Naked-eye Method Research Articles

Naked-eye sensitive detection of nanoPET by pH-responsive colorimetric method based on dual-enzyme catalysis

A pH-responsive colorimetric method based on dual-enzyme catalysis for rapid and facile detection and quantification of nanoPET at environment-dependent concentration is proposed. The nanoPET was hydrolyzed by the synergistic catalysis of cutinase and lipase to terephthalic acid which can be sensitive detected using bromocresol purple as the indicator. The color changed from purple to bright yellow as the nanoPET detection concentration increased from 0 mg/mL to 2 mg/mL which can be detected by UV–Vis. This naked-eye method has a high sensitivity for nanoPET detection with the visual detection cutoff of 31.00 μg/mL, and has a good linearity in the range of 0 ∼ 1 mg/mL with LOD of 22.84 μg/mL. The reliability of this method is verified in the detection of nanoPET in lake water and beer samples, with an average recovery of 87.1 %. The as-developed dual-enzyme colorimetric chemosensor holds promising potential as a robust and effective platform for the sensitive detection of nanoPET.

Phage amplification coupled with loop-mediated isothermal amplification (PA-LAMP) for same-day detection of viable Salmonella Enteritidis in raw poultry meat

Salmonella Enteritidis is the main serotype responsible for human salmonellosis in the European Union. One of the main sources of Salmonella spp. in the food chain are poultry products, such as eggs or chicken meat. In recent years, molecular methods have become an alternative to culture dependent methods for the rapid screening of Salmonella spp. In this work, the strain S. Enteritidis S1400, and previously isolated and characterized bacteriophage PVP-SE2, were used to develop and evaluate a same-day detection method combining Phage Amplification and Loop-mediated isothermal amplification (PA-LAMP) to specifically detect viable S. Enteritidis in chicken breast. This method is based on the detection of the phage DNA rather than bacterial DNA. The virus is added to the sample during pre-enrichment in buffered peptone water, where it replicates in the presence of viable S. Enteritidis. The detection of phage DNA allows, on the one hand to detect viable bacteria, since viruses only replicate in them, and on the other hand to increase the sensitivity of the method since for each infected S. Enteritidis cell, hundreds of new viruses are produced. Two different PA-LAMP detection strategies were evaluated, a real time fluorescence and a naked-eye detection. The present method could down to 0.2 fg/μL of pure phage DNA and a concentration of viral particles of 2.2 log PFU/mL. After a short Salmonella recovery step of 3 h and a co-culture of 4 h of the samples with phage particles, both real-time fluorescence and naked-eye method showed a LoD95 of 6.6 CFU/25 g and a LoD50 of 1.5/25 g in spiked chicken breast samples. The entire detection process, including DNA extraction and LAMP analysis, can be completed in around 8 h. In the current proof-of-concept, the novel PA-LAMP obtained comparable results to those of the reference method ISO 6579, to detect Salmonella Enteritidis in poultry meat.

Improving the selective naked-eye detection of COVID-19 mediated by simultaneously using three different target oligonucleotides coated on plasmonic AuNPs/hexagonal Ag@AuNPs

The localized surface plasmon resonance (LSPR) phenomenon provides a versatile property in biosensor technology. This uncommon feature was utilized to produce a homogeneous optical biosensor to detect COVID-19 by the naked-eye readout. In this work, we synthesized two types of plasmonic nanoparticles: (i) AuNPs and (ii) hexagonal core-shell nanoparticles-Au shell on AgNPs (Au@AgNPs). We report herein the development of two colorimetric biosensors employing the efficient targeting and the binding ability for three regions of the COVID-19 genome, that is, S-gene, N-gene and E-gene, at the same time. Two AuNPs and Ag@AuNPs individually coated with three different targets oligonucleotide sequence (TOs) (AuNPs-TOs-mix and Ag@AuNPs-TOs-mix) for simultaneous detection of S-gene, N-gene and E-gene of the COVID-19 virus, using the LSPR and naked-eye methods in the laboratory and biological samples. The target COVID-19 genome RNA detected using the AuNPs-TOs-mix and Ag@AuNPs-TOs-mix can achieve the same sensitivity. The detection ranges by the AuNPs-TOs-mix and Ag@AuNPs-TOs-mix are both sufficiently improved in equal amounts in comparison to any of the AuNPs-TOs and Ag@AuNPs-TOs. The sensitivity of the current COVID-19 biosensors were 94% and 96% based on the number of positive samples detected for AuNPs-TOs-mix and Ag@AuNPs-TOs-mix, respectively. Moreover, all the real-time PCR confirmed negative samples obtained the same results by the biosensor; accordingly, the specificity of this approach got to 100%. The current study reports a selective, reliable, reproducible and visual ‘naked-eye’ detection of COVID-19, devoid of the requirement of any sophisticated instrumental techniques.Communicated by Ramaswamy H. Sarma

