Photonic crystals in biology - NanoTR-VI

PPoster Session, Thursday, June 17Theme F686 - N1123Assembly of Peptide Coated Gold Nanoparticles on Surfaces1111Ismail SayinP P, Kemal KeserogluP P, Mehmet KahramanP Pand UMustafa CulhaUP P*1PDepartment of Genetics and Bioengineering, Yeditepe University, Istanbul 34755, TurkeyAbstract-The assembly of nanoparticles into the desired organizations and patterns is critically important for construction of higher structuresusing nanoparticles as building block. In this regard, we designed charged peptides that can stably bind the gold nanoparticles (AuNPs) to alterthe surface charge properties. Then, we investigate how the surface charge of the nanoparticles can influence the assembly of the AuNPs onsurfaces with different polarity from a drying droplet of their colloidal suspension.Self assembly of the biomolecule modified nanoparticles isextensively studied in recent years [1,2]. The main reasonbehind the use of biomolecule-modified nanoparticles is toutilize the existing weak interactions among biomolecules andbio-macromolecules such as hydrogen bonds, van der Waals,dipol-dipol and ionic interactions to control the nanoparticleassembly. The peptides are one of the target molecules thatare used in these studies because of their easy design andmanipulation of their charge and polarity properties comingfrom their side chains. One of the major factors influencingthe stabilization of the AuNPs in the aqueous environment isthe zeta potential (). Nearly -/+ 30 mV is needed for thestability of the nanoparticles and below these potentials thenanoparticles start to aggregate [3]. The charged peptides canbe used to stabilize the gold nanoparticles [4].In this work, we investigated the assembly of chargedpeptide modified AuNPs and their assembly after addition ofthe oppositely charged peptides into the modified goldcolloidal suspension. The rational behind this reason was tolook for any relationship between the surface chargeproperties of the nanoparticles and its affect on the assemblyof the nanoparticles in a drying droplet. The additions of theoppositely charged peptides cause surface potential changewhich is thought to influence the formation of uniquestructures. The peptides used in this regard are given inTable 1.Table 1. Peptides that were used in the experiments.Purpose Code peptide sequencesOverallChargeP1 Cys-Ser-Glu (-)Modificationof AuNPs P16 Cys-Ser-Glu-Asp-Ser-Asp-Glu-Ser Asp-Ser-Glu-Ser-Asp-Ser-Glu(-)Aggregation P3 Lys-Lys (+)Initiation P11 Lys-Arg-Arg-Lys (+)In this study, we first investigated the self assembledstructures occurred in suspension using SAXS and at the solidliquid interface with SEM and AFM. A correlation withsurface charge properties of the modified AuNPs andassembly behavior in suspension and at liquid-solid interfacewas investigated. The influence of the hydrophobic andhydrophilic surfaces on the behavior of the AuNPs was alsoinvestigated. It was observed that, on the hydrophilic surfaces,the modified AuNPs formed larger aggregates with thedecreasing value of the surface potential and the structures canbe seen all over the surface of the droplet area (Figure 1 andTable 2). On the hydrophobic surfaces, again the aggregatesizes were inversely proportional to the surface potential. Theaggregates were not spread all over the droplet area but theyformed at the near center area of the droplet.A)Figure 1. Aggregates/assemblies of modified AuNPs with differentzeta potentials on hydrophilic surfaces from a drying droplet.A)AuP1 + 1 L P11 B) AuP1 + 5 L P11Table 2. Zeta potential change after addition of the oppositelycharged peptides.AuNP-P11 L P11(+)5 L P11(+)In summary, the preliminary data shows that the structuresformed in the drying droplet are related to the zeta potentialson the AuNPs residing in colloidal suspension. The assemblyof the peptide modified gold nanoparticles differs with respectto the surface bound peptides and addition of the oppositelycharged peptides. The assembly of the nanopartices is alsoaffected from the polarity of the surface. The long term goal ofthis study is to find a way to nanoparticles by modifying thesurface charge properties of nanoparticles and the studies areconducted in this direction. This work was supported byTUBITAK under Grant No. 108T605.*Corresponding author: HTmculha@yeditepe.edu.trT10 L P11(+)AuNP-P1 (-) -30 mV -20 mV -10 mV -7 mV[1] Varpness, Z.; Peters, J. W.; Young, M.; Douglas, T. Nano Lett.2005, 5, 2306-2309.[2] Kramer, R. M.; Sowards, L. A.; Pender, M. A.; Stone, M. O.;Naik, R. R. Langmuir 2005, 21, 8466-8470.[3] J.A. Tullman, W.F. Finney, Y.-J. Lin, S.W. Bishnoi, Plasmonics 2(2007) 119.[4] R. L vy, ChemBioChem 2006, 7, 1141B)2 μm 2 μm6th Nanoscience and Nanotechnology Conference, zmir, 2010 645