18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS MAGNETIC GADOLINIUM-CHITOSAN COMPOSITE NANOPARTICLES CREATED BY RADIOLYTIC SYNTHESIS W. Pasanphan*, L. Chunkoh, S. Choofong Department of Applied Radiation and Isotopes, Faculty of Science, Kasetsart University, Bangkok, Thailand, * Corresponding author (wanvimol.p@ku.ac.th) Keywords : magnetic nanoparticle, gadolinium nanoparticle, chitosan, radiolytic synthesis dependent modifications of structural and magnetic 1 Introduction Magnetic nanoparticles (MNPs) are a major class of properties at nanoscale level [2]. Additionally, nanoscale materials with the potential to nanoscale materials contain higher effective surface revolutionize current clinical diagnostic and areas, lower sedimentation rates, and higher stability therapeutic techniques. The next generation of than bulk one [7]. Radiolytic synthesis has been MNP-based magnetic resonance imaging (MRI) recognized as a promising method to produce metal contrast agents, carriers for drug delivery, including nanoparticles in the present of stabilized polymers. radiosensitizers in neutron capture therapy (NCT) This method has several advantages including [1], is incorporates novel nanocrystalline cores, reduced agglomeration due to immediate coating of coating materials, and functional ligands to improve the particles, absent reducing agents and less the detection and specify delivery of these processing procedures in term of “one pot” nanoparticles. Biomedical application requires the synthesis. In relation of γ -irradiation and the magnetic particles to be stable in water and in synthesis of metallic nanoparticles, silver (Ag) physiological solutions as well as to be coated with a nanoparticles containing chitosan [8] and poly biocompatible polymer [2]. Polymeric coatings (vinylpyrrolidone) (PVP) [9] have been reported. provide a steric barrier to prevent nanoparticle Photochemical reaction using UV-light and agglomeration and avoid opsonization [3]. In microwave have also been proposed for the addition, these coatings provide a means to tailor the preparation of gold (Au) nanoparticles [10, 11]. Li et surface properties of MNPs such as surface charge al. [8] reported that using γ -irradiation to induce Ag and chemical functionality. One of the most widely and Au nanoparticles exhibited much smaller utilized and successful polymer coatings, in terms of particle size and higher concentrated nanoparticles in vivo applications, has been the polysaccharide than the chemical reduction method. Although many dextran [4]. Poly (ethylene glycol) (PEG) has also designs and protocols in preparing Gd nanoparticles been reported as a coating polymer for biomedical have been reported, to our knowledge, there has not applications [5]. Chitosan is a linear polysaccharide been studied about the synthesis of chitosan- composed of randomly distributed β -(1 → 4)-linked stabilized Gd nanoparticles by radiolysis D-glucosamine (deacetylated unit) and N-acetyl-D- methodology using γ -irradiation. Therefore, we glucosamine (acetylated unit). It dictates many study herein, the radiolytic synthesis of magnetic Gd advantageous properties, e.g. biocompatibility, nanoparticles in the present of stabilizing biodegradability, bioactivity, non-toxicity, etc. The biopolymer, i.e. chitosan, using energetic γ -ray excellent bioadhesive properties of chitosan irradiation. encouraged it used for Gd NCT via intratumor injection [6]. Chitosan has been reported as a biopolymer for the preparation of Gd-DTPA 2 Experimental microparticle for NCP by using an emulsion-droplet 2.1 Chemicals coalescence technique [2]. It is important to note that nanoscale Gd particles are Gadolinium chloride (GdCl 3 ·6H 2 O) was purchased also interesting to develop because of size- from Aldrich Company, USA. Chitosan with percent
MAGNETIC GADOLINIUM-CHITOSAN COMPOSITE NANOPARTICLES CREATED BY RADIOLYTIC SYNTHESIS degree of deacetylation (%DD) of 95 (M v = 7 x 10 5 nGd 0 → Gd 2 → …Gd n … → Gd agg (5) Da) was provided from Seafresh Chitosan (Lab) 3.1 Physical Appearance and Particle Formation Company Limited, Thailand. Acetic acid of Gd-CsCNPs (CH 3 COOH) was bought from Carlo Erbar reagent, USA. All chemicals were used without further All Gd (GdCl 3 ·6H 2 O) concentrations in the present of Cs solution of non-irradiation (0 kGy) is purification. transparent without color (Fig. 1(a)-(d)). 2.2 Instruments and Equipment Gamma ray irradiation was carried out in a 60 Co (a) Gammacell 220 irradiator with a dose rate of 7.7 kGy ⋅ h -1 kindly provided by the Office of Atoms for (b) Peace (OAP), Ministry of Science and Technology, Thailand. Ultraviolet and visible (UV-vis) (c) absorption spectra were recorded over a wavelength from 200-600 nm by a Libra S32 spectrophotometer (Biochrom, UK). Transmission electron microscope (d) (TEM) photographs were taken at an accelerating of 100.0 kV by a Hitachi H7650 zero (Hitachi High- Technology, Corporation, Japan). 