Surface modification and molecular cluster modelling of γ-Fe₂O₃ nanoparticles as a potential carrier for drug delivery
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Date
2013-07-04
Authors
Wijekoon, C. J. K.
Randiligamage, S.
Weerasooriya, R.
Bandara, W. M. A. T.
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Peradeniya
Abstract
Magnetic drug delivery is based on the fact that a drug can be encapsulated onto a magnetic nano core shell. When the magnetic carrier is intravenously administered the accumulation takes place within the areas to which the external magnetic field is applied. In this research the suitability of casein - γ-Fe₂O₃ core shell nanoparticles as a magnetic drug carrier under controlled fashion was determined.
Unmodified γ-Fe₂O₃ particles are unstable in physiological fluids tending to agglomerate and precipitate quickly. A surface coating of casein was used to prevent this. Casein also provides chemical handles for the conjugation of drug molecules. It also enhances the bio compatibility and controls the hydro dynamic radius of the core shell.
Diffuse Reflection Infrared spectroscopy (DRIFT) data were used to interpret the binding of casein onto γ-Fe₂O₃. To effectively analyze the experimentally found data, molecular modelling calculations were done for γ-Fe₂O₃ and surface modified γ-Fe₂O₃ with Gaussian 03 code. All the models were built with Gaussview. Optimized molecular structures were determined by searching in the potential energy surface for minima with respect to each atomic coordination using Density Function Theory (DFT) calculations under DFT hybrid B3LYP function with 6-31G (d,p) basic set. The γ-Fe₂O₃ nanoparticles were modelled using Fe₆(OH)₁₈(H₂O)₆ ring cluster. The adsorption of casein onto γ-Fe₂O₃ surface sites was also modelled using the derived cluster and the vibrational frequencies for the clusters were calculated.
Combination of the experimental and calculated data showed that casein binds to γ-Fe₂O₃ through the carboxylate group (COO⁻). COO⁻ shows two asymmetric vibrations (AS) (1610-1550 cm⁻¹) and one symmetric vibration (S) (1420-1300 cm⁻¹). By calculating AS-S (Δ) the binding modes of the COO⁻ group was determined. If Δ>200 cm⁻¹ monodentate, 140<Δ<200 cm⁻¹ bridging and Δ<140 cm⁻¹ bidentate. The binding modes changed with the pH. At pH 3 and 5 both bridging and bidentate bindings were observed. At pH 10 and 13 only monodentate binding was observed and at pH 7 monodentate and bidentate bindings were observed.
Hence the COO⁻ group of casein binds very effectively to γ-Fe₂O₃ in acidic conditions. Thus the surface modification of γ-Fe₂O₃ can be conveniently carried out using casein.
Description
Keywords
Chemistry , Drug delivery , Nanoparticles , Surface modification , Molecular cluster
Citation
Peradeniya University Research Sessions PURSE - 2012, Book of Abstracts, University of Peradeniya, Sri Lanka, Vol. 17, July. 4. 2012 pp.186