Rapid simultaneous SERS detection of dual myocardial biomarkers on single-track finger-pump microfluidic chip

An AI-assisted microfluidic paper-based multiplexed surface-enhanced raman scattering (SERS) biosensor with electrophoretic removal and electrical modulation for accurate acute myocardial infarction (AMI) diagnosis and prognosis

SERS detects single molecules with exceptional sensitivity. To counter the issue of selectivity faced by point-of-care, herein, an externally applied electric field that allows electrical modulation and electromigrates unbound SERS tags without multiple washing steps is successfully developed and demonstrated to improve the biosensor's selectivity and sensitivity in multiplexed detection of cTnI, HDL, and LDL in human serum at a low LoD. Ultra-sensitive detectors can detect signals from non-specifically absorbed species, and these species can cover up overlapping analyte peaks, amplifying the effect of non-specific binding. Even though antifouling molecules can prevent non-specific adsorption at the sensor interface, this approach does not completely eliminate it. Our significant findings show that an electrically regulated device can electromigrate non-specifically bound species without cross-reacting with endogenous albumin proteins. Stability, repeatability, and reproducibility were good, with an RSD of 10%. Artificial intelligence was employed to interpret and analyze high-dimensional fingerprint SERS spectra using feature selection and dimensionality reduction for accurate acute myocardial infarction diagnosis and prognosis. These machine learning methods allow quantification of cTnI, HDL, and LDL biomarkers with low RMSE. Machine learning classifiers showed strong AUROC values of 0.950 ± 0.111 and 0.884 ± 0.139 for early and recurrent AMI detection, respectively. A high negative predictive value (NPV) of ≥99% indicates an effective early AMI rule-out. In short, this work demonstrated that a simple, low-cost, electrophoretic modulated biosensor with machine learning can diagnose, rule out, and predict recurring AMI.

Multiplexed SERS Detection of Serum Cardiac Markers Using Plasmonic Metasurfaces

Surface-enhanced Raman spectroscopy (SERS) possesses exquisite molecular-specific properties with single-molecule sensitivity. Yet, translation of SERS into a quantitative analysis technique remains elusive owing to considerable fluctuation of the SERS intensity, which can be ascribed to the SERS uncertainty principle, a tradeoff between "reproducibility" and "enhancement". To provide a potential solution, herein, an integrated multiplexed SERS biosensing strategy is proposed, which features two distinct advantages. First, a subwavelength-structured plasmonic metasurface consisting of alternately stacked metal-dielectric pyramidal meta-atoms is fabricated and could provide simultaneously enhanced electric and magnetic fields to enable spatially extended and weakly wavelength-dependent SERS. Second, nanomechanical perturbations are harnessed to transduce signals in the form of SERS frequency shifts, which are not directly affected by the SERS uncertainty principle. By also employing 3D printing methods, a proof-of-concept study of multiplexed detection of a panel of serum cardiac biomarkers for acute myocardial infarction is provided. Success in the development of both the electric and magnetic fields-active plasmonic metasurfaces could transform future designs of SERS substrates with newly endowed functionalities, and frequency shift-based SERS multiplexing could open new opportunities to develop innovative quantitative optical techniques for applications in chemistry, biology, and medicine.

SERS-based pump-free microfluidic chip sensor for highly sensitive competitive immunoassay of cortisol in human sweat

Cortisol, known as the "stress hormone", is secreted by the adrenal cortex. Measuring cortisol levels in body fluids is essential for evaluating stress levels, adrenal function, hormone imbalance, and psychological well-being. Early diagnosis and management of related conditions depend on this measurement. A rapid detection method that combines immunoassay and surface-enhanced Raman scattering (SERS) technology has become widely used in bioanalysis, offering benefits such as fast detection, high throughput, integrated microsystems, and high specificity. This study introduces a pump-free microfluidic chip integrating a solid-state SERS substrate to detect trace amounts of cortisol in bodily fluids through immunoassay. The method relies on a competitive reaction between cortisol and SERS tags with cortisol antigens immobilized on gold nanostructured substrates in a microfluidic environment. Two detection channels are used to provide controls and enhance measurement efficiency and accuracy. Solid-state gold nanostructured substrates offer a larger surface area for antibody capture and act as SERS-active substrates, which significantly enhance the Raman signal and improve the microsystem's sensitivity and applicability. Driven by a capillary pump, the sample can be loaded within 60 seconds, with the entire detection process taking less than 10 min, significantly reducing the detection time. Results indicate that the detection limit for cortisol is 10 pg mL-1, meeting clinical biomarker thresholds. The integrated SERS microfluidic chip shows great promise as an analytical tool for the rapid and sensitive diagnosis of cortisol in bodily fluids.

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.

