Field Of Biosensors Research Articles

A Polarity-Sensitive Far-Red Fluorescent Probe for Glucose Sensing through Skin.

The field of glucose biosensors for diabetes management has been of great interest over the past 60 years. Continuous glucose monitoring (CGM) is important to continuously track the glucose level to provide better management of the disease. Concanavalin A (ConA) can reversibly bind to glucose and mannose molecules and form a glucose biosensor via competitive binding. Here, we developed a glucose biosensor using ConA and a fluorescent probe, which generated a fluorescent intensity change based on solvatochromism, the reversible change in the emission spectrum dependent on the polarity of the solvent. The direction in which the wavelength shifts as the solvent polarity increases can be defined as positive (red-shift), negative (blue-shift), or a combination of the two, referred to as reverse. To translate this biosensor to a subcutaneously implanted format, Cyanine 5.5 (Cy5.5)-labeled small mannose molecules were used, which allows for the far-red excitation wavelength range to increase the skin penetration depth of the light source and returned emission. Three Cy5.5-labeled small mannose molecules were synthesized and compared when used as the competing ligand in the competitive binding biosensor. We explored the polarity-sensitive nature of the competing ligands and examined the biosensor's glucose response. Cy5.5-mannotetraose performed best as a biosensor, allowing for the detection of glucose from 25 to 400 mg/dL. Thus, this assay is responsive to glucose within the physiologic range when its concentration is increased to levels needed for an implantable design. The biosensor response is not statistically different when placed under different skin pigmentations when comparing the percent increase in fluorescence intensity. This shows the ability of the biosensor to produce a repeatable signal across the physiologic range for subcutaneous glucose monitoring under various skin tones.

A critical review of enzymes immobilized on chitosan composites: characterization and applications.

Enzymes with industrial significance are typically used in biological processes. However, instability, high sensitivity, and impractical recovery are the major drawbacks of enzymes in practical applications. In recent years, the immobilization technology has attracted wide attention to overcoming these restrictions and improving the efficiency of enzyme applications. Chitosan (CS) is a unique functional substance with biocompatibility, biodegradability, non-toxicity, and antibacterial properties. Chitosan composites are anticipated to be widely used in the near future for a variety of purposes, including as supports for enzyme immobilization, because of their advantages. Therefor this review explores the effects of the chitosan's structure, molecular weight, degree of deacetylation on the enzyme immobilized, effect of key factors, and the enzymes immobilized on chitosan based composites for numerous applications, including the fields of biosensor, biomedical science, food industry, environmental protection, and industrial production. Moreover, this study carefully investigates the advantages and disadvantages of using these composites as well as their potential in the future.

Regulating the trans-Cleavage Activity of CRISPR/Cas12a by Using an Elongation-Caged Single-Stranded DNA Activator and the Biosensing Applications.

The CRISPR/Cas12a system exhibits extraordinary capability in the field of biosensing and molecular diagnosis due to its trans-cleavage ability. However, it is still desirable for precise control and programmable regulation of Cas12a trans-cleavage activity to promote the in-depth studies and application expansion of Cas12a-based sensing platforms. In this work, we have developed a new and robust CRISPR/Cas12a regulation mechanism by endowing the activator with the function of caging crRNA ingeniously. Specifically, we constructed an integrated elongation-caged activator (EL-activator) by extending the ssDNA activator on the 3'-end. We found that appending only about 8 nt that is complementary to the crRNA repeat region is enough to cage the crRNA spacer/repeat region, thus effectively inhibiting Cas12a trans-cleavage activity. The inner inhibition mechanism was further uncovered after a thorough investigation, demonstrating that the EL-activator works by impeding the conformation of crRNA required for Cas12a recognition and destroying its affinity with Cas12a. By further switching on the elongated moiety on the EL-activator using target biomarkers, the blocked trans-cleavage activity of Cas12a can be rapidly recovered. Finally, a versatile sensing platform was established based on the EL-activator regulation mechanism, expanding the conventional Cas12a system that only directly recognizes DNA to the direct detection of enzymes and RNA biomarkers. This work has enriched the CRISPR/Cas12a regulation toolbox and expanded its sensing applications.

