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Breast cancer has been reported to be high in its incidence with women, and early identification of breast cancer helps to improve and provide an effective treatment. Tumor markers are active substances; in particular, human epidermal growth factor receptor 2 (HER2) is over‐expressed at the level of 20%–30%. This research work developed a highly sensitive HER2 biosensor on the interdigitated electrode (IDE) by using aptamer as a detection probe. To enhance the analytical performances, aptamer was attached to the gold nanoparticle and immobilized on the IDE through a chemical linker [(3‐aminopropyl)triethoxysilane]. On the aptamer conjugation, HER2 was quantified through current‐volt measurements, and the limit of detection of HER2 was calculated as 1 pg/mL on a linear range from 0.1 to 3000 pg/mL at an R2 (regression coefficient) of 0.9657. Further, a selective performance with human serum increased the current responses by increasing HER2 concentrations. Specific experiments with control protein and complementary aptamer sequence failed to enhance the current responses. This HER2 biosensor reflects the occurrence of breast cancer at its lower abundance and helps to identify the associated complications. [ABSTRACT FROM AUTHOR]

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]

This research is focussed to quantify IGF1 by electroanalytical analysis on InterDigitated electrode surface and characterized by the microscopic observations. For the detection, antibody and aptamer were used to analyze the level of IGF1. The sandwich pattern (aptamer-IGF1-antibody) was designed on the chemically modified IDE surface and reached the limit of detection to 10 fM with 100 folds enhancement in the sensitivity. Different control experiments (absence of IGF1, binding with IGF2 and with non-complementary aptamer) were failed to show the current changes, discriminated the specific detection. A good detection strategy is to complement the currently following imaging systems for AAA. [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]

A new zeolite-iron oxide nanocomposite (ZEO-IO) was extracted from waste fly ash of a thermal power plant and utilized for capturing aptamers used to quantify the myocardial infarction (MI) biomarker N-terminal prohormone B-type natriuretic peptide (NT-ProBNP); this was used in a probe with an integrated microelectrode sensor. High-resolution microscopy revealed that ZEO-IO displayed a clubbell structure and a particle size range of 100–200 nm. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of Si, Al, Fe, and O in the synthesized ZEO-IO. The limit of detection for NT-ProBNP was 1–2 pg/mL (0.1–0.2 pM) when the aptamer was sandwiched with antibody and showed the doubled current response even at a low NT-ProBNP abundance. A dose-dependent interaction was identified for this sandwich with a linear plot in the concentration range 1 to 32 pg/mL (0.1–3.2 pM) with a determination coefficient R2 = 0.9884; y = 0.8425x–0.5771. Without sandwich, the detection limit was 2–4 pg/mL (0.2–0.4 pM) and the determination coefficient was R2 = 0.9854; y = 1.0996x–1.4729. Stability and nonfouling assays in the presence of bovine serum albumin, cardiac troponin I, and myoglobin revealed that the aptamer-modified surface is stable and specific for NT-Pro-BNP. Moreover, NT-ProBNP-spiked human serum exhibited selective detection. This new nanocomposite-modified surface helps in detecting NT-Pro-BNP and diagnosing MI at stages of low expression. [ABSTRACT FROM AUTHOR]

Abdominal aortic aneurysm (AAA) is a bulge in the abdominal aorta and cause high mortality and morbidity due to the unbalanced condition with haemostasis. AAA has been found with the diameter of 5.5 cm/lager needs a surgical treatment; otherwise, it ruptures with the excessive bleeding. Aneurysm infiltrating macrophage is located in the site of damaged tissue and actively expresses matrix metalloproteinase-9 (MMP-9). MMP-9 is highly correlated with increasing diameter of aneurysm. This research work was designed to detect MMP-9 level on interdigitated electrode (IDE) sensing system to identify the condition of AAA. Specifically, selected aptamer against MMP-9 was utilized as the probe to detect MMP-9 on IDE. MMP-9 detection was enhanced by modifying the surface of IDE with multiwalled carbon nanotube conjugated aptamer through the amine linker. On the linear range between 1 and 60 pM, the limit of detection was at 2 pM with the linear regression (y = 0.2579x + 0.0246; R2 = 0.9477). In addition, spiking of MMP-9 in human serum did not interfere the detection with the IDE designed. [ABSTRACT FROM AUTHOR]

