Primary Aptamer Research Articles

Development of Aptamer-Functionalized Gold Nanoparticles as Probes in Point-of-Care Diagnostic Device for Rapid Detection of Multidrug-Resistant Bacteria in Bombyx mori L. .

The sericulture industry suffers severe crop losses due to various silkworm diseases, necessitating the development of further technologies for rapid pathogen detection. Here, we report an all-in-one portable biosensor that combines conjugated gold nanoparticles (Au NPs) with an aptamer-based lateral flow assay (LFA) platform for the real-time analysis of Mammaliicoccus sp. and Pseudomonas sp. Our platform enables sample-to-answer naked eye detection within 5 min without any cross-reactivity with other representatives of the silkworm pathogenic bacterial group. This assay was based on the sandwich-type format using a bacteria-specific primary aptamer (Apt1) conjugated with 23 nm ± 1.27 nm Au NPs as a signal probe and another bacteria-specific secondary aptamer (Apt2)-coated nitrocellulose membrane as a capture probe. The hybridization between the signal probe and the capture probe in the presence of bacteria develops a red band in the test line, whose intensity is directly proportional to the bacterial concentration. Under the optimal experimental conditions, the visual limit of detection of the strip for Mammaliicoccus sp. and Pseudomonas sp. was 1.5 × 104 CFU/mL and 1.5 × 103 CFU/mL, respectively. Additionally, the performance of the LFA device was validated by using a colorimetric assay, and the results from the colorimetric assay are consistent with those obtained from the LFA. Our findings indicate that the developed point-of-care diagnostic device has significant potential for providing a cost-effective, scalable alternative for the rapid detection of silkworm pathogens.

Sandwich-type supersensitive electrochemical aptasensor of glypican-3 based on PrGO-Hemin-PdNP and AuNP@PoPD.

Anew sandwich-type electrochemical biosensing platform was developed by gold @polyphthalenediamine nanohybrids (AuNP@PoPD) as the sensing platform and phosphorus doped reduced graphene oxide-hemin-palladium nanoparticles (PrGO-Hemin-PdNP) as the signal amplifierfor phosphatidylinositol proteoglycan 3 (GPC3).AuNP@PoPD, co-electrodeposited into the screen printed electrode with high conductivity and stability, is dedicated to assembling the primary GPC3 aptamer (GPC3Apt). The second GPC3Apt immobilized on the high conductivity and large surface area of PrGO-Hemin-PdNP was utilized as an electrochemical signal reporter by hemin oxidation (PrGO-Hemin-PdNP-GPC3Apt). In the range 0.001-10.0ng/mL, the hemin oxidation current signal of the electrochemical aptasensor increased log-linearly with the concentration of GPC3, the lowest detection limit was 0.13pg/mL, and the sensitivity was 2.073 μA/μM/cm2. Theaptasensor exhibited good sensing performance in a human serum samplewith the relative error of 4.31-8.07%. The sandwich sensor showed good selectivity and stability for detection GPC3 in human serum samples, providing a new efficient and sensitive method for detecting HCC markers.

An aptamer-based sandwich assay for detection of alpha-defensin human neutrophil protein 1 on a microfluidic platform.

The diagnosis of periprosthetic joint infection (PJI) remains a labor-intensive and challenging issue, with life-threatening complications associated with misdiagnoses. Superior diagnostic approaches are therefore urgently needed, and synovial biomarkers are gaining substantial attention in this capacity. A new aptamer-based sandwich assay was developed where the aptamer probes specific to one such biomarker, alpha-defensin human neutrophil protein 1 (HNP 1), was integrated herein into a new microfluidic platform. The magnetic beads coated with the primary aptamer probe were able to bind the target protein with high affinity and high specificity in synovial fluid and a fluorescent-labelled secondary aptamer were further used to quantify HNP 1 in a sandwich approach. Up to four clinical samples with low volume (∼50μL each) in a much faster assay including detection within <60min with 100% accuracy (with totally 13 clinical samples without the need of sample pretreatment) through the use of the aptamer-based sandwich assay were automatically detected on a single chip. The wide dynamic range of this compact device, 0.5-100mg/L, highlights its utility for future PJI diagnostics in the clinic.

