| Abstract—Background and Objective: Augmentation of local drug delivery from targeted nanoparticles (NP) with nondestructive, noncavitational clinical ultrasound (US) offers the potential to enhance therapeutic efficacy in diseases such as cancer while limiting adverse systemic side effects. This lab has demonstrated augmentation of drug delivery from avb3-targeted perfluorocarbon NP and US in cancer cells in vitro (Crowder et al, 2005). The present study investigates the utility of conventional, clinical US for augmentation of drug delivery in vivo in a transgenic mouse cancer model (K14-HPV16) that develops squamous cell carcinomas. Methods: 16 mice were injected intravenously with either avb3-integrin targeted or nontargeted NPs complexed with 0.1 mol% fluorescent dye rhodamine. At 30 min post-injection, one ear was treated for 30 min with a commercial US imager (Philips iE33) in Color Doppler mode at MI=1.4 and at 2.3 MHz (other ear served as control). Mice were sacrificed at 2 hrs post-injection and ear sections visualized by fluorescence microscopy. After setting exposure time & color thresholds, the area of rhodamine signal was calculated using MicroSuite 5 software (Olympus, PA). The effect of US in enhancing therapeutic benefit of drug bearing NP was examined in mice treated with targeted NPs loaded with the cytolytic amphipathic peptide melittin, which is a principal component of bee venom with antitumor activity (13 mg/kg, 7 doses over 3 weeks). BRDU stains of proliferating cells were used as an index of antitumor effect. Results: US-exposed ears exhibited a 5.2 (±1.9 SE) fold rhodamine augmentation as compared to non-exposed ears in the avb3-targeted group (n=9, p<0.05, Wilcoxon signed-rank test) and a 4.0 (±1.3) fold augmentation in the nontargeted group (n=7, p<0.01), indicating a marked effect of material deposition induced by US. In the US therapy trial, ears of transgenic mice exposed to US+NPs show reduced proliferating keratinocytes compared to controls (see Fig) pointing to accelerated reversal of disease progression. Conclusion: Noncavitational US can significantly augment drug-delivery in vivo from molecularly targeted therapeutic NP. This readily available and clinically-benign approach offers possibility for additional measures of tumor targeting with exogenous US energy that improves therapeutic efficacy. |