Charlton Samuel G V, Jana Saikat, Chen Jinju
Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, 8093, Switzerland.
Newcastle University, School of Engineering, Newcastle Upon Tyne, NE1 7RU, United Kingdom.
Biofilm. 2024 Jul 3;8:100209. doi: 10.1016/j.bioflm.2024.100209. eCollection 2024 Dec.
The mechanics of biofilms are intrinsically shaped by their physicochemical environment. By understanding the influence of the extracellular matrix composition, pH and elevated levels of cationic species on the biofilm rheology, novel living materials with tuned properties can be formulated. In this study, we examine the role of a chaotropic agent (urea), two divalent cations and distilled deionized water on the nonlinear viscoelasticity of a model biofilm . The structural breakdown of each biofilm is quantified using tools of non-linear rheology. Our findings reveal that urea induced a softening response, and displayed strain overshoots comparable to distilled deionized water, without altering the microstructural packing fraction and macroscale morphology. The absorption of divalent ferrous and calcium cations into the biofilm matrix resulted in stiffening and a reduction in normalized elastic energy dissipation, accompanied by macroscale morphological wrinkling and moderate increases in the packing fraction. Notably, ferrous ions induced a predominance of rate dependent yielding, whereas the calcium ions resulted in equal contribution from both rate and strain dependent yielding and structural breakdown of the biofilms. Together, these results indicate that strain rate increasingly becomes an important factor controlling biofilm fluidity with cation-induced biofilm stiffening. The finding can help inform effective biofilm removal protocols and in development of bio-inks for additive manufacturing of biofilm derived materials.
生物膜的力学特性本质上受其物理化学环境的影响。通过了解细胞外基质组成、pH值和阳离子种类水平升高对生物膜流变学的影响，可以制备出具有可调特性的新型生物材料。在本研究中，我们研究了一种离液剂（尿素）、两种二价阳离子和去离子蒸馏水对模型生物膜非线性粘弹性的作用。使用非线性流变学工具对每种生物膜的结构破坏进行量化。我们的研究结果表明，尿素引发了软化反应，并表现出与去离子蒸馏水相当的应变过冲，而未改变微观结构堆积分数和宏观形态。二价亚铁离子和钙离子被生物膜基质吸收导致生物膜变硬，归一化弹性能耗降低，同时伴有宏观形态起皱和堆积分数适度增加。值得注意的是，亚铁离子导致速率依赖性屈服占主导，而钙离子导致速率和应变依赖性屈服以及生物膜结构破坏的贡献相等。总之，这些结果表明，随着阳离子诱导生物膜变硬，应变速率越来越成为控制生物膜流动性的重要因素。这一发现有助于为有效的生物膜去除方案提供信息，并有助于开发用于生物膜衍生材料增材制造的生物墨水。
