Novel Self assembled nanoparticles for Tumor targeted delivery of Zoledronic acid.

Purpose. To design and develop novel self assembled nanoparticles (NPs) for the delivery of zoledronic acid (ZOL) in cancer therapy. Methods. NPs were prepared by two different methods. Briefly, a solution of CaCl2 and Na2HPO4 were mixed under stirring and the resulting dispersion was filtered trough 0.22 m pore filters. The dispersion was mixed with an aqueous solution of ZOL, resulting in ZOL-containing Ca2+/PO43- NPs (CaPZ NPs). In the following step, the CaPZ NPs were incubated under strirring with PEGylated cationic liposomes at room temperature for 10 min (pre-PLCaP NPs). Alternatively, CaPZ NPs were mixed with cationic liposomes and the resulting particles were then incubated with micelles of PEGylated lipid at 50°C for 10 min (post- PLCaP NPs). All formulations were characterised in terms of morphology, mean diameter, polydispersity index, zeta potential and ZOL actual loading. of NPs. The in vitro activity of PLCaPZ NPs were investigated on different cell lines. Cell proliferation studies in presence of ZOL was investigated by MTT assay. Results. The technological characterization of NPs underlined significant differences between pre-PLCaPZ and post-PLCaPZ NPs. In particular, pre-PLCaPZ and post-PLCaPZ NPs had mean diameters of about 147 and 309 nm, respectively. Moreover, in the case of pre-PLCaP NPs, a very narrow size distribution was observed. Morphological analysis showed that the post-PLCaP preparation consisted in an heterogeneous particle dispersion, reasonably due to the coexistence of micelles and NPs. On the contrary, spherical-shaped and homogenously dispersed NPs were found in the case of pre-PLCaPZ. HPLC analyis of non-complexed ZOL showed an actual loading of 65 and 0.09 g of ZOL/mg lipid for post-PLCaP and pre-PLCaP, respectively. In all cell lines, the NPs strengthened the growth inhibition induced by free ZOL, reaching a potentiation factor of 12 in breast carcinoma MCF7 cell line. Conclusions. New ZOL-containing NPs were successfully developed in our lab. In particular, the formulation termed as pre-PLCaPZ consists in NPs with a narrow size distribution and high ZOL encapsulation and can be easily prepared directly before use. In vitro studies showed that the antiproliferative activity of ZOL is strongly improved by using pre-PLCaPZ. The results obtained indicate that pre-PLCaPZ NPs could be a new and powerful tool to deliver ZOL in vivo.