In vitro assay for measuring real time topotecan release from liposomes: release kinetics and cellular internalization

Abstract

Topotecan is a drug that is under investigation for the treatment of neuroblastoma and has been encapsulated into liposomes to improve its therapeutic efficacy. However, liposomal formulations still need to be optimized for drug retention and new techniques to measure drug release are required to better understand this process. Here, a novel in vitro method based on fluorescence de-quenching and an automated microscopy imaging platform were developed for monitoring, in real time, the release of topotecan from a liposomal formulation. Drug release from liposomes was monitored for up to 15 h under different conditions including topotecan concentrations, fetal bovine serum amounts (0-20%), and temperatures (25 and 37 °C). A cell-based assay was used to assess liposome association with cells in culture and to quantify amounts of topotecan internalized into cells after release from liposomes. Our results show that the liposomal topotecan concentration had an influence on drug release kinetics: there was a reduction in release rate as a function of increasing concentration. Our data also show that topotecan release from the liposomal formulation was dependent on serum concentration where faster release was observed at higher serum concentrations, and on temperature where faster release was found at 37 °C. This real-time liposomal drug release assay allows for better understanding of the factors important in governing release of topotecan. The assay will be essential towards designing liposomal formulations of topotecan (and potentially of other camptothecin derivatives such as irinotecan) with optimized retention times and better therapeutic efficacy for testing in the clinic.

Theranostic Nanoplatform: Triple-Modal Imaging-Guided Synergistic Cancer Therapy Based on Liposome-Conjugated Mesoporous Silica Nanoparticles

“…We would like to underline that ICG fluorescence intensity of the DOX@GdMSNs-ICG-TSLs + NIR group was the strongest compared to free the ICG + NIR and DOX@GdMSNs-ICG-TSLs group. Combined with flow cytometry data in Figure S5, it demonstrated that DOX@GdMSNs-ICG-TSLs were easier to achieve cell internalization under the assistance of lipid bilayer and NIR irradiation. − …”

Delivery of Rapamycin by Liposomes Synergistically Enhances the Chemotherapy Effect of 5-Fluorouracil on Colorectal Cancer

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Therapeutic Opportunities in Neuroblastoma Using Nanotechnology

“…Topotecan undergoes a pH-dependent, reversible hydrolysis into a nonactive carboxylate at physiologic pH (Devriese et al, 2015). With this in mind, a liposomal topotecan formulation was prepared to protect the cytostatic drug from this pH-induced hydrolysis (Chernov et al, 2017;Gilabert-Oriol et al, 2017). Pharmacokinetic studies showed that the nanoformulation exhibited a 10-fold increase in plasma half-life values in comparison with equivalent doses of topotecan (Hycamtin); however, encapsulated topotecan only modestly increased the life span of NB mice.…”