Computer Screen Photo-assisted Technique Research Articles

Compact System for Colorimetric Sensor Arrays Characterization Based on Computer Screen Photo-Assisted Technology

The detection of the spectral fingerprint of chemical sensors through the combined use of an LCD and a webcam is an alternative approach for chemical sensor characterization. This technique allows the development of more compact, cheap, and user-friendly measurement systems compared to the more classic instruments, such as spectrometers and gas chromatography systems. In the Computer Screen Photo-assisted Technique (CSPT), a display acts as a light source, and a conventional camera (e.g., a webcam) plays the role of a detector. The light from the LCD is reflected (or transmitted) by the chemical sensor, and the camera detects it. In the present contribution, we propose a compact and low-cost platform based on CSPT for the characterization of colorimetric sensor arrays. The system can provide spectral information of both reflected and transmitted light from the sample. Further, a 2.4-inch LCD and three different detector’s (a webcam, an RGB sensor, and a camera module) performances have been evaluated and discussed. The developed system includes a UDOO-based single board computer that makes it a stand-alone measurement system.

Two low-cost digital camera-based platforms for quantitative creatinine analysis in urine

In clinical analysis creatinine is a routine biomarker for the assessment of renal and muscular dysfunctions. Although several techniques have been proposed for a fast and accurate quantification of creatinine in human serum or urine, most of them require expensive or complex apparatus, advanced sample preparation or skilled operators. To circumvent these issues, we propose two home-made platforms based on a CD Spectroscope (CDS) and Computer Screen Photo-assisted Technique (CSPT) for the rapid assessment of creatinine level in human urine. Both systems display a linear range (r2 = 0.9967 and 0.9972, respectively) from 160 μmol L−1 to 1.6 mmol L−1 for standard creatinine solutions (n = 15) with respective detection limits of 89 μmol L−1 and 111 μmol L−1. Good repeatability was observed for intra-day (1.7–2.9%) and inter-day (3.6–6.5%) measurements evaluated on three consecutive days. The performance of CDS and CSPT was also validated in real human urine samples (n = 26) using capillary electrophoresis data as reference. Corresponding Partial Least-Squares (PLS) regression models provided for mean relative errors below 10% in creatinine quantification.

The Extended Receptive Field of Blends of Metalloporphyrins and pH Indicators

Molecular cooperation is a fascinating methodology to design functional materials. In chemical sensors, The sensitive unit can be formed by two interacting molecules whose interaction is altered by the adsorption of an analyte. This principle is conveniently exploited in the Indicator Displacement Assay (IDA) where the sensing unit is a colorimetric indicator bound to a colorless receptor. The interaction of the receptor with an analyte may than displace the dye giving rise to a detectable color change [1]. This technique has been demonstrated for instance for the colorimetric detection of sugars [2].This working principle can be extended preparing an assembly constituted of two chemoresponsive dyes, namely molecules that can change their spectrum as a consequence of the interaction with volatile compounds. AS an example of this apporahc we discuss the case of blends of a porphyrin and an acid-base indicator. Metalloporphyrins allow for the recognition of analytes with Lewis acid/base capabilities, while pH indicators respond to changes in the proton acidity or basicity of the surrounding environment. Molecules that possess none of these properties are not expected to be detected by these chemoresponsive dyes; but they can be optically detected by proper blends of dyes.Solid layers of blends can be spotted onto a transparent substrate to measure the light transmitted through the spote. The layer of spots can be coinveniently matched with a transduction technique known as Computer Screen Photoassisted Technique (CSPT). CSPT arrangement consists of a LCD screen that illuminates the sensing film and a computer camera that records pictures of it during the exposure to vapors of target analytes. Such arrangement was already demonstrated as a suitable system for VOCs classification or for food freshness evaluation [3].Different experiments aimed at evaluating the sensing capabilities of dye blends compared to those of single components were set up. Results indicate that for most part of the tested volatile compounds the variations of the absorbance spectrum of porphyrin-indicator blends exceed those of the single components.Noteworthy, for some of the compounds a response is found also when no color change is elicited in the membrane based on pure indicators.This is the most interesting characteristic of porphyrin-pH indicator blends as it overcomes the indicator failure in detecting certain chemical species through an optical transduction setup. The blends with different dye ratios show peculiar responses to the volatile compounds. In general the composition with a weight ratio 1:1 guarantees the best performance in terms of intensity response towards the largest number of compounds. Since the molar mass of the two components is similar, this is in agreement with the observation that the binding is established between single molecules.The sensitivity of porphyrins-pH indicator blends was tested with alcohols, amines, ketones, alcohols, ethers, aldehydes. Principal component analysis of the array data shows the effective recognition of different compounds.The blends with different dye ratios show peculiar responses to the volatile compounds. In general the composition with a weight ratio 1:1 guarantees the best performance in terms of intensity response towards the largest number of compounds. Since the molar mass of the two components is similar, this is in agreement with the observation that the binding is established between single molecules.The sensitivity of porphyrins-pH indicator blends was tested with alcohols, amines, ketones, alcohols, ethers, aldehydes. Principal component analysis of the array data shows the effective recognition of different compounds.

