scholarly journals Porous Silicon-Based Aptasensors: The Next Generation of Label-Free Devices for Health Monitoring

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2216 ◽  
Author(s):  
Monica Terracciano ◽  
Ilaria Rea ◽  
Nicola Borbone ◽  
Rosalba Moretta ◽  
Giorgia Oliviero ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Porous Silicon ◽  
Limit Of Detection ◽  
Combinatorial Libraries ◽  
High Sensitivity ◽  
Label Free ◽  
Great Specificity ◽  
Silicon Based ◽  
Exponential Enrichment

Aptamers are artificial nucleic acid ligands identified and obtained from combinatorial libraries of synthetic nucleic acids through the in vitro process SELEX (systematic evolution of ligands by exponential enrichment). Aptamers are able to bind an ample range of non-nucleic acid targets with great specificity and affinity. Devices based on aptamers as bio-recognition elements open up a new generation of biosensors called aptasensors. This review focuses on some recent achievements in the design of advanced label-free optical aptasensors using porous silicon (PSi) as a transducer surface for the detection of pathogenic microorganisms and diagnostic molecules with high sensitivity, reliability and low limit of detection (LoD).

scholarly journals Implementation of High-Throughput Sequencing (HTS) in Aptamer Selection Technology

2020 ◽  
Vol 21 (22) ◽  
pp. 8774
Author(s):  
Natalia Komarova ◽  
Daria Barkova ◽  
Alexander Kuznetsov
Keyword(s):  
Nucleic Acid ◽  
High Throughput ◽  
High Throughput Sequencing ◽  
Combinatorial Libraries ◽  
Structure And Function ◽  
Huge Number ◽  
Systematic Evolution ◽  
And Function ◽  
Exponential Enrichment

Aptamers are nucleic acid ligands that bind specifically to a target of interest. Aptamers have gained in popularity due to their high potential for different applications in analysis, diagnostics, and therapeutics. The procedure called systematic evolution of ligands by exponential enrichment (SELEX) is used for aptamer isolation from large nucleic acid combinatorial libraries. The huge number of unique sequences implemented in the in vitro evolution in the SELEX process imposes the necessity of performing extensive sequencing of the selected nucleic acid pools. High-throughput sequencing (HTS) meets this demand of SELEX. Analysis of the data obtained from sequencing of the libraries produced during and after aptamer isolation provides an informative basis for precise aptamer identification and for examining the structure and function of nucleic acid ligands. This review discusses the technical aspects and the potential of the integration of HTS with SELEX.

scholarly journals Label-Free Split Aptamer Sensor for Femtomolar Detection of Dopamine by Means of Flexible Organic Electrochemical Transistors

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2577 ◽  
Author(s):  
Yuanying Liang ◽  
Ting Guo ◽  
Lei Zhou ◽  
Andreas Offenhäusser ◽  
Dirk Mayer
Keyword(s):  
Detection Limit ◽  
Electrochemical Sensors ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Label Free ◽  
Dopamine Detection ◽  
Electrochemical Transistor ◽  
Sensitivity And Selectivity

The detection of chemical messenger molecules, such as neurotransmitters in nervous systems, demands high sensitivity to measure small variations, selectivity to eliminate interferences from analogues, and compliant devices to be minimally invasive to soft tissue. Here, an organic electrochemical transistor (OECT) embedded in a flexible polyimide substrate is utilized as transducer to realize a highly sensitive dopamine aptasensor. A split aptamer is tethered to a gold gate electrode and the analyte binding can be detected optionally either via an amperometric or a potentiometric transducer principle. The amperometric sensor can detect dopamine with a limit of detection of 1 μM, while the novel flexible OECT-based biosensor exhibits an ultralow detection limit down to the concentration of 0.5 fM, which is lower than all previously reported electrochemical sensors for dopamine detection. The low detection limit can be attributed to the intrinsic amplification properties of OECTs. Furthermore, a significant response to dopamine inputs among interfering analogues hallmarks the selective detection capabilities of this sensor. The high sensitivity and selectivity, as well as the flexible properties of the OECT-based aptasensor, are promising features for their integration in neuronal probes for the in vitro or in vivo detection of neurochemical signals.

scholarly journals PfHRP2 detection using plasmonic optrodes: performance analysis

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Médéric Loyez ◽  
Mathilde Wells ◽  
Stéphanie Hambÿe ◽  
François Hubinon ◽  
Bertrand Blankert ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Limit Of Detection ◽  
Fiber Surface ◽  
Malaria Diagnosis ◽  
High Sensitivity ◽  
Cost Effective ◽  
Label Free ◽  
Multiple Receptors ◽  
Label Free Detection

