A new long-term composite drug delivery system based on thermo-responsive hydrogel and nanoclay

Several problems and limitations faced in the treatment of many diseases can be overcome by using controlled drug delivery systems (DDS), where the active compound is transported to the target site, minimizing undesirable side effects. In situ-forming hydrogels that can be injected as viscous liquids and jellify under physiological conditions and biocompatible clay nanoparticles have been used in DDS development. In this work, polymer–clay composites based on Pluronics (F127 and F68) and nanoclays were developed, aiming at a biocompatible and injectable system for long-term controlled delivery of methylene blue (MB) as a model drug. MB release from the systems produced was carried out at 37◦C in a pH 7.4 medium. The Pluronic formulation selected (F127/F68 18/2 wt.%) displayed a sol/gel transition at approx. 30◦C, needing a 2.5 N force to be injected at 25◦C. The addition of 2 wt.% of Na116 clay decreased the sol/gel transition to 28◦C and significantly enhanced its viscoelastic modulus. The most suitable DDS for long-term application was the Na116-MB hybrid from which, after 15 days, only 3% of the encapsulated MB was released. The system developed in this work proved to be injectable, with a long-term drug delivery profile up to 45 days.publishersversionpublishe

A Review

This work is co-financed by FEDER, European Funds, through the COMPETE 2020 POCI and PORL, National Funds through FCT—Portuguese Foundation for Science and Technology, and POR Lisboa2020, under the projects PIDDAC (POCI-01-0145-FEDER-007688, Reference UIDB/50025/2020-2023) and PTDC/CTMCTM/30623/2017 (DREaMM). P.S. also acknowledges the individual contract CEECIND.03189.2020. C.T. acknowledges i3N for the Ph.D. grant with reference UI/BD/151541/2021. Publisher Copyright: © 2022 by the authors.In recent decades, new and improved materials have been developed with a significant interest in three-dimensional (3D) scaffolds that can cope with the diverse needs of the expanding biomedical field and promote the required biological response in multiple applications. Due to their biocompatibility, ability to encapsulate and deliver drugs, and capacity to mimic the extracellular matrix (ECM), typical hydrogels have been extensively investigated in the biomedical and biotechnological fields. The major limitations of hydrogels include poor mechanical integrity and limited cell interaction, restricting their broad applicability. To overcome these limitations, an emerging approach, aimed at the generation of hybrid materials with synergistic effects, is focused on incorporating nanoparticles (NPs) within polymeric gels to achieve nanocomposites with tailored functionality and improved properties. This review focuses on the unique contributions of clay nanoparticles, regarding the recent developments of clay-based nanocomposite hydrogels, with an emphasis on biomedical applications.publishersversionpublishe

Preliminary insights into electro-sensitive ecolubricants: A comparative analysis based on nanocelluloses and nanosilicates in castor oil

The newest generation of lubricants needs to adapt to stricter environmental policies. Simple and sustainable formulations with tunable rheological properties under the action of electric potentials may be the key. The present research explored the feasibility of producing electro-sensitive ecolubricants based on nanocellulose (crystalline and fibrillar) or nanoclay (Cloisite 15A montmorillonite and halloysite nanotubes) dispersions in castor oil, at concentrations that ranged from 2 to 6 wt.%. Broadband dielectric spectroscopy (BDS) measurements allowed for a first estimate on the electro-responsive potential of the nanofluids. The nanocelluloses and the montmorillonite suspensions presented a relaxation event in the dielectric loss, e", centered at ca. 2-4 kHz, which is related to interfacial polarization. Moreover, their actual electro-rheological (ER) effect under high electric potentials up to 4 kV/mm was assessed by determining the magnitude of the yield stress from steady flow curves at 25 °C. It was found that the nanocelluloses and the montmorillonite showed an enhancement of three orders of magnitude in their yield stress values at 4 kV/m. This enhancement was much greater than in the halloysite nanoclay, which did not exhibit any polarization). This is the starting point for the development of environmentally friendly ER lubricating fluids, based on nanocellulose and montmorillonites (layered nanosilicates), which might assist in reducing the friction and wear through the application of controlled electric fields.publishersversionpublishe

