2D and 3D applications of polymeric biomaterials
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The field of biomaterials has seen huge development over the past decade with enormous efforts invested in discovering materials with improved biocompatibility, application and versatility. Polymers can display many properties that make them ideal biomaterials, such as their potential flexibility, low weight, low cost and biodegradability. Moreover, they can be prepared in a wide variety of compositions and forms and be readily fabricated into various shapes and structures. Polymer microarrays represent an efficient high-throughput platform for the screening and discovery of new materials compared to conventional assays with advantages such as high-density screening, internal consistency of assays and the requirement for only small quantities of material. The first part of this thesis describes work in the area of diabetes research with a focus on how dysfunctional β-cells could be replaced by the transplantation of β-cells obtained from pluripotent stem cells. To achieve this aim, high numbers of β-cells are required. A polymer microarray screening approach was used to identify a number of polymers that promoted the attachment of pancreatic progenitor cells and enhanced cell proliferation. Multiple scale-up fabrication techniques were assessed to establish the most suitable approach and surface for long term cell culture leading to the obtainment of reproducible in situ polymerised polymer layers with enhanced binding properties toward pancreatic progenitor cells. These surfaces have the potential to support cell adhesion and proliferation and could find potential use in the industrial sector to increase the production of pancreatic progenitor cells in vitro. In the second part, efforts were made to gain a better understanding of the maturation of β-cells and their behaviour, with the development of 3D hydrogels based on the previously identified polymers. In this scenario, parameters such as stiffness and porosity were evaluated to identify the best environmental conditions to support 3D cell culturing of pancreatic progenitor cells. Several approaches were tested to generate scaffolds with suitable stiffness and porosity leading to the obtainment of scaffolds based on the previously identified polymer composition and with controlled porosity and stiffness. These scaffolds could represent a suitable environment to allow a better understanding of cell organisation and regulation. In a third avenue of work, arrays of 3D biocompatible materials, which were tailored for varying elasticity, hardness, and porosity (to provide the necessary physical cues to control cellular functions) were fabricated. In this chapter, details of the development of an array of eighty 3D double-network hydrogel features are reported. The array features can be produced as single or double networks and modulated in terms of stiffness, viscoelasticity and porosity to assess cell response to materials with a wide range of properties. The final part of the thesis describes the development and screening of polymeric materials to allow a better understanding of cell–surface interactions with various cell types. To investigate the correlation between cell attachment and the nature of the polymer, a series of random and block copolymers were synthesised and examined for their abilities to attach and support the growth of human cervical cancer cells (HeLa) and human embryonic kidney cells (HEK293T), with attachment modelled on monomer ratios, arrangement, and polymer chain length. The results of this screening showed differences between block copolymers and random copolymers in cell adhesion and provide interesting insight into the improvement of polymer coatings for cell culture.