Optical Hydrogel Detector for pH Measurements

Measuring pH has become a major key for determining health conditions, and food safety. The traditional pH assessment approaches are costly and offer low sensitivity. Here, a novel pH sensor based on a pH-responsive hydrogel has been developed. A Fresnel lens pattern was replicated on the surface of the pH-responsive hydrogel using the replica mould method. The pH sensors were tested in a pH range of 4–7. Introducing various pH solutions to the pH sensor led to volumetric shifts as the hydrogel swelled with pH. Consequently, the dimensions of the replicated Fresnel lens changed, modifying the focal length and the focus efficiency of the optical sensor. As a result, the measured optical power at a fixed distance from the sensor changed with pH. The optical sensor showed the best performance in the acidic region when pH changed from 4.5 to 5.5, in which the recorded power increased by 13%. The sensor exhibited high sensitivity to pH changes with a short respond time in a reversible manner. The developed pH optical sensor may have applications in medical point-of-care diagnostics and wearable continuous pH detection devices.

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Microfluidics-Based Plasmonic Biosensing System Based on Patterned Plasmonic Nanostructure Arrays

Micromachines ◽

10.3390/mi12070826 ◽

2021 ◽

Vol 12 (7) ◽

pp. 826

Author(s):

Yanting Liu ◽

Xuming Zhang

Keyword(s):

Plasmon Resonance ◽

Point Of Care ◽

Simultaneous Detection ◽

High Sensitivity ◽

Microfluidic Chips ◽

Label Free ◽

Plasmonic Nanostructure ◽

Point Of Care Diagnostics ◽

Surface Enhanced Raman ◽

Nanostructure Arrays

This review aims to summarize the recent advances and progress of plasmonic biosensors based on patterned plasmonic nanostructure arrays that are integrated with microfluidic chips for various biomedical detection applications. The plasmonic biosensors have made rapid progress in miniaturization sensors with greatly enhanced performance through the continuous advances in plasmon resonance techniques such as surface plasmon resonance (SPR) and localized SPR (LSPR)-based refractive index sensing, SPR imaging (SPRi), and surface-enhanced Raman scattering (SERS). Meanwhile, microfluidic integration promotes multiplexing opportunities for the plasmonic biosensors in the simultaneous detection of multiple analytes. Particularly, different types of microfluidic-integrated plasmonic biosensor systems based on versatile patterned plasmonic nanostructured arrays were reviewed comprehensively, including their methods and relevant typical works. The microfluidics-based plasmonic biosensors provide a high-throughput platform for the biochemical molecular analysis with the advantages such as ultra-high sensitivity, label-free, and real time performance; thus, they continue to benefit the existing and emerging applications of biomedical studies, chemical analyses, and point-of-care diagnostics.

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Comparison of Triangular Silver Nanoprisms with Different Capping Agents and Structural Size for H2O2 Etching-Based Biosensors

NANO ◽

10.1142/s1793292018500224 ◽

2018 ◽

Vol 13 (02) ◽

pp. 1850022 ◽

Cited By ~ 3

Author(s):

Lishi Huang ◽

Caihong Yuan ◽

Wenli Chen ◽

Fanshu Zeng ◽

Hui Xu ◽

...

Keyword(s):

