Tissue-penetrating, hypoxia-responsive echogenic polymersomes for drug delivery to solid tumors.

Hypoxia in solid tumors facilitates the progression of the disease, develops resistance to chemo and radiotherapy, and contributes to relapse. Due to the lack of tumor penetration, most of the reported drug carriers are unable to reach the hypoxic niches of the solid tumors. We have developed tissue-penetrating, hypoxia-responsive echogenic polymersomes to deliver anticancer drugs to solid tumors. The polymersomes are composed of a hypoxia-responsive azobenzene conjugated and a tissue penetrating peptide functionalized polylactic acid-polyethylene glycol polymer. The drug-encapsulated, hypoxia-responsive polymersomes substantially decreased the viability of pancreatic cancer cells in spheroidal cultures. Under normoxic conditions, polymersomes were echogenic at diagnostic ultrasound frequencies but lose the echogenicity under hypoxia. In-vivo imaging studies with xenograft mouse model further confirmed the ability of the polymersomes to target, penetrate, and deliver the encapsulated contents in hypoxic pancreatic tumor tissues.