Abstract Lippia javanica and Lippia scaberrima are used as herbal remedies and are commercially traded as health teas in southern Africa under the brands “Mosukujane” and “Musukudu”, respectively. This study evaluates the relationship between the presence of phenolic compounds and the antioxidant activities of infusions prepared from four Lippia species (L. javanica, L. scaberrima, L. rehmannii and L. wilmsii) indigenous to South Africa. The antioxidant activities of the infusions, determined by the 2,2-diphenylpycrylhydrazyl (DPPH) method, were also compared to those of popular black, green and herbal tea brands. Of the four indigenous species, infusions of L. javanica and L. wilmsii exhibited the highest antioxidant activities (EC50: 358 and 525 μg/ml, respectively) and contained the most phenolic compounds (14.8 and 14.5 mg/ml of dry weight gallic acid equivalent, respectively). Antibacterial activities of methanolic extracts of the four Lippia species were determined against four human pathogens (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa). The extract of L. javanica was the most active against all the pathogens tested. Those Lippia species (L. javanica and L. wilmsii) previously reported to produce higher levels of the pharmacologically active phenylethanoid glycosides verbascoside and isoverbascoside, portrayed stronger antioxidant and antibacterial activities. This study gives credence to the use of infusions of these Lippia species for their general health benefits.

No description available.

No description available.

Considering the infection and second trauma caused by dressing changes, development of antibacterial and low-adherent wound dressings is urgently needed. Silver ion is a widely used antimicrobial agent, but its cytotoxicity remains a problem. In this study, low-adherent PAM (polyacrylamide) hydrogel incorporated with less toxic AgNP (silver nanoparticle), was immobilized onto PET (poly(ethylene terephthalate)) substrates by an IPN (interpenetrating polymer network) method. The modified PET is effectively antibacterial and the surface is significantly less adherent than untreated PET. However, silver-resistant bacteria become a potential problem. Thus, ionic 5,5-dimethylhydantoin (DMH) analogues containing either a quaternary ammonium moiety or a phosphonate functional group were designed and synthesized. The DMH analogues were converted to antibacterial N-chloramine counterparts through chlorination to serve as potential alternatives to AgNP. The N-chloramine with a structural cation exhibited distinctly enhanced antibacterial functions both in solution and after immobilization on fabrics.

Considering the infection and second trauma caused by dressing changes, development of antibacterial and low-adherent wound dressings is urgently needed. Silver ion is a widely used antimicrobial agent, but its cytotoxicity remains a problem. In this study, low-adherent PAM (polyacrylamide) hydrogel incorporated with less toxic AgNP (silver nanoparticle), was immobilized onto PET (poly(ethylene terephthalate)) substrates by an IPN (interpenetrating polymer network) method. The modified PET is effectively antibacterial and the surface is significantly less adherent than untreated PET. However, silver-resistant bacteria become a potential problem. Thus, ionic 5,5-dimethylhydantoin (DMH) analogues containing either a quaternary ammonium moiety or a phosphonate functional group were designed and synthesized. The DMH analogues were converted to antibacterial N-chloramine counterparts through chlorination to serve as potential alternatives to AgNP. The N-chloramine with a structural cation exhibited distinctly enhanced antibacterial functions both in solution and after immobilization on fabrics.

No description available.

Hospital-acquired infections are a significant contributor to clinically-related morbidity and mortality. The majority of these infections are associated with the use of invasive medical devices, where urinary catheters account for ~36% of cases. Current preventative strategies have shown short-term (<7 days) success, however their long-term (>28 days) efficacy is unclear. This thesis explores the use of solution-cast polyurethane nanocomposite (PUNC) materials for antimicrobial drug delivery in urinary applications. It is hypothesised that the enhanced barrier properties of PUNCs, afforded by the incorporation of well-dispersed nanoinclusions, would allow for the sustained release of an antimicrobial agent. The objectives of this research were to investigate the antibacterial, mechanical and barrier properties of PUNCs incorporating various silicates modified using antimicrobials, hypothesised to also act as dispersing agents. Organically modified silicates (OMS) were prepared at 110%, 200% and 300% cationic exchange capacity (CEC) using the biocide, chlorhexidine diacetate (CHX), which was hypothesised to perform the dual functions; dispersant and antibacterial agent. Resulting OMS were incorporated at 1wt% and 5wt% loadings into a PU matrix to produce PUNCs; PEU-CHX1.1MMT, PEU-CHX2.0MMT, and PEU-CHX3.0MMT, respectively. CHX performed well as a dispersant, producing intercalated to partially exfoliated PUNCS. Antibacterial activity was dependent on OMS type and loading. PEU-CHX1.1MMT materials had poor antibacterial properties, but the addition of free CHX into the materials significantly improved their efficacy, demonstrating long-term sterility in an in vitro urinary tract (UT) model. PEU-CHX2.0MMT and PEU-CHX3.0MMT at 5wt% OMS loadings had partially exfoliated structures and excellent antibacterial activity. Cytotoxicity was evident in all materials, although to a lesser extent in the latter. Overall, intermediate OMS loadings of CHX2.0MMT would be expected to produce PUNCs with favourable antibacterial activity and cytocompatibility. PUNC drug-release profiles demonstrated sustained release compared to pristine PU, indicative of enhanced barrier properties. Their ultimate tensile properties decreased with increased OMS loading or addition of free CHX.Higher cationic-exchanged OMS caused significant reductions in strain. Young's modulus increased in response to higher %CEC OMS and loading. PUNCs show promise as antibacterial biomaterials for long-term urinary applications, where antimicrobial release and mechanical properties can be modulated through organic modification and OMS loading.

Thesis (M.S.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 92-105).

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 129-146).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.