higher ability to dissolve biofilm in all times tested, whereas the silver nanoparticle solution presented higher ability to dissolve biofilm compared with chlorhexidine in times of 5 and 15 minutes. In infected intratubular dentin with Enterococcus faecalis, the sodium hypochlorite solution presented significant higher effectiveness than the silver nanoparticle solutions and chlorhexidine, especially in middle third and deep areas of the root canal. When comparing the antimicrobial activity of these solutions in biofilm and infected intratubular dentin, it was shown that when the silver nanoparticle solution was used for shorter periods of time, it was more effective in intratubular dentin compared with biofilm. On the other hand, with longer time of 30 minutes, the number of viable bacteria was higher in intratubular dentin than in biofilm, which was also observed when using the sodium hypochlorite solution in this time of action. It was concluded that to increase the rate of success in endodontic retreatment, the combination of the use of reciprocating and rotary instruments in the removal of filling material, the agitation of irrigants and the use of antimicrobial agents could be used in an attempt to eliminate bacteria that resisted to endodontic treatment. (AU)

Em casos de insucesso do tratamento endodôntico, uma alternativa seria o retratamento do canal radicular. Durante este procedimento deve haver remoção de todo o material obturador para que seja realizada novo preparo biomecânico e nova obturação do sistema de canais radiculares. Bactérias são o principal fator etiológico em casos de fracasso da terapia endodôntica, e esta infecção persistente pode estar relacionada à capacidade dos microganismos em penetrar nos túbulos dentinários. Por este motivo é necessário o uso de soluções na irrigação do canal radicular com ação antimicrobiana e com boa tolerância tecidual. O objetivo deste trabalho foi avaliar o desempenho dos instrumentos de diferentes ligas metálicas na desobturação do canal radicular durante o retratamento endodôntico de incisivos laterais superiores com curvatura apical, por meio da microtomografia computadorizada e análise destas amostras no microscópio eletrônico de varredura após a ativação de irrigantes. Posteriormente foi avaliada a capacidade antimicrobiana de um irrigante do canal radicular contendo nanopartículas de prata, clorexidina a 2% e hipoclorito de sódio a 2,5% frente ao biofilme de Enterococcus faecalis e à dentina contaminada com este mesmo microrganismo. Foram selecionados trinta incisivos laterais superiores humanos extraídos que apresentavam curvatura apical. Os dentes foram instrumentados, obturados e divididos em três diferentes grupos de acordo com o protocolo de remoção do material obturador do canal radicular: no Grupo 1: a desobturação foi realizada com os instrumentos Reciproc R25, Mtwo 40 e ProDesign Logic 50.01; no Grupo 2: foram utilizados os instrumentos ProDesign R, ProDesign Logic 40 e ProDesign Logic 50.01; e no Grupo 3: a desobturação foi realizada com brocas de Gates-Glidden e instrumentos manuais tipo K e Hedstroem. Para a análise da remoção do material obturador, as amostras foram escaneadas em micrótomogafo SkyScan 1174 para que fossem comparadas as imagens antes e após a desobturação do canal radicular, e em cada amostra este volume foi calculado nos quatro níveis (apical 1, 2, médio e cervical). Estas amostras posteriormente foram clivadas e analisadas no microscópio eletrônico de varredura, para a visualização de resíduos de material obturador antes e após a ativação de irrigantes com o ultrassom e com o sistema EasyClean utilizado em rotação contínua. Para a análise estatística dos resultados foram utilizados os testes de Kruskal-Wallis, Friedman, Wilcoxon e Dunn. Posteriormente, foi determinada a concentração inibitória mínima de uma solução irrigadora do canal contendo nanopartículas de prata frente a cepas de Enterococcus faecalis, através do método de diluição em caldo. Em seguida, foi testada a atividade antimicrobiana das soluções de nanopartículas de prata, da clorexidina a 2% e do hipoclorito de sódio a 2,5% sobre o biofilme de Enterococcus faecalis in vitro. Para isso, foram utilizados blocos de dentina bovina colocados