Broadly Available Imaging Devices Enable High-Quality Low-Cost Photometry

This paper demonstrates that, for applications in resource-limited environments, expensive microplate spectrophotometers that are used in many central laboratories for parallel measurement of absorbance of samples can be replaced by photometers based on inexpensive and ubiquitous, consumer electronic devices (e.g., scanners and cell-phone cameras). Two devices, (i) a flatbed scanner operating in transmittance mode and (ii) a camera-based photometer (constructed from a cell phone camera, a planar light source, and a cardboard box), demonstrate the concept. These devices illuminate samples in microtiter plates from one side and use the RGB-based imaging sensors of the scanner/camera to measure the light transmitted to the other side. The broadband absorbance of samples (RGB-resolved absorbance) can be calculated using the RGB color values of only three pixels per microwell. Rigorous theoretical analysis establishes a well-defined relationship between the absorbance spectrum of a sample and its corresponding RGB-resolved absorbance. The linearity and precision of measurements performed with these low-cost photometers on different dyes, which absorb across the range of the visible spectrum, and chromogenic products of assays (e.g., enzymatic, ELISA) demonstrate that these low-cost photometers can be used reliably in a broad range of chemical and biochemical analyses. The ability to perform accurate measurements of absorbance on liquid samples, in parallel and at low cost, would enable testing, typically reserved for well-equipped clinics and laboratories, to be performed in circumstances where resources and expertise are limited.Chemistry and Chemical Biolog

Polymerization-based signal amplification for paper-based immunoassays

Diagnostic tests in resource-limited settings require technologies that are affordable and easy to use with minimal infrastructure. Colorimetric detection methods that produce results that are readable by eye, without reliance on specialized and expensive equipment, have great utility in these settings. We report a colorimetric method that integrates a paper-based immunoassay with a rapid, visible-light-induced polymerization to provide high visual contrast between a positive and a negative result. Using Plasmodium falciparum histidine-rich protein 2 as an example, we demonstrate that this method allows visual detection of proteins in complex matrices such as human serum and provides quantitative information regarding analyte levels when combined with cellphone-based imaging. It also allows the user to decouple the capture of analyte from signal amplification and visualization steps.Bill & Melinda Gates Foundation (Award 51308)United States. Defense Advanced Research Projects Agency (HR0011-12-2-0010)National Science Foundation (U.S.). Graduate Research FellowshipBurroughs Wellcome Fund (Career Award at the Scientific Interface

Adaptive Use of Bubble Wrap for Storing Liquid Samples and Performing Analytical Assays

This paper demonstrates that the gas-filled compartments in the packing material commonly called “bubble wrap” can be repurposed in resource-limited regions as containers to store liquid samples, and to perform bioanalyses. The bubbles of bubble wrap are easily filled by injecting the samples into them using a syringe with a needle or a pipet tip, and then sealing the hole with nail hardener. The bubbles are transparent in the visible range of the spectrum, and can be used as “cuvettes” for absorbance and fluorescence measurements. The interiors of these bubbles are sterile and allow storage of samples without the need for expensive sterilization equipment. The bubbles are also permeable to gases, and can be used to culture and store micro-organisms. By incorporating carbon electrodes, these bubbles can be used as electrochemical cells. This paper demonstrates the capabilities of the bubbles by culturing E. coli, growing C. elegans, measuring glucose and hemoglobin spectrophotometrically, and measuring ferrocyanide electrochemically, all within the bubbles.Chemistry and Chemical BiologyOther Research Uni

Electrically Activated Paper Actuators

This paper describes the design and fabrication of electrically controlled paper actuators that operate based on the dimensional changes that occur in paper when the moisture absorbed on the surface of the cellulose fibers changes. These actuators are called “Hygroexpansive Electrothermal Paper Actuators” (HEPAs). The actuators are made from paper, conducting polymer, and adhesive tape. They are lightweight, inexpensive, and can be fabricated using simple printing techniques. The central element of the HEPAs is a porous conducting path (used to provide electrothermal heating) that changes the moisture content of the paper and causes actuation. This conducting path is made by embedding a conducting polymer (PEDOT:PSS) within the paper, and thus making a paper/polymer composite that retains the porosity and hydrophilicity of paper. Different types of HEPAs (straight, precurved, and creased) achieved different types of motions (e.g., bending motion, accordion type motion). A theoretical model for their behavior is proposed. These actuators have been used for the manipulation of liquids and for the fabrication of an optical shutter.Chemistry and Chemical Biolog