Investigating the AIE and water sensing properties of a concise naphthalimide fluorophore

A simple naphthalimide fluorophore NAP-H2O was designed and synthesized. Basic photophysical properties were investigated, especially found that the probe showed robust green fluorescence in water compared with that in various organic solvents, and the specific mechanism was conformed to be the aggregation induced emission (AIE) through dynamic light scattering (DLS) analysis, solid-state luminescence and fluorescence imaging. Accordingly, the capability of NAP-H2O for water sensing was examined, and good linear relationships between fluorescence intensities at the green emission band and the water content were obtained, enabling quantitative detection of water in organic solvents. The detection limits were calculated to be 0.004 % (v/v) in ACN, 0.117 % (v/v) in 1,4–dioxane, 0.028 % (v/v) in THF, 0.022 % (v/v) in DMF and 0.146 % (v/v) in DMSO, respectively. In addition, the probe presented fast response time within 5 s to water and good photostability. Furthermore, the probe was successfully applied for fast and naked-eye detection of water in organic solvents via test papers. This work provides a rapid, sensitive and naked-eye method for trace amount detection of water in organic solvents and has potential for practical applications.

A Comparative Study on Depth of Penetration Measurements in Diagnostic Ultrasounds Through the Adaptive SNR Threshold Method

Depth Of Penetration (DOP) has been investigated in the scientific literature as an informative parameter able to monitor over time both the sensitivity and the general performance of ultrasound (US) diagnostic systems. In common practice, this parameter may suffer from operator-related errors due to its visual assessment. Different image analysis algorithms have been proposed in the literature to address this issue. In this regard, the present work evaluates the Adaptive SNR Threshold Method (AdSTM) on six US diagnostic systems equipped with three US probe models, operating at four frequencies. Data were collected from a US phantom with two distinct zones with different attenuation coefficients. The AdSTM results were compared to the outcomes provided by the Naked Eye Method (NEM), which was performed by 5 non-medical observers. Despite the small population sample of observers, the obtained results were generally consistent across methods, and suggest the implementation of a calibration procedure for AdSTM, and a more extensive testing.

Label-free and portable field-effect sensor for monitoring RT-LAMP products to detect SARS-CoV-2 in wastewater

The COVID-19 pandemic caused by the coronavirus SARS-CoV-2 has proven the need for developing reliable and affordable technologies to detect pathogens. Particularly, the detecting the genome in wastewater could be an indicator of the transmission rate to alert on new outbreaks. However, wastewater-based epidemiology remains a technological challenge to develop affordable technologies for sensing pathogens. In this work, we introduce a label-free and portable field-effect transistor (FET)-based sensor to detect N and ORF1ab genes of the SARS-CoV-2 genome. Our sensor integrates the reverse transcription loop-mediated isothermal amplification (RT-LAMP) reaction as a cost-effective molecular detection exhibiting high specificity. The detection relies upon pH changes, due to the RT-LAMP reaction products, which are detected through a simple, but effective, extended-gate FET sensor (EGFET). We evaluate the proposed device by measuring real wastewater samples to detect the presence of SARS-CoV-2 genome, achieving a limit of detection of 0.31 × 10−3 ng/μL for end-point measurement. Moreover, we find the ability of the sensor to perform real-time-like analysis, showing that the RT-LAMP reaction provides a good response after 15 min for concentrations as low as 0.37 ng/μL. Hence, we show that our EGFET sensor offers a powerful tool to detect the presence of the SARS-CoV-2 genome with a naked-eye method, in a straightforward way than the conventional molecular methods for wastewater analysis.

