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3D-FDTD modelling of optical biosensing based on gold-coated nanoporous anodic alumina
摘要： The suitability of using gold-coated nanoporous anodic alumina structures as a platform for reflectometry-based plasmonic biosensors is investigated by numerical simulation. Reflectance spectra of such structures has been obtained using 3D-FDTD while the sensing capabilities have been evaluated as the change in spectra upon the adsorption of a layer of a biological-related molecule (biolayer) on the gold coating and inner pore surface. Results show that the gold-coated nanoporous structure enables the coupling of normally incident light to a localized surface plasmon resonance, and that such resonance shifts upon the adsorption of the biolayer. A sensitivity can be defined as the resonance wavelength shift with the biolayer refractive index. It is demonstrated that smaller gold coating thicknesses result in an increase in sensitivity, but at the cost of a decrease in the resonance sharpness, what suggests the existence of an optimal gold coating thickness.
关键词： Gold-coated nanoporous anodic alumina,Biolayer,FDTD simulation,Reflectometry-based plasmonic biosensor
更新于2025-09-10 09:29:36
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Liquid Crystals: A Novel Approach for Cancer Detection and Treatment
摘要： Liquid crystals are defined as the fourth state of matter forming between solid and liquid states. Earlier the applications of liquid crystals were confined to electronic instruments, but recent research findings suggest multiple applications of liquid crystals in biology and medicine. Here, the purpose of this review article is to discuss the potential biological impacts of liquid crystals in the diagnosis and prognosis of cancer along with the risk assessment. In this review, we also discussed the recent advances of liquid crystals in cancer biomarker detection and treatment in multiple cell line models. Cases reviewed here will demonstrate that cancer diagnostics based on the multidisciplinary technology and intriguingly utilization of liquid crystals may become an alternative to regular cancer detection methodologies. Additionally, we discussed the formidable challenges and problems in applying liquid crystal technologies. Solving these problems will require great effort and the way forward is through the multidisciplinary collaboration of physicists, biologists, chemists, material-scientists, clinicians, and engineers. The triumphant outcome of these liquid crystals and their applications in cancer research would be convenient testing for the detection of cancer and may result in treating the cancer patients non-invasively.
关键词： biosensor,biomarker,antitumor drug,liquid crystals,cancers
更新于2025-09-10 09:29:36
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Design and numerical analysis of a graphene-coated fiber-optic SPR biosensor using tungsten disulfide
摘要： This article provides a simple hybrid design and rigorous numerical analysis of a fiber optic–based surface plasmon resonance (SPR) biosensor for DNA hybridization. The sensor core and both sides of the cladding are constructed with optical fiber, whereas the middle portion of the cladding is filled with the proposed hybrid of silver, tungsten disulfide (WS2), graphene, and a sensing medium. To the best of our knowledge, this is the first demonstration of such a highly sensitive SPR biosensor using WS2 for sensing DNA hybridization. The sensitivity, detection accuracy, and figure of merit are considered as the performance parameters and are analyzed in detail. The analyses reveal an impressive enhancement of the overall performance of the proposed sensor. Insertion of a WS2 layer between silver and graphene provides a sensor with sensitivity higher than that of other sensors reported to date. Additionally, concurrent improvement of all performance parameters is shown by this hybrid sensor, which is not the case for sensors based only on graphene. An increased number of graphene-only layers increases the sensitivity and decreases the detection accuracy and figure of merit. Numerical analysis shows that the variation of the SPR angle for mismatched DNA strands is quite negligible, whereas that for complementary DNA strands is considerable, which is essential for proper detection of DNA hybridization. Therefore, the proposed biosensor opens a new window toward detection of biomolecular interactions.
关键词： DNA hybridization,transmittance,surface plasmon resonance angle,Biosensor,sensitivity,tungsten disulfide
更新于2025-09-09 09:28:46
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A novel three-dimensional microTAS chip for ultra-selective single base mismatched Cryptosporidium DNA biosensor
摘要： The development of new rapid and reliable detection technology of Cryptosporidium, a deadly waterborne pathogen, using a three-dimensional micro total analysis systems (3D μTAS) is the main goal of this work. An approach to enhance DNA detection on a patterned configurable 3D μTAS electrochemical DNA biosensor to human genotype of Cryptosporidium was successfully developed in present study. A novel 3D μTAS, comprising three layers, was fabricated to achieve better result comparing the commercial SPE. The first layer was consisted a circular gold coated area (gold dot) in the center of a PI sheet and the third layer was consisted of a common homemade screen printed electrode (SPE). The second layer was included PDMS channels and reservoir for sample delivery. The biosensor was fabricated on the gold dot of the first layer and electrochemical signal was recorded using the differential pulse voltammetry (DPV) and impedance methods on the third layer and the results were compared with biosensor fabricated on commercial SPE. The calibration curve of 3D μTAS DNA biosensor shows a detection limit of 1.8 ng/mL and a sensitivity of 12.844 μA/(μg mL-1) in a linear range of 2.5 ng/mL to 0.1 μg/mL, which are 10 times higher detection limit and 23 higher sensitivity of commercial SPE in a similar linear range. The specificity of prepared DNA sensor was conducted by using non-complementary, single, three and five mismatches strands and the potential of the biosensor in discriminating single mismatch detection was experimentally appraised.
