PREPARAÇÃO E CARACTERIZAÇÃO DE NOVOS MATERIAIS BIODEGRADÁVEIS DE BASE POLIÁCIDO LÁCTICO

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Photocurable bioadhesive based on lactic acid

Publication . Marques, Dina; Santos, João; Ferreira, Paula; Correia, Tiago R.; Correia, Ilídio Joaquim Sobreira; Gil, Maria; Baptista, Cristina Maria dos Santos Gaudêncio

Novel 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.

2016-01-01Journal article

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Synthesis, functionalization and characterization of UV-curable lactic acid based oligomers to be used as surgical adhesives

Publication . Santos, João; Marques, Dina; Alves, Patrícia; Correia, Tiago R.; Correia, Ilídio Joaquim Sobreira; Baptista, Cristina Maria dos Santos Gaudêncio; Ferreira, Paula

The synthesis, functionalization and characterization of low molecular weight L-lactic acid based oligomers to be used as new UV-curable bioadhesives are presented herein. Prepolymers hydroxyl terminated were produced by L-lactic acid dehydration with 1,4-butanediol. The prepolymer was further modified with photoreactive sites by adding an isocyanate-functional unsaturated acrylic ester, which was used for the first time in the biomedical field (LAROMER® LR 9000). Films were afterwards produced upon UV irradiation for 120 s, using a biocompatible photoinitiator (Irgacure® 2959), and finally characterized. The synthesized films exhibited a moderate swelling ratio, suitable for the envisioned application. DSC analysis confirmed an increase in Tg values after each synthesis step. Nevertheless, the film Tg remains lower than the physiological and room temperature. TGA confirmed an improved stability of films at high temperatures. The in vitro degradation tests showed their susceptibility to hydrolysis at 37 °C, suitable for short-term uses. Preliminary evaluation of the adhesion capacity suggested that the synthesized material may be effective in sustaining wound closure and repair. The surface energy was also measured and its value was lower than the ones from blood or skin which supports the previous statement. Blood compatibility studies, cell viability assays (using human dermal fibroblasts) and bacterial inhibition tests (using two bacteria models) were performed. The results indicated that cured adhesive is bio/haemocompatible and possesses antimicrobial activity. Altogether, characterization results showed that the produced material presented a set of properties suitable for biomedical applications, particularly as a surgical adhesive.

2015-07-21Journal article

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Engineering star-shaped lactic acid oligomers to develop novel functional adhesives

Publication . Santos, João; Travassos, Diana Rita Sousa; Ferreira, Paula; Marques, Dina; Gil, Maria; Miguel, Sónia; Ribeiro, MP.; Correia, Ilídio Joaquim Sobreira; Baptista, Cristina

Direct 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.

2018Journal article

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Functionalization and photocuring of an L-lactic acid macromer for biomedical applications

Publication . Marques, Dina; Santos, João; Ferreira, Paula; Correia, Tiago R.; Correia, Ilídio Joaquim Sobreira; Gil, Maria; Baptista, Cristina Maria dos Santos Gaudêncio

L-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.

2016-04-07Journal article

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