Page 1 of 18 Submitted to Environmental Science & Technology 1 2 3 4 5 6 7 8 9 10 Size-exclusive Nanosensor for Quantitative Analysis of 11 12 Fullerene C60: A Concept Paper 13 1 14 SAMUEL N. KIKANDI, VERONICA A. OKELLO, QIONG WANG, * OMOWUNMI A. SADIK 15 Center for Advanced Sensors & Environmental System (CASE) 16 Department of Chemistry 17 State University of New York-Binghamton 18 P.O. Box 6000 19 20 Binghamton, NY 13902-6000 21 22 KATRINA. E.VARNER 23 US-EPA/NERL 24 Environmental Sciences Division 25 P.O. Box 93478-3478 26 27 Las Vegas, NV 89193-3478 28 29 SARAH A. BURNS 30 Department of Chemistry 31 359 Natural Sciences Complex 32 State University of New York-Buffalo 33 Buffalo, NY 14260-3000 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 *Corresponding Author:(607)777-4132;Fax:(607)777-4132,E-mail:[email protected] ACS Paragon Plus Environment Submitted to Environmental Science & Technology Page 2 of 18 1 2 3 4 5 6 ABSTRACT 7 This paper presents the first development of a mass-sensitive nanosensor for the isolation 8 and quantitative analyses of engineered fullerene (C ) nanoparticles, while excluding 9 60 mixtures of structurally similar fullerenes. Amino-modified beta cyclodextrin (β-CD-NH2) was 10 1 11 synthesized and confirmed by HNMR as the host molecule to isolate the desired fullerene 12 C60. This was subsequently assembled onto the surfaces of gold-coated quartz crystal 13 microbalance (QCM) electrodes using N-Dicyclohexylcarbodiimide/N-hydroxysuccinimide 14 (DCC/NHS) surface immobilization chemistry to create a selective molecular configuration 15 described as (Au)-S–(CH2)2-CONH-beta–CD sensor. The mass change on the sensor 16 configuration on the QCM was monitored for selective quantitative analysis of fullerene C60 17 14 16 2 18 from a C60/C70 mixture and soil samples. About ~10 -10 C60 particles/cm were successfully 19 quantified by QCM measurements. Continuous spike of 200 µl of 0.14 mg C60 /ml produced 20 changes in frequency (-∆f) that varied exponentially with concentration. FESEM and Time-of- 21 Flight Secondary Ion Mass Spectrometry (ToF-SIMS) confirmed the validity of sensor surface 22 chemistry before and after exposure to fullerene C60. The utility of this sensor for spiked real- 23 world soil samples has been demonstrated. Comparable sensitivity was obtained using both 24 25 the soil and purified toluene samples. This work demonstrates that the sensor has potential 26 application in complex environmental matrices. 27 28 29 KEYWORDS: Fullerenes, Nanotechnology, Engineered Nanomaterials, Implications, Toxicity, 30 Cyclodextrin, Nanosensors. 31 32 33 Introduction: 34 The discovery of fullerenes in 1985 has ushered in an explosive growth in the applications of 35 engineered nanomaterials (ENMs) and products (1-5). The rapid development of 36 nanotechnology and the increasing production of nanomaterials-based products and 37 processes present great opportunities and challenges. To date, the potential impacts of 38 nanomaterials on human health and the environment have been limited due to insufficient 39 40 understanding of the risks associated with its development, manipulation and wide-ranging 41 applications. The first step in assessing the risks posed by ENMs is to develop a broad array 42 of analytical tools and methods that are applicable to a wide range of manufactured 43 nanomaterials. Conventional methods of assessing the properties and characteristics of raw 44 nanomaterials focus on the size distribution and effects. They are, however, unsuitable for 45 detection and quantification of complex environmental samples or for differentiating between 46 47 the total or dissolved metal fractions or metal oxidation states. The toxicity, detection and 48 characterization of nanomaterials are dependent on factors such as functionalization, 49 geometry, and the type of nanomaterials. For example, the cytotoxicity of fullerenes can be 50 decreased following its hydroxylation with 24 hydroxyl groups(3), while the cytotoxicity of 51 carbon nanomaterials may be enhanced if it was functionalized with carboxylic acid 52 moieties(4). The potential toxicity of fullerenes and its derivatives is still a subject of intense 53 discussion (5). Some reports depict fullerenes as non-toxic while others demonstrate their 54 55 ability to both quench and generate reactive oxygen species(ROS) (6), which may lead to 56 DNA damage(7). Additionally, positive cytotoxicity and genotoxicity have been reported for the 57 water-soluble C60 aggregates (nC60) despite its low hydrophobicity(8). 58 59 2 60 ACS Paragon Plus Environment Page 3 of 18 Submitted to Environmental Science & Technology 1 2 3 4 5 6 The first step to a better understanding of the fate and transport of fullerenes and other 7 nanomaterials is to develop reliable metrology and analytical sensors. These offer novel 8 screening and monitoring approaches towards a better understanding of engineered 9 10 nanomaterials. Nanosensors can be classified under two main categories(1, 9): (i) 11 Nanotechnology-enabled sensors or sensors that are themselves nanoscale or have 12 nanoscale materials or components, and (ii) Nanoproperty-quantifiable sensors. 