Simple, rapid, portable and quantitative sensing of Fe3+ ions via analyte-triggered redox reactions mediating Tyndall effect enhancement of Au nanoparticles

This study initially describes a new nanosensing method for colorimetric detection of iron (III) (Fe3+) ions with high sensitivity and selectivity using one of the most basic optical properties of colloids (namely the Tyndall effect, TE). It adopts colloidal Au nanoparticles (AuNPs) prepared by sodium citrate reduction as the light scattering signaling probes, and 3,3′,5,5′ -tetramethylbenzidine (TMB) as recognition reagent. In the presence of Fe3+ ions, the TMB can be oxidized to its positively-charged product (TMBox) to induce the aggregation of the negatively-charged AuNP via electrostatic adsorption, leading to a significant enhancement in their TE which positively relies on the analyte concentration in the sample. The results demonstrate that this nanosensor is simple, rapid, low-cost, and portable, because it takes just 15 min to complete one assay run where only a laser pointer pen is utilized as the hand-held light source to stimulate the TE creation and a smartphone as the mobile quantitative TE reader. In particular, it can linearly detect the Fe3+ in a level range from 0.5 to 64 µM with a detection limit of ∼ 370 nM, offering a ∼ 37-fold improvement in sensitivity but with ∼ 9 times reduction in nanoprobe consumption per assay in comparison with the most common AuNP-based naked-eye method with surface plasmon resonance signaling strategy. Its accuracy and practicability are additionally validated by determining Fe3+ ions in real complex samples including tap water, commercially-available drinking water and human serum with acceptable recovery results between 85.96 and 115.52%. To the best of our knowledge, this is the first report of designing an equipment-free quantitative visual assay for the Fe3+ analysis by taking the advantage of the TE of colloids like AuNP tested herein.

Minimisation of variations in locating an acupuncture point using a laser-device

BackgroundIdentifying accurate acupoint is an essential component in clinical practice. A laser device can provide us with a visual guide for locating acupoints by dividing the space equally between two landmarks on the body. In this study, we compared the accuracy between the naked-eye and a laser device to locate an acupoint. MethodsTwenty-two participants were asked to mark acupoint PC5 on a male volunteer’s arm using two different methods: without a laser device (naked-eye) and with a laser device. The distributions of the acupoints were estimated by the kernel density estimation methods. ResultsThe overall distribution of acupoints was less when the laser device method was used, compared to the naked-eye method. We found significant differences in the longitudinal axis between the two methods, but no significant differences in the horizontal axis. ConclusionsOur findings suggest that direct measurement of the acupoint location using a laser device can reduce variations in locating points. Laser-assisted tools will help practitioners locate the acupoints more accurately and should be considered as standard practice, especially in acupuncture research and education.

A simple and rapid method for determination of paraquat in human urine and plasma by improved solid adsorption using equipment built in-house

A simple and rapid method was developed for clinical naked-eye and quantitative detection of paraquat (PQ) in human plasma and urine samples using built-in-house analytical devices followed by visual colorimetric method and UV–Vis spectrophotometry. A quantitative spectrophotometric method for PQ was also developed based on device built in-house. Different factors influencing the recovery efficiency of PQ such as the pH of the sample solution, the amount of adsorbent, the type and volume of eluent, the extraction and desorption time, the adsorption capacity and sample volume were studied and optimized in detail. Under optimal conditions, the whole analysis time of the naked-eye method was less than 5 min and it provided the detection limit observed with naked eye of 0.2 μg/mL with the detection range between 0.5 and 5.0 μg/mL for paraquat determination. PQ could be detected as low as 6.21 × 10−3 μg/mL in urine and 0.119 μg/mL in plasma with this proposed quantitative spectrophotometric method, respectively. The method was applied in monitoring PQ levels in plasma and urine at different hemoperfusion numbers in local hospitals for patients exposed to PQ poisoning. The detection result could not only enable immediate medical intervention but also benefit patients’ survival.

Indicator Layers Based on Ethylene-Vinyl Acetate Copolymer (EVA) and Dicyanovinyl Azobenzene Dyes for Fast and Selective Evaluation of Vaporous Biogenic Amines.

The article presents naked-eye methods for fast, sensitive, and selective detection of isopentylamine and cadaverine vapours based on 4-N,N-dioctylamino-4′-dicyanovinylazobenzene (CR-528) and 4-N,N-dioctylamino-2′-nitro-4′-dicyanovinylazobenzene (CR-555) dyes immobilized in ethylene-vinyl acetate copolymer (EVA). The reaction of CR-528/EVA and CR-555/EVA indicator layers with isopentylamine vapours caused a vivid colour change from pink/purple to yellow/orange-yellow. Additionally, CR-555/EVA showed colour changes upon exposure to cadaverine. The colour changes were analysed by ultraviolet–visible (UV/VIS) molecular absorption spectroscopy for amine quantification, and the method was partially validated for the detection limit, sensitivity, and linear concentration range. The lowest detection limits were reached with CR-555/EVA indicator layers (0.41 ppm for isopentylamine and 1.80 ppm for cadaverine). The indicator layers based on EVA and dicyanovinyl azobenzene dyes complement the existing library of colorimetric probes for the detection of biogenic amines and show great potential for food quality control.

