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Editorial

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5 pages, 176 KiB

Open AccessEditorial

Editorial to the Special Issue “Advances in Optical Biosensors and Chemical Sensors”

by Flavio Esposito, Stefania Campopiano and Agostino Iadicicco

Biosensors 2024, 14(9), 447; https://doi.org/10.3390/bios14090447 - 19 Sep 2024

Viewed by 780

Abstract

Optical biosensors and optical chemical sensors are innovative analytical tools that utilize light-based techniques to detect and quantify a plethora of biological and chemical substances [...] Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

Research

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17 pages, 7062 KiB

Open AccessArticle

Surface-Enhanced Spatially Offset Raman Spectroscopy in Tissue

by Dayle Kotturi, Sureyya Paterson and Mike McShane

Biosensors 2024, 14(2), 81; https://doi.org/10.3390/bios14020081 - 2 Feb 2024

Cited by 1 | Viewed by 1773

Abstract

One aim of personalized medicine is to use continuous or on-demand monitoring of metabolites to adjust prescription dosages in real time. Surface-enhanced spatially offset Raman spectroscopy (SESORS) is an optical technique capable of detecting surface-enhanced Raman spectroscopy (SERS)-active targets under a barrier, which [...] Read more.

One aim of personalized medicine is to use continuous or on-demand monitoring of metabolites to adjust prescription dosages in real time. Surface-enhanced spatially offset Raman spectroscopy (SESORS) is an optical technique capable of detecting surface-enhanced Raman spectroscopy (SERS)-active targets under a barrier, which may enable frequent metabolite monitoring. Here we investigate how the intensity of the signal from SERS-active material varies spatially through tissue, both experimentally and in a computational model. Implant-sized, SERS-active hydrogel was placed under different thicknesses of contiguous tissue. Emission spectra were collected at the air-tissue boundary over a range of offsets from the excitation site. New features were added to the Monte Carlo light-tissue interaction model to modify the optical properties after inelastic scattering and to calculate the distribution of photons as they exit the model. The Raman signals were detectable through all barrier thicknesses, with strongest emission for the case of 0 mm offset between the excitation and detector. A steep decline in the signal intensities occurred for offsets greater than 2 mm. These results did not match published SORS work (where targets were much larger than an implant). However, the model and experimental results agree in showing the greatest intensities at 0 mm offset and a steep gradient in the intensities with increasing offset. Also, the model showed an increase in the number of photons when the new, longer wavelengths were used following the Stokes shift for scattering and the graphical display of the exiting photons was helpful in the determination and confirmation of the optimal offset. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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15 pages, 4368 KiB

Open AccessEditor’s ChoiceArticle

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

by Lydia Colvin, Dandan Tu, Darin Dunlap, Alberto Rios and Gerard Coté

Biosensors 2023, 13(8), 788; https://doi.org/10.3390/bios13080788 - 4 Aug 2023

Cited by 3 | Viewed by 2541

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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10 pages, 2548 KiB

Open AccessCommunication

Coumarin-Based Fluorescence Probe for Differentiated Detection of Biothiols and Its Bioimaging in Cells

by Wei Du, Xiu-Lin Gong, Yang Tian, Xi Zhu, Yu Peng and Ya-Wen Wang

Biosensors 2023, 13(4), 447; https://doi.org/10.3390/bios13040447 - 31 Mar 2023

Cited by 9 | Viewed by 2079

Abstract

In this work, a coumarin derivative, SWJT-14, was synthesized as a fluorescence probe to distinguish cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in aqueous solutions. The detection limit of Cys, Hcy and GSH for the probe was 0.02 μM, 0.42 μM and [...] Read more.

