Piezoelectric biosensors

Authors:  Petr Skládal

Department of Biochemistry, Faculty of Science, Masaryk University, Brno, Czech Republic

Journal: Trends in Analytical Chemistry

Abstract: Progress in the field of piezoelectric (quartz crystal microbalance-based) biosensors in the recent five years is reviewed. In addition to the traditional immunosensing assays, the combination with detection of nucleic acids is addressed, biosensing of microbes and novel applications in the field of cellular biology are highlighted. The signal enhancing strategies based on both biochemical cascades (often involving nanoparticles) and technological improvements of instrumentation are discussed.

Keywords: Quartz crystal microbalance, Immunosensor, Nucleic acid sensor, Eukaryotic cellular studies, Instrumentation for piezosensors

Electro-Assisted Deposition of Calcium Phosphate on Self-Assembled Monolayers

Authors: Noah Metoki1, Kazi Sadman2, Kenneth Shull2, Noam Eliaz1 and Daniel Mandler3

1Biomaterials and Corrosion Lab, Department of Materials Science and Engineering, Tel-Aviv University, Ramat Aviv 6997801, Israel
2Polymer Surfaces & Inferfaces Lab, Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA
3Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel

Journal: Electrochimica Acta (2016)

Abstract: Calcium phosphate (CaP) ceramics are used in orthopedics and dentistry due to their excellent biocompatibility and osseointegration. Here, the electro-assisted deposition of CaP on two different selfassembled monolayers (SAMs), 2-mercaptoacetic acid (MAA) and 2-mercaptoethanol (ME), was studied both at short (up to 3 min) and long (2 hours) deposition periods on well-defined evaporated gold surfaces. It was found that the end group of the monolayer has a major effect on the growth of the CaP coating. The deposition was slower and less electrically efficient on MAA SAM, but surface cracking was essentially eliminated due to reduction of the crystallographic mismatch. The carboxylic acid may
facilitate CaP growth by attracting Ca2+ ions to the surface, which could explain the higher amount of side reactions occurring at the beginning of the deposition.

Keywords: Calcium phosphate (CaP), hydroxyapatite (HAp), electrodeposition, self- assembled monolayers (SAMs)

Gravimetric and dynamic deconvolution of global EQCM response of carbon nanotube based electrodes by Ac-electrogravimetry

Authors: F. Escobar-Teran, A. Arnau, J.V. García, Y. Jiménez, H. Perrot, O. Sel

Journal: Electrochemistry communications (2016)

The capacity charge storage of carbon nanotube (CNT) based electrodes was investigated by ac-electrogravimetry which couples fast quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS). In contact with an aqueous NaCI electrolyte, evidence was found that there are two types of cations (Na+.H2O and H+) electroadsorbed with different kinetics for cathodic potentials and the Cl– ionsfor anodic potentials together with free water molecules. The reconstruction of the total mass response from independent ac-electrogravimetry measurements agrees perfectly well with the global EQCM response. Our findings reveal the unique sensitivity of the ac-electrogravimetry to provide a fair gravimetric and dynamic deconvolution of the global EQCM responses.

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Calcium-induced calmodulin conformational change. Electrochemical evaluation

Authors: Isabel P.G. Fernandes, Ana Maria Oliveira-Brett. Chemistry Department, Faculty of Sciences and Technology, University of Coimbra, 3004-535 Coimbra, Portugal.

Journal: Bioelectrochemistry (2016)

Calmodulin (CaM) is an essential protein present in all eukaryote cells, ranging from vertebrates to unicellular organisms. CaM is the most important Ca2+ signalling protein, composed of two domains,  N- and C-terminal domains, linked by a flexible central α – helix, and is responsible for the regulation of numerous calcium-mediated signalling pathways. Four calcium ions bind to CaM, changing its conformation and determining how it recognizes and regulates its cellular targets. The oxidation mechanism of native and denatured CaM, at a glassy carbon electrode, was investigated using differential pulse voltammetry and electrochemical impedance spectroscopy. Native and denatured CaM presented only one oxidation peak, related to the tyrosine amino acid residue oxidation. Calcium-induced calmodulin conformational change and the influence of Ca2+ concentration on the electrochemical behaviour of CaM were evaluated, and significant differences, in the tyrosine amino acid residue peak potential and current, in the absence and in the presence of calcium ions, were observed. Gravimetric measurements were performed with a graphite coated piezoelectric quartz crystal with adsorbed CaM and calcium aggregation by CaM was demonstrated.

You may read the full paper here