Synthesis of electro-responsive nanocomposites for neural tissue engineering

• Autor(a) principal: Nascimento, Luís Filipe Miranda do
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10773/35687
• topic: Vertically aligned carbon nanotubes; Neural stem cells; Spinal cord injury; Polydimethilsiloxane; Hydrogels; Gelatin; Alginate; Electrical conductivity; Neuritogenesis

Spinal cord injury (SCI) is an extremely serious condition which leads to a drastic decrease on patient mobility. Neural tissue engineering (NTE) has been trying to promote solutions by combining different materials such as polymers, cells, and specific architectures to assist regeneration of the injured tissue. This work objective is the conceptualization and manufacture of a multilayer multifunctional nanocomposite and study its cytocompatibility with neural stem cells (NSCs) envisioning NTE application. For that, vertically aligned carbon nanotubes (VACNTs) were grown by thermal chemical vapor deposition onto a silica substrate (SiO₂). Then, as-grown VACNTs were transferred onto polydimethylsiloxane (PDMS) creating a VACNT-PDMS layer with a stable interface, maintaining CNT alignment, confirmed by scanning electron microscopy. By transferring VACNTs onto this PDMS layer, flexibility and handling of the nanocomposite was obtained eliminating some problems presented by native VACNTs when coupled with their native substrate which is rigid. However, the nanocomposite VACNT/PDMS is inert and requires a component that mimics the neural microenvironment. So, a third polymeric layer was needed. To integrate this layer. VACNT and PDMS underwent a series of surface treatments (i.e., ultraviolet coupled with ozone (UV/O3) and oxygen (O₂) plasma) leading to changes on wettability and surface energy assessed indirectly by water contact angle (WCA) and attenuated-total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify chemical changes post treatments. O₂ plasma treatment led to most significative change in wettability with the introduction of silanol (Si-OH) groups on PDMS and carboxylic (COOH) groups on CNTs. For the third layer two strategies were employed. The first (S1) relied on the creation of a hydrogel composed of gelatin and alginate methacrylamide (GelMA and AlgMA) capable of photo- and -ionic crosslink. The hydrogel showed to support NSC proliferation and viability, however, when transferred to the VACNT-PDMS layer the hydrogel would delaminate. The alternative solution (S2) consisted in the crosslink of gelatin and alginate induced by 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide coupled with N-hydroxysuccinimide on top of a previously silanized VACNT-PDMS layer. This was a successful approach creating a nanocomposite capable of sustaining adhesion and proliferation of NSCs. Furthermore, with immunocytochemical staining it was possible to observe neuronal differentiation. The results obtained demonstrated that the conceptualized multilayer multifunctional nanocomposite favors proliferation and differentiation of NSCs, making it an electro-responsive platform and a candidate to be electrically stimulated for neural tissue engineering.