Loading...
21 results
Search Results
Now showing 1 - 10 of 21
- Electrospun polymeric nanofibres as wound dressings: A reviewPublication . Miguel, Sónia P.; Figueira, Daniela Sofia Rodrigues; Simões, Déborah; Ribeiro, MP.; Coutinho, Paula; Ferreira, Paula; Correia, Ilídio Joaquim SobreiraSkin wounds have significant morbidity and mortality rates associated. This is explained by the limited effectiveness of the currently available treatments, which in some cases do not allow the reestablishment of the structure and functions of the damaged skin, leading to wound infection and dehydration. These drawbacks may have an impact on the healing process and ultimately prompt patients’ death. For this reason, researchers are currently developing new wound dressings that enhance skin regeneration. Among them, electrospun polymeric nanofibres have been regarded as promising tools for improving skin regeneration due to their structural similarity with the extracellular matrix of normal skin, capacity to promote cell growth and proliferation and bactericidal activity as well as suitability to deliver bioactive molecules to the wound site. In this review, an overview of the recent studies concerning the production and evaluation of electrospun polymeric nanofibrous membranes for skin regenerative purposes is provided. Moreover, the current challenges and future perspectives of electrospun nanofibrous membranes suitable for this biomedical application are highlighted.
- New drug-eluting lenses to be applied as bandages after keratoprosthesis implantationPublication . Carreira, Ana; Ferreira, Paula; Ribeiro, MP.; Correia, Tiago R.; Coutinho, Paula Isabel Teixeira Gonçalves; Correia, Ilídio Joaquim Sobreira; Gil, MariaCorneal tissue is the most commonly transplanted tissue worldwide. This work aimed to develop a new drug-eluting contact lens that may be used as a bandage after keratoprosthesis. During this work, films were produced using poly(vinyl alcohol) (PVA) and chitosan (CS) crosslinked with glyoxal (GL). Vancomycin chlorhydrate (VA) was impregnated in these systems by soaking. Attenuated total reflectance – Fourier transform infrared spectroscopy was used to confirm crosslinking. The cytotoxic and drug release profile, hydrophilicity, thermal and biodegradation as well as swelling capacity of the samples were assessed through in vitro studies. PVA and PVA/CS films were obtained by crosslinking with GL. The films were transparent, flexible with smooth surfaces, hydrophilic and able to load and release vancomycin for more than 8 h. Biodegradation in artificial lachrymal fluid (ALF) with lysozyme at 37 °C showed that mass loss was higher for the samples containing CS. Also, the samples prepared with CS showed the formation of pores which were visualized by SEM. All samples revealed a biocompatible character after 24 h in contact with cornea endothelial cells. As a general conclusion it was possible to determine that the 70PVA/30CS film showed to combine the necessary features to prepare vancomycin-eluting contact lenses to prevent inflammation after corneal substitution.
- Dual on–off and off–on switchable oligoaziridine biosensorPublication . Raje, Vivek; Morgado, Patrícia I.; Ribeiro, MP.; Correia, Ilídio Joaquim Sobreira; Bonifácio, Vasco; Branco, Paula S.; Ricardo, Ana AguiarA water-soluble biocompatible aziridine-based biosensor with pendant anthracene units was synthesized by radicalar polymerization of N-substituted aziridines in supercritical carbon dioxide. The binding ability of the sensor towards a series of metal ions was examined by comparing the fluorescence intensities of the solutions before and after the addition of 100 equivalents of a solution of the metal ion chloride salt. A fast, simple and highly optical sensitive dual behavior, “off–on” and “on–off” response, was observed after the biosensor was exposed to the metal cations in aqueous solution. Zinc presented the highest fluorescence enhancement (turn-on) and copper presented the highest fluorescence quenching (turn-off). The response time was found to be instantaneous and the detection limit was achieved even in the presence of excess metal cation competitors. By using immunofluorescence microscopy it was also shown that oligoaziridine acts as an “on–off” probe through highly sensitive (detection limit of 1.6 nM), selective and reversible binding to copper anions under physiologic conditions using living Human Fibroblast cells. The stoichiometry for the reaction of the biosensor with Cu2+ was determined by a Job plot and indicates the formation of an oligoaziridine-Cu2+ 1:2 adduct.
