Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- 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.
- Functionalization and photocuring of an L-lactic acid macromer for biomedical applicationsPublication . Marques, Dina; Santos, João; Ferreira, Paula; Correia, Tiago R.; Correia, Ilídio Joaquim Sobreira; Gil, Maria; Baptista, Cristina Maria dos Santos GaudêncioL-lactic acid was the starting material for obtaining bioahesives. Reaction with 1,4-butanediol provided a telechelic lactic acid prepolymer with hydroxyl end groups further functionalized with 2-isocyanatoethyl methacrylate. Films were produced upon UV irradiation, 2 min, after addition of Irgacure 2959. This was a solvent and catalyst free process. Thermal characterization of films confirmed stability at physiological temperature, enabling photocuring. Adhesion properties were assessed with good results. In vitro degradation tests showed moderate hydrolytic instability dependent on thickness. SEM images revealed a uniform and compact structure. Thrombosis tests confirmed the materials’ thrombogenicity while biocompatibility experiments showed fibroblast viability and antimicrobial behavior.
- Photocurable bioadhesive based on lactic acidPublication . Marques, Dina; Santos, João; Ferreira, Paula; Correia, Tiago R.; Correia, Ilídio Joaquim Sobreira; Gil, Maria; Baptista, Cristina Maria dos Santos GaudêncioNovel photocurable and low molecular weight oligomers based on l-lactic acid with proven interest to be used as bioadhesive were successfully manufactured. Preparation of lactic acid oligomers with methacrylic end functionalizations was carried out in the absence of catalyst or solvents by self-esterification in two reaction steps: telechelic lactic acid oligomerization with OH end groups and further functionalization with methacrylic anhydride. The final adhesive composition was achieved by the addition of a reported biocompatible photoinitiator (Irgacure® 2959). Preliminary in vitro biodegradability was investigated by hydrolytic degradation in PBS (pH = 7.4) at 37 °C. The adhesion performance was evaluated using glued aminated substrates (gelatine pieces) subjected to pull-to-break test. Surface energy measured by contact angles is lower than the reported values of the skin and blood. The absence of cytoxicity was evaluated using human fibroblasts. A notable antimicrobial behaviour was observed using two bacterial models (Staphylococcus aureus and Escherichia coli). The cured material exhibited a strong thrombogenic character when placed in contact with blood, which can be predicted as a haemostatic effect for bleeding control. This novel material was subjected to an extensive characterization showing great potential for bioadhesive or other biomedical applications where biodegradable and biocompatible photocurable materials are required.
- Preparation and chemical and biological characterization of a pectin/chitosan polyelectrolyte complex scaffold for possible bone tissue engineering applicationsPublication . Coimbra, Patrícia; Ferreira, Paula; Sousa, Hermínio C. de; Batista, Patrícia Sofia Pinhanços; Rodrigues, Miguel; Correia, Ilídio Joaquim Sobreira; Gil, MariaIn this work, porous scaffolds obtained from the freeze-drying of pectin/chitosan polyelectrolyte complexes were prepared and characterized by FTIR, SEM and weight loss studies. Additionally, the cytotoxicity of the prepared scaffolds was evaluated in vitro, using human osteoblast cells. The results obtained showed that cells adhered to scaffolds and proliferated. The study also confirmed that the degradation by-products of pectin/chitosan scaffold are noncytotoxic.
- Engineering star-shaped lactic acid oligomers to develop novel functional adhesivesPublication . Santos, João; Travassos, Diana Rita Sousa; Ferreira, Paula; Marques, Dina; Gil, Maria; Miguel, Sónia; Ribeiro, MP.; Correia, Ilídio Joaquim Sobreira; Baptista, CristinaDirect polycondensation of L-lactic acid with a comonomer allows tailoring the properties of the product from the very first step. The viscous L-lactic acid co-oligomers with star-shaped architectures obtained were modified with three different acrylate monomers. Regardless the functionalization agent, UV curing was fast and all materials were cell compatible and promoted cell adhesion. The physical properties of the three star-shaped films exhibited a consistent trend as swelling capacity, hydrolytic instability, and gel content decreased simultaneously. A higher network density increased crosslinking degree and gel content among the films with an isocyanate group. The methacrylic end group functionalized material, lowest molecular weight, consistently exhibited the higher hydrolytic instability. Comparison of physical properties of these films with the corresponding linear materials reported previously confirmed the influence of precursor molecular architecture on the final material. The methodology developed herein is prone to scale-up and lead to the industrial production of new bioadhesives.