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Abstract Obesity-related type 2 diabetes (DM) is a major public health concern. Adipose tissue metabolic dysfunction, including fibrosis, plays a central role in DM pathogenesis. Obesity is associated with changes in adipose tissue extracellular matrix (ECM), but the impact of these changes on adipose tissue mechanics and their role in metabolic disease is poorly defined. This study utilized atomic force microscopy (AFM) to quantify difference in elasticity between human DM and non-diabetic (NDM) visceral adipose tissue. The mean elastic modulus of DM adipose tissue was twice that of NDM adipose tissue (11.50 kPa vs. 4.48 kPa) to a 95% confidence level, with significant variability in elasticity of DM compared to NDM adipose tissue. Histologic and chemical measures of fibrosis revealed increased hydroxyproline content in DM adipose tissue, but no difference in Sirius Red staining between DM and NDM tissues. These findings support the hypothesis that fibrosis, evidenced by increased elastic modulus, is enhanced in DM adipose tissue, and suggest that measures of tissue mechanics may better resolve disease-specific differences in adipose tissue fibrosis compared with histologic measures. These data demonstrate the power of AFM nanoindentation to probe tissue mechanics, and delineate the impact of metabolic disease on the mechanical properties of adipose tissue.

Achieving simultaneous high storage and loss moduli in gels is difficult due to the opposite chemical structure requirements needed for such properties. Here the authors show a spectrum of gels containing CdTe nanoparticles stabilized by glutathione that have such properties which can be rationalised through the developed model.

The structure of A-b-B diblock copolymer (BCP) thin films is often exploited for “tailoring” the self-assembly of nanoparticles into various geometries, characterized by long-range order. Mechanistically, the nanoparticles are sequestered within the A or B domains of the copolymer, and the domains act as scaffolds to direct the assembly of the nanoparticles. We show that in BCP thin films, which order at suboptimal thicknesses, dislocations play a dominant role in determining the spatial organization of sufficiently large nanoparticles. The nanoparticles preferentially segregate to the core of edge dislocations, which are ubiquitous in these materials. To this end, the two-dimensional planar shape of the islands and holes determine the self-assembled geometry of the nanoparticles. We also show that the so-called “healing length”, λ, increases with film thickness, h, in a manner consistent with λ ∝ h1/2, in accordance with theory. In films of thickness between L< h< 3L, where Lis the domain spacing, λ largely determines the average size of the region within which the nanoparticles are sequestered. [ABSTRACT FROM AUTHOR]

The phase behavior of supported thin film mixtures (h∼ 120 nm thick) of polystyrene (PS) brush-coated spherical nanoparticle and PS homopolymers is characterized by three regimes, depending on P, the degree of polymerization of the PS host, and N, the degree of polymerization of the grafted chains. Phase separation between the nanoparticles and the host chains occurs in samples for which N N*, preferential segregation of the grafted nanoparticles to the interfaces is accompanied by a structural instability (surface roughening). We identify this as regime I and the former as regime II. The system is miscible in regime III (P N*); the nanoparticles are dispersed throughout the film. There exists a region of partial miscibility that separates regimes I and III. The characteristics of regime I are reminiscent of phase separation in polymer/polymer thin film mixtures. Regime II is reminiscent of the interfacial segregation of hard spheres in an athermal melt of polymer chains. [ABSTRACT FROM AUTHOR]

The physical properties of thin polymer films are often thickness, h, dependent, influenced by confinement and by interfacial interactions between the chains and the external interfaces. We show that the magnitude and film thickness dependence of the average glass transition temperature, Tg, of the polystyrene−silicon oxide (PS/SiO x/Si) system are influenced appreciably with the addition of polystyrene- b-poly(methyl methacrylate) (PS- b-PMMA) diblock copolymers. The Tgcan be “tailored” to increase, or decrease, with decreasing hor to remain independent of h. Tgshifts of as much of 35 °C are obtained for films of h≈ 20 nm. Additionally, we report that the critical micelle concentration, φ cmc, of the copolymer in thin films is considerably larger than for the bulk; specifically, micelles form only beyond a critical film thickness, determined by the size of the chains and by the number of chains in the system. The hdependence of Tgis not influenced by the ϕ cmcor by the number of micelles in this system. [ABSTRACT FROM AUTHOR]

It has recently been shown that thin polymer films in the nanometer thickness range exhibit anomalous swelling maxima in supercritical CO2 (Sc‐Co2) in the vicinity of the critical point of CO2. The adsorption isotherm of CO2 on carbon black, silica surfaces, porous zeolites, and other surfaces, is known to exhibit anomalous maxima under similar CO2 conditions. It is believed that because CO2 possesses a low cohesive energy density, there would be an excess amount of CO2 at the surfaces of these materials and hence the CO2/polymer interface. This might cause excess CO2 in the polymer films near the free surface, and hence the swelling anomaly. In addition, an excess of CO2 would reside at the polymer/substrate and polymer/CO2 interfaces for entropic reasons. These interfacial effects, as have been suggested, should account for an overall excess of CO2 in a thin polymer film compared to the bulk, and would be responsible for the anomalous swelling. In this study, we use in situ spectroscopic ellipsometry to investigate the role of interfaces on the anomalous swelling of polymer thin films of varying initial thicknesses, h0, exposed to Sc‐CO2. We examined three homopolymers, poly(1,1′‐dihydroperflurooctyl methacrylate) (PFOMA), polystyrene (PS), poly(ethylene oxide) (PEO), that exhibit very different interactions with Sc‐CO2, and the diblock copolymer of PS‐b‐PFOMA. We show that the anomalous swelling cannot be solely explained by the excess adsorption of CO2 at interfaces. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1313–1324, 2007 [ABSTRACT FROM AUTHOR]