Identification of peptide coatings that enhance diffusive transport of nanoparticles through the tumor microenvironment

Rashmi Mohanty; Xinquan Liu; Jae You Kim; Xiujuan Peng; Sahil Bhandari; Jasmim Leal; Dhivya Arasappan; Dennis C. Wylie; Tony Dong; Debadyuti Ghosh

Building on our in vitro studies, we next validated that our selected clone P4-phage improved transport and uptake in tumors compared to the negative control-phage. We measured and quantified ex vivo uptake of our peptide-presenting phage in ECM-rich BxPC3 pancreatic tumor xenografts 79 as described by Bajpayee et al. 80 . Briefly, the BxPC3 tumor tissue slices were preequilibrated in PBS with protease inhibitor and incubated with in a bath of sample, P4 or control-phage. We calculated the clone uptake ratio in the tissue by quantifying the amount of phage in the tissue to the amount in the incubation bath over several days. The average uptake of selected clone P4-phage dramatically increased from 1.67×10 3 ±2.08×10 3 after 1 day to 1.34×10 8 ±2.31×10 8 after 5 days of the incubation, whereas the tumor uptake of the negative control-phage only increased from 1.12×10 3 ±4.94×10 2 in 1 day to 7.27×10 5 ±1.32×10 5 in 5 days ( Figure 5) . Consequently, the uptake ratio of P4-phage is 200 times higher than that of the negative control-phage after five days of incubation with the ex vivo tumor tissue. At initial timepoints, the rate of uptake is similar for both clones, but at later timepoints, there is a larger concentration gradient for our selected clone. This gradient allows continued diffusion and further transport of the P4-phage into the tumor tissue than observed with the control-phage. The difference in concentration gradients resulting in improved tissue uptake has been observed in cartilage explants [80] [81] [82] and mucus hydrogels 63 .