Recent progress of aptamer‒drug conjugates in cancer therapy

Aptamers are single-stranded DNA or RNA sequences that can specifically bind with the target protein or molecule via specific secondary structures. Compared to antibody-drug conjugates (ADC), aptamer‒drug conjugate (ApDC) is also an efficient, targeted drug for cancer therapy with a smaller size, higher chemical stability, lower immunogenicity, faster tissue penetration, and facile engineering. Despite all these advantages, several key factors have delayed the clinical translation of ApDC, such as in vivo off-target effects and potential safety issues. In this review, we highlight the most recent progress in the development of ApDC and discuss solutions to the problems noted above.

Recent progress in aptamer-based microfluidics for the detection of circulating tumor cells and extracellular vesicles / 药物分析学报

Liquid biopsy is a technology that exhibits potential to detect cancer early,monitor therapies,and predict cancer prognosis due to its unique characteristics,including noninvasive sampling and real-time analysis.Circulating tumor cells(CTCs)and extracellular vesicles(EVs)are two important components of circu-lating targets,carrying substantial disease-related molecular information and playing a key role in liquid biopsy.Aptamers are single-stranded oligonucleotides with superior affinity and specificity,and they can bind to targets by folding into unique tertiary structures.Aptamer-based microfluidic platforms offer new ways to enhance the purity and capture efficiency of CTCs and EVs by combining the advantages of microfluidic chips as isolation platforms and aptamers as recognition tools.In this review,we first briefly introduce some new strategies for aptamer discovery based on traditional and aptamer-based micro-fluidic approaches.Then,we subsequently summarize the progress of aptamer-based microfluidics for CTC and EV detection.Finally,we offer an outlook on the future directional challenges of aptamer-based microfluidics for circulating targets in clinical applications.

Advancement in Aptamer-based Biosensors for Gastric Cancer and Therapeutic Strategies / 中国生物化学与分子生物学报

The timely diagnosis of early gastric cancer is important for guiding the choice of treatment and prolonging the survival of patients. However, current screening of early gastric cancer still relies on endoscopic examination due to the lack of sensitive, accurate, and convenient screening tools. The cost of large-scale screening through gastrointestinal endoscopy is high and many countries and regions cannot afford it. At present, many types of biomarkers have been proved to own the ability to predict and diagnose tumors. Aptamer, as single-stranded oligonucleotides DNA or RNA, can be used to construct sensitive and reliable biosensors based on fluorometry, colorimetric, electrochemistry, etc. through label modification, coupling with various novel materials, etc. Additionally, it is also widely used in the field of precision medicine due to its small molecular weight, high specificity, and natural biological properties. We summarized and concluded aptamer-based gastric cancer diagnostic and therapeutic studies to help researchers quickly get access to tumor-related aptamers screening process, biosensor construction and optimization methods, and therapeutic strategies. This study aimed to provide a reference for the subsequent development of gastric cancer-related aptamers that meet clinical needs and assist in the endoscopic examination, diagnosis, and follow-up.

T cell immunotherapy mediated by dual-affinity aptamer targeted liposome / 药学学报

Redirecting immune cells to the tumor cells and enhancing its anti-tumor immune response is a very promising cancer treatment strategy. AS1411 aptamers have high affinity for malignant tumors with high nucleolin expression, and cytotoxic T lymphocyte associated protein 4 (CTLA-4) aptamers can specifically bind to CTLA-4, which is expressed by T cells. In this study, a dual-affinity aptamer targeted liposome (Dat. Lipo) was constructed based on AS1411 aptamer and CTLA-4 aptamer, and its immunotherapeutic effect on T cells was studied. After the aptamer was modified with cholesterol, Dat. Lipo was prepared by instillation method; its effect of redirecting T cells was determined by confocal micrographs; its T cell immunotherapy effect was evaluated by cell counting kit-8 (CCK8) and T cell penetration was evaluated by tumor spheroids. The results showed that compared with liposomes loaded with one type aptamer, Dat. Lipo could effectively promote the redirection of T cells to tumor cells; Dat. Lipo had good biosafety and immunotherapeutic effect on MCF-7 and HepG2 cells in a concentration-dependent manner; Dat. Lipo could also promote T cells to infiltrate into the tumor spheroids and enhance the immunotherapy effect of T cells in different dimensions. In summary, Dat. Lipo can use the high affinity of aptamers to redirect T cells to tumor cells, enhance the effect of immunotherapy, and has a promising application prospect in tumor therapy. This study was approved by the Examination Committee of Cancer Hospital of Xiangya School of Medicine, Central South University, Hunan Cancer Hospital.

