Cytotoxic Evaluation of Irinotecan-loaded PLGA-PEG-retinoic acid Nanomicelles on HT-29 Cancer Cell Line

In the present study PLGA-PEG and PLGA-PEG-retinoic acid (RA) which had already been synthesized in our laboratory were used to prepare targeted (PLGA-PEG-RA) and non-targeted (PLGA-PEG) polymeric micelles by thin-film... [ view full abstract ]

In the present study PLGA-PEG and PLGA-PEG-retinoic acid (RA) which had already been synthesized in our laboratory were used to prepare targeted (PLGA-PEG-RA) and non-targeted (PLGA-PEG) polymeric micelles by thin-film hydration method to target irinotecan to colorectal cancer cell (HT-29). Cytotoxic effect of irinotecan solution, non-targeted irinotecan-loaded nanomicelles, targeted irinotecan-loaded nanomicelles, and blank nanomicelles were evaluated on HT-29 cell line using MTT assay. Untreated cells were taken as the negative control and the blank culture medium was used as the control. Cells were grown in RPMI 1640 medium and incubated with samples for 72 h at the equivalent irinotecan concentrations of 1 to 8 µg/ml. Cell viability for each sample was then calculated. Blank micelles did not show any measurable toxicity on HT-29 cell line indicating the safety of PLGA-PEG-RA as a potential drug carrier for irinotecan to the tumor cells. Toxicity of irinotecan and irinotecan-loaded nanomicelles were significantly increased in a drug concentration dependent manner. Non-targeted irinotecan-loaded nanomicelles showed greater cytotoxicity than free irinotecan while the cell toxicity of targeted irinotecan-loaded nanomicelles was significantly greater than both free irinotecan and non-targeted irinotecan-loaded nanomicelles. IC50 values of drug-loaded PLGA-PEG and drug-loaded PLGA-PEG-RA nanomicelles were significantly lower than those of the free drug. Irinotecan-loaded targeted nanomicelles exhibited lowest IC50 values as compared to free irinotecan and non-targeted nanomicelles. More cytotoxicity of non-targeted nanomicelles compared to free drug might be due to the presence of PEG on the surface of nanomicelles forming a brush-like shell that stretches away from the core reducing micelle aggregations and increasing cellular uptake. Drug-loaded PLGA-PEG-RA nanomicelles indicated highest toxicity compared to non-targeted nanomicelles which could be attributed to the receptor-mediated endocytosis and the nucleus-directed drug targeting of the nanoparticles. Our results indicate that the RA-conjugated nanomicelles could have great potential for targeted therapy of irinotecan, may reduce irinotecan therapeutic dose and consequently reduces adverse effects of this drug.