Percorrer por autor "Marto-Costa, Carolina"
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- Free-standing, water-resistant, and conductivity-enhanced PEDOT:PSS films from in situ polymerization of 3-hydroxymethyl-3-methyl-oxetanePublication . Jorge, Sara M.; Santos, Luís F.; Ferreira, Maria João; Marto-Costa, Carolina; Serro, Ana Paula; Galvão, Adelino M.; Morgado, Jorge; Charas, AnaFree-standing films based on conducting polymers, such as poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS), offer many benefits over traditional metal electrodes for applications in flexible electronics. However, to ensure structural integrity when contacting aqueous environments and high levels of electrical conductivity, solution-processed polymers require additives that act as crosslinking agents and conductivity enhancers. In this work, a new approach is presented to fabricate water-resistant free-standing films of PEDOT:PSS and simultaneously increase their conductivity, using an oxetane compound as an additive. It is shown that at moderate temperatures, oxetane polymerizes within the PEDOT:PSS acidic medium, forming hydroxymethyl-substituted polyether compounds that form a network upon crosslinking with PSS. The polymer composite films show self-sustainability, structural stability in aqueous environments, and enhanced conductivity. Finally, the potential of the free-standing films as health-monitoring electrodes, specifically for human electrocardiography, is explored.
- Improved triamcinolone acetonide-eluting contact lenses based on cyclodextrins and high hydrostatic pressure assisted complexationPublication . Marto-Costa, Carolina; Toffoletto, Nadia; Salema-Oom, Madalena; Antunes, Alexandra M.M.; Pinto, Carlos A.; Saraiva, Jorge A.; Silva-Herdade, Ana S.; Alvarez-Lorenzo, Carmen; Serro, Ana PaulaContact lenses (CLs) constitute an advantageous platform for the topical release of corticosteroids due to their prolonged contact with the eye. However, the lipophilic nature of corticosteroids hampers CLs' ability to release therapeutic amounts. Two approaches to improve loading and release of triamcinolone acetonide (TA) from poly(2-hydroxyethyl methacrylate)-based hydrogels were investigated: adding 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) to the monomers solution before polymerization (HEMA/i-CD) and an hydrogels' post-treatment with HP-β-CD (HEMA/p-CD). The effect of HP-β-CD and sterilization by high hydrostatic pressure (HHP) on the hydrogel properties (water content, oxygen and ion permeability, roughness, transmittance, and stiffness) was evaluated. The HEMA/i-CD hydrogels had stronger affinity for TA, sustaining its release for one day. HHP sterilization promoted the formation of cyclodextrin-TA complexes within the hydrogels, improving their drug-loading capacity »60 %. Cytotoxicity and irritability tests confirmed the safety of the therapeutic CLs. TA released from the hydrogels permeated through ocular tissues ex vivo and showed anti-inflammatory activity. Finally, a previously validated mathematical model was used to estimate the ability of the TA-loaded CLs to deliver therapeutic drug concentrations to the posterior part of the eye. Overall, HP-β-CD-containing CLs are promising candidates for the topical ocular application of TA as an alternative delivery system to intraocular injections.
- Low friction hydrogel with diclofenac eluting ability for dry eye therapeutic contact lensesPublication . Silva, Diana C.; Oliveira, Margarida; Marto-Costa, Carolina; Teixeira, João; Oom, Madalena Salema; Pinto, Carlos A.; Saraiva, Jorge A.; Marques, Ana Clara; Fitzhenry, Laurence; Serro, Ana PaulaWhen placed in the eye, contact lenses (CLs) disturb the tear fluid and affect the natural tribological behaviour of the eye. The disruption in the contact mechanics between the ocular tissues can increase frictional shear stress and ocular dryness, causing discomfort. Ultimately, continuous CLs wear can trigger inflammation which is particularly critical for people suffering from dry eye. In this work, a double strategy was followed to obtain therapeutic daily disposable CLs for dry eye: a hydroxyethyl methacrylate (HEMA) based hydrogel was coated with two natural polysaccharides, chitosan (CHI) and hyaluronic acid (HA) and posteriorly loaded with an anti-inflammatory drug (diclofenac, DCF). Material sterilisation was carried out by high hydrostatic pressure (HHP) combined with moderate temperature. The friction coefficient (μ) was determined in the presence of different tear biomolecules (cholesterol, lysozyme and albumin) using a nanotribometer. Drug release experiments were performed in static and in hydrodynamic conditions. The material was extensively characterised, regarding surface morphology/topography, optical properties, water content and swelling behaviour, wettability, ionic and oxygen permeability and mechanical properties. It was found that the coating did not impair the physico-chemical properties relevant for the material’s application in CLs. Besides, it also ensured a sustained release of DCF for 24 h in tests performed in hydrodynamic conditions that simulate those found in the eye, increasing significantly the amount of drug released. It reduced friction, improving the lubrication ability of the hydrogel, and presented antibacterial properties against S. aureus, P. aeruginosa and B. Cereus. The coated samples did not reveal any signs of cytotoxicity or potential eye irritation. Overall, the coating of the hydrogel may be useful to produce daily CLs able to alleviate dry eye symptoms and the discomfort of CLs wearers.
- Tribomechanical properties of PVA/Nomex® composite hydrogels for articular cartilage repairPublication . Santos, Francisco; Marto-Costa, Carolina; Branco, Ana Catarina; Oliveira, Andreia Sofia; Santos, Rui Galhano dos; Salema-Oom, Madalena; Diaz, Roberto Leonardo; Williams, Sophie; Colaço, Rogério; Figueiredo-Pina, Célio; Serro, Ana PaulaDue to the increasing prevalence of articular cartilage diseases and limitations faced by current therapeutic methodologies, there is an unmet need for new materials to replace damaged cartilage. In this work, poly(vinyl alcohol) (PVA) hydrogels were reinforced with different amounts of Nomex® (known for its high mechanical toughness, flexibility, and resilience) and sterilized by gamma irradiation. Samples were studied concerning morphology, chemical structure, thermal behavior, water content, wettability, mechanical properties, and rheological and tribological behavior. Overall, it was found that the incorporation of aramid nanostructures improved the hydrogel’s mechanical performance, likely due to the reinforcement’s intrinsic strength and hydrogen bonding to PVA chains. Additionally, the sterilization of the materials also led to superior mechanical properties, possibly related to the increased crosslinking density through the hydrogen bonding caused by the irradiation. The water content, wettability, and tribological performance of PVA hydrogels were not compromised by either the reinforcement or the sterilization process. The best-performing composite, containing 1.5% wt. of Nomex®, did not induce cytotoxicity in human chondrocytes. Plugs of this hydrogel were inserted in porcine femoral heads and tested in an anatomical hip simulator. No significant changes were observed in the hydrogel or cartilage, demonstrating the material’s potential to be used in cartilage replacement.