SERS-based immunoassay using gold-patterned array chips for rapid and sensitive detection of dual cardiac biomarkers

Highly sensitive SERS nanoplatform based on aptamer and vancomycin for detection of S. aureus and its clinical application

Staphylococcus aureus (S. aureus) is the most common pathogen in human purulent infections, which can cause local purulent infections, as well as pneumonia, pseudomembranous enteritis, pericarditis, and even systemic infections. The conventional methods including bacteria colony counting, polymerase chain reaction and enzyme-linked immunosorbent assay can't fully meet the requirement of highly sensitive detection of S. aureus due to their own disadvantages. Therefore, it's an urgent need to develop new platform to detect S. aureus in the early infection stage. In this study, a new surface-enhanced Raman scattering (SERS)-based nanoplatform based on dual-recognition of aptamer (Apt) and vancomycin (Van) was developed for the highly sensitive detection of S. aureus. The SERS nanoplatform consisted of two functional parts: aptamer-conjugated Fe3O4 magnetic nanoparticles (Fe3O4-Apt MNPs) for bacteria enrichment and vancomycin modified-Au nanoparticles (Van-Au NPs) as the SERS probes for S. aureus quantitative detection. Upon the target bacteria enrichment, the SERS signals of the supernatant after magnetic separation could be obtained and analyzed under different concentrations of S. aureus. The limit of detection of the proposed assay was found to be 3.27 CFU/mL. We believe that the proposed SERS-based nanoplatform has great potential as a powerful tool in the early detection of specific bacteria.

SERS in 3D cell models: a powerful tool in cancer research

Unraveling the cellular and molecular mechanisms underlying tumoral processes is fundamental for the diagnosis and treatment of cancer. In this regard, three-dimensional (3D) cancer cell models more realistically mimic tumors compared to conventional 2D cell cultures and are more attractive for performing such studies. Nonetheless, the analysis of such architectures is challenging because most available techniques are destructive, resulting in the loss of biochemical information. On the contrary, surface-enhanced Raman spectroscopy (SERS) is a non-invasive analytical tool that can record the structural fingerprint of molecules present in complex biological environments. The implementation of SERS in 3D cancer models can be leveraged to track therapeutics, the production of cancer-related metabolites, different signaling and communication pathways, and to image the different cellular components and structural features. In this review, we highlight recent progress in the use of SERS for the evaluation of cancer diagnosis and therapy in 3D tumoral models. We outline strategies for the delivery and design of SERS tags and shed light on the possibilities this technique offers for studying different cellular processes, through either biosensing or bioimaging modalities. Finally, we address current challenges and future directions, such as overcoming the limitations of SERS and the need for the development of user-friendly and robust data analysis methods. Continued development of SERS 3D bioimaging and biosensing systems, techniques, and analytical strategies, can provide significant contributions for early disease detection, novel cancer therapies, and the realization of patient-tailored medicine.

Multimetal-Based Metal-Organic Framework System for the Sensitive Detection of Heart-Type Fatty Acid Binding Protein in Electrochemiluminescence Immunoassay

In this work, an electrochemiluminescence (ECL) quenching system using multimetal-organic frameworks (MMOFs) was proposed for the sensitive and specific detection of heart-type fatty acid-binding protein (H-FABP), a marker of acute myocardial infarction (AMI). Bimetallic MOFs containing Ru and Mn as metal centers were synthesized via a one-step hydrothermal method, yielding RuMn MOFs as the ECL emitter. The RuMn MOFs not only possessed the strong ECL performance of Ru(bpy)32+ but also maintained high porosity and original metal active sites characteristic of MOFs. Moreover, under the synergistic effect of MOFs and Ru(bpy)32+, RuMn MOFs have more efficient and stable ECL emission. The trimetal-based MOF (FePtRh MOF) was used as the ECL quencher because of the electron transfer between FePtRh MOFs and RuMn MOFs. In addition, active intramolecular electron transfer from Pt to Fe or Rh atoms also occurred in FePtRh MOFs, which could promote intermolecular electron transfer and improve electron transfer efficiency to enhance the quenching efficiency. The proposed ECL immunosensor demonstrated a wide dynamic range and a low detection limit of 0.01-100 ng mL-1 and 6.8 pg mL-1, respectively, under optimal conditions. The ECL quenching system also presented good specificity, stability, and reproducibility. Therefore, an alternative method for H-FABP detection in clinical diagnosis was provided by this study, highlighting the potential of MMOFs in advancing ECL technology.

Cardiac multiscale bioimaging: from nano- through micro- to mesoscales

Cardiac multiscale bioimaging is an emerging field that aims to provide a comprehensive understanding of the heart and its functions at various levels, from the molecular to the entire organ. It combines both physiologically and clinically relevant dimensions: from nano- and micrometer resolution imaging based on vibrational spectroscopy and high-resolution microscopy to assess molecular processes in cardiac cells and myocardial tissue, to mesoscale structural investigations to improve the understanding of cardiac (patho)physiology. Tailored super-resolution deep microscopy with advanced proteomic methods and hands-on experience are thus strategically combined to improve the quality of cardiovascular research and support future medical decision-making by gaining additional biomolecular information for translational and diagnostic applications.

