Capping Gold Nanoparticles to Achieve a Protein-like Surface for Loop-Mediated Isothermal Amplification Acceleration and Ultrasensitive DNA Detection

Nanotechnology-Enabled PCR with Tunable Energy Dynamics

This Perspective elucidates the transformative impacts of advanced nanotechnology and dynamic energy systems on the polymer chain reaction (PCR), a cornerstone technique in biomedical research and diagnostic applications. Since its invention, the optimization of PCR-specifically its efficiency, specificity, cycling rate, and detection sensitivity-has been a focal point of scientific exploration. Our analysis spans the modulation of PCR from both material and energetic perspectives, emphasizing the intricate interplay between PCR components and externally added entities such as molecules, nanoparticles (NPs), and optical microcavities. We begin with a foundational overview of PCR, detailing the basic principles of PCR modulation through molecular additives to highlight material-level interactions. Then, we delve into how NPs, with their diverse material and surface properties, influence PCR through interface interactions and hydrothermal conduction, drawing parallels to molecular behaviors. Additionally, this Perspective ventures into the energetic regulation of PCR, examining the roles of electromagnetic radiation and optical resonators. We underscore the advanced capabilities of optical technologies in PCR regulation, characterized by their ultrafast, residue-free, and noninvasive nature, alongside label-free detection methods. Notably, optical resonators present a pioneering approach to control PCR processes even in the absence of light, targeting the often-overlooked water component in PCR. By integrating discussions on photocaging and vibrational strong coupling, this review presents innovative methods for the precise regulation of PCR processes, envisioning a new era of PCR technology that enhances both research and clinical diagnostics. The synergy between nanotechnological enhancements and energy dynamics not only enriches our understanding of PCR but also opens new avenues for developing rapid, accurate, and efficient PCR systems. We hope that this Perspective will inspire further innovations in PCR technology and guide the development of next-generation clinical detection instruments.

A label-free and rapid fluorometric strategy for microRNA detection using CRISPR-Cas12a coupled with copper nanoparticles

CRISPR-Cas12a with robust trans-cleavage activity were employed to mitigate background fluorescence signal, achieving sensitive detection of miRNA-21. The activation of trans-cleavage activity of Cas12a was achieved by utilizing cDNA as a trigger. Upon the presence of target miRNA-21, cDNA hybridizes with it forming a DNA/RNA double-stranded structure. Exonuclease III (ExoIII) facilitates the degradation of cDNA, releasing the target for subsequent cycles. Due to cDNA degradation, the trans-cleavage activity of Cas12a remains unactivated and does not disrupt the synthesis template of copper nanoparticles. Addition of Cu2+ and AA leads to the formation of highly fluorescent copper nanoparticles. Conversely, in absence of miRNA-21, intact cDNA activates trans-cleavage activity of Cas12a, resulting in degradation of the synthesis template and failure in synthesizing fluorescent copper nanoparticles. This method exhibits excellent selectivity with a low limit of detection (LOD) at 5 pM. Furthermore, we successfully applied this approach to determine miRNA-21 in cell lysates and human serum samples, providing a new approach for sensitive determination of biomarkers in biochemical research and disease diagnosis.

Detection ofmiRNA-378based on a catalytic hairpin self-assembly reaction combined with gold nanoparticle colorimetry

Recent studies have shown that abnormalmiRNA-378expression is a rule, rather than an exception, in cervical cancer and can be used as a diagnostic and prognostic biomarker to assess tumor initiation. In this study, we developed a general, sensitive strategy for detectingmiRNA-378using catalytic hairpin self-assembly (CHA) combined with gold nanoparticles (AuNP) colorimetry. The presence ofmiRNA-378triggers the repeated self-assembly of two designed hairpin DNAs (H1 and H2) into dsDNA polymers, which leads to changes in the surface plasmon resonance absorption band and the macroscopic color of the AuNP colloids due to the formation of nanoparticle-DNA conjugates. This experimental phenomenon can be observed by ultraviolet-visible spectrometry or even with the naked eye. Using this method,miRNA-378could be quantitatively detected at the picomolar level (as low as 20.7 pM). Compared with traditional methods, such as quantitative polymerase chain reaction and RNA blotting, this strategy has a simple operation, low cost, and high sensitivity and selectivity, and thus, exhibits significant potential for miRNA detection.

