Boosting wet adhesion of a genetically engineered glue from supercharged polypeptides employing a combination of computational and experimental methods

尽管在身体动态和潮湿环境中的粘附在外科等临床应用中具有重要意义，但它仍然是一个技术挑战。天然海洋生物为开发具有高机械稳定性和高灵活性的水下胶提供了灵感，这种胶可以在动态流体和表面存在的情况下抵抗持续的机械应力和高离子强度以及pH值。尽管有复杂的生物机械和化学，海洋生物中粘附的主要潜在机制是基于复杂的凝聚——由静电相互作用驱动，随后成熟为固相——由短程相互作用驱动。复合凝聚发生在两种带相反电荷的聚电解质混合时，它们经历了液-液相变。合成的聚电解质和天然或重组蛋白已被广泛研究来模拟这种自然机制。然而，在环境条件下，它们往往不能提供很强的附着力。这主要是由于结构可调性较低，包括电荷密度和分布或分子相互作用的精确调节等，这阻碍了我们在分子尺度上对粘附的理解。为了克服这些挑战，我们引入了一系列序列定义的增压多肽（SUPs），并研究了增强其粘合性能的结构要求。sup由一个重复的氨基酸序列组成，在每个重复序列中包含一个带电残基（X) (VPGXG)n X：赖氨酸或精氨酸）。我们的目标是展示改变sup的结构和组成如何影响其机械性能，并优化这些特性以提高水下附着力。这需要在不同类型的分子相互作用之间在几个时间和长度尺度上保持微妙的平衡。该项目分为三个主要目标：(1)合成sup并在其结构中编码不同类型的分子相互作用；(2)在宏观尺度上研究基于sup的复合凝聚物的粘附性能；(3)在分子水平上阐明粘附机制，并通过合成、表征和计算机模拟之间的重复反馈来改善粘附。我们的目标是精确控制sup的分子参数，包括摩尔质量，电荷密度和电荷梯度，拓扑结构以及化学，以建立一个全面的模型并预测湿粘附性能。

Although adhesion in dynamic and wet environments of the body is of prime importance in clinical applications such as surgery, it is still a technical challenge. Natural marine organisms have provided inspiration to develop underwater glues that can amalgamate high mechanical stability and high flexibility to resist continuous mechanical stresses and high ionic strength as well as pH in the presence of dynamic fluids and surfaces. In spite of the intricate biological machinery and chemistry, the primary underlying mechanism for adhesion in marine organisms is based on complex coacervation – driven by electrostatic interactions, followed by maturation into a solid phase – driven by short-range interactions. Complex coacervation occurs upon mixing of two oppositely charged polyelectrolytes, which undergo a liquid-liquid phase transition. Synthetic polyelectrolytes and natural or recombinant proteins have been extensively investigated to mimic this natural mechanism. However, they often failed to deliver strong adhesion strengths under ambient conditions. This is mainly due to the low degree of structural tunability, including charge density and distribution or the precise adjustment of molecular interactions etc., which imped our understanding about adhesion at the molecular scale. To overcome these challenges, we introduce a family of sequence-defined supercharged polypeptides (SUPs) and investigate the structural requirements to enhance their adhesive performance. SUPs consist of a repetitive amino acid sequence containing one charged residue (X) in every repeat ((VPGXG)n X:lysine or arginine). Our goal is to show how altering the architecture and composition of SUPs affect their mechanical properties and to optimize these features to improve underwater adhesion. This requires a delicate balance, at several time- and length-scales, between different types of molecular interactions. The project is divided into three main objectives: (1) synthesis of SUPs and encoding different types of molecular interactions in their structures, (2) investigation of adhesion performance of SUP-based complex coacervates at macroscopic scale and (3) elucidating the adhesion mechanism at the molecular level and improving the adhesion by a repetitive feedback between synthesis, characterization and computer simulation. We are aiming for precisely controlling the molecular parameters of SUPs including molar mass, charge density and charge gradients, topology as well as chemistry to develop a comprehensive model and to predict the wet adhesion properties.