Conjugation of Antibodies to Gold Nanorods through Fc Portion: Synthesis and Molecular Specific Imaging

Abstract

Anisotropic gold nanorods provide a convenient combination of properties, such as tunability of plasmon resonances and strong extinction cross-sections in the near-infrared to red spectral region. These properties have created significant interest in the development of antibody conjugation methods for synthesis of targeted nanorods for a number of biomedical applications, including molecular specific imaging and therapy. Previously published conjugation approaches have achieved molecular specificity. However, the current conjugation methods have several downsides including low stability and potential cytotoxicity of bioconjugates that are produced by electrostatic interactions as well as lack of control over antibody orientation during covalent conjugation. Here we addressed these shortcomings by introducing directional antibody conjugation to the gold nanorod surface. The directional conjugation is achieved through the carbohydrate moiety, which is located on one of the heavy chains of the Fc portion of most antibodies. The carbohydrate is oxidized under mild conditions to a hydrazide reactive aldehyde group. Then, a heterofunctional linker with hydrazide and dithiol groups is used to attach antibodies to gold nanorods. The directional conjugation approach was characterized using electron microscopy, zeta potential and extinction spectra. We also determined spectral changes associated with nanorod aggregation; these spectral changes can be used as a convenient quality control of nanorod bioconjugates. Molecular specificity of the synthesized antibody targeted nanorods was demonstrated using hyperspectral optical and photoacoustic imaging of cancer cell culture models. Additionally, we observed characteristic changes in optical spectra of molecular specific nanorods after their interactions with cancer cells; the observed spectral signatures can be explored for sensitive cancer detection.

A Novel Method for Preparation of Gold NanoBipyramids Using Microwave Irradiation and Its Application in Immunosensors

“…The A.R decreased during the conjugation procedure. 22 With NBP amplification, shown in Fig. 8, both frequencies were changed when the concentrations of CAP were 0.5 ppm.…”

Comparative review of interferometric detection of plasmonic nanoparticles

“…Examples from these reviews include cell imaging using nanorods [9] and nanoshells [21]. Instruments based on hyperspectral darkfield have enabled quantitative molecular imaging [22] and spectral multiplexing [7], using functionalized nanoparticles where an antibody conjugate provides molecular specificity [4,23]. These instruments are even capable of detecting plamonic shifts due to coupling which can then be used to provide additional spatial information [24][25][26].…”

“…There have been a number of reviews that focus on development and synthesis of nanoparticle structures [1][2][3][4][5], as well specific applications for optical imaging [6]. However, there has been little attention paid to determining optimal methods for discriminating the presence and concentration of nanoparticles as optical contrast agents.…”

A New Core–shell Hybrid Nanostructures of Gold Nanorod for Enhancing Fluorescence and Application in Dual-Color Imaging

“…[1][2][3] In the past studies, Eustis and ElSayed investigated the relative intensity of the emission from AuNRs of various aspect ratios and theoretical treatments were also carried out. 4 After that, Tcherniak et al reported one-photon luminescence of gold nanospheres and nanorods using single particle spectroscopy and presented a mechanism describing one-photon luminescence.…”