New frontiers in microfluidics devices for miRNA analysis

An integrated liposome-based microfluidic strategy for rapid colorimetric analysis: A case study of microRNA-21 detection

In this study, a novel integrated liposome-based microfluidic platform combined with a smartphone was designed for the rapid colorimetric detection of microRNA-21 (miRNA-21) in real samples. The flowing surface-functionalized liposomes were first captured by nucleic acid-functionalized Au nanoparticles in the microfluidic chip. In the presence of miRNA-21, the DNA strand modified on the surface of Au nanoparticles hybridized with the target to form double-stranded products and was cleaved by duplex-specific nuclease (DSN) enzyme, causing the liposomes to be re-released. Then, as the liposomes in the colorimetric module were lysed and the "cellular" contents were released, a step-by-step "glucose-glucose oxidase-3,3',5,5'-tetramethylbenzidine (TMB)" colorimetric reaction process catalyzed by the G-quadruplex/hemin was triggered. The grayscale values were recorded and recognized by the smartphone camera for miRNA-21 analysis. The advantages of the present strategy included the portability of smartphone-based colorimetric assay, the encapsulation and transport of reactants by liposomes and the low solvent usage of microfluidic chip. Under optimal conditions, this assay exhibited a wide linear range from 1 pM to 1 nM (r2 = 0.9981), and the limit of detection of miRNA-21 was as low as 0.27 pM. Moreover, the high specificity of this strategy allowed its successful application to the rapid analysis of miRNA-21 in real blood serum samples of people with type 2 diabetes.

Sample-to-answer salivary miRNA testing: New frontiers in point-of-care diagnostic technologies

MicroRNA (miRNA), crucial non-coding RNAs, have emerged as key biomarkers in molecular diagnostics, prognosis, and personalized medicine due to their significant role in gene expression regulation. Salivary miRNA, in particular, stands out for its non-invasive collection method and ease of accessibility, offering promising avenues for the development of point-of-care diagnostics for a spectrum of diseases, including cancer, neurodegenerative disorders, and infectious diseases. Such development promises rapid and precise diagnosis, enabling timely treatment. Despite significant advancements in salivary miRNA-based testing, challenges persist in the quantification, multiplexing, sensitivity, and specificity, particularly for miRNA at low concentrations in complex biological mixtures. This work delves into these challenges, focusing on the development and application of salivary miRNA tests for point-of-care use. We explore the biogenesis of salivary miRNA and analyze their quantitative expression and their disease relevance in cancer, infection, and neurodegenerative disorders. We also examined recent progress in miRNA extraction, amplification, and multiplexed detection methods. This study offers a comprehensive view of the development of salivary miRNA-based point-of-care testing (POCT). Its successful advancement could revolutionize the early detection, monitoring, and management of various conditions, enhancing healthcare outcomes. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > Diagnostic Nanodevices.

Biporous silica nanostructure-induced nanovortex in microfluidics for nucleic acid enrichment, isolation, and PCR-free detection

Efficient pathogen enrichment and nucleic acid isolation are critical for accurate and sensitive diagnosis of infectious diseases, especially those with low pathogen levels. Our study introduces a biporous silica nanofilms-embedded sample preparation chip for pathogen and nucleic acid enrichment/isolation. This chip features unique biporous nanostructures comprising large and small pore layers. Computational simulations confirm that these nanostructures enhance the surface area and promote the formation of nanovortex, resulting in improved capture efficiency. Notably, the chip demonstrates a 100-fold lower limit of detection compared to conventional methods used for nucleic acid detection. Clinical validations using patient samples corroborate the superior sensitivity of the chip when combined with the luminescence resonance energy transfer assay. The enhanced sample preparation efficiency of the chip, along with the facile and straightforward synthesis of the biporous nanostructures, offers a promising solution for polymer chain reaction-free detection of nucleic acids.

Microarray fabrication techniques for multiplexed bioassay applications

Microarrays are powerful tools for high-throughput bioassays that can extract information from tens of thousands of micro-spots consisting of biomolecules. This information is invaluable to many applications, such as drug discovery and disease diagnostics. Different applications of these microarrays need spots of different shapes, sizes, and chemistries to achieve their goals. Micro/nano-fabrication techniques are used to make microarrays with different feature structures and array densities for required assay procedures. Understanding these fabrication methods is essential to creating an effective microarray. The purpose of this article is to critically review fabrication methods used in recent microarray-based bioassay studies. We summarized commonly used microarray fabrication techniques and filled the gap in recent literature on relevant topics. We discussed recent examples of how microarrays were fabricated and used in a variety of bioassays. Specifically, we examined microarray printing, various microlithography techniques, and microfluidics-based microarray fabrication. We evaluated how their application shaped the fabrication methods and compared their performance based on different applications. In the end, we discussed current challenges and outlined potential future directions. This review addressed the gap in literature and provided important insights for choosing appropriate fabrication techniques towards different applications.