em placas de 24 poços e biofilme de Enterococcus faecalis foi formado durante 21 dias. Os blocos de dentina foram divididos em 9 grupos experimentais com 5 blocos cada um, em função dos irrigantes avaliados e do tempo de exposição à solução irrigadora (5, 10 e 15 minutos). As amostras foram coradas com corante Live/Dead para posterior análise no microscópio confocal de varredura a laser (MCVL). Por fim, foi testada a atividade antimicrobiana destas soluções irrigadoras após a contaminação de túbulos dentinários com Enterococcus faecalis. Foram confeccionados tubos de dentina a partir de incisivos bovinos que foram levados à centrífuga e contaminados com Enterococcus faecalis. Os tubos de dentina receberam tratamento com a solução de nanopartículas de prata, com clorexidina a 2% e com hipoclorito de sódio a 2,5%, e foram analisados no MCVL para avaliar a atividade antimicrobiana das soluções sobre bactérias presentes nos túbulos dentinários. Os resultados demonstraram que resíduos de material obturador foram encontrados após a desobturação do canal em todos os grupos. Não houve diferença significante na remoção de material obturador entre os instrumentos reciprocantes Reciproc e ProDesign R e entre os instrumentos rotatórios Mtwo 40 e ProDesign Logic 40. O instrumento ProDesign Logic 50/.01 melhorou significantemente a remoção de material obturador comparado com o uso dos instrumentos Reciproc e ProDesign R. Os níveis apicais apresentaram uma maior quantidade de material obturador remanescente comparados com os níveis médio e cervical. Após a desobturação do canal radicular, a irrigação ultrassônica passiva e agitação dos irrigantes com o EasyClean melhoraram significantemente a remoção de resíduos de material obturador em todos os terços do canal radicular. Não houve diferença significante no desempenho do ultrassom e do EasyClean em relação à remoção de resíduos de material obturador, assim como não foi observada diferença significante na remoção destes resíduos quando comparados terços apical, médio e cervical. No que diz respeito à ação das soluções irrigadoras sobre o Enterococcus faecalis, a concentração inibitória mínima da solução de nanopartículas de prata capaz de eliminar este microrganimo em meio de cultura e ágar foi de 94 ppm. Após a irrigação no biofilme de Enterococcus faecalis, a solução de nanopartículas de prata foi significantemente menos efetiva em matar bactérias comparada com a clorexidina quando utilizadas pelo tempo de 5 minutos. A solução de hipoclorito de sódio apresentou atividade antimicrobiana significantemente maior comparada com as soluções de nanopartículas de prata e clorexidina. Essa solução ainda apresentou maior capacidade de dissolução do biofilme em todos os tempos testados, enquanto que a solução de nanopartículas de prata apresentou maior capacidade de dissolver o biofilme comparada à clorexidina nos tempos de 5 e 15 minutos. Na dentina intratubular infectada com Enterococcus faecalis, a solução de hipoclorito de sódio apresentou efetividade significantemente maior que as soluções de nanopartículas de prata e clorexidina, principalmente no terço médio e na região profunda do canal radicular. Quando comparada a atividade antimicrobiana destas soluções no biofilme e na dentina intratubular infectada, verificou-se que quando a solução de nanopartículas de prata foi utilizada por um tempo mais curto, foi mais efetiva na dentina intratubular comparada com o biofilme. De maneira contrária, com tempo maior de 30 minutos, o número e bactérias viáveis foi maior na dentina intratubular do que no biofilme, o que ocorreu também com a solução de hipoclorito de sódio neste tempo de ação. Conclui-se que para se aumentar a chance de sucesso em tratamentos retratamentos endodônticos, a combinação do uso de instrumentos reciprocantes e rotatórios na desobturação do canal, agitação de irrigantes e uso de agentes com capacidade antimicrobiana podem ser utilizados na tentativa de se eliminar bactérias resistente ao tratamento endodôntico. (AU)

Copper nanoparticles as potential antimicrobial agent in disinfecting root canals: a systematic review / Nanopartículas de cobre como potencial agente antimicrobiano en la desinfección de canales radiculares: revisión sistemática

