A novel nucleic acid amplification system based on nano-gap embedded active disk resonators

Acid-activated bentonite for solid-phase nucleic acid extraction from various pathogenic samples

BACKGROUND

Despite significant advancements in nucleic acid testing technologies, current nucleic acid extraction methods are often limited by inefficiency, complexity, and a lack of versatility. To overcome these challenges, we have developed an innovative solid-phase extraction (SPE) method employing sulfuric acid-activated bentonite (SAB) for extracting nucleic acids from various sample types.

RESULTS

Activation with sulfuric acid expands the surface area of bentonite by 2.2 times, thereby enhancing its adsorption capacity and surface modification efficiency. To further improve extraction efficiency, we modified SAB through amine-functionalization using 3-aminopropyl(diethoxy)methylsilane (APDMS), resulting in the creation of APDMS-modified SAB (ASAB). This modification facilitates efficient nucleic acid binding via reversible interactions mediated by a homobifunctional imidoester (HI) reagent. Our ASAB-based SPE system offers a streamlined, universal protocol for isolating DNA, RNA, and miRNA from diverse samples, including clinical bodily fluids and culture media, in under 30 min. Moreover, the system effectively enriches low concentrations of negatively charged pathogens (down to 20 CFU/reaction) from large-volume samples (up to 50 mL) through a 30-min pre-enrichment step utilizing the positively charged ASAB-HI complex. Comparative testing with pooled human urine and plasma samples revealed up to a 3.95-fold increase in DNA recovery compared to commercial SPE kits. Additionally, the system demonstrated up to a 6.3-fold improvement in the isolation of unstable viral RNA from clinical nasopharyngeal swabs, as well as critical microRNA biomarkers.

SIGNIFICANCE

The versatility and high efficiency of nucleic acid recovery with our ASAB-based SPE system indicate its potential to revolutionize traditional SPE methods, positioning it as a universal nucleic acid extraction platform for molecular biology research.

Functionalization of Phosphate and Tellurite Glasses and Spherical Whispering Gallery Mode Microresonators

Active whispering gallery mode resonators made as spherical microspheres doped with quantum dots or rare earth ions achieve high quality factors and are excellent candidates for biosensors capable of detecting biomolecules at low concentrations. However, to produce quantum dot-doped microspheres, new low melting temperature glasses are sought, which require surface functionalization and antibody immobilization for biosensor development. Here, we demonstrate the successful functionalization of three low melting point glasses and microspheres made of them. The glasses were made from sodium borophosphate, sodium aluminophosphate, and tellurite, and then, they were functionalized using (3-glycidyloxypropyl)trimethoxysilane in ethanol- and toluene-based protocols. Proper silanization was confirmed by energy-dispersive X-ray spectroscopy and fluorescence microscopy of an amino-modified luminescent oligonucleotide probe. Fluorescence imaging showed successful silanization for all tested samples and no degradation for aluminophosphate and tellurite glasses. The strongest signal was registered for tellurite glass samples functionalized using the toluene-based silanization protocol. This conclusion implies that this functionalization method is the most efficient and is highly recommended for future antibody immobilization and biosensing application.

Insights into the structure, functional perspective, and pathogenesis of ZIKV: an updated review

Zika virus (ZIKV) poses a serious threat to the entire world. The rapid spread of ZIKV and recent outbreaks since 2007 have caused worldwide concern about the virus. Diagnosis is complicated because of the cross-reactivity of the virus with other viral antibodies. Currently, the virus is diagnosed by molecular techniques such as RT-PCR and IgM-linked enzyme immunoassays (MAC-ELISA). Recently, outbreaks and epidemics have been caused by ZIKV, and severe clinical symptoms and congenital malformations have also been associated with the virus. Although most ZIKV infections present with a subclinical or moderate flu-like course of illness, severe symptoms such as Guillain-Barre syndrome in adults and microcephaly in children of infected mothers have also been reported. Because there is no reliable cure for ZIKV and no vaccine is available, the public health response has focused primarily on preventing infection, particularly in pregnant women. A comprehensive approach is urgently needed to combat this infection and stop its spread and imminent threat. In view of this, this review aims to present the current structural and functional viewpoints, structure, etiology, clinical prognosis, and measures to prevent this transmission based on the literature and current knowledge. Moreover, we provide thorough description of the current understanding about ZIKV interaction with receptors, and a comparative examination of its similarities and differences with other viruses.

Advances in the use of nanomaterials for nucleic acid detection in point-of-care testing devices: A review

The outbreak of the coronavirus (COVID-19) has heightened awareness of the importance of quick and easy testing. The convenience, speed, and timely results from point-of-care testing (POCT) in all vitro diagnostic devices has drawn the strong interest of researchers. However, there are still many challenges in the development of POCT devices, such as the pretreatment of samples, detection sensitivity, specificity, and so on. It is anticipated that the unique properties of nanomaterials, e.g., their magnetic, optical, thermal, and electrically conductive features, will address the deficiencies that currently exist in POCT devices. In this review, we mainly analyze the work processes of POCT devices, especially in nucleic acid detection, and summarize how novel nanomaterials used in various aspects of POCT products can improve performance, with the ultimate aims of offering new ideas for the application of nanomaterials and the overall development of POCT devices.