- Poly(vinyl alcohol)/chitosan asymmetrical membranes: Highly controlled morphology toward the ideal wound dressingPublication . Morgado, Patrícia I.; Lisboa, Pedro; Ribeiro, MP.; Miguel, Sónia P.; Simões, Pedro; Correia, Ilídio Joaquim Sobreira; Ricardo, Ana AguiarAsymmetrical membranes have been reported as ideal wound dressings for skin regeneration. The usual methods (dry/wet-phase inversion) to produce those specific membranes are time consuming, and in majority of the cases demand the use of harmful organic solvents. In this study, supercritical carbon dioxide (scCO2)-assisted phase inversion method was applied to prepare poly(vinyl alcohol)/chitosan (PVA/CS) asymmetrical membranes. This technique can tailor the final structure of the dressing by tuning the processing conditions allowing the development of high porous materials with optimized morphology, mechanical properties and hydrophilicity. The PVA/CS dressings produced are recovered in a dry state but can form a hydrogel due to their high water uptake ability maintaining the moisturized environment needed for wound healing. The dressing presents a top thin layer of about 15 µm that allows gaseous exchange while barricading the penetration of microorganisms, and a sponge bottom layer that is able to remove excess exudates. A mathematical model based on Fick׳s second law of diffusion was developed to describe the pharmacokinetic release profile of a small drug (ibuprofen) from the swollen membrane in physiological conditions that mimic the wound. In vitro studies revealed that the dressings had excellent biocompatibility and biodegradation properties adequate for skin wound healing.
- Development of a novel hydrogel for skin regenerationPublication . Miguel, Sónia P.; Ribeiro, MP.; Correia, Ilídio Joaquim SobreiraSkin lesions are traumatic events that lead to increased fluid loss, infections, scars formation and the appearance of immunocompromised regions. The loss of skin integrity can result in significant physiological imbalances and disability or even death. So far, different wound dressings have been developed. Among them, hydrogels are the most applied. Herein, a thermoresponsive hydrogel was produced using chitosan and agarose formed at body temperature (37°C), in order to verify their applicability in the treatment of wounds. Hydrogel bactericidal activity, biocompatibility, morphology, porosity and wettability were characterized by confocal microscopy, MTS assay and SEM. The attained results revealed that hydrogel has a pore size (90–400 µm) compatible with cellular internalization and proliferation. A bactericidal activity was observed for hydrogels containing more than 188 µg/mL of chitosan. The results obtained demonstrated that this 3D network has the suitable properties for improving the healing process of cutaneous wounds.
- Desenvolvimento de um novo hidrogel de quitosano para futura aplicação como substituto de pelePublication . Ribeiro, Maximiano José Prata; Correia, Ilídio Joaquim SobreiraA pele é o maior órgão do corpo humano e está envolvida na preservação da homeostase dos fluidos do corpo, na regulação térmica e na protecção contra agentes infecciosos. Após uma lesão, a pele tem de ser revestida de forma a diminuir a dor, a contaminação, o risco de infecção e a desidratação do paciente. O processo de regeneração de uma lesão cutânea é complexo e envolve uma resposta integrada de vários tipos de células e factores de crescimento. No presente estudo foi avaliado a aplicabilidade de um hidrogel, à base de quitosano, no tratamento de lesões de pele. A morfologia do hidrogel foi caracterizada através de imagens de microscopia electrónica de varrimento. A biocompatibilidade e biodegrabilidade deste biomaterial foi avaliada através de ensaios in vitro e in vivo. Os fibroblastos isolados da pele de ratos Wistar, foram usados como modelos nos ensaios in vitro, de modo a avaliar a citotoxicidade do hidrogel. Os fibroblastos aderiram e proliferaram na presença do biomaterial em estudo, o que permitiu concluir a ausência de citotoxicidade deste, assim como dos produtos resultantes da sua degradação. A aplicabilidade do hidrogel no tratamento de lesões cutâneas foi avaliada em ratos Wistar, por indução de lesões profundas na pele. O processo de cicatrização da lesão foi monitorizado macroscopicamente e por análise histológica. A análise macroscópica revelou que as queimaduras dos animais tratados com o hidrogel de quitosano cicatrizaram mais rapidamente do que os animais usados como controlo. A análise histológica revelou a ausência de reacção inflamatória ou anormalidades patológicas nos órgãos obtidos por necrópsia nos animais tratados com o hidrogel, o que suporta a histocompatibilidade local e sistémica do biomaterial. Os resultados obtidos sugerem que este biomaterial poderá ajudar a restabelecer a estrutura da pele.
