scholarly journals Label free detection of specific protein binding using a microwave sensor

The Analyst ◽  
2014 ◽  
Vol 139 (21) ◽  
pp. 5335-5338 ◽  
Author(s):  
Marcela Salazar-Alvarez ◽  
Olga Korostynska ◽  
Alex Mason ◽  
Ahmed Al-Shamma'a ◽  
Jakki C. Cooney ◽  
...  
Keyword(s):  
Protein Binding ◽  
Specific Binding ◽  
Protein A ◽  
Specific Protein ◽  
Label Free ◽  
Microwave Sensor ◽  
Label Free Detection

The specific binding of streptavidin to biotinylated protein A was demonstrated using a label free microwave sensor.

scholarly journals Microfluidic Impedance Biosensor Chips Using Sensing Layers Based on DNA-Based Self-Assembled Monolayers for Label-Free Detection of Proteins

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 80
Author(s):  
Khaled Alsabbagh ◽  
Tim Hornung ◽  
Achim Voigt ◽  
Sahba Sadir ◽  
Taleieh Rajabi ◽  
...  
Keyword(s):  
Troponin I ◽  
Electrochemical Impedance ◽  
Specific Binding ◽  
Self Assembled Monolayers ◽  
Significant Shift ◽  
Label Free ◽  
Label Free Detection ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
Biosensor Chip

A microfluidic chip for electrochemical impedance spectroscopy (EIS) is presented as bio-sensor for label-free detection of proteins by using the example of cardiac troponin I. Troponin I is one of the most specific diagnostic serum biomarkers for myocardial infarction. The microfluidic impedance biosensor chip presented here consists of a microscope glass slide serving as base plate, sputtered electrodes, and a polydimethylsiloxane (PDMS) microchannel. Electrode functionalization protocols were developed considering a possible charge transfer through the sensing layer, in addition to analyte-specific binding by corresponding antibodies and reduction of nonspecific protein adsorption to prevent false-positive signals. Reagents tested for self-assembled monolayers (SAMs) on gold electrodes included thiolated hydrocarbons and thiolated oligonucleotides, where SAMs based on the latter showed a better performance. The corresponding antibody was covalently coupled on the SAM using carbodiimide chemistry. Sampling and measurement took only a few minutes. Application of a human serum albumin (HSA) sample, 1000 ng/mL, led to negligible impedance changes, while application of a troponin I sample, 1 ng/mL, led to a significant shift in the Nyquist plot. The results are promising regarding specific detection of clinically relevant concentrations of biomarkers, such as cardiac markers, with the newly developed microfluidic impedance biosensor chip.

scholarly journals Measuring stepwise binding of a thermally fluctuating particle to a cell membrane without labeling

2019 ◽  
Author(s):  
A. Rohrbach ◽  
T. Meyer ◽  
H. Kress
Keyword(s):  
Cell Membrane ◽  
Specific Binding ◽  
Thermal Fluctuations ◽  
Membrane Receptors ◽  
Brownian Dynamic ◽  
Label Free ◽  
Binding Partners ◽  
Label Free Detection ◽  
A Cell ◽  
Position And Orientation

ABSTRACTThermal motions enable a particle to probe the optimal interaction state when binding to a cell membrane. However, especially on the scale of microseconds and nanometers, position and orientation fluctuations are difficult to observe with common measurement technologies. Here we show that it is possible to detect single binding events of IgG-coated polystyrene beads, which are held in an optical trap nearby the cell membrane of a macrophage. Changes in the spatial and temporal thermal fluctuations of the particle were measured interferometrically and no fluorophore labelling was required. We demonstrate both by Brownian dynamic simulations and by experiments that sequential step-wise increases in the force constant of the bond between a bead and a cell of typically 20 pN / µm are clearly detectable. In addition, this technique provides estimates about binding rates and diffusion constants of membrane receptors. The simple approach of thermal noise tracking points out new strategies in understanding interactions between cells and particles, which are relevant for a large variety of processes including phagocytosis, drug delivery or the effects of small microplastics and particulates on cells.SIGNIFICANCEInteractions of cells with nearby particles, e.g. bacteria, viruses or synthetic material, is a very fundamental and complex process, often deciding about the cellular fate. The investigation of binding processes between particle and cell is typically investigated by fluorescence techniques, where fluorophores often hinder the molecular interaction of specific binding partners. Therefore, label-free detection or imaging techniques are essential, which are hardly available especially for live cell investigations. Molecular binding is based on thermal position and orientation fluctuations of the binding partners to find the best interaction state. Here, we present a label-free measurement technique that allows us to detect multiple stepwise binding events of molecules on an optically trapped particle close to the cell membrane.