Preparation and Biodistribution of 131I-labeled Hepatoma Nucleic Acid Nanotrain / 中山大学学报(医学科学版)

ObjectiveTo construct 131Ⅰ-labeled hepatoma nucleic acid nanotrain and to explore its feasibility as a new nuclide carrier targeting hepatoma. MethodsThree short nucleic acid chains self-assembled to a long nucleic acid chain after being annealed， and 131Ⅰ-NT was obtained by radioiodine labeling using chloramine T method. The labeling efficiency and radiochemical purity of the nanoparticles were measured by paper chromatography. The stability of the labeled products in vitro at different temperatures and different storage solvents was detected. The specific uptake of nanoparticles by hepatocellular carcinoma cells was observed by laser confocal microscopy， and the radioactive uptake ratio of 131Ⅰ-NT combined with human hepatocellular carcinoma cell HepG2 and normal hepatocyte L02 was measured. The biodistribution of 131Ⅰ-NT was obtained through injecting 131Ⅰ-NT into HepG2 tumor-bearing mice via tail vein. ResultsThe labeling rate of 131Ⅰ-NT was （93.05±0.74） %， and the radiochemical purity post purification was （98.35±0.32） %. Its radiochemical purity in PBS and pure serum at 4℃ for 24 h was （92.77±0.04） % and （89.43±0.2） %， respectively. The radioactivity uptake rate of HepG2 cells was higher than that of L02 cells after 131Ⅰ-NT was incubated with two kinds of cells for 2 h significantly. After injection of 131Ⅰ-NT through tail vein， the radioactive uptake per gram of tumor tissue were （4.9±0.55）%ID/g， （10.12±0.32）%ID/g and （4.25±0.31）%ID/g at 30 min， 1 h and 2 h， respectively. The T/M ratio was 7.33±2.04， 36.54±12.72 and 44.93±7.90 respectively. ConclusionsThe 131Ⅰ-labeled long chain nucleic acid nanotrain was constructed successfully， which possesses relatively high stability in vitro ， and high targeting ability to HepG2 cells in vitro and HepG2 tumor-bearing mouse model. Our study demonstrated that 131Ⅰ-NT may be a potential radionuclide carrier targeting human liver cancer， which provides a new idea for the targeted radionuclide diagnosis and treatment of hepatocellular carcinoma.

Drug discovery of sclerostin inhibitors

Sclerostin, a protein secreted from osteocytes, negatively regulates the WNT signaling pathway by binding to the LRP5/6 co-receptors and further inhibits bone formation and promotes bone resorption. Sclerostin contributes to musculoskeletal system-related diseases, making it a promising therapeutic target for the treatment of WNT-related bone diseases. Additionally, emerging evidence indicates that sclerostin contributes to the development of cancers, obesity, and diabetes, suggesting that it may be a promising therapeutic target for these diseases. Notably, cardiovascular diseases are related to the protective role of sclerostin. In this review, we summarize three distinct types of inhibitors targeting sclerostin, monoclonal antibodies, aptamers, and small-molecule inhibitors, from which monoclonal antibodies have been developed. As the first-in-class sclerostin inhibitor approved by the U.S. FDA, the monoclonal antibody romosozumab has demonstrated excellent effectiveness in the treatment of postmenopausal osteoporosis; however, it conferred high cardiovascular risk in clinical trials. Furthermore, romosozumab could only be administered by injection, which may cause compliance issues for patients who prefer oral therapy. Considering these above safety and compliance concerns, we therefore present relevant discussion and offer perspectives on the development of next-generation sclerostin inhibitors by following several ways, such as concomitant medication, artificial intelligence-based strategy, druggable modification, and bispecific inhibitors strategy.

