Mosquito‐repellent controlled‐release formulations for fighting infectious diseases

Malaria is a principal cause of illness and death in countries where the disease is endemic. Personal protection against mosquitoes using repellents could be a useful method that can reduce and/or prevent transmission of mosquitoborne diseases. The available repellent products, such as creams, roll-ons, and sprays for personal protection against mosquitoes, lack adequate long-term efficacy. In most cases, they need to be re-applied or replaced frequently. The encapsulation and release of the repellents from several matrices has risen as an alternative process for the development of invention of repellent based systems. The present work reviews various studies about the development and use of repellent controlled-release formulations such as polymer microcapsules, polymer microporous formulations, polymer micelles, nanoemulsions, solid-lipid nanoparticles, liposomes and cyclodextrins as new tools for mosquitoborne malaria control in the outdoor environment. Furthermore, investigation on the mathematical modelling used for the release rate of repellents is discussed in depth by exploring the Higuchi, Korsmeyer-Peppas, Weibull models, as well as the recently developed Mapossa model. Therefore, the studies searched suggest that the final repellents based-product should not only be effective against mosquito vectors of malaria parasites, but also reduce the biting frequency of other mosquitoes transmitting diseases, such as dengue fever, chikungunya, yellow fever and Zika virus. In this way, they will contribute to the improvement in overall public health and social well-being.The University of Pretoria (UP) Postdoctoral Fellowship programmehttps://malariajournal.biomedcentral.comam2022Chemical EngineeringSchool of Health Systems and Public Health (SHSPH)UP Centre for Sustainable Malaria Control (UP CSMC

Contribuição à Geologia e à Geocronologia do Terreno Rio Capibaribe (TRC, Província Borborema)

O Terreno Rio Capibaribe (TRC) foi definido ao sul - sudeste da Zona Transversal da Província Borborema (parte SE da Paraíba e parte NE de Pernambuco). Seus limites convencionais são grandes zonas de cisalhamento, a Congo - Cruzeiro do Nordeste (ao norte e noroeste) e o lineamento Pernambuco, ao sul. Esse terreno apresenta embasamento gnáissico-migmatítico do Paleoproterozoico e faixas móveis neoproterozoicas, do Eotoniano e do Criogeniano-Ediacarano. O embasamento desse TRC está recortado por várias intrusivas paleo, mesoproterozoicas (devidamente reestruturadas pelos ciclos mais jovens) e neoproterozoicas, de diferentes natureza e proveniências (ligadas ao desenvolvimento de arcos magmáticos, zonas de cisalhamento etc.), sendo destacáveis aqueles grandes corpos calcioalcalinos, de diferentes grupos composicionais. O TRC era conhecido em escalas pequenas, principalmente nos mapas geológicos dos estados acima mencionados, executados no início deste século. Apesar de várias teses e outros trabalhos científicos de vulto no TRC, ele foi considerado aquele terreno menos privilegiado em termos de dados sobre sua evolução geocronológica, motivos indutores da presente pesquisa. Foram realizadas várias seções geológicas e ampla consulta bibliográfica concomitante à realização de determinações geocronológicas pelos métodos Sm-Nd (ca. 60), Rb-Sr (ca. 50) e U-Pb (ca.8). Ao mesmo tempo, os autores procuraram acompanhar os mapas 1/100.000 presentemente em execução, ao largo deste terreno (pela Companhia de Pesquisa de Recursos Minerais - CPRM, Serviço Geológico do Brasil). Uma síntese interpretativa da evolução geológica e geocronológica será apresentada com a somatória de todos esses dados, válidos na presente instância do conhecimento, na tentativa de aclarar um pouco a complexa e rica evolução crustal desse terreno.The Rio Capibaribe Terrane (TRC) was first referred for the south - southeast part of the Transversal Zone, central domain of the Borborema Province (minor part SE of Paraíba and NE of Pernambuco states). The attributed conventional boundaries for this terrane are major shear zones, the Congo - Cruzeiro do Nordeste (to the north and northwest) and Pernambuco lineament to the south. This terrane exhibits gneissic-migmatitic basement complexes of Paleoproterozoic age and Neoproterozoic fold belts of the Tonian ("Cariris Velhos" cycle) and the Cryogenian - Ediacaran ("Brasiliano" cycle). It is crosscuted by many intrusive rock assemblages of the Paleoproterozoic, Mesoproterozoic and Neoproterozoic ages, of different sources and tectonic natures (anorogenic plutonism, plutons related to shear zones, and magmatic arcs etc.), these last ones presenting calc-alkaline rock types of different compositional groups are emphasized. The TRC was known in small scales, mainly in geological maps of the mentioned states, in the beginnings of this century. There are these and other scientific papers of great importance about the geology of parts of this terrane; nevertheless, it was considered the less privileged of all terranes of the Borborema Province, in terms of geochronological evolution data, and this was the motivation for the development of this paper. Many geological sections were carried out pari passu to extensive bibliographical research, as well as with the implementation of new geochronological determinations, by different methods, as Mend (ca. 60), Rb-Sr (ca. 50) and U-Pb (ca. 8, TIMS + LA-ICPMS). During that time, the authors looked to be accounted with the development of new geological mapping (scales 1/ 100,000) projects, several sheets, along this terrane, that were performed by the CPRM (Brazilian Geological Survey). An interpretative synthesis of the geological and geochronological evolution is being proposed, with the sum and help of all these data, being valid only for the present instance, in order to explain the complex and rich crustal evolution of this terrane

