Electronic Theses and Dissertations (Masters)

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Browsing Electronic Theses and Dissertations (Masters) by Keyword "Bioactive peptides"

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    Synthesis and characterization of novel short antimicrobial peptides with wound healing properties
    (University of the Witwatersrand, Johannesburg, 2019) Machumele, Khanani Peggy; Makatini, Maya Mellisa
    In recent years, there has been an increasing health crisis due to multidrug-resistant microbes. These pathogens are strains of bacteria that have become resistant to antibiotic drugs. In the year 2016, the World Health Organisation (WHO) had appealed to the members of states in the USA to create a priority list of other bacteria that are resistant to antibiotics in order to support research and development of effective drugs. According to literature, antimicrobial peptides have the potential to be potent agents against pathogens that have multidrug-resistant properties. Despite these studies, there are still substantial limitations (toxicity and susceptibility to proteases) that have affected their clinical and commercial development. In this study, the focus was on bacteria that infect wounds. The lack of potent chronic wound treatment has resulted in an enormous financial and physical burden on patients and the health care system. The stress of multi-resistant microbes heighten the challenges plagued on a patient due to untreatable infected wounds. Peptides which are able to kill bacteria and promote the wound healing process would greatly benefit patients. For example, patients with diabetic foot ulcers are prone to chronic wounds because of their condition, which may lead to amputation. Wound healing antimicrobial peptides are able to kill bacteria in the wound and induce the formation of collagen which will result in fewer amputations. The aim of this proposed research is to develop novel wound healing and antimicrobial compounds by derivatizing bioactive peptides into selective and protease-stable peptidomimetics. Tigerinin RC1 is an antimicrobial peptide with wound healing properties. It was chosen as a starting point for the design of analogues with drug-like properties and it was also conjugated to silver nanoparticle (AgNPs) to improve its bactericidal activity. In this study, 16 Tigerinin RC1 peptide analogues were successfully synthesized using the solid phase peptide synthesis strategy. Peptides were purified using the semi prep-HPLC however, the desired purity of > 90% was only achieved after two or more purification runs. Thus only 4 of the peptide analogues had a purity great than 90% which were KM-PEP-carb, KM-PEP-cyc-amide, KM-PEP-ada and KM-PEP-CT. These peptides were tested for antimicrobial activity and KM-PEP-cyc-amide peptide showed promising results with the minimum inhibitory concentration of 128 μg/ml against P. aeruginosa. Cytotoxicity studies also revealed that conjugation of KM-PEP-carb to AgNPs improved cytotoxicity because when 25 μg/ml of KM-PEP-carb was tested against human T cells the cell viability was -1.48% and when conjugated to AgNPs the cell viability increased to 35.17.