SERS-based immunoassay on a plasmonic syringe filter for improved sampling and labeling efficiency of biomarkers

Rapid, sensitive, and quantitative detection of biomarkers is needed for early diagnosis of disease and surveillance of infectious outbreaks. Here, we exploit a plasmonic syringe filter and surface-enhanced Raman spectroscopy (SERS) in the development of a rapid detection system, using human IgG as a model diagnostic biomarker. The novel assay design facilitates multiple passages of the sample and labeling solution through the detection zone enabling us to investigate and maximize sampling efficiency to the capture substrate. The vertical flow immunoassay process in this study involves the utilization of filter paper embedded with gold nanoparticles (AuNPs) to form a plasmonic substrate. Capture antibody (anti-human IgG) is then immobilized onto the prepared plasmonic paper and inserted into a vertical flow device (syringe filter holder). Sample solution is passed through the filter paper and the target antigen (human IgG) is selectively captured by the immobilized antibody to form an antibody-antigen complex. Next, functionalized AuNPs as extrinsic Raman labels (ERLs) are passed through the filter paper to label the captured biomarker molecules forming a layered structure. This sandwiched geometry enhances plasmonic coupling and SERS signal to provide highly sensitive detection of biomolecules. Systematic studies to investigate the impact of multiple infuse/withdraw cycles of the sample and labeling solutions reveal that antigen and ERL binding are maximized with 10 and 20 cycles, respectively. The optimized assay achieves a detection limit of ∼0.2 ng mL-1 for human IgG with a total assay time of less than 5 minutes, meeting the demands for rapid point of care diagnostics. Additionally, the optimized platform was implemented in the quantitative analysis of the SARS-CoV-2 nucleocapsid protein, the typical target in commercial, FDA-approved rapid antigen tests for COVID-19.

Raman-Based Techniques in Medical Applications for Diagnostic Tasks: A Review

Raman spectroscopy is a widely developing approach for noninvasive analysis that can provide information on chemical composition and molecular structure. High chemical specificity calls for developing different medical diagnostic applications based on Raman spectroscopy. This review focuses on the Raman-based techniques used in medical diagnostics and provides an overview of such techniques, possible areas of their application, and current limitations. We have reviewed recent studies proposing conventional Raman spectroscopy and surface-enhanced Raman spectroscopy for rapid measuring of specific biomarkers of such diseases as cardiovascular disease, cancer, neurogenerative disease, and coronavirus disease (COVID-19). As a result, we have discovered several most promising Raman-based applications to identify affected persons by detecting some significant spectral features. We have analyzed these approaches in terms of their potentially diagnostic power and highlighted the remaining challenges and limitations preventing their translation into clinical settings.

Exploring the Clinical Utility of Raman Spectroscopy for Point-of-Care Cardiovascular Disease Biomarker Detection

A variety of innovative point-of-care (POC) solutions using Raman systems have been explored. However, the vast effort is in assay development, while studies of the characteristics required for Raman spectrometers to function in POC applications are lacking. In this study, we tested and compared the performance of eight commercial Raman spectrometers ranging in size from benchtop Raman microscopes to portable and handheld Raman spectrometers using paper fluidic cartridges, including their ability to detect cardiac troponin I and heart fatty acid binding protein, both of which are well-established biomarkers for evaluating cardiovascular health. Each spectrometer was evaluated in terms of excitation wavelength, laser characteristics, and ease of use to investigate POC utility. We found that the Raman spectrometers equipped with 780 and 785 nm laser sources exhibited a reduced background signal and provided higher sensitivity compared to those with 633 and 638 nm laser sources. Furthermore, the spectrometer equipped with the single acquisition line readout functionality showed improved performance when compared to the point scan spectrometers and allowed measurements to be made faster and easier. The portable and handheld spectrometers also showed similar detection sensitivity to the gold standard instrument. Lastly, we reduced the laser power for the spectrometer with single acquisition line readout capability to explore the system performance at a laser power that change the classification from a Class 3B laser device to a Class 3R device and found that it showed comparable performance. Overall, these findings show that portable Raman spectrometers have the potential to be used in POC settings with accuracy comparable to laboratory-grade instruments, are relatively low-cost, provide fast signal readout, are easy to use, and can facilitate access for underserved communities.

The Emerging Role of Raman Spectroscopy as an Omics Approach for Metabolic Profiling and Biomarker Detection toward Precision Medicine

Omics technologies have rapidly evolved with the unprecedented potential to shape precision medicine. Novel omics approaches are imperative toallow rapid and accurate data collection and integration with clinical information and enable a new era of healthcare. In this comprehensive review, we highlight the utility of Raman spectroscopy (RS) as an emerging omics technology for clinically relevant applications using clinically significant samples and models. We discuss the use of RS both as a label-free approach for probing the intrinsic metabolites of biological materials, and as a labeled approach where signal from Raman reporters conjugated to nanoparticles (NPs) serve as an indirect measure for tracking protein biomarkers in vivo and for high throughout proteomics. We summarize the use of machine learning algorithms for processing RS data to allow accurate detection and evaluation of treatment response specifically focusing on cancer, cardiac, gastrointestinal, and neurodegenerative diseases. We also highlight the integration of RS with established omics approaches for holistic diagnostic information. Further, we elaborate on metal-free NPs that leverage the biological Raman-silent region overcoming the challenges of traditional metal NPs. We conclude the review with an outlook on future directions that will ultimately allow the adaptation of RS as a clinical approach and revolutionize precision medicine.

