Enzymatically Cross-Linked Tilapia Gelatin Hydrogels: Physical, Chemical, and Hybrid Networks
Enzymatically Cross-Linked Tilapia Gelatin Hydrogels: Physical, Chemical, and Hybrid Networks
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DOI：
10.1021/bm2009894
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发表时间：
2011-10-01
影响因子：
6.2
通讯作者：
Dreiss, Cecile A.
中科院分区：
文献类型：
--
作者：
Bode, Franziska;da Silva, Marcelo Alves;Dreiss, Cecile A.
本文研究了在存在和不存在酶交联剂微生物转谷氨酰胺酶的情况下由罗非鱼明胶（10% w/w）形成的不同类型的网络。在物理、化学和混合凝胶中检查了温度方案和交联剂浓度（0-55 U mTGase/g 明胶）的影响，其中物理凝胶是由三螺旋的形成产生的，当凝胶冷却到胶凝点以下时，三螺旋充当连接点。结合流变学和旋光度来研究储能模量（G'）随时间的演变以及每种类型凝胶形成的三螺旋数量。我们试图将凝胶的最终储能模量分为其化学和物理贡献，以检查两种类型网络之间是否存在协同作用。我们的实验表明，凝胶特性随热方案的不同而变化很大。化学凝胶中的最终储能模量随着酶浓度的增加而增加，这可能是由于在低交联剂量下优先形成闭环。在化学物理凝胶中，物理网络（螺旋）与共价网络连续形成，我们发现低于临界酶浓度，化学网络越广泛（由 G' 测量），最终凝胶越弱。归因于物理网络的储能模量作为化学网络的 G' 的函数呈指数下降，但发现这两个网络都是纯粹相加的。螺旋不是热稳定的。同时形成物理和化学网络（物理-共化学）导致 G' 值高于相同条件下形成的单个网络。区分两种情况：在低酶浓度（10-20 U mTGase/g 明胶）下，网络串联形成，但在存在螺旋的情况下，化学网络的储能模量更高（与纯化学凝胶相比）；在较高的酶浓度（30-40 U mTGase/g 明胶）下，发现了很强的协同效应，因为大部分共价网络在螺旋熔化后变得无效。
This Article investigates different types of networks formed from tilapia fish gelatin (10% w/w) in the presence and absence of the enzymatic cross-linker microbial transglutaminase. The influence of the temperature protocol and cross-linker concentration (0-55 U mTGase/g gelatin) was examined in physical, chemical, and hybrid gels, where physical gels arise from the formation of triple helices that act as junction points when the gels are cooled below the gelation point. A combination of rheology and optical rotation was used to study the evolution of the storage modulus (G') over time and the number of triple helices formed for each type of gel. We attempted to separate the final storage modulus of the gels into its chemical and physical contributions to examine the existence or otherwise of synergism between the two types of networks. Our experiments show that the gel characteristics vary widely with the thermal protocol. The final storage modulus in chemical gels increased with enzyme concentration, possibly due to the preferential formation of closed loops at low cross-linker amount. In chemical physical gels, where the physical network (helices) was formed consecutively to the covalent one, we found that below a critical enzyme concentration the more extensive the chemical network is (as measured by G'), the weaker the final gel is. The storage modulus attributed to the physical network decreased exponentially as a function of G' from the chemical network, but both networks were found to be purely additive. Helices were not thermally stabilized. The simultaneous formation of physical and chemical networks (physical-co-chemical) resulted in G' values higher than the individual networks formed under the same conditions. Two regimes were distinguished: at low enzyme concentration (10-20 U mTGase/g gelatin), the networks were formed in series, but the storage modulus from the chemical network was higher in the presence of helices (compared to pure chemical gels); at higher enzyme concentration (30-40 U mTGase/g gelatin), strong synergistic effects were found as a large part of the covalent network became ineffective upon melting of the helices.