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Title: Enzyme-responsive supramolecular assemblies for controlled release
Author: Caponi, Pier Francesco
ISNI:       0000 0004 2744 1359
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2012
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The use of "smart materials" is increasing due to the variety of stimuli to which the materials can be tailored to respond. In particular, enzyme responsive materials are of great interest for drug delivery applications due to the high biocompatibility and numerous advantages offered by enzymes. The number of publications in this area shows the increasing interest of the scientific community towards possible applications of enzyme responsive materials. In this thesis a new approach towards drug delivery is documented and explored through the synthesis and the study of self assembly behaviour of a new class of enzyme responsive polymers. Through an innovative, yet straight forward, one step-synthetic approach, we functionalised poly(2-isopropyl-2-oxazoline), a thermally responsive polymer, with enzyme substrates attached to fluorenylmethyloxy carbonyl moieties, creating the first example of temperature/phosphatase responsive polymer. The interactions developed after enzyme catalysis not only led to self assembly, but also affected the dimensions of the colloidal aggregates formed below and above the phase transition temperature of the polymer. Moreover, due to the presence of fluorenyl groups we were able to study the self assembly behaviour of the functionalised polymers gaining insight on the self assembly mechanisms. To have a deeper understanding of the self assembly mechanism and the role that interactions, e.g. π-π, hydrophobic, ionic, play during the process, a small library of amino acid functionalised polymers was synthesized. The polymers contained in the library were studied both singularly and as mixed populations. Through the study of self assembly behaviour of single populations, we found that ionic interactions have an important role in disrupting the formation of aggregates and, as expected, the presence of planar/hydrophobic groups facilitates it. By mixing two polymer populations, we were able to create multicomponent systems that would vary their sizes depending on enzyme catalysis/temperature and the amino acids forming the nanostructures. Moreover, the aggregates formed by two populations are still enzyme accessible, i.e. the enzyme can access the core of the particles and trigger dis-assembly, which is particularly important for applications in the drug delivery field. Finally, to prove the versatility of peptidic based materials, we exploited the self assembly properties of fluorenylmethoxycarbonyl-dipeptides to create hydrogels that can actively trap pheromones, often volatile and sensible substances, to afford a controllable and tuneable release over time. The peptide used for the study was chosen due to its capacity to self-assembly into micelles before enzymatic catalysis and form hydrogels after dephosphorylation. The tailored design allowed us not only to achieve controlled release, but also to improve the handling and storing process of volatile pheromones. Thanks to the number of variables that could be modified to create different systems with particular characteristics, e.g. different peptide-based hydrogels, peptide concentration, this innovative method shows potential to find application as a pest control/crop protecting agent in the agricultural industry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available