Sensitive colorimetric detection for lysozyme based on the capture of a fixed thiol-aptamer on gold nanoparticles

In this work, a novel simple and sensitive detection method for lysozyme based on the surface plasmon resonance of gold nanoparticles has been developed. The lysozyme aptamer constantly immobilized on the surface of gold nanoparticles via a thiol functional group is the recognition element of lysozyme and a stabilizer of this system. The presence of lysozyme leads to the red-shift of the resonance wavelength of gold nanoparticles in accordance with its concentration. Two factors lead to the red spectral shift of gold nanoparticles, which are the increase of the refractive index in the environment surrounding the gold nanoparticles and the aggregation of gold nanoparticles. A critical point is distinguished from the spectral shift as a function of lysozyme concentration, where the dominant power influencing the redshift is transferred from the first one to the second one with the increase of lysozyme concentration. The limit of detection for lysozyme in this study is 0.054 nM, with a linear calibration ranging from 0.347 nM to 2.431 nM under the optimal usage conditions of 0.1250 nM thiol-aptamer functionalized gold nanoparticles. Therefore, this thiol-aptamer functionalized gold nanoparticle method provides a selective detection strategy for lysozyme and generates a great promising application.