An ultrasensitive electrochemical aptasensor using Tyramide-assisted enzyme multiplication for the detection of Staphylococcus aureus

In this study, we aimed to introduce a new electrochemical aptasensor based on the tyramide signal amplification (TSA) technology for a highly-sensitive detection of the pathogenic bacterium, Staphylococcus aureus, as a model of foodborne pathogens. In this aptasensor, the primary aptamer, SA37, was used to specifically capture bacterial cells; the secondary aptamer, SA81@HRP, was used as the catalytic probe; and a TSA-based signal enhancement system comprising of biotinyl-tyramide and streptavidin-HRP as electrocatalytic signal tags was adopted to fabricate the sensor and improve the detection sensitivity. S. aureus cells were selected as the pathogenic bacteria to verify the analytical performance of this TSA-based signal-enhancement electrochemical aptasensor platform. After the simultaneous binding of SA37-S. aureus-SA81@HRP formed on the gold electrode, thousands of @HRP molecules could be bound onto the biotynyl tyramide (TB) displayed on the bacterial cell surface through a catalytic reaction between HRP and H2O2, resulting in the generation of the highly amplified signals mediated by HRP reactions. This developed aptasensor could detect S. aureus bacterial cells at an ultra-low concentration, with a limit of detection (LOD) of 3 CFU/mL in buffer. Furthermore, this chronoamperometry aptasensor successfully detected target cells in both tap water and beef broth with LOD to be 8 CFU/mL, which are very high sensitivity and specificity. Overall, this electrochemical aptasensor using TSA-based signal-enhancement could be a very useful tool for the ultrasensitive detection of foodborne pathogens in food and water safety and environmental monitoring.

Rapid Nanoplasmonic-Enhanced Detection of SARS-CoV-2 and Variants on DNA Aptamer Metasurfaces

Since the discovery of coronavirus disease 2019 (COVID-19) in December 2019, it has been mainly diagnosed with quantitative reverse transcription polymerase chain reaction (PCR) of nasal swabs in clinics. A very sensitive and rapid detection technique using easily collected fluids such as saliva is needed for safer and more practical, precise mass testing. Here, we introduce a computationally screened gold-nanopatterned metasurface platform out of a pattern space of 2 100 combinations for strongly enhanced light–virus interaction using a genetic algorithm and apply them to investigate the presence and concentration of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In our approach, the gold metasurface with the nanopattern that provides the highest plasmonic enhancement is modified with the primary DNA aptamer for COVID-19 sensing from unprocessed saliva. A fluorescently tagged secondary aptamer was used to bind the virus that was then captured on the surface with the primary aptamer. By incorporating machine learning to identify the virus from Raman spectra, we achieved 95.2% sensitivity and specificity on 36 SARS-CoV-2 PCR-positive and 33 SARS-CoV-2 PCR-negative samples collected in the clinics. In addition, we demonstrated that our nanoplasmonic aptasensor could distinguish wild-type, Alpha, and Beta variants through the machine learning analysis of their spectra. Our results may help pave the way for effective, safe, and quantitative preventive screening and identification of variants.

Model of the SARS-CoV-2 Virus for Development of a DNA-Modified, Surface-Enhanced Raman Spectroscopy Sensor with a Novel Hybrid Plasmonic Platform in Sandwich Mode.

The recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has posed a great challenge for the development of ultra-fast methods for virus identification based on sensor principles. We created a structure modeling surface and size of the SARS-CoV-2 virus and used it in comparison with the standard antigen SARS-CoV-2—the receptor-binding domain (RBD) of the S-protein of the envelope of the SARS-CoV-2 virus from the Wuhan strain—for the development of detection of coronaviruses using a DNA-modified, surface-enhanced Raman scattering (SERS)-based aptasensor in sandwich mode: a primary aptamer attached to the plasmonic surface—RBD-covered Ag nanoparticle—the Cy3-labeled secondary aptamer. Fabricated novel hybrid plasmonic structures based on “Ag mirror-SiO2-nanostructured Ag” demonstrate sensitivity for the detection of investigated analytes due to the combination of localized surface plasmons in nanostructured silver surface and the gap surface plasmons in a thin dielectric layer of SiO2 between silver layers. A specific SERS signal has been obtained from SERS-active compounds with RBD-specific DNA aptamers that selectively bind to the S protein of synthetic virion (dissociation constants of DNA-aptamer complexes with protein in the range of 10 nM). The purpose of the study is to systematically analyze the combination of components in an aptamer-based sandwich system. A developed virus size simulating silver particles adsorbed on an aptamer-coated sensor provided a signal different from free RBD. The data obtained are consistent with the theory of signal amplification depending on the distance of the active compound from the amplifying surface and the nature of such a compound. The ability to detect the target virus due to specific interaction with such DNA is quantitatively controlled by the degree of the quenching SERS signal from the labeled compound. Developed indicator sandwich-type systems demonstrate high stability. Such a platform does not require special permissions to work with viruses. Therefore, our approach creates the promising basis for fostering the practical application of ultra-fast, amplification-free methods for detecting coronaviruses based on SARS-CoV-2.

Selective determination of non-organophosphorus insecticide using DNA aptamer-based single-use biosensors.

In the present study, we developed a disposable aptamer-based biosensor for rapid, sensitive, and reliable detection of acetamiprid (ACE). To improve the sensitivity of the aptasensor, poly-5-amino-2-mercapto-1,3,4-thiadiazole [P(AMT)] and gold nanoparticles (AuNPs) were progressively electrodeposited on the screen-printed electrode (SPE) surface by using cyclic voltammetry (CV) technique. For the determination of ACE, thiol-modified primary aptamer (Apt1) was selected by using the SELEX method and immobilized on the surface of the P(AMT) and AuNPs-modified SPE (SPE/P(AMT)/AuNPs) via AuS bonding. Then, the surface-bound aptamer was incubated with ACE for 45Min. After that, the biotin-labeled aptamer 2 (Apt2) was interacted with the ACE, then the enzyme-labeled step was performed. In this step, alkaline phosphatase (ALP) was bound to the surface through the interaction between Apt2 labeled with biotin and streptavidin (strep)-ALP conjugate. The determination of ACE was achieved by measuring the oxidation signal of α-naphthol, which is formed on the electrode surface through the interaction of ALP with α-naphthyl phosphate. The working range of the developed aptasensor was determined as 5×10-12 -5×10-10 molL-1 with a low limit of detection (1.5pmolL-1 ). It was also found that the proposed aptasensor possessed great advantages such as low cost, good selectivity, and good reproducibility.

Aptamer-based surface-enhanced resonance Raman scattering assay on a paper fluidic platform for detection of cardiac troponin I.

