A capillary-based microfluidic chip with the merits of low cost and easy fabrication for the rapid detection of acute myocardial infarction

A capillary-based microfluidic chip prepared via multiple coating and used for a multiplex immunoassay

Point-of-care testing (POCT) is a fast, simple and portable procedure that is capable of multiplexed real-time detection. Microfluidic chips have emerged as an extremely promising pathway for POCT owing to their revolutionary improvements in integration and portability. However, traditional microfluidic chips still have many disadvantages, such as high costs and technical barriers for fabrication, which are incompatible with batch production and limit their development in the field of POCT. When the antibody array was prepared along the microchannel, the different antibodies were introduced into the microchannel from the same inlet and then resulted in the serious cross-contamination. In this study, a capillary-based microfluidic chip prepared via multiple coating was developed and used for a multiplex immunoassay. The array of capture antibodies was created by repeatedly blocking and conjugating the various capture antibodies onto the inner surface of capillary. The cross-contamination between the capture antibodies alongside the capillary was less than 5 %, which was proven by the experimental data and theoretical derivation. Two capillaries were encased in the plastic shell and then prepared for the multiplex detection of multiple biomarkers. The detection of myoglobin, cardiac troponin I, and creatine kinase-MB proved the viability and analytical capabilities of the capillary-based microfluidic chip, with the limit of detection of 1.0 ng/mL, 0.5 ng/mL and 1.0 ng/mL respectively. The capillary-based microfluidic chip prepared via multiple coating is compatible with batch production and shows promise for the portable and affordable detection of a range of acute diseases due to its low cost and simple fabrication.

Label-Free Liquid Crystal Biosensor Based on Split Aptamers for Detecting Serum Myoglobin

Myoglobin (Mb) is a critical cytoplasmic heme protein and one of the earliest detectable biomarkers following acute myocardial infarction (MI). The rapid and precise detection of serum Mb holds significant clinical value. This study capitalizes on the advantages of a split aptamer (Apt) sequence, which is short and effectively minimizes false-positive signals caused by the secondary structure of the probe. It constructs a "sandwich"-structured liquid crystal biosensor with an "Apt-target molecule-Apt" configuration for the label-free detection of serum Mb. Mb Apt fragments were immobilized on the surface of a glass substrate as capture probes (CP) by using triethoxybutanal silane (TEA) linker molecules. When Mb is present, the other Apt fragment, the signal probe (SP), specifically binds and reassociates with the CP, restoring the original stem-loop structure of Apt, thereby inducing a change in the alignment of 5CB liquid crystal molecules. This change leads to variations in the brightness and color of the optical signal in the polarizing microscope image, facilitating the quantitative detection of serum Mb. This method is capable of detecting Mb concentrations ranging from 0.05 to 130 ng/mL, with a minimum detection limit of 0.045 ng/mL. This "Apt-target molecule-Apt" sandwich liquid crystal biosensing method offers several advantages, including label-free detection, operational simplicity, and high specificity. It demonstrates significant potential for the rapid detection of serum biomarkers.

Label-Free Liquid Crystal Aptamer Sensors Based on Single-Stranded Nucleic Acid π-Structures for Detecting cTnI

Cardiac troponin I (cTnI) is a highly sensitive and important serological marker for clinical diagnosis of myocardial injury. Its rapid detection is crucial for the early diagnosis of cardiovascular diseases such as acute myocardial infarction. In this study, based on nucleic acid molecular hybridization and aptamer-specific binding to target molecules, a label-free liquid crystal aptamer sensor based on single-stranded nucleic acid π-structures was developed and applied for the quantitative detection of cTnI. The CP1 and CP2 oligonucleotide chains, complementary to the bases at both ends of the aptamer, are covalently bonded to the sensor substrate via APTES and GA-mediated molecules. The aptamer forms a π-structure with CP1 and CP2 through nucleic acid hybridization, serving as a target molecule capture probe. When cTnI is present in the system, cTnI and the complementary oligonucleotide chains competitively bind with the aptamer, causing the breakdown of the π-structure within the sensor. This reinstates the long-range ordered alignment of the 5CB liquid crystal molecules within the sensor, enabling quantitative measurement of cTnI through variations in optical images. Experimental results show that within the range of 0.01 to 25 ng/mL for cTnI concentration, there is a linear correlation between the brightness area coverage (Br) in the polarized light microscopy images of the sensor and the logarithm of the cTnI concentration, with a correlation coefficient (r). The detection limit is 5.16 pg/mL. This method is label-free, simple to operate, and low-cost, with good specificity and a low detection limit, achieving cTnI detection in serum samples.