Highly Active Single-Atom Nanozymes with High-Loading Iridium for Sensitive Detection of Pesticides.

Single-atom nanozymes (SAzymes) are novel mimic-enzyme materials with atomically doped active sites. They play a pivotal role in the field of nanozymes because of their excellent catalytic activities, high utilization efficiency of the metal atoms, and simple model of active sites. Herein, the peroxidase (POD)-like SAzymes with high-loading iridium (Ir) (5.31%) on graphene oxide (GO) nanosheets [Ir(III)/GO] were prepared through a coordination reaction between the Ir(III) complex and the oxygen-containing groups in GO. The preparation strategy avoids nitrogen doping and pyrolysis procedures which are the usually used strategies to improve the GO-based enzyme mimic activity. Ascribed to the highly active Ir atoms, Ir(III)/GO SAzymes demonstrate outstanding POD-like activity without the oxidase-like activity. In advantage of the excellent POD-like activity, a simple and sensitive colorimetric pesticide detection platform is established. The developed sensing platform offers an excellent "switch-on" pirimicarb (PIB) detection in the linear range of 10-300 nM with a limit of detection (LOD) of 2.81 nM. Moreover, the detection platform was fabricated into a portable test kit, which is composed of a test swab and sample processing tube. In the aid of a color-reading APP, the test kit can detect PIB with the LOD of 3.31 nM. It is astonishing to get this excellent detection sensitivity just using the simple colorimetric strategy. This work not only provides a novel strategy to synthesize Ir-based SAzymes but also exhibits the super capability of Ir(III)/GO in the biosensing field.

Recent Advances in Common Transition Metal‐Based Single‐Atom Nanozymes and Their Applications in Pollutant Detection and Degradation

AbstractNanozymes can be used as favorable substitutes for natural enzymes because of their strong catalytic activity and good stability. At the same time, research on single‐atom catalysts (SACs) with isolated metal atoms as active centers is also in full swing, showing excellent performance in a variety of catalytic reactions. With the in‐depth study of SACs, people have a comprehensive understanding of them and put forward the concept of single‐atom nanozymes (SAzymes) by combining nanozymes with SACs. As a new type of nanomaterial, SAzymes have attracted great interest due to their remarkable catalytic activity and rapid energy conversion. However, most applications of SAzymes are mainly in the fields of biomedicine and biosensing, and less research has been done in the field of the environment. Based on the amazing ability of nanozymes to detect and degrade pollutants, SAzymes are also used in the environmental field, and even they will show better capabilities. This review mainly analyses common transition metal‐based SAzymes and describes their applications in the field of environmental pollutants.

Thermus thermophilus Argonaute-based signal amplifier for highly sensitive and specific microRNA detection.

The prokaryote-derived gene defense system as a new generation of nucleic acid detection tool exhibits impressive performance in the field of molecular diagnosis. Prokaryotic Argonaute (Ago) is a CRISPR-associated protein that is guided by a short DNA (gDNA) and then efficiently cleaves gDNA-complementary nucleic acids and presents unique characteristics that are different from the CRISPR/Cas system. However, the application of Ago in biosensing is still relatively scarce, and many properties of Ago need to be further clarified. In this study, we aim to systematically explore the properties of Thermus thermophilus Argonaute (TtAgo), including the dependence of TtAgo activity on guide DNA (gDNA) length, substrates' length, and the position of gDNA complementary region on the substrate. Based on these properties, we constructed an exonuclease III-assisted target-recycled amplification system (exoAgo) for sensitive miRNA detection. The result showed that exoAgo can be used for miRNA profiling with a detection limit of 12.2pM and single-base-resolution and keep good performance for the detection of complex samples, which indicates that Ago has great application potential in the detection of nucleic acids. In conclusion, this study will provide guidance for further development and utilization of Ago in the field of biosensing.

