Nanoplasmonic amplification in microfluidics enables accelerated colorimetric quantification of nucleic acid biomarkers from pathogens

Fully integrated and automated centrifugal microfluidic chip for point-of-care multiplexed molecular diagnostics

Public health events caused by pathogens have imposed significant economic and societal burdens. However, conventional methods still face challenges including complex operations, the need for trained operators, and sophisticated instruments. Here, we proposed a fully integrated and automated centrifugal microfluidic chip, also termed IACMC, for point-of-care multiplexed molecular diagnostics by harnessing the advantages of active and passive valves. The IACMC incorporates multiple essential components including a pneumatic balance module for sequential release of multiple reagents, a pneumatic centrifugation-assisted module for on-demand solution release, an on-chip silicon membrane module for nucleic acid extraction, a Coriolis force-mediated fluid switching module, and an amplification module. Numerical simulation and visual validation were employed to iterate and optimize the chip's structure. Upon sample loading, the chip automatically executes the entire process of bacterial sample lysis, nucleic acid capture, elution quantification, and isothermal LAMP amplification. By optimizing crucial parameters including centrifugation speed, direction of rotation, and silicone membrane thickness, the chip achieves exceptional sensitivity (twenty-five Salmonella or forty Escherichia coli) and specificity in detecting Escherichia coli and Salmonella within 40 min. The development of IACMC will drive advancements in centrifugal microfluidics for point-of-care testing and holds potential for broader applications in precision medicine including high-throughput biochemical analysis immune diagnostics, and drug susceptibility testing.

Dual toeholds regulated CRISPR-Cas12a sensing platform for ApoE single nucleotide polymorphisms genotyping

Single nucleotide polymorphisms (SNPs) are closely associated with many biological processes, including genetic disease, tumorigenesis, and drug metabolism. Accurate and efficient SNP determination has been proved pivotal in pharmacogenomics and diagnostics. Herein, a universal and high-fidelity genotyping platform is established based on the dual toeholds regulated Cas12a sensing methodology. Different from the conventional single stranded or double stranded activation mode, the dual toeholds regulated mode overcomes protospacer adjacent motif (PAM) limitation via cascade toehold mediated strand displacement reaction, which is highly universal and ultra-specific. To enhance the sensitivity for biological samples analysis, a modified isothermal recombinant polymerase amplification (RPA) strategy is developed via utilizing deoxythymidine substituted primer and uracil-DNA glycosylase (UDG) treatment, designated as RPA-UDG. The dsDNA products containing single stranded toehold domain generated in the RPA-UDG allow further incorporation with dual toeholds regulated Cas12a platform for high-fidelity human sample genotyping. We discriminate all the single-nucleotide polymorphisms of ApoE gene at rs429358 and rs7412 loci with human buccal swab samples with 100% accuracy. Furthermore, we engineer visual readout of genotyping results by exploiting commercial lateral flow strips, which opens new possibilities for field deployable implementation.

Engineered two-dimensional nanomaterials based diagnostics integrated with internet of medical things (IoMT) for COVID-19

More than four years have passed since an inimitable coronavirus disease (COVID-19) pandemic hit the globe in 2019 after an uncontrolled transmission of the severe acute respiratory syndrome (SARS-CoV-2) infection. The occurrence of this highly contagious respiratory infectious disease led to chaos and mortality all over the world. The peak paradigm shift of the researchers was inclined towards the accurate and rapid detection of diseases. Since 2019, there has been a boost in the diagnostics of COVID-19 via numerous conventional diagnostic tools like RT-PCR, ELISA, etc., and advanced biosensing kits like LFIA, etc. For the same reason, the use of nanotechnology and two-dimensional nanomaterials (2DNMs) has aided in the fabrication of efficient diagnostic tools to combat COVID-19. This article discusses the engineering techniques utilized for fabricating chemically active E2DNMs that are exceptionally thin and irregular. The techniques encompass the introduction of heteroatoms, intercalation of ions, and the design of strain and defects. E2DNMs possess unique characteristics, including a substantial surface area and controllable electrical, optical, and bioactive properties. These characteristics enable the development of sophisticated diagnostic platforms for real-time biosensors with exceptional sensitivity in detecting SARS-CoV-2. Integrating the Internet of Medical Things (IoMT) with these E2DNMs-based advanced diagnostics has led to the development of portable, real-time, scalable, more accurate, and cost-effective SARS-CoV-2 diagnostic platforms. These diagnostic platforms have the potential to revolutionize SARS-CoV-2 diagnosis by making it faster, easier, and more accessible to people worldwide, thus making them ideal for resource-limited settings. These advanced IoMT diagnostic platforms may help with combating SARS-CoV-2 as well as tracking and predicting the spread of future pandemics, ultimately saving lives and mitigating their impact on global health systems.

