@conference{
author = "Krajišnik, Danina and Čalija, Bojan and Djekić, Ljiljana and Dobričić, Vladimir and Daković, Aleksandra and Marković, Marija and Milić, Jela",
year = "2018",
abstract = "Introduction
Interactions of cationic surfactants with natural zeolites have been extensively studied since they proved to be excellent adsorbents for various drug molecules contributing their functionality as drug carriers. Investigations related to nonsteroidal anti-inflammatory drugs (NSAIDs) are particularly interesting, since they are one of the most frequently used medications (Krajišnik et al., 2017). Sorption and release of ibuprofen (IBU) (a representative of NSAIDs; practically insoluble in water) by modified clinoptilolitic zeolitic tuff, in two step preparation procedure, was previously investigated (Krajišnik et al., 2015). According to this procedure, in the first step surfactant modified zeolites were prepared and then in the second step drug-modified zeolite composites were obtained by adsorption of IBU on modified zeolites.
The aim of this work was to carry out a study of direct method of drug-modified zeolite composites preparation and the influence of cationic surfactant:drug molar ratio on adsorption properties of clinoptilolitic zeolitic tuff.
Experimental Methods
In experiments, the initial clinoptilolitic zeolitic tuff from Zlatokop deposit (Serbia) (Krajišnik et al., 2011) was treated with solutions comprising surfactanthexadecyltrimethylammonium bromide (HB) in amounts equivalent to 100, 200 and 300% of its external cation exchange capacity (ECEC). In surfactant solutions (prepared at 40 C) IBU was solubilized at the same drug:surfactant molar ratio. The 10% aqueous suspensions were mixed on a high-speed disperser at 6000 rpm for 10 min. After mixing, the suspensions were filtered and the filtrates were collected for the drug assay by HPLC analysis. The obtained drug/modified zeolites composites, prepared by direct method, were denoted as ZHB-10 IBU/DM, ZHB-20 IBU/DM and ZHB-30 IBU/DM.
The average droplet size (Z-ave) and polydispersity index (PdI) in the starting drug/surfactant solutions were determined by photon correlation spectroscopy (PCS) using a ZetasizerNano ZS90 (Malvern Instruments, Malvern, UK). The zeta potentials of the starting zeolite and the prepared samples (drug/modified zeolites composites) were performed on the same apparatus. FT-IR spectra of the prepared samples and their individual components were recorded using a Nicolet iS50 spectrometer (Thermo Scientific, USA) in the range of 4000–400 cm−1 at a resolution of 2 cm−1.
Results and Discussion
In the starting drug/surfactant solutions, both IBU and HB were used at equimolar concentrations of 0.011 M, 0.022 M and 0.033 M for ZHB-10 IBU/DM, ZHB-20 IBU/DM and ZHB-30 IBU/DM, respectively. The HB concentration in all solutions was higher than its critical micelle concentration (cmc 0.92 mM at 20-25 °C). Instead of an intensive peak pattern associated with HB micelles, a group of very low intensity peaks was observed in a wider size range. The observed changes can be interpreted by disturbing the structure of the micelles under the conditions of agitation and temperature during the preparation of the starting solutions, and the formation of IBU complexes with individual HB molecules (Bunton et al., 1981), as well as their associates.The changes in zeta-potential of clinoptilolitic zeolitic tuff (ZVB) (Fig. 1a) were more pronounced for the samples with higher HB content compared with the sample ZHB-10 IBU/DM. Since the adsorbed amount of IBU on the prepared composites was lower for ZHB-10 IBU/DM ( 20 mg/g) and approximately the same for ZHB-20 IBU/DM and ZHB-30 IBU/DM ( 40 mg/g), increasing zeta potentials probably correspond to different surfactant coverage and organization at the mineral surface.
The bands in FT-IR spectrum of ZHB-30 IBU/DM (Fig. 1b) at 3618, 3420 and 1640 cm−1 are clinoptilolite characteristic bands related to acidic hydroxyls SiO(H)Al, hydrogen-bonding hydroxyl groups, and bending vibration of absorbed water, respectively (Korkuna et al., 2006). Compared to the FT-IR spectrum of ZVB the following bands were observed: the CH2 symmetric and asymmetric stretching vibrations of alkyl chain at 2919 and 2850 cm−1 and C–H scissoring vibrations of CH3–N+ moiety with peak at 1463 cm−1, which evidence the presence of HB (Sui et al., 2006). A weak band at 1384 cm−1 implies the presence of anionic form of adsorbed IBU (Krajišnik et al., 2015). The presented results of drug uptake by surfactant/zeolite composites revealed that drug adsorption from IBU/HB solutions could be successfully performed by the direct method of preparation, while cationic surfactant:drug molar ratio had influence on adsorbed amounts and organization of molecules on the zeolitic surface. Further investigations of pharmaceutical technical characteristics and drug release from the obtained composites would reveal their possible pharmaceutical application.
Acknowledgment
This work was realized within the framework of the projects TR 34031 and OI 172018 supported by the Ministry of Education, Science and Technological Development of Republic of Serbia.",
publisher = "Lublin : Lublin University of Technology",
journal = "ZEOLITE 2018 - 10th International Conference on the Occurrence, Properties and Utilization of Natural Zeolites",
title = "Ibuprofen adsorption on a clinoptilolitic zeolitic tuff modified with cationic surfactant: direct method of composites preparation",
pages = "192-191"
}