Framework-Enhanced Electrochemiluminescence in Biosensing

Electrochemiluminescence (ECL) has attracted increasing attention owing to its intrinsic advantages of high sensitivity, good stability, and low background. Considering the fact that framework nanocrystals such as metal–organic frameworks and covalent organic frameworks have accurate molecular structures, a series of framework-based ECL platforms are developed for decoding emission fundamentals. The integration of fluorescent ligands into frameworks significantly improves the ECL properties due to the arrangement of molecules and intramolecular electron transfer. Moreover, the various framework topologies can be easily functionalized with the recognition elements to trace the targets for signal readout. These ECL enhancement strategies lead to a series of sensitive analytical methods for protein biomarkers, DNA, small biomolecules, and cells. In this review, we summarize recent advances in various functions of frameworks during the ECL process, and constructions of framework-based ECL platforms for biosensing. The framework-based ECL nanoemitters and enhancement mechanisms show both theoretical innovation and potential applications in designing ECL biosensing systems. Perspectives are also discussed, which may give a guideline for researchers in the fields of ECL biosensing and reticular materials.

Advancements in SARS-CoV-2 Testing: Enhancing Accessibility through Machine Learning-Enhanced Biosensors.

The COVID-19 pandemic highlighted the importance of widespread testing for SARS-CoV-2, leading to the development of various new testing methods. However, traditional invasive sampling methods can be uncomfortable and even painful, creating barriers to testing accessibility. In this article, we explore how machine learning-enhanced biosensors can enable non-invasive sampling for SARS-CoV-2 testing, revolutionizing the way we detect and monitor the virus. By detecting and measuring specific biomarkers in body fluids or other samples, these biosensors can provide accurate and accessible testing options that do not require invasive procedures. We provide examples of how these biosensors can be used for non-invasive SARS-CoV-2 testing, such as saliva-based testing. We also discuss the potential impact of non-invasive testing on accessibility and accuracy of testing. Finally, we discuss potential limitations or biases associated with the machine learning algorithms used to improve the biosensors and explore future directions in the field of machine learning-enhanced biosensors for SARS-CoV-2 testing, considering their potential impact on global healthcare and disease control.

Translocation of Proteins through Solid-State Nanopores Using DNA Polyhedral Carriers.

The detection of biomolecules at the single molecule level has important applications in the fields of biosensing and biomedical diagnosis. The solid-state nanopore (SS nanopore) is a sensitive tool for detecting single molecules because of its unique label-free and low sample consumption properties. SS nanopore translocation of small biomolecules is typically driven by an electronic field force and is thus influenced by the charge, shape, and size of the target molecules. Therefore, it remains challenging to control the translocation of biomolecules through SS nanopores, particularly for different proteins with complex conformations and unique charges. Toward this problem, a DNA polyhedral carrier coating strategy to assist protein translocation through SS nanopores is developed, which facilitates target protein detection. The current signal-to-noise ratios are improved significantly using this DNA carrier loading strategy. The proposed method should aid the detection of proteins, which are difficult to translocate through nanopores. This coating-assisted method offers a wide range of applications for SS nanopore detection and promotes the development of single-molecule detection.

Antenna effect of perylene-sensitized up-conversion luminescent material amplifies the signal of electrochemiluminescence biosensor platform for the ultra-sensitive detection of enrofloxacin

Recently, up-conversion luminescent (UCL) materials have caught extensive sight on account of their excellent biocompatibility and weak automatic fluorescence background, but the low optical signal makes researchers shy away. Organic dye-sensitized UCL materials can improve the low optical signal drawback of UCL and rejuvenate it with adjustable optical properties and unique antenna effects. In this work, an efficient, simple and selective electrochemiluminescence (ECL) sensing platform was developed for determination of enrofloxacin (ENR). 3,4,9,10-perylene tetracarboxylic acid (PTCA) was successfully used as an “antenna” to improve the ECL performance of the UCL nanoparticles (PEI-NaYF4: Yb, Er) due to its appropriate excitation spectrum position and superior electron transfer rate. The specific recognition function of the aptamer enabled the sensor to eliminate the interference from conspecific impurity. In the presence of ENR, the specific combination of ENR with aptamer made the aptamer fall from surface of the electrode, thus we could see a considerable enhancement of signal. Under the most favourable conditions, the aptasensor based on antenna effect displayed a wide detection range (1.0 × 10−14∼1.0 × 10−6 M), low limit of detection (LOD = 3.0 × 10−15 M) and receivable recoveries (96.0%–102.4%) during water samples analysis. At this point, antenna effect provides a powerful strategy to expand the application of UCL in the field of ECL biosensing.

