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Graphene-Based Steganographicly Aptasensing System for Information Computing, Encryption and Hiding, Fluorescent Sensing and In Vivo Imaging of Fish Pathogens
摘要： Inspired by information processing and communication of life based on complex molecular interactions, some artificial (bio)chemical systems have been developed for applications in molecular information processing or chemo/biosensing and imaging. However, little attention has been paid to simultaneously and comprehensively utilize the information computing, encoding and molecular recognition capabilities of molecular-level systems (such as DNA-based systems) for multifunctional applications. Herein, a graphene-based steganographicly aptasensing system was constructed for multifunctional application, which relies on specific molecular recognition and information encoding abilities of DNA aptamers (Aeromonas hydrophila and Edwardsiella tarda-binding aptamers as models) and the selective adsorption and fluorescence quenching capacities of graphene oxide (GO). Although graphene-DNA systems have been widely used in biosensors and diagnostics, our proposed graphene-based aptasensing system can not only be utilized for fluorescent sensing and in vivo imaging of fish pathogens (Aeromonas hydrophila and Edwardsiella tarda), but can also function as a molecular-level logic computing system where the combination of matters (specific molecules or materials) as inputs produces the resulting product (matter level) or fluorescence (energy level) changes as two outputs. More importantly and interestingly, our graphene-based steganographicly aptasensing system can also be served as a generally doubly cryptographic and steganographic system for sending different secret messages by using pathogen-binding DNA aptamers as information carriers, GO as a cover, a pair of keys: target pathogen as a public key, the encryption key used to encode or decode a message in DNA as a private key. Our study not only provides a novel nano-biosensing assay for rapid and effective sensing and in vivo imaging fish pathogens, but also demonstrates a prototype of (bio)molecular steganography as an important and interesting extension direction of molecular information technology, which is helpful in probably promoting the development of multifunctional molecular-level devices or machines.
关键词： aptasensing,steganography,graphene oxide,DNA aptamer,encryption,fish pathogens,in vivo imaging,information hiding
更新于2025-11-21 11:24:58
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Systematic Truncating Aptamers to Create High Performance Graphene Oxide (GO)-based Aptasensors for Multiplex Detection of Mycotoxins
摘要： Graphene Oxide (GO)-based aptasensor is currently one of the most popular sensing platforms for simple and rapid detection of various targets. Unfortunately, the GO-based aptasensors with long aptamer strands typically show unsatisfactory performance resulted from insignificant structural transformations upon target bindings. We report herein the utilization of an aptamer truncating strategy to combat such a challenge. Taking a pre-selected anti-aflatoxin B1 (AFB1) aptamer (P-AFB1-50) as a trial system, we sequentially remove the extraneous nucleotides within the aptamer by means of circular dichroism (CD) spectroscopy and binding affinity analysis. Particularly, the ratio of the quenching constants between the GO sheets and the truncated aptamers (labelled with fluorophores) in the absence and presence of target was determined for each of the truncated aptamers to evaluate the optimal sequence. As a result, the truncated aptamer comprising 40 nucleotides was confirmed to show the highest FL output and best detection limit upon conjugation with GO sheets. More importantly, we demonstrated that this truncating strategy is versatile, i.e., it can be easily extended to other aptamer systems (anti-ochratoxin A (OTA) aptamer, P-OTA-61, as an example) for extraneous nucleotide identification. Impressively, the two optimal truncated aptamers can work together on GO sheets to achieve a simultaneous detection of two different mycotoxins (i.e., AFB1 and OTA) in one single testing. Essentially, this research opens a new avenue for the design and testing of aptamer/GO based-sensing platforms for rapid, low-cost and multiplex quantification of analytical targets of interest.