In this work, a coumarin derivative, SWJT-14, was synthesized as a fluorescence probe to distinguish cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in aqueous solutions. The detection limit of Cys, Hcy and GSH for the probe was 0.02 μM, 0.42 μM and 0.92 μM, respectively, which was lower than biothiols in cells. The probe reacted with biothiols to generate different products with different conjugated structures. Additionally, it could distinguish Cys, Hcy and GSH using fluorescence and UV-Vis spectra. The detection mechanism was confirmed by MS. SWJT-14 was successfully used in cellular experiments and detected both endogenous and exogenous biothiols. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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18 pages, 4383 KiB

Open AccessArticle

Non-Destructive and Non-Invasive Measurement of Ethanol and Toxic Alcohol Strengths in Beverages and Spirits Using Portable Raman Spectroscopy

by Panagiota Papaspyridakou, Panagiota Giannoutsou and Malvina G. Orkoula

Biosensors 2023, 13(1), 135; https://doi.org/10.3390/bios13010135 - 13 Jan 2023

Cited by 6 | Viewed by 3326

Abstract

The measurement of ethanol and toxic alcohol (methanol and isopropanol) strengths in beverages and spirits is crucial for health reasons but also for the identification of adulterated products. Many methodologies have been reported in the literature, based mainly on chromatographic and on spectroscopic [...] Read more.

The measurement of ethanol and toxic alcohol (methanol and isopropanol) strengths in beverages and spirits is crucial for health reasons but also for the identification of adulterated products. Many methodologies have been reported in the literature, based mainly on chromatographic and on spectroscopic techniques. Chromatographic techniques are laborious and time-consuming, while spectroscopic techniques are rapid and need no special sample pretreatment. All techniques were only applied to off-line or at-line manner. In the present work, Raman spectroscopy was used for fast and non-destructive measurements. A “through the container” method was developed for a non-invasive analysis, i.e., analysis without unsealing the bottles. This method, coupled with a miniature portable Raman, can serve for in-line measurements in a production line. The optimum laser focus for maximum spirit signal and minimum glass-wall signal was investigated. Calibration curves for the alcohols of interest were constructed and validated. The limits of detections were calculated and proved to be lower than the legitimate values. The influences of the liquor color and the bottle color, shape, and thickness were checked. Twenty-eight alcoholic products were studied. The concentrations found were compared against the nominal values (from the bottle labels). Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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16 pages, 10116 KiB

Open AccessArticle

A Reversible Optical Sensor Film for Mercury Ions Discrimination Based on Isoxazolidine Derivative and Exhibiting pH Sensing

by Reham Ali, Siwar Ghannay, Sabri Messaoudi, Fahad M. Alminderej, Kaïss Aouadi and Sayed M. Saleh

Biosensors 2022, 12(11), 1028; https://doi.org/10.3390/bios12111028 - 16 Nov 2022

Cited by 8 | Viewed by 2160

Abstract

We developed a new optical sensor for tracing Hg(II) ions. The detection affinity examines within a concentration range of 0–4.0 µM Hg(II). The sensor film is based on Methyl 2-hydroxy-3-(((2S,2’R,3a’S,5R)-2-isopropyl-5,5’-dimethyl-4’-oxotetrahydro-2’H-spiro[cy-clohexane-1,6’-im-idazo[1,5-b]isoxazol]-2’-yl)methyl)-5-methylbenzoate (IXZD). The novel synthesized compound could be utilized as an optical turn-on chemosensor [...] Read more.

We developed a new optical sensor for tracing Hg(II) ions. The detection affinity examines within a concentration range of 0–4.0 µM Hg(II). The sensor film is based on Methyl 2-hydroxy-3-(((2S,2’R,3a’S,5R)-2-isopropyl-5,5’-dimethyl-4’-oxotetrahydro-2’H-spiro[cy-clohexane-1,6’-im-idazo[1,5-b]isoxazol]-2’-yl)methyl)-5-methylbenzoate (IXZD). The novel synthesized compound could be utilized as an optical turn-on chemosensor for pH. The emission intensity is highly enhanced for the deprotonated form concerning the protonated form. IXZD probe has a characteristic fluorescence peak at 481 nm under excitation of 351 nm with large Stocks shift of approximately 130 nm. In addition, the binding process of IXZD:Hg(II) presents a 1:1 molar ratio which is proved by the large quench of the 481 nm emission peak of IXZD and the growth of a new emission peak at 399 nm (blue shift). The binding configurations with one Hg(II) cation and its electronic characteristics were investigated by applying the Density Functional Theory (DFT) and the time-dependent DFT (TDDFT) calculations. Density functional theory (DFT) and the time-dependent DFT (TDDFT) theoretical results were provided to examine Hg(II)-IXZD structures and their electronic properties in solution. The developed chemical sensor was offered based on the intramolecular charge transfer (ICT) mechanism. The sensor film has a significantly low limit of detection (LOD) for Hg(II) of 0.025 μM in pH 7.4, with a relative standard deviation RSD_r (1%, n = 3). Lastly, the IXZD shows effective binding affinity to mercury ions, and the binding constant K_b was estimated to be 5.80 × 10⁵ M⁻¹. Hence, this developed optical sensor film has a significant efficiency for tracing mercury ions based on IXZD molecule-doped sensor film. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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14 pages, 7090 KiB

