Advanced Agrochem最新文献

Functional nucleic acids including aptamers and DNAzymes are a class of valuable molecular tool for biotechnology. However, DNA and RNA aptamers and catalysts suffer from low biological stability and limited chemical diversity. Xeno-nucleic acids (XNAs) refer to nucleic acid analogues containing sugar moieties that are structurally distinct from DNA and RNA and possess advantageous properties. In this article, we first focus on two types of XNAs, threose nucleic acid (TNA) and 2’-fluoroarabinose nucleic acid (FANA), and summarize recent in vitro selections of TNA and FANA aptamers and catalysts. We then review three classes of unnatural base pairs (UBPs) and highlight examples of UBP-containing DNA aptamers and DNAzymes. Lastly, we briefly describe an XNA-modified DNAzyme 10–23 (X10-23) and its application in RNA knockdown and virus detection. Functional XNAs provide important chemical biology tools for biomedical research and future interdisciplinary collaboration will boost XNA basic research and clinical translation.

The development of simple and accurate detection of uracil-DNA glycosylase (UDG) is of great significance for early clinical diagnosis and biomedical research. Here, we on the first effort introduced the uracil bases into the rolling circle amplification (RCA) reaction to produce the functionalized pure DNA hydrogel (PDH) for UDG detection. During RCA process, methylene blue (MB) molecules as the indicators were encapsulated into PDH. The addition of UDG can remove the uracil bases of PDH to generate abasic sites, which are further cleaved with the assistance of apurinic/apyrimidinic endonuclease (APE), thus resulting in the dissociation of PDH to release blue MB. By combining with the paper analytical devices as the signal readout platform, a colorimetric and electrochemical dual-signal biosensor was constructed for convenient and accurate detection of UDG. The proposed MB@PDH-based dual-signal sensing system exhibited good selectivity and high sensitivity with a detection limit of 6.4 × 10⁻⁴ U/mL (electrochemical method). It was also demonstrated that this sensing system showed excellent performance in UDG inhibitor screening, thus providing great potential in UDG-related disease diagnosis and drug discovery.

Estradiol (E2) and related estrogens are emerging environmental contaminants that may adversely affect the health of humans, animals, and ecosystems. Many aptamers have been reported for the detection of E2, and our lab recently selected a series of high-affinity and short DNA aptamers that showed various binding orientations to E2, leading to different selectivity patterns. In this work, we report that using SYBR Green I (SGI) as a fluorescence probe, up to 200% fluorescence increase was achieved upon titration of E2 to these aptamers. Such enhancement was the highest among all reported small molecule binding aptamers using SGI for signal generation, although some metal-binding DNA can achieve even higher enhancement. By gradually shortening the stem region of an E2 binding aptamer, we concluded that the enhanced fluorescence was from the aptamer binding pocket upon target binding instead of from the duplexed stem region. Comparison was also made with a few other aptamers including those for caffeine, quinine, uric acid and cortisol, and none of them showed more than 20% fluorescence change. Using the SGI method, the detection limit was calculated to be 2.4 nM E2. We attributed the large fluorescence enhancement to the hydrophobic nature of E2 and the high-affinity binding of the aptamers. This study provides insights into the aptamers that can use SGI for their binding assays and biosensor development.

The contamination of mycotoxin in food has posed a serious threat to human health and safety. Accurate detection of mycotoxins provides a strong guarantee for food safety. Aptamers with excellent recognition capacity to mycotoxins have gained growing attention because of their high binding affinity, high specificity and low cost. They are commonly generated by an in vitro selection procedure called SELEX. However, the existing performance of mycotoxin aptamers are not good enough in complex food matrix, and the success rate of SELEX still need to be improved. The employment of efficient SELEX strategies for the generation of better mycotoxin aptamers is significantly important. This article has reviewed different SELEX approaches conducted for mycotoxin aptamer generation. Furthermore, the properties of various mycotoxin aptamers have been discussed. Finally, challenges and future considerations for mycotoxin aptamer selection are summarized, and their strengths and limitations in food safety application are highlighted.