Cellulose acetate/organoclay nanocomposites as controlled release matrices for pest control applications

This study aimed to develop cellulose-based polymer matrices as controlled release devices for plant-based insect repellents and attractants, with the aim of finding sustainable and environmentally friendly pest control methods for agricultural applications. Citronellol, terpineol and methyl salicylate were the selected active compounds for this study. Their compatibility with cellulose diacetate was predicted using Hansen Solubility Parameters, which predicted terpineol as the most compatible with cellulose diacetate, followed by methyl salicylate and citronellol. This was consistent with the plasticization efficiency trend from DMA results of solvent cast cellulose diacetate films containing the active compounds. The chemical identity of the films and cellulose diacetate-active compound intermolecular interactions were verified by FTIR. TGA demonstrated the thermal stability of cellulose diacetate/active compound/clay formulations at temperatures not exceeding 170 °C. Cellulose diacetate/organoclay nanocomposite matrices containing the active compounds at 35 wt-% were prepared by twin screw extrusion compounding, with the active compounds also functioning as plasticizers. The amount of active compound in the strands was determined by solvent extraction and TGA. Both methods showed that small amounts of active compound were lost during the compounding process. SEM demonstrated the effect of organoclay on the internal morphology of the matrix, whereas TEM showed clay dispersion and intercalation within the matrix. The matrix served as a reservoir for the active compounds while simultaneously controlling their release into the environment. Release profiles, obtained through oven ageing at 40 °C for 70 days, were fitted to existing Log-logistic and Weibull models, and novel Diffusion and Modified Weibull release models. Citronellol was released the fastest, followed by methyl salicylate and terpineol. The findings suggest that cellulose diacetate/organoclay strands are promising controlled-release matrices for pest control purposes.he Paper Manufacturers Association of South Africa (PAMSA) and the Department of Science and Innovation (DSI) and the National Research Foundation of South Africa (NRF).https://link.springer.com/journal/10570hj2023Chemical EngineeringUP Centre for Sustainable Malaria Control (UP CSMC

Blooming of chlorfenapyr from polyethylene films

FTIR, in ATR and in transmission modes, enabled the tracking of the migration of the insecticide Chlorfenapyr to the surface of a polymer film. It also allowed estimation of the apparent solubility in the polymer. However, SEM investigations revealed that a portion of the insecticide is trapped, in a crystalline state, inside the polymer matrix.https://aip.scitation.org/journal/apcpm2021Chemical EngineeringUP Centre for Sustainable Malaria Control (UP CSMC

Slow-DEET-release mosquito-repellent system based on poly(butylene succinate)