Multimodal Use of New Coumarin‐Based Fluorescent Chemosensors: Towards Highly Selective Optical Sensors for Hg2+ Probing

Despite several types of fluorescent sensing molecules have been proposed and examined to signal Hg(2+) ion binding, the development of fluorescence-based devices for in-field Hg(2+) detection and screening in environmental and industrial samples is still a challenging task. Herein, we report the synthesis and characterization of three new coumarin-based fluorescent chemosensors featuring mixed thia/aza macrocyclic framework as receptors units, that is, ligands L1-L3. These probes revealed an OFF-ON selective response to the presence of Hg(2+) ions in MeCN/H2 O 4:1 (v/v), which allowed imaging of this metal ion in Cos-7 cells in vitro. Once included in silica core-polyethylene glycol (PEG) shell nanoparticles or supported on polyvinyl chloride (PVC)-based polymeric membranes, ligands L1-L3 can also selectively sense Hg(2+) ions in pure water. In particular we have developed an optical sensing array tacking advantage of the fluorescent properties of ligand L3 and based on the computer screen photo assisted technique (CSPT). In the device ligand L3 is dispersed into PVC membranes and it quantitatively responds to Hg(2+) ions in natural water samples.

Fluorimetric Chemosensors Combined with Familiar CSPT Devices for the Selective Detection of Mercury(II) Ions

Abstract Fluorimetric and Computer Screen Photoassisted Technique (CSPT) studies on the binding properties of three coumarin pendant arm derivatives of mixed aza-thioether macrocyclic ligands (L1-L3), incorporated into PVC plasticized polymeric membranes, towards a number of different metal cations were carried out. An enhanced selectivity of the ligands towards Hg2+ion was detected. In particular, the DOS plasticized membrane containing L3 and tetrakis(p-chlorophenyl)borate, TpClPB-, as lipophilic anionic additive, displayed a strong fluorescence activation by Hg2+over the wide concentration range of 10-7to 10-3M. The influence of the ratio among ligand and lipophilic additive on the membrane performance was tested. In addition, the CSPT measurements showed that L3 possesses a unique selectivity towards Hg2+ion with respect to several common diverse cations. Moreover CSPT technique permits to perform the fast and low cost monitoring of mercury (II) ions, by application of familiar devices and a chemometric approach.

The hyphenated CSPT-potentiometric analytical system: An application for vegetable oil quality control

The computer screen photo assisted technique (CSPT) has been used to develop a hyphenated optical-potentiometric sensing array, based on porphyrinoid materials dispersed into PVC membranes. Sensing layers have been deposited onto indium tin oxide (ITO) glass slides, which were exploited as electrodes, for potentiometric measurements, and chromophore spots, to obtain CSPT data. Both measurements were contemporaneously carried out in the hyphenated sensing platform. The performances of the hyphenated sensing array were first tested for the detection of model analytes, characteristics of vegetable oil matrices, and then evaluated in the discrimination of real samples of olive and seed oils. The results obtained demonstrated that the hyphenated system affords a significant improvement of information and oils classification with respect to the individual potentiometric and optical components.

Spectral fingerprinting of porphyrins for distributed chemical sensing

Recent progress in spectral fingerprinting of fluorescent indicators using distributed instrumentation based on consumer electronic devices is reviewed. In particular, the evaluation of disposable assays using a computer screen photo-assisted technique (CSPT) is discussed. Sample identification and optimization strategies are analyzed as well as the underlying theoretical background for polychromatic spectral fingerprinting.

Towards integrated devices for computer screen photo-assisted multi-parameter sensing

The computer screen photo-assisted technique (CSPT) utilizes consumer electronic devices such as computer screens and web cameras for distributed chemical sensing. Key to this method is the development of small and disposable sensing assays able to aid the CSPT optical detection, and the evaluation of multiple indicators. Here we demonstrate CSPT identification of fluorescent indicators from individual 100 μm SU-8 (10) pillars covering an area of 4 mm × 4 mm with a density of 47 elements mm −2. The extraction of distinctive spectral fingerprints is aided by the exploitation of a three-band Moiré interference that enables the partial Bayer decoding of the CSPT images.