Progress in the Optical Sensing of Cardiac Biomarkers

Biomarkers play key roles in the diagnosis, risk assessment, treatment and supervision of cardiovascular diseases (CVD). Optical biosensors and assays are valuable analytical tools answering the need for fast and reliable measurements of biomarker levels. This review presents a survey of recent literature with a focus on the past 5 years. The data indicate continuing trends towards multiplexed, simpler, cheaper, faster and innovative sensing while newer tendencies concern minimizing the sample volume or using alternative sampling matrices such as saliva for less invasive assays. Utilizing the enzyme-mimicking activity of nanomaterials gained ground in comparison to their more traditional roles as signaling probes, immobilization supports for biomolecules and for signal amplification. The growing use of aptamers as replacements for antibodies prompted emerging applications of DNA amplification and editing techniques. Optical biosensors and assays were tested with larger sets of clinical samples and compared with the current standard methods. The ambitious goals on the horizon for CVD testing include the discovery and determination of relevant biomarkers with the help of artificial intelligence, more stable specific recognition elements for biomarkers and fast, cheap readers and disposable tests to facilitate rapid testing at home. As the field is progressing at an impressive pace, the opportunities for biosensors in the optical sensing of CVD biomarkers remain significant.

Chemiluminescence Biosensor for the Determination of Cardiac Troponin I (cTnI)

Cardiac vascular diseases, especially acute myocardial infarction (AMI), are one of the leading causes of death worldwide. Therefore cardio-specific biomarkers such as cardiac troponin I (cTnI) play an essential role in the field of diagnostics. In order to enable rapid and accurate measurement of cTnI with the potential of online measurements, a chemiluminescence-based immunosensor is presented as a proof of concept. A flow cell was designed and combined with a sensitive CMOS camera allowing sensitive optical readout. In addition, a microfluidic setup was established, which achieved selective and quasi-online cTnI determination within ten minutes. The sensor was tested with recombinant cTnI in phosphate buffer and demonstrated cTnI measurements in the concentration range of 2-25 µg/L. With the optimized system, a limit of detection (LoD) of 0.6 µg/L (23 pmol/L) was achieved. Furthermore, the selectivity of the immunosensor was investigated with other recombinant proteins, such as cTnT, and cTnC, at a level of 16 µg/L. No cross-reactivity could be observed. Measurements with diluted blood plasma and serum resulted in an LoD of 60 µg/L (2.4 nmol/L) and 70 µg/L (2.9 nmol/L), respectively.

Black Phosphorous Aptamer-based Platform for Biomarker Detection

Black phosphorus nanostructures (nano-BPs) mainly include BP nanosheets (BP NSs), BP quantum dots (BPQDs), and other nano-BPs-based particles at nanoscale. Firstly discovered in 2014, nano-BPs are one of the most popular nanomaterials. Different synthesis methods are discussed in short to understand the basic concepts and developments in synthesis. Exfoliated nano-BPs, i.e. nano-BPs possess high surface area, high photothermal conversion efficacy, excellent biocompatibility, high charge carrier mobility (~1000 cm^-2V^-1s^-1), thermal conductivity of 86 Wm^-1K^-1; and these properties make it a highly potential candidate for fabrication of biosensing platform. These properties enable nano-BPs to be promising photothermal/drug delivery agents as well as in electrochemical data storage devices and sensing devices; and in super capacitors, photodetectors, photovoltaics and solar cells, LEDs, super-conductors, etc. Early diagnosis is very critical in the health sector scenarios. This review attempts to highlight the attempts made towards attaining stable BP, BP-aptamer conjugates for successful biosensing applications. BP-aptamer- based platforms are reviewed to highlight the significance of BP in detecting biological and physiological markers of cardiovascular diseases and cancer; to be useful in disease diagnosis and management.

SERS-Based Immunoassay of Myocardial Infarction Biomarkers on a Microfluidic Chip with Plasmonic Nanostripe Microcones

We developed a new plasmonic nanostripe microcone array (PNMA) substrate-integrated microfluidic chip for the simultaneous surface-enhanced Raman scattering (SERS)-based immunoassay of the creatine kinase MB isoenzyme (CK-MB) and cardiac troponin (cTnI) cardiac markers. The conventional immunoassay usually employs a microtiter plate as the solid capture plate to form the immunocomplexes. However, the two-dimensional (2D) surface of the microtiter plate limits the capture efficiency of the target antigens due to the steric hindrance effect. To address this issue, a gold film-coated microcone array with nanostripes was developed that can provide a large surface area for capture antibody conjugation and serve as a SERS-active substrate. This unique nano-microhierarchical structure showed an excellent light trapping effect and induced surface plasmon resonance to further enhance the Raman signals of the SERS nanoprobes. It significantly improved the sensitivity and applicability of SERS-based immunoassay on the microfluidic chip. With this integrated microfluidic chip, we successfully performed the simultaneous detection of CK-MB and cTnI, and the detection limit can reach 0.01 ng mL^-1. It is believed that the PNMA substrate-integrated microfluidic chip would play a critical role in the rapid and sensitive diagnostics of cardiac diseases.

