Fig. 4

Coating-dependent behavior of intracellular quantum dots. a Heat maps of diffusion coefficient, D, versus confinement parameter, α. Histograms of D and α are projected on the x and y axes, respectively, and thresholds imposed for mobility are shown as black lines, yielding f_mobile shown in each plot. n = 7, 7, 16, 11, and 18 CHO cells for mPEG, aCOOH, pCOOH, pPEG, and pZW, respectively. b Representative 3D plots of D versus α versus \(B_{{\mathrm{rel}}}^{{\mathrm{max}}}\) for the different quantum dot (QD) coatings in individual cells. The box indicates the same threshold from a, in addition to a \(B_{{\mathrm{rel}}}^{{\mathrm{max}}}\) threshold for delineating populations of single QDs to determine f_1,mobile, shown in the inset of each plot. c Heat map of D versus α for immobilized QDs. d Receiver operating characteristic (ROC) curves distinguishing immobilized QDs from pZW-coated QDs in CHO cells, independently for D (blue) and α (black). Cutoffs that maximize both sensitivity and specificity (D > 0.020 μm² s⁻¹ and α > 0.21) are marked by red circles. e Ensemble average MSD plot for all recorded trajectories fit to Eq. (1) for the first 20 time increments. Calculated D and α values from ensemble and single-trajectory analyses are in Supplementary Table 1. f Heat map of D versus α for simulated trajectories generated using D and α inputs across the indicated ranges to approximate the mPEG-QD distribution. g Heat map of D versus α for simulated trajectories generated using D and α inputs across the indicated ranges to approximate the pZW distribution