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Bacterial Nanocellulose Hydrogels Designed as Bioartifcial Medical Implants
Published in Miguel Gama, Paul Gatenholm, Dieter Klemm, Bacterial NanoCellulose, 2016
Dieter Klemm, Hannes Ahrem, Friederike Kramer, Wolfgang Fried, Jens Wippermann, Raimund W. Kinne
The modulus of elasticity, ultimate tensile strength, elongation to failure, and fracture toughness are important features describing the mechanical properties of biomaterials (Teoh 2004). In comparison to stiff materials like metals or ceramics, BNC in its native, hydrated state is a hydrogel with low modulus of elasticity and fracture toughness. While the single BNC fibers have the mechanical strength of steel or Kevlar (Klemm et al. 2011), the mechanical properties of the whole hydrogel are partially defined by its water content and the discharge of water during compression. The water retention capacity of a BNC hydrogel is influenced by the structural composition of the fiber network. Because of the anisotropic architecture of the fleeces, there are regions with different mechanical properties. The wide-meshed network of the bottom layer leads to lower water binding and reduced mechanical properties. Sufficient mechanical properties of the BNC biomaterial are pivotal for surgical fixation and the compressive and tribological stress experienced by the biomaterial at the site of implantation. Current studies therefore focus on comparing the biomechanical properties of BNC and body tissues or the formation of composite (e.g., double-network) gels.
Case Study 6: Mechanics of Biomaterials
Published in Jenn Stroud Rossmann, Clive L. Dym, Lori Bassman, Introduction to Engineering Mechanics, 2015
Jenn Stroud Rossmann, Clive L. Dym, Lori Bassman
It is critical for engineers to understand how such materials will respond to loading, to mechanical stresses, and to biochemical and electrical stimuli, as well. In his pioneering texts on Biomechanics, Y. C. Fung outlines a systematic approach to problems in biomechanics: the first step is studying organism morphology, organ anatomy, tissue histology, and structure of materials. The second is determining the mechanical properties of the materials involved, before later steps—deriving the governing equations, developing boundary conditions, solving the problems, and performing experiments—follow. As Fung notes, determining the mechanical properties of biomaterials can be difficult, because “we cannot isolate the tissue for testing, or the size of available tissue specimens is too small, or it is difficult to keep the tissue in the normal living condition. Furthermore, biological tissues are often subjected to large deformations, and the stress–strain relationships are usually nonlinear and history dependent.”
Fabrication of silk fibroin film enhanced by acid hydrolyzed silk fibroin nanowhiskers to improve bacterial inhibition and biocompatibility efficacy
Published in Journal of Biomaterials Science, Polymer Edition, 2022
Minjie Lin, Wenjiao Xie, Xiuwen Cheng, Yuncong Yang, Jegatheeswaran Sonamuthu, Ying Zhou, Xiaogang Yang, Yurong Cai
The mechanical properties of biomaterials are essential for their application. The effect of SNWs on the mechanical properties of silk fibroin films was investigated by the universal testing machine. As shown in Table 1, the elastic modulus of films increases with the adding of SNWs which rise from 0 to 0.5 mg/mL in the RSF film. The maximum value of elastic module of films is 4.74 GPa when the addition of SNWs was 0.5 mg/mL. But with the further increase of SNWs contents, the elastic modulus and elongation at break of films are decreasing. The changing trend of elongation at break is consistent with the elasticity module of films. SNWs show a specific enhancement effect on the strength of RSF film. There are plenty of hydrophilic groups on SNWs, which can form plenty of hydrogen bonds between SNWs and RSF molecules when SNWs are added into the RSF solution. Subsequently, the strength and toughness of the film are improved. However, the strength of RSF/SNWs film goes poor with the increase of SNWs contents probably because the entanglement of the SNWs leads to uneven distribution in the film [36, 37]. The status in turn reduces the strength and elongation at the break of films. As a potential wound dressing, the elasticity of silk fibroin film is essential, a certain content of SNWs can significantly improve the toughness of RSF film, which makes it possible for RSF film used for wound dressing.