A review of cardiac troponin I detection by surface enhanced Raman spectroscopy: Under the spotlight of point-of-care testing

Cardiac troponin I (cTnI) is a biomarker widely related to acute myocardial infarction (AMI), one of the leading causes of death around the world. Point-of-care testing (POCT) of cTnI not only demands a short turnaround time for its detection but the highest accuracy levels to set expeditious and adequate clinical decisions. The analytical technique Surface-enhanced Raman spectroscopy (SERS) possesses several properties that tailor to the POCT format, such as its flexibility to couple with rapid assay platforms like microfluidics and paper-based immunoassays. Here, we analyze the strategies used for the detection of cTnI by SERS considering POCT requirements. From the detection ranges reported in the reviewed literature, we suggest the diseases other than AMI that could be diagnosed with this technique. For this, a section with information about cardiac and non-cardiac diseases with cTnI release, including their release kinetics or cut-off values are presented. Likewise, POCT features, the use of SERS as a POCT technique, and the biochemistry of cTnI are discussed. The information provided in this review allowed the identification of strengths and lacks of the available SERS-based point-of-care tests for cTnI and the disclosing of requirements for future assays design.

N, Adigal S, Lukose J, Kartha VB, Chidangil S. Cardiovascular biomarkers in body fluids: progress and prospects in optical sensors

Cardiovascular diseases (CVD) are the major causative factors for high mortality and morbidity in developing and developed nations. The biomarker detection plays a crucial role in the early diagnosis of several non-infectious and life-threatening diseases like CVD and many cancers, which in turn will help in more successful therapy, reducing the mortality rate. Biomarkers have diagnostic, prognostic and therapeutic significances. The search for novel biomarkers using proteomics, bio-sensing, micro-fluidics, and spectroscopic techniques with good sensitivity and specificity for CVD is progressing rapidly at present, in addition to the use of gold standard biomarkers like troponin. This review is dealing with the current progress and prospects in biomarker research for the diagnosis of cardiovascular diseases. Expert opinion. Fast diagnosis of cardiovascular diseases (CVDs) can help to provide rapid medical intervention, which can affect the patient's short and long-term health. Identification and detection of proper biomarkers for early diagnosis are crucial for successful therapy and prognosis of CVDs. The present review discusses the analysis of clinical samples such as whole blood, blood serum, and other body fluids using techniques like high-performance liquid chromatography-LASER/LED-induced fluorescence, Raman spectroscopy, mainly, optical methods, combined with nanotechnology and micro-fluidic technologies, to probe patterns of multiple markers (marker signatures) as compared to conventional techniques.

Cardiac Troponin Biosensor Designs: Current Developments and Remaining Challenges

Acute myocardial infarction (AMI) is considered as one of the main causes of death, threating human lives for decades. Currently, its diagnosis relies on electrocardiography (ECG), which has been proven to be insufficient. In this context, the efficient detection of cardiac biomarkers was proposed to overcome the limitations of ECG. In particular, the measurement of troponins, specifically cardiac troponin I (cTnI) and cardiac troponin T (cTnT), has proven to be superior in terms of sensitivity and specificity in the diagnosis of myocardial damage. As one of the most life-threatening conditions, specific and sensitive investigation methods that are fast, universally available, and cost-efficient to allow for early initiation of evidence-based, living-saving treatment are desired. In this review, we aim to present and discuss the major breakthroughs made in the development of cTnI and cTnT specific biosensor designs and analytical tools, highlighting the achieved progress as well as the remaining challenges to reach the technological goal of simple, specific, cheap, and portable testing chips for the rapid and efficient on-site detection of cardiac cTnI/cTnT biomarkers in order to diagnose and treat cardiovascular diseases at an incipient stage.

SERS based Y-shaped aptasensor for early diagnosis of acute kidney injury

Considering the pivotal role of biomarkers in plasma, the development of biomarker specific sensing platforms is of great significance to achieve accurate diagnosis and monitor the occurrence and progress in acute kidney injury (AKI). In this paper, we develop a promising surface-enhanced Raman scattering-based aptasensor for duplex detection of two protein biomarkers in AKI. Exploiting the base-pairing specificity of nucleic acids to form a Y-shaped self-assembled aptasensor, the MGITC labelled gold nanoparticles will be attached to the surface of magnetic beads. In the presence of specific AKI-related biomarkers, the gold nanoparticles will detach from magnetic beads into the supernatant, thus leading to a SERS signal increase, which can be used for the highly sensitive analysis of target biomarkers. In addition, the limit of detection calculated for each biomarker indicates that the SERS-based aptasensor can well meet the detection requirements in clinical applications. Finally, the generality of this sensor in the early diagnosis of AKI is confirmed by using a rat model and spiked plasma samples. This sensing platform provides a facile and general route for sensitive SERS detection of AKI-related biomarkers, which offers great promising utility for in vitro and accurate practical bioassay in AKI early diagnosis.

