An injectable and tumor-specific responsive hydrogel with tissue-adhesive and nanomedicine-releasing abilities for precise locoregional chemotherapy.

Locoregional chemotherapy, especially using implantable hydrogel depots to sustainably deliver chemotherapeutics at tumor site, has shown great potential for improving antitumor efficacy and reducing systemic toxicity. However, the hydrogel applications are limited by some intrinsic constraints, especially the contradiction between increasing drug penetration and accumulation in tumor and decreasing random drug diffusion into surrounding normal tissues. Herein, we report a unique "Jekyll and Hyde" nanoparticle-hydrogel (NP-gel) hybrid platform, which can keep dormant in adjacent normal tissues but be activated by mildly acidic and hyaluronidase-rich microenvironment in malignant tumor tissues to unidirectionally release tumor-targeting and penetrative doxorubicin (DOX)-loaded NPs. Apart from tumor-specific recognition, penetration, internalization and release, NP-gel features: shear-thinning behavior for injection, tissue-adhesiveness for continuous on-site activation, and full biodegradability for safe use. Precise delivery was clearly demonstrated in both tumor-grafted and tumor-resected mice. A single peritumoral injection of DOX-loaded NP-gel exhibited a significantly higher drug accumulation in tumor for 3 weeks than in nontarget organs and thus long-term tumor remission. More importantly, significant inhibition in tumor recurrence without detectable toxicity to healthy organs was demonstrated when applied after tumor resection. The designed system displayed long-acting and precise anticancer efficacy, paving the way toward effective tumor locoregional treatment. STATEMENT OF SIGNIFICANCE: Injectable hydrogels, allowing sustained drug delivery directly at tumor site, has shown great potential for locoregional chemotherapy. However, how to achieve tumor-specific drug accumulation but meanwhile impede the random drug diffusion into surrounding normal tissues remains an insurmountable challenge, especially considering high drug concentration gradient, higher interstitial fluid pressure and denser extracellular matrix in tumor than adjacent normal tissue. Herein, a 'Jekyll and Hyde' nanoparticle-hydrogel hybrid formulation was designed to keep dormant in adjacent normal tissues but be activated by mildly acidic and hyaluronidase-rich microenvironment in malignant tumor tissues to unidirectionally release tumor-targeting and penetrative DOX-loaded nanoparticles, leading to a significant tumor inhibition and antirecurrence efficiency without detectable toxicity to healthy organs, thus presenting great potential for precise locoregional chemotherapy.