Gradient nanofibers for dermal regeneration of hard-to-heal ulcers

• Autor(a) principal: Coelho, David José Caetano
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36010
• topic: Hard-to-heal ulcers; Chitosan; Nanofibers; Scaffold; Solution blow spinning; Platelet lysate; Tannic acid

Hard-to-heal ulcers are serious life-threatening chronical conditions, impairing skin and mucosa full regeneration and opening the door to debris or severe infections. The cost of treatment also puts national health systems across the globe under pressure. Several products aiming at skin wound healing exist on the market, giving the surgeon different options to choose from when tackling this condition, but there is still the need to develop better solutions in treating different clinical cases, not to mention aesthetical results. Chitosan, originated from the outer skeleton of shrimp and shellfish, is a natural polymer that has been extensively described in the literature, with applications in tissue engineering, drug delivery or vaccine immunogenicity. Being biocompatible and with low toxicity, several biomedical devices have been tested, including nanoparticles, biofilms or nanofibers. Among them, nanofibers reveal an extraordinary similarity to the collagen fibers comprising extracellular matrix, a network that confers nutrient and mechanical support to embedding cells and promotes the formation of new tissue, vital when pursuing skin regeneration. Chitosan fibers can be fabricated by spinning processes, including the widely reported Electrospinning, taking use of electrical fields, or Solution Blow Spinning (SBS), which uses instead heat and solvent evaporation to produce fibers. In the present work, chitosan was spun by SBS to produce scaffolds that can be used in skin wound healing. Due to chitosan chemical nature, spinning with a co-polymer – Polyethylene Oxide (PEO) - was required. The first goal was to develop a three-layered scaffold with different weight ratios of Chitosan and PEO, and a neutralization step in a basic solution revealed promising in extracting PEO. The layer with the highest chitosan content from the scaffold was further functionalized with bioactive molecules, tannic acid and growth factor cocktail-Platelet Lysate, to grant enhanced biological properties. Infrared spectroscopy and Scanning Electron Microscopy revealed the successful interaction between chitosan and the mentioned molecules, with stress-strain testing assuming crucial to analyse variations in mechanical properties. Lastly, the fabricated fibers were subjected to preliminary in vitro testing with Normal Human Dermal Fibroblasts, showing their attachment and proliferation, on what can be seen as a promising step to further characterize the single layered and three-layered scaffolds.