Uptake and cytotoxicity of poly(d,l-lactide-co-glycolide) nanoparticles in human colon adenocarcinoma cells

The main objectives of the present study were to evaluate the cytotoxicity and the mechanisms of uptake of biodegradable lactic acid–glycolic acid copolymer (PLGA) nanoparticle carrier systems in vitro using the human colon adenocarcinoma cell line Caco2. Nanoparticles (NPs) (PLGA 75:25) with an average diameter of 299.5 nm containing bovine serum albumin labeled with fluorescein isothiocyanate (BSA-FITC) as a fluorescent model protein marker were formulated by the double emulsion technique. Various parameters influencing the internalization process by Caco2 cells including concentration of NPs, duration of contact time and cell culture conditions were studied. After overnight exposure of NPs to cells at 37 °C, the cell uptake capacity varied in accord with NP concentration, over the 25–800 μg/ml concentration range tested. Maximal uptake of nanoparticles at 37 °C occurred at 4 h and was inhibited significantly at 4 °C. The extent of NPs internalization was evaluated by confocal laser scanning microscopy. Potential NP toxicity evaluated by modified MTS and lactate dehydrogenase (LDH) colorimetric cytotoxicity tests, measuring mitochondrial activity and membrane integrity respectively, showed that cell viability is significantly reduced at PLGA nanoparticle concentrations greater than 700 μg/ml after 24 and 48 h respectively. The results obtained in vitro for BSA-FITC loaded PLGA nanoparticles underline their potential as carriers for peptide delivery and their utility for the study of NP cell transport and trafficking mechanisms.