Screen-Printed Silver/Silver Chloride Electrodes Inhibit Alcohol Oxidase Activity

Silver/silver chloride (Ag/AgCl) is ubiquitous in the field of electrochemical biosensing due to its suitability as a reference electrode material. However, we recently discovered that screen-printed Ag/AgCl ink has a detrimental effect on Alcohol Oxidase enzyme stability. We performed an optical absorbance assay to isolate the interaction of enzyme and electrode to discover a surprisingly strong inhibition effect. The halftime of enzymatic activity was reduced from nearly 1 week in buffer to 10 h in the presence of the Ag/AgCl electrode. We expect this discovery to have broad implications on enzymatic biosensors that use Ag/AgCl as reference electrode material.

High performance zwitterionic hydrogels for ECG/EMG signals monitoring

Zwitterionic hydrogel is receiving growing interest due to their unique structure and properties. Nevertheless, overcoming the problem of weak mechanical strength and integrating multiple functions into one zwitterionic hydrogel is still a great challenge. Herein, we have designed an ion-conductive (3.0 S/m) zwitterionic hydrogel featured with many desirable properties of high strength (134 kPa), transparency (the average light transmission closes to 90%), flexibility (up to 287%), self-adhesion (187.5 N/m), low contact impedance (79 Ω) and fatigue resistance. The zwitterionic hydrogel exhibits good flexibility and fatigue resistance due to the combination of chemical cross-linking and hydrogen bonding in the structure. Additionally, it can adhere extensively to various substrate surfaces through intermolecular forces and detect small physical movements, simultaneously capturing the ECG and EMG signals of the body with precision and stability. It also demonstrates higher sensitivity (0.46) and lower RMS noise (6.83 μV) in static measurements than those of current commercial electrodes. We believe that the designed zwitterionic hydrogel has promising applications in the field of wearable biosensors.

Design of DMAP functionalized MoS2-GO hybrid for targeted visual detection of dopamine: a step towards chromogenic substrate free point of care testing

Abnormal release of DA, a crucial neurotransmitter, can cause serious neurological disorders such as Parkinson's and Alzheimer's disease. Thus, sensitive DA detection becomes critical for the investigation of physiological functions and disease diagnosis. Specific DA quantification in real samples is a tedious task due to the presence of analogous neurotransmitters. Therefore, aiming at on-site selective monitoring of DA, a high-performance colorimetric probe has been designed using a DMAP-modified MoS2-GO hybrid for highly selective visual detection of DA, especially for POC testing. The efficient DA recognition can be attributed to the large surface area with potentially active sites for greater electron transport and oxidation ability owing to the synergistic effect of MoS2 and GO. The hybrid has been modified with DMAP, which allows extremely selective and specific DA recognition against potential interferents, especially other neurotransmitters. The proposed mechanism relies on the attachment of DA to the hybrid surface, facilitating the oxidation and complexation processes that induce aggregation causing instant color change. The designed colorimetric method can recognize DA in neutral medium at room temperature without any reagents or supplementary operations. A good linear relationship was observed between the absorbance of the hybrid and DA concentrations in the range 1–100 μM, with a low detection limit of 0.17 μM. Furthermore, the applicability of the present approach was also verified by the analysis of DA in human serum samples and proved to be promising for sequential DA detection in biological samples with good precision and accuracy. From a POC perspective, easy-to-use paper-based test strips were prepared for visual recognition of DA in just 3 min. Results indicate that the designed DA assay provides a powerful, low-cost, convenient, and reagentless colorimetric platform for instant and highly selective DA detection in aqueous solution, strips, and human serum that is predicted to find extended applications in the fields of biosensing, clinical diagnosis, and in-vitro disease monitoring.

