Flow cytometry assays on assessing the specificity of affibody ZHER2:342 and nanoparticles modified with affibody, PLGA* ZHER2:342. (a) Cells were labeled with Trastuzumab-FITC and ZHER2:342-FITC and analyzed in BL1 channel (excitation laser 488 nm, emission filter 530/30 nm). Autofluorescence is shown by grey, cells labeled with Trastuzumab-FITC are shown by blue, with ZHER2:342-FITC are shown by red. (b) Flow cytometry assay: evaluation of PLGA*ZHER2:342 nanoparticles bound to cells. Flow cytometry histograms were acquired in the YL2 channel (excitation laser 561 nm, emission filter 615/20 nm). Autofluorescence is shown by green, cells labeled with PLGA*ZHER2:342 nanoparticles are shown by red. (c) Median fluorescence intensities of cells’ populations labeled with PLGA*ZHER2:342 in the corresponding fluorescent channel of the flow cytometer. ** p < 0.001.