13 Nanomaterials dimensions are on the same scale as biomolecules, which unveils exciting 14 possibilities for their interaction with biological species, such as microbial, tissue, cells, 15 antibodies, DNA and other proteins. Type I sensors have been used for the construction of 16 enzyme sensors, immunosensors and genosensors, to achieve direct wiring of enzymes and 17 18 relative components to electrode surface, to promote spectroelectrochemical reaction, to 19 impose barcode for biomaterials and to amplify signal of biorecognition event[(10, 11). 20 Extensive research papers and reviews using nanomaterials for chemical and bioassays have 21 since been published (1, 5). 22 Despite the enormous literatures, there are few sensors to measure nanoscale 23 properties or sensors belonging to Type II. This class of nanosensors is an area of critical 24 25 interest to nanotoxicology, detection and risk assessment, as well as for monitoring of 26 environmental and/or biological exposures to nanomaterials such as fullerene C60. This is 27 important because engineered fullerenes C60 which are prepared via thermal reactions always 28 exist as a mixture of C60, C70 and higher homologues. While supramolecular complexation 29 with host-guest recognition is a well-studied topic (12-14), and nanomaterials have been 30 widely reported as components of sensing or other applications, to the best of our knowledge, 31 there has neither been fullerene sensors reported nor the assembly of β-CD achieved onto 32 33 mass selective transducers for C60 nanoparticle sensing applications. This paper presents the 34 development of Category II nanosensor for the isolation and quantitative analyses of 35 engineered fullerene C60 while excluding other structurally similar fullerenes C70 and higher 36 homologues. 37 38 Experimental section: 39 40 Microgravimetric measurements: Microgravimetric measurements were performed following 41 a conventional procedure(15). Briefly, all microgravimetric QCM experiments were performed 42 using a QCA 917-quartz crystal analyzer (Seiko EG&G). This was an open circuit system 43 where only the gold-coated quartz crystal (QA-A9M-Au(M)) from Advanced Meas. Tech. (Oak 44 Ridge, TN)working electrode (QCM, area ~ 0.2 cm2) was connected in the absence of the 45 auxiliary and the reference electrodes.). The resonators consisted of gold thickness layer of 46 47 300 nm and a frequency resolution of 0.1 Hz at a sampling rate of 100 ms, allowing excellent 48 sensitivity down into the nanogram region. These resonators were mounted onto a Teflon 49 well-type electrochemical cell(15) then soaked with test solutions. Buffalo River Sediments soil 50 samples were obtained from, National Institute of Standards and Technology, Gaithersburg, 51 MD 20899, (Lot # 8704). 52 53 β 54 Synthesis of Cyclodextrin Derivatives: The sensor fabrication started with the synthesis of 55 or γ-cyclodextrin derivatives consisting of amino-functionalized derivatives of cyclodextrins 56 designated as: β-CD-NH2 1 and γ-CD-NH2 2(Supplementary Figure 1A). The synthesis of 57 these derivatives utilized previous literature procedures with slight modifications (16): Briefly, 58 0.72 g of either β–CD or γ-CD was treated with 1.2 g toluene-2-sulfonyl chloride, TsCl (Sigma- 59 3 60 ACS Paragon Plus Environment Submitted to Environmental Science & Technology Page 4 of 18 1 2 3 4 5 6 Aldrich,US) and ethylenediamine(1 ml)(Sigma-Aldrich, US) in 20 mL pyridine (Sigma-Aldrich, 7 US) and the mixture was refluxed for 7 hours resulting in yellow solids. The yellow solids were 8 designated as β-CD-NH 1 or γ-CD-NH 2. These synthetic products (1 & 2) were stored 9 2, 2 10 under ultra high purity nitrogen (UHP) until they were utilized for the immobilization onto the 11 QCM surface. 1 12 Successful synthesis of 1 and 2 were confirmed by HNMR spectra recorded on a 13 Bruker AM 360 spectroscopic system equipped with 8.45 T magnet and multinuclear and 14 inverse detection capabilities at 360MHz at 20 °C using D2O solvent (Supplementary Figure 15 1B). The 1HNMR sample concentrations were approximated as 25 mg/mL of β–CD, β–CD- 16 17 NH2 1, γ–CD and γ–CD-NH2 2. Compound 1, showed characteristic NH2 and methylene 18 protons with chemical shifts at δ ~2.2ppm and δ ~3.0 ppm respectively. Compound 2 showed 19 similar chemical shifts at δ ~ 2.2 and 2.8 ppm for NH2 and methylene protons respectively 20 (data not included). Chemical shifts from both compounds 1 and 2 were consistent with the 21 calculated theoretical chemical shifts values using ChemDraw for NH2 and CH2-protons (δ 22 =2.0 and δ=2.8 ppm respectively).