Target and acidic tumor microenvironment-induced in situ HCR for bispecific tumor cell imaging and therapy

Abstract

The tumor microenvironment is characterized by an acidic extracellular milieu generated through the anaerobic glycolysis of tumor cells. Leveraging this characteristic, we suggest employing an in situ hybridization chain reaction (HCR) activated by both target recognition and the acidic microenvironment for bispecific tumor cell imaging and therapy. By integrating the recognition capability of aptamers, the pH responsiveness of i-motifs, and the signal amplification of HCR, we have developed a pH-induced HCR (pH-HCR) system. This system consists of three DNA probes: pH-Apt, HP1, and HP2. pH-Apt is composed of the Apt-T-B and Imotif sequences (sequences that can form an i-motif structure). Apt-T-B includes two segments: an aptamer sequence for MUC1 recognition and a trigger sequence blocked by the Imotif sequence for HCR. Under acidic conditions, upon binding to MUC1, the Imotif sequence forms an i-motif structure, detaching from pH-Apt and exposing the trigger sequence. This initiation of HCR, in conjunction with HP1 and HP2, amplifies fluorescent signals, achieving the bispecific imaging of tumor cells. Simultaneously, doxorubicin (Dox) can be loaded onto probes and released under acidic conditions, resulting in a 47% cytotoxic efficiency against tumor cells. pH-HCR enables successful bispecific imaging and cell killing induced by MUC1 in the acidic microenvironment of SW620 cells.