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 φ2 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. In the nanocomposite hydrogels used here Apigenin-7-O-beta-D-glucopyranoside Laponite acts as the site for forming multifunctional crosslinking points and feff was calculated based on Equation (3):
(3) where Mw L is the molecular weight of Laponite (2.5 × 106 g mol?1) and CL 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)  and Laponite (2.53 g Apigenin-7-O-beta-D-glucopyranoside cm?3)  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 veff 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 feff. 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. Specifically PAAm-ND exhibited equal or higher veff and feff values when compared to those of PAAm-D. Additionally PAAm-ND equillibriated at pH 5. 0 exhibited the highest veff and feff values reported for all the formulations tested. At pH 9.0 both veff and feff 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 veff and feff values reported here are of the same order of magnitude as other physically crosslinked nanocomposite.