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- 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.
- Production and characterization of chitosan/gelatin/β-TCP scaffolds for improved bone tissue regenerationPublication . Serra, Inês Raquel Tavares; Fradique, Ricardo Gil; Vallejo, Mariana C. da S.; Correia, Tiago R.; Miguel, Sónia P.; Correia, Ilídio Joaquim SobreiraRecently, bone tissue engineering emerged as a viable therapeutic alternative, comprising bone implants and new personalized scaffolds to be used in bone replacement and regeneration. In this study, biocompatible scaffolds were produced by freeze-drying, using different formulations (chitosan, chitosan/gelatin, chitosan/β-TCP and chitosan/gelatin/β-TCP) to be used as temporary templates during bone tissue regeneration. Sample characterization was performed through attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction and energy dispersive spectroscopy analysis. Mechanical characterization and porosity analysis were performed through uniaxial compression test and liquid displacement method, respectively. In vitro studies were also done to evaluate the biomineralization activity and the cytotoxic profile of the scaffolds. Scanning electron and confocal microscopy analysis were used to study cell adhesion and proliferation at the scaffold surface and within their structure. Moreover, the antibacterial activity of the scaffolds was also evaluated through the agar diffusion method. Overall, the results obtained revealed that the produced scaffolds are bioactive and biocompatible, allow cell internalization and show antimicrobial activity against Staphylococcus aureus. Such, make these 3D structures as potential candidates for being used on the bone tissue regeneration, since they promote cell adhesion and proliferation and also prevent biofilm development at their surfaces, which is usually the main cause of implant failure.
- Coaxial electrospun PCL/Gelatin-MA fibers as scaffolds for vascular tissue engineeringPublication . Coimbra, Patrícia; Santos, Patrícia; Alves, Patrícia; Miguel, Sónia P.; Carvalho, Marco António Paulo de; Sá, Kevin; Correia, Ilídio Joaquim Sobreira; Ferreira, PaulaCoaxial electrospinning is a technique that allows the production of nanofibers with a core–shell structure. Such fibers present several advantages as materials for the preparation of scaffolds, namely due to the possibility of combining a core with the desired mechanical properties with a shell prepared from biocompatible materials that will establish proper interactions with the host. Herein, core-shell fibrous meshes, composed of a polycaprolactone (PCL) core and a functionalized gelatin shell, were prepared by coaxial electrospinning and then photocrosslinked under UV light aiming to be used in vascular tissue regeneration. The suitability of the meshes for the pretended biomedical application was evaluated by assessing their chemical/physical properties as well as their haemo and biocompatibility in vitro. The obtained results revealed that meshes’ shell prepared with a higher content of gelatin showed fibers with diameters presenting a unimodal distribution and a mean value of 600 nm. Moreover, those fibers with higher content of gelatin also displayed lower water contact angles, and therefore higher hydrophilicities. Such features are crucial for the good biologic performance displayed by these meshes, when in contact with blood and with Normal Human Dermal Fibroblasts cells.
- 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.
- Photocrosslinkable electrospun fiber meshes for tissue engineering applicationsPublication . Ferreira, Paula; Santos, Patrícia; Alves, P.; Carvalho, Marco António Paulo de; Sá, Kevin; Miguel, Sónia P.; Correia, Ilídio Joaquim Sobreira; Coimbra, Patrícia Manuela AlmeidaElectrospun polymeric meshes are known to exhibit promising properties for the regeneration of several soft tissues. Herein, electrospun polymeric meshes were prepared from blends of polycaprolactone and functionalized gelatin. The meshes were then photocrosslinked under UV light using Irgacure® 2959 as the photoinitiator, aiming to improve membranes’ stability in biological fluids. Moreover, meshes suitability to be used as vascular grafts was evaluated by characterizing their chemical/physical properties as well as their haemo and biocompatibility in vitro. The obtained results show that the blended polymeric meshes are biodegradable and those with a higher content of gelatin display a lower water contact angle. Blood compatibility studies showed that the photocrosslinked membranes are haemocompatible, i.e. they display low values of thrombogenicity and do not trigger any haemolytic effect. Also, Normal Human Dermal Fibroblasts cells were incubated in the presence of the produced membranes and they were able to adhere and proliferate, thus revealing the biocompatibility of the photocrosslinked meshes.
- Production of new 3D scaffolds for bone tissue regeneration by rapid prototypingPublication . Fradique, Ricardo Gil; Correia, Tiago R.; Miguel, Sónia P.; Sá, Kevin; Figueira, Daniela Sofia Rodrigues; Mendonça, António; Correia, Ilídio Joaquim SobreiraThe incidence of bone disorders, whether due to trauma or pathology, has been trending upward with the aging of the worldwide population. The currently available treatments for bone injuries are rather limited, involving mainly bone grafts and implants. A particularly promising approach for bone regeneration uses rapid prototyping (RP) technologies to produce 3D scaffolds with highly controlled structure and orientation, based on computer-aided design models or medical data. Herein, tricalcium phosphate (TCP)/alginate scaffolds were produced using RP and subsequently their physicochemical, mechanical and biological properties were characterized. The results showed that 60/40 of TCP and alginate formulation was able to match the compression and present a similar Young modulus to that of trabecular bone while presenting an adequate biocompatibility. Moreover, the biomineralization ability, roughness and macro and microporosity of scaffolds allowed cell anchoring and proliferation at their surface, as well as cell migration to its interior, processes that are fundamental for osteointegration and bone regeneration.
- 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.
- 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.
- In Vivo High-Content Evaluation of Three-Dimensional Scaffolds BiocompatibilityPublication . Oliveira, Mariana; Ribeiro, MP.; Miguel, Sónia; Neto, Ana; Coutinho, Paula Isabel Teixeira Gonçalves; Correia, Ilídio Joaquim Sobreira; Mano, João F.While developing tissue engineering strategies, inflammatory response caused by biomaterials is an unavoidable aspect to be taken into consideration, as it may be an early limiting step of tissue regeneration approaches. We demonstrate the application of flat and flexible films exhibiting patterned high-contrast wettability regions as implantable platforms for the high-content in vivo study of inflammatory response caused by biomaterials. Screening biomaterials by using high-throughput platforms is a powerful method to detect hit spots with promising properties and to exclude uninteresting conditions for targeted applications. High-content analysis of biomaterials has been mostly restricted to in vitro tests where crucial information is lost, as in vivo environment is highly complex. Conventional biomaterials implantation requires the use of high numbers of animals, leading to ethical questions and costly experimentation. Inflammatory response of biomaterials has also been highly neglected in high-throughput studies. We designed an array of 36 combinations of biomaterials based on an initial library of four polysaccharides. Biomaterials were dispensed onto biomimetic superhydrophobic platforms with wettable regions and processed as freeze-dried three-dimensional scaffolds with a high control of the array configuration. These chips were afterward implanted subcutaneously in Wistar rats. Lymphocyte recruitment and activated macrophages were studied on-chip, by performing immunocytochemistry in the miniaturized biomaterials after 24 h and 7 days of implantation. Histological cuts of the surrounding tissue of the implants were also analyzed. Localized and independent inflammatory responses were detected. The integration of these data with control data proved that these chips are robust platforms for the rapid screening of early-stage in vivo biomaterials' response.
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