Self-assembled peptide amphiphile nanofibers have been investigated for their potential use as in vivo scaffolds for tissue engineering and drug delivery applications. We report here the synthesis of magnetic resonance (MR) active peptide amphiphile molecules that self-assemble into spherical and fiber-like nanostructures, enhancing T(1) relaxation time. This new class of MR contrast agents can potentially be used to combine high-resolution three-dimensional MR fate mapping of tissue-engineered scaffolds with targeting of specific cellular receptors.

Current interest in biomaterials for tissue engineering and drug delivery applications have spurred research into self-assembling peptide amphiphiles (PAs). Nanofiber networks formed from self-assembling PAs can be used as biomaterial scaffolds with the advantage of specificity by the incorporation of peptide-epitopes. Imaging the materials noninvasively will give information as to their fate in vivo. We report here the synthesis and in vitro MR images of self-assembling peptide amphiphile contrast agents (PACAs) that form nanofibers. At 400 MHz using a 0.1 mM Gd(III) conjugate of the PA we observed a T(1) three times that of a control gel. The PA derivative was doped into various epitope bearing PA solutions and upon gelling resulted in a homogeneous biomaterial as imaged by MRI.

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Self-consistent field theory is applied to study the ordering behavior of triblock copolymer solutions. A unit cell approximation is used that provides information about individual micelles but does not provide information about the 3-dimensional packing of the micellar aggregates. Information obtained from this approach includes the preferred micellar geometry (spheres, cylinders, or lamellar), the aggregation number, bridging fraction, osmotic pressure, and form factor for a scattering experiment. A variety of general conclusions are obtained with regard to the relationships between these quantities and the polymer concentration, end block solvent quality, and relative molecular weights of the different copolymer blocks.