Non-Invasive Wearable Sweat and Tear-Based Biosensors for Continuous Health Monitoring

Over the years, the continuous advancements within the wearable biosensor field have raised public awareness in exploring new strategies for people's personalized point-of-care testing. Biosensors are multifunctional devices that allow people to quantify a range of biological signals through highly sensitive and small-scale sensing platforms, thus providing users convenience when limiting the need for clinical check-ups and laboratory diagnosis. Via dynamic, non-invasive evaluation of biomarkers in bodily fluids, biosensors are able to provide users with a nearly instant numerical result of the targeted biomarker's level (e.g., glucose, chloride) within their body. Here, this paper mainly focuses on exploring the wide range of sweat and tear-based biosensors' applications and methods to some extent. New generations of sweat-based wearable biosensors have been developed to better monitor one's health status by introducing techniques such as microfluidic sweat collection and Iontophoresis sweat induction methods. Additionally, much investment and effort have been put into developing tear-based wearable biosensors. For example, contact lens-based sensors are the most commonly adopted method for tear analysis, providing a minimally invasive detection of biomarkers.

Electronic Tongue for Direct Assessment of SARS-CoV-2-Free and Infected Human Saliva-A Feasibility Study.

An electronic tongue is a powerful analytical instrument based on an array of non-selective chemical sensors with a partial specificity for data gathering and advanced pattern recognition methods for data analysis. Connecting electronic tongues with electrochemical techniques for data collection has led to various applications, mostly within sensing for food quality and environmental monitoring, but also in biomedical research for the analyses of different bioanalytes in human physiological fluids. In this paper, an electronic tongue consisting of six electrodes (viz., gold, platinum, palladium, titanium, iridium, and glassy carbon) was designed and tested in authentic (undiluted, unpretreated) human saliva samples from eight volunteers, collected before and during the COVID-19 pandemic. Investigations of 11 samples using differential pulse voltammetry and a principal component analysis allowed us to distinguish between SARS-CoV-2-free and infected authentic human saliva. This work, as a proof-of-principle demonstration, provides a new perspective for the use of electronic tongues in the field of enzyme-free electrochemical biosensing, highlighting their potential for future applications in non-invasive biomedical analyses.

Preparation of Fe3O4/SiO2@CDS@Pt Micromotors for Dual‐Mode Detection of Blood Lead

AbstractIt is necessary to accurately detect the content of lead in blood. Here, we investigate the preparation of magnetic mesoporous silica tubular (MMST) micromotors and their application in blood lead detection. Specifically, a magnetic MMST/Carbon dots (CDs)/Pt tubular micromotor with fluorescence property and autonomous motion ability was prepared. Results show that the micromotor has a dual response of fluorescence and speed to trace lead ions in blood. In the blood lead concentration range (0.001 ng/mL–31.62 ng/mL), the fluorescence intensity and movement speed of the micromotor have a linear relationship with the blood lead concentration, respectively. This dual‐detection platform provides a new idea for the detection of blood lead. It is the first time to combine the quantum dots and the motion rate of motor to detect lead ions in blood. It may have some potential value in the field of biosensors in the future.

Research progress of DNA aptamer-based silver ions detection

Silver ions are regarded as one of the most hazardous metal contaminants, endangering both the ecological environment and human health. Traditional silver ions detection technologies are hampered by their high cost, time-consuming nature, and labor-intensive operation. DNA aptamers play an essential part in the field of biosensors due to their ease of synthesis, ease of modification, and low cost. This paper focuses on reviewing the research progress of DNA aptamer-based biosensors in silver ions detection. According to the types of signal transduction, they are classified into four forms of signal transduction: fluorescent biosensors, colorimetric biosensors, electrochemical biosensors, and surface-enhanced Raman spectroscopy biosensors. In addition, this paper gives a perspective on the application prospects outlook and development directions of DNA aptamer-based biosensors, in order to provide theoretical ideas for the future development of more sensitive DNA aptamer biosensors for rapid detection of silver ions.

