Low density lipoprotein detection based on antibody immobilized self-assembled monolayer: investigations of kinetic and thermodynamic properties.
ABSTRACT Human plasma low density lipoprotein (LDL) immunosensor based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) was fabricated by immobilizing antiapolipoprotein B (AAB) onto self-assembled monolayer (SAM) of 4-aminothiophenol (ATP). The AAB/ATP/Au immunosensor can detect LDL up to 0.252 microM (84 mg/dL) and 0.360 microM (120 mg/dL) with QCM and SPR, respectively. The SPR and QCM measurements were further utilized to study the reaction kinetics of the AAB-LDL interaction. The adsorption process involved was explored using Langmuir adsorption isotherm and Freundlich adsorption models. The thermodynamic parameters such as change in Gibb's free energy (DeltaG(ads)), change in enthalpy (DeltaH(ads)), and change in entropy (DeltaS(ads)) determined at 283, 298, and 308 K revealed that the AAB-LDL interaction is endothermic in nature and is governed by entropy. Kinetic, thermodynamic, and sticking probability studies disclosed that desorption of the water molecules from the active sites of AAB and LDL plays a key role in the interaction process and increase in temperature favors binding of LDL with the AAB/ATP/Au immunosensor. Thus, the studies were utilized to unravel the most important subprocess involved in the adsorption of LDL onto AAB-modified ATP/Au surface that may help in the fabrication of LDL immunosensors with better efficiency.
Article: Surface-Plasmon-Resonance-Based Fiber-Optic Sensor for the Detection of Low-Density Lipoprotein[show abstract] [hide abstract]
ABSTRACT: We report the fabrication and characterization of a surface plasmon resonance (SPR)-based fiber-optic sensor for the detection of low-density lipoprotein (LDL). The probe is prepared by first coating a 50-nm-thick gold film on the unclad portion of the optical fiber core and then immobilizing 4-aminothiophenol (4-ATP), followed by antiapolipoprotein B, over the 4-ATP/Au surface. Spectral interrogation technique is used for the characterization of the probe. SPR spectra are recorded for sample solutions of LDL with concentrations in the range of 0–190 mg/dl. Sensitivity of the sensor is found to be 0.18387 nm per mg/dl. Furthermore, the response time of the sensor is very small (around 2 min). The sensor can be utilized in online monitoring as well. This paper may result in the commer-cialization of a miniaturized low-cost reusable fast and accurate optical fiber sensor for the detection of LDL level in human blood.IEEE Sensors Journal 01/2012; 12. · 1.52 Impact Factor
Article: Evaluation of intact-and fragmented-antibody based immunosensors by total internal reflection ellipsometry[show abstract] [hide abstract]
ABSTRACT: a b s t r a c t Total internal reflection ellipsometry (TIRE) technique was used to investigate biological recognition lay-ers of immunosensors in order to estimate orientation of immobilized intact-and fragmented-antibodies. Two differently prepared biological recognition layers formed on gold-substrate were investigated: one layer was based on intact-antibodies (intact-Ab), second layer was based on chemically fragmented specific-antibodies (frag-Ab), which were obtained by reduction of intact-Ab. It was shown that TIRE enables to resolve differences in nanostructures of intact-Ab and frag-Ab layers. A multilayer model applied in our calculations shows that the distance between fragmented-antibody active sites and gold-surface after the immobilization process is lower than theoretical dimension of fragmented-antibodies. Moreover, it was calculated that analytical sensitivity of the () parameter of TIRE was 5.89 times better if compared to the sensitivity of the « () parameter, which is in fact similar to the sensitivity of surface plasmon resonance (SPR) based immunosensors.Sensors and Actuators B Chemical 01/2011; 160:555-562. · 3.90 Impact Factor