Preliminary study of ssDNA aptamer cytotoxicity on RhD+ red blood cells / 中国输血杂志

【Objective】 To investigate the effect of ssDNA aptamer of RhD blood group antigen on erythrocyte toxicity. 【Methods】 Two full-length ssDNA aptamers(82 bp) of RhD blood group antigen were obtained by gene synthesis.Five samples of whole blood with EDTA anticoagulant were collected to prepare red blood cell suspensions (4×107/mL), which were split into 10 tubes(100 μL/tube), corresponding to 5 experimental groups and 5 controls.Two monospecific full-length ssDNA sequences (100 pmol/μL, 5μL each) were added into the experimental group, while the same amount of normal saline into the control.After treatment, the experimental group and the control were incubated for 60 min at 37℃.After washing, they were suspended in LISS solution and stored at 4℃.The experimental group and the control were set according to different time point during storage (1 h, 1 d, 3 d, 10 d and 17 d), with 5 tubes in each group.For erythrocytes in LISS suspension at different storage time, Annexin V labeled with FITC was used as a probe to label the phosphatidylserine (PS) content and Fluo-4 to label Ca2+ .The eversion of PS and the change of Ca2+ concentration in red blood cells in LISS suspensions were determined by flow cytometry. 【Results】 After incubation, all groups were examined under the light microscope.No agglutination occurred in the experimental group, while agglutination occurred in the control.Flow cytometry showed that the number of Annexin V-FITC staining cells of suspended erythrocytes at the same storage time-point was similar between the experimental group and the control, with no significant differences.In the experimental group, apoptosis rate of Annexin V cells at 10-day storage(6.06±1.38) was significantly higher than that at 1-hour storage(P<0.05), so as at 17-day storage(7.77±1.23) than 1-hour, 1-day and 3-day storage(P<0.05). The apoptosis rate of Fluo-4 AM cell in suspended RBCs at the same storage time-point was similar between the two groups(P>0.05). In the experimental group, the apoptosis rate of Fluo-4 AM cell at the 3-day, 10-day and 17-day storage was 20.84±4.16, 22.35±3.37 and 27.06±2.81, respectively(P<0.05). 【Conclusion】 ssDNA aptamer was not found to have any cytotoxic effects on red blood cells, and RhD ssDNA aptamer may be used as a material for the detection and preparation of universal blood.

Research progress in design strategy and application of aptamers for targeted delivery of siRNA / 中国药理学通报

RNA interference induced by small interfering (siR¬NA) has shown great potential in disease treatment.However, due to the poor stability of siRNA and lack of targeting, it is still challenging to deliver siRNA to target tissues/cells and induce gene silencing.Aptamer is a kind of oligonucleotide sequence that can specifically recognize the target.Covalently binding aptamers with siRNA or linking with other siRNA carriers can guide siRNA into target tissues/cells.In this review we summa¬ rize the research progress in the design strategy and application of aptamer-based targeted deliver)' of siRNA in the treatment of diseases in recent years, and discuss the challenges and pros-pects of aptamer-mediated siRNA deliver>r in clinical transforma¬tion.

Recent advances in quantum dots-based biosensors for antibiotics detection / 药物分析学报

Antibiotics are a category of chemical compounds used to treat bacterial infections and are widely applied in cultivation,animal husbandry,aquaculture,and pharmacy.Currently,residual antibiotics and their metabolites pose a potential risk of allergic reactions,bacterial resistance,and increased cancer incidence.Residual antibiotics and the resulting bacterial antibiotic resistance have been recognized as a global challenge that has attracted increasing attention.Therefore,monitoring antibiotics is a critical way to limit the ecological risks from antibiotic pollution.Accordingly,it is desirable to devise new analytical platforms to achieve efficient antibiotic detection with excellent sensitivity and specificity.Quantum dots(QDs)are regarded as an ideal material for use in the development of antibiotic detection biosensors.In this review,we characterize different types of QDs,such as silicon,chalcogenide,carbon,and other doped QDs,and summarize the trends in QD-based antibiotic detection.QD-based sensing applications are classified according to their recognition strategies,including molecularly imprinted polymers(MIPs),aptamers,and immunosensors.We discuss the advantages of QD-derived antibiotic sensors,including low cost,good sensitivity,excellent stability,and fast response,and illustrate the current challenges in this field.