Magnetic poly(phages) encoded probes-based dual-mode assay for rapid determination of live Escherichia coli and Hafnia paralvei based on microfluidic chip and ATP bioluminescence meter

A dual-mode assay was developed for screening and detecting live Escherichia coli (E. coli) and Hafnia paralvei (H. paralvei) (as two typical pathogens in aquatic environments) based on magnetic poly(phages) encoded probes (MPEP). The probes were prepared by grafting a large number of phages targeting different target bacteria on a long-chain DNA structure, respectively. They could specifically capture and enrich E. coli and H. paralvei by magnetic separation. Then, different DNA signal tags with different lengths conjugate with the corresponding MPEP-bacteria complex and form two kinds of sandwich structures, respectively. After that, the captured E. coli and H. paralvei were lysed to release both adenosine triphosphate (ATP) and DNA signal tags. The measurement includes two steps. Firstly, a portable ATP bioluminescence meter was employed to rapidly screen the positive samples that contain either of the two target bacteria. Secondly, only positive samples were injected into the microfluidic chip which could detect various DNA signal tags for accurate quantification of the target bacteria. The assay demonstrated high sensitivity (3 CFU/mL for E. coli and 5 CFU/mL for H. paralvei), high specificity (strain identification), signal amplification (20-fold), and short time (≤ 35 min). It can be applied to detect other pathogens solely by changing the relative phage in MPEP. Furthermore, the proposed dual-mode assay provides a wide prospect for rapid screening and accurate determination of live foodborne pathogens. Clinical Trial Number: nbdxms-20240322.

Developing portable and controllable fluorescence capillary imprinted sensor for visual detection Crohn's disease biomarkers

Simultaneous detection of multiple biomarker levels is essential to improve the accuracy of early diagnosis. Introducing capillary will simplify procedure, less time, and reduce reagent consumption for point-of-care testing of biomarkers. Here, we developed a portable and controllable smartphone-integrated fluorescence capillary imprinted sensing platform for the accuracy visual detection of Crohn's disease biomarkers (lysozyme, Fe3+) using single-excitation/double-signal detection. A novel controllable capillary coating strategy was developed by static gas-driven coating method for synthesis uniform fluorescence capillary imprinted sensor (Si-CD/g-CdTe@MIP capillary sensor). When Fe3+ and lysozyme were added, the fluorescence intensity of Si-CD/g-CdTe@MIP capillary sensor was quenched at 426 nm and enhanced at 546 nm, respectively. This Si-CD/g-CdTe@MIP capillary sensor has high sensitivity and selectivity for quantification lysozyme and Fe3+ simultaneously with the detection limit of 0.098 nM and 0.20 nM, respectively. In addition, the smartphone-integrated Si-CD/g-CdTe@MIP capillary sensor was applied for the intelligent detection of lysozyme and Fe3+, in which the detection limit was calculated as 0.32 nM and 0.65 nM. The smartphone-integrated visual Si-CD/g-CdTe@MIP capillary sensor realized ultrasensitive microanalysis (18 μL/time) of biomarkers in health man and Crohn 's patients, providing a novel strategy for early diagnosis of Crohn 's disease.

