In Situ Monitoring of MicroRNA Replacement Efficacy and Accurate Imaging‐Guided Cancer Therapy through Light‐Up Inter‐Polyelectrolyte Nanocomplexes

Replacement of downregulated tumor‐suppressive microRNA (Ts‐miRNA) is recognized as an alternative approach for tumor gene therapy. However, in situ monitoring of miRNA replacement efficacy in a real‐time manner via noninvasive imaging is continually challenging. Here, glutathione (GSH)‐activated light‐up peptide‐polysaccharide‐inter‐polyelectrolyte nanocomplexes are established through self‐assembly of carboxymethyl dextran with disulfide‐bridged (“S—S”) oligoarginine peptide (S‐Arg(4)), in which microRNA‐34a (miR‐34a) and indocyanine green (ICG) are simultaneously embedded and the nanocomplexes are subsequently stabilized by intermolecular cross‐linking. Upon confinement within the robust nanocomplexes, the near‐infrared fluorescence (NIRF) of ICG is considerably quenched (“off”) due to the aggregation‐caused quenching effect. However, after intracellular delivery, the disulfide bond in S‐Arg(4) can be cleaved by intracellular GSH, which leads to the dissociation of nanocomplexes and triggers the simultaneous release of miR‐34a and ICG. The NIRF of ICG is concomitantly activated through dequenching of the aggregated ICG. Very interestingly, a good correlation between time‐dependent increase in NIRF intensity and miR‐34a replacement efficacy is found in nanocomplexes‐treated tumor cells and tumor tissues through either intratumoral or intravenous injections. Systemic nanocomplexes‐mediated miR‐34a replacement significantly suppresses the growth of HepG‐2‐ and MDA‐MB‐231‐derived tumor xenografts, and provides a pronounced survival benefit in these animal models.