Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695990
Title: End group functionalised highly branched poly(N-isopropylacrylamides) in biomaterials
Author: Plenderleith, Richard
ISNI:       0000 0004 5992 0100
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2015
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Abstract:
In these projects highly branched poly(N-isopropylacrylamide) (HB-PNIPAM) have been functionalised with peptides or bioactive molecules to control cell behaviour using polymers in solution and immobilised within crosslinked membranes. A set of HB-PNIPAM polymers have been synthesised, with varying feed ratios of NIPAM to 4-vinylbenzyl pyrrolecarbodithioate (4-VBPCD). This had a significant effect on the degree of branching, and influenced properties of the polymers such as, the number of acid ends per unit mass, the number of pyrrole ends per unit mass, molecular weight distributions and the lower critical solution temperature (LCST). These properties were thoroughly investigated by nuclear magnetic resonance (NMR), solution cell differential scanning calorimetry (VPDSC), gel permeation chromatography (GPC), ultra violet (UV) spectroscopy and fluorescence spectroscopy. The bimodal distributions of the molecular weights for these polymers were analysed using the traditional means but also by an alternative method, which should only be used for non-Gaussian distributions. This alternative method was based on the median and quartiles of the distribution and thus takes into account the whole distribution. Evidence for a core shell morphology of the polymer particles has been elucidated by using a fluorescent dye dissolved within the polymer core. The highly branched polymers have been functionalised with cell adhesive peptide sequences and used to lift cells from tissue culture plastic before redepositing them into new cell culture wells. This is made possible by affecting the availability of the cell adhesive peptide for cell binding via the LCST of the polymer. These polymers were not as efficient as Trypsin when transferring cells. However, a non-enzymatic method for passaging cells may by favourable for sensitive cell types. Branched semi-Interpenetrating polymer networks (BS-IPNs) have been synthesised from the peptide functional HB-PNIPAM polymers and polymer matrices based on PEG and PVP. Changing the concentration of the HB-PNIPAM-GRGDS has been shown to influence the adhesion and proliferation of cells in culture. It is suggested that the improvement in adhesion and proliferation of cultured cells on these materials could lead to the development of biomaterials with improved biological properties. The materials have been fabricated by microstereolithography to produce tube type structures. These could be used in the area of peripheral nerve repair. However, these materials could be suitable for a range of other biomaterials. A biodegradeable monomer system, based on PTMC, has been developed. Testing has shown the relationship between the molecular weight of the prepolymers used and the mechanical properties of the resulting crosslinked polymer. BS-IPNs were formed with the added HB-PNIPAM-GRGDS additive. This was shown to have a positive effect on the behaviour of cells cultured in vitro. The HB-PNIPAM polymers have been end functionalised with the antibiotic vancomycin and the solvatochromic dye Nile Blue. This produced a molecule which could bind to bacteria. It was hoped that the binding of the bacteria would trigger the coil to globule transition which would give rise to a colour change from the Nile Blue. However, the position of the dye on the polymer chain end meant that this colour change was not observed as the environment of the dye does not change upon coil collapse.
Supervisor: Rimmer, Stephen Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.695990  DOI: Not available
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