Dipartimento di Scienze Chimiche, Università di Padova, I-35131 Padova, Italy.
Istituto Nanoscienze-CNR-NANO, Center S3, via G. Campi 213/A, I-41125 Modena, Italy.
Nanotechnology. 2021 Feb 26;32(9):095702. doi: 10.1088/1361-6528/abc6dc.
A wide class of biosensors can be built via functionalization of gold surface with proper bio conjugation element capable of interacting with the analyte in solution, and the detection can be performed either optically, mechanically or electrically. Any change in physico-chemical environment or any slight variation in mass localization near the surface of the sensor can cause differences in nature of the transduction mechanism. The optimization of such sensors may require multiple experiments to determine suitable experimental conditions for the immobilization and detection of the analyte. Here, we employ molecular modeling techniques to assist the optimization of a gold-surface biosensor. The gold surface of a quartz-crystal-microbalance sensor is functionalized using polymeric chains of poly(ethylene glycol) (PEG) of 2 KDa molecular weight, which is an inert long chain amphiphilic molecule, supporting biotin molecules (bPEG) as the ligand molecules for streptavidin analyte. The PEG linkers are immobilized onto the gold surface through sulphur chemistry. Four gold surfaces with different PEG linker density and different biotinylation ratio between bPEG and PEG, are investigated by means of state-of-the art atomistic simulations and compared with available experimental data. Results suggest that the amount of biotin molecules accessible for the binding with the protein increases upon increasing the linkers density. At the high density a 1:1 ratio of bPEG/PEG can further improve the accessibility of the biotin ligand due to a strong repulsion between linker chains and different degree of hydrophobicity between bPEG and PEG linkers. The study provides a computaional protocol to model sensors at the level of single molecular interactions, and for optimizing the physical properties of surface conjugated ligand which is crucial to enhance output of the sensor.
可以通过将适当的生物共轭元素功能化到金表面上来构建广泛的生物传感器类别，这些元素能够与溶液中的分析物相互作用，并且可以通过光学、机械或电学方式进行检测。物理化学环境的任何变化或传感器表面附近质量定位的任何微小变化都可能导致转换机制的性质发生差异。这种传感器的优化可能需要进行多次实验，以确定适合分析物固定化和检测的实验条件。在这里，我们使用分子建模技术来协助优化金表面生物传感器。石英晶体微天平传感器的金表面通过分子量为 2 kDa 的聚乙二醇 (PEG) 的聚合链进行功能化，PEG 是一种惰性长链两亲分子，支持生物素分子（bPEG）作为链霉亲和素分析物的配体分子。PEG 接头通过硫化学固定在金表面上。通过最先进的原子模拟研究了具有不同 PEG 接头密度和 bPEG 与 PEG 之间不同生物素化比的四种金表面，并与可用的实验数据进行了比较。结果表明，随着接头密度的增加，可用于与蛋白质结合的生物素分子的数量增加。在高密度下，bPEG/PEG 的比例为 1:1 可以进一步提高生物素配体的可及性，因为接头链之间的强烈排斥和 bPEG 与 PEG 接头之间不同的疏水性导致了这种情况。该研究提供了一种计算方案，可用于在单个分子相互作用的水平上对传感器进行建模，并优化表面共轭配体的物理性质，这对于增强传感器的输出至关重要。