.Significance: Cardiac troponin I (cTnI) is a primary biomarker for diagnosis of myocardial infarction (MI). In contrast to central laboratory tests for cTnI, point-of-care (POC) testing has the advantage of providing results when the patient is first encountered, which helps high-risk patients to be treated more rapidly and low-risk patients to be released in a timely fashion. A paper fluidic platform is good for POC testing because the paper is abundant, low cost, and disposable. However, current cTnI assays on paper platforms use antibodies as the recognition element, which has limitations due to the high cost of production and antibody stability issues at the POC.Aim: To develop an aptamer-based assay on a paper strip using surface-enhanced resonance Raman spectroscopy (SERRS) for detection of cTnI in the clinically relevant range at the POC.Approach: Gold nanoparticles (AuNPs) were functionalized with a Raman reporter molecule, malachite green isothiocyanate. The functionalized AuNPs were encapsulated in a silica shell and provided a SERRS signal using a handheld Raman system with a 638-nm excitation wavelength. A primary aptamer and a secondary aptamer of cTnI were used in a sandwich assay format to bind the cTnI on a test line of a paper fluidic platform. By measuring the SERRS signal from the test line, the concentration of cTnI was quantitatively determined.Results: The aptamer-based SERRS assay on a paper strip had a detection range of 0.016 to for cTnI, had good selectivity for cTnI compared to three other markers, had good stability over 10 days, and had good performance in the more complex serum sample matrix.Conclusions: The aptamer-based SERRS assay on a paper strip has the potential to provide a sensitive, selective, stable, repeatable, and cost-effective platform for the detection of cTnI toward eventual use in diagnosis of MI at the POC.

Solid-phase colorimetric apta-biosensor for thrombin detection

Herein, we developed a solid-phase colorimetric apta-biosensor for thrombin detection. Aggregation of gold nanoparticles (AuNPs) deposited on a 3-aminopropyltriethoxysilane (APTES) substrate was utilized to form the colorimetric sensor. The APTES-coated substrate with primary aptamer (TBA1)-conjugated AuNPs (AuNP-TBA1) was used to construct the solid-phase sensing platform, where an enhancement of the localized surface plasmon resonance due to the AuNPs was observed upon incubation with a target molecule (thrombin). The introduction of secondary aptamer-conjugated AuNPs (AuNP-TBA2) induced plasmonic coupling of the AuNPs, resulting in significantly enhanced spectral signals and peak shifts and visually detectable color changes. This sensing platform not only includes several advantages, such as simplicity and rapid detection, but also allows naked-eye detection sensitivity at 3 μg/mL with no analytical equipment and a limit of detection of 1.33 μg/mL using UV–vis.

A new lateral flow strip assay (LFSA) using a pair of aptamers for the detection of Vaspin

A new lateral flow strip assay (LFSA) using a pair of aptamers has been designed and successfully developed using a pair of aptamers-functionalized with gold nanoparticles (AuNPs). This new LFSA biosensor system utilizes a cognate aptamer duo binding to vaspin, a target protein, at the two different binding sites, and exhibited a sensitive and highly selective response to vaspin. A sandwich-type format in LFSA was developed based on biotin-labeled primary V1 aptamer immobilized on streptavidin coated membrane as a capturing probe and secondary V49 aptamer conjugated with AuNPs as a signaling probe. Using this LFSA, vaspin could be visibly observed within the detectable concentrations of vaspin up to 5nM in both buffer and serum conditions. The sensitivity of this LFSA developed in this study was ranged from 0.137 to 25nM in buffer and from 0.105 to 25nM in spiked human serum, respectively. The limit of detection (LOD) of this LFSA was found to be 0.137nM and 0.105nM in buffer and spiked human serum condition, respectively. Therefore, this study has shown successful development of a simple yet effective LFSA for vaspin detection, and this development is not only limited to this target, but also other targets with a pair of aptamers available, without any special and laborious instrumentations. This system will be particularly useful as a screening tool for rapid on-site detection of any targets with a pair of aptamers generated.

Fluorescent aptamer-based assay for thrombin with large signal amplification using peroxidase mimetics