Synthesis and bioimaging of a BODIPY-based fluorescence quenching probe for Fe3

Iron is the main substance for maintaining life. Real-time determination of ferric ion (Fe3+) in living cells is of great significance for understanding the relationship of Fe3+ concentration changes with various physiological and pathological processes. Fluorescent probes are suitable for the detection of trace metal ions in cells due to their low toxicity and high sensitivity. In this work, a boron-dipyrromethene-based fluorescent probe (BODIPY-CL) for selective detection of Fe3+ was synthesized. The fluorescence emission of BODIPY-CL was determined at 516 nm. In a pH range of 1 to 10, the probe BODIPY-CL exhibits a quenching response to Fe3+. Meanwhile, BODIPY-CL showed a highly selective response to Fe3+ compared with 16 kinds of metal ions. The stoichiometry ratio of BODIPY-CL bound to Fe3+ was nearly 2 : 1. The fluorescence quenching response obtained by the sensor was linear with the Fe3+ concentration in the range of 0-400 μM, and the detection limit was 2.9 μM. BODIPY-CL was successfully applied to image Fe3+ in cells. This study provides a promising fluorescent imaging probe for further research on the physiological and pathological effects of Fe3+.

Detection of multiplex exosomal miRNAs for clinically accurate diagnosis of Alzheimer's disease using label-free plasmonic biosensor based on DNA-Assembled advanced plasmonic architecture

Alzheimer's disease (AD), the most common neurologic disorder, is characterized by progressive cognitive impairment. However, the low clinical significance of the currently used core AD biomarkers amyloid-beta and tau proteins remains a challenge. Recently, exosomes, found in human biological fluids, are gaining increasing attention because of their clinical significance in diagnosing of various diseases. In particular, blood-derived exosomal miRNAs are not only stable but also provide information regarding the different characteristics according to AD progression. However, quantitative and qualitative detection is difficult due to their characteristics, such as small size, low abundance, and high homology. Here, we present a DNA-assembled advanced plasmonic architecture (DAPA)-based plasmonic biosensor to accurately detect exosomal miRNAs in human serum. The designed nanoarchitecture possesses two narrow nanogaps that induce plasmon coupling; this significantly enhances its optical energy density, resulting in a 1.66-fold higher refractive-index (RI) sensitivity than nanorods at localized surface plasmon resonance (LSPR). Thus, the proposed biosensor is ultrasensitive and capable of selective single-nucleotide detection of exosomal miRNAs at the attomolar level. Furthermore, it identified AD patients from healthy controls by measuring the levels of exosomal miRNA-125b, miRNA-15a, and miRNA-361 in clinical serum samples. In particular, the combination of exosomal miRNA-125b and miRNA-361 showed the best diagnostic performance with a sensitivity of 91.67%, selectivity of 95.00%, and accuracy of 99.52%. These results demonstrate that our sensor can be clinically applied for AD diagnosis and has great potential to revolutionize the field of dementia research and treatment in the future.

Development of a gold-nanorod-based lateral flow immunoassay for a fast and dual-modal detection of C-reactive protein in clinical plasma samples

Fast and simple detection of C-reactive protein (CRP) is highly significant for the diagnosis and prognosis of inflammatory or infectious diseases. Lateral flow immunoassay has the advantages of rapid detection, simple operation and low cost, but it is usually limited by the quantitative ability and speed of data extraction. Herein, a gold-nanorod-based lateral flow immunoassay was developed to rapidly detect CRP by simultaneously monitoring the colorimetric and temperature signals. In this method, anti-CRP antibody-modified gold nanorods (GNRs) were designed as colorimetric and photothermal conversion probes. A mouse anti-CRP monoclonal antibody and goat anti-mouse IgG were used as test and control lines, respectively. Then, a lateral flow immunochromatographic strip was constructed by a sandwich-type method for detecting CRP by introducing antibody-modified GNRs, and this procedure needed less than 15 min. Finally, the detection signals can be directly observed by eyes and directly read using a thermal imager. The as-synthesized GNR showed high photothermal conversion efficiency (η = 39%) and strong localized surface plasmon resonance (LSPR) absorption. For CRP detection, the proposed immunochromatographic strip exhibited good specificity, high sensitivity, good linearity within the range of 50-10 000 ng mL-1 and a low limit of detection (LOD, 1.3 ng mL-1). This method was successfully applied for CRP detection in clinical plasma samples, and it correlated very well with the diagnostic kit of immunoturbidimetry (r = 0.96). The results indicated that the developed GNR-based immunochromatographic strip has immense potential for use as a rapid and cost-effective in vitro diagnostic kit.