Preparation of magnetic drug-loaded PLGA nanospheres as biodegradable magneto-responsive drug carriers Mohsen Ashjari1, Sepideh Khoee *,2, Ali Reza Mahdavian *,1 1 Polymer Science Department, Iran Polymer and Petrochemical Institute, Tehran, Iran 2 Polymer Chemistry Department, School of Science, University of Tehran, Tehran, Iran E-Mail: A.Mahdavian@ippi.ac.ir Abstract Experimental part (continued) Results (continued) The aim of this study is preparation of drug-loaded biodegradable magnetic PLGA nanospheres made by emulsification - evaporation method. The encapsulation procedure involves the formation of oil-in-water emulsion in which consists of an oil phase containing magnetite nanoparticles in an aqueous solution of drug, emulsification in an oil phase containing PLGA and a stabilizer and lastly emulsification double emulsion in an aqueous PVA solution lead to formation final multiple emulsion. The mean diameters of the magnetic PLGA nanospheres in this study were smaller than the critical size required for the recognition by the reticuloendothelial system (RES). The morphology and size distributions of the prepared magnetic PLGA nanospheres were investigated by SEM. The micrographs showed that the magnetic nanospheres were almost spherical in shape and the mean diameter within the range of 100-300 nm with broad size distributions. The VSM results showed magnetite content 35 %wt and good magnetic responsivity. The VSM measurements showed superparamagnetism of prepared magnetic nanospheres. This study suggests that the emulsification - evaporation process is a prospective technique to prepare biodegradable magnetic nanospheres containing water-soluble sensitive agents. Then, this double emulsion was poured into an aqueous PVA solution and the mixture was ultrasonicated. The resulting emulsions were diluted in PVA solution under mechanical stirring and the DCM was eliminated by solvent evaporation. The resulting magnetic PLGA nanospheres were cleaned by repeating procedure of centrifuging and resuspending in distilled water for three times and then were collected by a magnet. Finally, the obtained nanospheres were dried by lyophilization (freeze-drying) and stored at 4°C. The presence of PLGA causes such a decrease in Ms of the magnetic PLGA nanospheres relative to the pristine magnetite nanoparticles. On the other hand, it is well known that magnetic particles less than 30nm will demonstrate the characteristic of superparamagnetism, which can be verified by the magnetization curve. The remanence (Mr) and coercivity (Hc) for magnetic PLGA nanospheres in Figure 2 were close to zero, illustrating the superparamagnetic characteristic of the resulting nanospheres. As shown in Figure 2, it could be observed that both types of materials exhibit similar overall superparamagnetic behavior. Results The FTIR spectrum of freeze-dried magnetic PLGA nanosphere was obtained by the KBr pellet method. The FTIR spectrum shows the presence of all bands of the PLGA (ester carbonyl C=O stretch band at 1756 cm-1, strong), 1171 & 1090 (C-O-C in ester group, strong), 2850–3010, 1360–1460 (saturated C-H, including CH3, CH2, and CH), 3500 (terminal OH, weak), a peak at 1660 cm-1 that is attributed to 5-FU and a peak at 580 cm-1 that represents the existence of magnetite nanoparticles. Scanning electron microscopy (SEM) is powerful tools to characterize size, morphology and structure of magnetic PLGA nanospheres. The prepared samples were observed by SEM to obtain information about the morphology and surface characterization (shape, distribution, aggregation) of the magnetite PLGA nanospheres. The SEM micrographs clearly show that magnetic PLGA nanospheres are spherical in shape (Figure 1). The surface was primarily smooth, although some roughness could be identified in certain areas of some nanospheres. Introduction In order to avoid the inconvenient surgical insertion of large implants, injectable biodegradable and biocompatible polymeric particles (microspheres, microcapsules, nanocapsules and nanospheres) could be employed for controlled-release dosage forms [1]. Intravenous (i.v.) administration of drugs leads to systemic distribution throughout the body resulting in undesirable side effects and as a consequence only a suboptimal dosage of drugs reaches the desired target site. Magnetic nanodevice for targeted delivery approach involves administration of a therapeutic agent bound or encapsulated in a magnetic carrier [2]. These magnetic nanodevices that have unique surface properties permitting maximum biocompatibility and biodegradability could be suitable for drug delivery vehicles. Such systems can be driven and held in the specific area for a desired period of time by applying external localized magnetic fields. Additional advantages of this drug delivery by magnetic targeting include the maintenance of drug levels within a desired range by reducing their systemic distribution and the possibility of administering lower but more accurately targeted doses of the cytotoxic compounds used in these treatments [3, 4]. PLGA is an FDA approved polymer for certain clinical uses which have been utilized widely in drug delivering system as an effective encapsulating material. The existence of a separate encapsulated aqueous phase allows the possibility of protecting biologically active agent and possibly also of controlling their release. Figure 2: Magnetization vs. applied magnetic field for magnetite nanoparticles and magnetic PLGA nanospheres. Conclusion Magnetic drug targeting employing nanospheres as carriers is a promising cancer treatment avoiding side effects of conventional chemotherapy. This study suggests that the modified multiple emulsion - solvent evaporation process is a prospective technique to prepare biodegradable magnetic nanospheres containing water-soluble sensitive agents. As a drug-release carrier, PLGA is expected to provide a good release of drugs. The control of the structure of such copolymers would allow the proper selection in the rates of both the drug release and the biodegradation of microspheres or nanospheres. Acknowledgements The financial support of Iran National Science Foundation is greatly acknowledged. Figure 1: F SEM micrograph of the magnetic PLGA nanospheres. References To investigate the magnetic properties of magnetite nanoparticles and drug-loaded magnetic PLGA nanospheres, VSM measurement was used. Figure 2 shows the magnetization curve of the prepared magnetite nanoparticles and drug-loaded magnetic PLGA nanospheres. The saturation magnetization (Ms) of the pristine magnetite nanoparticles was found to be 38.2 emu/g and magnetic PLGA nanospheres approximately was 13.7 emu/g, revealing an approximate magnetite content 36 wt%. Experimental part [1] R. Jalil, J.R. Nixon: J. Microencapsulation, 7 (1990) 297. [2] S.H. Hu, K.T. Kuo, W.L. Tung, D.M. Liu, S.Y. Chen, Adv. Func. Mater. 19, (2009) 3396. [3] S. Goodwin, C. Peterson, C. Hoh, C. Bittner, J. Magn. Magn. Mater. 194, (1999) 132. In brief, magnetite nanoparticles were dispersed in DCM. Next, the inner aqueous solution was prepared by dissolving 5-flourouracil as a hydrophilic drug in water. The dispersion of magnetite was emulsified in an organic solution of the PLGA by ultrasonication in an ice bath to obtain an oil-in-water-in-oil double emulsion.