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Wound healing is a complex process involving an integrated response by many different cell types and growth factors in order to achieve rapid restoration of skin architecture and function. The present study evaluated the applicability of a chitosan hydrogel (CH) as a wound dressing. Scanning electron microscopy analysis was used to characterize CH morphology. Fibroblast cells isolated from rat skin were used to assess the cytotoxicity of the hydrogel. CH was able to promote cell adhesion and proliferation. Cell viability studies showed that the hydrogel and its degradation by-products are noncytotoxic. The evaluation of the applicability of CH in the treatment of dermal burns in Wistar rats was performed by induction of full-thickness transcutaneous dermal wounds. Wound healing was monitored through macroscopic and histological analysis. From macroscopic analysis, the wound beds of the animals treated with CH were considerably smaller than those of the controls. Histological analysis revealed lack of a reactive or a granulomatous inflammatory reaction in skin lesions with CH and the absence of pathological abnormalities in the organs obtained by necropsy, which supported the local and systemic histocompatibility of the biomaterial. The present results suggest that this biomaterial may aid the re-establishment of skin architecture.

Foamed beverages, such as cappuccino, have become very popular with consumers in recent years. Though the main appeal of such products lies in their milky frothy top, there is a lack of understanding on the liquid properties and process parameters driving froth quality. There are also no reliable methods to evaluate foam characteristics, since most studies to date focus on avoiding milk foaming during packaging and heat treatment, or on the behaviour of pure protein foams. The present study aims to understand the mechanisms of foam formation in milk, with a view to producing a froth that is more appealing to consumers. A methodology to characterize and distinguish between milk foams generated by two main methods—mechanical agitation and steam injection—is presented. The methodology involves characterizing the foam in terms of initial bubble hold-up, foam destabilization mechanisms and kinetics. Observation on foams formed by steam injection revealed that steam injection time does not have a significant effect on initial bubble hold-up even though it increases general foam stability. The increase on foam stability is most probably related to the greater extent of protein denaturation induced by increasing steam injection time. In the case of mechanically whipped milk foams, it was observed that higher milk temperatures resulted in dispersions having a lower bubble hold-up. The overall stability of the higher temperature foam expressed in terms of foam-to-liquid ratio was also lower as initial milk temperature increased. Higher milk temperatures induced by increasing steam injection time didn't affect foam stability, whereas whipping at higher temperatures had a strong destabilizing effect. This suggests that mechanisms of interface formation by the two methods differ and reinforces that an understanding of the changes occurring in milk during aeration by steam injection is essential to establish the differences between foams generated by both processes.

A pele é o maior órgão do corpo humano cuja função é comprometida pela ocorrência de feridas. O tratamento de feridas representa uma fracção considerável dos gastos em saúde, sendo o desenvolvimento de novos métodos de tratamento alvo de grande interesse. Uma das vertentes desta investigação é a utilização de novas matérias-primas na produção de dispositivos médicos(DM) para o tratamento de feridas. O quitosano é um derivado da quitina, o segundo biopolímero mais abundante. As propriedades biológicas do quitosano tornam-no um bom candidato à produção de dispositivos médicos. Este trabalho teve como objectivo o desenvolvimento de DM para o tratamento de feridas à base de quitosano. Foram desenvolvidos três dispositivos: um hidrogel obtido a partir da coagulação de uma solução de quitosano, uma matriz porosa por liofilização, e uma matriz combinada de microfibras e nanofibras por fiação húmida e electrofiação, respectivamente. Verificou-se que o quitosano acelera o processo de cicatrização de feridas, levando a uma diminuição mais rápida do seu tamanho quando comparado com o tratamento tradicional e uma reepitelização compatível com um processo de regeneração adequado. O melhor desempenho no tratamento de feridas foi obtido com a utilização da matriz combinada pela conjugação das propriedades biológicas do quitosano com a elevada área superficial das nanofibras. Neste trabalho foram comparados pela primeira vez em paralelo três produtos à base de quitosano com características distintas como DM para o tratamento de feridas. O sucesso da concepção e desenvolvimento do hidrogel e da matriz porosa de quitosano permitiu a sua certificação e industrialização com os nomes comerciais HidroKi® e AbsorKi®, respectivamente. Concluiu-se que o quitosano é um material adequado à produção de DM inovadores e que pode ser manipulável em estruturas para diferentes aplicações.