Disposable electrochromic polyaniline sensor based on a redox response using a conventional camera: A first approach to handheld analysis

We present a disposable optical sensor for Ascorbic Acid (AA). It uses a polyaniline based electrochromic sensing film that undergoes a color change when exposed to solutions of ascorbic acid at pH 3.0. The color is monitored by a conventional digital camera working with the hue (H) color coordinate. The electrochromic film was deposited on an Indium Tin Oxide (ITO) electrode by cyclic voltammetry and then characterized by atomic force microscopy, electrochemical and spectroscopic techniques. An estimation of the initial rate of H, as ΔH/Δt, is used as the analytical parameter and resulted in the following logarithmic relationship: ΔH/Δt = 0.029 log[AA] + 0.14, with a limit of detection of 17 μM. The relative standard deviation when using the same membrane 5 times was 7.4% for the blank, and 2.6% (for n = 3) on exposure to ascorbic acid in 160 μM concentration. The sensor is disposable and its applicability to pharmaceutical analysis was demonstrated. This configuration can be extended for future handheld configurations.We acknowledge financial support from the Junta de Andalucía (Proyecto de Excelencia P10-FQM-5974) and from the Ministerio de Economía y Competitividad (CTQ2013-44545-R). These projects were partially supported by European Regional Development Funds (ERDF)

Detection of Cartilage Oligomeric Matrix Protein Using a Quartz Crystal Microbalance

Current methods for diagnosing early stage osteoarthritis (OA) based on the magnetic resonance imaging and enzyme-linked immunosorbent assay methods are specific, but require specialized laboratory facilities and highly trained personal to obtain a definitive result. In this work, a user friendly and non-invasive quartz crystal microbalance (QCM) immunosensor method has been developed to detect Cartilage Oligomeric Matrix Protein (COMP) for early stage OA diagnosis. This QCM immunosensor was fabricated to immobilize COMP antibodies utilizing the self-assembled monolayer technique. The surface properties of the immunosensor were characterized by its FTIR and electrochemical impedance spectra (EIS). The feasibility study was based on urine samples obtained from 41 volunteers. Experiments were carried out in a flow system and the reproducibility of the electrodes was evaluated by the impedance measured by EIS. Its potential dynamically monitored the immunoreaction processes and could increase the efficiency and sensitivity of COMP detection in laboratory-cultured preparations and clinical samples. The frequency responses of the QCM immunosensor changed from 6 kHz when testing 50 ng/mL COMP concentration. The linear regression equation of frequency shift and COMP concentration was determined as: y = 0.0872 x + 1.2138 (R2 = 0.9957). The COMP in urine was also determined by both QCM and EIS for comparison. A highly sensitive, user friendly and cost effective analytical method for the early stage OA diagnosis has thus been successfully developed

Self-assembly and chiral recognition of quartz crystal microbalance chiral sensor

10.1002/chir.20756Chirality224411-415CHRL

Real-Time QCM Measurements of Rolling Circle Amplification Products

We demonstrate real-time experimental evidence for mass underestimation, to analyse high molecular weight biomolecules while using Quartz Crystal Microbalance (QCM) platform. For this, we present an experimental evidence with an assay consisting of an aptamer-antibody sandwich model with norovirus-like particles (NoVLPs). We combine this with the proximity ligation assay to generate bulky rolling circle products on a gold spot centralized quartz resonator surface. Real-time monitoring of the assay build-up reflects that bulky NoVLPs and amplified oligonucleotides generate fluctuating signals during measurement using a microfluidic QCM sensor. Such an understanding of mass underestimation for heavier molecules becomes indispensable to get deeper insights into molecular interactions in biotechnology studied using QCM devices