Bio-sourced and biodegradable poly(butylene succinate) (PBS) strands containing up to 40 m% mosquito-repellent N,N-diethyl-3-methylbenzamide (DEET) were obtained by extrusion, for an initial evaluation of the DEET evaporation characteristics and the possible application of such strands as biodegradable slow-release repellent-delivery devices. For DEET concentrations up to 20 m%, DEET is entrapped in the semicrystalline spherulitic superstructure of PBS. In contrast, at higher DEET concentrations, the liquid repellent, at least partially, is not fully incorporated in the PBS spherulites rather than segregates to form an own macrophase. Quantification of the release of DEET to the environment by thermogravimetric analysis at different temperatures between 60 and 100 °C allowed estimation of the evaporation rate at lower service temperatures, suggesting an extremely low release rate with a time constant of the order of magnitude of 1−2 years at 25 °C, independent of the initial concentration.Deutsche Forschungsgemeinschaft (DFG) and Martin Luther University Halle-Wittenberg.http://pubs.acs.org/journal/acsodfChemical Engineerin

Characterizing the thermal phase behaviour of fipronil polymorphs

This manuscript reports the investigation of the polymorphic behaviour of fipronil using a systematic comparison of the thermochemical and structural properties of different crystal forms obtained in this study as well as those previously reported in literature. The analytical techniques employed include DSC, TGA, PXRD, SCXRD and hot stage microscopy. DSC proved particularly useful because it made it possible to differentiate between the two different crystal forms found in the as-received neat fipronil. The DSC scans revealed the presence of two polymorphs which had melting endotherms with peak maxima at ca. 196 °C and 205 °C, respectively. These polymorphs were successfully separated via sublimation and resulted in a metastable, lower melting polymorph in the sublimate and a thermodynamically stable, higher melting form in the sublimation residue. Clear evidence for the instability of the lower melting polymorph was found when the endotherms were examined under a range of heating rates. The proportion of the metastable form appeared to increase as the rate was increased, indicating that the metastable form underwent a solid–solid phase transition to the stable form at low heating rates. Recrystallization of fipronil from different solvents yielded five different forms. TGA curves revealed that all forms, except the acetone-derived one, were solvate pseudo-polymorphs that showed solvent loss between 60 and 100 °C. The acetone-derived sample was a hemihydrate that only started to show mass loss at 120 °C. SCXRD studies revealed that three of the five forms have similar structural characteristics, while the other two forms differ notably from each other and the rest of the structures. Despite these structural differences, all five forms exhibit near-identical intra- and intermolecular hydrogen bond networks.Open access funding provided by University of Pretoria.This work is supported in part by Department of Higher Education and Training (DHET, South Africa) under the USDP funding instrument and by the Deutsche Forschungsgemeinschaft (DFG).https://www.springer.com/journal/10973Chemical EngineeringChemistrySDG-09: Industry, innovation and infrastructur

Microporous polyolefin strands as controlled-release devices for mosquito repellents

The main vectors of malaria in Africa, i.e. An. arabiensis, An. gambiae s.s. and An. funestus, are attracted by human foot odour and they tend to bite victims in the ankle area. Hence, affordable mosquito-repellent polymer-foot bracelets with long lasting protection could reduce infective lower limb bites and therefore help to reduce the overall malaria transmission rate. This study investigated the possibility of increasing the duration of repellence activity by incorporating repellents into inexpensive thermoplastic polymers, namely poly(ethylene-co-vinyl acetate) (EVA) and linear low-density polyethylene (LLDPE). Volatile repellents need to be released into the surrounding air to be effective, i.e. they are continuously lost to the atmosphere. This means that the bracelet should also act as a reservoir for relatively large quantities of the active compound. Towards this goal, polymer strands containing mosquito repellent were prepared by twin-screw extrusion compounding. A co-continuous phase structure was achieved by rapid quenching in an ice bath of the homogeneous polymer-repellent melt mixture exiting the extruder. Phase separation occurred through spinodal decomposition that trapped the liquid repellent in the microporous polymer matrix. A skin-like membrane that covered the extruded polymer strands controlled the release rate. Strands that contained up to 30 wt-% of either DEET or Icaridin provided effective protection against mosquito bites even after 12 weeks of ageing at 50 °C.The Deutsche Forschungsgemeinschaft (DFG), Germany, under Grant AN 212/22-1.http://http://www.elsevier.com/locate/cej2020-03-15hj2019Chemical EngineeringMedical VirologyStatistic

Alimentação popular em São Paulo (1920 a 1950): políticas públicas, discursos técnicos e práticas profissionais

