Development of a receptor targeted nanotherapy using a proapoptotic peptide
Sibuyi, Nicole Remaliah Samantha
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The prevalence of obesity amongst South Africans is alarming, with more than 29% of men and 56% of women considered to be obese. Angiogenesis, a process for development of new blood vessels play a major role in growth and survival of the adipose tissues. Pharmacological inhibitors of angiogenesis are therefore a sensible strategy to reduce excess body weight. Current anti-obesity drugs have limitations because of their lack of selectivity and specificity, which lead to undesirable side effects and reduced drug efficacy. Future anti-obesity therapeutic strategies should be target-specific, with minimal toxicity towards healthy tissues will be more appropriate for obesity treatment. Targeted nano-therapeutic agents are currently being developed to overcome the drawbacks associated with conventional drug therapies. The nano-based delivery vehicles that specifically target diseased cells are appealing as they could reduce drug toxicity towards healthy tissues and be more effective at lower dosages. The main aim of this study was to develop a receptor-mediated nanotherapy that specifically targets the white adipose tissue vasculature and trigger the death of these cells through apoptosis. The 14 nm gold nanoparticles (AuNPs) were synthesized using theTurkevich method following reduction of gold aurate by sodium citrate salt. Different chemistries were used to functionalise the AuNPs for biological application by conjugating with either vascular targeting peptide or pro-apoptotic peptide on their surface or both. The nanomaterials were characterised by UV-Vis, Zeta potential and transmission electron microscopy (TEM). The sensitivity and specificity of various AuNP conjugates were tested in vitro on colon and breast cancer cell lines. A human (Caco-2) cell line that expresses the receptor for the adipose homing peptide was chosen as an in vitro model system. Cellular toxicity and uptake of the nanoparticles was evaluated using the WST-1 assay, Inductively Coupled Plasma-Optical Emission Spectra (ICP-OES) and TEM. The induction of apoptosis following exposure to the nanoparticles was examined by Western blot and flow cytometric analysis. The anti-proliferative activity of the targeted therapeutic nanoparticles on the cells was more pronounced on the cells expressing the receptor for the adipose homing peptide. The uptake of unfunctionalised AuNPs was higher compared to functionalised nanoparticles, but this did not impair cell viability. The activity of the therapeutic peptide was retained and enhanced following conjugation to AuNPs as shown by Western blot and flow cytometric analysis. The nanotherapy under study demonstrated receptor mediated targeting, and enhanced activity on the cells expressing the receptor. However, the therapeutic and efficacy of the targeted nanotherapy still need to be tested in animal models of obesity to confirm the treatment specificity.