Papers by Keyword: QCM-D

Abstract: An immunosensor is an analytical system consisting of specific immune system molecules coupled to a signal transducer. Immunosensor sensitivity depends on the type of immunorecognition ligands used, immobilization influence on their activity and orientation on the surface. Quartz crystal microbalance with dissipation (QCM-D) was employed to investigate the immobilization of antibodies against bovine leukemia virus antigen gp51 (gp51). Disulphide bridges of antibody hinge region were reduced chemically to yield two half antibody fragments (Frag-Ab), each having a single antigen binding site and free sulfhydryl groups that were used for immobilization. Frag-Ab were immobilized on planar gold and gold nanoparticle (AuNP) modified QCM-D sensor surfaces from initial solutions of different concentrations. Higher Frag-Ab surface density values were obtained on AuNP modified surfaces at all tested antibody concentrations. Frag-Ab/gp51 specific interaction was registered and it was determined that the highest sensitivity was exhibited by Frag-Ab immobilized at the lowest surface desities on both types of investigated surfaces. Specific gp51 interaction with Frag-Ab and non-specific binding to bovine serum albumin modified surfaces were compared by employing Δf/ΔD plots, which could serve as fingerprints of different processes.

Abstract: Hydroxyapatite (HAp) sensor, available for quartz crystal microbalance with dissipation (QCM-D) technique, has been fabricated by an electrophoretic deposition method. The method of re-usability of the sensor after adsorption of fibrinogen and the biological apatite (BAp) growth on the sensor with and without the adsorption of feral bovine serum (FBS) from 1.5 simulated body fluid were investigated. The re-usability of the sensor, cleaning with the combination of ammonia and hydrogen peroxide mixture and UV/ozone treatment, achieved ten times reuses. BAp was grown on the HAp surface but not on the gold surface at 37.5 oC for 40 hours. The viscoelastic property (DD/Df value) of the BAp layer on the HAp sensor showed harder than that of the protein adsorption films from FBS. The amount of the BAp grown on the HAp sensor adsorbed FBS is lower than that on the HAp sensor. The adsorption of FBS proteins on the HAp surface strongly inhibited the BAp growth.

Abstract: The adsorption of multiple proteins derived from fetal bovine serum (FBS) in phosphate buffer saline (PBS) and alpha minimum essential (aMEM) was in situ analyzed with a quartz crystal microbalance with dissipation technique on gold, titanium and HAp sensors. The adsorption behaviors of FBS proteins were varied depending on the sensors. The DD/Df value of the HAp sensor were clearly different in PBS and aMEM, and others were not changed. The viscoelastic properties of the protein films adsorbed on the HAp sensor in PBS were flexible in comparison with those on the gold and titanium sensors. The D-f plots incidated that the proteins adsorbed on HAp in PBS would lead to competitive adsorption and conformational change and those in aMEM could form a monolayer. The adsorption behavior on the HAp in carbonate buffer saline was found to be similar to that in aMEM. These differential adsorption behaviors on the HAp surface were attributed to the pre-adsorptive ion, such PO43- or CO32- in the solvent.

Abstract: Real time adsorption behaviors of six proteins with different isoelectric points on hydroxyapatite (HAp) nanocrystal surfaces have been investigated by using HAp sensors for quartz crystal microbalance with dissipation technique (QCM-D). The dissipation (D)–frequency (f) plots clearly showed that the different types of protein adsorption behaviors; the D-f plots of acidic proteins lie on one straight line with a constant slope under all initial protein concentrations, while those of neutral and basic proteins lie on two straight lines with different slopes. The acidic proteins formed a monolayer, while the neutral and basic proteins could cause conformational changes with the adsorbed amount of proteins. The QCM-D technique with novel HAp nanocrystal sensor is useful for the liquid phase changes of proteins on the surface.