The development of nanomedicine that can be efficiently internalized by drug-resistant cancer cells still presents a daunting challenge due to the low uptake capacity caused by various drug resistance-related factors on the cell membrane. Herein, we engineered the surfaces of glycan nanocarriers with negative, neutral, and gradient positive charges, and discovered that positively charged nanocarriers can be anchored onto the cell membrane through electrostatic attraction and thus be efficiently internalized by drug-resistant cancer cells. In contrast, drug-resistant cancer cells do not readily uptake neutral or negatively charged nanocarriers. By proposing a concentric ring fluorescence coefficient (CRFC), we were able to quantify the cell membrane anchoring capabilities of the nanocarriers and found that positively charged nanocarriers have a much stronger anchoring ability toward drug-resistant cell membranes than their neutral and negatively charged counterparts. Interestingly, with the increase of positive charge, the ability of the nanocarriers to become anchored onto cell membranes was further enhanced, thus confirming that electrostatic attraction plays a crucial role in the membrane-anchoring guided cellular uptake. The method of endowing nano-objects with this charge-attracting capability towards negatively charged cell membranes to drive membrane-anchoring mediated cellular uptake illustrates its potential as a universal strategy for engineering nanocarriers to promote the uptake of nanodrugs into drug-resistant cancer cells and thus improve the therapeutic effect.

Herein we develop a unique differentiated-uptake strategy capable of efficient and high-purity isolation of genuine drug-resistant (DR) cells from three types of drug-surviving cancer cells, which include paclitaxel-surviving human ovarian OVCAR-3 cancer cells and human lung carcinoma A549/Taxol cells, and doxorubicin-surviving human immortalized myelogenous leukemia K562/ADR cells. By using this strategy which relies on fluorescent glycan nanoparticle (FGNP)-based fluorescence-activated cell sorting (FACS) assays, two subpopulations with distinct fluorescences existing in drug-surviving OVCAR-3 cells were separated, and we found that the lower fluorescence (LF) subpopulation consisted of DR cells, while the higher fluorescence (HF) subpopulation was comprised of non-DR cells. Besides, the DR cells and their progenies were found distinct in their increased expression of drug-resistant genes. More intriguingly, by using the FGNP-based FACS assay to detect DR/non-DR phenotypes, we found that the DR phenotype had a potential to differentiate into the non-DR progeny, which demonstrates the differentiation feature of stem-like cancer cells. Further research disclosed that the assay can quantitatively detect the degree of drug resistance in DR cells, as well as the reversal of drug resistance that are tackled by various therapeutic methods. The strategy thus paves the way to develop theranostic approaches associated with chemotherapy-resistance and cancer stemness.