Prostate cancer is a leading health burden, the third most common cancer in a man. High accuracy detection and screening methods with a suitable biomarker can significantly reduce the risk of mortality. Prostate specific antigen (PSA) is the efficient and acceptable biomarker due to its level of increment in the biological fluid with the prostate cancer patient. This research was focused to establish a sensitive method of PSA detection by using gold nanoparticle (GNP) conjugated PSA specific aptamer on interdigitated mini-electrode. GNP allowed to capture higher number of aptamers on the surface and enhanced the interaction of PSA. This good detection method can determine PSA at 45 aM with the sensitivity of 30 aM. A linear range was noticed from 60 until 2000 aM on the regression curve at y = 0. 1 5 6 8 x + 0. 1 4 3 ; R 2 = 0. 9 5 5. Moreover, spiking PSA in human serum enhances the current response with increasing PSA concentrations. This method of determination helps to quantify the PSA level and diagnose the prostate cancer at different stages. This study uses the properly fabricated interdigitated mini-electrode for identifying the prostate specific antigen. Aptamer has been used as the probe and numbers of aptamer immobilization enhanced by gold nanoparticle conjugation. To minimize the biofouling, PEGylated metal oxide was layered on the sensing surface. By using this set-up, the sensitivity and limit of detection were attained at attomolar range with higher selectivity. [ABSTRACT FROM AUTHOR]

Cancer is the uncontrollable abnormal division of cell growth, caused due to the varied reasons. Cancer can be expressed in any part of the body, and it is one of the death-causing diseases. Human reproductive organs are commonly damaged by cancer. In particular, the women reproductive system is affected by various cancers including ovarian, cervical, endometrial, vaginal, fallopian tube, and vulvar cancers. Identifying these cancers at earlier stages prevents the damage to the organs. Aptamer is the potential probe that can identify these cancers. Aptamer is an artificial antibody selected from the randomized library of molecules and has a high binding affinity to the target biomarker. Targeting cancers in the reproductive organs using aptamers showed an excellent efficiency of detection compared to other probes. Different aptamers have been generated against the gynaecological cancer biomarkers, which include HE4, CA125, VEGF, OCCA (for ovarian cancer), EGFR, FGFR1, K-ras (for endometrial cancer), HPV E-16, HPV E-7, HPV E-6, tyrosine, and kinase (for cervical cancer), which help to identify the cancers in woman reproductive organs. In this overview, the biomarkers for gynecologic cancers and the relevant diagnosing systems generated using the specific aptamers are discussed. Furthermore, the therapeutic applications of aptamer with gynaecological cancers are narrated. [ABSTRACT FROM AUTHOR]

An evanescent-field-coupled waveguide-mode (EFC-WM) sensor utilizes monolithic SiO2/Si/SiO2 sensing plates having a multilayered structure and is used to evaluate a blocking agent comprising poly(ethylene glycol)-based block copolymers. Factor IX (FIX) protein was detected using its aptamer, viz. FIX was immobilized on a glutaraldehyde-modified silica surface, and then treated with a biotinylated aptamer. The quantitative analysis of FIX was carried out using streptavidin-conjugated gold nanoparticles (SA-GNPs). The blocking polymer, poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAAc), was found to mask unreacted amine and glutaraldehyde (Glu) moieties on the SiO2 surface, and it completely prevented the non-specific binding of SA-GNPs. By exploiting the strong blocking effect of PEG-b-PAAc, we achieved high ligand–analyte interaction sensitivity (sensitive down to 100 pM). To improve the sensitivity further, we also used pentaethylenehexamine-terminated PEG (N6-PEG) on GNPs. The improvement in sensitivity was found to be 1000-fold (to 100 fM), which was substantiated by the observation of higher numbers of GNPs on the sensing surface in the results of the scanning electron microscopic examination. Based on the competition assay of free biotin premixed with SA-GNPs, it was concluded that some active biotin-binding sites on the streptavidin were blocked by N6-PEG, which improved the binding ability to the biotinylated sensing surface. An optimum number of binding sites on the SA-GNPs might improve their binding affinity. The strategy shown with dual polymers, viz. blocking of the sensor chip surface and coating of SA-GNPs, is recommended for developing sensors with higher sensitivity and reliability. Selective binding of the aptamer to a very small amount of FIX in the mixed sample containing FXIa and FVIIa, or albumin, makes this the optimal strategy for detecting a FIX deficiency in human blood samples. [ABSTRACT FROM AUTHOR]