关键词： Cryptosporidium,electrochemical DNA biosensor,E. Coli DNA,3D micro total analysis systems (3D μTAS)
更新于2025-09-09 09:28:46
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Characterization of functionalized glass and indium tin oxide surfaces as substrates for super-resolution microscopy
摘要： Modern high-throughput biosensors with sensitivity down to a single analyte molecule may be possible with single-molecule localization microscopy (SMLM). Functionalized surfaces can be fabricated with self-assembly monolayer chemistry on indium tin oxide (ITO) substrates but not glass. However, characterizations of SMLM-compatible fluorophores are primarily performed on glass substrates. Here we collect single-molecule kinetics data of isolated Alexa Fluor 647 molecules on bare and functionalized glass and ITO surfaces. Extracting the photophysical dynamics of the fluorophores allows direct comparison of behavior of this dye on these substrates and fitting data to a model that accounts for multiple reversible dark states. All surfaces had sensitivity sufficient to image single fluorophore molecules. Photophysical kinetics observed are similar between the two substrates. The photon yield from individual fluorophores was greatest on bare glass, but functionalized ITO surfaces showed superior yield to functionalized glass surfaces and nearly matched the yield of bare glass. Together these results indicate functionalized ITO as a promising substrate for modern single-molecule biosensors.
关键词： indium tin oxide,super-resolution microscopy,biosensor,single-molecule imaging
更新于2025-09-09 09:28:46
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Label-free protein quantitation by dielectric spectroscopy of dual-frequency liquid crystal
摘要： A dual-frequency-liquid-crystal (DFLC)-based biosensor was developed and its frequency-dependent dielectric properties were exploited to detect and quantitate a protein standard, bovine serum albumin (BSA). By analyzing the dielectric spectra of DFLC in the presence of BSA at various concentrations, we found that the difference in dielectric permittivity between the high- and low-frequency regimes is correlated to BSA concentration, thereby permitting a DFLC-based protein quantitative method. The dielectric properties of DFLCs are fundamental in the design of liquid crystal displays and fast-switching devices. Results from this study demonstrate the extended potential of the frequency-revertible dielectric anisotropy of DFLC in biosensing and protein quantitation.
关键词： Dielectric spectroscopy,Protein,LC-based biosensor,Bovine serum albumin,Dual-frequency liquid crystal
更新于2025-09-09 09:28:46
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Carbon-Dot-Based Ratiometric Fluorescence Glucose Biosensor
摘要： A ratiometric fluorescence glucose biosensor based on carbon dots (CDs) and rhodamine 6G (Rh6G) was developed both as an aqueous solution and as a crosslinked poly(acrylic acid) solid-state film. A ratiometric fluorescence color change was realized by fluorescence quenching due to the bienzymatic reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP) with glucose. When excited at 360 nm, the blue fluorescence emission of the CDs, prepared by a solvothermal method with citric acid and ethylene diamine, was quenched by the bienzymatic reaction with glucose, whereas the fluorescence of Rh6G was inert to glucose. Thus, a ratiometric fluorescence color change from blue to green was observed as the glucose concentration increased. The optimized CD/Rh6G/GOx/HRP aqueous solution showed a linear range of 0.1–500 μM with a limit of detection (LOD) of 0.04 μM, good selectivity for glucose over the major ingredients in human blood and could be used with human blood serum. A stable solid-state biosensor film was fabricated by immobilization of CD/Rh6G/GOx/HRP in the hydrogel film prepared by ultraviolet curing of a mixture of acrylic acid and diacrylated poly(ethylene glycol) (70:30, w/w). Compared to the CD/Rh6G/GOx/HRP aqueous solution, the hydrogel film showed a similar ratiometric fluorescence color change, sensitivity (linear range of 0.5–500 μM with an LOD of 0.08 μM), and selectivity. Further, the solid-state glucose biosensor film was inherently stable and could be used whenever needed, overcoming the instability of the aqueous solution (owing to aggregation, enzyme denaturation, etc.). These ratiometric biosensors increase the ability to detect glucose using the naked eye compared to simple turn-on or turn-off modes. Thus, this approach expands the potential applications of CDs in biosensors to provide more convenient and practical detection methods.