This article discusses how the concept of lower-class eating habits came about and developed in the intellectual circles of São Paulo during the first half of the 20th century. It starts by reconstructing the elements of the debate around the income and ignorance of the underprivileged as the main reasons behind their bad eating habits. Then, it looks at the focal points for interventions and public policies proposed by the government to deal with the problem thus identified, namely: training methods to produce sanitation counselors capable of offering dietary guidance as well; popular educational campaigns and new learning sites in addition to schools (e.g. healthcare centers and households); lunch and other means of offering food at schools; and diagnostic studies about food intake and eating habits among laborers. Because they were translated into technical and scientific language, the proposals and policies implemented in São Paulo left traces in a variety of supporting documents and media (photographs, primers, posters, inquiry notebooks, and academic literature).O artigo discute a construção da idéia de alimentação popular nos meios intelectuais em São Paulo, na primeira metade do século XX. Para isso, reconstitui, como motivos da má alimentação, elementos do debate em torno da renda e da ignorância dos mais pobres. Identificado o problema, as propostas de intervenção e as políticas públicas concentraram-se em alguns setores, abordados neste trabalho: métodos para a formação de educadores sanitários aptos a atuar também na educação alimentar; campanhas de instrução popular e criação de novos lugares de aprendizado (além das escolas, os centros de saúde e os lares); merenda escolar e outras alternativas de alimentação nas escolas; e diagnósticos referentes ao conteúdo e à forma da alimentação dos operários. Traduzidas em discurso técnico-científicos, as propostas e políticas implementadas na cidade deixaram indícios em documentação de suporte e tipologia variados (fotografias, cartilhas, cartazes, cadernetas de inquéritos e textos acadêmicos).Universidade Federal de São Paulo (UNIFESP)UNIFESPSciEL

Mosquito repellent microporous polyolefin strands

Pyrogenic silica and organoclay nanocomposite strands containing liquid mosquito repellents were prepared by twinscrew extrusion compounding. The mosquito repellents DEET and Icaridin were immobilized in the pores of a microporous polyolefin matrix. The nature and levels of the repellent and nanofiller employed affected the material phase morphology. The repellent release was followed as a function of ageing time in convection ovens set at 50 qC. The release rates were a described by a mathematical model that considered the microporous internal structure. In most cases, the integral skin covering the strands determined the repellent release rate. The implication of these findings is that Icaridin is an attractive candidate for long-lasting wearable mosquito repellent devices.The Deutsche Forschungsgemeinschaft (DFG)https://aip.scitation.org/journal/apcpm2021Chemical EngineeringUP Centre for Sustainable Malaria Control (UP CSMC

Development, characterization and modeling of mosquito repellent release from microporous devices

Nanocomposite strands with mosquito repellent DEET or Icaridin incorporated in a poly(ethylene-co-vinyl acetate) (EVA) matrix, with either pyrogenic silica or an organoclay as a nanofiller, were prepared by a twin-screw extrusion compounding technique. The nature and levels of the repellent and nanofiller that was used affected the material phase morphology. The repellent release was followed as a function of aging time in convection ovens set at 30 and 50 C. The experimental release data of the mosquito repellent from the microporous polymer swellable matrix strands was mathematically modeled and fitted using a range of semi-empirical models. In the majority of case, the Korsmeyer-Peppas power law model provided the best data fit. As expected, the wide range of internal morphologies also resulted in quite different release profiles. These models were found to be valuable as they provided insights into the mechanism of repellent release from EVA swellable matrices. It was possible to differentiate between diffusion and relaxation mechanisms. Surprisingly, strands containing nominally more than 30 wt% Icaridin showed accelerating mass loss during the initial phase, consistent with Super Case II transport. Diffusional exponents as high as 1.81 were found. Furthermore, the internal microporous region of the extruded EVA strands was covered by a surface membrane that acted a diffusion barrier that, in effect, controlled the release rate of the mosquito repellents. Some of the investigated samples exhibited release profiles that suggest that longer lasting effective release of repellents is possible than currently achieved by available commercially products.Deutsche Forschungsgemeinschaft (DFG)https://onlinelibrary.wiley.com/journal/26903857hj2021Chemical EngineeringUP Centre for Sustainable Malaria Control (UP CSMC