Point Of Care ◽

High Sensitivity ◽

Wavelength Shift ◽

Time Saving ◽

Capping Agents ◽

Silver Nanoprisms ◽

Structural Size ◽

Point Of Care Diagnostics ◽

Citrate Capping ◽

Capping Ligands

This study compared the susceptibility of different triangular silver nanoprisms (TSNPRs) towards the etching of hydrogen peroxide (H2O2), a catalytical product of glucose oxidase (GOx). The influence of capping agents and structural size have been explored towards the oxidation of silver nanoprisms. Results indicated that the etching of the TSNPRs was extremely effected by surface capping agents, in which citrate contributed a highest H2O2-sensitive effect in the absence of secondary capping ligands (e.g., glycerol and ethanol). Meanwhile, compared to bigger TSNPRs, smaller nanoprisms exhibited a different signal output of plasma resonance peak through intensity decrease rather than wavelength shift, making them more H2O2-etching susceptibile. In virtue of GOx etching-based system, TSNPRs with a small size and citrate capping were served as a substitute for big nanoprisms to sense glucose, offering a number of advantages such as high sensitivity, improved calibration, time-saving and extended detection ranges. Moreover, the small sized TSNPRs capping with citrate alone have been expected to be of great interest in the trace of GOx, providing an ultrahigh sensitive GOx etching-based analytical platform for point-of-care diagnostics towards other analytes (e.g., DNA, protein).

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CRISPR-Based COVID-19 Testing: Toward Next-Generation Point-of-Care Diagnostics

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.663949 ◽

2021 ◽

Vol 11 ◽

Author(s):

Uyanga Ganbaatar ◽

Changchun Liu

Keyword(s):

Nucleic Acid ◽

Point Of Care ◽

High Sensitivity ◽

Detection Methods ◽

Molecular Testing ◽

Practical Applications ◽

Food Industries ◽

Resource Limited ◽

Point Of Care Diagnostics ◽

Agriculture And Food

As the COVID-19 pandemic continues, people are becoming infected at an alarming rate, individuals are unknowingly spreading disease, and more lives are lost every day. There is an immediate need for a simple, rapid, early and sensitive point-of-care testing for COVID-19 disease. However, current testing approaches do not meet such need. Recently, clustered regularly interspaced short palindromic repeats (CRISPR)-based detection methods have received substantial attention for nucleic acid-based molecular testing due to their simplicity, high sensitivity and specificity. This review explores the various CRISPR-based COVID-19 detection methods and related diagnostic devices. As with any emerging technology, CRISPR/Cas-based nucleic acid testing methods have several challenges that must be overcome for practical applications in clinics and hospitals. More importantly, these detection methods are not limited to COVID-19 but can be applied to detect any type of pathogen, virus, and fungi that may threaten humans, agriculture, and food industries in resource-limited settings. CRISPR/Cas-based detection methods have the potential to become simpler, more reliable, more affordable, and faster in the near future, which is highly important for achieving point-of-care diagnostics.

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Reusable Surface Molecular Imprint Biosensors Aided by Naturally Occurring Surface Roughness Indices for Point-of-Care Diagnostics

MRS Advances ◽

10.1557/adv.2019.138 ◽

2019 ◽

Vol 4 (22) ◽

pp. 1299-1308 ◽

Cited By ~ 1

Author(s):

Yehoshua Auerbach ◽

Rebecca Isseroff ◽

Nicholas Clayton ◽

Miguel Hulyalkar ◽

Andrew Todt ◽

...

Keyword(s):

Real Time ◽

Molecular Imprinting ◽

Point Of Care ◽

High Sensitivity ◽

Cost Effective ◽

Stem Cell Differentiation ◽

Diverse Range ◽

Point Of Care Diagnostics ◽

Molecular Imprint ◽

Detection Of Biomarkers

ABSTRACTWe have shown that molecular imprinting (MI) technology can be used to produce sensitive, robust, cost-effective biosensing systems with a real-time electrochemical readout that can be utilized for point of care diagnostics. Real time detection of biomarkers is essential when rapid, critical decisions need to be made, such as in situations where public health is threatened. Our biosensor has high sensitivity compared to standard methods like ELISA, and results are obtained within minutes, using inexpensive, accessible potentiometric readout technology. These biosensors utilize surface molecular imprinting of a self-assembling monolayer of hydroxy-terminated alkanethiol chains which form a crystalline ‘lock-and-key’ structure around a target analyte, allowing the sensors to detect and differentiate between bio-macromolecules of similar size and shape with high selectivity and sensitivity. The sensors are extremely versatile and able to detect a diverse range of molecules of varied chemical composition and structure. To fully exploit the sensors’ advantages, especially in remote, economically disadvantaged areas, it is important to quantify their durability and reusability. Biosensor chips were created to test the viability of hemoglobin detection and to evaluate the potential for sensor reusability when washed after detection testing. The successful readsorption of hemoglobin even after washing, accompanied by cyclic voltammetry data indicating the preservation of the SAM, indicate that these biosensors are reusable, significantly augmenting the device’s value. Potential applications include the analysis of complex chemical and biological processes such as stem cell differentiation and on-the-spot detection of diseases such as Zika.

