Cationic Polyelectrolyte Adsorption onto Anionic Nanoparticles Analyzed with Frequency‐Domain Scanning Fluorescence Correlation Spectroscopy

• DOI: 10.1002/smtd.202401985
• Publication Date: 2025-04-11T05:46:31Z
• Authors: Lucas Oorlynck; Lenny Van Daele; Alina Myslovska; Sarah Goddaer; Sumit Sumit; Yera Ye. Ussembayev; Katrien Remaut; Iwan Moreels; Peter Dubruel; Filip Strubbe

AbstractAn improved small‐circle scanning fluorescence correlation spectroscopy (sFCS) technique is introduced by combining acousto‐optical laser scanning with fitting the autocorrelation function in the frequency domain. The technique is validated using both simulation and experimental data on various fluorescent nanoparticles, including polystyrene beads, CdSe/CdS quantum dots, and lipid nanoparticles. Then, the sFCS method is used to investigate the adsorption of in‐house synthesized poly(2‐guanidinoethyl methacrylate) (PGUMA) polymers on polystyrene beads as a model system for polymer‐coated particles in biomedical and gene delivery applications. Using the particle diffusion and illumination beam waist values obtained from our sFCS analysis, regions of polymer concentrations are identified where polymer‐particle complexes remain stable. An increase in hydrodynamic size is also observed with the molecular mass of the adsorbed polymer. Beyond quantifying polymer‐particle stability and hydrodynamic size, the sFCS technique offers the advantage of not requiring a time‐consuming calibration step for the measurement volume, unlike standard FCS.