RESUMEN
AIMS: To develop novel polypropylene composite materials with antimicrobial activity by adding different types of copper nanoparticles. METHODS AND RESULTS: Copper metal (CuP) and copper oxide nanoparticles (CuOP) were embedded in a polypropylene (PP) matrix. These composites present strong antimicrobial behaviour against E. coli that depends on the contact time between the sample and the bacteria. After just 4 h of contact, these samples are able to kill more than 95% of the bacteria. CuOP fillers are much more effective eliminating bacteria than CuP fillers, showing that the antimicrobial property further depends on the type of copper particle. Cu²âº released from the bulk of the composite is responsible for this behaviour. Moreover, PP/CuOP composites present a higher release rate than PP/CuP composites in a short time, explaining the antimicrobial tendency. CONCLUSIONS: Polypropylene composites based on copper nanoparticles can kill E. coli bacteria depending on the release rate of Cu²âº from the bulk of the material. CuOP are more effective as antimicrobial filler than CuP. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings open up novel applications of these ion-copper-delivery plastic materials based on PP with embedded copper nanoparticles with great potential as antimicrobial agents.
Asunto(s)
Cobre/farmacología , Desinfectantes/farmacología , Escherichia coli/efectos de los fármacos , Nanopartículas del Metal/química , Polipropilenos/química , Cobre/química , Desinfectantes/química , Nanopartículas del Metal/ultraestructuraRESUMEN
In interventions aimed at the control of the immature stages of Aedes aegypti (L.), the principal vector of the dengue viruses, attempts are often made to treat or manage all larval habitats in households. When there are resource-constraints, however, a concentration of effort on the types of container that produce the most pupae may be required. Identification of these 'key' container types requires surveys of the immature stages and particularly - since these give the best estimates of the numbers of adults produced - of the numbers of pupae in local containers. Although there has been no clearly defined or standardized protocol for the sampling of Ae. aegypti pupae for many years, a methodology for 'pupal/demographic' surveys, which may allow the risk of dengue outbreaks in a given setting to be estimated, has been recently described. The consistency and practicality of using such surveys has now been investigated in three cities in the Mexican state of Chiapas, Mexico. Using a combination of 'quadrat'- and transect-sampling methods, 600 houses in each city were each sampled twice. Containers within each study household were searched for pupae and larvae. Although 107,297 containers, belonging to 26 categories, were observed, only 16,032 were found to contain water and 96% and 92% of these 'wet' containers contained no pupae and no third- or fourth-instar larvae, respectively. Although the random 'quadrat' sampling gave similar results to sampling along transects, there were statistically significant differences in the numbers of pupae according to container type and locality. The most important containers for pupal production were found to be large cement wash basins, which were present in almost every household investigated and from which 84% (10,257/12,271) of all pupae were collected. A focus on this class of container could serve as the basis of a targeted intervention strategy. When traditional Stegomyia indices were calculated they appeared to be correlated with the assessments of pupal abundance. The methodology for pupal/demographic surveys appears to be practical and to give consistent results, although it remains to be seen if monitoring of pupal productivity can adequately reflect the impact of vector-control interventions.
Asunto(s)
Aedes , Dengue , Insectos Vectores , Control de Mosquitos , Animales , Estudios Transversales , Dengue/epidemiología , Dengue/transmisión , Ecosistema , Artículos Domésticos , Humanos , Larva , Estudios Longitudinales , México/epidemiología , Vigilancia de la Población/métodos , Pupa , Reproducibilidad de los Resultados , Salud Urbana , Abastecimiento de AguaRESUMEN
Dengue fever is a serious problem in Mexico and vector control has not been effective enough at preventing outbreaks. Malaria is largely under control, but it is important that new control measures continue to be developed. Novaluron, a novel host-specific insect growth regulator and chitin synthesis inhibitor, has proved to be effective against agricultural pests, but its efficacy against larval mosquito vectors under field conditions remains unknown. In accordance with the World Health Organization Pesticide Evaluation Scheme, phase I, II and III studies were conducted to evaluate the efficacy and residual effect of Novaluron (Rimon 10 EC, Makhteshim, Beer-Sheva, Israel) on the malaria vectors Anopheles albimanus Wiedemann (Diptera: Culicidae) and Anopheles pseudopunctipennis Theobald, the dengue vectors Aedes aegypti (L) and Aedes albopictus Skuse and the nuisance mosquito Culex quinquefasciatus Say. Laboratory susceptibility tests yielded diagnostic concentrations for all five target species. Field trials to identify the optimum field dosage of Novaluron against Anopheles mosquitoes were carried out under semi-natural conditions in artificial plots and in vessels with wild mosquitoes. Efficacy was measured by monitoring mortality of larvae and pupae and the percentage of inhibition of emergence from floating cages. Dosages of Novaluron for field tests were based on pupal LC(99) (lethal concentration 99%) of An. pseudopunctipennis (0.166 mg/L) in plots and average pupal LC(99) of Ae. aegypti and Ae. albopictus (0.55 mg/L). At all dosages tested, Novaluron significantly reduced larval populations of An. albimanus, Culex coronator Dyar & Knab, Ae. albopictus and Cx. quinquefasciatus by approximately 90%, inhibited adult emergence of An. albimanus and An. pseudopunctipennis by approximately 97% for almost 4 months in experimental plots, and inhibited adult emergence of Ae. aegypti and Ae. albopictus by approximately 97% for up to 14 weeks. Recommended dosages of Novaluron for non-container breeding and container breeding mosquitoes are 0.166 mg/L and 0.55 mg/L, respectively. Overall, the residual effect was more sustained than that of temephos. The lowest dosage of Novaluron had less of an impact on non-target organisms than did temephos. Small-scale field trials in natural breeding sites treated with Novaluron at 0.6 L/ha eliminated adult emergence of An. albimanus and Cx. coronator for 8 weeks. For phase III studies, Novaluron was tested at the local and village levels, applying the optimum field rate to all natural breeding habitats within 1 km of a pair of neighbouring villages. Village-scale trials of Novaluron at 0.6 L/ha reduced An. albimanus larval populations for at least 8 weeks and, more importantly, sharply reduced the densities of adult host-seeking mosquitoes approaching houses. We conclude that Novaluron is effective and environmentally safer than temephos.