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  • Publication
    Design and Characterisation of Degradable Polymeric Microstructures
    (University College Dublin. School of Chemistry, 2022) ;
    This thesis reports the design and controlled degradation of polymeric materials. In particular, polycaprolactone-containing microstructures are the main focus. Direct laser writing (DLW) through two-photon polymerisation (2PP) was employed to fabricate solid polymeric templates quickly and accurately from liquid precursors on the micron scale. The use of these templates for successful replica moulding of a dynamical array of microscale pillars using polycaprolactone dimethacrylate (PCL-DMA) is discussed. Initially, the purity of purchased PCL-DMA was a concern. Upon its characterisation, it was realised that the polymer contained a considerable level of impurities. From here, the PCL-DMA was then synthesised in yields of 75 - 86 %. The phase of the purified product then required further blending with 1,6-hexanediol diacrylate (HDDA) to reach the liquid phase to achieve successful feature replica moulding of 2PP templates. Two blends consisting of 1:9 PCL-DMA:HDDA and 1:4 PCL-DMA:HDDA (all containing 1 % photoinitiator w/w) were produced along with neat HDDA (all including 1 % photoinitiator w/w). These formulations were used to fabricate degradable microstructures from 2PP printed templates. The two PCL-containing blends and neat HDDA were replica moulded to produce a small library of materials with controllably degradable surface microstructures in a reproducible manner. The abbreviation ‘UCD’ was incorporated into the polymeric microstructures by the intelligent design of the 2PP template. As such, this logo was degraded in a controlled manner over time upon exposure to an alkaline environment. The degradation was then monitored via mass loss calculations and imaging techniques, including atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). These polymeric materials were then tested to establish their cytotoxicity against mammalian cell lines, in particular, NTERA-2 and HeLa cells. After establishing the biocompatibility of these materials towards these cells, the viability to load silica particles was investigated for their potential use in applications concerning drug loading and delivery. Early pilot release studies describe the swelling ratio and mesh size calculations of cured gels fabricated from polyethylene glycol diacrylate (PEG-DA) and water. It was demonstrated that depending on the molecular weight of PEG-DA and the concentration of water used in the mixture, the swelling ratio and mesh size was considerably impacted. The mesh sizes of these gels were related to biologics, where preliminary Bradford assay release studies of lysozyme were conducted.