Dual mode gelation behavior of silk fibroin microgel embedded poly(ethylene glycol) hydrogels.

Hydrogel formation by more than two cross-linking mechanisms is preferred for the sophisticated manipulation of hydrogel properties. Both chemical and physical crosslinks are often utilized for fabricating stimuli-responsive hydrogels or for compensating the drawbacks of the single crosslinking method. In this study, silk fibroin (SF) microgel embedded poly(ethylene glycol) (PEG) hydrogels were fabricated by dual mode cross-linking based on thiol-ene photo-click chemistry and ß-sheet formation of SF. Norbornene-functionalized SF (SF-NB) was incorporated into PEG hydrogels by photo-cross-linking. The equilibrium shear modulus of SF-PEG hybrid hydrogels decreased with increasing SF-NB content. However, the incorporation of SF-NB caused stiffening of SF-PEG hybrid hydrogels gradually over 5 days and the gel modulus was maintained for 2 weeks. In contrast, the modulus of pure PEG hydrogels decreased continuously owing to hydrolytic degradation of ester bonds in the PEGNB macromers. Structural analysis revealed that such a post-gelation stiffening effect was caused by ß-sheet transition in SF microgels embedded in the PEG hydrogel matrix. PEG hydrogels incorporated with 4 wt% SF microgels exhibited about 2-fold increase in shear modulus compared with the modulus on day 1 post-gelation. To evaluate the compatibility of these hydrogels as cell culture matrices, the cytotoxicity of the hydrogel was examined using in situ encapsulated A549 cells. SF-PEG hybrid hydrogels showed no apparent cytotoxicity and promoted the proliferation of encapsulated A549 cells even at a higher gel modulus compared with cells in pure PEG hydrogels. These results suggest that SF-PEG hybrid hydrogels fabricated by dual mode crosslinking serve as good candidates for three-dimensional cell culture requiring temporal control of hydrogel stiffness.

Defining the molecular response to trastuzumab, pertuzumab and combination therapy in ovarian cancer.

BACKGROUND: Trastuzumab and pertuzumab target the Human Epidermal growth factor Receptor 2 (HER2). Combination therapy has been shown to provide enhanced antitumour activity; however, the downstream signalling to explain how these drugs mediate their response is not clearly understood. METHODS: Transcriptome profiling was performed after 4 days of trastuzumab, pertuzumab and combination treatment in human ovarian cancer in vivo. Signalling pathways identified were validated and investigated in primary ovarian xenografts at the protein level and across a timeseries. RESULTS: A greater number and variety of genes were differentially expressed by the combination of antibody therapies compared with either treatment alone. Protein levels of cyclin-dependent kinase inhibitors p21 and p27 were increased in response to both agents and further by the combination; pERK signalling was inhibited by all treatments; but only pertuzumab inhibited pAkt signalling. The expression of proliferation, apoptosis, cell division and cell-cycle markers was distinct in a panel of primary ovarian cancer xenografts, suggesting the heterogeneity of response in ovarian cancer and a need to establish predictive biomarkers. CONCLUSION: This first comprehensive study of the molecular response to trastuzumab, pertuzumab and combined therapy in vivo highlights both common and distinct downstream effects to agents used alone or in combination, suggesting that complementary pathways may be involved.

Structural characteristics and properties of the regenerated silk fibroin prepared from formic acid.

Structural characteristics and thermal and solution properties of the regenerated silk fibroin (SF) prepared from formic acid (FU) were compared with those of SF from water (AU). According to the turbidity and shear viscosity measurement, SF formic acid solution was stable and transparent, no molecular aggregations occurred. The sample FU exhibited the beta-sheet structure, while AU random coil conformation using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry. The effects of methanol treatment on samples were also examined. According to the measurement of crystallinity (XRD) and crystallinity index (FTIR), the concept of long/short-range ordered structure formation was proposed. Long-range ordered crystallites are predominantly formed for methanol treated SF film while SF film cast from formic acid favors the formation of short-range ordered structure. The relaxation temperatures of SF films measured by dynamic thermomechanical analysis supported the above mechanism due to the sensitivity of relaxation temperature on the short-range order.

Solvent effect on the alpha-effect for the reactions of aryl acetates with butane-2,3-dione monoximate and p-chlorophenoxide in MeCN-H2O mixtures.

Second-order rate constants have been measured spectrophotometrically for the nucleophilic reactions of three substituted phenyl acetates with butane-2,3-dione monoximate (Ox(-)) as an alpha-nucleophile and p-chlorophenoxide (ClPhO(-)) as corresponding normal nucleophile, in MeCN-H2O mixtures of varying compositions at 25.0 +/- 0.1 degrees C. The reactivity of Ox(-) toward the aryl acetates decreases upon addition of MeCN to the reaction medium up to ca. 30 mol % MeCN, followed by a gradual increase in rate upon further addition of MeCN. A similar result has been obtained for the reaction of ClPhO(-) with the aryl acetates. However, the decrease in rate is more significant for the less reactive ClPhO(-) than for the more reactive Ox(-). Thus, for all the aryl acetates studied, Ox(-) exhibits a sizable alpha-effect (k(Ox)-/k(ClPhO)-) whose magnitude increases as the mol % MeCN in the reaction medium increases. The relative basicities (DeltapK(a)) of Ox(-) and ClPhO(-) have been determined spectrophotometrically using piperazine as a reference base. The DeltapK(a) values increase on increasing the mol % MeCN in the medium for both Ox(-) and ClPhO(-). The difference in the relative basicities of these nucleophiles (DeltaDeltapK(a)) becomes larger with increasing mol % MeCN. The plots of log k(Ox)-/k(ClPhO)- vs DeltaDeltapK(a) for the three substrates are linear with near-unit slope, indicating that the difference in the relative basicity of the nucleophiles is largely responsible for the increasing alpha-effect with medium composition in this system.