Real-Time Detection of Antigen–Antibody Reactions by Imaging Ellipsometry

2007 ◽  
Vol 60 (9) ◽  
pp. 667 ◽  
Author(s):  
Irina Chamritski ◽  
Mark Clarkson ◽  
Jeff Franklin ◽  
Shi Wei Li
Keyword(s):  
Real Time ◽  
Specific Binding ◽  
Protein A ◽  
Surface Proteins ◽  
Human Antibody ◽  
Label Free ◽  
Time Resolved ◽  
Imaging Ellipsometry ◽  
Antibody Complex ◽  
Antigen Antibody

In the field of proteomics the quantification of the affinity of an antibody to its partners and the evaluation of its specific binding is an important issue. With an imaging ellipsometer the interaction of an antibody with immobilized antigens on a model microarray is observed in a time-resolved and label-free manner. Imaging ellipsometry was developed for real-time monitoring of the biomolecule interaction between an antigen in solution and an antibody immobilized on a silicon surface. Proteins were immobilized by the formation of carboxy-alkyl monolayers on silicon substrates, where a biotin-labelled antibody was immobilized by a biotin–streptavidin linkage. Anti-human IgG bound specifically to human antibody and protein A, similarly anti-goat IgG bound to goat antibody. No binding was observed between anti-rabbit IgG and goat antibody. All stages of the formation of the antigen–antibody complex were imaged by imaging ellipsometry. By monitoring changes in y, the mole fraction θ of the antigen–antibody binding was determined. Immunological reactions of two different antigen–antibody combinations were fitted by the Langmuir adsorption equation, and affinity constants for two reactions were calculated.

scholarly journals Protein Binding Characteristics of the Principal Green Tea Catechins: A QCM Study Comparing Crude Extract to Pure EGCG

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Elsadig E. Ali ◽  
Mohamed O. Elmakki ◽  
Miranda L. Gavette ◽  
Brian J. Doyle ◽  
Shannon J. Timpe
Keyword(s):  
Protein Binding ◽  
Green Tea ◽  
Crude Extract ◽  
Chemical Constituents ◽  
Epigallocatechin Gallate ◽  
Protein Molecule ◽  
Detection Methods ◽  
Label Free ◽  
Binding Characteristics ◽  
Label Free Detection

Label-free detection methods such as the quartz crystal microbalance (QCM) are well suited to the analysis of molecular interactions in complex mixtures such as crude botanical extracts. In the present study, the binding characteristics of epigallocatechin gallate (EGCG) and crude green tea extract solutions to bovine serum albumin (BSA) have been investigated. The adsorbed mass levels onto BSA-functionalized surfaces were measured at various solution concentrations. Langmuir and Freundlich isotherms were used to model the adsorption data. The Langmuir isotherm better described the adsorption behavior with correlations of 0.68 and 0.70 for the EGCG and the crude extract solutions, respectively. The better fit of the Langmuir model indicates that adsorption occurs homogeneously and that aggregation is negligible. The mass saturation is estimated to be 58% higher for the crude green tea solution as compared to the pure EGCG solution (7.9 ng/cm2 for green tea and 5 ng/cm2 for EGCG). The increased adsorption for the crude extract indicates that the additional tea chemical constituents are binding to alternate sites on the protein molecule and that competitive binding is a nondominant effect. However, a reduced adsorption rate for the crude extract was also observed, indicating some presence of competitive mechanisms. The results demonstrate the utility of the QCM for the analysis of protein binding in crude mixtures as well as pure compounds.

