Selective Intracellular Delivery of Antibodies in Cancer Cells with Nanocarriers Sensing Endo/Lysosomal Enzymatic Activity

The differential enzymatic activity in the endo/lysosomes of particular cells could trigger targeted endosomal escape functions, enabling selective intracellular protein delivery. However, this strategy may be jeopardized due to protein degradation during endosomal trafficking. Herein, using custom made fluorescent probes to assess the endosomal activity of cathepsin B (CTSB) and protein degradation, we found that certain cancer cells with hyperacidified endosomes grant a spatiotemporal window where CTSB activity surpass protein digestion. This inspired the engineering of antibody‐loaded polymeric nanocarriers having CTSB‐activatable endosomal escape ability. The nanocarriers selectively escaped from the endo/lysosomes in the cells with high endosomal CTSB activity and delivered active antibodies to intracellular targets. This study provides a viable strategy for cell‐specific protein delivery using stimuli‐responsive nanocarriers with controlled endosomal escape. Endo/lysosomal cathepsin B activity differentiates among cell types and serves as a stimulus to trigger cell‐specific endosomal escape. By designing nanocarriers armed with cathepsin B‐activatable endosomal escape function, endosomal escape can be controlled to only occur in targeted cancer cells with upregulated endo/lysosomal cathepsin B activity. This innovative approach offers a new means to achieve targeted intracellular protein delivery.