Two‐Protein Modified Gold Nanoparticles for One‐Step Serological Diagnosis

Nanoparticles based on noble metals such as gold are characterized by their surface plasmon resonance (SPR). Aggregation of gold nanoparticles causes an interparticle plasmon coupling, which can be observed as a redshift in the maximum absorbance. This behavior is employed in the presented work to detect antibodies in human sera samples. Analysis of Lyme borreliosis is considered as a model in the here case. Therefore, gold nanoparticles are synthesized and modified with two proteins, surface VlsE Borrelia antigen and protein A. The specific interaction of the two proteins with anti‐Borrelia antibodies result in aggregation of the gold nanoparticles. Three different sizes (20, 30, and 40 nm) are tested; a convenient recognition of antibodies is achieved with all sizes using spectroscopic measurements. In addition, 30 nm particles show a very promising colorimetric detection; accumulation of nanoparticles could be easily observed using naked eyes. The size of the modified particles show a crucial impact on the assay time; 3 h, 30 min, and 1 min as incubation time, are needed to obtain considered results when 20, 30, and 40 nm particles are used, respectively. The proposed test can be performed only in one step with no additional washing steps, making it advantageous over the other conventional methods. The test is promising, simple, and suitable for point‐of‐care testing. Applying of the proposed platform to other assays is suggested for rapid analysis.