Copper was registered as the first solid antimicrobial material. Its availability makes it an important option as an antibacterial agent. At nanoparticle size it does not exceed 100 nm, allowing close interaction with microbial membranes, enhancing its effect even more. Copper generates toxic hydroxyl radicals that damage cell membranes of Gram-negative and Gram-positive bacteria, among the latter, Enterococcus faecalis, which are present in infected radicular canals. Synthesis of metal nanoparticles with antimicrobial properties has become a viable alternative and has promising applications in the fight against pathogenic microorganisms. Furthermore, the use of some polymers to stabilize nanoparticles increases their release time and may as well decrease the risk of bacterial recolonization and biofilm formation within the ducts, enhancing the antimicrobial properties of these compounds.The aim of this article is to conduct a systematic review of the literature on antimicrobial copper nanoparticles, their current applications and their potential use in the area of oral health, specifically in the field of endodontics.

El cobre fue registrado como el primer material antimicrobiano sólido y su disponibilidad permite que constituya una importante opción como agente antibacteriano. Al tamaño de nanopartícula no supera los 100 nm, lo que permite una interacción estrecha con las membranas microbianas, potenciando aún más su efecto. Genera radicales hidroxilos tóxicos que provocan daño en la membrana celular de bacterias Gram negativas y Gram positivas, entre estas últimas, Enterococcus faecalis, presente en conductos radiculares infectados. Por lo que la síntesis de nanopartículas metálicas con propiedades antimicrobianas se ha vuelto una alternativa viable con aplicaciones prometedoras en la lucha contra microorganismos patógenos. Además, utilizando algunos polímeros para estabilizar las nanopartículas se aumenta el tiempo de liberación de éstas y se disminuye el riesgo de recolonización bacteriana y la formación de biopelículas al interior de los conductos, mejorando las propiedades antimicrobianas de estos compuestos. El propósito de este artículo es realizar una revisión sistemática de la literatura acerca de nanopartículas de cobre como antimicrobiano, sus aplicaciones actuales y su potencial uso en el área de la salud oral, específicamente en el campo de la Endodoncia.

Silver nanoparticle incorporation effect on mechanical and thermal properties of denture base acrylic resins

ABSTRACT Objective The aim of the present study was to evaluate the mechanical and thermal characteristics of two denture base acrylic resins containing silver nanoparticles (AgNPs). Material and Methods Two different acrylic denture base resins (heat-polymerized and microwave polymerized) containing 0.3, 0.8 and 1.6 wt% AgNPs were evaluated for flexural strength, elastic modulus and impact strength. The glass transition temperature (Tg) and relative heat capacity (Cp) of the samples were determined from the Differential Scanning Calorimetry (DSC) results. For statistical analysis, two-way ANOVA and Tukey-HSD tests were performed. Results Addition of 0.8% and 1.6% AgNPs in microwave-polymerized resin significantly decreased the transverse strength and elastic modulus. In terms of impact strength, the addition of AgNPs has no effect on both resin groups. Glass transition temperature (Tg) was decreased with the addition of AgNPs for both denture base resins. Conclusions The incorporation of AgNPs, generally used for antimicrobial efficiency, affected the transverse strength of the denture base acrylic resins depending on the concentration of nanoparticles. Tg was decreased with the addition of AgNPs for both denture base resins.

Effect of silver nanoparticles on the physicochemical and antimicrobial properties of an orthodontic adhesive