A novel integrated lateral flow immunoassay platform for the detection of cardiac troponin I using hierarchical dendritic copper-nickel nanostructures

Cardiac troponin I (cTnI) is a critical biomarker for the diagnosis of acute myocardial infarction (AMI). Herein, we report a novel integrated lateral flow immunoassay (LFIA) platform for highly sensitive point-of-care testing (POCT) of cTnI using hierarchical dendritic copper-nickel (HD-nanoCu-Ni) nanostructures. The electrodeposited HD-nanoCu-Ni film (∼22 μm thick) on an ITO-coated glass substrate exhibits superior capillary action and structural integrity. These properties enable efficient sample transport and antibody immobilization, making it a compelling alternative to conventional multi-component paper-based LFIA test strips, which are often plagued by structural fragility and susceptibility to moisture damage. The biofunctionalized HD-nanoCu-Ni substrates were laser-etched with lateral flow channels, including a sample loading/conjugate release zone, a test zone, and a control zone. Numerical simulations were used to further optimize the design of these channels to achieve optimal fluid flow and target capture. The HD-nanoCu-Ni LFIA device utilizes a fluorescence quenching based sandwich immunoassay format using antibody-labeled gold nanoparticles (AuNPs) as quenchers. Two different fluorescent materials, fluorescein isothiocyanate (FITC) and CdSe@ZnS quantum dots (QDs), were used as background fluorophores in the device. Upon the formation of a sandwich immunocomplex with cTnI on the HD-nanoCu-Ni device, introduced AuNPs led to the fluorescence quenching of the background fluorophores. The total assay time was approximately 15 min, demonstrating the rapid and efficient nature of the HD-nanoCu-Ni LFIA platform. For FITC, both inner filter effect (IFE) and fluorescence resonance energy transfer (FRET) contributed to the AuNP-mediated quenching. In the case of CdSe@ZnS QDs, IFE dominated the AuNP-induced quenching. Calibration curves were established based on the relationship between the fluorescence quenching intensity and cTnI concentration in human serum samples, ranging from 0.5 to 128 ng/mL. The limits of detection (LODs) were determined to be 0.27 ng/mL and 0.40 ng/mL for FITC and CdSe@ZnS QDs, respectively. A method comparison study using Passing-Bablok regression analysis on varying cTnI concentrations in human serum samples confirmed the equivalence of the HD-nanoCu-Ni LFIA platform to a commercial fluorescence cTnI LFIA assay kit, with no significant systematic or proportional bias observed.

Quantitative measurement of acute myocardial infarction cardiac biomarkers by "All-in-One" immune microfluidic chip for early diagnosis of myocardial infarction

Acute myocardial infarction (AMI) is a life-threatening condition with a narrow treatment window, necessitating rapid and accurate diagnostic methods. We present an "all-in-one" convenient and rapid immunoassay system that combines microfluidic technology with a colloidal gold immunoassay. A degassing-driven chip replaces a bulky external pump, resulting in a user-friendly and easy-to-operate immunoassay system. The chip comprises four units: an inlet reservoir, an immunoreaction channel, a waste pool, and an immunocomplex collection chamber, allowing single-channel flow for rapid and accurate AMI biomarker detection. In this study, we focused on cardiac troponin I (cTnI). With a minimal sample of just 4 μL and a total detection time of under 3 min, the chip enabled a quantitative visual analysis of cTnI concentration within a range of 0.5 ∼ 60.0 ng mL-1. This all-in-one integrated microfluidic chip with colloidal gold immunoassay offers a promising solution for rapid AMI diagnosis. The system's portability, small sample requirement, and quantitative visual detection capabilities make it a valuable tool for AMI diagnostics.