Improved Catalytic Activity of Spherical Nucleic Acid Enzymes by Hybridization Chain Reaction and Its Application for Sensitive Analysis of Aflatoxin B1

Conventional spherical nucleic acid enzymes (SNAzymes), made with gold nanoparticle (AuNPs) cores and DNA shells, are widely applied in bioanalysis owing to their excellent physicochemical properties. Albeit important, the crowded catalytic units (such as G-quadruplex, G4) on the limited AuNPs surface inevitably influence their catalytic activities. Herin, a hybridization chain reaction (HCR) is employed as a means to expand the quantity and spaces of G4 enzymes for their catalytic ability enhancement. Through systematic investigations, we found that when an incomplete G4 sequence was linked at the sticky ends of the hairpins with split modes (3:1 and 2:2), this would significantly decrease the HCR hybridization capability due to increased steric hindrance. In contrast, the HCR hybridization capability was remarkably enhanced after the complete G4 sequence was directly modified at the non-sticky end of the hairpins, ascribed to the steric hindrance avoided. Accordingly, the improved SNAzymes using HCR were applied for the determination of AFB1 in food samples as a proof-of-concept, which exhibited outstanding performance (detection limit, 0.08 ng/mL). Importantly, our strategy provided a new insight for the catalytic activity improvement in SNAzymes using G4 as a signaling molecule.

Ultrasensitive and visual detection of genetically modified crops using two primers-induced cascade exponential amplification assay

The increased global cultivation area of genetically modified (GM) crops has caused severe controversies over potential health and environmental risks worldwide. There is an urgent need to verify even trace amount of a particular GM material in products. Herein, a two primers-induced cascade exponential amplification reaction combined with cationic conjugated polymers (CCPs)-based visual detection method is developed for rapid and ultrasensitive detection of GM crops. This method only uses two primers to specifically recognize the four regions of the target gene, which is easier for primer design and probably more suitable for the detection of shorter targets. By integrating the two exponential amplification reactions, as low as 5 pg genomic DNA from GM maize can be accurately detected, which is more sensitive than the single amplification-based methods. Taking advantage of the efficient fluorescence resonance energy transfer (FRET) between CCPs and the commercial fluorescent dye SYBR Green I (SG), our method can differentiate as low as 0.01 % GM maize from a large amount of non-GM maize, which is the most accurate method so far. By changing the two primers according to target gene, our method can be modified to the detection of any other GM materials, indicating that our method is promising to be applied in other GM materials-related testing and screening system.

Precise Detection of Viral RNA by Programming Multiplex Rolling Circle Amplification and Strand Displacement

Detection of viral infections (e.g., SARS-CoV-2) with high precision is critical to disease control and treatment. There is an urgent need to develop point-of-care detection methods to complement the gold standard laboratory-based PCR assay with comparable sensitivity and specificity. Herein, we developed a method termed mCAD to achieve ultraspecific point-of-care detection of SARS-CoV-2 RNA while maintaining high sensitivity by programming multiplex rolling circle amplification and toehold-mediated strand displacement reactions. RCA offers sufficient amplification of RNA targets for subsequent detection. Most importantly, a multilayer of detection specificity is implemented into mCAD via sequence-specific hybridization of nucleic acids across serial steps of this protocol to fully eliminate potential false-positive detections. Using mCAD, we demonstrated a highly specific, sensitive, and convenient visual detection of SARS-CoV-2 RNA from both synthetic and clinical samples, exhibiting performance comparable to qPCR. We envision that mCAD will find its broad applications in clinical prospects for nucleic acid detections readily beyond SARS-CoV-2 RNA.

Hydrogel Digital LAMP with Suppressed Nonspecific Amplification for Rapid Diagnostics of Fungal Disease in Fresh Fruits

Fungal disease, mainly caused by Alternaria alternata infection, can generate severe economic losses and health hazards. However, rapid nucleic acid test without nonspecific reaction still remains challenging. Here, we reported the hydrogel digital loop-mediated isothermal amplification (HdLAMP) with suppressed nonspecific amplification for rapid diagnosis of fungi in fresh fruits. The introduction of hydrogel offered a simple platform to achieve absolute quantification. By breaking the 3'end G-C anchor, the nonspecific amplification of primers could be suppressed, while the specific positive reaction in HdLAMP was not affected. This method could be applied for A. alternata detection in 9 min with excellent performances in speed, specificity, reproducibility, sensitivity, and detection limit down to a single copy. Finally, the real diseased jujubes during postharvest storage were successfully diagnosed as an A. alternata infection. HdLAMP promotes the molecular diagnosis of fungal diseases and broadens the application of hydrogels in the agricultural and food industry.