Wash-free operation of smartphone-integrated optical immunosensor using retroreflective microparticles

Herein, we introduce a smartphone-integrated immunosensor based on non-spectroscopic optical detection. Sedimentation of the retroreflector and gentle inversion of the microfluidic chip was chosen as biosensing principles to ensure minimal human involvement. To realize this, wash-free immunosensing was implemented on a polymeric microfluidic chip device fabricated for light signal penetration in retroreflection signal acquisition. Applying a transparent chip and passive modulation of retroreflectors enabled the minimization of human error during sensing. In addition, a retroreflection-detectable optical gadget was constructed for integration with the commercial smartphone. The gadget had an optical chamber that induced retroreflection by integration with a smartphone. When the micro-sized reflector, named the retroreflective Janus microparticle, reacted on the sensing surface, the incident light was retroreflected towards the image sensor and quantified by a smartphone-installed Android application package. The developed application package features include time-lapse image capture performed by manipulating LED flash and camera modules, and quantification of retroreflected signal counts by image processing of time-lapse images. With this platform, the user could independently commence optical signal processing without a complicated optical setup and running software on a PC, and sensitive and reproducible immunosensing results could be obtained. The applicability test for creatine kinase-myocardial band detection from the buffer to serum was conducted and presented a calibration curve of 0-1000 ng/mL within 1 h. With the developed system, we believe that the applicability of the platform in bioanalytical detection can be expanded.

Dual Sensitization Smartphone Colorimetric Strategy Based on RCA Coils Gathering Au Tetrahedra and Its Application in the Detection of CK-MB

In recent years, the combination of DNA nanotechnology and biosensing has been extensively reported. Herein, we attempted to develop a dual sensitization smartphone colorimetric strategy based on rolling circle amplification (RCA) coils gathering Au tetrahedra and explore its application. The dual sensitization effect of this strategy was achieved by rolling circle amplification (RCA) and Au tetrahedra. Under the initiation of the complementary DNA, a large number of ssDNA were generated, achieving amplification of the reaction signal. At the same time, due to the formation of Au tetrahedra, more gold nanoparticles could be gathered under the same conditions, and the signal would be amplified again. Using software ImageJ, the gray value of the reaction solution can be analyzed, detecting the target timely under the practical conditions of lack of equipment. By selecting aptamers with strong binding affinity, we applied this strategy to detect creatine kinase isoenzymes (CK-MB), showing a limit of detection of 0.8 pM, which performed well in actual detection and can meet the needs for real-time detection of CK-MB. Therefore, a universal detection platform was developed, which has broad application prospects in biosensing, clinical diagnosis, food detection, and other fields.

Biomimetic -mineralized multifunctional nanoflowers for anodic-stripping voltammetric immunoassay of rehabilitation-related proteins

C-reactive proteins (CRPs; an acute-phase protein) in patients with initial acute cerebral infarction neurological rehabilitation prediction have a significant correlation. In this work, a simple and sensitive anodic-stripping voltammetric (ASV) immunosensing system was innovatively designed for the quantitative screening of target CRPs using biomimetic-mineralized bifunctional antibody-Cu₃(PO₄)₂ nanoflowers as molecular tags. In this system, a monoclonal anti-CRP antibody-anchored microtiter plate was utilized to specifically capture target CRPs from the sample. For detection, a sandwiched immunoreaction mode was employed with the antibody-Cu₃(PO₄)₂ nanoflowers in the presence of analytes. Subsequent ASV measurement of copper ions (Cu²⁺) released under acidic conditions from the bifunctional nanoflowers was conducted at an in situ prepared mercury film electrode. The introduction of hybrid nanoflowers greatly increased the loading amount of copper ions on the molecular tag, thereby amplifying the detectable signal of electrochemical immunoassay. Meanwhile, factors influencing the analytical properties of the electrochemical immunoassay were investigated in detail. By combining the high-efficiency nanohybrids with signal amplification, the dynamic concentration range of electrochemical immunoassay spanned from 0.01 ng mL^-1 to 100 ng mL^-1 toward the target CRP. The limit of detection was calculated to be 0.0079 ng mL^-1 at 3S_blank criterion. Intra- and interassay imprecisions (relative standard deviations: RSDs) were less than or equal to 6.72%. Good anti-interference ability, long-term storage stability, and acceptable accuracy for the evaluation of human serum specimens were observed during a series of procedures to determine the target protein. In addition, the bifunctional nanoflower-based immunosensing system offers promise for the simple, cost-effective analysis of disease-related proteins.

Aptamer-modified magnetic SERS substrate for label-based determination of cardiac troponin I

A sensitive label-based SERS strategy composed of magnetic bimetallic nanoparticles Fe₃O₄@Ag@Au, specific aptamer, and Bradford method was developed for the quantitative determination of cardiac troponin I (cTnI) in human serum. The prepared substrate with high magnetic character, signal enhancement, and uniformity exhibited significant Raman response. After the substrate was bound to the aptamer, the target protein cTnI was specifically captured, and it showed the Raman signal when the signal reporter Coomassie Brilliant Blue G-250 (CBBG) was supplied. The Raman signal intensity at 1621 cm^-1 showed a wide linear relationship with the log value of the cTnI concentration in the range 0.01 to 100 ng·mL^-1, and the estimated limit of detection (LOD) was 5.50 pg·mL^-1. The recovery and relative standard deviation (RSD) of the spike experiment in human serum samples were 92-115% and 7.4-12.7%, respectively.