关键词： glucose,ratiometric,carbon dot,fluorescence,biosensor,enzyme
更新于2025-09-09 09:28:46
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Surface regeneration and reusability of label-free DNA biosensors based on weak polyelectrolyte-modified capacitive field-effect structures
摘要： The reusability of capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensors modified with a cationic weak polyelectrolyte (poly(allylamine hydrochloride) (PAH)) for the label-free electrical detection of single-stranded DNA (ssDNA), in-solution- and on-chip-hybridized double-stranded DNA (dsDNA) has been studied. It has been demonstrated that via simply regeneration of the gate surface of the EIS sensor by means of an electrostatic adsorption of a new PAH layer, the same biosensor can be reused for at least five DNA-detection measurements. Because of the reversal of the charge sign of the outermost layer after each surface modification with the cationic PAH or negatively charged DNA molecules, the EIS-biosensor signal exhibits a zigzag-like behavior. The amplitude of the signal changes has a tendency to decrease with increasing number of macromolecular layers. The direction of the EIS-signal shifts can serve as an indicator for a successful DNA-immobilization or -hybridization process. In addition, we observed that the EIS-signal changes induced by each surface-modification step (PAH adsorption, immobilization of ssDNA or dsDNA molecules and on-chip hybridization of complementary target cDNA) is decreased with increasing the ionic strength of the measurement solution, due to the more efficient macromolecular charge-screening by counter ions. The results of field-effect experiments were supported by fluorescence-intensity measurements of the PAH- or DNA-modified EIS surface using various fluorescence dyes.
关键词： charge screening,label-free,field-effect sensor,DNA biosensor,reusability,weak polyelectrolyte
更新于2025-09-09 09:28:46
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Non-Invasive Diagnosis of Diabetes by Volatile Organic Compounds in Urine Using FAIMS and Fox4000 Electronic Nose
摘要： The electronic nose (eNose) is an instrument designed to mimic the human olfactory system. Usage of eNose in medical applications is more popular than ever, due to its low costs and non-invasive nature. The eNose sniffs the gases and vapours that emanate from human waste (urine, breath, and stool) for the diagnosis of variety of diseases. Diabetes mellitus type 2 (DM2) affects 8.3% of adults in the world, with 43% being underdiagnosed, resulting in 4.9 million deaths per year. In this study, we investigated the potential of urinary volatile organic compounds (VOCs) as novel non-invasive diagnostic biomarker for diabetes. In addition, we investigated the influence of sample age on the diagnostic accuracy of urinary VOCs. We analysed 140 urine samples (73 DM2, 67 healthy) with Field-Asymmetric Ion Mobility Spectrometry (FAIMS); a type of eNose; and FOX 4000 (AlphaM.O.S, Toulouse, France). Urine samples were collected at UHCW NHS Trust clinics over 4 years and stored at ?80 ?C within two hours of collection. Four different classifiers were used for classification, specifically Sparse Logistic Regression, Random Forest, Gaussian Process, and Support Vector on both FAIMS and FOX4000. Both eNoses showed their capability of diagnosing DM2 from controls and the effect of sample age on the discrimination. FAIMS samples were analysed for all samples aged 0–4 years (AUC: 88%, sensitivity: 87%, specificity: 82%) and then sub group samples aged less than a year (AUC (Area Under the Curve): 94%, Sensitivity: 92%, specificity: 100%). FOX4000 samples were analysed for all samples aged 0–4 years (AUC: 85%, sensitivity: 77%, specificity: 85%) and a sub group samples aged less than 18 months: (AUC: 94%, sensitivity: 90%, specificity: 89%). We demonstrated that FAIMS and FOX 4000 eNoses can discriminate DM2 from controls using urinary VOCs. In addition, we showed that urine sample age affects discriminative accuracy.
关键词： biosensor,urine sample,medical application,electronic nose,non-invasive diagnosis,FOX 4000,volatile organic compounds (VOCs),FAIMS,diabetes
更新于2025-09-09 09:28:46
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Sensitivity enhancement of SPR optical biosensor based on Graphene–MoS2 structure with nanocomposite layer
摘要： The optical plasmonic biosensors are an important research item in the field of bio-photonics. The graphene-molybdenum disulfide (MoS2) based hybrid structures are very useful in designing and fabrication of the high sensitive biosensors. In this paper, we designed hetero-structured Air/MoS2/Nanocomposite/MoS2/Graphene as an optical biosensor with high sensitivity. The proposed configuration for this Surface Plasmon Resonance (SPR) biosensor is Otto configuration. Herein, the enhancement sensitivity of this proposed SPR biosensor is investigated in different arrangement of layers. The influence of the refractive index of the coupling prism, the thickness of the nanocomposite layer, the constituent components of the nanocomposite layer and the number of the MoS2 layer is investigated and the optimal values is calculated for the biosensor with maximum sensitivity. The maximum sensitivity ～200°/RIU is achieved with six layers of MoS2 layer and a nanocomposite layer containing the gold nanoparticles and TiO2 as host dielectric.
关键词： Sensitivity,Biosensor,Nanocomposite,Graphene,Surface plasmon resonance,Molybdenum disulfide
更新于2025-09-09 09:28:46