CRISPR-Cas12a Coupled with DNA Nanosheet-Amplified Fluorescence Anisotropy for Sensitive Detection of Biomolecules

DNA nanosheets (DNSs) have been utilized effectively as a fluorescence anisotropy (FA) amplifier for biosensing. But, their sensitivity needs to be further improved. Herein, CRISPR-Cas12a with strong trans-cleavage activity was utilized to enhance the FA amplification ability of DNSs for the sensitive detection of miRNA-155 (miR-155) as a proof-of-principle target. In this method, the hybrid of the recognition probe of miR-155 (T1) and a blocker sequence (T2) was immobilized on the surface of magnetic beads (MBs). In the presence of miR-155, T2 was released by a strand displacement reaction, which activated the trans-cleavage activity of CRISPR-Cas12a. The single-stranded DNA (ssDNA) probe modified with a carboxytetramethylrhodamine (TAMRA) fluorophore was cleaved in large quantities and could not bind to the handle chain on DNSs, inducing a low FA value. In contrast, in the absence of miR-155, T2 could not be released and the trans-cleavage activity of CRISPR-Cas12a could not be activated. The TAMRA-modified ssDNA probe remained intact and was complementary to the handle chain on the DNSs, and a high FA value was obtained. Thus, miR-155 was detected through the obviously decreased FA value with a low limit of detection (LOD) of 40 pM. Impressively, the sensitivity of this method was greatly improved about 322 times by CRISPR-Cas12a, confirming the amazing signal amplification ability of CRISPR-Cas12a. At the same time, the SARS-CoV-2 nucleocapsid protein was detected by the strategy successfully, indicating that this method was general. Moreover, this method has been applied in the analysis of miR-155 in human serum and the lysates of cells, which provides a new avenue for the sensitive determination of biomarkers in biochemical research and disease diagnosis.

Miniature Hierarchical DNA Hybridization Circuit for Amplified Multiplexed MicroRNA Imaging

Accurate diagnosis requires the development of multiple-guaranteed DNA circuits. Nevertheless, for reliable multiplexed molecular imaging, existing DNA circuits are limited by poor cell-delivering homogeneity due to their cumbersome and dispersive reactants. Herein, we developed a compact-yet-efficient hierarchical DNA hybridization (HDH) circuit for in situ simultaneous analysis of multiple miRNAs, which could be further exploited for specifically discriminating cancer cells from normal ones. By integrating the traditional hybridization chain reaction and catalytic hairpin assembly reactants into two highly organized hairpins, the HDH circuit is fitted with condensed components and multiple response domains, thus permitting the programmable multiple microRNA-guaranteed sequential activations and the localized cascaded signal amplification. The synergistic multi-recognition and amplification features of the HDH circuit facilitate the magnified detection of multiplex endogenous miRNAs in living cells. The in vitro and cellular imaging experimental results revealed that the HDH circuit displayed a reliable sensing performance with high selective cell-identification capacity. We anticipate that this compact design can provide a powerful toolkit for accurate diagnostics and pathological evolution.

Ultrafast and absolute quantification of SARS-CoV-2 on food using hydrogel RT-LAMP without pre-lysis

With rapid growing of environmental contact infection, more and more attentions are focused on the precise and absolute quantification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus on cold chain foods via point-of-care test (POCT). In this work, we propose a hydrogel-mediated reverse transcription loop-mediated isothermal amplification (RT-LAMP) for ultrafast and absolute quantification of SARS-CoV-2. Cross-linked hydrogel offers opportunities for digital single molecule amplification in nanoconfined spaces, facilitating the virus lysis, RNA reverse transcription and amplification process, which is about 3.4-fold faster than conventional bulk RT-LAMP. Ultrafast quantification of SARS-CoV-2 is accomplished in 15 min without virus pre-lysis and RNA extraction. The sensitivity can accurately quantify SARS-CoV-2 down to 0.5 copy/μL. Furthermore, the integrated system has an excellent specificity, reproducibility and storage stability, which can be also used to test SARS-CoV-2 on various cold chain fruits. The developed ultrafast and simple hydrogel RT-LAMP will be an enormous potential for surveillance of virus or other hazardous microbes in environmental, agricultural and food industry.