Reactive Oxygen Species-Biodegradable Gene Carrier for the Targeting Therapy of Breast Cancer.

An ideal gene-carrying vector is supposed to exhibit outstanding gene-condensing capability with positively charged macromolecules to protect the carried gene during in vivo circulation and a rapid dissociation upon microenvironmental stimuli at the aimed sites to release the escorted gene. Currently, it still remains a challenge to develop an ideal gene carrier with efficient transfection ability and low toxicity for clinical applications. Herein, we have innovatively introduced a reactive oxygen species (ROS)-biodegradable boric acid ester linkage in elaborating the design of a gene carrier. In virtue of the featured intracellular characteristics such as the high level of ROS in tumor cells, an ROS-biodegradable electropositive polymer derived from branched polyethylenimine (BPEI) with a low molecular weight (1.2k) through a cross-linking reaction by the boric acid ester bond was developed in this study to achieve condensation and escorting of carried genes. Furthermore, the polymer was modified with substance P (SP) peptide as the targeting ligand through polyethylene glycol. The final fabricated SP-cross-linked BPEI/plasmid DNA nanoparticles exhibit favorable biocompatibility, ROS-cleavability, and fine targeting ability as well as high transfection efficiency compared with parental BPEI both in vitro and in vivo. SP-cross-linked BPEI/small interfering RNA (pololike kinase 1) polyplex possesses favorable gene-silencing effects in vitro and satisfactory antitumor ability in vivo. Hopefully, this novel cross-linked electropositive polymer may serve well as a safe and efficient gene-delivery vehicle in the clinic.