A comparison of photophysical characteristics of rHDL encapsulated anti-cancer drug valrubicin and free valrubicin.

Nanotechnology as a channel for drug delivery is one of the rapidly developing fields in cancer therapeutics. Targeted drug delivery has the advantage of having minimal interaction with healthy tissue, thereby reducing the toxicity of the drug to the rest of the body. rHDL nanoparticles have been found to be an efficient delivery system for highly lipophilic anti-cancer drugs. This is achieved through the interaction of scavenger receptors class B type I (SR-BI), which are highly expressed on cancer cells interact with rHDL nanoparticles for effective drug delivery to the cancer cell and tumor. The drug under investigation is Valrubicin, which, apart from being an effective anti-cancer drug, also has intrinsic fluorescence. This allowed for the comparison of photophysical properties of free Valrubicin and rHDL Valrubicin via steady state and time resolved fluorescence measurements. The steady-state anisotropy of rHDL Valrubicin is higher as compared to free Valrubicin, suggesting its encapsulation in rHDL nanoparticles. A longer rotational correlation time was observed for rHDL Valrubicin in time resolved anisotropy measurements compared to free Valrubicin, further supporting steady state anisotropy data.. We also studied the cellular internalization of free Valrubicin and rHDL Valrubicin using confocal microscopy. This could help track the movement of rHDL nanoparticles within the cancer cells.