Tumour cell delivery of antisense oligonuclceotides by human serum albumin nanoparticles.

Nanoparticles consisting of human serum albumin (HSA) and containing different antisense oligonucleotides (ASO) were prepared by desolvation. The preparation process was optimised regarding the amount of desolvating agent, stabilisation conditions as well as nanoparticle purification. The glutaraldehyde crosslinking procedure of the particle matrix was identified as a crucial parameter for biodegradability and drug release of the nanoparticles. The influence of chain length and backbone modification of ASOs on the drug loading efficiency was investigated. The loading increased with longer chain length and employment of a phosphorothioate backbone. The resulting nanoparticles were tested in cell cultures for cytotoxicity and cellular uptake. In different tumour cell lines no cytotoxic effect was observed up to nanoparticle concentrations of 5000 microg/ml. All cell lines showed a significant cellular uptake of HSA nanoparticles. The entrapment of a fluorescent labelled oligonucleotide within the particle matrix was used for the detection of the intracellular drug release of the carrier systems. Confocal laser scanning microscopy revealed that nanoparticles crosslinked with low amounts of glutaraldehyde, rapidly degraded intracellularly, leading to a significant accumulation of the ASO in cytosolic compartments of the tumour cells.