Carboxylated/Oxidized Diamond Nanoparticles for Quantifying Immunoglobulin G Antibodies

Mhikee Janella N. Descanzo^1*, Avinash A. Patil¹, Justin Benedict A. Agcaoili¹, Cheng-Kang Chiang², Huan-Cheng Chang³, Wen-Ping Peng¹

¹Physics, National Dong Hwa University, Hualien County, Taiwan
²Chemistry, National Dong Hwa University, Hualien County, Taiwan
³Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei City, Taiwan

* Presenter:Mhikee Janella N. Descanzo, email:mndescanzo@yahoo.com

An understanding of how nanodiamonds (NDs) interact with antibodies (Abs) is necessary to maximize the efficiency of NDs in various applications, such as drug delivery, biomarkers for diagnosis, and therapeutics. In this work, the usefulness of the ND particles to directly quantify Ab, i.e. immunoglobulin G (IgG), in nanomolar (nM) concentration range using matrix-laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is demonstrated. The adsorption of IgG molecules with two types of NDs, i.e., carboxylated high-pressure high-temperature ND (HPHT-ND) and oxidized detonation ND (oxDND), is shown and is quantitatively analyzed using Langmuir-Freundlich isotherm model. The maximum adsorption capacity of oxDND (~6199 IgG molecules) is found to be much greater than that of HPHT-ND (~2851 IgG molecules). Furthermore, oxDND enabled the detection of lower IgG concentrations (< 10 nM) as compared to HPHT-ND. The tail-on orientation of most human chorionic gonadotropin (hCG)-β Abs on the oxDND surface is verified by analyzing the ion signal of hCG antigen recognized by the hCG-β Ab-oxDND conjugate and hCG-β Ab-Mag Beads Protein G conjugate. Compared to the commercially-available Ab-Mag Beads Protein G conjugate, the Ab-oxDND conjugate does not require a linker and can be used as simple antibody-antigen platform in immunodiagnostics.

Keywords: carboxylated/oxidized diamond nanoparticles, direct mass quantification, immunoglobulin G, Langmuir-Freundlich isotherm, tail-on orientation of antibody