SERS-based microdevices for use as in vitro diagnostic biosensors

Advances in surface-enhanced Raman scattering (SERS) detection have helped to overcome the limitations of traditional in vitro diagnostic methods, such as fluorescence and chemiluminescence, owing to its high sensitivity and multiplex detection capability. However, for the implementation of SERS detection technology in disease diagnosis, a SERS-based assay platform capable of analyzing clinical samples is essential. Moreover, infectious diseases like COVID-19 require the development of point-of-care (POC) diagnostic technologies that can rapidly and accurately determine infection status. As an effective assay platform, SERS-based bioassays utilize SERS nanotags labeled with protein or DNA receptors on Au or Ag nanoparticles, serving as highly sensitive optical probes. Additionally, a microdevice is necessary as an interface between the target biomolecules and SERS nanotags. This review aims to introduce various microdevices developed for SERS detection, available for POC diagnostics, including LFA strips, microfluidic chips, and microarray chips. Furthermore, the article presents research findings reported in the last 20 years for the SERS-based bioassay of various diseases, such as cancer, cardiovascular diseases, and infectious diseases. Finally, the prospects of SERS bioassays are discussed concerning the integration of SERS-based microdevices and portable Raman readers into POC systems, along with the utilization of artificial intelligence technology.

Multiplex nanozymatic biosensing of Salmonella on a finger-actuated microfluidic chip

A colorimetric biosensor was elaboratively designed for fast, sensitive and multiplex bacterial detection on a single microfluidic chip using immune magnetic nanobeads for specific bacterial separation, immune gold@platinum palladium nanoparticles for specific bacterial labeling, a finger-actuated mixer for efficient immunoreaction and two coaxial rotatable magnetic fields for magnetic nanobead capture (outer one) and magnet-actuated valve control (inner one). First, preloaded bacteria, nanobeads and nanozymes were mixed through a finger actuator to form nanobead-bacteria-nanozyme conjugates, which were captured by the outer magnetic field. After the inner magnetic field was rotated to successively wash the conjugates and push the H2O2-TMB substrate for resuspending these conjugates, colorless TMB was catalyzed into blue TMBox products, followed by color analysis using ImageJ software for bacterial determination. This simple biosensor enabled multiplex Salmonella detection as low as 9 CFU per sample in 45 min.

A review of SERS coupled microfluidic platforms: From configurations to applications

Microfluidic systems have attracted considerable attention due to their low reagent consumption, short analysis time, and ease of integration in comparison to conventional methods, but still suffer from shortcomings in sensitivity and selectivity. Surface enhanced Raman scattering (SERS) offers several advantages in the detection of compounds, including label-free detection at the single-molecule level, and the narrow Raman peak width for multiplexing. Combining microfluidics with SERS is a viable way to improve their detection sensitivity. Researchers have recently developed several SERS coupled microfluidic platforms with substantial potential for biomolecular detection, cellular and bacterial analysis, and hazardous substance detection. We review the current development of SERS coupled microfluidic platforms, illustrate their detection principles and construction, and summarize the latest applications in biology, environmental protection and food safety. In addition, we innovatively summarize the current status of SERS coupled multi-mode microfluidic platforms with other detection technologies. Finally, we discuss the challenges and countermeasures during the development of SERS coupled microfluidic platforms, as well as predict the future development trend of SERS coupled microfluidic platforms.

One-Stop Plasmonic Nanocube-Excited SERS Immunoassay Platform of Multiple Cardiac Biomarkers for Rapid Screening and Progressive Tracing of Acute Myocardial Infarction

Rapid and precise acute myocardial infarction (AMI) diagnosis is essential for preventing patient death. In addition, the complementary roles of creatine kinase muscle brain (CK-MB) and cardiac troponin I (cTnI) cardiac biomarkers in the early and late stages of AMI demand their simultaneous detection, which is difficult to implement using conventional fluorescence and electrochemical technologies. Here, a nanotechnology-based one-stop immuno-surface-enhanced Raman scattering (SERS) detection platform is reported for multiple cardiac indicators for the rapid screening and progressive tracing of AMI events. Optimal SERS is achieved using optical property-based, excitation wavelength-optimized, and high-yield anisotropic plasmonic gold nanocubes. Optimal immunoassay reaction efficiencies are achieved by increasing immobilized antibodies. Multiple simultaneous detection strategies are implemented by incorporating two different Raman reports with narrow wavenumbers corresponding to two indicators and by establishing a computational SERS mapping process to accurately detect their concentrations, irrespective of multiple enzymes in the human serum. The SERS platform precisely estimated AMI onset and progressive timing in human serum and made rapid AMI identification feasible using a portable Raman spectrometer. This integrated platform is hypothesized to significantly contribute to emergency medicine and forensic science by providing timely treatment and observation.

