The development of natural based, effective and protective wound dressings associated to local treatment applied on chronic wounds, represents a major challenge nowadays. In this work chitosan-based films were prepared with different concentrations of ethanolic ultrasound assisted extracts from Cynara cardunculus leaves (EtPUAE). The physico-chemical film properties revealed that extract incorporation influences the volumetric swelling capacity and mechanical properties of the films, leading to materials with a lower fluid absorption capacity and more fragile. However, no impact was detected on the thermal properties of the films, as well as on their dense structure characterized by Scanning Electronic Microscopy (SEM) analysis. Biological screening of chitosan-based films show that chitosan with a 1% (w/w) and a 5% (w/w) EtPUAE loading did not induce cytotoxicity on normal human skin fibroblasts (Bj5-ta cell line), mainly attributed to cynaropicrin (extract key active compound) present in the film below its IC50 value. Nevertheless, chitosan-based films with 5% (w/w) EtPUAE presented an interesting anti-inflammatory activity. Bj5-ta cells stimulated with liposaccharides (LPS), presented a reduction of 86% on IL-6 cytokine levels, after exposure to chitosan with 5% EtPUAE film extract. The results obtained in this study open up the possibility of successfully using chitosan films doped with EtPUAE for development of chronic wound dressings, with the advantage of using naturally-sourced materials with anti-inflammatory activity

Atualmente, nenhum penso utilizado clinicamente em feridas crónicas, mais especificamente em queimaduras, providencia adesão, hidratação, força mecânica semelhante à matriz extracelular natural (MEC) da pele e capacidade de ser removido sem causar trauma. Os hidrogéis surgem como uma alternativa promissora devido à sua capacidade de manter um ambiente húmido no local da ferida e, ao mesmo tempo, absorver o exsudato, às suas propriedades mecânicas versáteis e à competência de proteção contra infeções bacterianas. Os hidrogéis estímulo responsivos trazem a possibilidade de controlar a degradação dos hidrogéis, sem causar dor ao doente, colmatando uma das maiores desvantagens dos pensos tradicionais. Os hidrogéis foto responsivos são uma excelente opção devido às características inócuas da luz visível para os tecidos humanos. Utilizou-se a reação de click para sintetizar os hidrogéis, ao fazer reagir o polietilenoglicol funcionalizado com a polietilenoimina (PEI), resultando em uma ligação estéreo especifica de β-aminoacrilato facilmente clivável por oxigénio singleto (1O2). A caracterização química dos precursores foi realizada por ressonância magnética nuclear de protão (1H NMR) e espetroscopia de transformada de Fourier no infravermelho, no modo de refletância total atenuada (ATR-FTIR). O impacto do peso molecular da PEI nas propriedades dos hidrogéis foi determinado. Os hidrogéis apresentam uma capacidade de inchaço entre 139% e 404% o seu peso inicial, dependendo do peso molecular da PEI e da percentagem em massa utilizado na síntese dos hidrogéis. A caracterização das propriedades mecânicas revelou uma resistência à compressão máxima de 139.3 kPa. O ensaio de adesão revelou que os hidrogéis aderem à superfície do tecido com uma força média entre 1.6 e 5.2 N/cm2. A morfologia de superfície e a capacidade de eliminação de ROS pelo hidrogel foi também analisada. Esta dissertação propõe um mecanismo promissor para facilitar a degradação dos hidrogéis inspirado na terapia fotodinâmica. O mecanismo baseia-se na incorporação de um fotossensibilizador (PS) dentro da matriz polimérica do hidrogel. Após irradiação com um comprimento de onda adequado, o PS gera 1O2 capaz de degradar as ligações β-aminoacrilato presentes na estrutura do hidrogel. O sucesso do mecanismo proposto foi investigado quimicamente por ATR-FTIR. As propriedades físicas dos hidrogéis após irradiação foram avaliadas através da análise das propriedades mecânicas, da morfologia de superfície, da geração de 1O2 in vitro e através de testes de degradação por ação da luz e do pH. Uma perda visível das propriedades do hidrogel ocorre após irradiação, confirmando a capacidade promissora de dissolução in situ do hidrogel. Estudos de citocompatibilidade foram efetuados nos hidrogéis com e sem irradiação, destacando a boa citocompatibilidade e segurança dos hidrogéis sintetizados com PEI1.8k e 30% wt. após serem irradiados.

Despite all the efforts that have been done up to now, the currently available wound dressings are still unable to fully re-establish all the structural and functional properties of the native skin. To overcome this situation, researchers from the tissue engineering area have been developing new wound dressings (hydrogels, films, sponges, membranes) aiming to mimic all the features of native skin. Among them, asymmetric membranes emerged as a promising solution since they reproduce both epidermal and dermal skin layers. Wet or dry/wet phase inversion, scCO2-assisted phase inversion, and electrospinning have been the most used techniques to produce such a type of membranes. Among them, the electrospinning technique, due to its versatility, allows the development of multifunctional dressings, using natural and/or synthetic polymers, which resemble the extracellular matrix of native skin as well as address the specific requirements of each skin layer. Moreover, various therapeutic or antimicrobial agents have been loaded within nanofibers to further improve the wound healing performance of these membranes. This review article provides an overview of the application of asymmetric electrospun membranes as wound dressings displaying antibacterial activity and as delivery systems of biomolecules that act as wound healing enhancers.