ABSTRACT Orthodontic treatment with fixed brackets plays a major role on the formation of white spot lesions. Objective This study aimed to incorporate silver nanoparticle solutions (AgNP) in an orthodontic adhesive and evaluate its physicochemical and antimicrobial properties. Material and Methods Silver nanoparticle solutions were added to a commercial adhesive in different concentrations (w/w): 0%, 0.11%, 0.18%, and 0.33%. Shear bond strength (SBS) test was performed after bonding metal brackets to enamel. Raman spectroscopy was used to analyze in situ the degree of conversion (DC) of the adhesive layer. The surface free energy (SFE) was evaluated after the measurement of contact angles. Growth inhibition of Streptococcus mutans in liquid and solid media was determined by colony-forming unit count and inhibition halo, respectively. One-way ANOVA was performed for SBS, DC, SFE, and growth inhibition. Results The incorporation of AgNP solution decreased the SBS (p<0.001) and DC in situ (p<0.001) values. SFE decreased after addition of 0.18% and 0.33% AgNP. Growth inhibition of S. mutans in liquid media was obtained after silver addition (p<0.05). Conclusions The addition of AgNP solutions to Transbond™ XT adhesive primer inhibited S. mutans growth. SBS, DC, and SFE values decreased after incorporation up to 0.33% AgNP solution without compromising the chemical and physical properties of the adhesive.

Undergraduate dental sudents' perspectives about experiences in primary care for their education in the field of health / Perspectivas de graduandos em odontologia acerca das experiências na atenção básica para sua formação em saúde

Supervised training periods in primary care have been used as spaces for teaching and extension in the area of health, making it feasible to include undergraduates in concrete teaching-learning scenarios. The aim of this study was to analyze the perceptions of dental students about the importance of supervised training periods in Family Health Units to their professional education. The sample consisted of 185 students who answered the question: What is your opinion about the importance of this training period in SUS to your professional education? Comment on this experience and its positive and negative aspects The responses were analyzed by the quali-quantitative Collective Subject Discourse (CSD) technique. The students appreciated learning through practice in the service; contact with professionals from other areas; opportunity for technical-operative improvement and demonstrated sensitivity in the face of social reality, although they appeared to be concerned about being absent from the faculty, arguing that they were being prejudiced as regards their intramural clinical productivity, exhaustively demanded of them. It was concluded that students placed value on the extramural experience, however, it was perceived that there was still a predominant influence of focus on intramural clinical training.

Os estágios supervisionados na atenção básica vêm sendo utilizados como espaços de ensino e extensão nas áreas da saúde, viabilizando a inserção dos graduandos em cenários concretos de ensino-aprendizagem. O objetivo deste estudo foi analisar as percepções de acadêmicos de odontologia sobre a importância do estágio supervisionado em Unidades de Saúde da Família, para sua formação profissional. A amostra foi constituída por 184 acadêmicos que responderam à questão: Qual a sua opinião em relação à importância deste estágio no SUS para a sua formação profissional? Comente esta experiência e seus aspectos positivos e negativos. As respostas foram analisadas através da técnica qualiquantitativa do discurso do sujeito coletivo. Os alunos valorizaram o aprendizado através da prática no serviço, do contato com profissionais de outras áreas, da oportunidade de aperfeiçoamento técnico-operatório e demonstraram sensibilização frente à realidade social, embora tenham aparentado incômodo por se ausentarem da faculdade, sob o argumento de serem prejudicados quanto à produtividade da clínica intramuros, exaustivamente cobrada. Concluiu-se que os alunos valorizaram a experiência extramural, entretanto, percebeu-se que ainda há uma hegemonia do foco no treinamento clínico intramuros.

Más que curar, prevenir: surgimiento y primera etapa de los Centros de Higiene Infantil en la Ciudad de México, 1922-1932 / Prevention rather than cure: the emergence and first stage of the Centros de Higiene Infantil in Mexico City, 1922-1932

Este trabajo aborda las principales características del surgimiento y primeros diez años de funcionamiento de los Centros de Higiene Infantil, establecimientos dependientes del Departamento de Salubridad Pública desde 1922 en la Ciudad de México y que tuvieron como objetivo atender a las madres, desde el periodo de gestación, y a los niños, desde el nacimiento hasta los dos años de edad. Revisa las acciones que dieron origen a este proyecto y su consolidación. Analiza la estructura de estos Centros, las características de las madres y los niños que atendieron, así como las funciones que realizaron médicos y enfermeras enfatizando la noción de prevención de las enfermedades infantiles, para finalmente mostrar un primer balance acerca de los alcances y limitaciones que tuvieron.