Abstract Background Early malaria diagnosis and its profiling require the development of new sensing platforms enabling rapid and early analysis of parasites in blood or saliva, aside the widespread rapid diagnostic tests (RDTs). Methods This study shows the performance of a cost-effective optical fiber-based solution to target the presence of Plasmodium falciparum histidine-rich protein 2 (PfHRP2). Unclad multimode optical fiber probes are coated with a thin gold film to excite Surface Plasmon Resonance (SPR) yielding high sensitivity to bio-interactions between targets and bioreceptors grafted on the metal surface. Results Their performances are presented in laboratory conditions using PBS spiked with growing concentrations of purified target proteins and within in vitro cultures. Two probe configurations are studied through label-free detection and amplification using secondary antibodies to show the possibility to lower the intrisic limit of detection. Conclusions As malaria hits millions of people worldwide, the improvement and multiplexing of this optical fiber technique can be of great interest, especially for a future purpose of using multiple receptors on the fiber surface or several coated-nanoparticles as amplifiers.

scholarly journals Hybrid-Type SELEX for the Selection of Artificial Nucleic Acid Aptamers Exhibiting Cell Internalization Activity

Pharmaceutics ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 888
Author(s):  
Hiro Uemachi ◽  
Yuuya Kasahara ◽  
Keisuke Tanaka ◽  
Takumi Okuda ◽  
Yoshihiro Yoneda ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Surface Protein ◽  
Functional Screening ◽  
Nucleic Acid Aptamers ◽  
Hybrid Type ◽  
Cell Internalization ◽  
Promising Target ◽  
A Cell ◽  
Exponential Enrichment

Nucleic acid aptamers have attracted considerable attention as next-generation pharmaceutical agents and delivery vehicles for small molecule drugs and therapeutic oligonucleotides. Chemical modification is an effective approach for improving the functionality of aptamers. However, the process of selecting appropriately modified aptamers is laborious because of many possible modification patterns. Here, we describe a hybrid-type systematic evolution of ligands by exponential enrichment (SELEX) approach for the generation of the artificial nucleic acid aptamers effective against human TROP2, a cell surface protein identified by drug discovery as a promising target for cancer therapy. Capillary electrophoresis SELEX was used for the pre-screening of multiple modified nucleic acid libraries and enrichment of TROP2 binding aptamers in the first step, followed by functional screening using cell-SELEX in the second step for the generation of cell-internalizing aptamers. One representative aptamer, Tac-B1, had a nanomolar-level affinity to human TROP2 and exhibited elevated capacity for internalization by cells. Because of the growing interest in the application of aptamers for drug delivery, our hybrid selection approach has great potential for the generation of functional artificial nucleic acid aptamers with ideal modification patterns in vitro.

TOWARDS SENSING SINGLE OR A FEW BIO-MOLECULAR ARCHITECTURES: DESIGN OF FUNCTIONAL SURFACES

2008 ◽  
Vol 18 (01) ◽  
pp. 187-194
Author(s):  
PEIJI ZHAO ◽  
DWIGHT WOOLARD ◽  
JORGE M. SEMINARIO ◽  
ROBERT TREW
Keyword(s):  
Density Functional ◽  
High Sensitivity ◽  
Lower Sensitivity ◽  
Label Free ◽  
Dna Molecules ◽  
Surface Attachment ◽  
Biomolecular Sensing ◽  
Aromatic Molecules ◽  
Electrical Sensing ◽  
Silicon Based

There is considerable interest in electrical sensing of biomolecular binding since it has the potential to be label free, to work easily in aqueous environments native to the biomolecules, and to be integrated with small, fast, and inexpensive microelectronoics as detection instrumentation. Although electrochemical methods have been used successfully in detections of DNA molecules with Ag labels at very high sensitivity (~ p ml), detection of DNA molecules in terms of label free techniques has a lower sensitivity (~ μ ml). Here, the surface attachment chemistry is critical towards the detection of ultra-low concentration of biomolecules. In this article, based on density functional theory, we have calculated and analyzed the electrical characteristics of the contact between aromatic molecules and silicon (100) − 2×1 surfaces. Design principles for silicon based electrodes of electrochemically biomolecular sensing instruments for label-free sensing of single or a few biomolecular molecules have also been discussed.

scholarly journals Development of PCR, LAMP and qPCR Assays for the Detection of Aflatoxigenic Strains of Aspergillus flavus and A. parasiticus in Hazelnut

Toxins ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 757
Author(s):  
Sara Franco Ortega ◽  
Ilenia Siciliano ◽  
Simona Prencipe ◽  
Maria Lodovica Gullino ◽  
Davide Spadaro
Keyword(s):  
Food Safety ◽  
Real Time ◽  
Aspergillus Flavus ◽  
Real Time Pcr ◽  
Limit Of Detection ◽  
Screening Method ◽  
Lamp Assay ◽  
High Sensitivity ◽  
Isothermal Amplification

Aspergillus flavus and A. parasiticus are two species able to produce aflatoxins in foodstuffs, and in particular in hazelnuts, at harvest and during postharvest phase. As not all the strains of these species are aflatoxin producers, it is necessary to develop techniques that can detect aflatoxigenic from not aflatoxigenic strains. Two assays, a LAMP (loop-mediated isothermal amplification) and a real time PCR with TaqMan® probe were designed and validated in terms of specificity, sensitivity, reproducibility, and repeatability. The capability of the strains to produce aflatoxins was measured in vitro and both assays showed to be specific for the aflatoxigenic strains of A. flavus and A. parasiticus. The limit of detection of the LAMP assay was 100–999 picograms of DNA, while the qPCR detected 160 femtograms of DNA in hazelnuts. Both techniques were validated using artificially inoculated hazelnuts and naturally infected hazelnuts. The qPCR was able to detect as few as eight cells of aflatoxigenic Aspergillus in naturally infected hazelnut. The combination of the LAMP assay, which can be performed in less than an hour, as screening method, with the high sensitivity of the qPCR, as confirmation assay, is able to detect aflatoxigenic strains already in field, helping to preserve the food safety of hazelnuts.

