Principle Of Complementary Base Pairing Research Articles

A controllable Y-shaped DNA structure assisted aptasensor for the simultaneous detection of AFB1 and OTA based on ARGET ATRP.

The development of a simple, rapid, and sensitive technology for the simultaneous detection of mycotoxins is of great significance in ensuring the safety of foods and drugs. Herein, a fluorescence aptasensor with high sensitivity and reproducibility for the simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA) was developed. In this sensing system, AFB1 and OTA aptamers were co-immobilized on the surface of magnetic beads (MBs) to form a Y-shaped structure through the principle of complementary base pairing, and were used as recognition probes to specifically capture the target. Activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) was used as a signal amplification strategy to improve the sensitivity. The initiator modified at the end of an antibody initiates the ARGET ATRP reaction. Different fluorescence signals were designed to achieve the simultaneous detection of OTA and AFB1 with limits of 426.18 and 79.55 fg mL-1 for AFB1 and OTA, respectively. In addition, experiments were conducted on three types of samples, and the recoveries of the two mycotoxins ranged from 87.30% to 109.50%, with relative standard deviations ranging from 0.50% to 4.92% under reproducible conditions. The results suggest that the developed aptasensor is sufficient to meet the different regulatory requirements of the two mycotoxins in food and drug safety and shows great potential.

Research progress on the application of framework nucleic acid in bone regeneration.

Framework nucleic acid (FNA) is a set of DNA nanostructures characterized by the framework morphology. It can design rational DNA sequences and follow the principle of complementary base pairing to construct FNA. The recent discovery of FNA constructed by DNA nanotechnology has great application potential in the field of bone regene-ration. It plays a positive role in the osteogenic differentiation of stem cells, bone regeneration, vascular regeneration, neuromodulation, immune regulation, and drug delivery. Here, we reviewed the current study findings on FNA in the field of bone regeneration.

Quantitative image analysis for sensing HIV DNAs based on NaGdF4:Yb,Er@NaYF4 upconversion luminescent probe and magnetic beads

A quantitative image analysis and separation system has been designed for detection of human immunodeficiency virus related DNAs by combining of upconversion luminescence nanoprobe and magnetic beads. • A quantitative image analysis and separation system was designed for detection HIV DNAs. • The image analysis was based on the upconversion luminescence total internal reflection. • The quantitative image analysis shows higher sensitivity and wider detection range. A quantitative image analysis and separation system was designed for detection of human immunodeficiency virus (HIV) related DNAs in the red region by combining of upconversion luminescence nanoprobe and magnetic beads (MBs). Carboxyl-modified NaGdF 4 :Yb,Er@NaYF 4 upconversion nanoparticles (UCNPs) were connected to single-stranded DNA to form a reporter probe, while carboxyl-modified magnetic beads were connected to another single-stranded DNA to form a capture probe. In the presence of target HIV DNAs, NaGdF 4 :Yb,Er@NaYF 4 UCNPs and magnetic beads were conjugated to form UCNPs-DNA-MBs nanocomplexes through DNA-DNA heteroduplexes based on the principle of complementary base pairing. After magnetic separation, the upconversion luminescence intensity of UCNPs-DNA-MBs nanocomplexes was related to the concentration of the target HIV DNAs. The detection methods were investigated by fluorescence spectrometry and quantitative image analysis based on upconversion luminescence total internal reflection (TIR) imaging platform. Compared to the luminescence spectral analysis, the quantitative image analysis shows higher sensitivity (linear range of 0.02−30 nM and detection limit of 0.0102 nM). More importantly, this method only needs 10 μL sample and the analysis time is about 0.1 s. The method combines quantitative image analysis with magnetic separation technology, which has the characteristics of low background interference and high separation efficiency allowing for application to the field of biology.

Electrochemiluminescence immunoassay for the prostate-specific antigen by using a CdS/chitosan/g-C3N4 nanocomposite.