This article deals with the main features of the emergence and first ten years of the Centros de Higiene Infantil, facilities run by the Departamento de Salubridad Pública from 1922 on in Mexico City with the goal of providing care for mothers from pregnancy onwards and children from birth to two years of age. It reviews the actions that gave rise to this project and how it became established. It analyzes the structure of these centers, the characteristics of the mothers and children seen there and the functions performed by doctors and nurses, stressing the notion of preventing childhood illnesses, and ends with a first assessment of the effects and limitations of these centers.

Highly Sensitive and Novel Point-of-Care System, aQcare Chlamydia TRF Kit for Detecting Chlamydia trachomatis by Using Europium (Eu) (III) Chelated Nanoparticles

BACKGROUND: The bacterium Chlamydia trachomatis is one of the leading causes of sexually transmitted diseases worldwide. Since no simple and effective tool exists to diagnose C. trachomatis infections, we evaluated a novel point-of-care (POC) test, aQcare Chlamydia TRF kit, which uses europium-chelated nanoparticles and a time-resolved fluorescence reader. METHODS: The test performance was evaluated by comparing the results obtained using the novel POC testing kit with those obtained using a nucleic acid amplification test (NAAT), using 114 NAAT-positive and 327 NAAT-negative samples. RESULTS: The cut-off value of the novel test was 20.8 with a detection limit of 0.27 ng/mL. No interference or cross-reactivity was observed. Diagnostic accuracy showed an overall sensitivity of 93.0% (106/114), specificity of 96.3% (315/327), positive predictive value (PPV) of 89.8% (106/118), and negative predictive value (NPV) of 97.5% (315/323). The sensitivity of the novel test was much higher than that of currently available POC tests. Furthermore, the relative ease and short turnaround time (30 min) of this assay enables C. trachomatis-infected individuals to be treated without a diagnostic delay. CONCLUSIONS: This simple and novel test is a potential tool to screen a larger population, especially those in areas with limited resources.

Size Control of 99mTc-tin Colloid Using PVP and Buffer Solution for Sentinel Lymph Node Detection

Colloidal particle size is an important characteristic that allows mapping sentinel nodes in lymphoscintigraphy. This investigation aimed to introduce different ways of making a 99mTc-tin colloid with a size of tens of nanometers. All agents, tin fluoride, sodium fluoride, poloxamer-188, and polyvinylpyrrolidone (PVP), were mixed and labeled with 99mTc. Either phosphate or sodium bicarbonate buffers were used to adjust the pH levels. When the buffers were added, the size of the colloids increased. However, as the PVP continued to increase, the size of the colloids was controlled to within tens of nanometers. In all samples, phosphate buffer added PVP (30 mg) stabilized tin colloid (99mTc-PPTC-30) and sodium bicarbonate solution added PVP (50 mg) stabilized tin colloid (99mTc-BPTC-50) were chosen for in vitro and in vivo studies. 99mTc-BPTC-50 (100 nm) mainly accumulated in the liver. When a rabbit was given a toe injection, the node uptake of 99mTc-PPTC-30 decreased over time, while 99mTc-BPTC-50 increased. Therefore, 99mTc-BPTC-50 could be a good candidate radiopharmaceutical for sentinel node detection. The significance of this study is that nano-sized tin colloid can be made very easily and quickly by PVP.

Exposure to Cerium Oxide Nanoparticles Is Associated With Activation of Mitogen-activated Protein Kinases Signaling and Apoptosis in Rat Lungs / 예방의학회지