Antibody coated conductive polymer for the electrochemical immunosensing of Human Cardiac Troponin I in blood plasma

Cardiac troponin I (cTnI) is a sensitive biomarker for cardiovascular disease (CVD). Rapid determination of cTnI concentration in blood can greatly reduce the potential of significant heart damage and heart failure. Herein, we demonstrate a new electrochemical immunosensor for selective affinity binding and rapid detection of cTnI in blood plasma by an electrochemical method. A conductive film of "poly 2,5-bis(2-thienyl)3,4-diamine-terthiophene (PDATT)" was deposited onto an Indium Tin Oxide (ITO) electrode using chronoamperometry. Anti-cardiac troponin I antibody was then attached to the two amine (NH₂) groups substituted on the central thiophene of terthiophene repeating unit of the polymer chain via amide bond formation. The gaps on the surface of the antibody coated immunosensor were backfilled with bovine serum albumin (BSA) to prevent nonspecific binding of interfering molecules. Differential pulse voltammetry (DPV) was used to determine cTnI upon the formation of cTnI immunocomplex on the sensing surface, appearing a peak at 0.27 V. The response range was 0.01-100 ng mL^-1 with limit of quantification down to 0.01 ng mL^-1. The developed immunosensor was used to determine cTnI in spiked blood plasma without interference from cardiac troponin T (cTnT). Therefore, this new sensor can be utilised for the detection of cTnI biomarker in pathological laboratories and points of care in less than 15 min.

High-throughput fabrication of high aspect ratio Ag/Al nanopillars for optical detection of biomarkers

Nanomaterial-based optical techniques for biomarker detection have garnered tremendous attention from the nanofabrication community due to their high precision and enhanced limit of detection (LoD) features. These nanomaterials are highly responsive to local refractive index (RI) fluctuations, and their RI unit sensitivity can be tuned by varying the chemical composition, geometry, and dimensions of the utilized nanostructures. To improve the sensitivity and LoD values of these nanomaterials, it is common to increase both dimensions and aspect ratios of the fabricated nanostructures. However, limited by the complexity, prolonged duration, and elevated costs of the available nanofabrication techniques, mass production of these nanostructures remains challenging. To address not only high accuracy, but also speed and production effectiveness in these nanostructures' fabrication, our work reports, for the first time, a fast, high-throughput, and cost-effective nanofabrication protocol for routine manufacturing of polymer-based nanostructures with high sensitivity and calculated LoD in the pM range by utilizing anodized aluminum oxide (AAO) membranes as templates. Specifically, our developed platform consists of arrays of nearly uniform polystyrene nanopillars with an average diameter of ∼185 nm and aspect ratio of ∼11. We demonstrate that these nanostructures can be produced at a high speed and a notably low price, and that they can be efficiently applied for biosensing purposes after being coated with aluminum-doped silver (Ag/Al) thin films. Our platform successfully detected very low concentrations of human C-reactive protein (hCRP) and SARS-CoV-2 spike protein biomarkers in human plasma samples with LoDs of 11 and 5 pM, respectively. These results open new opportunities for day-to-day fabrication of high aspect ratio arrays of nanopillars that can be used as a base for nanoplasmonic sensors with competitive LoD values. This, in turn, contributes to the development of point-of-care devices and further improvement of the existing nanofabrication techniques, thereby enriching the fields of pharmacology, clinical analysis, and diagnostics.

Development of a novel ssDNA aptamer targeting cardiac troponin I and its clinical applications

Cardiac troponin I (cTnI) is a specific biomarker of acute myocardial infarction (AMI). However, cTnI detection kits prepared with antibodies have many defects. Nucleic acid aptamers are sequences of single-strand DNA or RNA that can overcome the deficiency of antibodies. Herein, sandwich ELONA methods were established based on aptamers. Two selected ssDNA aptamers (Apt3 and Apt6) showed high binding affinity and sensibility (Apt3: Kd = 1.01 ± 0.07 nM, Apt6: k = 0.68 ± 0.05) and did not bind to the same domain of cTnI. Therefore, these two aptamers can be applied to the ELONA methods. The detection range of cTnI using the dual-aptamer sandwich ELONA method was 0.05-200 ng/mL, and the bioanalytical method verification results can meet the national standard of Chinese Pharmacopoeia (2020 Edition). There was no difference between results of the dual-aptamer sandwich ELONA method and the diagnostic results of serum obtained from 243 people (P = 0.39, P ˃ 0.05). The sensitivity and specificity of the ELONA with cTnI in serum were 96.46% and 93.85%, respectively. Compared with the FICA kit, which is clinically used, the consequences of ELONA method are closer to the diagnostic results. This study suggests that the aptamers Apt3 and Apt6 have high affinity and strong specificity and that the dual-aptamer sandwich ELONA method has a wide detection range and can be used to determine cTnI in serum, with potential applications in the diagnosis of AMIs.

