Assembly and stability of lipid-coated silver nanoparticles: a combined UV-Vis / multispectral iSCAT study
Embargo Date
2027-05-27
OA Version
Citation
Abstract
Although silver (Ag) nanoparticles (NPs) possess superb optical properties, their insufficient chemical stability and susceptibility to oxidative etching preclude their application in many complex biosensing environments. Lipid coating represents a promising strategy to enhance the stability of AgNPs by providing a biocompatible passivation layer. However, the successful assembly of these hybrid membranes depends on several thermodynamic parameters that require rigorous optimization. While macroscopic stability assays, such as bulk UV-Vis spectroscopy, are essential for this performance optimization, these conventional ensemble-based strategies often obscure the underlying structural heterogeneity of the nanostructures and can confound genuine chemical etching with nanoparticle aggregation.In this thesis, we overcome these limitations by employing custom-built multispectral interferometric scattering (iSCAT) microscopy to quantify the oxidative etching kinetics of lipid-coated silver nanoparticles (L-AgNPs) at the single-particle level. To achieve this, a robust computational and analytical pipeline was developed, successfully translating complex, non-monotonic optical contrast signals into precise, real-time physical diameters using a polynomial calibration model and physical constraint algorithms.
By tracking the real-time etching trajectories of individual L-AgNPs, we resolve a distinct bimodal behavior that is completely undetectable via bulk UV-Vis spectroscopy. Rather than degrading uniformly, the particles either undergo rapid, catastrophic etching or remain kinetically inert. This indicates that the protection provided by the membrane is an "all-or-nothing" phenomenon governed by nanoscale defect probabilities. Furthermore, we demonstrate that the probability of achieving complete AgNP stabilization is highly dependent on the temperature during the assembly process. Maintaining the lipid formulation in a fluid, liquid-crystalline phase during both initial liposome formation and final L-AgNP self-assembly maximizes the dynamic rearrangement of the lipids, thereby optimizing the yield of stable, fully protected nanohybrids. Ultimately, these findings highlight the unparalleled power of single-particle interferometric imaging for characterizing the true structural integrity of hybrid nanomaterials and guiding their rational design.
Description
2026