High yield (95% recovery of SF protein) and high productivity (>98% salt removal in <2hrs.) shown herein for Sephadex column chromatography provide a promising alternative to conventional SF purification by dialysis. Purification of SF solutions by Sephadex G-25 column chromatography could be an effective and industrially scalable chemical

process. However, further optimization and analysis need to be performed for utilizing SF in Inhibitors,research,lifescience,medical pharmaceutical development. In addition, Sephadex media can be flushed and reused, thereby reducing development costs associated with purification of SF solutions. 4.2. Design of SF-Based Controlled Release Systems SF is dominated in composition by the amino acids glycine, alanine and serine which tend to form antiparallel β-sheets or crystals through hydrogen bonding and hydrophobic interactions. Upon gelation a random coil structure of the SF transformed into Inhibitors,research,lifescience,medical β-sheet structure. Several factors affect the gelation of the SF aqueous solutions. Many factors such as temperature, SF concentration, shear force, metallic ions, Ca2+, pH, treatment with low dielectric Inhibitors,research,lifescience,medical constant solvents and poly(ethylene oxide) [21, 26] are thought to affect the conformation transition. With increase in SF content and temperature, physical cross-linking among SF chains formed more easily. Ca2+ ions accelerated these interactions through the hydrophilic

blocks at the chain ends [27]. Inhibitors,research,lifescience,medical It is well known and reported in the literature [14] that the addition of methanol

to SF induces aggregation (STI571 manufacturer dehydration), which drives the structural transition from random coil to β-sheet. It was demonstrated [28, 29] that upon methanol-induced crystallization, the SF β-sheet network stabilizes SF/gelatin hydrogels at elevated temperatures. The transition of Inhibitors,research,lifescience,medical regenerated SF films from random coil to β-sheet has been reported [30] after treatment with methanol, ethanol, and 2-propanol. It was also demonstrated [31] that the rate of gelation of SF was dependent upon glycerol content and/or SF content and addition of glycerol to the SF solution accelerated this rate. In our research, we investigated the effect of dehydrating solvents (methanol, ethanol, isopropyl alcohol, and glycerin) on formation of β-sheets in SF/gelatin blends and demonstrated that the treatment with glycerin is also effective for the transformation of silk I to II which is in agreement with also the literature data [32]. The presence of glycerin in the matrix can trigger β-sheet induction as seen from Table 3 at the ratio of SF/gelatin ~1:1. Since the β-sheet formation did not occur in experiments with SF-to-gelatin ratio of 1:3, it is suggested that the ratio of SF to gelatin is also critical for the β-sheet formation. In the presence of glycerin, for the SF/gelatin 1:1 blend, untreated films exhibit the absorption bands characteristic of the β-sheet structure.