Browsing by Author "Verwey, Lehani"

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    Hydrogels based on poly(styrene-co-maleic anhydride) for the application of reversible male contraceptive
    (2016-03) Verwey, Lehani; Klumperman, Bert; Pfukwa, Rueben; Stellenbosch University. Faculty of Engineering. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: The use of a polymeric gel as male contraceptive, injected into the vas deferens of the male, has attracted a considerable amount of interest due to improved criteria over the current available options. The non-invasive character of these gels offer reduced side effects and improved reversibility over a vasectomy, rendering a promising new alternative to satisfy society’s ever increasing demand for an ideal contraceptive. This thesis focuses on the design, synthesis and characterisation of a polymer hydrogel system with improved biocompatibility and reversibility properties for contraception purposes in the male. Poly(styrene-co-maleic anhydride) (SMA), a biocompatible, commercially available copolymer that easily undergoes chemical modification through its highly reactive maleic anhydride residues is a candidate system for use in these hydrogel matrices. RAFT (reversible addition fragmentation chain transfer) mediated polymerisation was utilised for the synthesis of well-defined SMA, followed by two post-polymerisation modification approaches. The first, prepared through modification of the anhydride residues in the SMA backbone and the alternative, through chain end modification of the thiocarbonyl thio group of the RAFT-made SMA. Preference was given to the first approach during the present study, as side-reactions turned out to hamper the disulphide formation of thiol terminal-SMA. Water-soluble boronic acid functionalised polymers (SMI-BA) were prepared by partial modification of the reactive maleic anhydride residues in SMA with 3-aminophenylboronic acid (BA). SMI-BA was combined with poly(vinyl alcohol) (PVA) to prepare the required hydrogels. Gelation is achieved within minutes after mixing of aqueous solutions of SMI-BA and PVA, based on reversible ester crosslink formation between the boronic acid groups in SMI-BA and the 1,3 diols in PVA. The structural properties of the gels were characterized by oscillatory rheometry as a function of composition and degree of modification (SMI-BA). Adequate gelation times of approximately 1-5 minutes (37 C, PBS, pH = 7.4), with storage moduli (G’) of 12 kPa – 50 kPa were obtained. Rapid reversibility of the gels is achieved within a few minutes by the addition of glucose in combination with sodium bicarbonate (NaHCO3). The results indicate that the polymeric hydrogel is a promising candidate for further investigation as an injectable gel for male contraception purposes.