Thermal-induced Immuno-nephelometry Using Gold Nanoparticles Conjugated with a Thermoresponsive Polymer for the Detection of Avidin

Abstract

Thermoresponsive immunonephelometry was achieved with biotinylated poly(acrylate) and thermoresponsive gold nanocomposites composed of 13-nm gold nanoparticles and thermoresponsive polymers containing triethylenetetramine and biotin groups. The avidin-biotin interaction was used to model an immunoreaction in order to demonstrate thermoresponsive immunonephelometry. In the absence of avidin, positively charged gold nanocomposites electrostatically interacted with biotinylated poly(acrylate) to form binary complexes, in which the charges canceled each other out. The charge cancelation resulted in the binary complexes precipitating when the solution was heated above the phase-transition temperature. However, adding avidin formed ternary sandwich complexes through the avidin-biotin interaction. The ternary complexes remained sufficiently soluble above the phase-transition temperature because of the spatial isolation of the positive and negative charges. The transmittance of the solution containing the thermoresponsive gold nanocomposites and biotinylated poly(acrylate) at 37 C increased as the avidin concentration increased. A sigmoidal profile was observed from 10 -6.5 to 10 -5.5 mol/L. The concentration of avidin spiked in bovine serum was determined by our method.

Acoustic Sensing Based on Density Shift of Microspheres by Surface Binding of Gold Nanoparticles

“…Metal NPs-such as gold NPs (AuNPs) and silver NPs-are most extensively employed because various sizes and shapes are available, their surface can be biologically or chemically modified in relatively simple ways, and they often exhibit characteristic colors originating from plasmon absorption. [2][3][4][5][6][7] AuNPs usually have a reddish color, and their absorption wavelength strongly depends on the particle size. Therefore, if they are aggregated as the result of a reaction with mediators, the mediators can be detected according to any color change, even with the naked eyes.…”

“…The aggregation of metal NPs has also been applied to surface-enhanced Raman scattering (SERS) [8][9][10] and light-scattering detection. 7,11 The manipulation and separation of particles play key roles in the successful implementation of particle-based bioanalyses. The magnetic nature of the particles allows easy manipulation or separation because they are attracted or repelled by a magnet.…”

Numerical Modelling of the Optical Properties of Plasmonic and Latex Nanoparticles to Improve the Detection Limit of Immuno-Turbidimetric Assays

“…Hence, we modelled the extinction of oligomers formed by a larger number of NPs (up to 11). Given all the possible arrangements for nanospheres in an oligomer, the calculations have been focused on some geometric arrangements that can be associated with the formation of linear, fractal, or compact clusters [50][51][52], considering three nanosphere sizes corresponding to commercially available latex beads of 77 (PS_77, Figure 2A-C), 127 (PS_127, Figure 2D-F), and 200 nm (PS_200, Figure 2G-I) [1][2][3]7]. For the three sizes considered, the trends of Cext/NP, the absolute ΔCext/NP in m 2 , and the relative ΔCext/NP in per- Dimers are just the first type of oligomers that form at low antigen concentration [50][51][52][53].…”

“…In turbidimetric assays, the quantity of the analyte is correlated to optical extinction through a colloid of nanoparticles (NPs) that selectively undergo aggregation and scattering of light in the presence of the target compound [ 1 , 2 , 3 , 4 ]. These assays are widely used in medicine for measuring the concentration of various biological components but find application also in environmental, food, and agriculture analysis [ 3 , 5 , 6 ].…”

“…In turbidimetric assays, the quantity of the analyte is correlated to optical extinction through a colloid of nanoparticles (NPs) that selectively undergo aggregation and scattering of light in the presence of the target compound [ 1 , 2 , 3 , 4 ]. These assays are widely used in medicine for measuring the concentration of various biological components but find application also in environmental, food, and agriculture analysis [ 3 , 5 , 6 ]. Immuno-turbidimetric assays usually rely on surface functionalized submicrometric latex spheres because of their low cost, uniform tailorable diameter, ease of surface functionalization with selective targeting units, colloidal stability, and linearity of the light scattering intensity in the visible range at increasing levels of aggregation [ 1 , 2 , 3 , 4 , 6 , 7 ].…”