@article{gil_hudson_2007, title={Effect of silk fibroin interpenetrating networks on swelling/deswelling kinetics and rheological properties of poly(N-isopropylacrylamide) hydrogels}, volume={8}, ISSN={["1526-4602"]}, DOI={10.1021/bm060543m}, abstractNote={Novel protein/synthetic polymer hybrid interpenetrating polymer networks (IPNs) of poly(N-isopropylacrylamide) (PNIPAAm) with Bombyx mori silk fibroin (SF) have been prepared by using methanol to postinduce SF crystallization. Those IPNs having the beta sheet crystalline structure of SF show improved storage and loss moduli. The IPN hydrogels show the same volume phase transition temperature and NaCl concentration as pure PNIPAAm hydrogels. The PNIPAAm/SF IPNs keep the swelling kinetics of PNIPAAm, while showing increased deswelling kinetics. The IPNs with SF beta sheet structure should decrease the formation of the skin layer observed in conventional PNIPAAm hydrogels. Therefore, the proposed IPN hydrogels composed of protein/polymer provide fast deswelling rates as well as improved mechanical properties over pure PNIPAAm hydrogels. The effect of SF beta sheet networks on the IPNs copolymerized with acrylic acid (AAc) (P(NIPAAm-co-AAc)/SF IPNs) is compared with that on the PNIPAAm/SF IPNs, and the parameters controlling the deswelling kinetics of the IPNs are investigated. Three parameters, (1) the skin layer formation, (2) the restriction of SF beta sheet networks, and (3) the aggregation force of NIPAAm chains, are cooperatively involved in the deswelling process of IPN hydrogels according to the SF content and the presence of the AAc moiety.}, number={1}, journal={BIOMACROMOLECULES}, author={Gil, Eun Seok and Hudson, Samuel M.}, year={2007}, month={Jan}, pages={258–264} }
 @article{gil_frankowski_hudson_spontak_2007, title={Silk fibroin membranes from solvent-crystallized silk fibroin/gelatin blends: Effects of blend and solvent composition}, volume={27}, ISSN={["0928-4931"]}, DOI={10.1016/j.msec.2006.05.017}, abstractNote={Protein membranes have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to induce SF crystallization. Amorphous blends of these polymers appear quasi-homogeneous, as discerned from visual observation, electron microscopy and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random-coil to β-sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, as discerned from FTIR spectroscopy and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been measured as functions of blend and solvent composition. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels or generate SF membranes for biomaterial, pharmaceutical and gas-separation purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally-responsive G/SF bioconjugates.}, number={3}, journal={MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS}, author={Gil, Eun S. and Frankowski, David J. and Hudson, Samuel M. and Spontak, Richard J.}, year={2007}, month={Apr}, pages={426–431} }
 @article{gil_frankowski_bowman_gozen_hudson_spontak_2006, title={Mixed protein mends composed of gelatin and bombyx mori silk fibroin: Effects of so solvent-induced crystallization and composition}, volume={7}, ISSN={["1526-4602"]}, DOI={10.1021/bm050622i}, abstractNote={Novel protein blends have been prepared by mixing gelatin (G) with Bombyx mori silk fibroin (SF) and using aqueous methanol (MeOH) to post-induce SF crystallization. When co-cast from solution, amorphous blends of these polymers appear homogeneous, as discerned from visual observation, microscopy, and Fourier-transform infrared (FTIR) spectroscopy. Upon subsequent exposure to aqueous MeOH, SF undergoes a conformational change from random coil to beta sheet. This transformation occurs in pure SF, as well as in each of the G/SF blends, according to X-ray diffractometry and thermal calorimetry. The influence of MeOH-induced SF crystallization on structure and property development has been ascertained in terms of preparation history and blend composition. Thermal gravimetric analysis reveals that the presence of beta sheets in SF and G/SF blends improves thermal stability, while extensional rheometry confirms that SF crystallization enhances the tensile properties of the blends. By preserving a support scaffold above the G helix-to-coil transition temperature, the formation of crystalline SF networks in G/SF blends can be used to stabilize G-based hydrogels for biomaterial and pharmaceutical purposes. The present study not only examines the properties of G/SF blends before and after SF crystallization, but also establishes the foundation for future research into thermally responsive G/SF bioconjugates.}, number={3}, journal={BIOMACROMOLECULES}, author={Gil, ES and Frankowski, DJ and Bowman, MK and Gozen, AO and Hudson, SM and Spontak, RJ}, year={2006}, month={Mar}, pages={728–735} }
 @article{gil_spontak_hudson_2005, title={Effect of beta-sheet crystals on the thermal and rheological behavior of protein-based hydrogels derived from gelatin and silk fibroin}, volume={5}, ISSN={["1616-5187"]}, DOI={10.1002/mabi.200500076}, abstractNote={Novel protein-based hydrogels have been prepared by blending gelatin (G) with amorphous Bombyx mori silk fibroin (SF) and subsequently promoting the formation of beta-sheet crystals in SF upon exposure to methanol or methanol/water solutions. Differential scanning calorimetry of the resultant hydrogels confirms the presence and thermoreversibility of the G helix-coil transition between ambient and body temperature at high G concentrations. At low G concentrations, this transition is shifted to higher temperatures and becomes progressively less pronounced. Complementary dynamic rheological measurements reveal solid-liquid cross-over at the G helix-coil transition temperature typically between 30 and 36 degrees C in blends prior to the formation of beta-sheet crystals. Introducing the beta-sheet conformation in SF stabilizes the hydrogel network and extends the solid-like behavior of the hydrogels to elevated temperatures beyond body temperature with as little as 10 wt.-% SF. The temperature-dependent elastic modulus across the G helix-coil transition is reversible, indicating that the conformational change in G can be used in stabilized G/SF hydrogels to induce thermally triggered encapsulant release.}, number={8}, journal={MACROMOLECULAR BIOSCIENCE}, author={Gil, ES and Spontak, RJ and Hudson, SM}, year={2005}, month={Aug}, pages={702–709} }
 @article{gil_frankowski_spontak_hudson_2005, title={Swelling behavior and morphological evolution of mixed gelatin/silk fibroin hydrogels}, volume={6}, ISSN={["1526-4602"]}, DOI={10.1021/bm050396c}, abstractNote={Mixed protein-based hydrogels have been prepared by blending gelatin (G) with amorphous Bombyx mori silk fibroin (SF) and promoting beta-crystallization of SF via subsequent exposure to methanol or methanol/water solutions. The introduction of beta crystals in SF serves to stabilize the hydrogel network and extend the solidlike behavior of these thermally responsive materials to elevated temperatures beyond the helix-->coil (h-->c) transition of G. In this work, we investigate the swelling and protein release kinetics of G/SF hydrogels varying in composition at temperatures below and above the G h-->c transition. At 20 degrees C, G and G-rich mixed hydrogels display evidence of moderate swelling with negligible mass loss in aqueous solution, resulting in porous polymer matrixes upon solvent removal according to electron microscopy. When the solution temperature is increased beyond the G h-->c transition to body temperature (37 degrees C), these gels exhibit much higher swelling with considerable mass loss due to dissolution and release of G. The extent to which these properties respond to temperature decreases systematically with increasing SF content. The unique temperature- and composition-dependent properties of G/SF hydrogels dictate the efficacy of these novel materials as stimuli-responsive delivery vehicles.}, number={6}, journal={BIOMACROMOLECULES}, author={Gil, ES and Frankowski, DJ and Spontak, RJ and Hudson, SM}, year={2005}, pages={3079–3087} }