ISDRS 2007, December 12-14, 2007, College Park, MD, USA

ISDRS 2007 – http://www.ece.umd.edu/ISDRS

Engineered Surfaces of Multifunctional and Molecular Diamond for Biosensing Sanju Gupta

Department of Electrical and Computer Engineering, University of Missouri, Columbia, MO 65211

With the increasing number of threats from both the chemical and biological agents since 9/11 attack and deaths from anthrax contamination, adaptable and fast methods of detection of those agents have become imperative. Food safety, on the other hand, especially with regard to foodborne pathogens, is another important issue. Foodborne disease is one of the most common causes of morbidity and mortality around the world and more than 200 known diseases are transmitted through food produce. A wide variety of fresh or minimally processed fruits, vegetables and fruit juices have been linked to foodborne diseases [1, 2]. This is despite the fact that America's food supply is one of the safest in the world. Therefore, the need for rapid and/or real-time detection of pathogens becomes extremely important for the food industry as well as homeland security. Biosensors, by definition, are analytical devices incorporating a biological material (tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, natural products etc.), a biologically derived material (recombinant antibodies, engineered proteins, aptamers etc.) or a bio-mimic (synthetic catalysts, combinatorial ligands, imprinted polymers), associated with or integrated within a physiochemical transducer, which may be optical, electrochemical, magnetic or micromechanical [3]. They usually yield either fluorescence signal or a digital signal which is proportional to the concentration of a specific analyte or group of analytes [4]. This work presents the novel ideas of engineered surfaces of multifunctional and molecular diamond for immobilization of bio-molecules as viable and potential platforms. With the recent development in nanoscience and nanotechnology, carbon-based nanomaterials (e.g. fullerenes, nanotubes, nanodiamond) are receiving much attention due to their remarkable physical and structural properties. The importance of carbon nanomaterials in biological applications has been recently recognized [5]. The cutting-edge technologies of nanodiamond (thin film or powder form) are proposed in the development of next generation biosensors as potential candidates [6]. However, the immobilization of antibodies on the sensor platform to convert a non-electrical, physical or chemical, quantity into an electrical signal is the key for the control and the improvement of the performance of such a biosensor. Therefore, the proposed research is geared towards the development of synthetic nanodiamond-based biosensing platforms because of their inherent advantages for rapid detection of foodborne pathogenic microorganisms. Among the family of advanced carbon materials, diamond is of great interest owing to their several unsurpassable physical (mechanical, electrical, thermal, and chemical inertness and biocompatible) properties for multitude of applications. Thus diamond presents a great potential for biosensor substrates. Diamond (in particular, nanodiamond) is unique when compared with established semiconducting material i.e. Si for bio-applications. It is attributed to a unique combination of structural and physical properties including smoother surfaces, easy surface modification, physicochemical stability, chemical sensitivity and specificity, bio-inertness and biocompatibility, making nanodiamond almost an ideal material for next generation biosensors surfaces as well as nano-bio integration. There are several lesser-known surface properties that potentially make nanodiamond promising, for instance, the chemical inertness of diamond makes it suitable for most biological environments. Therefore, it is envisaged that nanodiamond may prove to be even better drug carrier, imaging probe, or implant coating for biological systems compared to currently used nanomaterials. The surface of the most diamond thin films grown using plasma-enhanced chemical vapor deposition (PECVD) is terminated with hydrogen forming hydrogen−carbon (C-H) bonds that are extremely stable and resistant to chemical attack. In addition, conducting diamond films such as nanocrystalline diamond have superior electrochemical properties offering wide potential window. Chemical immobilization of electro-active enzymes on as- prepared diamond thin films is laying the basis for carbon-based biosensors and bio-interfaces. The present paper aimed to introduce novel concept and novel forms of diamond for biosensing applications including ultra dispersed diamond (powder) and ultra-nanocrystalline diamond (thin film deposited on Si). Several types of studies were performed to determine the fluorescence and chemical modification of the diamond surfaces. A general scheme for immobilization of Protein A is shown in

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ISDRS 2007, December 12-14, 2007, College Park, MD, USA

ISDRS 2007 – http://www.ece.umd.edu/ISDRS

Figure 2. Shown are the SEM, AFM and TEM images of ultrananocrystalline and ultradispersed diamond surfaces revealing the surface morphology. Micro-Raman spectra showing characteristic nanodiamond peaks (labeled D and G) is also shown.

Figure 1. Shown is the scheme for immobilization of Protein A on nanodiamond surface consisting of salinization followed by functionalization.

Figure 1. The surface morphologies of the two types of nanodiamond used is shown in Figures 2 and 3 and the nanoscale structure is apparent. For both the kinds of films, the grain size varied between 2-10 nm assessed using AFM and TEM analytical tools. Studies of the materials’ fluorescence identified several natural emission peaks that are dependent on the excitation wavelength. Chemical surface functionalization and protein immobilization were evaluated via scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy analytical tools. SEM shows that bio-functionalization drastically changes the morphology of the diamond surface. It was also determined that fluorescently labeled Protein A can be successfully immobilized to the functionalized diamond by acquiring its characteristic fluorescence emission peak thus retaining its integrity. These initial observations suggest the diamond surfaces as a potential platform for rapid detection of bio-agents. The present work is discussed in terms of a) the affinity of nanodiamond surfaces and hydrogen plasma treatment and b) the efficacy and efficiency of covalent binding of bio-molecules. *This work is partly supported in parts by MU Research Council and MU Biology and Bioprocessing Center (BBC) Grants. The author acknowledges Dr. S. Grant and her student J. Mimisevich. References [1] L. R. Beuchat, “Pathogenic microorganisms associated with fresh produce” J. Food Protection, 59, 204-216 (1996). [2] L. R. Beuchat, “Surface decontamination of fruits and vegetables eaten raw: A review” Food Safety Unit, World Health Organization (WHO/FSF/FOS/98.2) (1998). [3] B. M. Paddle, “Biosensors for chemical and biological agents of defense interest”, Biosensors and Bioelectronics 11, 1079-1113 (1996). [4] V. I. Efremenko, S. V. Stolbin, and L. I. Grekov, “Biosensors and their applications”, Prikl. Biokhim. Mikrobiol. 26, 11-8 (1990). [5] W. Yang, O. Auciello, J. E. Butler, W. Cai, J. A. Carlisle, J. E. Gerbi, D. M. Gruen, T. Knickerbocker, T. L. Lasseter, J. N. Russell, L. M. Smith, and R. J. Hamers, “DNA-modified nanocrystalline diamond thin-films as stable, biologically active substrates”, Nature Materials, 1, 253-257 (2002). [6] H. G. Craighead, “Nanostructure science and technology: Impact and prospects for biology”, J. Vacuum Science & Technology A. 21(5) S216-S221 (2003).