Showing papers by "David M. Collard published in 2009"

Polymer brushes and self-assembled monolayers: Versatile platforms to control cell adhesion to biomaterials (Review).

Abstract: This review focuses on the surface modification of substrates with self-assembled monolayers (SAMs) and polymer brushes to tailor interactions with biological systems and to thereby enhance their performance in bioapplications. Surface modification of biomedical implants promotes improved biocompatibility and enhanced implant integration with the host. While SAMs of alkanethiols on gold substrates successfully prevent nonspecific protein adsorption in vitro and can further be modified to tether ligands to control in vitro cell adhesion, extracellular matrix assembly, and cellular differentiation, this model system suffers from lack of stability in vivo. To overcome this limitation, highly tuned polymer brushes have been used as more robust coatings on a greater variety of biologically relevant substrates, including titanium, the current orthopedic clinical standard. In order to improve implant-bone integration, the authors modified titanium implants with a robust SAM on which surface-initiated atom transfer radical polymerization was performed, yielding oligo(ethylene glycol) methacrylate brushes. These brushes afforded the ability to tether bioactive ligands, which effectively promoted bone cell differentiation in vitro and supported significantly better in vivo functional implant integration.

Synthesis and Properties of Amphiphilic Poly(1,4-Phenylene Ethynylene)s Bearing Alkyl and Semifluoroalkyl Substituents

Abstract: New poly(1,4-phenylene ethynylenes)s (PPEs), in which each phenylene unit is substituted with both semifluoroalkoxy (−O(CH2)m(CF2)nF) and dodecyloxy (−O(CH2)12H) groups, are amphiphilic by virtue of the self-aggregating properties of the dissimilar side chains. Sonogashira polymerization of 4-iodophenylacetylenes bearing semifluoroalkoxy and alkoxy groups in the 2- and 5-positions, respectively, affords polymers with regular relative placement of the dissimilar side chains (i.e., “regioregular” materials containing only “head-to-tail” diads). This provides a Janus type structure. The assembly of these polymers was studied as a function of the length of the fluoroalkyl segment in the side chain by X-ray diffraction, differential scanning calorimetry, and UV−vis spectroscopy. The properties of these polymers were compared to analogues with random relative placement of side chains (i.e., materials containing a mixture of “head-to-head”, “tail-to-tail” and “head-to-tail” diads), and to a nonfluorinated analog...

Synthetic Approaches to Regioregular Unsymmetrical Dialkoxy-Substituted Poly(1,4-phenylene ethynylene)s

Abstract: Poly(2,5-disubstituted-1,4-phenylene ethynylene)s, PPEs, are generally synthesized by Pd-catalyzed coupling polymerizations of appropriately substituted 1,4-diiodobenzenes and 1,4-diethynylbenzenes...