An electrochemiluminescence (ECL) biosensor was fabricated for the evaluation of prostate specific antigen (PSA). The sensor was developed by successively modifying glassy carbon electrode (GCE) electrodes with CdS/Chito/g-C3N4 nanocomposites and DNA1 was labeled at the 5' end with thiol. The aptamer DNA was labeled at the 3' end with a quencher ferrocene (Fc) was ligated to DNA1 by the principle of complementary base pairing. In the absence of PSA, the ECL intensity signal is effectively quenches through the energy transfer and photoexcitation electron transfer between CdS/Chito/g-C3N4 emitter and quencher Fc. After incubation with target PSA, the aptamer DNA interacts with PSA and then moved away from the electrode surface together, which will recover the ECL intensity. Under the optimal conditions, the ECL intensity increases linearly with the logarithm of PSA concentration in the range of 1pg·mL-1 to 100ng·mL-1, and the detection limit is 0.14pg·mL-1 (S/N = 3). The biosensor has been successfully applied to the determination of PSA in serum sample. Graphical abstractSchematic representation of the electrochemiluminescence sensor based on a CdS/chitosan/g-C3N4 nanocomposite, which can be applied to the determination of prostate specific antigen in serum.

CRISPR/Cas9 System and its Research Progress in Gene Therapy.

Genome editing refers to changing the genome sequence of an organism by knockout, insertion, and site mutation, resulting in changes in the genetic information of the organism. The clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR-associated protein-9 nuclease (Cas9) system is a genome editing technique developed by the acquired immune system in the microbes, such as bacteria and archaebacteria, which targets and edits genome sequences according to the principle of complementary base pairing. This technique can be used to edit endogenous genomic DNA sequences in organisms accurately and has been widely used in fields, such as biotechnology, cancer gene therapy, and dermatology. In this review, we summarize the history, structure, mechanism, and application of CRISPR/Cas9 in gene therapy and dermatological diseases.

Electrochemical aptasensor based on gold modified graphene nanocomposite with different morphologies for ultrasensitive detection of Pb2+

A sensitive electrochemical aptasensor was designed based on gold modified graphene nanocomposite with different morphologies for the detection of lead ion (Pb2+). Specifically, a sulfydryl-labeled substrate strand (Apt1) and a sulfydryl-labeled catalytic strand (Apt2) were devised in fabricating the electrochemical aptasensor. Gold modified porous reduced graphene oxide (Au@p-rGO) was synthesized and applied as support for immobilizing the Apt1. And gold modified graphene oxide (Au NPs@GO) was employed as signal probe and connected with Apt2 to realize the immobilization of it on the electrode by means of the principle of complementary base pairing. The current signal can be obtained by recording the electrocatalytic conditions toward H2O2. The Pb2+-dependent DNAzyme could play a role when Pb2+ existed. With the increase of the concentration of Pb2+, the current response revealed a diminishing signal, thus realizing the sensitive detection of Pb2+. Under the optimal conditions, the fabricated electrochemical aptasensor exhibited a linear response toward Pb2+ ranging from 5 pmol/L to 1 μmol/L, together with a low limit of detection of 1.67 pmol/L. Moreover, the prepared aptasensor displayed outstanding selectivity, acceptable stability and superior reproducibility for detecting Pb2+. This proposed tactics may provide reference and potential applications for detecting some other heavy metal ions.

Development of CdSe⁻ZnO Flower-Rod Core-Shell Structure Based Photoelectrochemical Biosensor for Detection of Norovirous RNA.

In this work, the CdSe–ZnO flower-rod core-shell structure (CSZFRs) was prepared by ion-exchange method. The surface of CSZFRs was modified by 3-mercaptopropionic acid (MPA), and then the DNA probe was immobilized on the surface via chemical bond between -NH2 of DNA probe and -COOH of MPA. Finally, the target norovirous (NV) RNA was combined with the probe according to the principle of complementary base pairing, resulting in a decrease of the photocurrent. The results show that the absorbance spectrum of visible light is enhanced for CSZFRs compared with pure ZnO. Under visible light irradiation, the photocurrent of CSZFRs is up to 0.1 mA, which can improve the sensitivity of the photoelectrochemical (PEC) biosensor. In the measurement range of 0–5.10 nM, the measured concentrations (c) have a good linear relationship with the output photocurrent of the biosensor. The linear regression equation is expressed as I = 0.03256 − 0.0033c (R2 = 0.99, S/N = 3) with a detection limit of 0.50 nM. Therefore, this work realizes a rapid and sensitive method for the detection of NV RNA.

