Identification of a novel DNA aptamer that selectively targets lung cancer serum

Screening and application of aptamers as fluorescent biosensors for selective and sensitive detection of hepatocellular carcinoma and in vivo targeted delivery studies

The incidence of primary hepatocellular carcinoma (HCC) has recently ranked fifth in the world, and the incidence rate is increasing year by year worldwide. Therefore, early diagnosis is the highest priority in the treatment of HCC. In this paper, four anti-HCC aptamers were obtained using magnetic bead SELEX technology. Among them, Apt-1 had the smallest Kd value(5.9 nM) and the highest affinity. Flow cytometry results showed that the FITC-aptamers only specifically recognized HCC serum. Circular dichronism (CD) spectral characterization showed a positive peak near 275 nm and a negative peak near 250 nm for all aptamers, elucidating that the secondary structure formed by the candidate aptamers was a stem-loop B-DNA structure. In addition, molecular docking simulations showed that the binding of the HCC target to the candidate aptamer sequences was mainly dominated by hydrogen bonding. The results of the aptamer sensing performance analysis showed that under the optimized assay conditions, a linear relationship (ranging from 1 nM to 1 µM) was achieved, with a limit of detection (LOD) down to 0.75 nM and a LOQ of 2.32 nM. This was further validated in clinical samples, with a positive detection rate of more than 90%. Furthermore, aptamer-mediated in vivo delivery of luciferase mRNA showed that Apt-1-luciferase mRNA could be targeted to the liver and hepatic luciferase expression was significantly increased. These results demonstrate that the aptamer paves the way for clinical application, evidencing  significant potential to offer reference information for early diagnosis.

Aptamers combined with immune checkpoints for cancer detection and targeted therapy: A review

In recent years, remarkable strides have been made in the field of immunotherapy, which has emerged as a standard treatment for many cancers. As a kind of immunotherapy drug, monoclonal antibodies employed in immune checkpoint therapy have proven beneficial for patients with diverse cancer types. However, owing to the extensive heterogeneity of clinical responses and the complexity and variability of the immune system and tumor microenvironment (TME), accurately predicting its efficacy remains a challenge. Recent advances in aptamers provide a promising approach for monitoring alterations within the immune system and TME, thereby facilitating targeted immunotherapy, particularly focused on immune checkpoint blockade, with enhanced antitumor efficiency. Aptamers have been widely used in tumor cell detection, biosensors, drug discovery, and biomarker screening due to their high specificity and high affinity with their targets. This review aims to comprehensively examine the research status and progress of aptamers in cancer diagnosis and immunotherapy, with a specific emphasis on those related to immune checkpoints. Additionally, we will discuss the future research directions and potential therapeutic targets for aptamer-based immune checkpoint therapy, aiming to provide a theoretical basis for targeting immunotherapy molecules and blocking tumor immune escape.

Recent progress of SELEX methods for screening nucleic acid aptamers

Nucleic acid aptamers are oligonucleotide sequences screened by an in vitro methodology called Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Known as "chemical antibodies", aptamers can achieve specific recognition towards the targets through conformational changes with high affinity, and possess multiple attractive features including, but not limited to, easy and inexpensive to prepare by chemical synthesis, relatively stable and low batch-to-batch variability, easy modification and signal amplification, and low immunogenicity. Now, aptamers are attracting researchers' attentions from more than 25 disciplines, and have showed great potential for application and economic benefits in disease diagnosis, environmental detection, food security, drug delivery and discovery. Although some aptamers exist naturally as the ligand-binding elements of riboswitches, SELEX is a recognized method for aptamers screening. After thirty-two years of development, a series of SELEX methods have been investigated and developed, as well as have shown unique advantages to improve sequence performances or to explore screening mechanisms. This review would mainly focus on the novel or improved SELEX methods that are available in the past five years. Firstly, we present a clear overview of the aptamer's history, features, and SELEX development. Then, we highlight the specific examples to emphasize the recent progress of SELEX methods in terms of carrier materials, technical improvements, real sample-improved screening, post-SELEX and other methods, as well as their respects of screening strategies, implementation features, screening parameters. Finally, we discuss the remaining challenges that have the potential to hinder the success of SELEX and aptamers in practical applications, and provide the suggestions and future directions for developing more convenient, efficient, and stable SELEX methods in the future.