Molecular Genetic Variability, Population Structure and Mating System in Tropical Forages

Microsatellite (SSR) markers were developed for the following tropical forage species, using accessions available from the plant genetic resources (PGR) collections held by EMBRAPA (Brazilian Agricultural Research Corporation): Brachiaria brizantha, B. humidicola, Panicum maximum, Paspalum spp., Stylosanthes capitata, S. guianensis, S. macrocephala, Calopogonium mucunoides and Centrosema spp. The markers were used to analyse population structure and genetic diversity, evolution and origin of the genetic variability in the centre of origin, mating systems and genetic resources in EMBRAPA’s germplasm bank. The results shed light on the amount of genetic variation within and between populations, revealed the need in some cases for further plant collection to adequately represent the species in PGR collections, allowed us to assemble core collections (subsets of the total collections) that should contain most of the available diversity and (in the case of the legumes) showed the need to avoid unwanted outcrossing when regenerating conserved material. The data will allow plant breeders to better select accessions for hybrid production, discriminate between genotypes and use marker-assisted selection in breeding programs. Our results will also underpin the construction of genetic maps, mapping of genes of agronomic interest and numerous other studies on genetic variability, population structure, gene flow and reproductive systems for the tropical forage species studied in this work

Experimental characterization of injection grouts incorporating hydrophobic silica fume

(FCT/MCTES) through the scholarship SFRH/BPD/108427/2015. The authors would like to acknowledge the support from the strategic project UID/CTM/50025/2013.This paper puts forward a new hydrophobic silica fume and assesses its contribution to the performance improvement of grouts for stone masonry consolidation. The experiments were conducted using different dosages of hydrophobic silica fume with natural hydraulic lime grouts in the presence of a polycarboxylate-based high-range water reducer. Results revealed that the effects of hydrophobic silica fume on properties of natural hydraulic lime grouts optimize the use of ordinary silica fume. Remarkable rheological performance was obtained in the presence of hydrophobic silica fume: the plastic viscosity and yield stress were reduced compared with the ordinary silica fume. For mechanical strength aspects, it was found that hydrophobic silica fume slightly affected the flexural and compressive strength; however, the values obtained are suitable for the old stone masonry consolidation purposes. It was also observed that water capillarity was substantially reduced as a result of the water-repellent behavior of hardened grouts. This study suggests that the promising effectiveness of this new silica fume for injection grouts opens the way for it to be used in many other applications.authorsversionpublishe

Antioxidants in Sunscreens: Which and What For?

Ultraviolet (UV) radiation promotes the generation of reactive oxygen species (ROS) and nitrogen species (RNS), resulting in skin damage. Cosmetic industries have adopted a strategy to incorporate antioxidants in sunscreen formulations to prevent or minimize UV-induced oxidative damage, boost photoprotection effectiveness, and mitigate skin photoaging. Many antioxidants are naturally derived, mainly from terrestrial plants; however, marine organisms have been increasingly explored as a source of new potent antioxidant molecules. This work aims to characterize the frequency of the use of antioxidants in commercial sunscreens. Photoprotective formulations currently marketed in parapharmacies and pharmacies were analyzed with respect to the composition described on the label. As a result, pure compounds with antioxidant activity were found. The majority of sunscreen formulations contained antioxidants, with vitamin E and its derivatives the most frequent. A more thorough analysis of these antioxidants is also provided, unveiling the top antioxidant ingredients found in sunscreens. A critical appraisal of the scientific evidence regarding their effectiveness is also performed. In conclusion, this work provides an up-to-date overview of the use of antioxidants in commercial sunscreens for a better understanding of the advantages associated with their use in photoprotective formulations

