Methotrexate (MTX) is the single most effective agent for the treatment of primary central nervous system
lymphoma. Currently, the delivery of MTX to the brain is achieved by high systemic doses, which cause severe long-term neurotoxicity, or intrathecal administration, which is highly invasive and may lead to
infections or hemorrhagic complications. Acoustically active
microbubbles have been developed as
drug carriers for the noninvasive and brain-targeted delivery of
therapeutics. However, their application is limited by their low
drug-loading capacity. To overcome this limitation, we prepared
microbubbles coupled to MTX-loaded
liposomes using ZHIFUXIAN, a novel type of
microbubbles with a superior safety profile and long circulation time. MTX-
liposome-coupled
microbubbles had a high
drug-loading capacity of 8.91%± 0.86%, and their size (2.64 ± 0.93 μm in diameter) was suitable for
intravenous injection. When used with ultrasound, they showed more potent in vitro cytotoxicity against Walker-256
cancer cells than MTX alone or MTX-loaded
liposomes. When Sprague-Dawley rats were exposed to sonication, administration of these MTX-
liposome-coupled
microbubbles via the tail vein led to targeted disruption of the blood-brain barrier without noticeable tissue or capillary damage. High-performance liquid chromatography analysis of the brain MTX concentration showed that MTX delivery to the brain followed the order of MTX-
liposome-coupled
microbubbles + ultrasound (25.3 ± 2.4 μg/g) > unmodified ZHIFUXIAN + MTX + ultrasound (18.6 ± 2.2 μg/g) > MTX alone (6.97 ± 0.75 μg/g) > MTX-
liposome-coupled
microbubbles (2.92 ± 0.39 μg/g). Therefore, treatment with MTX-
liposome-coupled
microbubbles and ultrasound resulted in a significantly higher brain MTX concentration than all other treatments (P<0.01). These results suggest that MTX-
liposome-coupled
microbubbles may hold great promise as new and effective
therapies for primary central nervous system
lymphoma and other central nervous system
malignancies.