As a basic functional unit, living cell with sophisticated structures play an indispensable role in life activities. Since the abnormality of important molecules inside cells is closely related to diseases, the dynamic analysis and spatio-temporal monitoring of specific molecules in living cells can provide precious information for the diagnosis and treatment of diseases. More recently, DNA has not only been recognized as the carrier of genetic information, but has also used as a robust building block for the assembly of multitudinous nanoscale structures due to the intrinsic advantages of high programmability of classic Watson–Crick base-pairing rule. Intensive study promotes the rapid progress of nanotechnology in various fields, such as bioimaging, diagnosis, and therapeutics. Among numerous well-defined DNA nanomaterials, DNA nanomachines have been widely exploited in cell imaging owing to their desirable ability to achieve high-resolution temporal and spatial images in response to endogenous or exogenous stimuli. In brief, elaborate DNA nanomachines can undergo structural changes upon the stimuli of target analytes or environmental factors, resulting in rapid increase or reduction of output signals and thereby indirectly reflecting the expression level of targets. DNA nanomachines with high sensitivity and specificity contribute to the recognition of diseased tissues. In this review, we introduce the basic assembly modules of DNA nanomachines and summarize the recent advances in dynamic DNA nanomachines for diseased-cell imaging. Finally, the current challenges and future directions of DNA nanomachines for bioimaging are discussed.

Fluorescent aptasensor was developed for acrylamide (AAm) detection by utilizing the adsorption effect of Au nanoparticles (AuNPs) and fluorescence properties of SYBR Green I (SGI) towards double-stranded DNA (dsDNA). Compared to the binding of aptamer with AAm, the higher affinity of aptamer with cDNA may facilitate a structure switching from the aptamer/AAm complex to aptamer/cDNA dsDNA. The free aptamers were adsorbed onto AuNPs and separated by centrifugation. Subsequently, SGI was introduced as a fluorescent reporter for quantitative detection. Compared to conventional AuNPs-based colorimetric detection, the sensitivity of this strategy was improved by 3.18-fold in the range of 0.005–50 mg/L with a low detection limit of 4.68 μg/L. The method has been successfully applied to analyze fried twists and biscuits. Notably, it is a low-cost and general method that provides guidance for the development of rapid screening technology in the field.

Mycotoxins are small molecules produced by fungi that contaminate crops and cause notable health effects for humans, owing to their inherent toxicity. Aflatoxins are among the most potent mycotoxins, with aflatoxin B1 and M1 being the most concerning. Due to their negative impact on human health and agro-economics, developing cost-effective, rapid, highly sensitive and specific detection tools is urgently needed. Nucleic acid–based synthetic receptors, aptamers, have been successfully selected for aflatoxin with high binding affinity and selectivity, and have been incorporated into a wide array of sensor platforms. By exploiting the optical properties of metallic nanoparticles, aptasensors have been developed to achieve low-cost, rapid, and sensitive tests to detect contaminated foods. Herein, we describe the use of functional nucleic acids, specifically DNA aptamers with metallic nanoparticles such as gold and silver for detecting aflatoxin B1 and M1. This review highlights various aptamer-nanoparticle assay types designed for colorimetric aflatoxin detection (i.e., solution and paper-based) along with their associated detection limits, as well as their strengths and areas for further development.

Aptamers are short, single-stranded DNA or RNA molecules that selectively bind to a target molecule. Aptamer-complement duplex (ACD) is often used to design molecular switches capable of producing a detectable signal or triggering a structural change upon aptamer binding to a target. However, such aptamer switch generally faces an increased dissociation constant (K_d) due to the energy barrier of the complementary duplex. We reported a competitive hybridization mechanism to modulate the binding affinity of an ACD to a target adenosine. Using the computation-guided design, we calculated the aptamer folding energy for the duplex length from 11-nt to 15-nt, and experimentally measured increased apparent K_d values resulted from these extended duplexes. Using a set of strands to compete with the ACD hybridization, it reduced the aptamer folding energy to facilitate aptamer switches with decreased apparent K_d values ranging from over 400 μM without a competing strand to ∼30 μM with a competing strand. This competitive aptamer switch was also found sensitive to single-nucleotide mutations of a competing strand. Our work provides an approach to modulate the binding affinity and the sensitivity of aptamer-complement duplexes, which could be useful in the nucleic acids-based sensing and nanomedicine.

Silver ions are regarded as one of the most hazardous metal contaminants, endangering both the ecological environment and human health. Traditional silver ions detection technologies are hampered by their high cost, time-consuming nature, and labor-intensive operation. DNA aptamers play an essential part in the field of biosensors due to their ease of synthesis, ease of modification, and low cost. This paper focuses on reviewing the research progress of DNA aptamer-based biosensors in silver ions detection. According to the types of signal transduction, they are classified into four forms of signal transduction: fluorescent biosensors, colorimetric biosensors, electrochemical biosensors, and surface-enhanced Raman spectroscopy biosensors. In addition, this paper gives a perspective on the application prospects outlook and development directions of DNA aptamer-based biosensors, in order to provide theoretical ideas for the future development of more sensitive DNA aptamer biosensors for rapid detection of silver ions.