Cascade Drug Delivery through Tumor Barriers of Pancreatic Cancer via Ultrasound in Combination with Functional Microbubbles

The abundant desmoplastic stroma and the lack of sufficient targets on pancreatic cancer cells render poor drug penetration and cellular uptake, which significantly compromise the chemotherapy efficacy. Herein, we reported a three-step cascade delivery strategy for selective delivery of paclitaxel (PTX) to achieve a targeted therapy for pancreatic cancer. cRGD and cCLT1 peptides, which could target the integrin and fibronectin, respectively, overexpressed in pancreatic cancer cells and stroma, were decorated on PTX-loaded microbubbles, resulting in the formation of dual-targeting PTX-RCMBs. In this strategy, ultrasound in combination with PTX-RCMBs first enhanced the permeability of tumor vessels via cavitation effects and simultaneously helped the generated PTX-RCNPs penetrate into the stroma. Then, the cCLT1 peptide modified on PTX-RCNPs selectively bound the fibronectin highly expressed in the stroma and later targeted the integrin (α5β1) on the cell surface. Finally, another targeting cRGD peptide modified on PTX-RCNPs would further promote PTX uptake via targeting the integrin (αvβ3) on the cell surface. This strategy significantly increased the delivery of PTX into tumor tissues. Moreover, the in vivo effective accumulation of PTX was monitored by ultrasound and fluorescence bimodal imaging. The tumor growth inhibition was investigated on subcutaneous tumor mouse models with 89.8% growth inhibition rate during 21 days of treatment, showing great potential for improving pancreatic cancer therapy.