Monitoring the functionalization of single-walled carbon nanotubes with chitosan and folic acid by two-dimensional diffusion-ordered NMR spectroscopy
Introduction
Over the past decade, the interest for using carbon nanotubes (CNTs) functionalized with different types of biomolecules has increased [1], [2], [3]. The nanometer size and unique physical properties of CNTs make them attractive for anticancer drug delivery [4], [5], [6], [7], [8], molecular transport [9], [10], [11], and new therapeutic mechanisms [12], [13]. CNTs have been activated to target various cancer cells using folic acid (FA). FA is an attractive ligand that is useful for targeting cell membranes and enhancing CNTs endocytosis by the folate receptor [14], [15]. FA receptors can be direct targets for drug delivery [16], which explains the diversity of strategies used for folate conjugation.
Conventionally, CNTs–FA has been characterized by UV–Vis (ultraviolet–visible spectroscopy), NIR spectroscopy (near-infrared) [17], AFM (atomic force microscopy) and TEM (transmission electronic microscopy) [9] but not with 2D NMR (two-dimensional nuclear magnetic resonance) experiments. The 2D NMR techniques have become popular since they efficiently map out 3D interactions within, or sometimes between, molecules [18]. The diffusion ordered spectroscopy (DOSY) technique is a non-invasive powerful technology that has been used for the analysis of a large variety of mixtures [19], as well as for the characterization of aggregates of varying sizes and hence different diffusion coefficients (DC) [20].
The DOSY technique has been referred to as “NMR chromatography” for its ability to “separate” the components of a complex mixture. In a recent application, Marega et al. [21] used 1H-2D DOSY spectroscopy to monitor the functionalization and purification of a carbon nanotube–polyethylene glycol (CNT–PEG) conjugate. There have been numerous publications on the characterization of various bioconjugates using 2D NMR techniques [22], [23]. However, studies related to the characterization of CNT–FA conjugates using 2D NMR spectroscopy have yet to be published.
The aim of this study was to characterize a conjugate formed by single-walled carbon nanotubes (SWCNTs), chitosan and FA by means of the DOSY 2D-NMR technique 1H NMR spectroscopy. The values obtained for the diffusion coefficient confirmed the conjugation of FA to SWCNTs wrapped by the chitosan. The synthesis and utilization of these conjugate systems opens new possibilities for the treatment of infectious diseases and cancer cells [24].
Section snippets
Materials
SWCNTs with diameters ranging from 2 to 5 nm and lengths between 500 and 2000 nm were purchased from Unydim, California. Chitosan with a molecular weight of 5000 Da, folic acid (FA) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) were obtained from Sigma–Aldrich Corp. These and all other chemicals used in this work were of analytical grade.
Solubilization of single-walled carbon nanotubes
Five milligrams of SWCNTs were sonicated for 1 h in 5 mL of a 30% aqueous solution of chitosan. The solution was centrifuged at 2800 rpm for
Results and discussion
The conjugate was prepared by a reaction of FA with SWCNT–chitosan in the presence of EDC (Fig. 3). The EDC is the most popular carbodiimide for conjugating biological substances containing carboxylates and amines [23] and it was used as a crosslinking agent to mediate the formation of an amide between the carboxyl group of the folic acid and the amine group of the chitosan. Hydrolysis by water of the intermediate (EDC–FA) is the major competing reaction cleaving off the activated ester
Conclusions
According to the present study, a two-dimensional diffusion-ordered NMR spectroscopy with presaturation of the solvent (ZGPR) could be successfully employed to monitor the conjugation of folic acid to SWCNTs–chitosan. The obtained diffusion coefficient values revealed that free folic acid diffused more rapidly than its counterpart conjugated to SWCNT, thus proving the efficiency of the synthesis method when it comes to attaching the folic acid molecules around the SWCNT. This is an important
Acknowledgments
The Colombian Administrative Department of Science, Technology and Innovation, COLCIENCIAS (Project 110245921468) and the Danish Agency for Science Technology and Innovation (FSS 09-066053) are gratefully acknowledged for financial support. Doctor Casper H. Clausen who help with the AFM image.
References (32)
- et al.
Carbon nanotubes as nanomedicines: from toxicology to pharmacology
Adv Drug Deliv Rev
(2006) - et al.
Targeted delivery and controlled release of doxorubicin to cancer cells using modified single wall carbon nanotubes
Biomaterials
(2009) Diffusion ordered nuclear magnetic resonance spectroscopy: principles and applications
Prog Nucl Magn Reson Spectrosc
(1999)- et al.
Stability of water-solubles carbodiimide in aqueous solution
Anal Biochem
(1990) - et al.
The use of 2D NMR to study beta-cyclodextrin complexation and debittering of amino acids and peptides
Food Res Int
(2010) - et al.
Characterization of folate-graft-chitosan as a scaffold for nitric oxide release
Int J Biol Macromol
(2008) - et al.
Synthesis and characterization of folate conjugated chitosan and cellular uptake of its nanoparticles in HT-29 cells
Carbohydr Res
(2011) - et al.
Carbon nanotubes in biology and medicine: in vitro and in vivo detection, imaging and drug delivery
Nano Res
(2009) - et al.
Engineering nanomaterial surfaces for biomedical applications
Exp Biol Med
(2009) - Xing ZC, Chang YM, Kang IK. Immobilization of biomolecules on the surface of inorganic nanoparticles for biomedical...
Anticancer drug delivery systems based on noncovalent interactions between carbon nanotubes and linear-dendritic copolymers
Soft Matter
Targeted killing of cancer cells in vivo and in vitro with EGF-directed carbon nanotube-based drug delivery
ACS Nano
Functionalized carbon nanomaterials as nanocarriers for loading and delivery of a poorly water-soluble anticancer drug: a comparative study
Chem Commun
Increased paclitaxel cytotoxicity against cancer cell lines using a novel functionalized carbon nanotube
Int J Nanomed
Carbon nanotubes in cancer theragnosis
Nanomedicine
Carbon nanotubes as multifunctional biological transporters and near-infrared agents for selective cancer cell destruction
Proc Natl Acad Sci USA
Cited by (17)
Preparation and plasticizing mechanism of deep eutectic solvent/lignin plasticized chitosan films
2023, International Journal of Biological MacromoleculesComputational and experimental studies of the interaction between single-walled carbon nanotubes and folic acid
2013, Chemical Physics LettersCitation Excerpt :FA receptors can be direct targets for drug delivery and disease detection [10], which explains the diversity of strategies that folate conjugation can be utilized for. Conventionally, SWCNTs–FA conjugates have been characterized by UV–Vis (ultraviolet–visible spectroscopy), NIR (near-infrared) spectroscopy [6], NMR (nuclear magnetic resonance) spectroscopy [11], AFM (atomic force microscopy) and TEM (transmission electronic microscopy), but they have yet to be investigated with computational methods. However, various studies have been performed using CNTs functionalized with different biomolecules [11–13].
Surface Diffusion of C<inf>1</inf>-C<inf>3</inf> Alcohols on Multiwall Carbon Nanotubes
2023, Adsorption Science and TechnologyCharacterization of the non-covalent conjugate graphene-folic acid using Raman spectroscopy and computational methods
2018, Revista de la Academia Colombiana de Ciencias Exactas, Fisicas y Naturales