Aptamer-based approaches for in vitro molecular detection of cancer

Engineered aptamers for molecular imaging

Molecular imaging, including quantification and molecular interaction studies, plays a crucial role in visualizing and analysing molecular events occurring within cells or organisms, thus facilitating the understanding of biological processes. Moreover, molecular imaging offers promising applications for early disease diagnosis and therapeutic evaluation. Aptamers are oligonucleotides that can recognize targets with a high affinity and specificity by folding themselves into various three-dimensional structures, thus serving as ideal molecular recognition elements in molecular imaging. This review summarizes the commonly employed aptamers in molecular imaging and outlines the prevalent design approaches for their applications. Furthermore, it highlights the successful application of aptamers to a wide range of targets and imaging modalities. Finally, the review concludes with a forward-looking perspective on future advancements in aptamer-based molecular imaging.

Unveiling the underpinnings of various non-conventional ELISA variants: a review article

INTRODUCTION

Enzyme-linked immunosorbent assay (ELISA) is a key bio-analytical technique used for the detection of a large array of antigenic substances of scientific, clinical, food safety, and environmental importance. The assay primarily involves capturing and detecting target analytes using specific antigen-antibody interactions. The wide usage of ELISA shoulders on its high specificity and reproducibility. Notwithstanding, the conventional microwell plate-based format of ELISA has some major drawbacks, such as long assay time (4 - 18 h), large sample volumes requirement (100 - 200 μL), lack of multiplicity, and burdensome procedures that limit its utility in rapid and affordable diagnostics.

AREAS COVERED

Here, we reviewed microfluidic-ELISA, paper-ELISA, aptamer-ELISA, and those based on novel incubation such as heat-ELISA, pressure-ELISA, microwave-ELISA, and sound-ELISA. Further, the current trends and future prospects of these ELISA protocols in clinical diagnostics are discussed.

EXPERT OPINION

The reviewed non-conventional ELISA formats are relatively rapid, require low reagent volumes, are multiplexable, and could be performed in a low-cost setup. In our opinion, these non-conventional variants of ELISA are on a par with the conventional format for clinical diagnostics and fundamental biological research and hold added clinical translational potential for quick, inexpensive, and convenient measurements.

Aptamer-Based Sensors for Thrombin Detection Application

Thrombin facilitates the aggregation of platelet in hemostatic processes and participates in the regulation of cell signaling. Therefore, the development of thrombin sensors is conducive to comprehending the role of thrombin in the course of a disease. Biosensors based on aptamers screened by SELEX have exhibited superiority for thrombin detection. In this review, we summarized the aptamer-based sensors for thrombin detection which rely on the specific recognitions between thrombin and aptamer. Meanwhile, the unique advantages of different sensors including optical and electrochemical sensors were also highlighted. Especially, these sensors based on electrochemistry have the potential to be miniaturized, and thus have gained comprehensive attention. Furthermore, concerns about aptamer-based sensors for thrombin detection, prospects of the future and promising avenues in this field were also presented.

Advances in aptamer-based nuclear imaging

Aptamers are short oligonucleotides that bind to specific target molecules. They have been extensively explored in biomedical applications, including biosensing, medical imaging, and disease treatment. Their adjustable affinity for specific biomarkers stimulates more translational efforts, such as nuclear imaging of tumors in preclinical and clinical settings. In this review, we present recent advances of aptamer-based nuclear imaging and compare aptamer tracers with other biogenic probes in forms of peptides, nanobodies, monoclonal antibodies, and antibody fragments. Fundamental properties of aptamer-based radiotracers are highlighted and potential directions to improve aptamer's imaging performance are discussed. Despite many translational obstacles to overcome, we envision aptamers to be a versatile tool for cancer nuclear imaging in the near future.

Chimeric antigen receptor-T cells immunotherapy for targeting breast cancer

Redirected chimeric antigen receptor (CAR) T-cells can recognize and eradicate cancer cells in a major histocompatibility complex independent manner. Genetic engineering of T cells through CAR expression has yielded great results in the treatment of hematological malignancies compared with solid tumors. There has been a constant effort to enhance the effectiveness of these living drugs, due to their limited success in targeting solid tumors. Poor T cell trafficking, tumor-specific antigen selection, and the immunosuppressive tumor microenvironment are considered as the main barriers in targeting solid tumors by CAR T-cells. Here, we reviewed the current state of CAR T-cell therapy in breast cancer, as the second cancer-related death in women worldwide, as well as some strategies adopted to keep the main limitations of CAR T-cells under control. Also, we summarized various approaches that have been developed to enhance the therapeutic outcomes of this treatment in solid tumors targeting.

