摘要： Fluorescent probes with small size, low toxic and specific recognition are of fundamental interests as well as of practical prospects in bioimaging. Though various probes have been reported up to now, including traditional organic dye, quantum dots, rare earth-based particles, and recently emerged carbon dots, silicon dots, polymer dots and metal cluster et al., the relatively large size and lack of specify are far from satisfaction in cellular imaging. As confirmed in previous reports, the large size might influence the functions of target, where the consequent drawback of non-specific is requiring conjugate with additional ligands which brings even larger size and complex procedures. In such a context, fluorescent metal nanoclusters have rapidly attracted widely concern for their integrated advantages of small size, high stability, unique selectivity and tunable properties by simply selecting different stabilizer. In considering a wide variety of stabilizer, aptamer, as a class of ssDNA, has received particular interest because of the easy production, reduced size comparing with antibody and selectively binding ability in molecule level with specific structures. Former researches have proved that cytosine has strong interaction with Ag cations. Therefore, colorful Ag clusters (AgNCs) have been continuously prepared using different DNA sequences in a simple reductive reaction after mixing both aptamer and Ag cation. Additionally, the as synthesized AgNCs do not influence the selectivity of the aptamer itself. For example, Sun et al. reported a one-step process to synthesize silver nanoclusters by specific aptamer which can selectively image the nuclei of CCRF cells, clearly demonstrates the strength of the aptamer capsulated Ag clusters. Anterior gradient protein 2 homolog (AGR), a homolog of xenopus anterior gradient-2 (XAG-2) of Xenopus laevis, is a typical protein that secret by gland cancer cell. Since being discovered as a pro-oncogenic protein that weakens p53 gene activity in 2004. Clinical studies have shown that AGR is highly expressed in pancreatic, breast, and prostate cancer cells, etc. The molecular function and clinical relevance of AGR with variety cancers have thus been increasingly investigated. Specifically, it is a functional protein that plays a key role in variety of biological systems, including the development of vertebrate tissue and the inflammatory tissue injury response. Overall, Tian's results demonstrated that AGR overexpression could predict poor overall survival (OS) and poor time to tumor progression (TTP) of all solid tumor patients. Therefore, fluorescence recognizing of AGR is important for detecting gland cancer cells. At present, a number of reports related with AGR have been reported, but few on specific recognition probes. Through a series of screening, Wu et al. discovered AGR's corresponding aptamer “C14B1”. Few years later, Hu et al. successfully achieved the direct detection of AGR in vitro. However, in the cell imaging field, there is scarcely report on AGR detection. Therefore, synthesis of fluorescent AgNCs conjugating with aptamer to target AGR could provide a novel method for recognizing human gland cancer cell with a high selectivity, efficiency, and low cytotoxicity. In this paper, modified AGR aptamer (MA) were used as template to synthesize AgNCs. Specifically, MA's sequence is 5′-CGG GTG GGA GTT GTG GGG GGG GGT GGG AGG GTT TTTTT CCC CCC CCC CCC-3′ (50 bases). This sequence consists of two functional parts, AGR-apt sequence for recognition AGR in breast cancer (MCF-7) cells, where 12 cytosine base sequence (12C) for effectively preparing fluorescent AgNCs. According to Li's research, a T5 loop (-TTTTT-) could enhance the fluorescence intensity and avoid the influence of space hindrance. It was incorporated between the 3′ end of the apt and 12C sequence. Eventually, according to optimized reaction conditions, MA stabilized silver nanocluster (MA@AgNCs) with a small size, suitable stability, good selectivity was prepared. The fluorescence excitation peak and emission peak of MA@AgNCs were located at 510 nm and 565 nm respectively with a quantum yield as high as 87.43%. Moreover, MA@AgNCs shows descent specific recognition of MCF-7 cells, suggesting the prepared MA@AgNCs have the ability to selective target gland cancer cell and potentially utilized for clinical diagnosis and treatment.