In-Vitro Delivery Of Blm Into Resistant Cancer Cell Line Using Sonoporation With Low-Boiling Point Phase Change Ultrasound Contrast Agents

Bleomycin (BLM) is a potent chemotherapeutic that causes cytotoxic oxidative damage to DNA. However, this non-permeant drug is mainly internalized via receptor-mediated endocytosis. Therefore, tumors showing poor expression of BLM-binding proteins are resistant to this therapy. This work aims to improve the intracellular accumulation and efficacy of BLM in resistant colorectal adenocarcinoma cells (HT-29) through sonoporation with low-boiling point phase change contrast agents (PCCAs). At 37 degrees C, octafluoropropane PCCAs can be converted into microbubbles (MBs) at or above a peak negative pressure (PNP) of 300 kPa. Here, PCCAs were added to a suspension of HT-29 cells at a ratio of 5.6 PCCAs: 1 cell in a plastic cuvette. This suspension was maintained at 37 degrees C and stimulated with ultrasound (1.0 MHz, 400 kPa PNP, 40% duty cycle). Cell viability was assessed at BLM concentrations ranging from 0.01 - 10 mu M using a MTT assay 48 hours post-sonoporation. Furthermore, drug delivery efficacy was compared using PCCAs and standard lipid-shelled MBs as sonoporation mediators. As expected, results show that BLM alone had no effect on the viability of resistant colon cancer cells at any of the tested concentrations. However, a significant and dose-dependent decrease in cell viability was observed when BLM was delivered to the cells via PCCA- or MB-mediated sonoporation. Our in-vitro results suggest that PCCAs are as effective (i.e., 47% cell death with 10 mu M BLM) as regular MBs for sonoporation. Additionally, no significant cell death was observed when cells were exposed to the sonoporation procedure in the absence of BLM.