Anticancer Activity from Gold-alpha-Lactalbumin Nanoconstructs?

Human alpha-Lactalbumin made lethal to tumor cells (HAMLET), and its bovine analogue BAMLET, have in the recent years shown promising results in cancer therapy. HAMLET contains several oleic acids which in turn stabilize a partially unfolded conformational state of the protein, inducing a higher surface activity compared to the native protein, and likely play a role in its cancer-detrimental function as well. Herein, we report the formation of gold-bovine alpha-lactalbumin nanoconstructs (Au-LA NCs) displaying conformational changes in the native protein and its concomitant ability to reduce He La cell viability approaching that of BAMLET. Modification of LA with gold was achieved via two synthesis protocols; (i) utilizing the intrinsic reduction potential of LA (Au-LAint) or (ii) the addition of an extrinsic reducing agent (Au-LAext). The gold-protein nanostructures formed were investigated using a palette of analytical probes including AFM, TEM, zeta-potential, UV-vis, circular dichroism, and fluorescence (steady-state and time-resolved). Toxicity toward He La cells was studied using a trypan blue assay and benchmarked against BAMLET. Whereas constructs from both synthetic protocols employed result in conformational changes of the protein and altered surface activity compared to the native protein, Au-LAint was found to display lipid-specific interaction and severe disruption of lipid monolayers. Au-LAint also revealed toxicity toward He La-cells comparable to that of BAMLET. The results imply that formation of Au-LA nanoconstructs could be a new route to making HAMLET-like materials, while also imparting a built-in optical probe from fluorescent or plasmonic gold species.