Ultrasound-mediated gene delivery by using folic acid-modified cationic microbubbles

Glioblastoma multiforme (GBM) is a malignant brain tumor with poor prognosis and high recurrence rate despite traditional chemotherapy. Ultrasound-targeted microbubbles destruction (UTMD) has been approved to achieve local blood-brain barrier disruption (BBBD), enhancing therapeutic agents into the brain. Besides, UTMD has been employed to deliver tumor-killing gene for cancer therapy. Recently, folate receptor (FR), a small molecule with no immunogenicity protein, has been found to be overexpressed in GBM which benefits tumor-specific targeting therapy. Based on the natural high affinity of FR, folate microbubbles (MBs) could effectively conjugate around FR overexpressing tumor. In this study, we fabricated folate-targeted cationic MBs (FCMBs) for improving gene delivery by loading DNA on MBs shell and actively attaching on cancer cell. By the trigger of focus ultrasound (FUS) (center frequency = 1 MHz; pulse length = 10 ms; burst rate = 5 Hz; duty cycle = 5%; acoustic pressure = 0.28-0.7 MPa; exposure time, 60 sec), 1 × 10⁸ pGFP loaded-FCMBs were added in C6 glioma cells. Gene expression and cell viability were assessed using cell counting assay and alarma blue assay, respectively. Results confirmed that FCMBs enable to load DNA via electrostatic interaction on MBs shell and target gene delivery on cancer. Moreover, the gene transfection of FCMBs in C6 glioma cells was significantly higher than MBs without folate and cationic lipid under FUS exposure. In addition, increasing acoustic pressure and inertial cavitation could improve gene delivery by enhancing permeability of cell membrane.