Open AccessArticle

Dual Optical Nanosensor Based on Ormosil Nanoparticles for Monitoring O₂ and pH

by Reham Ali

Biosensors 2022, 12(11), 1011; https://doi.org/10.3390/bios12111011 - 12 Nov 2022

Cited by 5 | Viewed by 2095

Abstract

Monitoring O₂ and pH has excellent potential in different sensing applications, especially in biological and clinical applications. This report presents a protocol for synthesizing an optical dual nanosensor for those two parameters. The organically modified silica (ormosil) nanoparticles were prepared based on [...] Read more.

Monitoring O₂ and pH has excellent potential in different sensing applications, especially in biological and clinical applications. This report presents a protocol for synthesizing an optical dual nanosensor for those two parameters. The organically modified silica (ormosil) nanoparticles were prepared based on phenytrimethoxysilane in an aqueous solution using an acid-base one-pot strategy. Ormosil was selected as a lipophilic matrix for loading fluorescent O₂-sensitive dye platinum(II)-tetrakis-(pentafluorophenyl) porphyrin (Pt-TPFPP), which was quenched in the presence of O₂ gas and exhibited a considerable detection proficiency within a percentage range of (0–100%) O₂. Commercially available drug ingredient salicylamide was labeled on the surface of the nanoparticles using a coupling agent (3-glycidoxypropyl) trimethoxysilane (GPTMS). For measuring pH, salicylamide acted for the first time as a pH-sensitive probe based on a turn-on process with increasing pH. The nanosensor displayed a significant pH detection efficiency in the range of (pH = 6–10). Salicylamide turn-on fluorescence was attributed to the excited state intramolecular transfer (ESIPT) process followed by the inter charge transfer (ICT). The presented dual nanosensor opens new opportunities as a promising candidate material for industrial systems and medical applications. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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Review

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37 pages, 11105 KiB

Open AccessReview

Advances in Tapered Optical Fiber Sensor Structures: From Conventional to Novel and Emerging

by Wen Zhang, Xianzheng Lang, Xuecheng Liu, Guoru Li, Ragini Singh, Bingyuan Zhang and Santosh Kumar

Biosensors 2023, 13(6), 644; https://doi.org/10.3390/bios13060644 - 12 Jun 2023

Cited by 18 | Viewed by 4302

Abstract

Optical fiber sensors based on tapered optical fiber (TOF) structure have attracted a considerable amount of attention from researchers due to the advantages of simple fabrication, high stability, and diverse structures, and have great potential for applications in many fields such as physics, [...] Read more.

Optical fiber sensors based on tapered optical fiber (TOF) structure have attracted a considerable amount of attention from researchers due to the advantages of simple fabrication, high stability, and diverse structures, and have great potential for applications in many fields such as physics, chemistry, and biology. Compared with conventional optical fibers, TOF with their unique structural characteristics significantly improves the sensitivity and response speed of fiber-optic sensors and broadens the application range. This review presents an overview of the latest research status and characteristics of fiber-optic sensors and TOF sensors. Then, the working principle of TOF sensors, fabrication schemes of TOF structures, novel TOF structures in recent years, and the growing emerging application areas are described. Finally, the development trends and challenges of TOF sensors are prospected. The objective of this review is to convey novel perspectives and strategies for the performance optimization and design of TOF sensors based on fiber-optic sensing technologies. Full article

(This article belongs to the Special Issue Advances in Optical Biosensors and Chemical Sensors)

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