Folding Analytical Devices for Electrochemical ELISA in Hydrophobic R H Paper

This work describes a device for electrochemical enzyme-linked immunosorbent assay (ELISA) designed for low-resource settings and diagnostics at the point of care. The device is fabricated entirely in hydrophobic paper, produced by silanization of paper with decyl trichlorosilane, and comprises two zones separated by a central crease: an embossed microwell, on the surface of which the antigen or antibody immobilization and recognition events occur, and a detection zone where the electrodes are printed. The two zones are brought in contact by folding the device along this central crease; the analytical signal is recorded from the folded configuration. Two proof-of-concept applications, an electrochemical direct ELISA for the detection of rabbit IgG as a model antigen in buffer and an electrochemical sandwich ELISA for the detection of malarial histidine-rich protein from Plasmodium falciparum (Pf HRP2) in spiked human serum, show the versatility of this device. The limit of detection of the electrochemical sandwich ELISA for the quantification of Pf HRP2 in spiked human serum was 4 ng mL–1 (102 pmol L–1), a value within the range of clinically relevant concentrations.Chemistry and Chemical Biolog

Fabrication of Paper-Templated Structures of Noble Metals

This manuscript describes a simple and rapid method for fabricating freestanding structures composed primarily (>94% w/w, and 55–80 at%) of noble metals (e.g., gold, silver, platinum, etc.) and having physical morphologies that resemble paper, thread, or fabric. In this method, templates (i.e., pieces of paper, or cotton fabric) are loaded with aqueous solutions of salts of noble metals, and then the cellulosic component is burned off in a furnace held at high temperatures (i.e., from 550 °C to 800 °C, depending on the procedure, in air). Even though the environment in a furnace is ostensibly oxidizing (e.g., hot air), the metal ions are reduced to elemental metal and form paper-template or fabric-templated structures that have morphologies similar to that of the material from which they were derived (i.e., paper or fabric). Paper template structures are fibrous, permeable to gases and liquids, electrically conductive, and in some cases (e.g., paper templated gold and paper template platinum structures), their surfaces are electroactive. The surface areas of paper-templated structures are more than 20 times higher than their projected areas. Paper-templated structures thus have properties that make them potentially useful in catalysis, sensing, and electroanalysis.Chemistry and Chemical Biolog

Comparative study of the AT1 receptor prodrug antagonist candesartan cilexetil with other sartans on the interactions with membrane bilayers

AbstractDrug–membrane interactions of the candesartan cilexetil (TCV-116) have been studied on molecular basis by applying various complementary biophysical techniques namely differential scanning calorimetry (DSC), Raman spectroscopy, small and wide angle X-ray scattering (SAXS and WAXS), solution 1H and 13C nuclear magnetic resonance (NMR) and solid state 13C and 31P (NMR) spectroscopies. In addition, 31P cross polarization (CP) NMR broadline fitting methodology in combination with ab initio computations has been applied. Finally molecular dynamics (MD) was applied to find the low energy conformation and position of candesartan cilexetil in the bilayers. Thus, the experimental results complemented with in silico MD results provided information on the localization, orientation, and dynamic properties of TCV-116 in the lipidic environment. The effects of this prodrug have been compared with other AT1 receptor antagonists hitherto studied. The prodrug TCV-116 as other sartans has been found to be accommodated in the polar/apolar interface of the bilayer. In particular, it anchors in the mesophase region of the lipid bilayers with the tetrazole group oriented toward the polar headgroup spanning from water interface toward the mesophase and upper segment of the hydrophobic region. In spite of their localization identity, their thermal and dynamic effects are distinct pointing out that each sartan has its own fingerprint of action in the membrane bilayer, which is determined by the parameters derived from the above mentioned biophysical techniques

Investigation of antioxidant properties of oils by using analytical spectrochemical techniques