Real-time video-assisted retrieval of airway foreign body in very young pediatric patients.

ObjectivesAdvancements in medical endoscopy and techniques of rigid bronchoscopy for foreign body removal have enabled higher diagnostic accuracy, reduced morbidity and precise manipulation. However, in pediatric patients, endoscope-combined forceps may be too big to fit into the small sized airway. Here we present our method of endoscope assisted rigid bronchoscopy in pediatric patients and compare the clinical benefits with conventional naked-eye rigid bronchoscopy.MethodsWe used a 2.7 mm, 0° straight endoscope and small caliber grasping forceps with 3.0 to 4.5 mm sized rigid bronchoscopy for very young (<3 years of age) patients of foreign body aspiration. As an assistant held the rigid bronchoscope in situ, the operator could manipulate the endoscope and forceps bimanually. With endoscopic guidance, the foreign body retrieval was performed carefully. The clinical advantages were compared between our endoscope-assisted method (n=29) and the conventional bronchoscopy method (n=33) in terms of operation time and recovery (hospital stay).ResultsBimanual endoscope-assisted rigid bronchoscopy method was technically feasible and safe. The operation time was less, compared to the conventional technique and the patients recovered more quickly. In all cases, our method completely removed the foreign body without need of a second bronchoscopy procedure.ConclusionBimanual endoscope-assisted retrieval of airway foreign body in very young age pediatric patients was superior to the conventional naked-eye method concerning accurate manipulation and safety.

Cryotherapy precision. Clinician's estimate of cryosurgical iceball lateral spread of freeze

To examine physicians' ability to estimate the lateral spread of freeze (LSF) of a cryosurgical iceball using three techniques. A nonrandomized control trial of in vitro nitrous oxide cryosurgical procedures. Primary care residency training programs. A convenience sample of 80 resident and faculty physicians from four family practice residency programs and one obstetrics and gynecology residency program. After performing cryosurgery with standard naked-eye and colposcopic-assisted techniques, subjects used a new experimental cryosurgical iceball gauge (CIG) to estimate the LSF during cryotherapy. LSF estimations reported physicians were compared simultaneously with those measured by an observer. The mean (+/- SD) LSF estimation errors at the termination of freeze were as follows: 2.62 +/- 2.42 mm for the colposcopy technique, 2.00 +/- 2.16 mm for the naked-eye method, and 1.28 +/- 0.87 mm for the CIG technique. The range of maximum error was 6.5 to 11 mm for the colposcopic technique, 5.5 to 12.5 mm for the naked-eye method, and 3.0 to 4.0 mm for the CIG technique. Overestimation of the LSF, which increases the risk of undertreatment and residual disease, was more common than underestimation. The CIG minimized perceptual error and provided the best cryosurgical precision.

A chromosome anomaly in an infant with a degenerative disease of the central nervous system

A presumably balanced reciprocal translocation involving 2 chromosomes of Group E (16–18) has been observed in an infant with a degenerative disease of the central nervous system. Human translocation involving 2 members of Group E has not previously been observed. It is generally stated that balanced reciprocal translocations produce no detectable phenotypic effect since there is no loss of genetic material. However, the naked-eye method of karyotype analysis may fail to detect the loss of small amounts of genetic material. Whether the relationship between the abnormal karyotype and the clinical disorder in this case is causal or fortuitous remains to be determined.

PLAGUE AMONG RATS IN SAN FRANCISCO.

The following notes on epizootic plague in rats are published in the belief that they may prove of interest to other workers. It will be observed that the relative merits of the microscopic and naked-eye methods of detecting plague in rats have been thoroughly tested. Our data are drawn from the microscopic and anatomic appearances of 14,184 rodents examined between Sept. 13, 1907, and Jan. 14, 1908. We agree with the last Indian Commission¹in their belief that the naked-eye method alone furnishes enough data to pass on a rat as being plague infected or not. Like them, however, we preferred to combine the two methods first in order to rule out any fallacies which might be introduced by unknown local conditions. So far no disease of rats has been encountered which could possibly cause confusion, with the exception of a few instances which will be cited below under