Microfluidic-based cardiovascular systems for advanced study of atherosclerosis

Atherosclerosis (AS) is a significant global health concern due to its high morbidity and mortality rates. Extensive efforts have been made to replicate the cardiovascular system and explore the pathogenesis, diagnosis, and treatment of AS. Microfluidics has emerged as a valuable technology for modeling the cardiovascular system and studying AS. Here a brief review of the advances of microfluidic-based cardiovascular systems for AS research is presented. The critical pathogenetic mechanisms of AS investigated by microfluidic-based cardiovascular systems are categorized and reviewed, with a detailed summary of accurate diagnostic methods for detecting biomarkers using microfluidics represented. Furthermore, the review covers the evaluation and screening of AS drugs assisted by microfluidic systems, along with the fabrication of novel drug delivery carriers. Finally, the challenges and future prospects for advancing microfluidic-based cardiovascular systems in AS research are discussed and proposed, particularly regarding new opportunities in multi-disciplinary fundamental research and therapeutic applications for a broader range of disease treatments.

Rapid diagnosis of acute myocardial infarction through integrated microfluidic chips for detection of characteristic targets

Myoglobin (Myo), creatine kinase-MB (CKMB), and cardiac troponin I (cTnI) are crucial biomarkers for diagnosing acute myocardial infarction (AMI) The accurate and rapid detection of these three targets can greatly improve the prognosis of AMI patients. Herein, this study developed a microfluidic immunofluorescence method that can detect all three targets in 10-15 min. Ultrasonic atomization and spray technology are used to modify the surface of the injection-molded microfluidic chip (MFC), which effectively solves the problem of biological cross-linking and antibody immobilization on the MFC surface. In addition, it improves the hydrophilicity of the chip surface, thus enhancing fluid self-driving effect. The linear response towards Myo, CKMB and cTnI range from 5 ng/mL to 500 ng/mL, 1 ng/mL to 70 ng/mL, and 0.05 ng/mL to 30 ng/mL, respectively. The intra-batch precision is ≤ 10%, and the inter-batch precision is ≤ 15%. Furthermore, this method shows good consistency compared with the BECKMAN ACCESS2 chemiluminescent immunoanalyzer. The present work provides an AMI diagnostic method with high sensitivity, good repeatability, high accuracy and simple operation, which can satisfy the needs of clinical diagnosis, and shows promising application prospects.

Innovative, Flexible, and Miniaturized Microfluidic Paper-Based Plasmonic Chip for Efficient Near-Infrared Metal Enhanced Fluorescence Biosensing and Imaging

The implementation of metal enhanced fluorescence (MEF) as an efficient detection tool, especially in the near-infrared region of the electromagnetic spectrum, is a rather new direction for diagnostic analytical technologies. In this context, we propose a novel microfluidic plasmonic design based on paper for efficient MEF detection of the "proof-of-concept" biotin-streptavidin recognition interaction. Our design made use of the benefits of gold nanobipyramids (AuBPs), considering the strong enhanced electromagnetic field present at their sharp tips, and filter paper to operate as a natural microfluidic channel due to excellent wicking abilities. The calligraphed plasmonic paper, obtained using a commercial pen filled with AuBPs, was integrated in a robust sandwich optically transparent polydimethylsiloxane chip, exhibiting portability and flexibility while preserving the chip's properties. To place the Alexa 680 fluorophore at an optimal distance from the nanobipyramid substrate, the human IgG-anti-IgG-conjugated biotin sandwich reaction was employed. Thus, upon the capture of Alexa 680-conjugated streptavidin by the biotinylated system, a 1.3-fold average enhancement of the fluorophore's emission was determined by bulk fluorescence measurements. However, the local enhancement factor was considerably higher with values spanning from 5 to 6.3, as proven by mapping the fluorescence emission under both re-scan microscopy and fluorescence lifetime imaging, endorsing the proposed chip's feasibility for bulk MEF biosensing as well as high-resolution MEF bioimaging. Finally, the versatility of our chip was demonstrated by adapting the biosensing protocol for cardiac troponin I biomarker detection, validated using 10 plasma samples collected from pediatric patients and corroborated with a conventional ELISA assay.