Foodborne illness outbreaks caused by the consumption of food contaminated with harmful bacteria has drastically increased in the past decades. Therefore, detection of harmful bacteria in the food ...has become an important factor for the recognition and prevention of problems associated with food safety and public health. Staphylococcus aureus is one of the most commonly isolated foodborne pathogen and it is considered as a major cause of foodborne illnesses worldwide. A number of different methods have been developed for the detection and identification of S. aureus in food samples. However, some of these methods are laborious and time-consuming and are not suitable for on-site applications. Therefore, it is highly important to develop rapid and more approachable detection methods. In the last decade, biosensors have gained popularity as an attractive alternative method and now considered as one of most rapid and on-site applicable methods. An overview of the biosensor based methods used for the detection of S. aureus is presented herein. This review focuses on the state-of-the-art biosensor methods towards the detection and quantification of S. aureus, and discusses the most commonly used biosensor methods based on the transducing mode, such as electrochemical, optical, and mass-based biosensors.
•Recent advances in development of biosensors for detection of S. aureus are discussed.•An overview of biosensors based on transducing mode is presented.•Electrochemical, optical, and mass-based biosensors are mainly discussed.
We demonstrate a smartphone based spectrometer design that is standalone and supported on a wireless platform. The device is inherently low-cost and the power consumption is minimal making it ...portable to carry out a range of studies in the field. All essential components of the device like the light source, spectrometer, filters, microcontroller and wireless circuits have been assembled in a housing of dimensions 88 mm × 37 mm × 22 mm and the entire device weighs 48 g. The resolution of the spectrometer is 15 nm, delivering accurate and repeatable measurements. The device has a dedicated app interface on the smartphone to communicate, receive, plot and analyze spectral data. The performance of the smartphone spectrometer is comparable to existing bench-top spectrometers in terms of stability and wavelength resolution. Validations of the device were carried out by demonstrating non-destructive ripeness testing in fruit samples. Ultra-Violet (UV) fluorescence from Chlorophyll present in the skin was measured across various apple varieties during the ripening process and correlated with destructive firmness tests. A satisfactory agreement was observed between ripeness and fluorescence signals. This demonstration is a step towards possible consumer, bio-sensing and diagnostic applications that can be carried out in a rapid manner.
A water-soluble thermochromic molecular switch with spectrally resolved fluorescence in its two interconvertible states can be assembled in three synthetic steps by integrating a fluorescent coumarin ...chromophore, a hydrophilic oligo(ethylene glycol) chain, and a switchable oxazole heterocycle in the same covalent skeleton. Measurements of its two emissions in separate detection channels of a fluorescence microscope permit the noninvasive and ratiometric sensing of temperature at the micrometer level with millisecond response in aqueous solutions and within hydrogel matrices. The ratiometric optical output of this fluorescent molecular switch overcomes the limitations of single-wavelength fluorescent probes and enables noninvasive temperature mapping at length scales that are not accessible to conventional thermometers based on physical contact.
Organophosphorus (OP) pesticides have been used widely as agricultural and household pest control agents for almost five decades and persist in our water resources, fruits, vegetables and processed ...food as health and environmental hazardous compounds. Thus, detection of these harmful OP pesticides at an ease with high sensitivity and selectivity is the need of hour. Bio-sensing technology meet these requirements and has been employed at a large scale for detection. The present review is aimed mainly to provide the overview of the past and recent advances occurred in the field of biosensor technology employed for the detection of these OP compounds. The review describes the principle and strategy of various OP biosensors including electrochemical (amperometric, potentiometric), thermal, piezoelectric, optical (fluorescence, Surface Plasmon Resonance (SPR)), microbial and DNA biosensors in detail. The electrochemical biosensors are generally, based on inhibition of enzyme, acetyl cholinesterase (AChE), butyryl cholinesterase (BChE), tyrosinase and alkaline phosphatase or enzyme (organophosphorus hydrolase, OPH)) catalyzed reaction. The detection limits and linearity range of various OP biosensors have also been compared. AChE inhibition based amperometric OP biosensors exhibited the lowest detection limit of 1 × 10−11 μM with a linearity range of 1.0 × 10−11 – 1.0 × 10−2 μM.
Scheme: Overview of bio-sensing techniques employed for the detection of organophosphorus (OP) compounds. Display omitted
•OP pesticides determination has great relevance in environmental monitoring and sustainable agriculture.•At large, various enzymes, AChE, BChE, tyrosinase, alkaline phosphatase inhibition based and OPH hydrolysis based biosensors has been fabricated so far.•AChE inhibition based amperometric OP biosensors have the lowest detection limit of 1 × 10−11 μM and linearity range of 1.0 × 10−11 – 1.0 × 10−2 μM among all the biosensors.