关键词： DNA/GO-based biosensors,AFB1,OTA,long-chain aptamer,multiplex detection,extraneous nucleotide truncation
更新于2025-11-14 15:28:36
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Determination of 17β-estradiol by surface-enhanced Raman spectroscopy merged with hybridization chain reaction amplification on Au@Ag core-shell nanoparticles
摘要： The authors describe an aptamer-based assay for 17β-estradiol. It relies on the combined use of surface enhanced Raman scattering (SERS) and hybridization chain reaction (HCR). The aptamer against 17β-estradiol is applied as the recognition probes, and this results in excellent specificity. Specific recognition of target 17β-estradiol induce the freedom of DNA 2, which will open the stem-loop structure of probe 1 on the Au@Ag and form the partial dsDNA structure. With the nicking enzyme, the partial dsDNA will be hydrolyzed and the reside ssDNA on Au@Ag will form a small stem-loop structure. With the help of the other probe 2 modified Au@Ag and pre-immobilized probe 3 on the well of the microplate, an enzyme-free HCR can occur and tremendous Au@Ag can be assembled along the formed dsDNA in HCR, which can act as the excellent substrate for Raman measurement and greatly amplify the Raman signal of R6G on the Au@Ag. Afterwards, the key factor, ratio between probe 2-Au@Ag (P2) and probe1-Au@Ag (P1), affects the detection sensitivity is systematically optimized for the best sensing performance. The SERS signal of R6G, best measured at 1651 cm?1, increases linearly in the wide range from 1 pM to 10 nM. The detection limit can be as low as 0.1 pM.
关键词： Estrogen,Hybridization chain reaction,SERS,Food safety,Aptamer,Gold nanoparticle,Signal amplification,Environment monitoring
更新于2025-09-23 15:23:52
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Development of an Aptamer-Conjugated Polyrotaxane-Based Biodegradable Magnetic Resonance Contrast Agent for Tumor-Targeted Imaging
摘要： Gadolinium-based magnetic resonance imaging (MRI) contrast agents with biodegradability, biosafety, and high efficiency are highly desirable for tumor diagnosis. Herein, a biodegradable, AS1411-conjugated, α-cyclodextrin polyrotaxane-based MRI contrast agent (AS1411-G2(DTPA-Gd)-SS-PR) was developed for targeted imaging of cancer. The polyrotaxane-based contrast agent was achieved by the complexation of α-cyclodextrin (α-CD) and a linear poly(ethylene glycol) (PEG) chain containing disulfide linkages at two terminals. The disulfides enable the de-threading of the polyrotaxane into excretable small units due to cleavage of the disulfide linkages by reducing agents such as intracellular glutathione (GSH). Furthermore, the second-generation lysine dendron conjugated with gadolinium chelates and AS1411, a G-quadruplex oligonucleotide that has high binding affinity to nucleolin generally presenting a high level on the surface of tumor cells, coupled to the α-CD via click chemistry. The longitudinal relaxivity of AS1411-G2(DTPA-Gd)-SS-PR (11.7 mM?1 s?1) was two times higher than the clinically used Gd-DTPA (4.16 mM?1 s?1) at 0.5 T. The in vitro degradability was confirmed by incubating with 10 mM 1,4-Dithiothreitol (DTT). Additionally, the cytotoxicity, histological assessment and gadolinium retention studies showed that the prepared polyrotaxane-based contrast agent had a superior biocompatibility and was predominantly cleared renally without long-term accumulation toxicity. Importantly, AS1411-G2(DTPA-Gd)-SS-PR displayed the enhanced performance in MRI of breast cancer cells in vitro as well as a subcutaneous breast tumor in vivo due to the targeting ability of AS1411 aptamer. The enhanced performance was due to efficient multivalent interactions with tumor cells, producing faster accumulation and longer contrast imaging time at the tumor site. This work clearly confirms that the specially designed and fabricated α-CD-based polyrotaxane is a promising contrast agent with excellent contrast imaging performance and biosafety for tumor MR imaging.