- Development of a new chitosan hydrogel for wound dressingPublication . Ribeiro, MP.; Espiga, Ana; Silva, Daniela; Baptista, Patrícia; Henriques, Joaquim; Ferreira, Catarina L.; Silva, Jorge; Borges, João; Pires, Eduardo; Chaves, Paula; Correia, Ilídio Joaquim SobreiraWound 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.
- Thermoresponsive chitosan–agarose hydrogel for skin regenerationPublication . Miguel, Sónia P.; Ribeiro, MP.; Brancal, Hugo Gonçalo Monteiro Silva Aguiar; Coutinho, Paula Isabel Teixeira Gonçalves; Correia, Ilídio Joaquim SobreiraHealing enhancement and pain control are critical issues on wound management. So far, different wound dressings have been developed. Among them, hydrogels are the most applied. Herein, a thermoresponsive hydrogel was produced using chitosan (deacetylation degree 95%) and agarose. Hydrogel bactericidal activity, biocompatibility, morphology, porosity and wettability were characterized by confocal microscopy, MTS assay and SEM. The performance of the hydrogel in the wound healing process was evaluated through in vivo assays, during 21 days. The attained results revealed that hydrogel has a pore size (90–400 μm) compatible with cellular internalization and proliferation. A bactericidal activity was observed for hydrogels containing more than 188 μg/mL of chitosan. The improved healing and the lack of a reactive or a granulomatous inflammatory reaction in skin lesions treated with hydrogel demonstrate its suitability to be used in a near future as a wound dressing.
- Biocompatible Polyurea Dendrimers with pH‐Dependent FluorescencePublication . Restani, Rita; Morgado, Patrícia I.; Ribeiro, MP.; Correia, I.J.; Ricardo, Ana Aguiar; Bonifácio, VascoBiocompatible and biodegradable water‐soluble dendrimers comprising ureas within the interior and amino groups on the periphery were synthesized in supercritical carbon dioxide (dendrimer of generation 1 shown in picture). This novel class of dendrimers shows a pH‐dependent intrinsic blue fluorescence at very low concentrations, which makes them potential polymeric fluorescent cell markers.
- Synthesis and characterization of a photocrosslinkable chitosan–gelatin hydrogel aimed for tissue regenerationPublication . Saraiva, Sofia Mendes; Miguel, Sónia P.; Ribeiro, MP.; Coutinho, Paula Isabel Teixeira Gonçalves; Correia, Ilídio Joaquim SobreiraIn the area of tissue engineering different approaches have been studied, so far, for promoting regeneration or replacement of damaged tissues. Among the different materials developed, hydrogels, due to their biocompatibility and similarities with the native extracellular matrix, have emerged as suitable candidates for being used for different therapeutic purposes. Herein, photocrosslinkable hydrogels, composed by chitosan methacrylamide (ChMA) and gelatin methacrylamide (GelMA) were crosslinked by ultraviolet (UV) light, using Irgacue 2959 as photoinitiator. The morphological, physicochemical and biological properties of the hydrogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance. The obtained results demonstrated that the developed hydrogels possess suitable properties for being used as 3D constructs on several areas of tissue engineering. Furthermore, these properties may allow their future application as space filling agents or as delivery vehicles of bioactive molecules and cells.
- «
- 1 (current)
- 2
- 3
- »