An all-in-one paper-based analytical device (PAD) was successfully developed for visual fluorescence detection of carcinoembryonic antigen (CEA) on CdTe/CdSe quantum dot (QD)-enzyme-impregnated paper ...by coupling with a bioresponsive controlled-release system from DNA-gated mesoporous silica nanocontainers (MSNs). The assay was carried out in a centrifuge tube by using glucose-loaded MSNs with a CEA aptamer and a QD-enzyme-paper attached on the lid. Initially, single-strand complementary DNA to a CEA aptamer was covalently conjugated to the aminated MSN, and then glucose (enzyme substrate) molecules were gated into the pore with the help of the aptamer. Glucose oxidase (GOD) and CdTe/CdSe QDs were coimmobilized on paper for the visual fluorescence signal output. Upon target CEA introduction in the detection cell, the analyte specifically reacted with the immobilized aptamer on the MSN to open the pore, thereby resulting in the glucose release. The released glucose was oxidized by the immobilized GOD on paper to produce gluconic acid and hydrogen peroxide, and the latter quenched the fluorescence of CdTe/CdSe QDs, which could be determined by the naked eye on a portable smartphone and a commercial fluorospectrometer. Under optimal conditions, the PAD-based sensing system enabled sensitive discrimination of target CEA against other biomarkers or proteins in a linear range of 0.05-20 ng mL
with a limit of detection of 6.7 pg mL
(ppt). In addition, our strategy displayed high specificity, good reproducibility, and acceptable accuracy for analyzing human serum specimens with a commercial human CEA ELISA kit. Importantly, this methodology offers promise for simple analysis of biological samples and is suitable for use in the mass production of miniaturized devices, thus opening new opportunities for protein diagnostics and biosecurity.
In recent years fluorescence correlation spectroscopy (FCS) has become a routine method for determining diffusion coefficients, chemical rate constants, molecular concentrations, fluorescence ...brightness, triplet state lifetimes, and other molecular parameters. FCS measures the spatial and temporal correlation of individual molecules with themselves and so provides a bridge between classical ensemble and contemporary single-molecule measurements. It also provides information on concentration and molecular number fluctuations for nonlinear reaction systems that complement single-molecule measurements. Typically implemented on a fluorescence microscope, FCS samples femtoliter volumes and so is especially useful for characterizing small dynamic systems such as biological cells. In addition to its practical utility, however, FCS provides a window on mesoscopic systems in which fluctuations from steady states not only provide the basis for the measurement but also can have important consequences for the behavior and evolution of the system. For example, a new and potentially interesting field for FCS studies could be the study of nonequilibrium steady states, especially in living cells.
Gemigliptin-Rosuvastatin single-pill combination is a promising therapeutic tool in the effective control of hyperglycemia and hypercholesterolemia. Organic sensors with high quantum yields have ...profoundly significant applications in the pharmaceutical industry, such as routine quality control of marketed formulations. Herein, the fluorescence sensor, 2-Morpholino-4,6-dimethyl nicotinonitrile 3, (λex; 226 nm, λem; 406 nm), was synthesized with a fluorescence quantum yield of 56.86% and fully characterized in our laboratory. This sensor showed high efficiency for the determination of Gemigliptin (GEM) and Rosuvastatin (RSV) traces through their stoichiometric interactions and simultaneously fractionated by selective solvation. The interaction between the stated analytes and sensor 3 was a quenching effect. Various experimental parameters and the turn-off mechanism were addressed. The adopted approach fulfilled the ICH validation criteria and showed linear satisfactory ranges, 0.2-2 and 0.1-1 μg/mL for GEM and RSV, respectively with nano-limits of detection less than 30 ng/mL for both analytes. The synthesized sensor has been successfully applied for GEM and RSV co-assessment in their synthetic polypill with excellent % recoveries of 98.83 ± 0.86 and 100.19 ± 0.64, respectively. No statistically significant difference between the results of the proposed and reported spectrophotometric methods in terms of the F- and t-tests. Ecological and whiteness appraisals of the proposed study were conducted via three novel approaches: the Greenness Index via Spider Diagram, the Analytical Greenness Metric, and the Red-Green-Blue 12 model. The aforementioned metrics proved the superiority of the adopted approach over the previously published one regarding eco-friendliness and sustainability. Our devised fluorimetric turn-off sensing method showed high sensitivity, selectivity, feasibility, and rapidity with minimal cost and environmental burden over other sophisticated techniques, making it reliable in quality control labs.