UV Filters: Challenges and Prospects

The use of sunscreens is an established and recommended practice to protect skin from solar-induced damage. Around 30 UV filters can be used in sunscreen products in the European Union, which ought to follow the requirements of the regulation 1223/2009 to ensure their efficacy and safety for humans. Nevertheless, low photostability and putative toxicity for humans and environment have been reported for some UV filters. Particularly, the negative impact in marine organisms has recently raised concern on the scientific community. Therefore, it is important to develop new UV filters with improved safety profile and photostability. Over the last two decades, nearly 200 new compounds have revealed promising photoprotection properties. The explored compounds were obtained through different approaches, including exploration of natural sources, synthetic pathways, and nanotechnology. Almost 50 natural products and around 140 synthetic derivatives, such as benzimidazoles, benzotriazoles, hydroxycinnamic acids, xanthones, triazines, among others, have been studied aiming the discovery of novel, effective, and safer future photoprotective agents. Herein, we provide the reader with an overview about UV filters' challenges and prospects, offering a forward-looking to the next-generation of UV filters

Recent Trends on UV filters

UV filters are the shield ingredients of sunscreens against the negative effects of solar radiation. Since the discovery of the first UV filter, nearly 30 filters have become commercially available. Over the years, innovation and regulatory updates have driven their use by the cosmetic industry. This work aimed to characterize commercial sunscreens and unveil the main trends by analyzing the labels of 444 sunscreen formulations that are currently being marketed. Avobenzone, octocrylene, and bis-ethylhexyloxyphenol methoxyphenyl triazine were the three UV filters with the highest usage frequencies (>40%). Emulsified preparations and sprays were the preferred forms, while the most frequent SPF was 50+. Differences were noted between adult and children’s sunscreens, namely the higher usage of inorganic filters for the latter. Over the past few years, the five most used UV filters remained the same, but octocrylene, ethylhexyl salicylate, and nano methylene bis-benzotriazolyl tetramethylbutylphenol had decreased usage. An increasing tendency towards the use of the inorganic UV filter titanium oxide was also observed. Overall, this study characterized the true market impact of approved UV filters and how the market has evolved over recent years. This insight can help pave the way for the design of new UV filters and is helpful for the assessment of environmental risks

Recent Trends on UV filters

UV filters are the shield ingredients of sunscreens against the negative effects of solar radiation. Since the discovery of the first UV filter, nearly 30 filters have become commercially available. Over the years, innovation and regulatory updates have driven their use by the cosmetic industry. This work aimed to characterize commercial sunscreens and unveil the main trends by analyzing the labels of 444 sunscreen formulations that are currently being marketed. Avobenzone, octocrylene, and bis-ethylhexyloxyphenol methoxyphenyl triazine were the three UV filters with the highest usage frequencies (>40%). Emulsified preparations and sprays were the preferred forms, while the most frequent SPF was 50+. Differences were noted between adult and children’s sunscreens, namely the higher usage of inorganic filters for the latter. Over the past few years, the five most used UV filters remained the same, but octocrylene, ethylhexyl salicylate, and nano methylene bis-benzotriazolyl tetramethylbutylphenol had decreased usage. An increasing tendency towards the use of the inorganic UV filter titanium oxide was also observed. Overall, this study characterized the true market impact of approved UV filters and how the market has evolved over recent years. This insight can help pave the way for the design of new UV filters and is helpful for the assessment of environmental risks

Up-to-Date Overview of the Use of Natural Ingredients in Sunscreens

The photoprotective skincare segment is in high demand to meet consumer concerns on UV-induced skin damage, with a recent trend towards sunscreen alternatives with a natural origin. In this study, the use of natural ingredients, either from terrestrial or marine origin, in a panel of 444 sunscreen commercial formulations (2021) was analyzed. Ingredients from terrestrial organisms represent the large majority found in the analyzed sunscreen formulations (48%), whereas marine ingredients are present only in 13% of the analyzed products. A deeper analysis regarding the most prevalent families of ingredients from terrestrial and marine organisms used as top ingredients is also presented, as well as their mechanisms of action. This study provides an up-to-date overview of the sunscreen market regarding the use of natural ingredients, which is of relevance for scientists involved in the development of new sunscreens to identify opportunities for innovation