Cardellini Jacopo, De Santis Ilaria, Lio Giuseppe Emanuele, Brucale Marco, Valle Francesco, Catani Virginia, Mastrolia Ilenia, Calabria Marta, Dominici Massimo, Zendrini Andrea, Radeghieri Annalisa, Paolini Lucia, Bergese Paolo, Caselli Lucrezia, Berti Debora, Montis Costanza
Department of Chemistry "Ugo Schiff", University of Florence, Sesto Fiorentino, 50019 Florence, Italy.
CSGI, Center for Colloid and Surface Science, 50019 Florence, Italy.
J Am Chem Soc. 2025 Jun 11;147(23):20008-20022. doi: 10.1021/jacs.5c05189. Epub 2025 May 30.
Assembly of plasmonic nanoparticles (NPs) generates unique optical properties through coupling of the localized surface plasmon resonance (LSPR) of individual NPs. However, precisely controlling and monitoring how mesoscale assembly dictates final optical properties remain key challenges in designing advanced plasmonic materials. Here, we introduce "nanoplasmonic isosbestics" as optical descriptors of the mesoscale organization of gold nanoparticles (AuNPs) on soft templates. Unlike isosbestic points in molecular spectroscopy, which describe chemical equilibria, our numerical simulations demonstrate that nanoplasmonic isosbestics emerge from the coexistence of individual AuNPs and AuNP clusters, where the interparticle spacing determines the isosbestic wavelength. By templating AuNP assembly onto synthetic free-standing lipid bilayers with tunable membrane rigidity, we experimentally achieve precise control over interparticle spacing and prove that it is mirrored by univocal modulation of the isosbestic wavelength. This provides a fundamental understanding of the structure-function relationship in plasmonic systems, linking, for the first time, nanoplasmonic isosbestics to interparticle spacing and equilibrium structure in plasmonic assemblies. On the analytical perspective, nanoplasmonic isosbestics provide noninvasive optical fingerprints of the templates, opening to appealing applications. As a proof of concept, we apply this approach to profile the stiffness of two extracellular vesicle (EVs) classes─mesenchymal stem cell (MSC)-derived and red blood cell-derived EVs─both recognized for their biological and translational potential.
等离子体纳米颗粒（NPs）的组装通过单个NPs的局域表面等离子体共振（LSPR）耦合产生独特的光学性质。然而，精确控制和监测中尺度组装如何决定最终光学性质仍然是设计先进等离子体材料的关键挑战。在这里，我们引入“纳米等离子体等吸收点”作为软模板上金纳米颗粒（AuNPs）中尺度组织的光学描述符。与描述化学平衡的分子光谱中的等吸收点不同，我们的数值模拟表明，纳米等离子体等吸收点源于单个AuNPs和AuNP簇的共存，其中粒子间间距决定等吸收波长。通过将AuNP组装模板化到具有可调膜刚性的合成独立脂质双层上，我们通过实验实现了对粒子间间距的精确控制，并证明它由等吸收波长的明确调制反映出来。这提供了对等离子体系统中结构-功能关系的基本理解，首次将纳米等离子体等吸收点与等离子体组装中的粒子间间距和平衡结构联系起来。从分析角度来看，纳米等离子体等吸收点提供了模板的非侵入性光学指纹，开启了有吸引力的应用。作为概念验证，我们应用这种方法来分析两种细胞外囊泡（EVs）——间充质干细胞（MSC）衍生的和红细胞衍生的EVs——的硬度，这两种EVs都因其生物学和转化潜力而受到认可。
