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- Alginate films encapsulating polyphenols for nutraceutical and biomedical applicationsPublication . Lagoa, Ricardo; Vanat, Pavlo; Ferreira, Stefanie; Silva, João; Marques-da-Silva, Dorinda; Ribeiro, Vânia; Vaz, Daniela C.; Barreiros, Fátima; Rodrigues, Joaquim Rui
- Towards the Development of Delivery Systems of Bioactive Compounds With Eyes Set on PharmacokineticsPublication . Silva, João S.; Marques-da-Silva, Dorinda; Lagoa, RicardoDelivery systems carrying natural bioactive compounds for enhanced targeting and controlled release are capturing increasing attention. High loadings and sustained release are common design goals. However, in the case of compounds naturally present in human nutrition and physiology, further efforts are justified to optimize their bioactivity and promote clinical success. In this work, it is proposed a specific attention to the regulation of drug temporal presentation as important factor to obtain novel multifunctional delivery systems meeting higher therapeutic efficiencies. Case studies on the relation between drug release dynamics and biological responses are presented for some major delivery strategies and different bioactive molecules. Pharmacokinetic essential concepts and issues concerning the multi-target mode of action typical of the pharmacological properties of natural compounds are discussed in the perspective of improving the development of efficient drug formulations. Several classes of controlled release systems are considered through the chapter, and laboratory setups for testing films and particulate delivery systems are detailed, as well as the application of models for kinetic analysis. Descriptions are illustrated with experimental results obtained with caffeine and epicatechin in our laboratory. Future investigations will benefit from preclinical and clinical evaluation of the new formulations developed by emerging approaches and tools that are being suggested by diverse authors.
- Bioactivity gradients of cytoprotective and anticancer catechins in skin: Simulation studies for the design of controlled release systemsPublication . Silva, João; Videira, Paula; Lagoa, RicardoDermal delivery of catechins may be an effective approach for protection of skin against inflammation, aging and cancer caused by exposure to radiation and environmental toxicants. Catechins are flavonoid-type polyphenols showing capacity to attenuate UV-induced skin injury, carcinogenesis and melanoma metastasis, but the prevalence of beneficial effects depends on compound concentration. In this work, catechin penetration through the skin was simulated to predict the concentration in different layers: stratum corneum, viable epidermis and dermis. By combining these results with expected dose-effect relationships of the compounds, bioactivity profiles were calculated for relevant skin regions. Since the concentration dependences of catechin capacities to protect dermal fibroblasts and to inhibit melanoma cells (data aggregated from published literature) follow different types of dose-effect curves, bioactivity profiles in the skin can be different, even for the same delivery conditions. This method allows to estimate the delivery conditions (time and concentrations) required to achieve the desired biological/pharmacological activities at critical skin strata, namely, viable epidermis and dermis where metastatic melanoma cells and susceptible fibroblasts localize. The work suggests a framework to support the rational design of controlled release systems of topically applied bioactive compounds in therapeutic and investigative delivery.
- Reassessment of the experimental skin permeability coefficients of polycyclic aromatic hydrocarbons and organophosphorus pesticidesPublication . Silva, João; Marques da Silva, Dorinda; Lagoa, Ricardo
- Metal alginates for polyphenol delivery systems: Studies on crosslinking ions and easy-to-use patches for release of protective flavonoids in skinPublication . Silva, João; Vanat, Pavlo; Marques da Silva, Dorinda; Rodrigues, Joaquim Rui; Lagoa, RicardoIncorporation of bioactive natural compounds like polyphenols is an attractive approach for enhanced functionalities of biomaterials. In particular flavonoids have important pharmacological activities, and controlled release systems may be instrumental to realize the full potential of these phytochemicals. Alginate presents interesting attributes for dermal and other biomaterial applications, and studies were carried here to support the development of polyphenol-loaded alginate systems. Studies of capillary viscosity indicated that ionic medium is an effective strategy to modulate the polyelectrolyte effect and viscosity properties of alginates. On gelation, considerable differences were observed between alginate gels produced with Ca2+, Ba2+, Cu2+, Fe2+, Fe3+ and Zn2+ as crosslinkers, especially concerning shrinkage and morphological regularity. Stability assays with different polyphenols in the presence of alginate-gelling cations pointed to the choice of calcium, barium and zinc as safer crosslinkers. Alginate-based films loaded with epicatechin were prepared and the kinetics of release of the flavonoid investigated. The results with calcium, barium and zinc alginate matrices indicated that the release dynamics is dependent on film thicknesses, but also on the crosslinking metal used. On these grounds, an alginate-based system of convenient use was devised, so that flavonoids can be easily loaded at simple point-of-care conditions before dermal application. This epicatechin-loaded patch was tested on an ex-vivo skin model and demonstrated capacity to deliver therapeutically relevant concentrations on skin surface. Moreover, the flavonoid released was not modified and retained full antioxidant bioactivity. The alginate-based system proposed offers a multifunctional approach for flavonoid controllable delivery and protection of skin injured or under risk.
- Bioactivity gradients of cytoprotective and anticancer catechins in skin: Simulation studies for the design of controlled release systemsPublication . Silva, João; Videira, Paula; Lagoa, RicardoDermal delivery of catechins may be an effective approach for protection of skin against inflammation, aging and cancer caused by exposure to radiation and environmental toxicants. Catechins are flavonoid-type polyphenols showing capacity to attenuate UV-induced skin injury, carcinogenesis and melanoma metastasis, but the prevalence of beneficial effects depends on compound concentration. In this work, catechin penetration through the skin was simulated to predict the concentration in different layers: stratum corneum, viable epidermis and dermis. By combining these results with expected dose-effect relationships of the compounds, bioactivity profiles were calculated for relevant skin regions. Since the concentration dependences of catechin capacities to protect dermal fibroblasts and to inhibit melanoma cells (data aggregated from published literature) follow different types of dose-effect curves, bioactivity profiles in the skin can be different, even for the same delivery conditions. This method allows to estimate the delivery conditions (time and concentrations) required to achieve the desired biological/pharmacological activities at critical skin strata, namely, viable epidermis and dermis where metastatic melanoma cells and susceptible fibroblasts localize. The work suggests a framework to support the rational design of controlled release systems of topically applied bioactive compounds in therapeutic and investigative delivery.