2.3 Synthesis of Gd-Cs Composite Nanoparticles Fig.1. Appearance of gadolinium solution with the concentraton of (a) 0.02, (b) 0.04, (c) 0.06, and (d) Chitosan (Cs) flakes were dissolved in acetic acid to 0.08 mmole in the present of 0.1% (w/v) chitosan obtain a Cs solution (0.2% w/v). An aqueous solutions (in 1% (v/v) aqueous acetic acid solution), solution of 10 mM GdCl 3 ·6H 2 O was prepared. Cs after γ -ray irradiation with various doses. solution with different concentrations (0.02, 0.05, and 0.1 %w/v) was mixed with different amounts of The γ -rays irradiated Cs solutions containing GdCl 3 ·6H 2 O (0.02, 0.04, 0.06, and 0.08 mmole). The GdCl 3 ·6H 2 O exhibited more intense yellow color mixtures were γ -ray irradiated with the doses of 1-30 kGy using 60 Co Gammacell 220 irradiator to obtain than the non-irradiated sample. The color intensity increased with increasing the γ -ray dose. The intense gadolinium-Cs composite nanoparticles (Gd- CsCNPs) yellow color was obviously seen when the samples were irradiated with the γ -ray doses of 10, 20, and 30 kGy. Since nanometer-sized metal clusters 3 Results and Discussion usually exhibit unique optical properties with their Radiolytic reduction generally involves radiolysis of specific absorption and scattering [13], the formation aqueous solutions to produce the radiolytic species. of Gd-CsCNPs was investigated by UV-vis For water radiolysis in the present of oxygen, the spectrophotometer. The UV-vis spectra (Fig 2(a)) of - , H 3 O + , H • , H 2 , HO • , H 2 O 2 radiolytic species of e aq GdCl 3 ·6H 2 O containing chitosan solution obviously are created as seen in Eq. (1). Here, the reactive reveals two peaks at 260 and 290 nm, which species created by γ -rays induced both reactions, i.e. interpreted as the chemical structure changes of degradation of Cs due to chain scission (Eq. 2 and 3) chitosan after γ -ray irradiation [9]. It have been [12] and reduction of Gd ions (Gd 3+ ) to form cluster explained that the absorption band appeared at 260 of Gd particles (Gd 0 ) (Eq. 4 and 5). nm belonged to the C=O in COOH group and the one at 290 nm corresponded to a terminal carbonyl - , H 3 O + , H • , H 2 , HO • , H 2 O 2 H 2 O 2 → e aq (1) structure formed at C 1 and C 4 after main chain OH • (H • ) + R-H → R • (C 1 -C 6 ) + H 2 O (H 2 ) scission [9]. The γ -ray irradiated GdCl 3 ·6H 2 O (2) precursor in the chitosan solutions also showed little R • (C 1 , C 4 ) • + F 2 • (chain scission) → F 1 (3) surface plasmon absorption bands around 413 and Gd 3+ + 3e aq - → Gd 0 (4) 473 nm (Fig. 2(b)), whereas the non-irradiated
MAGNETIC GADOLINIUM-CHITOSAN COMPOSITE NANOPARTICLES CREATED BY RADIOLYTIC SYNTHESIS 0.5 samples presented no absorption band. This (a) evidence confirms the formation of Gd-CsCNPs in 0.4 Absorbance the GdCl 3 ·6H 2 O containing chitosan solutions after 0.3 γ -ray irradiation. The absorbance implied the particle size and the number of particles as well as the 0.2 formation of Gd aggregates. The absorption bands 0.1 were visibly seen when the γ -ray dose increased 0 4.0 0 5 10 15 20 25 30 35 (a) 30 kGy Dose (kGy) 20 kGy 0.5 3.0 10 kGy (b) Absorbance 0.4 8 kGy Absorbance 0.3 5 kGy 2.0 3 kGy 0.2 1 kGy 0 kGy 0.1 1.0 0 0 5 10 15 20 25 30 35 0.0 Dose (kGy) 200 300 400 500 600 0.5 Wavelength (nm) (c) wavelength (nm) 0.4 Absorbance 0.6 0.3 (b) 0.5 0.2 Absorbance 0.4 0.1 0 0.3 0 5 10 15 20 25 30 35 0.2 Dose (kGy) 0.5 0.1 (d) 0.4 Absorbance 0.0 0.3 350 400 450 500 550 600 0.2 Wavelength (nm) wavelength (nm) Fig. 2. UV-vis absorption spectra of GdCl 3 ·6H 2 O 0.1 solutions (0.06 mmol) in the present of 1% (w/v) chitosan solution (in 1% (v/v) aqueous acetic acid 0 solution) after γ -ray irradiation with various doses. 0 5 10 15 20 25 30 35 Dose (kGy) from 5 kGy to 20 kGy. Increasing the γ -ray dose Fig. 3. Absorbance at maximum wavelength (413 from 10 kGy to 20 kGy, did not increase the nm) of gadolinium solution with different absorbance of resulted Gd-CsNPs, on the contrary, concentrations; (a) 0.02, (b) 0.04, (c) 0.06, and (d) decreased. It was suspected that the particle size 0.08 mmole in the present of chitosan solution (in might increase and the Gd particle possibly 1%(v) aqueous acetic acid solution) with different aggregated when the γ -ray dose increased as high as concentrations; ( ● ) 0.02, ( ■ ) 0.0.5, and ( ▲ ) 0.1% 20 kGy. Fig. 3 clearly indicates the effect of the γ - (w/v). ray doses and the Cs concentration on the 3
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