Methylene blue@silver nanoprisms conjugates as a strategy against Candida albicans isolated from balanoposthitis using photodynamic inactivation.

Balanoposthitis can affect men in immunocompromised situations, such as HIV infection and diabetes. The main associated microorganism is Candida albicans, which can cause local lesions, such as the development of skin cracks associated with itching. As an alternative to conventional treatment, there is a growing interest in the photodynamic inactivation (PDI). It has been shown that the association of photosensitizers with metallic nanoparticles may improve the effectiveness of PDI via plasmonic effect. We have recently shown that the association of methylene blue (MB), a very known photosensitizer, with silver prismatic nanoplatelets (AgNPrs) improved PDI of a resistant strain of Staphylococcus aureus. To further investigate the experimental conditions involved in PDI improvement, in the present study, we studied the effect of MB concentration associated with AgNPrs exploring spectral analysis, zeta potential measurements, and biological assays, testing the conjugated system against C. albicans isolated from a resistant strain of balanoposthitis. The AgNPrs were synthesized through silver anisotropic seed growth induced by the anionic stabilizing agent poly(sodium 4-styrenesulfonate) and showed a plasmon band fully overlapping the MB absorption band. MB and AgNPrs were conjugated through electrostatic association and three different MB concentrations were tested in the nanosystems. Inactivation using red LED light (660 nm) showed a dose dependency in respect to the MB concentration in the conjugates. Using the highest MB concentration (100 µmol⋅L-1) with AgNPr, it was possible to completely inactivate the microorganisms upon a 2 min irradiation exposure. Analyzing optical changes in the conjugates we suggest that these results indicate that AgNPrs are enhancers of MB photodynamic action probably by a combined mechanism of plasmonic effect and reduction of MB dimerization. Therefore, MBAgNPrs can be considered a suitable choice to be applied in PDI of resistant microorganisms.

Maternal identification of dental caries lesions in their children aged 1-3 years.

AIM: To analyse the maternal identification of different stages of dental caries in children aged 1-3 years. METHODS: A cross-sectional study was conducted with 274 children and their mothers. The mothers answered a questionnaire on the occurrence of dental caries in their children and completed questions addressing their demographic/socio-economic status. The oral examination of the children was performed using the International Caries Detection and Assessment System. Descriptive, Chi square test and Poisson regression statistical analyses were performed. RESULTS: The prevalence of initial and established/severe dental caries lesions by age were: 1 year (23.2 and 24.2%), 2 years (17.9 and 55.7%) and 3 years (23.3 and 60.3%) respectively. Significant associations between clinical examinations and the mothers' reports were observed among children aged 1 year old who had initial stage caries lesions (p = 0.006) and in children aged 1, 2 and 3 years old who had established/severe stage caries lesions (p < 0.001). After adjustment for confounding variables it was found that mothers were more able to identify dental caries both at initial (PR 4.01, 95% CI 1.35-11.94) and established/severe stages (PR 9.14, 95% CI 2.49-33.56) in children aged 1 year old. In children aged 2 and 3 years, this identification was more evident in the established/severe stage (2 years, PR 2.98, 95% CI 1.42-6.26; 3 years, PR 2.75, 95% CI 1.09-6.93). CONCLUSIONS: Mothers of children aged 1 year old identified dental caries at initial and established/severe stages. Mothers of children aged 2 and 3 years identified dental caries only at established/severe stages.