Design and synthesis of a novel lanthanide fluorescent probe (TbIII-dtpa-bis(2,6-diaminopurine)) and its application to the detection of uric acid in urine sample

In this study, a novel fluorescent probe, TbIII-dtpa-bis(2,6-diaminopurine) (Tb-dtpa-bdap), is designed based on the principle of complementary base pairing and synthesized for uric acid detection. The synthesized fluorescent probe is characterized by 1H NMR, 13C NMR, infra-red (IR) spectrum and ultraviolet-visible (UV–vis) spectra. It is found that the fluorescence of Tb-dtpa-bdap solution can be quenched obviously in the presence of uric acid. The affecting factors, including solution acidity, uric acid concentration and interfering substances, on the detection of uric acid using this probe are examined. Under optimized conditions, the fluorescence intensities of Tb-dtpa-bdap solution towards different uric acid concentrations show a linear response in the range from 1.00 × 10−5 mol·L−1 to 5.00 × 10−5 mol·L−1 with a linear correlation coefficient (R2) of 0.9877. And the obtained limit of detection (LOD) is about 5.80 × 10−6 mol·L−1, which is lower than the level of uric acid in actual urine. The mechanism on the detection of uric acid by using Tb-dtpa-bdap is inferred from the experimental results. The facts demonstrate that the proposed fluorescent probe can be successfully applied for the determination of uric acid in human urine samples.

Efficient Detection of Environmental Estrogens Bisphenol A and Estradiol By Sensing System Based on AuNP-AuNP-UCNP Triple Structure

A sensing system based on AuNP-AuNP-UCNP triple structure for efficient detection of dual targets bisphenol A and estradiol was constructed. In the preparation of triple structure, the gold nanoparticles (AuNPs) and upconversion nanoparticles (NaYF4: Yb, Er, Gd, UCNPs) were synthesized and surface modified. Then, the two nanoparticles and their aptamers were connected to form two kinds of optical fluorescent probes. A nucleic acid sequence that matches with two aptamers was designed, rendering the probes to get close based on the principle of complementary base pairing. On the basis of this, a sensing system with triple structure was prepared, and its connecting effect was characterized by TEM. With this system, dual targets of bisphenol A and estradiol were detected efficiently and conveniently through quantitatively determination by fluorescence and UV spectrophotometer. At the reaction temperature 30 °C and pH 7.8, this method exhibited good linear range for determination of bisphenol A and estradiol from 2 ng mL–1 to 200 ng mL–1 and from 10 ng mL–1 to 150 ng mL–1, with the limits of detection of 0.2 ng mL–1 and 0.5 ng mL–1, respectively. This sensing system with triple structure owned better specificity to structural and functional analogues, showed good repeatability and stability. What's more, this sensing system could be applied to actual water detection, with the recoveries of 86.1%–107.4%, and the relative standard deviation below 6.8%. This method shows promising applications in other environmental estrogens in water sample.

Nucleobase chemosensor based on carbon nanodots

A facile and sensitive fluorescence protocol for nucleobase detection was developed based on carbon nanodot (CD) chemosensors. The novel fluorescent CDs were prepared using four kinds of nucleobases (including adenine, guanine, thymine and cytosine) as separate carbon sources via simple hydrothermal strategy. The quantum yield of adenine CDs (A-CDs), guanine CDs (G-CDs), thymine CDs (T-CDs) and cytosine CDs (C-CDs) was checked as 15.1%, 28.3%, 10.6% and 11.7%, respectively. Four CDs can recognize their complementary nucleobases based on the principle of complementary base pairing. Their fluorescence was linearly quenched with the increase of nucleobase concentrations under optimal conditions. Combining the calibration curve, quantitative assay of nucleobase in solution can be realized. For example, A-CDs could determine thymine in the concentration range of 2–20mM with a detection limit of ca. 0.053mM, and the linear equation is fitting as (I0−I) / I = 0.01961 × CT(mM) + 0.01756 (R2 = 0.994). Thymine can induce the fluorescence lifetime of A-CDs decreasing from 5.58 to 3.34ns, indicating a dynamic quenching mechanism. The novel nucleobase sensors were also evaluated in specific solution environment. A-CDs showed a relatively minor relative standard deviation (< 4.0%) in fetal calf serum solution, indicating a high accuracy and credibility of the sensing system. In view of the excellent sensitivity, preferable biocompatibility as well as simple constructing method, the sensing platform derived from the nucleobase-based CDs present great potential in biological sensing applications.