OBJECTIVES: With recent advances in nanoparticle manufacturing and applications, potential exposure to nanoparticles in various settings is becoming increasing likely. No investigation has yet been performed to assess whether respiratory tract exposure to cerium oxide (CeO2) nanoparticles is associated with alterations in protein signaling, inflammation, and apoptosis in rat lungs. METHODS: Specific-pathogen-free male Sprague-Dawley rats were instilled with either vehicle (saline) or CeO2 nanoparticles at a dosage of 7.0 mg/kg and euthanized 1, 3, 14, 28, 56, or 90 days after exposure. Lung tissues were collected and evaluated for the expression of proteins associated with inflammation and cellular apoptosis. RESULTS: No change in lung weight was detected over the course of the study; however, cerium accumulation in the lungs, gross histological changes, an increased Bax to Bcl-2 ratio, elevated cleaved caspase-3 protein levels, increased phosphorylation of p38 MAPK, and diminished phosphorylation of ERK-1/2-MAPK were detected after CeO2 instillation (p<0.05). CONCLUSIONS: Taken together, these data suggest that high-dose respiratory exposure to CeO2 nanoparticles is associated with lung inflammation, the activation of signaling protein kinases, and cellular apoptosis, which may be indicative of a long-term localized inflammatory response.

Nano gold conjugation, anti-arthritic potential and toxicity studies of snake Naja kaouthia (Lesson, 1831) venom protein toxin NKCT1 in male albino rats and mice.

Nanoscience and Nanotechnology have found their way in the fields of pharmacology and medicine. The conjugation of drug to nanoparticles combines the properties of both. In this study, gold nanoparticle (GNP) was conjugated with NKCT1, a cytotoxic protein toxin from Indian cobra venom for evaluation of anti-arthritic activity and toxicity in experimental animal models. GNP conjugated NKCT1 (GNP-NKCT1) synthesized by NaBH4 reduction method was stable at room temperature (25±2 °C), pH 7.2. Hydrodynamic size of GNP-NKCT1 was 68–122 nm. Arthritis was developed by Freund's complete adjuvant induction in male albino rats and treatment was done with NKCT1/GNP-NKCT1/standard drug. The paw/ankle swelling, urinary markers, serum markers and cytokines were changed significantly in arthritic control rats which were restored after GNP-NKCT1 treatment. Acute toxicity study revealed that GNP conjugation increased the minimum lethal dose value of NKCT1 and partially reduced the NKCT1 induced increase of the serum biochemical tissue injury markers. Histopathological study showed partial restoration of toxic effect in kidney tissue after GNP conjugation. Normal lymphocyte count in culture was in the order of GNP-NKCT1>NKCT1>Indomethacine treatment. The present study confirmed that GNP conjugation increased the antiarthritic activity and decreased toxicity profile of NKCT1.

Synthesis of silver nanoparticles using a biosurfactant produced in low-cost medium as stabilizing agent

Background A biosurfactant produced by Pseudomonas aeruginosa cultivated in a low-cost medium formulated with 2.5% vegetable oil refinery residue and 2.5% corn steep liquor and distilled water was employed to stabilize silver nanoparticles in the liquid phase. The particles were initially synthesized using NaBH4 as reducing agent in biosurfactant reverse micelles and were extracted from the micellar solution to disperse in heptane. Results A silver particle size in the range of 1.13 nm was observed. The UV-vis absorption spectra proposed that silver nanoparticles could be formed in the reverse micelles and relatively stabilized for at least 3 months without passivator addition. The Transmission Electron Microscope (TEM) shows that the silver nanoparticles are of spherical form and relatively uniform. Conclusions This process provided a simpler route for nanoparticle synthesis compared to existing systems using whole organisms or partially purified biological extracts, showing that the low-cost biosurfactant can be used for nanoparticle synthesis as a non-toxic and biodegradable stabilizing agent.

Biosynthesis of silver nanoparticles using fresh extracts of Tridax procumbens Linn.

A simple and eco-friendly method for the synthesis of biogenic nanoparticles (NP’s) using an aqueous solution of T. procumbens fresh plant extract (leaf and stem) as a bioreductant is reported. The prepared biogenic nanoparticles were well characterized using U.V. visible spectroscopy, scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. The particles were confirmed to be elemental crystal by X-ray diffraction. The potential applications of biosynthesized nanoparticles as antimicrobial (antibacterial and antifungal) against pathogens Escherichia coli, Vibrio cholerae, Aspergillus niger and Aspergillus flavus were demonstrated.