Correlation of Capture Efficiency with the Geometry, Transport, and Reaction Parameters in Heterogeneous Immunosensors

Abstract

Higher capture efficiency of biomarkers in heterogeneous immunosensors would enable early detection of diseases. Several strategies are used to improve the capture efficiency of these immunosensors including the geometry of the system along with the transport and reaction parameters. Having a prior knowledge of the behavior of the above parameters would facilitate the design of an efficient immunosensor. While the contributions of the transport and reaction parameters toward understanding of the mechanism involved in capture have been well studied in the literature, their effect in combination with the geometry of the sensors has not been explored until now. In this work, we have experimentally demonstrated that the capture efficiency of the antigen-antibody systems is inversely related to the size of the sensor patch. The experimental system was simulated in order to get an in-depth understanding of the mechanism behind the experimental observation. Further, the extent of heterogeneity in the system was analyzed using the Sips isotherm to obtain the heterogeneity index (α) and the reaction rate constant (K(D)) as fitted parameters for a sensor patch of 1.5 mm radius. The experimental kinetic data obtained for the same sensor patch matched reasonably with the simulation results by considering K(D) as the global affinity constant, which indicated that our system can be considered to be homogeneous. Our simulation results associated with the size dependency of the capture efficiency were in agreement with the trends obtained in our experimental observations where an inverse relation was observed owing to the fact that the mass-transfer limitation decreases with the decrease in the size of the sensor patch. The possible underlying mechanism associated with size dependency of capture efficiency was discussed based on the time-dependent radial variation of captured antigens obtained from our simulation results. A study on the parametric variation was further conducted for the nonmixed and mixed systems on the transport (Deff), reaction (K(D)), and geometric parameters (R). Two different correlations were established for the nonmixed and mixed systems between the capture efficiency (f) and a nondimensional number (t(D)/t(R)) consisting of the above-mentioned parameters. Such unified relations will be useful in designing heterogeneous immunosensors and can be extended to microfluidic immunosensors.

Investigation of Mechanisms Involved in the Enhanced Label Free Detection of Prostate Cancer Biomarkers Using Field Effect Devices

“…These experimental observations utilizing the covalently attached antibodies support the hypothesis of Landheer et al 8 and Wunderlich et al 11 (Figure 6b), while Shalev et al 12 obtained experimental results opposite to these theoretical models by using the adsorbed proteins (Figure 6c). Unlike adsorbed biomolecules, the covalently attached biomolecules do not cover the entire surface of the dielectric (shown in Figure 6b) because of higher degree of up-right/end-on orientation 29,30 allowing for the protonation/deprotonation of the hydrogen ions on the dielectric surface which neutralize the effect of charges associated with the biomolecules. It was also seen that the APTES modified SiO 2 surface was not completely covered during the electrostatic attachment of silica nanoparticles 23 which was further confirmed by observing the presence of both type of surface sites i.e.…”

“…Then the devices were treated with 1% casein as a blocking agent, and the schematic of the antibody attached surface is shown in Figure 1e with preferred degree of upright orientation of antibodies. 29,30 Binding of PSA was done by keeping the 20 μL of PSA solutions on the sensor surface of concentrations ranging from 10 pg/ml to 10 ng/ml using the optimum conditions reported elsewhere 31 to obtain maximum antigen binding i.e. for 30 minutes at 37 • C. Then, the sensor was thoroughly rinsed with PBS to remove adsorbed antigens and dried with N 2 gas, the schematic of antigen bound with antibodies are shown in Figure 1f.…”

Using Cell Membranes as Recognition Layers to Construct Ultrasensitive and Selective Bioelectronic Affinity Sensors

“…Comparing the analytical characteristics achieved for the 5 min versus the 20 min incubation-based assays, a reasonable 4-fold reduction in sensitivity and corresponding widening of the linear TNF-α concentration range were obtained (Table S1). These findings suggest the possibility of tailoring the analytical parameters of the cell membrane-based biosensor by controlling the incubation time of the sample to the bioreceptors, similar to what has been employed previously for affinity-based electrochemical sensors. − …”

Toward the Development of Rapid, Specific, and Sensitive Microfluidic Sensors: A Comprehensive Device Blueprint

“…At these conditions, we can ensure that the fraction of bound sites ( b eq / b max ) is detectable for C 0 ≪ K D using conventional detection methods. To achieve this goal, d can be easily tailored by simply coating a larger area of the device substrate with receptors, depending on the application. ,− On the other hand, tailoring b max is more challenging yet has the most significance. − …”