关键词： AS1411 aptamer,biodegradability,polyrotaxanes,magnetic resonance imaging,breast cancer targeting
更新于2025-09-23 15:23:52
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A label-free aptamer-based nanogap capacitive biosensor with greatly diminished electrode polarization effects
摘要： A significant impediment to the use of impedance spectroscopy in bio-sensing is the electrode polarization effect that arises from the movement of free ions to the electrode–solution interface, forming an electrical double layer (EDL). The EDL screens the dielectric response of the bulk and its large capacitance dominates the signal response at low frequency, masking information particularly relevant for biological samples, such as molecular conformation changes and DNA hybridization. The fabrication of nanogap capacitors with electrode separation less than the EDL thickness can significantly reduce electrode polarization effects and provide enormous improvement in sensitivity due to better matching of the sensing volume with the size of the target entities. We report on the fabrication of a horizontal thin-film nanogap capacitive sensor with electrode separation of 40 nm that shows almost no electrode polarization effects when measured with water and ionic buffer solutions, thereby allowing direct quantification of their relative permittivity at low frequencies. Surface modification of the electrodes with thiol-functionalized single strand DNA aptamers transforms the device into a label-free biosensor with high sensitivity and selectivity towards the detection of a specific protein. Using this approach, we have developed a biosensor for the detection of human alpha thrombin. In addition, we also examine frequency dependent permittivity measurements on high ionic strength solutions contained within the nanogap and discuss how these support recent experimental observations of large Debye lengths. A large shift in the Debye relaxation frequency to lower frequency is also found, which is consistent with water molecules being in a rigid-like state, possibly indicating the formation of an ordered ‘‘ice-like’’ phase. Altogether, this work highlights the need for better understanding of fluids in confined, nanoscale geometries, from which important new applications in sensing may arise.
关键词： electrode polarization,aptamer,nanogap,capacitive biosensor,dielectric spectroscopy,thrombin
更新于2025-09-23 15:23:52
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G-quadruplex specific dye-based ratiometric FRET aptasensor for robust and ultrafast detection of toxin
摘要： G-quadruplex specific dyes are powerful tools for probing nucleic acid structures. Among nucleic acids, aptamers are of great interest, and widely exploited to construct versatile bioassays. Herein, based on G-quadruplex selective dye, thioflavin T (ThT), for probing the intrinsic structure of aptamers, we proposed a ratiometric fluorescence resonance energy transfer (FRET) aptasensor enabling robust and ultrafast detection of toxin. The binding of target ochratoxin A (OTA) would destruct the G-quadruplex structure of aptamer. It would lead to the detachment of ThT dye from aptamer which diminished the FRET effect between ThT and terminal-labeled dye, thus allowing quantification of OTA via FRET signals. The FRET aptasensor would confer an enhancement of 76.9% of signal to background ratio compared to the ThT-based non-FRET aptasensor. Remarkably, the FRET mechanism would eliminate the signal fluctuation resulted from varied probe concentration, thus benefiting the robustness of the assay. The aptasensor could achieve a detection of limit of 0.38 ng/mL for OTA detection. And the detection of OTA could be finished within 30 s. Besides, the assay was successful in analyzing OTA in coffee and oat samples with recoveries rate of 93.93%–107.59%. Therefore, G-quadruplex specific dye-based probing and FRET method would be a compelling design strategy for aptasensor, and may facilitate their practical application in food safety and environmental screening.
