Biopolymers valorization using biocompatible ionic liquids for biomedical applications

• Autor(a) principal: Santos, João Pedro Azevedo
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/113755
• topic: Biopolymers; ionic liquids; chitin-glucan complex; topical drug delivery; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

In the last decades, biopolymers received much attention, especially due to its inherent properties, such as biodegradability, biocompatibility and biological properties. However, they showed some limitations in a wide range of applications, mainly in the biomedical field, due to their low solubility in water and in biocompatible organic solvents. To overcome this, ionic liquids (ILs) as low-melting organic salts appeared as an alternative dissolution agent, mainly due to their peculiar properties, which can be tuned according to the adequate selection of the cation and anion. In this context, this thesis aims the development of polymeric structures via biopolymer dissolution using innovative biocompatible ILs. ILs containing pharmaceutically acceptable drugs – namely lidocaine, procaine, and ibuprofen with anaesthetic and anti-inflammatory effects, respectively – were synthesized to enhance the therapeutic properties of the produced biopolymeric structures. This way, the IL will have a double role, it will act as a solvent for the biopolymer dissolution as well as a therapeutic agent, for example for topical delivery of anaesthetic and anti-inflammatory drugs. Different protic ionic liquids, which are ILs that are not fully ionized, have been successfully synthetized by acid-base reactions, using active pharmaceutical drugs as a cation (lidocaine or procaine) combined with carboxylate anions, namely acetate, propionate, hexanoate or ibuprofenate (anti-inflammatory properties). They have been characterized by spectroscopic techniques (1H NMR, FTIR) to assess their structure, thermal analysis (TGA, DSC) to evaluate their thermal stability, and viscosity studies. The prepared ILs have been tested as dissolution agents for different biopolymers, namely chitin-glucan complex (CGC) and chitosan. In general, the prepared ILs containing acetate or propionate anions seemed to be capable to dissolve the CGC biopolymer (1 wt. %). The obtained polymeric structures have been characterized by adequate methods to study their morphology (SEM), composition (FTIR), thermal (TGA, DSC) and mechanical properties depending on their form (films or gels). FTIR studies suggested the obtained films were composed mainly by lidocaine free base and the obtained gel was composed mainly by procaine free base. In general, all prepared polymeric structures showed lower thermal stability than the CGC biopolymer. The obtained gel exhibited a viscous behaviour, whereas films exhibited hydrophilic surface and, poor mechanical properties which limits their potential for application.