Molecular Details on Multiple Cofactor Containing Redox Metalloproteins Revealed by Infrared and Resonance Raman Spectroscopies

Vibrational spectroscopy and in particular, resonance Raman (RR) spectroscopy, can provide molecular details on metalloproteins containing multiple cofactors, which are often challenging for other spectroscopies. Due to distinct spectroscopic fingerprints, RR spectroscopy has a unique capacity to monitor simultaneously and independently different metal cofactors that can have particular roles in metalloproteins. These include e.g., (i) different types of hemes, for instance hemes c, a and a3 in caa3-type oxygen reductases, (ii) distinct spin populations, such as electron transfer (ET) low-spin (LS) and catalytic high-spin (HS) hemes in nitrite reductases, (iii) different types of Fe-S clusters, such as 3Fe-4S and 4Fe-4S centers in di-cluster ferredoxins, and (iv) bi-metallic center and ET Fe-S clusters in hydrogenases. IR spectroscopy can provide unmatched molecular details on specific enzymes like hydrogenases that possess catalytic centers coordinated by CO and CN- ligands, which exhibit spectrally well separated IR bands. This article reviews the work on metalloproteins for which vibrational spectroscopy has ensured advances in understanding structural and mechanistic properties, including multiple heme-containing proteins, such as nitrite reductases that house a notable total of 28 hemes in a functional unit, respiratory chain complexes, and hydrogenases that carry out the most fundamental functions in cells.

Long non-coding RNA SENCR alleviates hypoxia/reoxygenation-induced cardiomyocyte apoptosis and inflammatory response by sponging miR-1

Background

Myocardial cell apoptosis is one of the main reasons for the occurrence of acute myocardial infarction (AMI). The role of smooth muscle and endothelial cell enriched migration/differentiation-associated lncRNA (SENCR) in the cardiomyocyte apoptosis induced by hypoxia/reoxygenation (H/R) injury and its potential mechanism were investigated in this study to provide a novel biomarker for the development of AMI.

Methods

The expression levels of SENCR in the serum of AMI patients and non-AMI patients with chest pain (control) were detected by qRT-PCR. The function of SENCR in the cardiomyocyte apoptosis and inflammatory response induced by H/R injury was evaluated by MTT, cell apoptosis, and ELISA assay, respectively. The mechanism underlying the function of SENCR was investigated with the luciferase reporter assay.

Results

SENCR was significantly downregulated in AMI compared with the control volunteers, which showed negative correlations with the cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) level of patients. The H/R injury-induced cell apoptosis and inflammatory response in cardiomyocytes, which were attenuated by the overexpression of SENCR. The expression of miR-1 was suppressed by the overexpression of SENCR, while the overexpression of miR-1 could alleviate the cell apoptosis, enhance cell viability, and attenuate inflammatory response in cardiomyocyte. SENCR reversed H/R-induced myocardial cell injury by regulating the expression of miR-1.

Conclusions

SENCR was correlated with the clinicopathological features of patients and was revealed to alleviate the cardiomyocyte apoptosis and inflammatory response induced by H/R injury via sponging miR-1.

Microfluidics-Based Sensing of Biospecies

Over the past decades, microfluidic devices based on many advanced techniques have aroused widespread attention in the fields of chemical, biological, and analytical applications. Integration of microdevices with a variety of chip designs will facilitate promising functionality. Notably, the combination of microfluidics with functional nanomaterials may provide creative ideas to achieve rapid and sensitive detection of various biospecies. In this review, focused on the microfluids and microdevices in terms of their fabrication, integration, and functions, we summarize the up-to-date developments in microfluidics-based analysis of biospecies, where biomarkers, small molecules, cells, and pathogens as representative biospecies have been explored in-depth. The promising applications of microfluidic biosensors including clinical diagnosis, food safety control, and environmental monitoring are also discussed. This review aims to highlight the importance of microfluidics-based biosensors in achieving high throughput, highly sensitive, and low-cost analysis and to promote microfluidics toward a wider range of applications.

SERS-based immunoassay using core–shell nanotags and magnetic separation for rapid and sensitive detection of cTnI

Au-4MBA@Ag with a strong Raman signal was successfully synthesized, and combination with magnetic separation technology achieved sensitive detection of cTnI.

SERS-based magnetic immunoassay for simultaneous detection of cTnI and H-FABP using core-shell nanotags

Acute myocardial infarction (AMI) is the single leading cause of worldwide mortality and morbidity. Heart-type fatty acid-binding protein (H-FABP) and cardiac troponin I (cTnI), as biomarkers emerging at different stages of AMI, have complementary advantages in terms of specificity and sensitivity. Therefore, we developed a magnetic immunoassay method based on surface-enhanced Raman scattering (SERS) to detect H-FABP and cTnI simultaneously. Herein, two mutually independent Raman reporter molecules were embedded between a gold core and silver shell and then combined with a tracer antibody to form a SERS immunoprobe. During detection, the SERS immunoprobe, target antigen and capture probe undergo an immune reaction to form a sandwich structure, and then the immune complex was enriched by a specific reaction of streptavidin on the surface of magnetic beads with biotin. Finally, the concentration of biomarkers was quantified by detecting the characteristic Raman peak intensities of the two Raman reporter molecules. Under the optimized conditions, the minimum detection limits of H-FABP and cTnI were 0.6396 and 0.0044 ng mL^-1, respectively. Besides, the target antigen does not cross-react with non-specific proteins, showing good specificity. Therefore, our proposed SERS-based magnetic immunoassay method has the advantages of accuracy, rapidity and good selectivity, and has great potential for early diagnosis of acute myocardial infarction disease.