Automatic optimization of experimental conditions for fast evaluation of diagnostic tests using ubiquitous instrumentation

Abstract Rapid quantitative determinations of creatinine, potassium and glucose, all important parameters in routine medical diagnostics, are demonstrated using a computer screen photo-assisted technique (CSPT). CSPT uses regular computer screens as light sources and web cameras as imaging detectors for supporting optical evaluations of diverse character. The ubiquity and versatility of the setup, makes CSPT an attractive candidate for point of care determinations. A robust procedure for the automatic selection of experimental conditions in CSPT evaluation, including camera channels and illuminating colors that minimize the measuring time up to 5 times is described. The method utilizes the correlation between experimental conditions and classification scores, obtained under a generic 50 color training session, to extract measuring sequences as short as 9 s. The extracted measuring conditions automatically adapted to the different tests provided a general, practical and fast approach for CSPT optimization in real scenarios.

Insights on the chemistry of a,c-biladienes from a CSPT investigation

Computer Screen Photoassisted Technique (CSPT) is a recent interesting approach for the development of optical sensor platforms using ubiquitous devices. We demonstrate here that the information obtained by CSPT measurements can be useful for other than sensing purposes and a computer set and a web camera can also be exploited as spectroscopic technique for the characterization of the compounds used as indicators. CSPT measurement data have been used to characterize novel features of the a,c-biladiene chemistry, which have been later confirmed by photophysical characterization carried out using classical instrumentation. The demonstrated analytical capabilities of a regular computer–web camera set reach a degree of complexity approaching that of fluorescence excitation-emission spectroscopy, something remarkable considering the exploitation of familiar and already well distributed devices.

Direct quantitative evaluation of complex substances using computer screen photo-assisted technology: The case of red wine

The combination of computer monitors and webcams has been recently demonstrated to behave as a sort of spectrophotometer able to classify and recognize substances according to their light absorption and emission properties. This measurement technique is known as computer screen photoassisted technique (CSPT). In this paper, it is demonstrated for the first time and in the case of a complex sample such as red wine, that also quantification of integral parameters (colour indicators) and specific compounds (total anthocyanins and polyphenols) is possible through a multivariate analysis of CSPT fingerprints. Most of the properties of the method are due to the combination of light emission and absorption properties that are captured by the CSPT platform. Thanks to this combination, a CSPT fingerprint may contain a comparable amount of information with respect to standard spectrophotometers. Wine measurements were performed on intact samples without the intervention of chemical mediators. The regression models, built by Partial Least Squares, obtained errors of estimation of colour parameters, total polyphenols and anthocyanines that are comparable with those typical of the standard methods in use. Since computation functionalities, video capture and display are embedded in a steadily growing number of ubiquitously distributed equipments (from portable computers to cellular phones), these results indicate a viable methodology for low-cost and largely diffused analytical capabilities.

Computer screen photo-assisted techniques for global monitoring of environmental and sanitary parameters

The computer screen photo-assisted technique (CSPT) is a measuring method that uses regular computer screens as controlled light sources and web cameras as imaging detectors for optical evaluations of sensing substances, which optical properties respond to target analytes. The fact, that CSPT uses a globally distributed and familiar infrastructure as instrumentation and that is able to serve multiple targets with the same setup, makes it an attractive candidate for home testing. This article reviews the CSPT concept and focuses in two recent studies that demonstrate thorough CSPT determinations using a handy and eventually disposable assay format, with the potential to be as ubiquitous as the CSPT platforms themselves. The implications of such combination of technologies is discussed, and its potential to support the global monitoring of environmental and sanitary parameters, using Internet geography browsers, is analyzed.

Spectral characteristics of computer screen photoassisted classification

The computer screen photoassisted technique (CSPT) is a practical method for the classification of colored or fluorescent substances such as those present in bioassays but using standard computer sets and regular web cameras as all instruments. It is empirically known that the performance of the CSPT classification depends on the composition of the illuminating sequences displayed by the computer screens during the measurements, and by the way that substance fingerprints from these measurements are composed. Here the illuminating conditions are examined with the help of a CSPT model that allows to examine the physical grounds of optimum illuminating sequences different from just three screen primaries and to assess the limitations and importance of longer illuminating sequences in practical determinations.

Background compensation in computer screen photo-assisted reflectance fingerprinting

The computer screen photo-assisted technique (CSPT) is a method for the classification of colorimetric assays utilizing ordinary computer sets and web cameras as instrumentation. In CSPT measurements the web camera captures the image of the assay under the screen illumination, and typically a spurious spatial distribution of intensities is overlapped on the image. This issue is examined here, focusing on the effect of the sample and illuminating colors on the spatial modulation of intensity. A method for the selection of colors composing an illuminating sequence that minimizes the spatial variability is proposed. The approach is tested for the classification of different color substances showing improvements up to 53% of the intra/inter cluster distance ratio measured in a PCA space, when compared to randomly chosen colors.