Portable microfluidic plasmonic chip for fast real-time cardiac troponin I biomarker thermoplasmonic detection

Acute myocardial infarction is one of the most serious cardiovascular pathologies, impacting patients' long-term outcomes and health systems worldwide. Significant effort is directed toward the development of biosensing technologies, which are able to efficiently and accurately detect an early rise of cardiac troponin levels, the gold standard in detecting myocardial injury. In this context, this work aims to develop a microfluidic plasmonic chip for the fast and accurate real-time detection of the cardiac troponin I biomarker (cTnI) via three complementary detection techniques using portable equipment. Furthermore, the study focuses on providing a better understanding of the thermoplasmonic biosensing mechanism taking advantage of the intrinsic photothermal properties of gold nanoparticles. Specifically, a plasmonic nanoplatform based on immobilized gold nanobipyramids was fabricated, exhibiting optical and thermoplasmonic properties that promote, based on a sandwich-like immunoassay, the "proof-of-concept" multimodal detection of cTnI via localized surface plasmon resonance, surface enhanced Raman spectroscopy and thermoplasmonic effects under simulated conditions. Furthermore, after the integration of the plasmonic nanoplatform in a microfluidic channel, the determination of cTnI in 16 real plasma samples was successfully realized via thermoplasmonic detection. The results are compared with a conventional high-sensitivity enzyme-linked immunosorbent clinical assay (ELISA), showing high sensitivity (75%) and specificity (100%) as well as fast response features (5 minutes). Thus, the proposed portable and miniaturized microfluidic plasmonic chip is successfully validated for clinical applications and transferred to clinical settings for the early diagnosis of cardiac diseases, leading towards the progress of personalized medicine.

Advancements in the research of finger-actuated POCT chips

Microfluidic point-of-care testing (POCT) chips are used to enable the mixing and reaction of small sample volumes, facilitating target molecule detection. Traditional methods for actuating POCT chips rely on external pumps or power supplies, which are complex and non-portable. The development of finger-actuated chips has reduced operational difficulty and improved portability, promoting the development of POCT chips. This paper reviews the significance, developments, and potential applications of finger-actuated POCT chips. Three methods for controlling the flow accuracy of finger-actuated chips are summarized: direct push, indirect control, and sample injection control method, along with their respective advantages and disadvantages. Meanwhile, a comprehensive analysis of multi-fluid driving modes is provided, categorizing them into single-push multi-driving and multi-push multi-driving modes. Furthermore, recent research breakthroughs in finger-actuated chips are thoroughly summarized, and their structures, driving, and detection methods are discussed. Finally, this paper discusses the driving performance of finger-actuated chips, the suitability of detection scenarios, and the compatibility with existing detection technologies. It also provides prospects for the future development and application of finger-actuated POCT chips.

A micro-nano interface integrated SERS-based microfluidic sensor for miRNA detection using DNAzyme walker amplification

BACKGROUND

Precise and specific miRNA detection plays a vital role in exploring development mechanisms of cancer disease, thereby it can significantly improve relevant prevention and treatment strategies.

RESULTS

In this work, a surface-enhanced Raman spectroscopy (SERS)-based microfluidic chip has been devised with a microcone array SERS substrate (MCASS) for the miR-141 detection. This substrate excels in unique SERS activity and large surface area for DNA oligonucleotide modification. As the presence of miR-141, the DNAzyme walker induced cleavage reaction took place on the finely designed and prepared dual DNA conjugated SERS nanoprobes. The SERS nanoprobes can anchor on MCASS by the DNA hybridization that achieved an impressive detection limit in the femtomolar level.

SIGNIFICANCE

With this integrated SERS-based microfluidic chip, we provided a miRNA detection strategy using DNAzyme walker amplification technology. It is believed that this strategy could be a powerful tool for miRNA detection and related cancer screening test.

Additive manufacturing leveraged microfluidic setup for sample to answer colorimetric detection of pathogens

Colorimetric readout for the detection of infectious diseases is gaining traction at the point of care/need owing to its ease of analysis and interpretation, and integration potential with highly specific loop-mediated amplification (LAMP) assays. However, coupling colorimetric readout with LAMP is rife with challenges including, rapidity, inter-user variability, colorimetric signal quantification, and user involvement in sequential steps of the LAMP assay, hindering its application. To address these challenges, for the first time, we propose a remotely smartphone-operated automated setup consisting of (i) an additively manufactured microfluidic cartridge, (ii) a portable reflected-light imaging setup with controlled epi-illumination (PRICE) module, and (iii) a control and data analysis module. The microfluidic cartridge facilitates sample collection, lysis, mixing of amplification reagents stored on-chip, and subsequent isothermal heating for initiation of amplification in a novel way by employing tunable elastomeric chambers and auxiliary components (heaters and linear actuators). PRICE offers a new imaging setup that captures the colorimetric change of the amplification media over a plasmonic nanostructured substrate in a controlled and noise-free environment for rapid minute-scale nucleic acid detection. The control and data analysis module employs microprocessors to automate cartridge operation in tandem with the imaging module. The different device components were characterized individually and finally, as a proof of concept, SARS-CoV-2 wild-type RNA was detected with a turnaround time of 13 minutes, showing the device's clinical feasibility. The suggested automated device can be adopted in future iterations for other detection and molecular assays that require sequential fluid handling steps.