Applications of surface-enhanced Raman spectroscopy in detection fields

Surface-enhanced Raman spectroscopy (SERS) is a Raman spectroscopy technique that has been widely used in food safety, environmental monitoring, medical diagnosis and treatment and drug monitoring because of its high selectivity, sensitivity, rapidness, simplicity and specificity in identifying molecular structures. This review introduces the detection mechanism of SERS and summarizes the most recent progress concerning the use of SERS for the detection and characterization of molecules, providing references for the later research of SERS in detection fields.

Troponin Aptamer on an Atomically Flat Au Nanoplate Platform for Detection of Cardiac Troponin I

Well-ordered bioreceptors on atomically flat Au surfaces can be a high-performance biosensor. Cardiac troponin I proteins (cTnIs) have been regarded as a specific biomarker for acute myocardial infarction (AMI). Here, we report the accurate detection of cTnIs using an aptamer-immobilized Au nanoplate platform. The single-crystalline and atomically flat Au nanoplate was characterized by atomic force microscopy. For the precise detection of cTnI, we immobilized an aptamer that can strongly bind to cTnI onto an atomically flat Au nanoplate. Using the aptamer-immobilized Au nanoplate, cTnIs were successfully detected at a concentration of 100 aM (2.4 fg/mL) in buffer solution. Furthermore, cTnIs in serum could be identified at a concentration of 100 fM (2.4 pg/mL). The total assay time was ~7 h. Importantly, the aptamer-immobilized Au nanoplate enabled us to diagnose AMI patients accurately, suggesting the potential of the present method in the diagnosis of AMI.

Recent Trends in Electrochemical Sensors for Vital Biomedical Markers Using Hybrid Nanostructured Materials

This work provides a succinct insight into the recent developments in electrochemical quantification of vital biomedical markers using hybrid metallic composite nanostructures. After a brief introduction to the biomarkers, five types of crucial biomarkers, which require timely and periodical monitoring, are shortlisted, namely, cancer, cardiac, inflammatory, diabetic and renal biomarkers. This review emphasizes the usage and advantages of hybrid nanostructured materials as the recognition matrices toward the detection of vital biomarkers. Different transduction methods (fluorescence, electrophoresis, chemiluminescence, electrochemiluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy) reported for the biomarkers are discussed comprehensively to present an overview of the current research works. Recent advancements in the electrochemical (amperometric, voltammetric, and impedimetric) sensor systems constructed with metal nanoparticle-derived hybrid composite nanostructures toward the selective detection of chosen vital biomarkers are specifically analyzed. It describes the challenges involved and the strategies reported for the development of selective, sensitive, and disposable electrochemical biosensors with the details of fabrication, functionalization, and applications of hybrid metallic composite nanostructures.

Rapid and sensitive detection of cardiac troponin I using a force enhanced immunoassay with nanoporous membrane

There is a need for point of care diagnostic technologies that are rapid, sensitive, easy to use, and relatively inexpensive. In this article we describe an assay that uses an antibody functionalized nanoporous membrane and superparamagnetic beads to capture and detect human cardiac troponin I (cTnI), which is an important biomarker for acute myocardial infarction (AMI). The membrane assisted force differentiation assay (mFDA) is capable of detecting cTnI at a sensitivity of 0.1 pg ml^-1 in 15% serum in less than 16 minutes, which is a significant improvement in performance over conventional lateral flow immuosorbant assays. The speed of this assay results from the rapid concentration of cTnI on the surface of the nanoporous membrane and the use of the magnetic beads to react with the analyte, which rapidly react with the immobilized cTnI. The increased sensitivity of assay results from the use of magnetically controlled forces that reduce the nonspecific background and modify both the on-rate and off-rate. We believe that the improved performance and ease of application of the mFDA will make it useful in the early identification of AMI as well as other diseases based on the detection of 1 pg ml^-1 variations in the concentrations cTnI in blood.

Nanoscale Technologies in Highly Sensitive Diagnosis of Cardiovascular Diseases

Cardiovascular diseases (CVD) are the leading cause of death and morbidity in the world and are a major contributor to healthcare costs. Although enormous progress has been made in diagnosing CVD, there is an urgent need for more efficient early detection and the development of novel diagnostic tools. Currently, CVD diagnosis relies primarily on clinical symptoms based on molecular imaging (MOI) or biomarkers associated with CVDs. However, sensitivity, specificity, and accuracy of the assay are still challenging for early-stage CVDs. Nanomaterial platform has been identified as a promising candidate for improving the practical usage of diagnostic tools because of their unique physicochemical properties. In this review article, we introduced cardiac biomarkers and imaging techniques that are currently used for CVD diagnosis. We presented the applications of various nanotechnologies on diagnosis within cardiac immunoassays (CIAs) and molecular imaging. We also summarized and compared different cardiac immunoassays based on their sensitivities and working ranges of biomarkers.