Measurement strategy and instrumental performance of a computer screen photo-assisted technique for the evaluation of a multi-parameter colorimetric test strip

A measuring strategy for the evaluation of a seven parameters colorimetric test using a computer screen photo-assisted technique (CSPT) is demonstrated. CSPT is a versatile approach aimed at point of care or home tests that uses regular computer sets and web cameras as the whole instrument. Issues such as the stability and the equivalency on different platforms of the determinations have been addressed in the present work. The method uses an embedded local reference simultaneously measured with the tests and solves the evaluation as a classification problem. The achieved performance tested along 580 classifications covering all the ranges of the assay, using synthetic samples, yielded 97.2% correct determinations compared with 89.7% for the case of colorimetric determinations. The errors were concentrated in only two parameters that show a significant correlation with a set of quality indices used to assess the performance of the classification.

Effect of fingerprint conformation and spectral scaling on the performance of computer screen photo-assisted experiments

The use of computer screens as controlled light sources and web cameras as image detectors (the so-called computer screen photo-assisted technique, CSPT) is an ubiquitous alternative for the evaluation of colorimetric quick tests at homes or in primary care units. The performance of CSPT for such evaluations depends on several factors, from which the most relevant are the composition of illuminating sequences and the conformation of CSPT substance signatures. In this work, with the aid of a CSPT model, the effect of the construction of the substance signatures on the classification performance of different representative substance sets is studied. The correlation of illuminating colors with such classification is investigated, allowing one to determine redundancy and limitations with respect to visible spectroscopy. The concept of spectral scaling is introduced and its properties compared with standard procedures.

Preferential color substances and optimized illuminations for computer screen photo-assisted classification

The computer screen photo-assisted technique (CSPT) is a practical method aimed at the evaluation of colorimetric assays using regular computer sets and web cameras as only instruments. The performance of CSPT, understood as its ability to distinguish different color substances, depends of the color of the evaluated substances and on the particular illuminating sequences used for the measurements. In this work, the systematic study of the CSPT performance for sets of 2 and 5 similar color substances is accomplished with the aid of a CSPT model. The result allows identifying specific substance transmittances most favorable with the classification capability of the technique, which is relevant for the design of assays customized for CSPT. The optimization of three colors short illuminating sequences (implying fast measurements) for specific sets of substances is demonstrated and compared with the performance for white illumination. The resulting average improvement in the performance, quantified as the Euclidean distance in a principal components space, for sets of 2 and 5 substances approximately doubles the result with white illumination, and presents performance peaks more than five times larger for critical substance sets.

Computer screen photo-assisted detection of complementary DNA strands using a luminescent zwitterionic polythiophene derivative

The computer screen photo-assisted technique (CSPT), a practical method for the evaluation of assays using computer screens as light sources and web cameras as detectors, has been used to detect the attachment of complementary DNA strands (20-mer, 5′-CAT GAT TGA ACC ATC CAC CA-3′) to a complex of single DNA strands and a polythiophene derivative (poly(3-[( S)-5-amino-5-carboxyl-3-oxapentyl]-2,5-thiophenylene hydrochloride (POWT)). The complex is a highly sequence specific indicator, based on non-covalent coupling of DNA to a water-soluble, zwitterionic, electroactive and photoactive polymer able to produce a combined absorption-emission signal readable by CSPT. The observed CSPT signal retains key spectral features of the complex spectrum, distinguishing the DNA attachment, as well as other stimuli, such as pH regulation at concentrations of 30 μM POWT and 15 μM DNA. A CSPT time resolved (linked to temperatures between 8 and 18 °C) approach is demonstrated as a complementary source of discrimination and for testing the robustness of the achieved classification.

Enhancing classification capabilities of computer screen photo-assisted fluorescence fingerprinting

The separation of emission from transmitted light for the fingerprinting of fluorescent substances using a computer screen photo-assisted technique (CSPT) is demonstrated. CSPT is a technique for optical evaluation using a simple cell with just a standard computer set and a web camera as instrumentation. It has been demonstrated to be a versatile system for colorimetric and fluorescent fingerprinting. Here the omnidirectional property of fluorescent emission is utilized to separate it from the background, using a simple optical arrangement compatible with CSPT purposes. This enhances the classification capabilities and makes classification at sub-μM concentrations possible.

Adaptive illumination in computer screen assisted spectral fingerprinting

The computer screen photoassisted technique (CSPT) uses displays as controlled light sources for measuring spectral fingerprints of color substances, such as those present in bioassays. Here, the possibility of tuning the illuminating sequences for matching CSPT fingerprints with target spectral transmittances is demonstrated. This approach enables robust classification; orders of magnitude form mismatches, and establish a systematic method for adapting optimum illuminating sequences to any unknown measuring platform.