Aptamer-based sensing of breast cancer biomarkers: a comprehensive review of analytical figures of merit

INTRODUCTION

Accurate determination of the aberrantly expressed biomarkers such as human epidermal growth factor receptor 2 (HER2), carcinoembryonic antigen (CEA), platelet-derived growth factor (PDGF), mucin 1 (MUC1), and vascular endothelial growth factor VEGF₁₆₅ have played an essential role in the clinical management of the breast cancer. Assessment of these cancer-specific biomarkers has conventionally relied on time-taking methods like the enzyme-linked immunosorbent assay and immunohistochemistry. However, recent development in the aptamer-based diagnostics has allowed developing tools that may substitute the conventional means of biomarker assessment in breast cancer. Adopting the aptamer-based diagnostic tools (aptasensors) to clinical practices will depend on their analytical performance on clinical samples.

AREAS COVERED

In this review, we provide an overview of the analytical merits of HER2, CEA, PDGF, MUC1, and VEGF₁₆₅ aptasensors. Scopus and Pubmed databases were searched for studies reporting aptasensor development for the listed breast cancer biomarkers in the past one decade. Linearity, detection limit, and response time are emphasized.

EXPERT OPINION

In our opinion, aptasensors have proven to be on a par with the antibody-based methods for detection of various breast cancer biomarkers. Though robust validation of the aptasensors on significant sample size is required, their ability to detect pathophysiological range of biomarkers suggest the possibility of future clinical adoption.

Novel devices for isolation and detection of bacterial and mammalian extracellular vesicles

Extracellular vesicles are spherical nanoparticles inherently released by almost all cell types. They acquire the cell's membrane and cytoplasmic characteristics offering abundant identical units that can be captured to recognize the cell of origin. The abundance of vital cell information and multifunctional roles in cellular processes has rendered them attention, particularly as promising biomarkers for disease diagnosis and use in potential drug delivery systems. This review provides insights into standard approaches towards cultivation and isolation of mammalian and bacterial extracellular vesicles. We assess gaps in conventional separation and detection technologies while also tracking developments in ongoing research. The review focuses on highlighting alternative state-of-the-art microfluidic devices that offer avenues for fast, cost-effective, precision-oriented capture and sensing of extracellular vesicles. Combining different detection technologies on an integrated "lab-on-a-chip" system has the prospective to provide customizable opportunities for clinical use of extracellular vesicles in disease diagnostics and therapeutic applications.

X-aptamers targeting Thy-1 membrane glycoprotein in pancreatic ductal adenocarcinoma

Modified DNA aptamers incorporated with amino-acid like side chains or drug-like ligands can offer unique advantages and enhance specificity as affinity ligands. Thy-1 membrane glycoprotein (THY1 or CD90) was previously identified as a biomarker candidate of neovasculature in pancreatic ductal adenocarcinoma (PDAC). The current study developed and evaluated modified DNA X-aptamers targeting THY1 in PDAC. The expression and glycosylation of THY1 in PDAC tumor tissues were assessed using immunohistochemistry and quantitative proteomics. Bead-based X-aptamer library that contains 108 different sequences was used to screen for high affinity THY1 X-aptamers. The sequences of the X-aptamers were analyzed with the next-generation sequencing. The affinities of the selected X-aptamers to THY1 were quantitatively evaluated with flow cytometry. Three high affinity THY1 X-aptamers, including XA-B217, XA-B216 and XA-A9, were selected after library screening and affinity binding evaluation. These three X-aptamers demonstrated a high binding affinity and specificity to THY1 protein and the THY1 expressing cell lines, using THY1 antibody as a comparison. The development of these X-aptamers provides highly specific and non-immunogenic affinity ligands for THY1 binding in the context of biomarker development and clinical applications. They could be further exploited to assist molecular imaging of PDAC targeting THY1.

An innovative cell selection approach in developing human cells overexpressing aspartyl/asparaginyl β-hydroxylase

Background and purpose:

Aspartyl/asparaginyl β-hydroxylase (ASPH) is abundantly expressed in malignant neoplastic cells. The establishment of a human cell line overexpressing ASPH could provide the native-like recombinant protein needed for developing theranostic probes. In the process of transfection, the obtained cells normally contain a range of cells expressing the different levels of the target of interest. In this paper, we report on our simple innovative approach in the selection of best-transfected cells with the highest expression of ASPH using subclone selection, quantitative real-time polymerase chain reaction, and gradual increment of hygromycin concentration.

Experimental approach:

To achieve this goal, human embryonic kidney (HEK 293T) cells were transfected with an ASPH-bearing pcDNA3.1/Hygro(+) vector. During antibiotic selection, single accumulations of the resistant cells were separately cultured and the ASPH mRNA levels of each flask were evaluated. The best subclones were treated with a gradually increasing amount of hygromycin. The ASPH protein expression of the obtained cells was finally evaluated using flow cytometry and immunocytochemistry.

Findings / Results:

The results showed that different selected subclones expressed different levels of ASPH. Furthermore, the gradual increment of hygromycin (up to 400mg/mL) improved the expression of ASPH. The best relative fold change in mRNA levels was 57.59 ± 4.11. Approximately 90.2% of HEK^ASPH cells overexpressed ASPH on their surface.

Conclusion and implications:

The experiments indicated that we have successfully constructed and evaluated a recombinant human cell line overexpressing ASPH on the surface. Moreover, our innovative selection approach provided an effective procedure for enriching highly expressing recombinant cells.