Electro-Optical Multiclassification Platform for Minimizing Occasional Inaccuracy in Point-of-Care Biomarker Detection

On-site diagnostic tests that accurately identify disease biomarkers lay the foundation for self-healthcare applications. However, these tests routinely rely on single-mode signals and suffer from insufficient accuracy, especially for multiplexed point-of-care tests (POCTs) within a few minutes. Here, this work develops a dual-mode multiclassification diagnostic platform that integrates an electrochemiluminescence sensor and a field-effect transistor sensor in a microfluidic chip. The microfluidic channel guides the testing samples to flow across electro-optical sensor units, which produce dual-mode readouts by detecting infectious biomarkers of tuberculosis (TB), human rhinovirus (HRV), and group B streptococcus (GBS). Then, machine-learning classifiers generate three-dimensional (3D) hyperplanes to diagnose different diseases. Dual-mode readouts derived from distinct mechanisms enhance the anti-interference ability physically, and machine-learning-aided diagnosis in high-dimensional space reduces the occasional inaccuracy mathematically. Clinical validation studies with 501 unprocessed samples indicate that the platform has an accuracy approaching 99%, higher than the 77%-93% accuracy of rapid point-of-care testing technologies at 100% statistical power (>150 clinical tests). Moreover, the diagnosis time is 5 min without a trade-off of accuracy. This work solves the occasional inaccuracy issue of rapid on-site diagnosis, endowing POCT systems with the same accuracy as laboratory tests and holding unique prospects for complicated scenes of personalized healthcare.

On-chip droplet analysis and cell spheroid screening by capillary wrapping enabled shape-adaptive ferrofluid transporters

Non-invasive droplet manipulation with no physical damage to the sample is important for the practical value of manipulation tools in multidisciplinary applications from biochemical analysis and diagnostics to cell engineering. It is a challenge to achieve this for most existing photothermal, electric stimuli, and magnetic field-based technologies. Herein, we present a droplet handling toolbox, the ferrofluid transporter, for non-invasive droplet manipulation in an oil environment. It involves the transport of droplets with high robustness and efficiency owing to low interfacial friction. This capability caters to various scenarios including droplets with varying components and solid cargo. Moreover, we fabricated a droplet array by transporter positioning and achieved droplet gating and sorting for complex manipulation in the droplet array. Benefiting from the ease of scale-up and high biocompatibility, the transporter-based droplet array can serve as a digital microfluidic platform for on-chip droplet-based bioanalysis, cell spheroid culture, and downstream drug screening tests.

An Ion Concentration Polarization Microplatform for Efficient Enrichment and Analysis of ctDNA

Strategies for rapid, effective nucleic acid processing hold tremendous significance to the clinical analysis of circulating tumor DNA (ctDNA), a family of important markers indicating tumorigenesis and metastasis. However, traditional techniques remain challenging to achieve efficient DNA enrichment, further bringing about complicated operation and limited detection sensitivity. Here, we developed an ion concentration polarization microplatform that enabled highly rapid, efficient enrichment and purification of ctDNA from a variety of clinical samples, including serum, urine, and feces. The platform demonstrated efficiently separating and enriching ctDNA within 30 s, with a 100-fold improvement over traditional methods. Integrating an on-chip isothermal amplification module, the platform further achieved 100-fold enhanced sensitivity in ctDNA detection, which significantly eliminated false-negative results in the serum or urine samples due to the low abundance of ctDNA. Such a simple-designed platform offers a user-friendly yet powerful diagnosis technique with a wide applicability, ranging from early tumor diagnosis to infection screening.

Massively Scalable Self-Assembly of Nano and Microparticle Monolayers via Aerosol Assisted Deposition

An extremely rapid process for self-assembling well-ordered, nano, and microparticle monolayers via a novel aerosolized method is presented. The novel technique can reach monolayer self-assembly rates as high as 268 cm2 min-1 from a single aerosolizing source and methods to reach faster monolayer self-assembly rates are outlined. A new physical mechanism describing the self-assembly process is presented and new insights enabling high-efficiency nanoparticle monolayer self-assembly are developed. In addition, well-ordered monolayer arrays from particles of various sizes, surface functionality, and materials are fabricated. This new technique enables a 93× increase in monolayer self-assembly rates compared to the current state of the art and has the potential to provide an extremely low-cost option for submicron nanomanufacturing.

Digital microfluidics with distance-based detection - a new approach for nucleic acid diagnostics

There is great enthusiasm for using loop-mediated isothermal amplification (LAMP) in point-of-care nucleic acid amplification tests (POC NAATs), as an alternative to PCR. While isothermal amplification techniques like LAMP eliminate the need for rapid temperature cycling in a portable format, these systems are still plagued by requirements for dedicated optical detection apparatus for analysis and manual off-chip sample processing. Here, we developed a new microfluidic system for LAMP-based POC NAATs to address these limitations. The new system combines digital microfluidics (DMF) with distance-based detection (DBD) for direct signal readout. This is the first report of the use of (i) LAMP or (ii) DMF with DBD - thus, we describe a number of characterization steps taken to determine optimal combinations of reagents, materials, and processes for reliable operation. For example, DBD was found to be quite sensitive to background signals from low molecular weight LAMP products; thus, a Capto™ adhere bead-based clean-up procedure was developed to isolate the desirable high-molecular-weight products for analysis. The new method was validated by application to detection of SARS-CoV-2 in saliva. The method was able to distinguish between saliva containing no virus, saliva containing a low viral load (104 genome copies per mL), and saliva containing a high viral load (108 copies per mL), all in an automated system that does not require detection apparatus for analysis. We propose that the combination of DMF with distance-based detection may be a powerful one for implementing a variety of POC NAATs or for other applications in the future.

