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Myocardial infarction (MI) is highly related to cardiac arrest leading to death and organ damage. Radiological techniques and electrocardiography have been used as preliminary tests to diagnose MI; however, these techniques are not sensitive enough for early‐stage detection. A blood biomarker‐based diagnosis is an immediate solution, and due to the high correlation of troponin with MI, it has been considered to be a gold‐standard biomarker. In the present research, the cardiac biomarker troponin I (cTnI) was detected on an interdigitated electrode sensor with various surface interfaces. To detect cTnI, a capture aptamer‐conjugated gold nanoparticle probe and detection antibody probe were utilized and compared through an alternating sandwich pattern. The surface metal oxide morphology of the developed sensor was proven by microscopic assessments. The limit of detection with the aptamer‐gold‐cTnI‐antibody sandwich pattern was 100 aM, while it was 1 fM with antibody‐gold‐cTnI‐aptamer, representing 10‐fold differences. Further, the high performance of the sensor was confirmed by selective cTnI determination in serum, exhibiting superior nonfouling. These methods of determination provide options for generating novel assays for diagnosing MI. [ABSTRACT FROM AUTHOR]

Carcinoembryonic antigen (CEA) is a glycoprotein, one of the common tumor biomarkers, found at low levels in body fluids. Generally, overexpression of CEA is found in various cancers, including ovarian, breast, lung, colorectal, gastric, and pancreatic cancers. Since CEA is an important tumor biomarker, the quantification of CEA is helpful for diagnosing cancer, monitoring tumor progression, and the follow-up treatment. This research develops a highly sensitive sandwich aptasensor for CEA identification on an interdigitated electrode sensor. Carbon-based material was used to attach a higher anti-CEA capture aptamer onto the sensor surface through a chemical linker, and then, CEA was quantified by the aptamer. Furthermore, CEA-spiked serum was tested by using the immobilized aptamer, which was found to not affect the target validation. The limit of detection for CEA in PBS and serum is calculated from a linear regression graph to be 0.5 ng/mL with R2 values of 0.9593 and 0.9657, respectively, over a linear range from 0.5 to 500 ng/mL. This CEA quantification by the aptasensor can help diagnose various surgical tumors and monitor their progression. [ABSTRACT FROM AUTHOR]

17β‐Estradiol‐E2 (17β‐E2) is a steroid hormone that plays a major role in the reproductive endocrine system and is involved in various processes, such as pregnancy, fertility, and menopause. In this study, the performance of an enzyme‐linked immunosorbent assay (ELISA) for 17β‐E2 quantification was enhanced by using a gold nanoparticle (GNP)‐conjugated aptamer. An anti‐17β‐E2–aptamer–GNP antibody was immobilized on an amine‐modified ELISA surface. Then, 17β‐E2 was allowed to interact with and be sandwiched by antibodies. Aptamer–GNP conjugation was confirmed by colorimetric assays via the naked eye and UV–visible light spectroscopy. The detection limit based on a signal‐to‐noise ratio (S/N) of 3 was estimated to be 1.5 nM (400 pg/mL), and the linear range was 1.5–50 nM. Control experiments (without 17β‐E2/with a complementary aptamer sequence/with a nonimmune antibody) confirmed the specific detection of 17β‐E2. Moreover, 17β‐E2 spiking of human serum did not interrupt the interaction between 17β‐E2 and its antibody and aptamer. Thus, the developed ELISA can be used as an alternate assay for quantification of 17β‐E2 and assessment of endocrine‐related gynecological problems. [ABSTRACT FROM AUTHOR]

This article describes a sensitive impedimetric method for the determination of human blood coagulation factor IX protein (FIX) which is present in extremely low concentration in serum. An interdigitated electrode (IDE) whose surface was layered with zinc oxide was modified with two kinds of probes. One is an antibody, the other an aptamer against FIX. A comparative study between anti-FIX aptamer and anti-FIX antibody showed the aptamer to possess higher affinity for FIX. A sandwich aptamer assay was worked out by using the FIX-binding aptamer on the surface of the IDE. It has a detection limit as low as 10 pM which makes it 4 to 30-fold more sensitive than any other method reported for FIX. Moreover, to practice detection in clinical samples, FIX was detected from the human blood serum by spiking. In our perception, the sensitivity of the ZnO-modified IDE presented here makes it a promising tool for sensing clinically relevant analytes that are present in very low (sub-pM) concentrations. [ABSTRACT FROM AUTHOR]

Aptamers are single-stranded nucleic acids or peptides identified from a randomized combinatorial library through specific interaction with the target of interest. Targets can be of any size, from small molecules to whole cells, attesting to the versatility of aptamers for binding a wide range of targets. Aptamers show drug properties that are analogous to antibodies, with high specificity and affinity to their target molecules. Aptamers can penetrate disease-causing microbial and mammalian cells. Generated aptamers that target surface biomarkers act as cell-targeting agents and intracellular delivery vehicles. Within this context, the 'cell-internalizing aptamers' are widely investigated via the process of cell uptake with selective binding during in vivo systematic evolution of ligands by exponential enrichment (SELEX) or by cell-internalization SELEX, which targets cell surface antigens to be receptors. These internalizing aptamers are highly preferable for the localization and functional analyses of multiple targets. In this overview, we discuss the ways by which internalizing aptamers are generated and their successful applications. Furthermore, theranostic approaches featuring cell-internalized aptamers are discussed with the purpose of analyzing and diagnosing disease-causing pathogens. [ABSTRACT FROM AUTHOR]

Aptamers are single-stranded oligonucleotides that can be artificially generated by a method called Systematic evolution of ligands by exponential enrichment (SELEX). The generated aptamers have been assessed for high-performance sensing applications due to their appealing characteristics. With either aptamers alone or complementing with antibodies, several high sensitive and portable sensors have been demonstrated for use in ‘point-of-care testing’. Due to their high suitability and flexibility, aptamers are conjugated with nanostructures and utilized in field applications. Moreover, aptamers are more amenable to chemical modifications, making them capable of utilization with most developed sensors. In this overview, we discuss novel, portable, and aptamer-based sensing strategies that are suitable for ‘point-of-care testing’. [ABSTRACT FROM AUTHOR]