Rapid and label-free detection of protein a by aptamer-tethered porous silicon nanostructures

2017 ◽  
Vol 257 ◽  
pp. 171-177 ◽  
Author(s):  
Katharina Urmann ◽  
Peggy Reich ◽  
Johanna-Gabriela Walter ◽  
Dieter Beckmann ◽  
Ester Segal ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Protein A ◽  
Silicon Nanostructures ◽  
Label Free ◽  
Label Free Detection

Label-free detection of protein binding with multisine SPR microchips

Lab on a Chip ◽  
2011 ◽  
Vol 11 (24) ◽  
pp. 4194 ◽  
Author(s):  
Tridib Ghosh ◽  
Layne Williams ◽  
Carlos H. Mastrangelo
Keyword(s):  
Protein Binding ◽  
Label Free ◽  
Label Free Detection

scholarly journals Effect of specific binding of human albumin, fibrinogen, and immunoglobulin G on surface characteristics of bacterial strains as revealed by partition experiments in polymer phase systems

1980 ◽  
Vol 29 (3) ◽  
pp. 879-885
Author(s):  
H Miörner ◽  
E Myhre ◽  
L Björck ◽  
G Kronvall
Keyword(s):  
Protein Binding ◽  
Surface Properties ◽  
Immunoglobulin G ◽  
Specific Binding ◽  
Polymer Concentration ◽  
Specific Protein ◽  
Bacterial Cells ◽  
Bacterial Strains ◽  
Human Proteins ◽  
Phase Systems

Four strains of gram-positive cocci with different combinations of positive binding of human proteins were investigated with respect to changes in physicochemical surface properties after specific protein binding. Staphylococcus aureus Cowan I, two group A beta-hemolytic streptococci, and one group G streptococcal strain were studied; they represented three different combinations of reactivity for human serum albumin, human immunoglobulin G, and fibrinogen. Using single-tube partition of bacterial cells in a dextran-polyethylene glycol system of constant polymer concentration but varying ionic compositions, it was possible to detect changes in the partition of bacteria after specific protein binding. There was a correlation between the binding of radiolabled human proteins to the bacterial strains and the effect of human proteins on the partition of the bacteria in the phase systems. Thus, the specific binding of proteins to the bacteria changes their physicochemical surface properties. These types of bacteria-protein interactions may play an important role in modulating host-parasite relationships.

scholarly journals Plasmonic random laser biosensor on fiber facet for label-free detecting biomolecules

2020 ◽  
Author(s):  
Xiaoyu Shi ◽  
Kun Ge ◽  
Junhua Tong ◽  
Tianrui Zhai
Keyword(s):  
Clinical Medicine ◽  
Specific Binding ◽  
Low Cost ◽  
Protein A ◽  
Random Laser ◽  
Label Free ◽  
Refractive Index Sensitivity ◽  
Near Surface ◽  
Medical Diagnostic ◽  
Index Sensitivity

Abstract Low-cost and miniaturized biosensors are key factors leading to the possibility of portable and integrated biomedical system, which play an important role in clinical medicine and life sciences. Random lasers with simple structures provide opportunities for detecting biomolecules. Here, a low-cost biosensors on fiber facet for label-free detecting biomolecules is demonstrated resorting to plasmonic random laser. The random laser is achieved resorting to a random plasmonic scattering structure of Ag nanoparticles and polymer film on fiber facet. Refractive index sensitivity and near-surface sensitivity of the biosensor are systematically studied. Furthermore, the biosensor is used to detect lgG through specific binding to protein A , exhibiting the detecting limit of 0.68 nM. It is believed that this work may promote the applications of plasmonic random laser bio-probe in portable or integrated medical diagnostic platforms, and provide fundamental understanding for the life science.

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