scholarly journals Rapid label-free SERS detection of foodborne pathogenic bacteria based on hafnium ditelluride-Au nanocomposites

2020 ◽  
Vol 13 (05) ◽  
pp. 2041004 ◽  
Author(s):  
Yang Li ◽  
Yanxian Guo ◽  
Binggang Ye ◽  
Zhengfei Zhuang ◽  
Peilin Lan ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Limit Of Detection ◽  
Principal Component ◽  
High Sensitivity ◽  
Chemical Mechanism ◽  
Sers Substrate ◽  
Label Free ◽  
Label Free Detection ◽  
Surface Enhanced Raman ◽  
Foodborne Pathogenic Bacteria

Two-dimensional (2D) nanomaterials have captured an increasing attention in biophotonics owing to their excellent optical features. Herein, 2D hafnium ditelluride (HfTe[Formula: see text], a new member of transition metal tellurides, is exploited to support gold nanoparticles fabricating HfTe2-Au nanocomposites. The nanohybrids can serve as novel 2D surface-enhanced Raman scattering (SERS) substrate for the label-free detection of analyte with high sensitivity and reproducibility. Chemical mechanism originated from HfTe2 nanosheets and the electromagnetic enhancement induced by the hot spots on the nanohybrids may largely contribute to the superior SERS effect of HfTe2-Au nanocomposites. Finally, HfTe2-Au nanocomposites are utilized for the label-free SERS analysis of foodborne pathogenic bacteria, which realize the rapid and ultrasensitive Raman test of Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella with the limit of detection of 10 CFU/mL and the maximum Raman enhancement factor up to [Formula: see text]. Combined with principal component analysis, HfTe2-Au-based SERS analysis also completes the bacterial classification without extra treatment.

scholarly journals 1832. Development of an Ultrasensitive Field-Applicable Plasmodium falciparum Assay for Malaria Diagnosis and Eradication

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S42-S43
Author(s):  
Rose Lee ◽  
Helena De Puig Guixe ◽  
Jeffrey Dvorin ◽  
James Collins
Keyword(s):  
Plasmodium Falciparum ◽  
Nucleic Acid ◽  
Genomic Dna ◽  
Limit Of Detection ◽  
Malaria Diagnosis ◽  
High Sensitivity ◽  
Nucleic Acid Detection ◽  
One Pot ◽  
Minimal Sample ◽  
Isothermal Assay

Abstract Background Malaria control and eradication have been hampered by asymptomatic carriage which serves as a parasite reservoir. Low-density infections (< 100 parasites/microliter) frequently fall below the limit of detection (LOD) of microscopy and rapid diagnostic tests (RDT) which are antigen-based tests. Molecular methods such as polymerase chain reaction are capable of higher sensitivity yet remain impractical for resource-limited settings. We describe development of an isothermal assay using the nucleic acid detection platform SHERLOCK (Specific High-Sensitivity Enzymatic Reporter UnLOCKing), which may also be increasingly important as there has been rising detection of histidine-rich protein 2 (HRP2) gene deletions in Plasmodium spp. HRP2 is the most commonly used antigen in RDTs and deletion of this gene would render many RDTs obsolete. Methods SHERLOCK leverages the endonucleases of CRISPR-associated microbial adaptive immunity. Cas12a is an RNA-guided, DNA-cleaving enzyme, which can be programmed with guide RNAs to cleave nontarget reporter ssDNA. We exploit the nonspecific degradation of labeled ssDNA to detect the presence of the dsDNA target that activated Cas12a (Figure 1). Recombinase polymerase amplification (RPA) coupled with Cas12a detection enables a lower LOD. Plasmodium falciparum whole genomic DNA was compared with parasites cultured in red blood cells (RBCs) with known parasitemia and boiled at 95°C for 5 minutes for lysis of RBCs/parasites then diluted 1:2.5 to prevent solidification. Results This SHERLOCK assay detected simulated Plasmodium falciparum infection at attomolar LODs when applied to whole genomic DNA and simulated samples of infected RBCs spiked into whole blood. The genomic assay detected down to 0.2 parasites/microliter and the simulated sample detected to 10 parasites/microliter in the final reaction volume. In comparison, LODs from the initial input volume was 5aM and 250aM, respectively (Figure 2). Conclusion We demonstrate an isothermal nucleic acid detection platform capable of diagnosis in 60 minutes in a one-pot assay requiring minimal sample preparation and reaching an LOD recommended by the WHO for malaria eradication. In summary, we illustrate the utility of the SHERLOCK platform in application to malaria and global health. Disclosures All Authors: No reported Disclosures.

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