Rapid and sensitive detection of microRNA via the capture of fluorescent dyes-loaded albumin nanoparticles around functionalized magnetic beads

Development of a Novel System Consisting of a Reductase-Like Nanozyme and the Reaction of Resazurin and Ammonia Borane for Sensitive Fluorometric Sensing

We report a novel system consisting of a redox reaction and a highly efficient reductase-like nanozyme, silica-palladium nanoparticles (Pd@SiO2 NPs), as a novel detection platform for fluorometric sensing. In a proof-of-concept demonstration using an oligonucleotide as the detection target, a glass fiber-based sensor is fabricated by covalently conjugating two oligo probes, which are complementary to the adjacent segments of the target oligonucleotide, on Pd@SiO2 NPs and glass fiber, respectively. In the presence of the target oligonucleotide, the two probes are drawn together by the target through sequence-specific hybridization, bringing the Pd@SiO2 NPs to the glass fiber. When the glass fiber is subsequently immersed in a mixture of resazurin and ammonia borane solution, the Pd@SiO2 NPs on the glass fiber trigger the catalytic conversion of resazurin (blue, slightly fluorescent) to resorufin (pink, highly fluorescent) with massive signal amplification, indirectly signaling the presence of the target oligonucleotide. We show that the glass fiber-based fluorometric sensor can detect a target oligonucleotide associated with the BRAF mutation linearly in the concentration range of 20 to 400 pM with a detection limit (LOD) of 15 pM and the specificity to differentiate targets with single-base difference. These results demonstrate a new frontier for the development of a sensitive, specific, and inexpensive nonenzyme-based fluorometric sensing platform as an alternative to conventional enzyme-based assays.

Phage-based peptides for pancreatic cancer diagnosis and treatment: alternative approach

Pancreatic cancer is a devastating disease with a high mortality rate and a lack of effective therapies. The challenges associated with early detection and the highly aggressive nature of pancreatic cancer have limited treatment options, underscoring the urgent need for better disease-modifying therapies. Peptide-based biotherapeutics have become an attractive area of research due to their favorable properties such as high selectivity and affinity, chemical modifiability, good tissue permeability, and easy metabolism and excretion. Phage display, a powerful technique for identifying peptides with high affinity and specificity for their target molecules, has emerged as a key tool in the discovery of peptide-based drugs. Phage display technology involves the use of bacteriophages to express peptide libraries, which are then screened against a target of interest to identify peptides with desired properties. This approach has shown great promise in cancer diagnosis and treatment, with potential applications in targeting cancer cells and developing new therapies. In this comprehensive review, we provide an overview of the basic biology of phage vectors, the principles of phage library construction, and various methods for binding affinity assessment. We then describe the applications of phage display in pancreatic cancer therapy, targeted drug delivery, and early detection. Despite its promising potential, there are still challenges to be addressed, such as optimizing the selection process and improving the pharmacokinetic properties of phage-based drugs. Nevertheless, phage display represents a promising approach for the development of novel targeted therapies in pancreatic cancer and other tumors.

Ratiometric Fluorescent Biosensor Based on Self-Assembled Fluorescent Gold Nanoparticles and Duplex-Specific Nuclease-Assisted Signal Amplification for Sensitive Detection of Exosomal miRNA

The sensitive detection of cancer-associated exosomal microRNAs shows enormous potential in cancer diagnosis. Herein, a ratiometric fluorescent biosensor based on self-assembled fluorescent gold nanoparticles (Au NPs) and duplex-specific nuclease (DSN)-assisted signal amplification was fabricated for sensitive detection of colorectal cancer (CRC)-associated exosomal miR-92a-3p. In this biosensing system, the hairpin DNA modified with sulfhydryl and fluorescent dye Atto-425 at both ends is conjugated to fluorescent Au NPs through Au-S bonds, resulting in the quenching of Atto-425. The miR-92a-3p can open the hairpin of DNA and forms an miR-92a-3p/DNA heteroduplex, triggering the specific cleavage of DSN for the DNA in the heteroduplex. As a result, Atto-425 leaves the fluorescent Au NPs and recovers the fluorescence emission. The released miR-92a-3p can hybridize with another hairpin DNA and lead to a stronger fluorescence recovery of Atto-425 to form a signal amplification cycle. The stable fluorescence of Au NPs and the changing fluorescence of Atto-425 constitute a ratiometric fluorescent system reflecting the concentration of miR-92a-3p. This biosensor exhibits excellent specificity and can distinguish CRC patients from healthy individuals by detecting miR-92a-3p extracted from clinical exosome samples, showing the potential in CRC diagnosis.

