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.

中文翻译：

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靶点和酸性肿瘤微环境诱导的原位 HCR 用于双特异性肿瘤细胞成像和治疗

肿瘤微环境的特征是肿瘤细胞无氧糖酵解产生的酸性细胞外环境。利用这一特性，我们建议采用由靶标识别和酸性微环境激活的原位杂交链式反应（HCR）进行双特异性肿瘤细胞成像和治疗。通过整合适体的识别能力、i-motifs的pH响应性和HCR的信号放大能力，我们开发了pH诱导的HCR（pH-HCR）系统。该系统由三个 DNA 探针组成：pH-Apt、HP1 和 HP2。 pH-Apt由Apt-TB和Imotif序列（可以形成i-motif结构的序列）组成。 Apt-TB 包括两个片段：用于 MUC1 识别的适体序列和用于 HCR 的被 Imotif 序列阻断的触发序列。在酸性条件下，与 MUC1 结合后，Imotif 序列形成 i-motif 结构，与 pH-Apt 分离并暴露触发序列。 HCR 的启动与 HP1 和 HP2 结合，放大荧光信号，实现肿瘤细胞的双特异性成像。同时，阿霉素 (Dox) 可以负载到探针上并在酸性条件下释放，从而对肿瘤细胞产生 47% 的细胞毒效率。 pH-HCR 能够在 SW620 细胞的酸性微环境中成功实现双特异性成像和 MUC1 诱导的细胞杀伤。