Methotrexate-loaded biodegradable polymeric micelles for lymphoma therapy.

Drug resistance and recurrence are the main clinical challenges in chemotherapy of lymphoma. Methotrexate (MTX), especially high dose MTX (HD MTX), is extensively used to treat some aggressive subtypes of lymphoma, such as Burkitt's lymphoma, in order to overcome drug resistance. But poor solubility of the free drug and severe side effects of HD MTX limit its clinical application. Polymeric micelle, as an ideal nano delivery system, provides effective solutions to these problems. In this work, monomethyl poly (ethylene glycol)-poly (ε-caprolactone) (MPEG-PCL) was employed to load MTX through a one-step solid dispersion method. MTX loaded micelles had a small particle size of 25.64 ± 0.99 nm and polydisperse index (PDI) of 0.176 ± 0.05. Drug loading and encapsulation efficiency of MTX loaded micelles were 5.57 ± 0.14% and 92.46 ± 2.38%. Compared with free MTX, MTX loaded micelles demonstrated a much slower and sustained release behavior in vitro. MTT assay and cell apoptosis study suggested that MTX loaded micelles were more effective in inhibiting proliferation and inducing apoptosis on Raji lymphoma cells than MTX injection, which was especially distinct in high dose groups. Cellular uptake study indicated that MPEG-PCL micelle had a 1.5 times higher uptake rate in Raji cells. As for in vivo studies, MTX loaded micelles were more competent to suppress tumor growth and prolong survival time than MTX injection in the subcutaneous Raji lymphoma model. Notably, the high dose group of micelle formulation exhibited the strongest anti-tumor effect without additional toxicity. Furthermore, immunofluorescent and immunohistochemical studies showed that tumors of MPEG-PCL-MTX treated mice had more apoptotic cells and fewer proliferative cells. In conclusion, MPEG-PCL-MTX micelle is an excellent intravenously injectable formulation of MTX with both good solubility and enhanced anti-tumor activity, which perfectly meets clinical demands, especially for administration of HD MTX.