Graphene-oxide-based bioassay for the fluorometric determination of agrC gene transcription in methicillin-resistant Staphylococcus aureus that uses nicking-enzyme-assisted target recycling and a hybridization chain reaction

Herein, we report the development of a graphene-oxide-based (GO-based) fluorescent bioassay for determining agrC gene transcription (mRNA) in methicillin-resistant Staphylococcus aureus (MRSA). The design is based on nicking-enzyme-assisted (Nb.BbvcI-assisted) target recycling amplification (NATR) and a hybridization chain reaction (HCR). The system consists of a helper probe (HP), a molecular beacon (MB) probe, four hairpins, and endonuclease Nb.BbvcI, which plays a role in target recycling and signal amplification. In the absence of the target, all of the carboxyfluorescein-labeled (FAM-labeled) hairpins are adsorbed through π-stacking interactions onto the surface of GO, resulting in FAM signal quenching. When the target is added, three nucleic acid chains hybridize together to form a triple complex that is recognized by Nb.BbvCI. The MB probe is then cleaved by Nb.BbvCI to generate an HP/target complex and two new DNA fragments; the former is hybridized to another MB probe and enters the next round of reaction. The two newly reproduced DNA fragments induce a HCR with the assistance of hairpins 1-4 to create double-stranded DNA (dsDNA) products. These dsDNA products are repelled by GO and generate strong fluorescence at excitation/emission wavelengths of 480/514 nm. Importantly, synergy between FAM and the dsDNA-SYBR Green I duplex structure led to significantly amplified fluorescence and enhanced sensitivity. The bioassay showed a detection limit of 7.5 fM toward the target and a good linearity in the 10 fM to 100 pM range. The developed method was applied to monitor biofilm formation and study the mechanism of drug action, with satisfactory results obtained.

Interaction between miR4749 and Human Serum Albumin as Revealed by Fluorescence, FRET, Atomic Force Spectroscopy and Computational Modelling

The interaction of Human Serum Albumin (HSA) with the microRNA, miR4749, was investigated by Atomic Force Spectrscopy (AFS), static and time-resolved fluorescence spectroscopy and by computational methods. The formation of a HSA/miR4749 complex with an affinity of about 10⁴ M⁻¹ has been assessed through a Stern–Volmer analysis of steady-state fluorescence quenching of the lone Trp residue (Trp214) emission of HSA. Förster Resonance Energy Transfer (FRET) measurements of fluorescence lifetime of the HSA/miR4749 complex were carried out in the absence and in the presence of an acceptor chromophore linked to miR4749. This allowed us to determine a distance of 4.3 ± 0.5 nm between the lone Trp of HSA and the dye bound to miR4749 5p-end. Such a distance was exploited for a screening of the possible binding sites between HSA and miR4749, as predicted by computational docking. Such an approach, further refined by binding free energy calculations, led us to the identification of a consistent model for the structure of the HSA/miR4749 complex in which a positively charged HSA pocket accommodates the negatively charged miRNA molecule. These results designate native HSA as a suitable miRNA carrier under physiological conditions for delivering to appropriate targets.

Recent advances in catalytic hairpin assembly signal amplification-based sensing strategies for microRNA detection

Accumulative evidences have indicated that abnormal expression of microRNAs (miRNAs) is closely associated with many health disorders, making them be regarded as potentialbiomarkers for early clinical diagnosis. Therefore, it is extremely necessary to develop a highly sensitive, specific and reliable approach for miRNA analysis. Catalytic hairpin assembly (CHA) signal amplification is an enzyme-free toehold-mediated strand displacement method, exhibiting significant potential in improving the sensitivity of miRNA detection strategies. In this review, we first describe the potential of miRNAs as disease biomarkers and therapeutics, and summarize the latest advances in CHA signal amplification-based sensing strategies for miRNA monitoring. We describe the characteristics and mechanism of CHA signal amplification and classify the CHA-based miRNA sensing strategies into several categories based on the "signal conversion substance", including fluorophores, enzymes, nanomaterials, and nucleotide sequences. Sensing performance, limit of detection, merits and disadvantages of these miRNA sensing strategies are discussed. Moreover, the current challenges and prospects are also presented.