This article describes an aptamer-based thrombin assay using a hemin-based peroxidase mimetic for signal amplification. Thrombin is recognized by an immobilized primary aptamer (G1-quadruplex). The G1-quadruplex/hemin complex formed quenches the fluorescence of CdTe quantum dots (QDs) due to photoinduced electron transfer (PET). In the next step, thrombin is associated with a secondary aptamer (G2-quadruplex) consisting of Pt nanoparticles (NPs), G2-quadruplex and hemin to form a sandwich structure. Both the G1-quadruplex/hemin complex and the Pt NPs/G2-quadruplex/hemin complex associated with thrombin act as enzyme mimetics and catalyze the oxidation of hydroquinone by H2O2 to form 2-hydroxy-p-benzoquinone (HPB). The HPB produced quenches the fluorescence of the CdTe QDs via a PET and an inner filter effect, thus causing large signal amplification. The effects were exploited to design a highly sensitive and selective thrombin assay. Under optimized conditions, a linear fluorescence response is achieved in the 0.05 pmol·L−1 to 10 nmol·L−1 concentration range, with a lower detection limit of 15 fmol·L−1. This approach, in our perception, represents a promising platform for sensitive detection of biomolecules for which appropriate aptamers can be found.

Electrochemical aptasensor for mucin 1 based on dual signal amplification of poly(o-phenylenediamine) carrier and functionalized carbon nanotubes tracing tag

Mucin 1 (MUC 1), as a most studied mucin, has become a useful marker for identifying breast cancer in the early stages. In this work, a novel method for the determination of MUC 1 in serum was developed based on a sandwich-type electrochemical aptasensor, which combined a dual signal amplification strategy of poly(o-phenylenediamine)–Au nanoparticles (PoPD–AuNPs) hybrid film as carrier and AuNPs functionalized silica/multiwalled carbon nanotubes core–shell nanocomposites (AuNPs/SiO2@MWCNTs) as tracing tag. The PoPD–AuNPs film provides a suitable microenvironment for stabilizing the primary aptamer (Apt) assembly, and the AuNPs/SiO2@MWCNTs enhances the surface area for immobilizing abundant secondary Apts as well as load large amounts of electrochemical probe thionine (Thi). In the presence of MUC 1, the sandwich-type recognition reacted on the aptasensor surface, and the Thi-AuNPs/SiO2@MWCNTs nanoprobes were captured onto the electrode surface to form biocomplex. AuNPs and MWCNTs could facilitate the electron transfer from Thi to the electrode, thus amplifying the detection response. Under the optimized experimental conditions, the proposed sensing strategy provided a wider linear dynamic range over three orders of magnitude with the detection limit down to 1pM. Moreover, the aptasensor demonstrated good precision, acceptable stability and reproducibility.

A luminol electrochemiluminescence aptasensor based on glucose oxidase modified gold nanoparticles for measurement of platelet-derived growth factor BB

A sandwich-type luminol electrochemiluminescence (ECL) aptasensor for highly sensitive and selective detection of platelet-derived growth factor BB (PDGF-BB) is fabricated. For this proposed ECL aptasensor, a multilayered AuNPs-electrochemically reduced graphene (AuNPs-EG) nanocomposite film was formed on the GCE surface as the base of the aptasensor through a co-electrodeposition method. The AuNPs-EG composites possess high conductivity to promote the electron transfer at the electrode interface and good biocompatibility and large surface area to capture large amounts of primary aptamer (Apt1), thus amplifying the detection response. Moreover, glucose oxidase (GOD) functionalized AuNPs labeled secondary aptamer (GOD–Apt2–AuNPs) was designed as the signal probe for the sandwiched aptasensor. Enhanced sensitivity was obtained by in situ generation of H2O2 from reaction between GOD and glucose and the excellent catalytic behavior of AuNPs to the ECL of the luminol–H2O2 system. Under the optimal conditions, the as-prepared ECL aptasensor exhibited excellent analytical property for the detection of PDGF-BB in the range from 1.0×10–13 to 5.0×10−10molL−1 with a detection limit of 1.7×10–14molL−1 (S/N=3). The application of the present protocol was demonstrated by analyzing PDGF-BB in human serum and human urine samples with the recoveries from 85.0% to 110%.

