Synthesis of poly (N-vinyl pyrrolidone) (PVP) nanogels by gamma irradiation using different saturation atmospheres

Nanogels are internally crosslinked particles of nanometric size used in various fields e.g. as such as carriers in drug delivery systems. They can be produced using ionizing radiation in dilute aqueous solutions. This method is carried out in a pure polymer-solvent system, avoiding the addition of any additives such as monomers, surfactants, catalysts and crosslinking agents and no further purification step is necessary. Poly(N-vinyl pyrrolidone) (PVP K-90) nanogels were prepared by gamma irradiation in an aqueous solution. The samples were prepared in triplicate in multipurpose cobalt-60 gamma irradiator using 1, 10, 25 and 100 mM PVP solutions. Samples were irradiated in argon and nitrous oxide conditions with doses from 1 kGy up to 25 kGy with 10 kGy/h dose rate. The mean particle size (Rh) was determined by Dynamic Light Scattering (DLS) and radius of gyration (Rg) and weight-average molecular weight (Mw) by Static Light Scattering (SLS). These samples were morphologically characterized using Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Samples prepared with 100 mM PVP K-90 solution formed macroscopic gels, in the samples obtained with 25 mM PVP K-90 solution there was a prevalence of intermolecular crosslinking. On the other hand, in the samples generated with 10 mM PVP K-90 solution, there was a predominance of intramolecular crosslinking demonstrated in the tendency to: decrease in the radius of gyration (Rg), in the constancy of the weight-average molecular weight (Mw), in the increase in polymer coil density (ρcoil), in the Rg/Rh ratio (shape factor) around 1.0 indicating homogenous, internally cross-linked spheres, in the high relief spherical structures observed in the AFM images and in the spherical particles with high contrast observed in the TEM images. The saturation of the samples with nitrous oxide doubled formation of hydroxyl radicals, favoring the generation of polymeric radicals. Higher average number of radicals in each macromolecule contributed to the higher number of intramolecular crosslinks.

Ultraviolet radiation protection: current available resources in photoprotection.

Ultraviolet radiation can damage the DNA, cause immunosuppression, chemical and histological alterations in the epidermis, early photoaging, cataracts and carcinogenesis, among others. Photoprotection prevents these and other harmful effects of ultraviolet radiation. Sunscreens, protective clothing, proper accessories and safe sun exposure are essential photoprotection tools. The main forms of photoprotection are presented and discussed in this article, including sunscreens containing organic and inorganic filters, the assessment of their efficacy and current developments on the topic.

Proteção à radiação ultravioleta: recursos disponíveis na atualidade em fotoproteção / Ultraviolet radiation protection: current available resources in photoprotection

A radiação ultravioleta pode provocar danos ao DNA, imunossupressão, alterações químicas e histológicas na epiderme, envelhecimento precoce, cataratas e carcinogênese, dentre outras deteriorações. A fotoproteção previne estes e outros efeitos danosos da radiação ultravioleta. Protetores solares, vestimentas, acessórios adequados e exposição segura ao sol são ferramentas essenciais da fotoproteção. Neste artigo, são apresentadas e discutidas as principais formas de fotoproteção, incluindo os protetores solares com filtros inorgânicos e orgânicos, a avaliação da eficácia dos mesmos e atualizações envolvendo o tema.

Ultraviolet radiation can damage the DNA, cause immunosuppression, chemical and histological alterations in the epidermis, early photoaging, cataracts and carcinogenesis, among others. Photoprotection prevents these and other harmful effects of ultraviolet radiation. Sunscreens, protective clothing, proper accessories and safe sun exposure are essential photoprotection tools. The main forms of photoprotection are presented and discussed in this article, including sunscreens containing organic and inorganic filters, the assessment of their efficacy and current developments on the topic.

Hidrolipodistrofia ginoide: aspectos gerais e metodologias de avaliação da eficácia: [revisão] / Gynoid lipodystrophy: general aspects and methodologies for efficacy evaluation: [review]

A hidrolipodistrofia ginoide (HLDG), popularmente conhecida como celulite, está presente em grande parte da população feminina. Trata-se de umaalteração do relevo cutâneo, envolvendo modificações morfológicas, histoquímicas, bioquímicas e ultraestruturais nos adipócitos, além de alterações na derme e na microcirculação. Existem inúmeras formas de se tratar essa condição, sendo a mais utilizada e de fácil acesso o uso de produtos tópicos contendo princípios ativos com ação vasoprotetora, anti-inflamatória, estimuladores da microcirculação periférica e agentes lipolíticos. Para verificar a eficácia destas formulações, existem metodologias de avaliação envolvendo avaliações instrumentais e clínicas da melhoria do aspecto da celulite. Este artigo teve por objetivo revisar as formas existentes de se avaliar a ação de produtos que atuam na HLDG, considerando os diversos mecanismos de ação, além de revisar aspectos gerais referentes a esta condição.

Gynoid lipodystrophy (HLDG), popularly known as cellulite, is present in a great part of the female population. It is an alteration of the cutaneousrelief involving morphological, histochemical, biochemical and ultrastructural modifications in the adipocytes and also alterations in the dermis andmicrocirculation. There are countless ways of treating this condition, being topic products containing active principles with vessel protective, antiinflammatory actions, peripheral microcirculation stimulators and lipolytic agents the most used and of easiest access. In order to verify the efficacyof these formulations, there are evaluation methodologies involving instrumental and clinical evaluations of the improvement of the aspect of cellulite. Therefore, this article aimed at reviewing the existent ways of evaluating the efficacy of products against gynoid lipodystrophy, taking the different mechanisms of action into account and also at reviewing general aspects concerning this condition.