Simple Tripedal DNA Walker Prepared by Target-Triggered Catalytic Hairpin Assembly for Ultrasensitive Electrochemiluminescence Detection of MicroRNA

In contrast to common DNA walkers, multipedal DNA walkers exhibit larger walking area and faster walking kinetics and provide increased amplification efficiency. Consequently, they have received a considerable amount of attention in biosensing. However, most of them are synthesized by immobilizing multiple DNA walking strands on the surface of Au nanoparticles, which is tedious and time-consuming. Simple preparation of multipedal DNA walkers remains a challenge. Herein, we adopted a simple enzyme-free target-triggered catalytic hairpin assembly (CHA) circuit to synthesize a tripedal DNA walker. By walking on a DNA track-functionalized electrode, a sensitive electrochemiluminescence DNA nanomachine biosensor was constructed for sensing miRNA-21. The DNA walker was powered by toehold-mediated strand displacement; the whole process did not need the assistance of enzymes, thus avoiding tedious procedures and enzyme degradation under unfavorable environmental conditions. Specifically, a superior detection limit of 4 aM and a broad linear range of 10 aM to 1 pM were achieved. This CHA-tripedal DNA walker biosensor was then applied for the detection of miRNA-21 in human serum and showed high selectivity and excellent reproducibility, demonstrating its practical application in bioanalysis. In particular, the Y-shaped tripedal DNA walker comes from the DNA circuit, which makes the approach ideally suited for biosensing of small nucleic acid targets.

Photo-affinity pulling down of low-affinity binding proteins mediated by post-translational modifications

Weak and transient protein-protein interactions (PPIs) mediated by the post-translational modifications (PTMs) play key roles in biological systems. However, technical challenges to investigate the PTM-mediated PPIs have impeded many research advances. In this work, we develop a photo-affinity pull-down assay method to pull-down low-affinity binding proteins, thus for the screen of PTM-mediated PPIs. In this method, the PTM-mediated non-covalent interactions can be converted to the covalent interactions by the photo-activated linkage, so as to freeze frame the low-affinity binding interactions. The fabricated photo-affinity magnetic beads (PAMBs) ensure high specificity and resolution to capture the interacted proteins. Besides, the introduction of PEG passivation layer on PAMB has significantly reduced the non-specific interaction as compared to the traditional pull-down assay. For proof-of-concept, by using this newly developed assay method, we have identified a set of proteins that can interact with a specific methylation site on Flap Endonuclease 1 (FEN1) protein. Less interfering proteins (decreased over 80%) and more proteins sub-classes are profiled as compared to the traditional biotin-avidin pull-down system. Therefore, this new pull-down method may provide a useful tool for the study of low-affinity PPIs, and contribute to the discovery of potential targets for renewed PTM-mediated interactions that is fundamentally needed in biomedical research.

Mass spectrometric quantification of microRNAs in biological samples based on multistage signal amplification

Quantification of miRNAs based on multistage signal amplification and LC-ESI-MS/MS.

Double-signal mode based on metal–organic framework coupled cascaded nucleic acid circuits for accurate and sensitive detection of serum circulating miRNAs

A double-signal mode based on metal–organic framework coupled cascaded nucleic acid circuits was developed for the accurate and sensitive detection of serum circulating miRNAs.

Recent advances on nanomaterials-based fluorimetric approaches for microRNAs detection

MicroRNAs are types of small single-stranded endogenous highly conserved non-coding RNAs, which play main regulatory functions in a wide range of cellular and physiological events, such as proliferation, differentiation, neoplastic transformation, and cell regeneration. Recent findings have proved a close association between microRNAs expression and the development of many diseases, indicating the importance of microRNAs as clinical biomarkers and targets for drug discovery. However, due to a number of prominent characteristics like small size, high sequence similarity and low abundance, sensitive and selective identification of microRNAs has rather been a hardship through routine traditional assays, including quantitative polymerase chain reaction, microarrays, and northern blotting analysis. More recently, the soaring progression in nanotechnology and fluorimetric methodologies in combination with nanomaterials have promised microRNAs detection with high sensitivity, efficiency and selectivity, excellent reproducibility and lower cost. Therefore, this review will represent an overview of latest advances in microRNAs detection through nanomaterials-based fluorescent methods, like gold nanoparticles, silver and copper nanoclusters, graphene oxide, and magnetic silicon nanoparticles.