An enzyme-free signal amplified strategy based on hollow platinum nanochains catalyzed oxidation of uric acid for electrochemical aptasensor construction

This work designed an enzyme-free aptasensor for thrombin detection using hollow platinum nanochains (HPtNCs) to catalyze uric acid oxidation as signal amplification strategy and Au-Pt nanoflowers (Au-PtNFs) functionalized C60 nanoparticles (nano-C60) as interface. Firstly, the nano-C60 was coated on the bare electrode and then the Au-Pt nanoflowers (Au-PtNFs) were decorated on the resultant electrode by electrodepositing method to obtain the Au-PtNFs/nano-C60 interface. Subsequently, the thrombin primary aptamer (TBA I) was immobilized on the modified electrode through interaction between Au-PtNFs and -SH in TBA I. Next, the HPtNCs were prepared and acted not only as nano-carries for thrombin secondary aptamer (TBA II) loading but also as efficient catalyst towards uric acid (UA) for signal amplification. With target thrombin (TB) being present, the sandwiched structure can be formed between the TBA I and HPtNCs labeled TBA II to achieve the enhanced signal. Under optimized conditions, the proposed aptasensor showed a linear range of 0.5pM to 10nM with a correlation coefficient of R=0.998 and a detection limit of 0.16pM, which exhibited a wide linear range and a low detection limit.

Planar Hall magnetoresistive aptasensor for thrombin detection

The use of aptamer-based assays is an emerging and attractive approach in disease research and clinical diagnostics. A sensitive aptamer-based sandwich-type sensor is presented to detect human thrombin using a planar Hall magnetoresistive (PHR) sensor in cooperation with superparamagnetic labels. A PHR sensor has the great advantages of a high signal-to-noise ratio, a small offset voltage and linear response in the low-field region, allowing it to act as a high-resolution biosensor. In the system presented here, the sensor has an active area of 50µm×50µm with a 10-nm gold layer deposited onto the sensor surface prior to the binding of thiolated DNA primary aptamer. A polydimethylsiloxane well of 600-µm radius and 1-mm height was prepared around the sensor surface to maintain the same specific area and volume for each sensor. The sensor response was traced in real time upon the addition of streptavidin-functionalized magnetic labels on the sensor. A linear response to the thrombin concentration in the range of 86pM–8.6µM and a lower detection limit down to 86pM was achieved by the proposed present method with a sample volume consumption of 2µl. The proposed aptasensor has a strong potential for application in clinical diagnosis.

Aptamer-based portable biosensor for platelet-derived growth factor-BB (PDGF-BB) with personal glucose meter readout

A novel portable biosensor for sensitive and selective detection of platelet-derived growth factor-BB (PDGF-BB) had been developed based on the specific recognition between aptamer and protein using a personal glucose meter (PGM) as readout. In the presence of PDGF-BB, the primary aptamer of PDGF-BB which is bound to the surface of streptavidin magnespheres paramagnetic particles (SA-PMPs) reacts quantitatively with invertase-functionalized secondary aptamer of PDGF-BB to form a stable complex, resulting in the attachment of invertase on the SA-PMPs. Subsequently, the invertase catalyzes the hydrolysis of sucrose to produce a large amount of glucose and quantitative readout by the PGM. The enhanced signal of the PGM has a relationship with the concentration of PDGF-BB in the range of 1.0×10–14M~3.16×10−12M, and the detection limit is 2.9fM. The proposed portable biosensor had been successfully applied to assay the PDGF-BB in saliva samples.