This thesis deals with the development and validation of spectrophotometric analytical methods for the determination of the antioxidant properties of edible oils. Edible oils and especially olive oils are known for their strong antioxidant properties. A number of assays for the evaluation of the antioxidant activity of edible oils have been published but most of them refer to the hydrophilic extracts of the oils. There are only few assays, which study the antioxidant properties of total oil, mainly by using stability tests. This is due to the difficulty in finding the appropriate solvent, which dissolves both oil and the reagents, used in the method, without formation of turbid solutions.In this work, the following nine spectrophotometric analytical methods, able to estimate the antioxidant properties of edible oils, have been developed and validated: (a) a modified DPPH method, (b) a modified ABTS method, (c) a modified CUPRAC method, (d) a modified Fe-phenanthroline method, (e) a chemiluminogenic flow method (FIA-CL) based on chemiluminogenic reaction of lucigenin with alkaline hydrogen peroxide solution, (f) a fluorimetric method based on N-methylacridone produced from the reaction of lucigenin with alkaline hydrogen peroxide solution, (g) a chemiluminogenic flow method (FIA-CL) based on the reaction of luminol with alkaline hydrogen peroxide solution and (h) two chemiluminogenic methods based on the reaction of peroxy−oxalates with hydrogen peroxide. The developed assays have been applied to the evaluation of antioxidant activity of standard compounds and to the evaluation of total antioxidant activity of several edible oils as well as their lipophilic and hydrophilic extracts. The obtained results were compared and discussed.Η διατριβή αυτή ασχολείται με την ανάπτυξη και επικύρωση φασματοχημικών αναλυτικών μεθόδων εκτίμησης των αντιοξειδωτικών ιδιοτήτων εδώδιμων ελαίων. Τα έλαια και ιδιαιτέρως τα ελαιόλαδα είναι γνωστό ότι εμφανίζουν ισχυρές αντιοξειδωτικές ιδιότητες. Όλες οι μέθοδοι που αναφέρονται στη βιβλιογραφία εκτιμούν την αντιοξειδωτική ικανότητα υδρόφιλων εκχυλισμάτων ελαίων. Σπάνιες είναι οι αναφορές για μεθόδους εκτίμησης της ολικής αντιοξειδωτικής ικανότητας των ελαίων ή των λιπόφιλων εκχυλισμάτων αυτών και οι αναφορές αυτές είναι κυρίως πειράματα οξειδωτικής σταθερότητας με έμμεσο και εμπειρικό υπολογισμό της αντιοξειδωτικής ικανότητας. Κύρια αιτία για την έλλειψη μεθόδων προσδιορισμού της ολικής αντιοξειδωτικής ικανότητας εδώδιμων ελαίων είναι η δυσκολία εύρεσης κατάλληλου διαλύτη που να διαλυτοποιεί το έλαιο αλλά και τα αντιδραστήρια που χρησιμοποιούνται στη μέθοδο χωρίς να σχηματίζονται κολλοειδή διαλύματα.Στα πλαίσια αυτής της εργασίας αναπτυχθήκαν και επικυρώθηκαν οι παρακάτω εννέα αναλυτικές φασματοχημικές μέθοδοι εκτίμησης των αντιοξειδωτικών ιδιοτήτων ελαίων: (α) μια τροποποιημένη μέθοδος DPPH, (β) μια τροποποιημένη μέθοδος ABTS, (γ) μια τροποποιημένη μέθοδος CUPRAC, (δ) μια τροποποιημένη μέθοδος Fe-φαινανθρολίνης, ε) μια χημειοφωταυγειομετρική μέθοδος συνεχούς ροής (FIA-CL) βασισμένη στη χημειοφωταυγειομετρική αντίδραση της λουσιγενίνης με αλκαλικό διάλυμα υπεροξειδίου του υδρογόνου, στ) μια φθορισμομετρική μέθοδος βασισμένη στην εκπομπή φθορισμού της Ν-μεθυλοακριδόνης που παράγεται από την αντίδραση της λουσιγενίνης με αλκαλικό διάλυμα υπεροξειδίου του υδρογόνου, ζ) μια χημειοφωταυγειομετρική μέθοδος συνεχούς ροής (FIA-CL) βασισμένη στη αντίδραση της λουμινόλης με αλκαλικό διάλυμα υπεροξειδίου του υδρογόνου, και η) δύο χημειοφωταυγειομετρικές μεθόδους βασισμένες στην αντίδραση των οξαλικών εστέρων με το υπεροξείδιο του υδρογόνου. Οι μέθοδοι που αναπτύχθηκαν χρησιμοποιήθηκαν για την εκτίμηση της αντιοξειδωτικής ικανότητας προτύπων ουσιών και εδώδιμων ελαίων καθώς και στην εκτίμηση της αντιοξειδωτικής ικανότητας του λιπόφιλου και υδρόφιλου τμήματος αυτών. Τα αποτελέσματα που ελήφθησαν συγκρίθηκαν και σχολιάστηκαν