Endogenous miRNA and K+ Co-Activated Dynamic Assembly of DNA Coacervates for Intracellular miRNA Imaging and Mitochondrial Intervention

Intracellular dynamic assembly of DNA structures may be beneficial for the development of multifunctional nanoplatforms for the regulation of cell behaviors, providing new strategies for disease diagnosis and intervention. Herein, we propose the dynamic assembly of DNA coacervates in living cells triggered by miRNA-21 and K+, which can be used for both miRNA imaging and mitochondrial intervention. The rationale is that miRNA-21 can trigger the hybridization chain reaction to generate G-quadruplex precursors, and K+ can mediate the assembly of G-quadruplex-based coacervates, allowing the colorimetric detection of miRNA-21 ranging from 10 pM to 10 μM. Moreover, the as-formed DNA coacervates can specifically target mitochondria in MCF-7 breast cancer cells using the MCF-7 cell membrane as delivery carriers, which further act as an anionic shielding to inhibit communication between mitochondria and environments, with a significant inhibitory effect on ATP production and cellular migration behaviors. This work provides an ideal multifunctional nanoplatform for rationally interfering with cellular metabolism and migration behaviors through the dynamic assembly of DNA coacervates mediated by endogenous molecules, which has a large number of potential applications in the biomedical field, especially theranostics for cancer metastasis.

Mitochondrial miRNA as epigenomic signatures: Visualizing aging-associated heart diseases through a new lens

Aging bears many hard knocks, but heart disorders earn a particular allusion, being the most widespread. Cardiovascular diseases (CVDs) are becoming the biggest concern to mankind due to sundry health conditions directly or indirectly related to heart-linked abnormalities. Scientists know that mitochondria play a critical role in the pathophysiology of cardiac diseases. Both environment and genetics play an essential role in modulating and controlling mitochondrial functions. Even a minor abnormality may prove detrimental to heart function. Advanced age combined with an unhealthy lifestyle can cause most cardiomyocytes to be replaced by fibrotic tissue which upsets the conducting system and leads to arrhythmias. An aging heart encounters far more heart-associated comorbidities than a young heart. Many state-of-the-art technologies and procedures are already being used to prevent and treat heart attacks worldwide. However, it remains a mystery when this heart bomb would explode because it lacks an alarm. This calls for a novel and effective strategy for timely diagnosis and a sure-fire treatment. This review article provides a comprehensive overture of prospective potentials of mitochondrial miRNAs that predict complicated and interconnected pathways concerning heart ailments and signature compilations of relevant miRNAs as biomarkers to plot the role of miRNAs in epigenomics. This article suggests that analysis of DNA methylation patterns in age-associated heart diseases may determine age-impelled biomarkers of heart disease.

Combining 3D Printing and Microfluidic Techniques: A Powerful Synergy for Nanomedicine

Nanomedicine has grown tremendously in recent years as a responsive strategy to find novel therapies for treating challenging pathological conditions. As a result, there is an urgent need to develop novel formulations capable of providing adequate therapeutic treatment while overcoming the limitations of traditional protocols. Lately, microfluidic technology (MF) and additive manufacturing (AM) have both acquired popularity, bringing numerous benefits to a wide range of life science applications. There have been numerous benefits and drawbacks of MF and AM as distinct techniques, with case studies showing how the careful optimization of operational parameters enables them to overcome existing limitations. Therefore, the focus of this review was to highlight the potential of the synergy between MF and AM, emphasizing the significant benefits that this collaboration could entail. The combination of the techniques ensures the full customization of MF-based systems while remaining cost-effective and less time-consuming compared to classical approaches. Furthermore, MF and AM enable highly sustainable procedures suitable for industrial scale-out, leading to one of the most promising innovations of the near future.

Formation of miRNA Nanoprobes-Conjugation Approaches Leading to the Functionalization

Recently, microRNAs (miRNA) captured the interest as novel diagnostic and prognostic biomarkers, with their potential for early indication of numerous pathologies. Since miRNA is a short, non-coding RNA sequence, the sensitivity and selectivity of their detection remain a cornerstone of scientific research. As such, methods based on nanomaterials have emerged in hopes of developing fast and facile approaches. At the core of the detection method based on nanotechnology lie nanoprobes and other functionalized nanomaterials. Since miRNA sensing and detection are generally rooted in the capture of target miRNA with the complementary sequence of oligonucleotides, the sequence needs to be attached to the nanomaterial with a specific conjugation strategy. As each nanomaterial has its unique properties, and each conjugation approach presents its drawbacks and advantages, this review offers a condensed overview of the conjugation approaches in nanomaterial-based miRNA sensing. Starting with a brief recapitulation of specific properties and characteristics of nanomaterials that can be used as a substrate, the focus is then centered on covalent and non-covalent bonding chemistry, leading to the functionalization of the nanomaterials, which are the most commonly used in miRNA sensing methods.