The ectodomain of the gD protein of herpes simplex viruses (HSVs) plays an important role in viral entry by binding to specific cellular coreceptors and mediating viral entry to the host cells. In the present study, we isolated RNA aptamers (aptamer-1 and aptamer-5) that specifically bind to the gD protein of HSV-1 with high affinity and are able to discriminate the gD protein of a different virus, HSV-2. Aptamer-1 efficiently interfered with the interaction between the gD protein and the HSV-1 target cell receptor (HVEM) in a dose-dependent manner. The 50% effective concentration (EC50) of aptamer-1 was estimated to be in the nanomolar range (60 nM). Furthermore, aptamer-1 was analyzed for anti-HSV-1 activity by using plaque assays, and it efficiently inhibited viral entry with an estimated Kt of 0.8 µΜ. To expand the future applications of aptamer-1, a shorter variant was designed by using both mapping and boundary analyses, resulting in the mini-1 aptamer (44-mer). Compared to the fulllength aptamer, mini-1 had at least as high an affinity, specificity, and ability to interfere with gD-HVEM interactions. These studies suggest that the mini-1 aptamer could be explored further as an anti-HSV-1 topical therapy designed to prevent the risk of acquiring HSV-1 infection through physical contact. [ABSTRACT FROM AUTHOR]

Thesystematic evolution of ligands by exponential enrichment (SELEX)is a selection process for identifying high-affinity selective moleculesfrom a randomized combinatorial nucleic acid library against a widerange of target molecules. Using a pool of N25 RNA molecules, theSELEX process was performed against two targets from influenza viruses,namely, intact influenza B/Tokio/53/99 and hemagglutinin of infuluenzaB Jilin/20/2003. The selection processes were evaluated by surfaceplasmon fluorescence spectroscopy (SPFS), and the result was comparedto that obtained by a conventional radioisotope method. Clear discriminationamong different selection cycles was displayed by SPFS, indicatingthat this method can be used as an alternative method of radioisotopelabeling. The dissociation constant of the selected aptamers againstthe targets was in the low nanomolar range. The sensitivity of theselected aptamer against intact influenza B/Tokio/53/99 to detectthe influenza virus was the low ng/mL level, an approximately 250-foldhigher sensitivity than that of the commercially obtained antibody.The target binding sites on the aptamer were predicted by mappinganalyses. The selected aptamer could discriminate other influenzastrains, and the sensitivity of the selected aptamer was further confirmedby gold-nanoparticle-based sensing on a waveguide-mode sensor. Thisfinding demonstrates that the selected aptamer would be useful fordetecting influenza viruses at an early stage of infection and forthe purpose of influenza surveillance. [ABSTRACT FROM AUTHOR]

Aptamers are ssDNA or RNA that binds to wide variety of target molecules with high affinity and specificity produced by systematic evolution of ligands by exponential enrichment (SELEX). Compared to RNA aptamer, DNA aptamer is much more stable, favourable to be used in many applications. The most critical step in DNA SELEX experiment is the conversion of dsDNA to ssDNA. The purpose of this study was to develop an economic and efficient approach of generating ssDNA by using asymmetric PCR. Our results showed that primer ratio (sense primer:antisense primer) of 20:1 and sense primer amount of 10 to 100 pmol, up to 20 PCR cycles using 20 ng of initial template, in combination with polyacrylamide gel electrophoresis, were the optimal conditions for generating good quality and quantity of ssDNA. The generation of ssDNA via this approach can greatly enhance the success rate of DNA aptamer generation. [ABSTRACT FROM AUTHOR]