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Aqua-gel pH sensor: intelligent engineering and evaluation of pH sensor based on multi-factorial testing regimes

Sensor Review ◽

10.1108/sr-06-2017-0104 ◽

2019 ◽

Vol 39 (2) ◽

pp. 178-189 ◽

Cited By ~ 1

Author(s):

Mariam Mir ◽

Murtaza Najabat Ali ◽

Umar Ansari ◽

Patrick J. Smith ◽

Amber Zahoor ◽

...

Keyword(s):

Point Of Care ◽

Ph Sensor ◽

Ph Responsive ◽

Content Type ◽

Physico Chemical ◽

Ph Range ◽

Composition Ratios ◽

Gel Composition ◽

Conductometric Sensor

PurposeThe fabrication and characterization of a hydrogel-based conductometric sensor have been carried out. The purpose of this research is to fabricate a small robust hydrogel-based conductometric sensor for real-time monitoring of pH in the physiological range.Design/methodology/approachA pH-responsive Chitosan/Gelatin composite hydrogel has been used for this purpose. This study reports and analyzes the sensing response obtained from four hydrogel compositions with varying Chitosan/Gelatin ratios. The pH-responsive nature of the hydrogel has been mapped out through volumetric and conductometric tests. An attempt has been made to correlate these characteristics with the physico-chemical nature of the hydrogel through scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques.FindingsThe four hydrogel compositions differed on the basis of gel composition ratios; the conductometric analysis results prove that the sensor with the hydrogel composition (Chitosan 2 per cent, Gelatin 7 per cent, ratio 1:2) produces the best pH resolution in the pH range of 4 to 9. The sensing mechanisms and the differences obtained between individual sensor outputs have been discussed in detail. On the basis of this extensivein vitroassessment, it has been concluded that while key pendant functional groups contribute to pH-responsive characteristics of the hydrogel, the overall sensitivity of the sensors gel component to surrounding pH is also determined by the crystalline to amorphous ratio of the hydrogel composite, its interpenetrating cross-linked structure and the relative ratio of the hydrophilic to the pH-sensitive components.Practical implicationsThe conductometric sensor results prove that the fabricated sensor with the shortlisted hydrogel composition shows good sensitivity in the physiological pH range (4 to 9) and it has the potential for use in point of care medical devices for diagnostic purposes.Originality/valueThis is the first reported version of the fabrication and testing and analysis/comparison of a hydrogel-based conductometric sensor based on this composition. The work is original and has not been replicated anywhere.

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A nanofluidic device for rapid and multiplexed SARS-CoV-2 serological antibody detection

10.21203/rs.3.rs-537056/v1 ◽

2021 ◽

Author(s):

Thomas Mortelmans ◽

Dimitrios Kazazis ◽

Celestino Padeste ◽

Philipp Berger ◽

Xiaodan Li ◽

...

