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

Time-lapse images were analyzed using a customized Matlab script (Script S1) developed in our lab based on the Crocker and Grier algorithm and the Matlab version of particle tracking code repository developed by Blair & Dufresne 89, 90 . Based on the size and the threshold intensity value of the fluorescence, the centroid of the nanoparticles were determined in each image. The particle trajectory was estimated by linking the particle locations between frames, and based on a simple random-walk trajectory, the mean square displacement of the particles within a time scale was estimated. The mean square displacement (MSD) was calculated as 〈∆ @ ( )〉 = 〈| ( + ) − ( )| @ 〉, where is the position vector of the particle, and is the lag time. The ensemble average of MSDs (〈〈∆ @ ( )〉〉) of collected individual particles was calculated to average the MSD's over a time lag of 1 sec over multiple particles 91 .