An aptamer-based biosensor for sensitive thrombin detection with phthalocyanine@SiO2 mesoporous nanoparticles

Silica nanoparticles, with entrapped hydrophobic photosensitizer tetra-α-(2, 4-di-tert-butylphenoxy)-phthalocyaninato zinc (ZnPc(OAr)4), were synthesized by hydrolyzing triethoxyvinylsilane (TEVS) and 3-amino propyl triethoxysilane (APTES). The as-prepared nanoparticles, which were highly monodispersed spheres (about 100nm), exhibited strong Q-band absorption of ZnPc(OAr)4 centered at 701nm. The aqueous solubility of ZnPc(OAr)4 encapsulated in silica nanoparticles was obviously improved. The nanoparticles efficiently generated singlet oxygen (1O2) both in organic and aqueous solutions after being irradiated at suitable wavelength. The resulting 1O2 then initiated chemiluminescence (CL) by reacting with a methyl cypridina luciferin analog (MCLA). Based on the photoinduced CL, a sensitive aptamer-based sandwich-type sensor was presented to detect human thrombin. Thrombin was first attached to Pc@SiO2 via secondary aptamer, and then they were collected, for CL determination, by beads with primary aptamer. The proposed approach, which was highly selective with a low detection limit of 80pmol/L, minimized the nonspecific adsorption. Such an aptamer-based biosensor is feasible in screening biomarkers in complex matrices at ultratrace levels.

Ultrasensitive aptasensor based on graphene-3,4,9,10-perylenetetracarboxylic dianhydride as platform and functionalized hollow PtCo nanochains as enhancers

A novel electrochemical aptasensor for ultrasensitive detection of thrombin is described that uses the conductive graphene-3,4,9,10-perylenetetracarboxylic dianhydride nanocomposites (GPA) as desirable sensor platform and hollow PtCo nanochains–thionine–Pt–HRP labeled secondary thrombin aptamer (HPtCoNCs–Thi–Pt–HRP–TBA, aptamer II) for signal amplification. With the surface area enhanced by GPA nanocomposites, the amount of immobilized primary thrombin aptamer can be improved. More importantly, the synthesized HPtCoNCs also yielded large surface area, which provide substantial binding sites for thionine–Pt–HRP–TBA. The thionine acts as a mediator of electron transfer between HRP and electrode surface. Enhanced sensitivity was achieved by introducing the multibioconjugates of aptamer II onto the electrode surface through “sandwich” reactions. With amplifying factors mentioned above, a wider linear range from 10−15 to 10−9M was acquired with an ultralow detection limit of 6.5×10−16M for thrombin. This amplification strategy showed acceptable stability and reproducibility, high sensitivity, and good precision, which could provide a promising potential for clinical screening and point-of-care diagnostics.

A multi-amplification aptasensor for highly sensitive detection of thrombin based on high-quality hollow CoPt nanoparticles decorated graphene

In this work, we have successfully demonstrated a facile strategy to incorporate high-quality hollow CoPt bimetal alloy nanoparticles (HCoPt) onto reduced graphene oxide sheet (HCoPt-RGs). An advanced sandwich-type electrochemical aptasensor for thrombin was proposed by using the HCoPt-RGs conjugates as secondary label. The formed conjugates provided large surface area for loading plentiful redox probe thionine (Thi), horseradish peroxidase (HRP) and secondary aptamer (Apt II) with good stability and friendly biocompatibility, indicating their superior properties in electroactive mediator enrichment and biomolecule immobilization. Furthermore, activated by glutaraldehyde (GA), the chitosan-hollow CoPt alloy nanoparticle (CS-HCoPt) film can greatly facilitate the capture of primary aptamer (Apt I) and dramatically reduce the nonspecific binding. Excellent sensitivity was obtained by detecting the conspicuously enhanced electrochemical signal of Thi, which was amplified by HCoPt alloy nanoparticles and HRP toward the catalytic reduction of H 2O 2. The aptasensor displayed excellent performance for thrombin with a wide linearity in the range from 1.0 × 10 −12 to 5.0 × 10 −8 M and a relatively low detection limit of 3.4 × 10 −13 M. Moreover, the resulted aptasensor also exhibited good specificity, acceptable reproducibility and stability, indicating that the present strategy could pave a promising way for the wide application of graphene in clinical research.

Ultrasensitive label-free aptamer-based electronic detection.

Ultrasensitive label-free aptamer-based electronic detection.