Bio-SELEX: A Strategy for Biomarkers Isolation Directly from Biological Samples

Bio-SELEX is a revolutionary method for the discovery of novel biomarkers within biological samples, offering profound insights into diagnosing both infectious and non-infectious diseases. This innovative strategy involves three crucial steps: Traditional SELEX, Pull Down, and mass spectrometry. Firstly, Traditional SELEX involves the systematic selection of specific nucleic acid sequences (aptamers) that bind to the target molecules of interest. These aptamers are generated through iterative rounds of selection, amplification, and enrichment, ultimately yielding highly selective ligands. Secondly, the Pull-Down phase employs these aptamers to capture and isolate the target biomarkers from complex biological samples. This step ensures the specificity of the selected aptamers in binding to their intended targets. Lastly, mass spectrometry is utilized to identify and quantify the captured biomarkers, providing precise information about their presence and concentration in the sample. These quantitative data are invaluable in disease diagnosis and monitoring. Bio-SELEX's significance lies in its ability to discover biomarkers for a wide range of diseases, spanning infectious and non-infectious conditions. This approach holds great promise for early disease detection, personalized medicine, and the development of targeted therapies. By harnessing the power of aptamers and mass spectrometry, Bio-SELEX advances our understanding of disease biology and opens new avenues for improved healthcare.

Molecular targets, therapeutic agents and multitasking nanoparticles to deal with cancer stem cells: A narrative review

There is increasing evidence that malignant tumors are initiated and maintained by a sub-population of tumor cells that have similar biological properties to normal adult stem cells. This very small population of Cancer Stem Cells (CSC) comprises tumor initiating cells responsible for cancer recurrence, drug resistance and metastasis. Conventional treatments such as chemotherapy, radiotherapy and surgery, in addition to being potentially toxic and non-specific, may paradoxically increase the population, spread and survival of CSCs. Next-generation sequencing and omics technologies are increasing our understanding of the pathways and factors involved in the development of CSCs, and can help to discover new therapeutic targets against CSCs. In addition, recent advances in nanomedicine have provided hope for the development of optimal specific therapies to eradicate CSCs. Moreover, the use of artificial intelligence and nano-informatics can elucidate new drug targets, and help to design drugs and nanoparticles (NPs) to deal with CSCs. In this review, we first summarize the properties of CSCs and describe the signaling pathways and molecular characteristics responsible for the emergence and survival of CSCs. Also, the location of CSCs within the tumor and the effect of host factors on the creation and maintenance of CSCs are discussed. Newly discovered molecular targets involved in cancer stemness and some novel therapeutic compounds to combat CSCs are highlighted. The optimum properties of anti-CSC NPs, including blood circulation and stability, tumor accumulation and penetration, cellular internalization, drug release, endosomal escape, and aptamers designed for specific targeting of CSCs are covered. Finally, some recent smart NPs designed for therapeutic and theranostic purposes to overcome CSCs are discussed.

The application of Aptamer in biomarker discovery

Biomarkers are detectable molecules that can reflect specific physiological states of cells, organs, and organisms and therefore be regarded as indicators for specific diseases. And the discovery of biomarkers plays an essential role in cancer management from the initial diagnosis to the final treatment regime. Practically, reliable clinical biomarkers are still limited, restricted by the suboptimal methods in biomarker discovery. Nucleic acid aptamers nowadays could be used as a powerful tool in the discovery of protein biomarkers. Nucleic acid aptamers are single-strand oligonucleotides that can specifically bind to various targets with high affinity. As artificial ssDNA or RNA, aptamers possess unique advantages compared to conventional antibodies. They can be flexible in design, low immunogenicity, relative chemical/thermos stability, as well as modifying convenience. Several SELEX (Systematic Evolution of Ligands by Exponential Enrichment) based methods have been generated recently to construct aptamers for discovering new biomarkers in different cell locations. Secretome SELEX-based aptamers selection can facilitate the identification of secreted protein biomarkers. The aptamers developed by cell-SELEX can be used to unveil those biomarkers presented on the cell surface. The aptamers from tissue-SELEX could target intracellular biomarkers. And as a multiplexed protein biomarker detection technology, aptamer-based SOMAScan can analyze thousands of proteins in a single run. In this review, we will introduce the principle and workflow of variations of SELEX-based methods, including secretome SELEX, ADAPT, Cell-SELEX and tissue SELEX. Another powerful proteome analyzing tool, SOMAScan, will also be covered. In the second half of this review, how these methods accelerate biomarker discovery in various diseases, including cardiovascular diseases, cancer and neurodegenerative diseases, will be discussed.