关键词： Fluorescence resonance energy transfer,G-quadruplex specific dyes,Homogeneous analysis,Toxin,Thioflavin T,Aptamer
更新于2025-09-23 15:23:52
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Fluorescent Ag clusters conjugated with anterior gradient-2 antigen aptamer for specific detection of cancer cells
摘要： Fluorescent probes with small size, low toxic and specific recognition are of fundamental interests as well as of practical prospects in bioimaging. Though various probes have been reported up to now, including traditional organic dye, quantum dots, rare earth-based particles, and recently emerged carbon dots, silicon dots, polymer dots and metal cluster et al., the relatively large size and lack of specify are far from satisfaction in cellular imaging. As confirmed in previous reports, the large size might influence the functions of target, where the consequent drawback of non-specific is requiring conjugate with additional ligands which brings even larger size and complex procedures. In such a context, fluorescent metal nanoclusters have rapidly attracted widely concern for their integrated advantages of small size, high stability, unique selectivity and tunable properties by simply selecting different stabilizer. In considering a wide variety of stabilizer, aptamer, as a class of ssDNA, has received particular interest because of the easy production, reduced size comparing with antibody and selectively binding ability in molecule level with specific structures. Former researches have proved that cytosine has strong interaction with Ag cations. Therefore, colorful Ag clusters (AgNCs) have been continuously prepared using different DNA sequences in a simple reductive reaction after mixing both aptamer and Ag cation. Additionally, the as synthesized AgNCs do not influence the selectivity of the aptamer itself. For example, Sun et al. reported a one-step process to synthesize silver nanoclusters by specific aptamer which can selectively image the nuclei of CCRF cells, clearly demonstrates the strength of the aptamer capsulated Ag clusters. Anterior gradient protein 2 homolog (AGR), a homolog of xenopus anterior gradient-2 (XAG-2) of Xenopus laevis, is a typical protein that secret by gland cancer cell. Since being discovered as a pro-oncogenic protein that weakens p53 gene activity in 2004. Clinical studies have shown that AGR is highly expressed in pancreatic, breast, and prostate cancer cells, etc. The molecular function and clinical relevance of AGR with variety cancers have thus been increasingly investigated. Specifically, it is a functional protein that plays a key role in variety of biological systems, including the development of vertebrate tissue and the inflammatory tissue injury response. Overall, Tian's results demonstrated that AGR overexpression could predict poor overall survival (OS) and poor time to tumor progression (TTP) of all solid tumor patients. Therefore, fluorescence recognizing of AGR is important for detecting gland cancer cells. At present, a number of reports related with AGR have been reported, but few on specific recognition probes. Through a series of screening, Wu et al. discovered AGR's corresponding aptamer “C14B1”. Few years later, Hu et al. successfully achieved the direct detection of AGR in vitro. However, in the cell imaging field, there is scarcely report on AGR detection. Therefore, synthesis of fluorescent AgNCs conjugating with aptamer to target AGR could provide a novel method for recognizing human gland cancer cell with a high selectivity, efficiency, and low cytotoxicity. In this paper, modified AGR aptamer (MA) were used as template to synthesize AgNCs. Specifically, MA's sequence is 5′-CGG GTG GGA GTT GTG GGG GGG GGT GGG AGG GTT TTTTT CCC CCC CCC CCC-3′ (50 bases). This sequence consists of two functional parts, AGR-apt sequence for recognition AGR in breast cancer (MCF-7) cells, where 12 cytosine base sequence (12C) for effectively preparing fluorescent AgNCs. According to Li's research, a T5 loop (-TTTTT-) could enhance the fluorescence intensity and avoid the influence of space hindrance. It was incorporated between the 3′ end of the apt and 12C sequence. Eventually, according to optimized reaction conditions, MA stabilized silver nanocluster (MA@AgNCs) with a small size, suitable stability, good selectivity was prepared. The fluorescence excitation peak and emission peak of MA@AgNCs were located at 510 nm and 565 nm respectively with a quantum yield as high as 87.43%. Moreover, MA@AgNCs shows descent specific recognition of MCF-7 cells, suggesting the prepared MA@AgNCs have the ability to selective target gland cancer cell and potentially utilized for clinical diagnosis and treatment.
