Topotecan-loaded thermosensitive nanocargo for tumor therapy: In vitro and in vivo analyses

This study demonstrates the development of topotecan (TCN) loaded thermosensitive nanocargos (TCN-TS-NC) for intramuscular (IM) administration with enhanced antitumor activity. In this regards, TCN loaded temperature dependent solid lipid nanoparticles (SLNs) were prepared with micro-emulsion method, which were then incorporated into temperature sensitive poloxamer solution to develop TCN-TS-NC. The particle size, entrapment efficiency (%EE), zeta potential and transmission electron microscopy (TEM) analysis of the TCN-TS-NC were performed. Moreover, the inject-ability, release pattern, apoptosis, cellular uptake, pharmacokinetics and antitumor studies of the TCN-TS-NC were attained and compared with TCN solution and TCN-Emulgel (poloxamer solution containing TCN). At room temperature, the TCN loaded SLNs were solid and poloxamer solution remains liquid, however, TCN loaded SLNs melted to liquid and Emulgel converted into gel from, at body temperature, resulting controlled release of the incorporated drug. The TCN-TS-NC showed enhanced cellular uptake and better apoptosis. Similarly, it reduces C_max and sustained its level for a significantly longer time in rats, as compared to the TCN-Emulgel and TCN solution. Moreover, a significantly improved antitumor activity was observed in TCN-TS-NC treated tumor bearing athymic nude mice when compared with the control, TCN solution and TCN-Emulgel applied mice. Thus, the TCN-TS-NC system showed control release of the drug with no initial fast effect. Furthermore, it enhanced the antitumor activity of TCN with comparatively no toxicity. It is therefore concluded that TCN-TS-NC could be a potentially more suitable drug delivery system for the delivery of TCN.