Computer-aided aptamers screening technologies: a review / 生物工程学报

The computer information technology that has penetrated into every aspect of our lives, can not only assist the screening of drugs, but also simulate the effect of drugs. At present, computer-aided technologies have been used to screen aptamers, which play an important role in improving the screening efficiency and screening high affinity binding aptamers. This review summarized the screening methods of aptamers through computer-aided sequence evaluation, structural analysis and molecular docking.

Determination of bisphenol A in water by truncated aptamer-fluorescence method / 预防医学

Objective@#To establish a fluorescence method based on turncated aptamer for the determination of bisphenol A in water.@*Methods@#The bisphenol A truncated aptamer containing 38 bases was selected as a recognition module, and was modified with the fluorophore 6-FAM at the 5'end. The 3'end of the complementary sequence cDNA was modified with the quencher DABCYL. The standard solutions of bisphenol A and interfering compounds were configured. The detection system was established after optimizing the number of bases in cDNA, the concentration ratio of truncated aptamer to cDNA, the incubation temperature and time, and the pH of the buffer. The specificity and recovery experiments were carried out. @*Results@#When the complementary sequence cDNA included 9 bases, the concentration ratio of the truncated aptamer to cDNA was 1:1.5, the pH value of the buffer solution was 7.5, the cDNA was incubated at 55 ℃ for 60 minutes, in the concentration range of 10-75 pmol/L, the linear regression equation was y=2 230.7x+110 825, the correlation coefficient was 0.926. The limits of detection was 3.3 pmol/L. The difference values of fluorescence intensity between tetrabromobisphenol A, estradiol, estriol, bisphenol S and bisphenol A were obviously different, so there was no significant interference to the test result. The recovery rates were 97.8%, 98.8% and 102.3% with the spiked concentrations of 20.0, 40.0 and 60.0 pmol/L. The relative standard deviations were 4.4%, 2.1% and 2.6% (n=5), respectively. @*Conclusion@#The fluorescence method based on turncated aptamer has the advantages of easy operation, high sensitivity and specificity, which can be used for the determination of bisphenol A in water.

The Interaction between Aptamer and Beclomethasone Based on High Resolution Mass Spectrometry and Molecular Docking / 中国生物化学与分子生物学报

Beclomethasone is an effective glucocorticoid, and beclomethasone-aptamer is a short single-stranded DNA with affinity and specificity to beclomethasone. The interaction between them is still unclear. The study of the interaction between aptamers and beclomethasone has a certain significance for the application of aptamers. In this study, high-resolution Fourier transform ion cyclotron resonance mass spectrometer (FT-MS) and molecular docking simulation technology were used to study the interaction between aptamer and beclomethasone. Firstly, under the optimized conditions of high-resolution mass spectrometry parameters, the complex of aptamer and beclomethasone was detected by the negative ion scanning mode with the electrospray ion source. Based on the results of high-resolution mass spectrometry, most of the compounds were -8-valent ions, and their dissociation constant K

Screening and Identification of Nucleic Acid Aptamers Specifically Binding to Human Lipocalin 6 / 中国生物化学与分子生物学报

It is an urgent and difficult task to establish a simple and efficient method for identifying and isolating sperm cells from mixed stains in forensic science. Nucleic acid aptamers targeting sperm cell-surface proteins can be used for the separation and purification of sperms from mixed stain samples. Human lipocalin 6 (hLCN6) is an epididymal secreted protein that binds to the head and tail of sperm cells and is associated with sperm maturation. Using the systematic evolution of ligands by the exponential enrichment (SELEX) technique, magnetic bead-bound hLCN6 was used as the target molecule to screen for aptamers with high affinity and specificity to hLCN6 from a random single-stranded DNA (ssDNA) library. Through 15 rounds of positive selection and 3 rounds of negative selection, 24 clones were selected and subjected to sequence analysis. Subsequently, 4 candidate aptamers were selected and further examined for their binding affinity and specificity by enzyme-linked oligonucleotide adsorption (ELONA) and cell binding assays. One aptamer (H2) against hLCN6 with a high affinity and specificity was isolated and investigated by dot blotting and immunofluorescence staining. The result revealed that the candidate aptamer H2 with a dissociation constant of (3. 21 ± 0. 75) nmol/ L was able to recognize and specifically bind to hLCN6. The aptamer H2 also showed high affinity and specificity to human sperms in vitro, which establishes the foundation for the separation of sperm cells from mixed stain based on nucleic acid-protein interactions and provides a new scheme.

