Peptide amphiphile molecules (PAs) developed in our laboratory self‐assemble from aqueous media into three‐dimensional networks of bioactive nanofibers. Multiple non‐covalent interactions promote assembly of the supramolecular nanofibers and ultimately determine the bulk physical properties of the macroscopic gels. In this study, we use oscillatory rheology, Fourier‐transform infrared spectroscopy, and circular‐dichroism spectroscopy to better understand the assembly mechanism of a typical PA molecule known as PA‐1. Self‐assembly of PA‐1 is triggered by counterion screening and stabilized by van der Waals and hydrophobic forces, ionic bridging, and coordination and hydrogen bonding. The concentration, electronic structure, and hydration of counterions significantly influence self‐assembly and gel mechanical properties.

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Surface modification enables the creation of bioactive implants using traditional material substrates without altering the mechanical properties of the bulk material. For applications such as bone plates and stents, it is desirable to modify the surface of metal alloy substrates to facilitate cellular attachment, proliferation, and possibly differentiation. In this work we present a general strategy for altering the surface chemistry of nickel-titanium shape memory alloy (NiTi) in order to covalently attach self-assembled peptide amphiphile (PA) nanofibers with bioactive functions. Bioactivity in the systems studied here includes biological adhesion and proliferation of osteoblast and endothelial cell types. The optimized surface treatment creates a uniform TiO 2 layer with low levels of Ni on the NiTi surface, which is subsequently covered with an aminopropylsilane coating using a novel, lower temperature vapor deposition method. This method produces an aminated surface suitable for covalent attachment of PA molecules containing terminal carboxylic acid groups. The functionalized NiTi surfaces have been characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and atomic force microscopy (AFM). These techniques offer evidence that the treated metal surfaces consist primarily of TiO 2 with very little Ni, and also confirm the presence of the aminopropylsilane overlayer. Self-assembled PA nanofibers presenting the biological peptide adhesion sequence Arg-Gly-Asp-Ser are capable of covalently anchoring to the treated substrate, as demonstrated by spectrofluorimetry and AFM. Cell culture and scanning electron microscopy (SEM) demonstrate cellular adhesion, spreading, and proliferation on these functionalized metal surfaces. Furthermore, these experiments demonstrate that covalent attachment is crucial for creating robust PA nanofiber coatings, leading to confluent cell monolayers.

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“Intelligent” organosilica sol–gels that show fast dynamic response to temperature, pH, and electric fields are presented. A bis‐(propyl)ethylenediamine bridge is responsible for a change of water affinity under environmental stimuli, resulting in water expulsion or uptake by the polymeric network. The Figure shows the tips of a tweezer‐like sol–gel device that opens and closes upon pH fluctuation.

Biological self-assembly of superparamagnetic iron-oxo cores in ferritin illustrates a unique example of matrix-assisted formation of magnetic nanomaterials 1 and artificial analogues of ferritin still remain an elusive goal. In this context, synthesis of iron oxide nanoparticles has been attempted by different methods. [2][3][4][5][6][7][8] How-* To whom correspondence should be addressed.

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A novel silica sol‐gel that swells or shrinks rapidly by changing its hydration state upon temperature variation is described. The swelling–deswelling (see Figure) is reversible and the kinetics of the bulk transition are fast. The effects of preparation technique and structural variation on the thermal shrinkage properties are discussed.