Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Antibody Targeting of Doxorubicin Loaded Nanoparticles to HER2 Expressing Cancer Cells G. Petek en, F. Gürkan A ırcan, Ufuk Gündüz Middle East Technical University, Biological Sciences Abstract- Doxorubicin was encapsulated into PLGA nanoparticles with single emulsion solvent evaporation method. Trastuzumab was adsorbed on the surface of nanoparticles for targeting to HER2 expressing mammary cancer cells. Delivery of anti-cancer drugs using biocompatible nanoparticles are likely to provide protection from degradation, better adsorption, reduced frequency of administration, and improved therapeutic index. The next generation of drug delivery systems includes surface modified nanoparticles in order to get a selective drug carrier system. Targeting can be achieved via antibodies against proteins over-expressed on cell membrane. Between 25% and 30% of breast cancers overexpress human epidermal growth factor receptor 2 (HER2-neu), which is associated with poorer prognosis and resistance to treatment [1]. Trastuzumab is a humanized monoclonal antibody that is currently used as a treatment for the cancer type that expresses HER2 receptor. In this study, anti-cancer drug doxorubicin was loaded into Poly (lactic-co-glycolic acid) (PLGA) nanoparticles. Active targeting of nanoparticles via adsorption of trastuzumab on their surface was aimed. BT- 474 cell line which over-express HER2 receptor was used. Anticancer drug doxorubicin was encapsulated by PLGA polymer by using a modified single emulsion solvent evaporation technique [2]. Doxorubicin was solubilized in chloroform containing triethylamin. PLGA was dissolved in this solution. Solution was than added drop wise into the aqueous phase containing 2% PVA under magnetic stirring at. Chloroform was evaporated. Hardened nanoparticles were obtained by centrifugation and washed with distilled water. Adsorption of trastuzumab was achieved by 24 hours incubation of antibody with doxorubicin loaded nanoparticles at different pH values with different antibody nanoparticle ratios. The incubations were done in PBS at pH values of 5.0, 7.0 and 9.0 with the antibody nanoparticle ratios of 1:1 and 2:1. Amount of the antibody adsorbed on the nanoparticles was determined by protein assay. Incubation at pH 5.0 and with the nanoparticle antibody ratio of 1:2, adsorption of antibodies on nanoparticles’ surface was at maximum. Surface analyses of unmodified doxorubicin loaded and trastuzumab adsorbed nanoparticles were done. Scanning electron microscopy images showed that trastuzumab adsorption changed the structure of nanoparticles (Figure 1). During incubation with antibody, nanoparticles were swelled and their surface became smoother. Cellular targeting and uptake of unmodified and antibody coated nanoparticles were investigated with BT-474 cell culture. Equal amounts of unmodified and coated nanoparticles were added to the cells and incubated for 4 hours. The cells were then washed to remove nanoparticles not internalized by the cells or bound to the cell surfaces. Fluorescence microscopy was then performed. It was observed that there were significantly higher amounts of nanoparticles around and inside the BT-474 cells when the nanoparticles were covered with trastuzumab antibody (Figure 2). a) b) Figure 2. BT-474 cell line incubated with a) unmodified nanoparticles b) trastuzumab adsorbed nanoparticles Coated nanoparticles were more likely to be bound to the cells than non-coated nanoparticles. Results indicated increased interaction of nanoparticles with the cells when they are coated with antibody. Increased interactions may be helpful in internalization of the drug and increasing potency of the therapy. While nanoparticles are known to increase the bioavailability of doxorubicin, trastuzumab adsorption can target the doxorubicin loaded nanoparticles to HER2 expressing cell. Further research is in progress in order to indicate specific targeting of coated nanoparticles to HER2 expressing BT-474 cells. ufukg@metu.edu.tr [1] Slamon DJ, Godolphin W, Jones LA, et al. Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer. Science 1989;244:707-712. a) b) Figure 1. Scanning electron micrograph of a) unmodified nanoparticles b) trastuzumab adsorbed nanoparticles [2] X.S. Wu, Preparation, characterization, and drug delivery applications of microspheres based on biodegradable lactic/glycolic acid polymers. In: WiseEncyclopedic handbook of biomaterials and bioengineering, Marcel Dekker, New York (1995), pp. 1151–1200. 6th Nanoscience and Nanotechnology Conference, zmir, 2010 252