Selection and appraisement of nucleic acid aptamers for castration resistant prostate cancer cells based on Cell-SELEX / 西安交通大学学报(医学版)

【Objective】 To screen nucleic acid aptamers that can specifically recognize castration-resistant prostate cancer （CRPC） cells by Cell-SELEX. 【Methods】 For Cell-SELEX selection， CRPC cell lines C4-2 were used as positive control cells， while androgen-dependent prostate cancer cell lines LNCap were used as negative control cells. The 5’end of the upstream primers was labeled with FITC， and the 5’end of the downstream primers was labeled with biotin. Single-stranded DNA （ssDNA） collected from each round of screening was used as template for PCR amplification and purification. The biotin-streptavidin magnetic bead separation was used to isolate PCR product for the next round of screening. The process of Cell-SELEX was analyzed by flow cytometry. ssDNA products of the last round were collected for PCR amplification， purification， cloning and DNA sequencing. The secondary structure of selected DNA aptamers was predicted. Dissociation constants of the two aptamers were calculated. Flow cytometry and confocal microscopy were used to evaluate selective binding of aptamers to CRPC cells and tissues. 【Results】 The binding rate of DNA products to CRPC cells gradually increased with the increase of selection cycles， reaching the highest in the last round. DNA structure prediction analysis showed that the secondary structure of aptamers CRPC-1 and CRPC-2 was mainly stem-loop structure. Flow cytometry analysis and confocal images showed that both CRPC-1 and CRPC-2 could specifically target C4-2 cells. In addition， immunohistofluorescence assay showed that CRPC-1 could specifically target CRPC tissues. 【Conclusion】 Cell-SELEX can be used to screen aptamers that specifically target CRPC cells and tissues， which provides experimental basis for early screening and targeted diagnosis of CRPC. It is of significance for treatment plan adjustment and prognosis improvement of prostate cancer.

The effect of different guanine base number on fluorescence intensity of DNA/ silver nanoclusters / 药学实践杂志

Objective To investigate the effect of different guanine base numbers on the fluorescence intensity of DNA/ silver nanoclusters through C-G base complementary pairing, in order to explore a new method for the construction of fluorescent probe switches. Methods Designed complementary sequences of aptamer parts of a series of silver nanoclusters by using the nucleic acid base complementary pairing principle, and investigated the effect of the number of G bases exposed in the aptamer sequence on the fluorescence signal. Results Base G could enhance the fluorescence signal intensity of silver nanoclusters, and the fluorescence signal strength was positively correlated with the number of G bases. The fitting linear equation was Y=1726.1X+8972.5, r=0.9789. Conclusion This study is a great reference for the regulation of fluorescence intensity of silver nanoclusters and the design of G quadruplet aptamer fluorescent probe switch.

Molecularly engineered truncated tissue factor with therapeutic aptamers for tumor-targeted delivery and vascular infarction

Selective occlusion of tumor vasculature has proven to be an effective strategy for cancer therapy. Among vascular coagulation agents, the extracellular domain of coagulation-inducing protein tissue factor, truncated tissue factor (tTF), is the most widely used. Since the truncated protein exhibits no coagulation activity and is rapidly cleared in the circulation, free tTF cannot be used for cancer treatment on its own but must be combined with other moieties. We here developed a novel, tumor-specific tTF delivery system through coupling tTF with the DNA aptamer, AS1411, which selectively binds to nucleolin receptors overexpressing on the surface of tumor vascular endothelial cells and is specifically cytotoxic to target cells. Systemic administration of the tTF-AS1411 conjugates into tumor-bearing animals induced intravascular thrombosis solely in tumors, thus reducing tumor blood supply and inducing tumor necrosis without apparent side effects. This conjugate represents a uniquely attractive candidate for the clinical translation of vessel occlusion agent for cancer therapy.

