Rolling Circle Amplification as an Efficient Analytical Tool for Rapid Detection of Contaminants in Aqueous Environments

Environmental contaminants are a global concern, and an effective strategy for remediation is to develop a rapid, on-site, and affordable monitoring method. However, this remains challenging, especially with regard to the detection of various contaminants in complex water environments. The application of molecular methods has recently attracted increasing attention; for example, rolling circle amplification (RCA) is an isothermal enzymatic process in which a short nucleic acid primer is amplified to form a long single-stranded nucleic acid using a circular template and special nucleic acid polymerases. Furthermore, this approach can be further engineered into a device for point-of-need monitoring of environmental pollutants. In this paper, we describe the fundamental principles of RCA and the advantages and disadvantages of RCA assays. Then, we discuss the recently developed RCA-based tools for environmental analysis to determine various targets, including heavy metals, organic small molecules, nucleic acids, peptides, proteins, and even microorganisms in aqueous environments. Finally, we summarize the challenges and outline strategies for the advancement of this technique for application in contaminant monitoring.

MiRNA Detection Using a Rolling Circle Amplification and RNA-Cutting Allosteric Deoxyribozyme Dual Signal Amplification Strategy

A microRNA (miRNA) detection platform composed of a rolling circle amplification (RCA) system and an allosteric deoxyribozyme system is proposed, which can detect miRNA-21 rapidly and efficiently. Padlock probe hybridization with the target miRNA is achieved through complementary base pairing and the padlock probe forms a closed circular template under the action of ligase; this circular template results in RCA. In the presence of DNA polymerase, RCA proceeds and a long chain with numerous repeating units is formed. In the presence of single-stranded DNA (H1 and H2), multi-component nucleic acid enzymes (MNAzymes) are formed that have the ability to cleave substrates. Finally, substrates containing fluorescent and quenching groups and magnesium ions are added to the system to activate the MNAzyme and the substrate cleavage reaction, thus achieving fluorescence intensity amplification. The RCA–MNAzyme system has dual signal amplification and presents a sensing platform that demonstrates broad prospects in the analysis and detection of nucleic acids.

Rolling circle amplification with electrochemical detection assay for SARS-CoV-2

This protocol describes the rolling circle amplification (RCA) and electrochemical detection of SARS-CoV-2. The procedure consists of 3 parts, which are the amplification, hybridization and detection steps. In the presence of RNA template, the circular DNA template will be ligated to produce a Padlock DNA, which serves as a template for amplification by phi29 DNA polymerase to produce RCA amplicons. The RCA amplicon is a concatemer containing multiple repeats of sequences that are complementary to the circular template. The RCA amplicons are hybridized with redox active probes and detected by electrochemical biosensor using differential pulse voltammetry (DPV). Due to its isothermal nature, RCA can be performed using a simple water bath or heating block. Overall, the whole assay takes approximately 45 min. The assay enables rapid, quantitative results to be obtained for detection of SARS-CoV-2, either in the laboratory or more importantly, in a field setting.

Application of Cardiovascular Angiography in Diagnosis of Heart Disease Based on Adaptive Tracking Circular Template Technique

Objective: To explore the application value of cardiovascular extraction technique in the complex and/or complex malformation of congenital heart disease (CHD) and the application of deep learning to the diagnosis of medical imaging. Methods: Quantitative description of cardiovascular lesions and reconstruction of three-dimensional cardiovascular using angiographic images, the cardiovascular representation of the contrast image as a single pixel wide cardiovascular skeleton, using a rotating Gaussian function to enhance the image, using adaptive tracking circular template pair Enhanced cardiovascular images for cardiovascular extraction. The 360 cases of complex and/or complex malformation were analyzed and their association with clinical examinations such as echocardiography. Results: This group of 360 patients (including 75 cases of pulmonary atresia with ventricular septal defect, 62 cases of right ventricular double exit, 60 cases of tetralogy of Fallot, 52 cases of single ventricle, 42 cases of aortic dislocation, 15 cases of tricuspid atresia, 6 cases of coronary artery Abnormalities, 5 cases of complete pulmonary venous malformation, 5 cases of complete endocardial pad defect, 4 cases of common arterial trunk, 3 cases of interventricular complete pulmonary atresia, 7 cases of other cases and 24 cases of postoperative examination) angiography. Compared with ultrasound, the latter was corrected in 34 cases, missed diagnosis in 30 cases, and misdiagnosis in 16 cases of combined malformation. The detection and diagnosis of collateral vessels, coronary artery malformations and branches of pulmonary arteries and their abnormalities in complex and/or complex malformations are superior to echocardiography, and can measure pulmonary arterial and venous pressures and collateral vessel pressure It is superior to other imaging methods. Conclusions: Cardiac angiography (DSA) is still important for the diagnosis and differential diagnosis of difficult cases of congenital heart disease complex and/or complex malformation, especially showing the whole appearance and related lesions of the body, lung and coronary branches, as well as measuring pulmonary artery and ventricular pressure.

Amplified visual detection of microRNA-378 through a T4 DNA ligase-mediated circular template specific to target and target-triggering rolling circle amplification

MicroRNA-378 (miRNA-378) is widely regarded as a novel noninvasive serum biomarker for early detection of gastric cancer.

Real-time Terrain Matching Based on 3D Zernike Moments

Since the descriptors based on Three-Dimensional (3D) Zernike moments are robust to geometric transformations and noise, they have been proposed for terrain matching. However, terrain matching algorithms based on 3D Zernike Moments (3DZMs) are often difficult to implement in practice since they are computationally intensive. This paper presents a more efficient real-time terrain matching algorithm based on 3DZMs for land applications. Two efficient methods based on coordinate transformation and symmetry are proposed to compute the geometric moments. The impact of the sample difference on the matching result due to heading angle is investigated to prove the feasibility of using a circular template. Consequently, the terrain feature vectors of the reference map can be computed off-line with the circular template to significantly reduce on-line computation. Numerical experiments on a real digital elevation model demonstrate that the proposed algorithm is robust to the heading angle and can be implemented for real-time terrain matching operations.

Copy Move Forgery Image Detection via Discrete Radon and Polar Complex Exponential Transform-Based Moment Invariant Features

Copy move forgery with geometric distortions such as the rotational operation, the scaling operation, the mirror operation and the additive noise operation became more common. Existing methods are not competent for the detection of the copy move forgery with these distortions. In fact, the most critical issue for the detection of the forgery is the determination of the geometric features. This paper proposes an efficient Discrete Radon Polar Complex Exponential Transform (DRPCET)-based method for the extraction of the rotational and the scaling invariant features for the copy move forgery detection. First, the features obtained by the Radon transform (RT) and the Polar Complex Exponential Transform (PCET) are fused together. Then, these features are normalized. In order to achieve the scaling invariant property, an auxiliary circular template is introduced. With the auxiliary circular template, the translational moment invariant features, the rotational moment invariant features and the scaling moment invariant features are constructed for the extraction of the planar geometrical features. By further extracting some useful features for the representation of the image background, the interference of the background information can be reduced. After extracting the geometrical features, the lexicographic sorting is applied. Then, a correlation between the same part or similar parts of the image which are copied and moved to another image is computed. Based on the obtained correlations, these forgery parts can be identified and their composed positions can be located. Finally, these images are denoted as the forgery image. Extensive computer numerical simulations have been performed. The obtained results show that the proposed method can detect the copy move region in the forgery image precisely even though the forgery regions are suffered from the mixed geometric distortions.