关键词： Bio-probe,Cell imaging,Anterior gradient-2 antigen,Silver nanoclusters,Aptamer
更新于2025-09-23 15:23:52
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Ultrasensitive analysis of kanamycin residue in milk by SERS-based aptasensor
摘要： An ultrasensitive method for the kanamycin (KANA) detection in milk sample using surface-enhanced Raman spectroscopy-based aptasensor was employed in the current study. Double strand DNA binding bimetallic gold@ silver nanoparticles were developed as a sensing platform. Probe DNAs were first embedded on the surface of gold nanoparticles by the end-modified thiol, and after silver shell encapsulating, KANA aptamer DNAs with the Raman reporter Cy3 were then hybridized with probe DNAs by complementary base pairing. Results showed that with increase in the KANA concentration, the Raman intensity of Cy3 decreased. Besides achieving selectivity, an ultralow detection limit of 0.90 pg/mL, a broad linear relationship ranging from 10 μg/mL to 100 ng/mL in aqueous reagent and satisfactory recoveries of 90.4–112% in liquid whole milk were obtained. The result of actual sample proved that this aptasensor was promising in trace determination of KANA residue.
关键词： Milk,Kanamycin,Aptamer,Surface enhanced Raman spectroscopy
更新于2025-09-23 15:23:52
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Target-recycling-amplified colorimetric detection of pollen allergen using non-cross-linking aggregation of DNA-modified gold nanoparticles
摘要： Increasing prevalence of pollen allergies has raised concerns about human health. Development of a facile and precise method to detect pollen allergens would thus be of significance for environmental assessments and medical diagnoses. Here we report a sensitive colorimetric method to detect the Japanese cedar pollen allergen, Cry j 2. The method consists of two steps: a signal amplification based on the catalytic DNA hairpin self-assembly, followed by a signal transduction using the salt-induced non-cross-linking aggregation of gold nanoparticles densely modified with short DNA. The assay exhibits a detection limit of 0.2 ng/mL, which is 130-fold greater than that of the previously reported one. Moreover, the assay enables the detection of Cry j 2 spiked in soil solutions by avoiding any interference from the contaminants. The signal amplification system includes an anti-Cry j 2 DNA aptamer, which accounts for the absence of false responses to five non-target allergen proteins. The present method could be of general applicability to various proteins by using appropriate aptamers.
关键词： Surface plasmon resonance,Allergen,Aptamer,Gold nanoparticle,DNA,Cry j 2
更新于2025-09-23 15:23:52
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Determination of Saxitoxin by Aptamer-Based Surface-Enhanced Raman Scattering
摘要： Saxitoxin is one of the most harmful paralytic shellfish toxins due to its high toxicity and adverse effects on the environment and human health. Aptasensors provide simple detection procedures because they have the advantages of chemical stability, easy synthesis and modification, and high convenience in signal transformation. Surface-enhanced Raman scattering (SERS) is an analytical technique that amplifies the analytical signals of molecules at extremely low concentrations, or even at the single molecule level, when the analyte is very close to rough metal surfaces or nanostructures. In this study, an SERS aptasensor is reported for the determination of saxitoxin for the first time. The optimized saxitoxin aptamer (M-30f) was modified on gold nanoparticles and served as the recognition element. Crystal violet was used as the Raman reporter without chemical bounding. The analytical principles of the aptasensor are that saxitoxin destabilized the conformations of the aptamer at high temperature conditions and altered the binding of crystal violet on the gold nanoparticles. In the presence of saxitoxin, the conformation of aptamer containing the G-quadruplex that selectively bound crystal violet unfolded to a large extent and hence the crystal violet molecules were released from gold nanoparticles with a reduced SERS signal. The effects of the gold nanoparticle size, the amount of DNA, aptamer density, sodium chloride concentration, and operation temperature upon the SERS determination were optimized. The resulting simple SERS aptasensor was developed with a satisfactory limit of detection (11.7 nM) and selectivity. The application for the analysis of real shellfish samples with simple procedures demonstrates that this SERS aptasensor is promising for on-site applications.
关键词： saxitoxin,paralytic shellfish toxin,surface-enhanced Raman scattering (SERS),Aptamer
更新于2025-09-23 15:23:52