Tumor microenvironment targeting with dual stimuli-responsive nanoparticles based on small heat shock proteins for antitumor drug delivery

Tumour microenvironment (TME)-targeting nanoparticles (NPs) were developed based on Methanococcus jannaschii small heat shock proteins (Mj-sHSPs). Transactivator of transcription (TAT) were modified on the surface of Mj-sHSPs (T-HSPs) to enhance their cellular internalization ability (CIA), and a pH/enzyme dual sensitive PEG/N-(2-aminoethyl)piperidine-hyaluronic acid (PAHA) coat was combined with T-HSPs (PT-HSPs). PT-HSP NPs exhibited multi-layered morphologies and good stability against plasma protein adsorption. The release of paclitaxel (PTX) from PT-HSP NPs was negligible at physiological pH. Under conditions similar to the TME (acidic pH and overexpressed hyaluronidase (HAase)), the PAHA coat deshielded from PT-HSP NPs because of two factors: charge reversal and HAase degradation. Once the PAHA coat was shed, the size of the NPs decreased; its surface charge became positive; and remarkable drug release was triggered. Cellular experiments indicated that the CIA of PT-HSPs was shielded in the microenvironment of normal cells and recovered in that of tumour cells. In vivo imaging exhibited that the PT-HSP NPs had an impressive tumour targeting ability compared with the uncoated controls. The antitumor efficacy in vivo demonstrated that tumour-bearing mice treated with PTX-loaded PT-HSP NPs achieved better anti-tumour effects and safety than the Taxol formulation. In summary, this study provided Mj-sHSP NPs with coats that could be shed in response to the particular pH and enzymes in the TME, which improved the efficacy of tumour therapy. This study reports on tumor microenvironment-targeting protein-based nanoparticles (PT-HSP NPs) for targeted tumor therapy. The NPs had a multilayered structure: a protein cage, a TAT cationic layer, and a dual-sensitive coat. PT-HSP NPs exhibited multilayered morphology, with good stability against plasma protein adsorption, and PTX release negligible at physiological pH. Under the tumor microenvironment (acidic pH and overexpressed HAase), PAHA coat deshielded from PT-HSP NPs due to two factors: the charge reversal induced by protonation of piperidines in PAHA and HAase degradation. The results of cellular uptake, cytotoxicity, in vivo imaging, and tumor inhibition experiments confirmed that PT-HSP NPs exhibited promising tumor targeting efficacy in vitro and in vivo.