Immunogold Nanoparticles Recognition imaging by Direct Atomic Force Microscopy

Abstract

We have developed a method that integrated the widely used nanogold immunoassay into direct atomic force microscopy (AFM) imaging and provided a specific morphological technique applying for virus identification. The series of specimens including bare gold particles (Au), antibody-conjugated gold particles (Au-Ab), purified influenza virions (H1N1), antibody-bound virions (H1N1-Ab) and virion-immunogold complex (H1N1- Ab-Au) were investigated by AFM and transmission electron microscopy stepwisely and parallelly. The recognition method of the immuno-AFM technique was constructed by taking the local phase contrast in phase image as main judgment for the existence of immunogold labels and taking the height and amplitude images as auxiliary judgment for viral morphology and positioning. The nanogold-antibody conjugates binding to the H1N1 virions were clearly identified as higher brightness spots from the background biomaterials. Under direct AFM, the topographical image of the scanned biosamples can be easily investigated and reproduced. Our findings achieved the combination of virus morphological features with antibody-antigen specific recognition through the application of antibody-specific nanogold labels and, in principle, the labels for immuno-AFM could be extended to other types of nanomaterials for bio-recognition and localization assay.