Recent advances in point-of-care testing of COVID-19

Advances in microfluidic device miniaturization and system integration contribute to the development of portable, handheld, and smartphone-compatible devices. These advancements in diagnostics have the potential to revolutionize the approach to detect and respond to future pandemics. Accordingly, herein, recent advances in point-of-care testing (POCT) of coronavirus disease 2019 (COVID-19) using various microdevices, including lateral flow assay strips, vertical flow assay strips, microfluidic channels, and paper-based microfluidic devices, are reviewed. However, visual determination of the diagnostic results using only microdevices leads to many false-negative results due to the limited detection sensitivities of these devices. Several POCT systems comprising microdevices integrated with portable optical readers have been developed to address this issue. Since the outbreak of COVID-19, effective POCT strategies for COVID-19 based on optical detection methods have been established. They can be categorized into fluorescence, surface-enhanced Raman scattering, surface plasmon resonance spectroscopy, and wearable sensing. We introduced next-generation pandemic sensing methods incorporating artificial intelligence that can be used to meet global health needs in the future. Additionally, we have discussed appropriate responses of various testing devices to emerging infectious diseases and prospective preventive measures for the post-pandemic era. We believe that this review will be helpful for preparing for future infectious disease outbreaks.

Additively manufactured multiplexed electrochemical device (AMMED) for portable sample-to-answer detection

Portable sample-to-answer devices with applications in point-of-care settings have emerged to obviate the necessity of centralized laboratories for biomarker analysis. In this work, a smartphone-operated and additively manufactured multiplexed electrochemical device (AMMED) is presented for the portable detection of biomarkers in blood and saliva. AMMED is comprised of a customized portable potentiostat with a multiplexing feature, a 3D-printed sample collection cartridge to handle three samples of saliva and blood at the same time, a smartphone application to remotely control the potentiostat, and a 3D-printed-based multiplexed microfluidic electrochemical biosensor (test chip). Here, by employing additive manufacturing techniques, a simple, cleanroom-free, and scalable approach was proposed for the fabrication of the test chip. Moreover, these techniques can bring about easy integration of AMMED components. Additionally, the test chip can be compatible with different affinity-based bioassays which can be implemented in a multiplexed manner for detection. The AMMED components were successfully characterized in terms of electrochemical and fluidic performance. Particularly, to demonstrate the biosensing capabilities of the device, the spike protein of the SARS-CoV-2 omicron variant and a well-established aptameric assay were selected as the representative biomarker and the bioassay, respectively. The proposed device accurately and selectively detected the target of interest in a rapid (5 min) and multiplex manner with a dynamic detection range of 1-10 000 pg ml-1 in different media, and the clinical feasibility was assessed by several saliva patient samples. AMMED offers a versatile sample-to-answer platform that can be used for the detection of various biomarkers present in biofluids.

Saliva Analysis Based on Microfluidics: Focusing the Wide Spectrum of Target Analyte

Saliva is one of the most critical human body fluids that can reflect the state of the human body. The detection of saliva is of great significance for disease diagnosis and health monitoring. Microfluidics, characterized by microscale size and high integration, is an ideal platform for the development of rapid and low-cost disease diagnostic techniques and devices. Microfluidic-based saliva testing methods have aroused considerable interest due to the increasing need for noninvasive testing and frequent or long-term testing. This review briefly described the significance of saliva analysis and generally classified the targets in saliva detection into pathogenic microorganisms, inorganic substances, and organic substances. By using this classification as a benchmark, the state-of-the-art research results on microfluidic detection of various substances in saliva were summarized. This work also put forward the challenges and future development directions of microfluidic detection methods for saliva.

Hot-Electron Dynamics Mediated Medical Diagnosis and Therapy

Surface plasmon resonance excitation significantly enhances the absorption of light and increases the generation of "hot" electrons, i.e., conducting electrons that are raised from their steady states to excited states. These excited electrons rapidly decay and equilibrate via radiative and nonradiative damping over several hundred femtoseconds. During the hot-electron dynamics, from their generation to the ultimate nonradiative decay, the electromagnetic field enhancement, hot electron density increase, and local heating effect are sequentially induced. Over the past decade, these physical phenomena have attracted considerable attention in the biomedical field, e.g., the rapid and accurate identification of biomolecules, precise synthesis and release of drugs, and elimination of tumors. This review highlights the recent developments in the application of hot-electron dynamics in medical diagnosis and therapy, particularly fully integrated device techniques with good application prospects. In addition, we discuss the latest experimental and theoretical studies of underlying mechanisms. From a practical standpoint, the pioneering modeling analyses and quantitative measurements in the extreme near field are summarized to illustrate the quantification of hot-electron dynamics. Finally, the prospects and remaining challenges associated with biomedical engineering based on hot-electron dynamics are presented.

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.