Gold nanorods-mediated efficient synergistic immunotherapy for detection and inhibition of postoperative tumor recurrence

Tumor recurrence after surgery is the main cause of treatment failure. However, the initial stage of recurrence is not easy to detect, and it is difficult to cure in the late stage. In order to improve the life quality of postoperative patients, an efficient synergistic immunotherapy was developed to achieve early diagnosis and treatment of post-surgical tumor recurrence, simultaneously. In this paper, two kinds of theranostic agents based on gold nanorods (AuNRs) platform were prepared. AuNRs and quantum dots (QDs) in one agent was used for the detection of carcinoembryonic antigen (CEA), using fluorescence resonance energy transfer (FRET) technology to indicate the occurrence of

Nucleic acid aptamer-based traditional Chinese medicine application:therapy,targeting and diagnosis / 中国中药杂志

Nucleic acid aptamers, broad-spectrum target-specific single-stranded oligonucleotides, serve as molecules in targeted therapy, targeted delivery and disease diagnosis for the treatment of tumor or microbial infection and clinical detection. Due to the existence of components in the use of traditional Chinese medicine(TCM), the target is difficult to concentrate and the specificity of treatment is poor. The effective components of TCM are toxic components, so a highly sensitive detection method is urgently needed to reduce the toxicity problem at the same time. The combined application of TCM and modern medical treatment strategy are difficult and cannot improve the therapeutic effect. Aptamers, advantageous in biosensors, aptamer-nanoparticles for targeted drug delivery, and aptamer-siRNA chimeras, are expected to connect Chinese medicinals with nanotechnology, diagnostic technology and combined therapies. We summarized the preparation, screening, and modification techniques of nucleic acid aptamers and the biomedical applications and advantages in therapy, targeting, and diagnosis, aiming at providing a reference for the in-depth research and development in TCM.

Towards wearable and implantable continuous drug monitoring:A review / 药物分析学报

Continuous drug monitoring is a promising alternative to current therapeutic drug monitoring strategies and has a strong potential to reshape our understanding of pharmacokinetic variability and to improve individualised therapy.This review highlights recent advances in biosensing technologies that support continuous drug monitoring in real time.We focus primarily on aptamer-based biosensors,wearable and implantable devices.Emphasis is given to the approaches employed in constructing biosensors.We pay attention to sensors'biocompatibility,calibration performance,long-term characteristics stability and measurement quality.Last,we discuss the current challenges and issues to be addressed in continuous drug monitoring to make it a promising,future tool for individualised therapy.The ongoing efforts are expected to result in fully integrated implantable drug biosensing technology.Thus,we may anticipate an era of advanced healthcare in which wearable and implantable biochips will automatically adjust drug dosing in response to patient health conditions,thus enabling the management of diseases and enhancing individualised therapy.

A smart dual-drug nanosystem based on co-assembly of plant and food-derived natural products for synergistic HCC immunotherapy

Nanotechnology has emerged as an ideal approach for achieving the efficient chemo agent delivery. However, the potential toxicity and unclear internal metabolism of most nano-carriers was still a major obstacle for the clinical application. Herein, a novel "core‒shell" co-assembly carrier-free nanosystem was constructed based on natural sources of ursolic acid (UA) and polyphenol (EGCG) with the EpCAM-aptamer modification for hepatocellular carcinoma (HCC) synergistic treatment. As the nature products derived from food-plant, UA and EGCG had good anticancer activities and low toxicity. With the simple and "green" method, the nanodrugs had the advantages of good stability, pH-responsive and strong penetration of tumor tissues, which was expected to increase tumor cellular uptake, long circulation and effectively avoid the potential defects of traditional carriers. The nanocomplex exhibited the low cytotoxicity in the normal cells