a, General scheme for biotinylation of glycopolypeptides with sulfo-NHS biotin. Biotinylation reactions were performed in 1× PBS at room temperature overnight. b, Biotin–LYTAC-mediated NA-647 uptake is continuous over time in K562 cells. K562 cells were incubated at 37 °C in complete growth medium with 500 nM NA-647 or 500 nM NA-647 and 2 μM poly(M6Pn)short for the indicated time, then washed and analysed by live-cell flow cytometry. The MFI (mean fluorescence intensity) was measured relative to background fluorescence from untreated K562 cells. c, d, Biotinylated poly(M6Pn) LYTACs direct NA-647 to lysosomes in K562 cells (c) and Jurkat cells (d). Cells were incubated with PBS, 500 nM NA-647, or 500 nM NA-647 and 2 μM biotinylated poly(M6Pn)short for 0.5–1 h in complete growth medium. NA-647 (red) colocalized with acidic endosomes and lysosomes as labelled with LysoTracker Green (turquoise). Scale bar, 20 μm. Fluorescence intensity is normalized in the NA-647 channel for all images. For c, d, data are representative of two independent experiments. For b, data are mean ± s.d. of three independent experiments.