Microrheology and Release Behaviors of Self-Assembled Steroid Hydrogels

A hydrogel is formed by the self-assembly of sodium deoxycholate (NaDC) in aqueous solution with sodium chloride at pH-7.0. The NaDC hydrogel made of the three-dimensional network of nanofibers shows pH-dependent swelling behaviors. Polystyrene particles with a diameter of 100 nm and doxorubicin hydrochloride (DOX) can be easily loaded into the NaDC hydrogel through swelling. By using the loaded polystyrene particles as a light scattering probe, we study the microrheology of the NaDC hydrogel, showing complex viscoelastic properties. The viscous component dominates at both low and high frequencies, while the elastic component dominates in the intermediate range. The cavity size of the nanofiber network can also be estimated to be ~180 nm. We show that the loaded DOX can be slowly released from the hydrogels into aqueous solution. The release profile of DOX is found to depend on the pH value of the solution.

In situ measurement of ECM rheology and microheterogeneity in embedded and overlaid 3D pancreatic tumor stroma co-cultures via passive particle tracking

Tumor growth is regulated by a diverse set of extraellular infuences,including paracrine crosstalk with stromal partners,and biophysical interactions with surrounding cells and tissues.Studies elucidating the role of physical force and the mechanical properties of the extracellular matrix(ECM)itself as regulators of tumor growth and invasion have been greatly catalyzed by the use of in ritro three-dimensional(3D)tumor models.These systems provide the ability to systematically isolate,manipulate,and evaluate impact of stromal components and extracellular mechanics in a platform that is both conducive to imaging and biologically relevant.However,recognizing that mechanoregulatory crosstalk is bi-directional and fully utilizing these models requires complementary methods for in situ measurements of the local mechanical environment.Here,in 3D tumor/fbroblast co-culture models of pancreatic canocer,a discase characterized by its prominent stromal involvement,we evaluate the use of particle-tracking microrhoology to probe dynamic mechanical changes.Using videos of fuorescently labeled polystyrene micro-spheres embedded in ollagen I ECM,we measure spatiotemporal changes in the Brownian motion of probes to report local ECM shear modulus and microheterogeneity.This approach reveals st ffening of collagen in fibroblast co-cultures relative to cultures with cancer cells only,which exhibit degraded ECM with heterogeneous microstructure.We further show that these effects are dependent on culture geometry with contrast ing behavior for embedded and overlay cultures.In addition to potential application to screening stroma targeted therapeutics,this work also provides insight into how the compoition and plating geometry impact the mechanical propertios of 3D cell cultures that are increasingly widey used in cancer biology.

Rheological Properties of Waterborne Polyurethane Paints

The rheological properties of two specific waterborne polyurethane （PU） paints were studied by both macrorheological and microrheological methods. During the macrorheological measurement on a rotary rheometer, evaporation of solvent cannot be totally excluded, which has an influence on the reliability of rheological results. So, the linear oscillatory frequency sweep results （storage and loss modulus versus frequency） and steady shear results （viscosity versus shear rate） got from the rotary rheometer measurement are only used for qualitative analysis. As the evaporation of solvent can be neglected during microrheological measurements on a diffusing wave spectroscope （DWS）, the results of storage modulus （G3 and loss modulus （G＇~） versus frequency are more credible than the results obtained from the rotary rheometer measurement. Thus, the results of G＇ and G＂ versus frequency from DWS measurements are used for quantitative analysis in this work. The G＇ for both of the waterborne PU paints are larger than G＂ at low frequency and that is opposite at high frequency in the experimental angular frequency range. The values of modulus at same frequency and viscosity at low shear rate for the two PU paints have apparent difference, which determines the difference of their application.

Microrheological characteristics of reticulocyte in vivo

Using the method of phenylhydrazine-induced anemia in rabbits, a mass of new reticulocytes, which synchronously grow, were got in vivo. The measurements of deformation index, orientation index, electrophoresis mobility etc. were performed for more than 72 h in the process of reticulocytes turning into red blood cells in vivo. There were obvious changes in the micro- rheological characteristics of reticulocytes in the course of turning into erythrocytes. The present study is significant in clinic for studying erythrocytes' microrheological characteristics when there are a lot of reticulocytes in blood, and also important in basic theorem for studying reticulocytes microrheological characteristics. It makes up a deficiency in the study on microrheological characteristics of reticulocytes turning into new RBCs from reticulocytes during reticulocytes life span.