We herein present a novel platform of well-controlled ordered and disordered nanopatterns positioned with a cyclic peptide of arginine-glycine-aspartic acid (RGD) on a bioinert poly(ethylene glycol) background, to study whether the nanoscopic order of spatial patterning of the integrinspecific ligands influences osteoblast adhesion. This is the first time that the nanoscale order of RGD ligand patterns was varied quantitatively, and tested for its impact on the adhesion of tissue cells. Our findings reveal that integrin clustering and such adhesion induced by RGD ligands is dependent on the local order of ligand arrangement on a substrate when the global average ligand spacing is larger than 70 nm; i.e., cell adhesion is "turned off" by RGD nanopattern order and "turned on" by the RGD nanopattern disorder if operating at this range of inter-ligand spacing.Integrin plays a central role in the formation of focal adhesions (FAs), which anchor cells to the extracellular matrix (ECM). 1 High-affinity binding of the integrin transmembrane proteins to ECM ligands has been extensively exploited for tailoring artificial synthetic ECM systems. 2 Thus far, it has been reported that cell responses to the synthetic ECM depend to a large extent on multiple substrate features, such as its chemical composition, 3-6 geometry and topographical features, 7 ligand organization, 8,9 and even substrate stiffness. 10,11 In particular, the spatial organization of the integrin-specific peptide sequence of arginineglycine-aspartic acid (RGD) on non-fouling substrates has attracted much attention. This sequence, contained in many ECM proteins, can be recognized by all five aV integrins (αVβ1, αVβ3, αVβ5, αVβ6, αVβ8), two β1 integrins (α5β1, α8β1) and αIIbβ3. 12 Once ligated, the integrin receptors link the ECM to the cytoskeleton and integrate intracellular and extracellular events. Furthermore, it is known that cellular behaviors such as adhesion, migration, proliferation and differentiation, are quite sensitive to the bioactivity, tether length, interspacing and density of surface RGD ligands in artificial ECM materials. 13-21Recent developments in nanotechnology have given access to the nanoscale organization of RGD ligands in both inorganic and polymeric substrates mimicking ECMs. Research concerning randomly dispersed RGD ligands grafted onto polymeric materials suggested that *Corresponding authors: E-mail: E-mail: Spatz@mf.mpg.de (J.P. Spatz); E-mail: jdding1@fudan.edu.cn (J. Ding). Supporting Information Available: A detailed description of the experimental protocols for sample preparation and characterization is available free of charge via the Internet at http://pubs.acs.org. Nevertheless, there has been no report to date of studies comparing cellular responses to nanostructured surfaces characterized by ordered or disordered organization of biomolecules such as RGD ligands. Herein, we chose to examine this critical issue in cell-nanomaterial interactions by exploring osteoblast adhesion regulated by the nanoscale organ...

Noble-metal nanoparticles (Au, Ag, Pt, Pd) are of substantial interest for various scientific and technical applications [1] because they exhibit a number of unique optical, [2][3][4] electronic, [5,6] and catalytic [7,8] characteristics compared to bulk materials. It is important to realize that nearly all of these properties are a function of the particle size and shape at the nanometer scale.The size-dependent interaction of light with small particles, referred to as localized surface-plasmon resonance (LSPR), [9] and coupled-plasmon resonance [10] enables them to be used for various applications such as biosensors [11] and molecular rulers. [12] Spectroscopic techniques such as surface enhancedRaman spectroscopy (SERS), [13,14] nonlinear scattering experiments, for example, second-harmonic generation (SHG), [15,16] and time-resolved methods [17][18][19] have been developed, each of them sensitive to the electronic properties of the metallic nanoparticles and their interaction with electromagnetic waves as a function of the particle diameter and particle-particle spacing. [20] However, the generation of nanostructures with feature sizes smaller than 100 nm relies on conventional lithographic techniques such as electron-beam (e-beam), X-ray, and photolithography. [21] All these methods, summarized as top-down technology, are rather complicated, timeconsuming, and require expensive technical equipment. An alternative route is offered by the so called bottom-up technology. Scanning probe microscopy (SPM) techniques like ''dip-pen'' nanolithography [22] are capable of preparing nanostructures with feature sizes down to 10 nm with excellent spatial resolution. Their disadvantage is low throughput, as a consequence of being a serial process. In contrast, microcontact printing [23] enables a rapid and parallel fabrication of chemical and topological micro-and nanostructures. Here the resolution is limited by the mechanical properties of the stamp and the contact stability between the stamp and the substrate.Lithographic techniques based on self-assembly are particularly attractive since they offer the large-scale fabrication of feature sizes down to a few nanometers with predefined molecular and colloidal properties. Nanosphere lithography [24][25][26] has been reported to be capable of producing highly ordered metallic nanoparticle arrays with well-defined size and shape based on pure self-assembly. Crystalline monolayers of self-assembled polystyrene spheres act as a template for the vapor deposition of metals such as gold or silver. The in-plane diameter, shape, and spacing between the metal clusters are related to the diameter of the colloidal spheres. As a consequence, it is not possible to control the structural parameters independently from each other, which is limiting the general applicability. Therefore a nanofabrication technique that allows a fast, substrate-independent, and inexpensive sample processing with the possibility to independently adjust the structural parameters, such as size and spacing, at a...

The development of multilayered thin film assemblies containing (bio)molecules is driven by the need to miniaturize sensors, reactors, and biochips. Viral nanoparticles (VNPs) have become popular nanobuilding blocks for material fabrication, and our research has focused on the well-characterized plant virus Cowpea mosaic virus (CPMV). In a previous study, we have reported the construction of multilayer VNP assemblies. Here we extend these studies by providing further details on the formation and properties of arrays that are made by the alternating deposition of biotinylated CPMV particles and streptavidin molecules. Array formation was followed in real time by a quartz crystal microbalance with dissipation monitoring. Our data provide indications that multiple interactions between biotin and streptavidin not only promote the assembly of a multilayered structure but also generate cross-links within each layer of CPMV particles. The degree of intralayer and interlayer cross-linking and hence the mechanical properties and order of the array can be modulated by the grafting density and spacer length of the biotin moieties on the CPMV particles.