Advances in Stabilization and Enrichment of Shallow Nitrogen-Vacancy Centers in Diamond for Biosensing and Spin-Polarization Transfer.

Negatively charged nitrogen-vacancy (NV-) centers in diamond have unique magneto-optical properties, such as high fluorescence, single-photon generation, millisecond-long coherence times, and the ability to initialize and read the spin state using purely optical means. This makes NV- centers a powerful sensing tool for a range of applications, including magnetometry, electrometry, and thermometry. Biocompatible NV-rich nanodiamonds find application in cellular microscopy, nanoscopy, and in vivo imaging. NV- centers can also detect electron spins, paramagnetic agents, and nuclear spins. Techniques have been developed to hyperpolarize 14N, 15N, and 13C nuclear spins, which could open up new perspectives in NMR and MRI. However, defects on the diamond surface, such as hydrogen, vacancies, and trapping states, can reduce the stability of NV- in favor of the neutral form (NV0), which lacks the same properties. Laser irradiation can also lead to charge-state switching and a reduction in the number of NV- centers. Efforts have been made to improve stability through diamond substrate doping, proper annealing and surface termination, laser irradiation, and electric or electrochemical tuning of the surface potential. This article discusses advances in the stabilization and enrichment of shallow NV- ensembles, describing strategies for improving the quality of diamond devices for sensing and spin-polarization transfer applications. Selected applications in the field of biosensing are discussed in more depth.

Emerging Biosensing Methods to Monitor Lung Cancer Biomarkers in Biological Samples: A Comprehensive Review

Lung cancer is the most commonly diagnosed of all cancers and one of the leading causes of cancer deaths among men and women worldwide, causing 1.5 million deaths every year. Despite developments in cancer treatment technologies and new pharmaceutical products, high mortality and morbidity remain major challenges for researchers. More than 75% of lung cancer patients are diagnosed in advanced stages, leading to poor prognosis. Lung cancer is a multistep process associated with genetic and epigenetic abnormalities. Rapid, accurate, precise, and reliable detection of lung cancer biomarkers in biological fluids is essential for risk assessment for a given individual and mortality reduction. Traditional diagnostic tools are not sensitive enough to detect and diagnose lung cancer in the early stages. Therefore, the development of novel bioanalytical methods for early-stage screening and diagnosis is extremely important. Recently, biosensors have gained tremendous attention as an alternative to conventional methods because of their robustness, high sensitivity, inexpensiveness, and easy handling and deployment in point-of-care testing. This review provides an overview of the conventional methods currently used for lung cancer screening, classification, diagnosis, and prognosis, providing updates on research and developments in biosensor technology for the detection of lung cancer biomarkers in biological samples. Finally, it comments on recent advances and potential future challenges in the field of biosensors in the context of lung cancer diagnosis and point-of-care applications.

Fiber Laser-Based Lasso-Shaped Biosensor for High Precision Detection of Cancer Biomarker-CEACAM5 in Serum.

Detection of trace tumor markers in blood/serum is essential for the early screening and prognosis of cancer diseases, which requires high sensitivity and specificity of the assays and biosensors. A variety of label-free optical fiber-based biosensors has been developed and yielded great opportunities for Point-of-Care Testing (POCT) of cancer biomarkers. The fiber biosensor, however, suffers from a compromise between the responsivity and stability of the sensing signal, which would deteriorate the sensing performance. In addition, the sophistication of sensor preparation hinders the reproduction and scale-up fabrication. To address these issues, in this study, a straightforward lasso-shaped fiber laser biosensor was proposed for the specific determination of carcinoembryonic antigen (CEA)-related cell adhesion molecules 5 (CEACAM5) protein in serum. Due to the ultra-narrow linewidth of the laser, a very small variation of lasing signal caused by biomolecular bonding can be clearly distinguished via high-resolution spectral analysis. The limit of detection (LOD) of the proposed biosensor could reach 9.6 ng/mL according to the buffer test. The sensing capability was further validated by a human serum-based cancer diagnosis trial, enabling great potential for clinical use. The high reproduction of fabrication allowed the mass production of the sensor and extended its utility to a broader biosensing field.