Xiaona Fang

Ovarian cancer is a significant and life-threatening malignancy among women worldwide. Selective tumor targeting by molecular agents is essential for the development of effective therapeutics and diagnostics. Recognizing the disparities between in vivo and in vitro environments, we have implemented an in vivo SELEX strategy to identify DNA aptamers capable of specifically localizing to ovarian tumors in situ. Aptamer L1 has emerged as a promising candidate with a high binding affinity to Insulin-like Growth Factor Binding Protein 3 (IGFBP3), a tumor-promoting protein overexpressed in ovarian cancer. Notably, aptamer L1 effectively downregulates IGFBP3 expression and suppresses ovarian cancer cell proliferation. The unique molecular characteristics of aptamer L1 underscore its potential as a theranostic agent for ovarian cancer.

Traditional screening of aptamers for small-molecule targets is often inefficient, typically requiring more than 13 rounds of selection. To address this inefficiency, we optimized the Capture-SELEX process by refining key factors that impact selection efficacy. By extending the length of the capture sequence and reducing the self-dissociation rate to minimize background noise, we significantly enhanced the screening efficiency. Utilizing meperidine (MPD), an addictive substance, as a model, we successfully identified aptamers within just six rounds. We further validated these optimized conditions using a multitarget mixed SELEX approach and successfully obtained high-affinity aptamers. To demonstrate the practical application of these aptamers, we developed two fluorescent biosensors incorporating MPD aptamers. This biosensor achieved a detection limit of 60 nM for MPD in artificial saliva and exhibited excellent specificity even in the presence of various interfering substances. This indicates that our method is effective for both single and mixed targets. By employing a 20-base-long capture sequence to minimize library self-dissociation, we have addressed the long-standing inefficiencies of Capture-SELEX, significantly improving the screening of small-molecule aptamers. This advancement is anticipated to greatly enhance the application of aptamers in small-molecule research and on-site drug detection.

The COVID-19 pandemic over recent years has shown a great need for the rapid, low-cost, and on-site detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, an aptamer-based colloidal gold nanoparticle lateral flow test strip was well developed to realize the visual detection of wild-type SARS-CoV-2 spike proteins (SPs) and multiple variants. Under the optimal reaction conditions, a low detection limit of SARS-CoV-2 S proteins of 0.68 nM was acquired, and the actual detection recovery was 83.3% to 108.8% for real-world samples. This suggests a potential tool for the prompt detection of SARS-CoV-2 with good sensitivity and accuracy, and a new method for the development of alternative antibody test strips for the detection of other viral targets.

The COVID-19 pandemic over the past years has shown a great need for rapid, low-cost and on-site detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this paper, an aptamer-based colloidal gold nanoparticle lateral flow test strip was well developed to realize the visual detection of wild type SARS-CoV-2 spike protein (SP) and multiple variants. Under the optimal reaction conditions, a low detection limit of SARS-CoV-2 S protein of 0.68 nM was acquired, and the actual detection recovery was 83.3% to 108.8% for real world samples. This suggests a potential tool for the prompt detection of SARS-CoV-2 with good sensitivity and accuracy, and a new method for the development of alternative antibody test strips for the detection of other viral targets.

With the outbreak of COVID-19, which is fast transmitting and highly contagious, the development of rapid, highly specific, and sensitive detection kits has become a research hotspot. The existing assay methods for SARS-CoV-2 are mainly based on enzymatic reactions, which require expensive reagents, hindering popular use, especially in resource-constrained areas. Herein, we propose an aptamer-based method for the assay of SARS-CoV-2 via binding of the spike protein using functionalized biomimetic nanochannels. To get the analogous effect of human ACE2, a receptor for the spike protein, the aptamer to bind to the spike S1 protein has been first screened by a SELEX technique and then immobilized on the previously prepared nanochannels. In the presence of SARS-CoV-2, the changes in steric hindrance and charge density on the surface of the nanochannels will affect the ion transport, along with a rapid electrochemical response. Our method has been successfully applied to detect the viral particles in clinical pharyngeal swab specimens in one step without sample treatment. We expect this rapid, reagent-free, and sensitive assay method to be developed as a useful tool for diagnosing COVID-19.

Diagnosis and treatment of ovarian cancer are based on intraoperative pathology and debulking surgery. The development of a novel molecular tool is significant for rapid intraoperative pathologic diagnosis, which instructs the decision-making on excision surgery and effective chemotherapy. In this work, we represent a DNA aptamer named mApoc46, which is generated from cell-SELEX by targeting patient-derived primary serous ovarian cancer (pSOC) cells. An average dissociation constant (K_d) was determined to be 0.15 ± 0.05 μM by flow cytometry. The mApoc46 aptamer displays a robust specificity to pSOC cells. Labeled with FAM, mApoc46 can selectively stain living pSOC cells in 30 min without staining commercial OC cell lines and cell lines associated with other cancers. Interestingly, FAM-mApoc46 displayed superb selectivity toward high-grade serous ovarian cancer (HG-SOC) tissues in frozen sections against low-grade SOC, ovarian borderline tumor, other nonepithelial ovarian tumors, and healthy ovarian tissue. These results lead to a potential application in the identification of OCs’ histological subtypes during operation. In the patient-derived tumor xenograft NCG mice model, Cy5-labeled mApoc46 was found to accumulate at the tumor area and served as an in vivo imaging probe. The mApoc46 probe shows a robust and stable performance to visualize SOC tumors in the body. Therefore, aptamer mApoc46 holds great potential in rapid intraoperative detection, pathological diagnosis, fluorescence image-guided cancer surgery, and targeted drug delivery and therapy.