Abstract
Glioblastoma multiforme (GBM) is the most common and highly malignant primary brain tumor. Traditional chemotherapy for treating GBM has limitations such as systemic cytotoxic effects and poor blood-brain barrier (BBB) penetration. When sufficient amounts of chemotherapeutic agents were delivered to the tumor locations, severe systemic cytotoxic effects would be induced, and thus some studies recently focused on enhancing the permeability of BBB by using focused ultrasound (FUS) with microbubbles (MBs) to non-invasively and locally disrupt BBB. Moreover, several drug carriers and drug controlled release methods have been proposed as promising strategies to increase local drug concentrations meanwhile reducing systemic side effects. The aim of this study is to develope a drug-loaded MB formulation (BCNU-MB) with a high loading capacity of 1,3-bis(2-chloroethyl)-1- nitrosourea (BCNU) drug, which was complexed to the lipid shell by both hydrophobic and electrostatic interactions. Note that the BCNU-MBs with FUS contained specific acoustic properties for delivering drug and locally disrupting BBB simultaneously. BCNU-MBs were fabricated via the thin-film hydration method. The BCNU drug encapsulation efficiency was 68.01 ± 4.35 % estimated by an UV-visible spectrometer. Cultured C6 glioma cells implanted in Sprague-Dawley rats were established as tumor model. A 1-MHz FUS with 0.7 MPa pressure, 5% duty factor, and 2 min sonication were used to minimize the intracerebral hemorrhage while maximizing the drug delivery. On day 4 and 5 after the implantation of tumor cells, 0.5 ml BCNU-MBs were delivered intravenously, following the synergistic effect of FUS. BCNU accumulation in the brain and liver were analyzed by high performance liquid chromatography (HPLC) coupled with an UV detector. Tumor volumes were monitored by a series of MR T2-weighted images to follow outcomes of the treatment. Results showed that BBB disruption could be achieved by BCNU-MB with FUS. The HPLC data showed that BCNU-MB delivery system indeed locally release more drugs at FUS-treated hemisphere brains than traditional intravenous chemotherapy drug delivery way. Besides, the BCNU-MB method performed 5-fold less deposition of BCNU in the liver compared to that in traditional chemotherapy, and the MRI images also revealed the significant changes in tumor growth between the two methods. In the study, delivery of drug-loaded MBs and disruption of BBB by FUS in a xenograft rat glioma model can be achieved at the same time. Future works include modifying specific ligands and SPIO particles on BCNU-MBs surface for targeting therapy and as multimodality contrast agents, respectively.