excitation is believed to involve the = 0 -*• 1 transition and thus is a measure of the fundamental vibration for the ion.3 Although ion-matrix electronic interactions are on the order of 1 eV,22 differences in interactions between ground and excited vibrational states are probably small, and vibrational spectra of matrix-isolated molecular ions are believed to be representative of the gaseous ion. The fact that argon-krypton matrix differences are small (5-7 cm"1) for such ions as CF3+ and CHBr2+, which are only slightly larger than the 4-cm'1 3argon-krypton matrix difference for CF3 and CHBr2 radicals,1,9,23,24 suggests that the gas-to-argon matrix shift for the vibrational fundamental of the ion is relatively small (~10 cm"1). This in turn suggests that even the low-intensity IRMPDS may involve higher vibrational manifold excitations and peak at slightly lower energy than the fundamental owing to normal cubic anharmonicity.Perhaps the most important information from the present study is that C-F vibrational modes in relatively large radical cations absorb at slightly higher frequencies than the corresponding modes of the neutral molecule. The effect on perfluoropropene is relatively small, ca. 29 and 17 cm"1 for the two modes. A much larger increase (21)

J aggregates of a pseudoisocyanine dye (PIC) at a mica/solution interface were in situ observed in solution for the first time by atomic force microscopy (AFM), confirming formation of the aggregates showing a narrow J absorption band (peak, ∼580 nm; line width (HWHM), ∼120-125 cm -1 ) at room temperature. The J aggregates possessed the three-dimensional island structure with the height of about 3-6 nm, consisting of at least ∼10 6 PIC molecules, but not a two-dimensional monolayer structure. The growth processes of the J aggregates were discussed on the basis of the morphological changes of the islands with a dye concentration (i.e., Volmer-Weber type growth process), while the optical properties such as the absorption peak position, line width, or fluorescence lifetime (∼50 ps) were unchanged. These results indicated that the physical aggregation size observed was much larger than the coherence size of the J aggregate.

The design of nano- and microstructures based on self-organization is a key area of research in the search for new materials, and it has a variety of potential applications in tissue engineering scaffolds. We have reported a honeycomb-patterned polymer film (honeycomb film) with highly regular pores that is formed by self-organization. This study describes the behavior of vascular endothelial cells (ECs) on honeycomb films with four different pore sizes (5, 9, 12, and 16 microm) as well as on a flat film. We examined the influence of the honeycomb pattern and pore size on cell behavior. The changes in cell morphologies, actin filaments, vinculin clusters, cell proliferation, and secreted extracellular matrix (ECM) (fibronectin, laminin, type IV collagen, and elastin) production profiles were observed by using optical, fluorescence, and scanning electron microscopy. The ECs that adhered to the flat film showed an elongated morphology with random orientation; the actin filaments and focal adhesions were not conspicuous. On the other hand, the ECs on the honeycomb films exhibited greater spreading and flattening; the degree of spreading of the ECs increased with an increase in the pore size. The actin filaments and focal adhesions appeared conspicuous, and the focal adhesions localized along the edge of the honeycomb pores were distributed over the entire projected cell area. The honeycomb film with a pore size of 5 microm showed the highest cell proliferation and ECM production profiles. These results suggest that the honeycomb film is a suitable material for designing a new vascular device.

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Surface topography has vital roles in cellular response. Here, to investigate the mechanism behind cellular response to surface topography, we prepared honeycomb (HC)-patterned films from poly(epsilon-caprolactone) (PCL) with micropatterned surface topography by casting a polymer solution of water-immiscible solvent under high humidity. We characterized the adsorption of fibronectin (Fn) on the film using atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). The response of porcine aortic endothelial cells (PAECs) to adsorbed Fn molecules onto HC-patterned films was observed by immunofluorescence labeling of vinculin and the actin fiber of PAECs cultured for 1 and 72 h in serum-free medium. The expression of focal adhesion kinase autophosphorylated at the tyrosine residue (pFAK) at 1 h culture was determined using an immunoprecipitation method. Fn adsorbed selectively around the pore edges to form ring-shaped aggregates. The immunostaining results revealed that PAECs adhered to the HC-patterned films at focal contact points localized around pore peripheries. These points correspond to adsorption sites of Fn. The expression of pFAK after 1 h on the HC-patterned film was 3 times higher than that on a corresponding flat film, indicating that the signaling mediated by the binding between Fn and the integrin receptor was more highly activated on the HC-patterned film. These results suggest that the cellular response to HC-patterned films (e.g., adhesion pattern and phosphorylation of FAK) originates from the regularly aligned adsorption pattern of Fn determined by the pore structure of the film.

Tough triple network (TN) hydrogels that facilitate cell spreading and proliferation and, at the same time, preserve high mechanical strength are synthesized by the introduction of a proper component of negatively charged moiety, poly(2-acrylamido-2-methyl-propane sulfonic acid sodium salt) (PNaAMPS), on which cells proliferate, with neutral moiety, poly(N,N-dimethylacrylamide) (DMAAm), on which cells do not proliferate, as the third network component, to PNaAMPS/PDMAAm double network (DN) gels. For synthesizing the tough TN gels to support cell viability, the effect of charge density on the behaviors of three kinds of cells, bovine fetal aorta endothelial cells (BFAECs), human umbilical endothelial cells (HUVECs), and rabbit synovial tissue-derived fibroblast cells (RSTFCs) were systematically investigated on poly(NaAMPS-co-DMAAm) gels with different charge density. The charge density of the gels was tuned by changing the molar fraction (F) of negatively charged monomer in the copolymer hydrogels. Critical F, which corresponds to a critical value of the zeta potential (zeta), is observed for cell spreading and proliferation. The critical F for BFAECs and HUVECs proliferate to confluent is F = 0.4 (zeta = -20 mV), whereas the critical F for RSTFCs shifts to F = 0.7 (zeta = -28.5 mV). The effect of gel charge density on cell behavior is correlated well with the total adsorbed proteins and fibronectin. By applying these results, cell proliferation is successfully realized on the tough TN hydrogels without surface modification with any cell adhesive proteins or peptides. The results will substantially promote the application of tough hydrogels as soft and wet tissues.

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