Avenues Toward microRNA Detection In Vitro: A Review of Technical Advances and Challenges

Over the decades, the biological role of microRNAs (miRNAs) in the post-transcriptional regulation of gene expression has been discovered in many cancer types, thus initiating the tremendous expectation of their application as biomarkers in the diagnosis, prognosis, and treatment of cancer. Hence, the development of efficient miRNA detection methods in vitro is in high demand. Extensive efforts have been made based on the intrinsic properties of miRNAs, such as low expression levels, high sequence homology, and short length, to develop novel in vitro miRNA detection methods with high accuracy, low cost, practicality, and multiplexity at point-of-care settings. In this review, we mainly summarized the newly developed in vitro miRNA detection methods classified by three key elements, including biological recognition elements, additional micro-/nano-materials and signal transduction/readout elements, their current challenges and further applications are also discussed.

A fluorescent nanoparticle probe based on sugar-substituted tetraphenylethene for label-free detection of galectin-3

An AIE-active nanoparticle probe decorated with galactoside residues is designed and developed for label-free detection of galectin-3 with enhanced specificity, showing promising applications in cancer diagnoses.

A signal amplification system constructed by bi-enzymes and bi-nanospheres for sensitive detection of norepinephrine and miRNA

Achieving the enhanced sensitivity and stability is always the pursuit for the fabrication of enzymatic biosensors. However, their sensitivity was still restricted by the fluctuant detection target (e.g. concentration), complex detection environment and limited recognition capability of enzymes. Herein, an effective and facile approach was designed to construct a bi-enzymatic and bi-nanospherical signal amplification system for fabrication of biosensors based on the designed polydopamine(PDA)-laccase@Au-glucose dehydrogenase. Therein, laccase-catalytic polymerized PDA nanoparticles (NPs) provided the supporting matrix for immobilization of laccase and AuNPs. The AuNPs with good conductivity and large surface area were used not only as a platform for enhanced loading capacity of glucose dehydrogenase but also as a conducting medium for electron transfer acceleration between enzymes and electrode. Moreover, the coordinated catalysis of bi-enzymes (laccase and glucose dehydrogenase) could avoid the fluctuated concentration of detection target (e.g. norepinephrine), while the application of bi-nanospheres loaded with large amount of enzymes could effectively amplify the signal of biosensors. Taking advantages of these merits, the as-prepared biosensors showed preeminent reproducibility, larger detection range from 0.5 nM to 0.5 μM, and lower detection limit of 0.07 nM (S/N = 3) for the norepinephrine detection. Besides, the constructed PDA-laccase@Au-glucose dehydrogenase was also successfully applied as the sensing probes for the detection of microRNA (miRNA), especially for single-nucleotide mismatched miRNA via specific recognition.

Carotid Plaque Rupture Is Accompanied by an Increase in the Ratio of Serum circR-284 to miR-221 Levels

BACKGROUND

Atherosclerotic plaque rupture is accompanied by an acute decrease in the carotid plaque expression of micro-RNAs (miRs)-221 and miR-222. Circular RNA (circR)-284 is a potential inhibitor of miR-221/miR-222 activity. We aimed to determine whether changes in the serum levels of these noncoding RNAs are observed in patients with asymptomatic high-grade carotid disease versus patients with acutely symptomatic carotid disease and recent ischemic stroke. Additionally, we tested the use of functionally related noncoding RNA pairs to enhance the discriminatory power of noncoding RNAs as circulating biomarkers.

METHODS AND RESULTS

Serum levels of miR-221, miR-222, miR-145, and circR-284 were measured in 24 asymptomatic (asymptomatic) and 17 acutely symptomatic patients ([urgent] ischemic cerebrovascular event within the previous 5 days) undergoing carotid endarterectomy. miR-221 was significantly lower, whereas circR-284 was elevated in the serum of the urgent compared with the asymptomatic group. The ratio of serum circR-284:miR-221 was significantly elevated in the urgent group (P=0.0002) and exhibited favorable characteristics as a biomarker indicative of carotid plaque rupture and stroke. A validation study in 112 patients (47 asymptomatic, 41 urgent, and 24 patients with a cerebrovascular event between 5 and 180 days of the carotid endarterectomy [symptomatic]) confirmed elevation of serum circR-284:miR-221 uniquely in the urgent group (P<0.001) and favorable sensitivity and specificity for detecting plaque rupture and stroke.

CONCLUSIONS

Serum circR-284:miR-221 has potential as a diagnostic biomarker of carotid plaque rupture and stroke. Moreover, we demonstrate the use of functionally related pairs of circulating noncoding RNAs as biomarkers in cardiovascular disease.

Sensitive detection of intracellular microRNA based on a flowerlike vector with catalytic hairpin assembly

A flowerlike nanovector with horn-shaped tips is developed for in situ detection of intracellular microRNA with multiple signal outputs.