Multi-layered nanogels with MMP-sheddable PEG masks: Preparation and promotion of tumor cell uptake by controlling surface characteristics.

•Multi-layered nanogels (MLNGs) with matrix-metalloproteinase (MMP) sensitivity were developed for targeted intracellular delivery.•PEG was introduced onto nanogels to be shed in a tumor microenvironment.•MLNGs showed enhanced uptake in tumor cells.•PEG layers both with and without an MMP-peptide shielded the cytotoxicity of MLNGs.