99mTc-vinorelbine tartrate loaded spherulites: Lung disposition study in Sprague-Dawley rats by gamma scintigraphy

Vinorelbine Tartrate (VLB) is the first line chemotherapeutic agent for treatment of Non-Small Cell Lung Cancer, whose non-specific distribution causes unwanted side effects. The aim of the present investigation was to formulate VLB loaded spherulites intended for targeting the lung. Spherulites were composed of Soyabean Phosphatidylcholine (SPC), Cholesterol (Chol), Potassium oleate and Mannitol. Lipid film prepared using SPC, Chol and Potassium oleate, was dispersed in aqueous phase comprising Mannitol and VLB, followed by controlled shearing and extrusion. PEGylated Spherulites were prepared by incorporating 1,2-distearoyl-sn-glycero-3 phosphatidylethanolamine-N-[methoxy poly (ethylene glycol)] (DSPE-PEG 2000) in the lipid phase. Vesicles were characterized for size, entrapment efficiency and drug release. In vitro cell cytotoxicity and apoptosis study were performed on A549 cell line. Radiolabeling of VLB was performed by direct labeling with reduced technetium-99m. Binding affinity of 99mTc- labelled complexes was assessed by diethylenetriaminepenta acetic acid (DTPA) challenge test. Biodistribution study was done in Sprague Dawley rats. Dynamic light scattering and Transmission electron micrographs confirmed that PEGylated and non-PEGylated Spherulites were discrete, spherical and exhibited the size range of 120-130 nm. Non-PEGylated and PEGylated Spherulites had an entrapment efficiency of 95.65% and 94.2% respectively. In vitro drug release study indicated VLB plain drug solution diffused completely within 24 h, however, Non-PEGylated and PEGylated Spherulites showed similar release pattern till 48 h. Results of cell line study showed that cells treated with VLB loaded Spherulites showed more cytotoxicity and underwent high degree of apoptosis at lower concentration compared to the VLB solution. Radiolabeled complex was stable in saline and serum, further, DTPA challenge study ensured the high binding strength. Gamma Scintigraphy displayed that PEGylated Spherulites were localized within lungs at higher concentration than non-PEGylated followed by plain drug.