Linear polyacrylamide (PAAm) is modified with dopamine or nitrodopamine (PAAm-D and PAAm-ND respectively) to evaluate the Apigenin-7-O-beta-D-glucopyranoside effect of nitro-group modification on the interfacial binding properties of polymer-bound catechol. functionality and molecular weight between crosslinks nitro-group functionalization of dopamine results in a polymer network with increased crosslinking density and crosslinking points with higher functionality. Nitro-functionalization enhances the interfacial binding property of dopamine and increases its resistant to oxidation which results in nanocomposite hydrogels with enhanced stiffness and a viscous dissipation property. = 3) were tested using parallel plate (20 mm) with a gap that was 85% that of the individual hydrogel thickness as measured by a digital calliper. Mineral oil was applied around the edge of the hydrogel disc to avoid dehydration during testing. 2.7 Statistical Analysis Statistical analysis was performed using JPM Pro 9 software (SAS Cary NC). The student t-test and one-way analysis of variance (ANOVA) with Tukey-Kramer HSD analysis were performed for comparing means of two and more than two groups respectively. A < 0.05); ^ Statistically ... 3.3 Oscillatory Rheometry The viscoelasticity properties of PAAm and Laponite nanocomposite hydrogels with or without the incorporation of dopamine and nitrodopamine moieties were determined using oscillatory rheometry (Figure 4 ? 55 and ?and6).6). Regardless of the polymer or pH nanocomposite hydrogels exhibited very similar responses. For all samples the measured storage Mouse monoclonal to CD47.DC46 reacts with CD47 ( gp42 ), a 45-55 kDa molecule, expressed on broad tissue and cells including hemopoietic cells, epithelial, endothelial cells and other tissue cells. CD47 antigen function on adhesion molecule and thrombospondin receptor. modulus Apigenin-7-O-beta-D-glucopyranoside (is the shear modulus is the gas constant is the temperature in Kelvin and *φ*2 is the volume fraction of the polymer in the hydrogel. *G*′ recorded at a frequency of 1 1 rad s?1 was used as *G*.[61] In the nanocomposite hydrogels used here Apigenin-7-O-beta-D-glucopyranoside Laponite acts as the site for forming multifunctional crosslinking points and *f*eff was calculated based on Equation (3):[62]

(3) where *M*w L is the molecular weight of Laponite (2.5 × 106 g mol?1)[61] and *C*L is the mass concentration of Laponite in the hydrogel. φ2 was calculated based on the EWC data using the density of water (1 g cm?3) PAAm (1.42 g cm?3) [63] and Laponite (2.53 g Apigenin-7-O-beta-D-glucopyranoside cm?3) [64] while assuming the mass ratio of PAAm and Laponite remain the same as the starting mixture at a 60:40 wt%:wt% ratio. For a given pH *v*eff values for PAAm were significantly lower than those of PAAm-D and PAAm-ND (Table 2) indicating that the presence of catechol drastically increased crosslinking density. Similarly PAAm-ND were more densely crosslinked than PAAm-D. This increase in the crosslinking density was associated with the formation of crosslinking points with higher functionality (i.e. a number of elastically effective network chains extending from Laponite) as measured by *f*eff. These results are in agreement with published observations where increased interfacial binding strength between polymer matrix and encapsultated nanoparticles increased both the crosslinking density and functionality of the network.[65] Specifically PAAm-ND exhibited equal or higher *v*eff and *f*eff values when compared to those of PAAm-D. Additionally PAAm-ND equillibriated at pH 5. 0 exhibited the highest *v*eff and *f*eff values reported for all the formulations tested. At pH 9.0 both *v*eff and *f*eff values for PAAm-ND and PAAm-D were equivalent. Given that PAAm-ND exhibited significantly higher moduli values than PAAm-D (Figure 7) our results further confirmed that nitrodopamine formed stronger bonds with Laponite even at a basic pH. Both *v*eff and *f*eff values reported here are of the same order of magnitude as other physically crosslinked nanocomposite.