Introduction: Gold nanoparticles (AuNPs) possess several features that make them well suited for applications in medicine. AuNPs functionalized with cancer targeting peptides can be applied in the diagnosis and/or treatment of cancer. We investigated the application of two cancer targeting peptides, namely p.L and p.14 to produce AuNPs that can specifically bind to colon carcinoma cells.
Methods: Citrate capped AuNPs (cAuNPs) of 14 nm in size were synthesized and coated with PEG-OH and PEG-biotin to produce PEG-AuNPs. Streptavidin tagged p.L and p.14 peptides were conjugated to PEG-AuNP using the biotin moiety on PEG-biotin to facilitate the conjugation. UV-Vis spectroscopy, TEM, FTIR spectroscopy and the zetasizer measurements were used to characterize the physico-chemical properties of the AuNPs. The cytotoxicity of the AuNPs was evaluated on human colon carcinoma (Caco-2, HT-29), human breast carcinoma (MCF-7) and non-cancerous human fibroblast cells (KMST-6). The cells were treated with increasing concentrations (1 – 4nM) of the cAuNP, PEG-AuNP, and peptide conjugated PEG-AuNP (p.L-AuNPs and p.14-AuNPs) after which cell viability was assessed using the MTT assay. The cellular uptake of AuNPs was confirmed using ICP-MS.
Results: The AuNPs displayed a typical surface plasmon resonance (SPR) band of 520 nm. TEM micrographs demonstrated relatively spherically shaped and reasonably monodispersed AuNPs. PEG-AuNPs and peptide-AuNPs showed a red shift in SPR band, size and charge. cAuNPs were highly toxic even at the lowest concentration (1nM) tested. PEGylated AuNPs were less toxic with more than 80% of the cells still viable. The cytotoxicity assay also revealed reduced Caco-2 viability at 4nM for p.L-AuNPs. Similarly, p.14-AuNPs showed reduced HT-29 and Caco-2 viability (below 80%) at 3 and 4nM. No cytotoxicity was observed for MCF-7 and KMST-6 cell lines.
Conclusion: This study provides more information on the successful conjugation of peptides to AuNPs using streptavidin-biotin chemistry, and also gives preliminary information on the toxicity of the synthesized-AuNPs in vitro. This study warrants further investigation into the cellular uptake and localization of p.L-AuNP and p.14-AuNP in the colon carcinoma cell lines.
Keywords: Gold nanoparticles; Colon cancer; Toxicity;Polyethylene glycol;Peptides
Targeted drug delivery and nanocarriers , Nanomedicine for cancer diagnosis & therapy , Toxicology and risk assessment of nanomedicine systems
