A comprehensive characterization of the viscoelastic properties of Bovine Submaxillary Mucin (BSM) and the effect of additives

This study presents a comprehensive characterization of the viscoelastic and structural properties of Bovine Submaxillary Mucin (BSM), a good biomaterial model system for mucins and mucus in general. We conducted concentration studies of BSM and examined the effects of various additives - sodium chloride, calcium chloride, lysozyme, and DNA - on its rheological behavior. Through oscillatory and shear flow macrorheological experiments, we established a detailed correlation between the concentration of BSM and its viscoelastic properties, uncovering changes in the rheological moduli with the addition of sodium and calcium chloride, particularly at higher concentrations. This highlights the mucins responsiveness to ionic strength and composition variations. The presence of lysozyme and DNA further influenced the rheological characteristics of BSM, adding a new dimension to our understanding of mucin behavior. The rheological spectra could be well-described by a Fractional Kelvin-Voigt Model (FKVM), which allows to describe the complete behavior with a minimum of model parameters. A detailed proteomics analysis provided insight into the molecular interactions within BSM, enhancing our understanding of its structural intricacies. Complementing this, cryo-scanning electron microscopy (cryo-SEM) was employed to visualize the microstructural alterations and network properties in relation to the rheological data. By elucidating the complex interplay between mucin concentration, environmental conditions, and viscoelastic properties, this research significantly contributes to the field of mucus research and lays an important basis for future studies and advanced applications of numerous mucin-based biomaterials.

本研究对牛颌下粘蛋白（Bovine Submaxillary Mucin, BSM）的粘弹性与结构特性开展了全面表征——该蛋白是通用粘蛋白及粘液体系的优质生物材料模型。我们针对BSM开展浓度梯度研究，并考察了氯化钠、氯化钙、溶菌酶与脱氧核糖核酸（DNA）等多种添加剂对其流变行为的影响。通过振荡流与剪切流宏观流变实验，我们明确了BSM浓度与其粘弹性特性间的详细关联，揭示了添加氯化钠与氯化钙后流变模量的变化规律，尤其在高浓度体系中表现更为显著。该结果凸显了粘蛋白对离子强度与组分变化的响应性。溶菌酶与DNA的存在进一步调控了BSM的流变特性，为我们理解粘蛋白行为增添了全新维度。其流变光谱可通过分数阶开尔文-沃伊特模型（Fractional Kelvin-Voigt Model, FKVM）进行精准描述，该模型仅需少量参数即可完整复现体系的流变行为。详细的蛋白质组学分析为解析BSM内部的分子相互作用提供了关键视角，加深了我们对其结构复杂性的认知。作为补充研究手段，我们采用冷冻扫描电子显微镜（cryo-scanning electron microscopy, cryo-SEM）对微观结构变化与网络特性进行可视化表征，并结合流变数据开展关联分析。本研究阐明了粘蛋白浓度、环境条件与粘弹性特性间的复杂相互作用，为粘液研究领域作出了重要贡献，并为未来诸多基于粘蛋白的生物材料的相关研究与高端应用奠定了坚实基础。