In this article, a novel triphenylamine-modified salicylaldehyde Schiff base 2-(((4-(diphenylamino)phenyl)imino)methyl)-4-(pyridine-4-yl)phenol (HL) was synthesized and structurally characterized. HL ...possessed D-π-A structure and exhibited typical AIE property in THF/H
O. It was applied to selectively recognize Cu
through an on-off mode in THF/H
O (1/9, v/v), and the fluorescence attenuation was attributed to a paramagnetic quenching effect of Cu
together with the abatement of HL aggregates. Hence, the detection limit achieved was as low as 1.32 × 10
M. The spectroscopic and ESI-HRMS results revealed a 1 : 2 complexation ratio of Cu
with HL. The mechanism for sensing Cu
was further confirmed by performing DFT calculations. Owing to the large affinity between Cu
and His, the resultant CuL2 system was further used to detect His
the off-on method based on the displacement of ligands. The detection limit for His reached 5.14 × 10
M. Furthermore, HL was available to prepare handy indicator papers for the on-site recognition of Cu
and His. Confocal fluorescent imaging demonstrated that HL could sequentially respond to intracellular Cu
and His.
Finding and preserving normal parathyroid glands or localizing and removing diseased parathyroid glands are crucial steps to successful thyroid and parathyroid operations. Using near-infrared ...fluorescence detection to identify parathyroid glands during thyroid and parathyroid operations has lately gained widespread recognition, with 2 Food and Drug Administration–cleared devices currently in the market. We aim to update the endocrine surgery community on how near-infrared fluorescence detection can be most optimally used for rapid intraoperative parathyroid gland identification or preservation.
A literature review was performed using the key terms: “parathyroid,” “near infrared,” and “fluorescence” in relevant search engines. Based on the reviewed literature and expert surgeons’ opinions, recommendations were formulated for applying near-infrared fluorescence detection to identify or preserve parathyroid glands during cervical endocrine surgery.
The scope of near-infrared fluorescence detection can be broadly categorized into (1) using near-infrared auto-fluorescence to identify or locate both healthy and diseased parathyroid glands, and (2) using contrast-enhanced near-infrared fluorescence to evaluate parathyroid gland perfusion. The benefits and pitfalls for both near-infrared–based approaches are described herein.
Near-infrared fluorescence detection appears helpful for identification and likely preservation of parathyroid glands. We hope these recommendations will be valuable to the practicing endocrine surgeon as they consider incorporating these intraoperative adjuncts in their surgical practice.
A water-soluble azo functionalized oligomeric chitosan reagent (β-NAC) has been developed for the visual detection and quantification of KMnO
at micromolar concentrations. The β-NAC sensor was also ...explored as a detection probe for the spectrophotometric and spectrofluorometric detection of several metal ions and anions. The synthesized reagent was characterized by TGA-DTA-DTG analysis, DLS studies, BET analysis, and spectral analysis. The β-NAC reagent produces conspicuous colours with different concentrations and different pH values of KMnO
solution. This provides evidence for high selectivity in the visual detection of KMnO
up to the micromolar level because of its interactions in the case of KMnO
only. The colour of the β-NAC reagent after interacting with KMnO
(10
M) changes from brown to blood red. Furthermore, the β-NAC sensor was employed for the spectrophotometric detection of KMnO
. The absorption spectrum of β-NAC shows a peak at 327 nm and on interacting with KMnO
, it shows a bathochromic shift to 331 nm. The intensity of the peak at 331 nm increases as the concentration of KMnO
was increased from 1 μM to 0.01 M. The detection and quantification limits in the spectrophotometric detection of KMnO
were found to be 4.55 μM and 15.17 μM, respectively. The results of pH studies show that there is a pH effect of the KMnO
solution on KMnO
detection. The stability of the complex was determined by investigating the effect of time on the absorption intensity. In the spectrofluorometric detection, the fluorescence intensity of β-NAC at the 427 nm emission maxima was decreased on adding KMnO
solution. The fluorescence quenching increased on increasing the KMnO
concentration from 1 μM to 0.008 M. The optimum pH for fluorescence quenching was found to be 8. The detection and quantification limits in the spectrofluorometric detection of KMnO
were found to be 0.967 μM and 3.223 μM, respectively. The Stern-Volmer constant value was found to be 41 366.2 L mol
, confirming the significant complexation between KMnO
and the β-NAC reagent. Interference studies were conducted to analyse the effect of various metal ions and anions on KMnO
detection. Electrochemical studies were also performed to analyse the mechanism of complex formation.
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