Hydrogels are considered to be the most ideal materials for the production of wound dressings since they display a three-dimensional structure that mimics the native extracellular matrix of skin as well as a high-water content, which confers a moist environment at the wound site. Until now, different polymers have been used, alone or blended, for the production of hydrogels aimed for this biomedical application. From the best of our knowledge, the application of a xanthan gum-konjac glucomannan blend has not been used for the production of wound dressings. Herein, a thermo-reversible hydrogel composed of xanthan gum-konjac glucomannan (at different concentrations (1% and 2% w/v) and ratios (50/50 and 60/40)) was produced and characterized. The obtained data emphasize the excellent physicochemical and biological properties of the produced hydrogels, which are suitable for their future application as wound dressings.

The electrospinning has been widely used in tissue engineering for the preparation of wound dressing with the most varied polymers and drugs. Considering that propolis has antimicrobial and anti-inflammatory characteristics, the aim was to develop electrospun fibers from PBAT (poly (butylene-adipate-co-terephthalate)/PCL (poly(ε-caprolactone) containing propolis in order to promote antimicrobial action and the healing of wounds. By the optical microscopy analysis, the best parameter for obtaining the fibers was chosen: 16.5% (v/v) of propolis extract alcoholic solution, 14.0 cm needle-collector distance, 17.0 kV of voltage and 0.5 mL h-1 flow rate. The scanning electron microscopy demonstrated fiber diameters of 0.51 ± 0.12 μm for the polymer blend and 1.16 ± 0.98 μm for the blend with propolis. The Fourier transform infrared spectroscopy (FTIR) results showed no evidence of chemical interaction with propolis, this being a physical interaction. This interaction was corroborated by the differential scanning calorimetry (DSC) due to the variation in the heats involved, mainly in the aromatic part of the polymer blend, indicating a better interaction in the PBAT group. Finally, it was found that fibers presents propolis antimicrobial activity against the bacteria Pseudomonas Aeruginosa. The results indicate that this blend has a great potential to be used as a cutaneous dressing.

Abstract Electrospun nanofibers from gelatin (G), chitosan (CS), and chitosan-polyvinyl alcohol (CS-PVA) were developed by electrospinning process. Mechanical properties were determined by the tensile test, the elastic modulus values of the nanofibers were G (15.418-34.34 MPa) and CS-PVA (17.44-126.427 MPa). The morphological characterization by SEM revealed that the systems with 15% G and 6% CS-PVA showed morphological homogeneity. Structural characterization by FTIR indicated an interaction among some functional groups of the component. Thermal analysis by DSC and TGA showed degradation temperatures for G (330 °C), CS (210 °C to 370 °C), and PVA (310 °C to 420 °C). The contact angles values denoted the hydrophilic nature of the material. Finally, the antimicrobial assay proved that both 15% G and 7% PVA on the CS-PVA system presented the best antimicrobial effect. The results indicate that the electrospun nanofibers fabricated with G or CS-PVA can be used as wound healing dressings.

Abstract Recently, latex (NRL) and natural rubber (NR) from Hevea brasiliensis have emerged as promising biomaterials from renewable sources for biomedical applications. Although some attempts at commercial applications have been made, there is a need to comprehensively document the state-of-the-art of these biopolymers for biomedical applications and regenerative medicine. Here we present the recent advances in the development of NRL and NR as biomedical materials with potential properties including biocompatibility and biodegradability. Due to the angiogenic properties of NRL and NR, well-defined functional materials can be used for drug delivery systems (oral/transdermal), scaffolds for skin and bone regeneration, and dressings for wound healing. The incorporation of drugs, nanoparticles, cells, and others into NRL and NR polymer chains offers a wide range of applications such as dressings with antimicrobial activity and sustained release systems. Concluding remarks on the growth of these biomaterials for biomedical applications and regenerative medicine were discussed.

Abstract In this work, NRL films were enriched with red propolis and silver nanoparticles with the aim of obtaining dressings with bactericide properties. To improve the properties of these materials, plasma treatment was also applied to the films. Cytotoxic effects were evaluated by MTT and agar diffusion assays on secondary and stem cells. Determination of cell behavior on the films were assessed by EDS and FEG-SEM. In general, the plasma modified NRL films presented hydrophilic character, favorable condition for biomedical applications. RBS results showed that silver is probably in nanoparticulate form. MTT assays revealed that non-cytotoxic effects were observed for all the samples extracts. Either the plasma treatment or silver deposition were effective in sterilizing the samples and modifying their surfaces. It was demonstrated in this in vitro study that ADSCs associated with NRL films enriched with propolis should be considered promising for application in the healing of occlusive wounds.

This study compares a wound dressing based on bacterial cellulose/collagen (BC/COL) hydrogel in rat dorsum with commercial collagenase ointment and untreated wound. The hydrogel was characterized by Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier transformed - Infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). According to the In vivo test and macroscopic evaluation, BC/COL hydrogel showed a better repair of wounds and promoted statistically significant differences of tissue repair between treatments on the 7th day after surgery. Better quality, quantity and orientation evaluation of collagen fibers (p=0.0001) were observed in the BC/COL hydrogel and collagenase ointment groups in relation to the control group. The BC/COL hydrogel promoted better wound healing than collagenase and the control group, therefore, it can be considered a potential wound dressing for skin regeneration.