Poster Session, Tuesday, June 15 Theme A1 - B702 Nanoporous Zeolites with Antimicrobial Activity 1 2 , Selami Demirci 2 , Nurcan Baç 1 * 1 2 Genetics and Bioengineering Department Yeditepe University, Abstract-Antibacterial and antimicrobial activity of silver, copper and zinc zeolites are studied using Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Staphylococcus aureus. Results indicated that distinct microbial growth inhibition zones are clearly visible. Zeolites are nanoporous crystalline alu minosilicates with a framework structure that consists of three dimensional networks of SiO 4 and AlO 4 tetrahedra linked by shared oxygen atoms, and contain ions like Na + or K + . This is a highly ordered special molecular structure composed of uniform nanoscale channels and cavities, unlike their ordinary powdery appearance. It is well known that some kind of metallic particle, such as silver, copper and zinc, have antibacterial capabilities. In order to facilitate the particle handling and to reduce health risks, particles in inorganic matrix are being studied as antibacterial agents. These materials present high antibacterial activity, low toxicity, chemical stability, long lasting action period and thermal resistance versus organic antibacterial agents. Due to the stability of these particles supported on a matrix, they can be used in paint or polymers as a bactericide agent for coat hospital equipment, as well as fittings for public places, public transport, paints, toys and kitchen, school and hospital utensils. In the present work, zeolites are ion exchanged with a metal ion such as Ag, Zn or Cu, they show antimicrobial effect [1, 2]. There are many types of zeolites like Zeolite A, Zeolite X, Zeo lite Y etc. In this work, Zeolites A and X are synthesized using sodium aluminate and colloidal silica (Ludox) or sodium metasilicate under hydrothermal conditions Compositions of ingredients vary according to the type of zeolite [3,4]. The synthesis gel is vigorously shaken for the homogenization, and is placed into high density polyethylene (HDPE) bottles and processed in a convection oven at 90 ºC for zeolites A and X.. After a predetermined time, the sample bottles are removed and the zeolite product is filtered and dried. Preliminary characterization is done by an optical microscope followed by SEM (Scanning Electron Microscope) images. The zeolites synthesized in sodium form are then ion exchanged with silver copper and zinc at different concentrations for antimicrobial activity [1, 3]. The antimicrobial activity starts as soon as silver, copper and zinc ions are released from the zeolite crystals into the system containing microorganisms. In this study we examined the antimicrobial activity of silver zeolites against three bacterial species Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus etc., and various yeast and fungus. Microbial growth inhibition zones were evaluated for Escherichia coli, Staphylococcus aureus., some other bacteria and for yeasts at 37 °C, and for Pseudomonas aeruginosa at 28 °C, and for fungus at room temperature. Figure 1. Scanning electron micrograph of Ag + -A Results with Zeolite A, X show that silver, copper, or zinc zeolites inhibit microbial growth. *Corresponding author: nbac@yeditepe.edu.tr [1] Hagiwara, Z., Hoshino, S., Ishino, H., Noara, S., Tagawa, K., Yamanaka, K., U.S. Patent, 4,775,585, 1988. [2] Matsumura, Y., Yoshikata, K., Kunisaki, S., Tsuchido, T., Applied and Environmental Microbiology, 69, 7, 4278-4281 (2003) [3] Kamisoglu, K., Aksoy ,E. A., Akata, B., Hasirci, N., Bac, N.,Jour. Appl. Polymer Sci. 10 2854-2861 (2008) [4] Warzywoda J., Bac, N., Jansen, J. C., Sacco, A., Jour. Crystal Growth 220 140-149 (2000) 6th Nanoscience and Nanotechnology Conference, zmir, 2010 253
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