Modified Nanodiamonds for Adsorption of Propidium Iodide and Aflatoxin
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1236-SS09-05
Modified Nanodiamonds for Adsorption of Propidium Iodide and Aflatoxin Natalie M. Gibson1, Tzy-Jiun Mark Luo1, Olga Shenderova1, 2, Yong-Jae Choi1 and Donald W. Brenner1 1 Department of Materials Science and Engineering, North Carolina State University, 911 Partners Way, Raleigh, NC 27695 2 International Technology Center, P.O. Box 13740, Research Triangle Park, NC 27709 ABSTRACT Nanodiamonds (NDs) have desirable chemical, physical and biological properties that lend them to a wide range of applications. ND’s facile surface chemistry, for example, can be used to create a high affinity for adsorbing various biological molecules. However, NDs, which are commercially available from multiple vendors, show inconsistencies with surface groups, aggregate sizes and impurity contents that may limit adsorption. We explore adsorption mechanisms of molecules to NDs in efforts to expand ND applications to drug delivery agents, bio-labels and enterosorbents. In doing so, several types of NDs and modification methods are evaluated to increase adsorption capacity and selectivity of propidium iodide and aflatoxin B1. Capacities and binding strengths of target molecules are assessed by Langmuir isotherms and transform calculations. UV-Vis spectroscopy shows our modification treatments are successful in increasing ND adsorption capacities. Additionally, cyclic voltammetry measurements, used to monitor in-situ adsorption, show electrochemical detection even after binding. INTRODUCTION Detonation nanodiamonds (NDs) represent an emerging class of diamond material. The interest in NDs stems from their large specific surface areas (300-400 m2/g) and rich surface chemistry, which can be easily manipulated for specific applications. NDs have recently been shown to be biocompatible and noncytotoxic [1], opening up their applications to biology and medicine. Previously, NDs have been explored as carriers for active molecules and drug delivery agents [2]. Here, we explore adsorption mechanisms of molecules to the surface of NDs in an effort to develop new applications for NDs in drug delivery, bio-labeling and as enterosorbents. Propidium iodide (PI) was selected as a charged molecule model. PI is used widely in biology because its positive charge prevents penetration into positively charged cell membranes, so that only staining of dead cells is facilitated [3,4]. Because this dye has been extensively studied, we look to it for observing initial behaviors of positively charged molecules with ND aggregates. PI’s fluorescence is easy to detect with UV-Vis spectroscopy, meaning simple and time efficient measurements. Basic knowledge of electrostatic interactions between the molecule and NDs will allow for future development of NDs as drug delivery carriers and bio-labels. Aflatoxin B1 (AfB1), a carcinogenic and mutagenic by-product of mold growth found in crops and feedstuff [6], was selected as a neutral charged molecule model. Currently, hydrated sodium calcium aluminosilicate (HSCAS) clays are the most common enterosorbents for Af
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