Keyword(s):

Influenza A ◽

Point Of Care ◽

Simultaneous Detection ◽

High Sensitivity ◽

Modern Society ◽

Antibody Detection ◽

Multiplexed Detection ◽

Viral Spread ◽

Point Of Care Diagnostics ◽

Nanofluidic Device

Abstract The outbreak of COVID-19 has led to a substantial death toll and has hindered the functioning of modern society, sending the world into a medical and economic crisis1,2. This underlined the importance of point-of-care diagnostics, as well as accurate, cost-effective serological antibody tests as well as point-of-care diagnostics to monitor the viral spread and contain pandemics and endemics. Here, we present a three-dimensional (3D) nanofluidic device for rapid and multiplexed detection of viral antibodies. The device is designed to size-dependently immobilize particles from a multi-particle mixture at predefined positions in nanochannels through capillary forces only, resulting in distinct trapping lines. We show that individual lines can be used as an on-chip fluorescence-linked immunosorbent assay for multiplexed detection of serological immunoglobulin antibodies against viral proteins with high sensitivity. Further device versatility is exhibited by on-bead color multiplexing for simultaneous detection of IgG and IgM antibodies in convalescent human serum and by concurrent detection of anti-spike (SARS-CoV-2) and anti-hemagglutinin (Influenza A) antibodies. The device’s applications can be further extended to detect a plethora of diseases simultaneously in a reliable and straightforward manner.

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FBG Multifunctional pH Sensor - Monitoring the pH Rain in Cultural Heritage

ACTA IMEKO ◽

10.21014/acta_imeko.v7i3.560 ◽

2018 ◽

Vol 7 (3) ◽

pp. 24 ◽

Cited By ~ 8

Author(s):

Lorenzo Dinia ◽

Fabio Mangini ◽

Marco Muzi ◽

Fabrizio Frezza

Keyword(s):

Ph Sensor ◽

High Sensitivity ◽

Fiber Optic Sensor ◽

Archaeological Sites ◽

Ph Responsive ◽

New Era ◽

Optic Sensor ◽

Corrosion Phenomenon ◽

And Control ◽

Sensor Monitoring

A new era of pollution requires an important focus on the conservation of archaeological sites and monuments. In the last years great efforts were required to develop various sensors for different tasks. The fiber Bragg grating (FBG) was one of the most studied thanks to the multitude of applications and the surprising performances. An original fiber optic sensor that combines the fiber Bragg gratings<strong> </strong>with a pH responsive polymer coating for monitoring the pH of the rains on critical and prestigious monuments is proposed. The core consists of four different materials, which makes the sensor very innovative and allowing it to reach a high sensitivity. In this study, the setup arrangement of the optical sensor is modeled with COMSOL Multiphysics (Wave Optics Module), based on the FEM (Finite Element Method) solver. Monitoring the pH of water can be used by experts to predict and control the corrosion phenomenon of specific materials, especially limestone and marble, thus scheduling the timely restoration.

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Point-of-Care Testing for Multiple Cardiac Markers Based on a Snail-Shaped Microfluidic Chip

Frontiers in Chemistry ◽

10.3389/fchem.2021.741058 ◽

2021 ◽

Vol 9 ◽

Author(s):

Binfeng Yin ◽

Xinhua Wan ◽

Changcheng Qian ◽

A. S. M. Muhtasim Fuad Sohan ◽

Songbai Wang ◽

...

Keyword(s):

Microfluidic Chip ◽

Point Of Care ◽

Mechanical Valve ◽

High Sensitivity ◽

Base Layer ◽

Cardiac Markers ◽

Point Of Care Testing ◽

Experimental Conditions ◽

Long Time ◽

Low Sensitivity

Existing methods for detecting cardiac markers are difficult to be applied in point-of-care testing (POCT) due to complex operation, long time consumption, and low sensitivity. Here, we report a snail-shaped microfluidic chip (SMC) for the multiplex detection of cTnI, CK-MB, and Myo with high sensitivity and a short detection time. The SMC consists of a sandwich structure: a channel layer with a mixer and reaction zone, a reaction layer coated with capture antibodies, and a base layer. The opening or closing of the microchannels is realized by controlling the downward movement of the press-type mechanical valve. The chemiluminescence method was used as a signal readout, and the experimental conditions were optimized. SMC could detect cTnI, CK-MB, and Myo at concentrations as low as 1.02, 1.37, and 4.15. The SMC will be a promising platform for a simultaneous determination of multianalytes and shows a potential application in POCT.

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