In Vitro Characterization and Real-Time Label-Free Assessment of the Interaction of Chitosan-Coated Niosomes with Intestinal Cellular Monolayers

In vitro cell-based characterization methods of nanoparticles are generally static and require the use of secondary analysis techniques and labeling agents. In this study, bare niosomes and chitosan-coated niosomes (chitosomes) and their interactions with intestinal cells are studied under dynamic conditions and without fluorescent probes, using surface plasmon resonance (SPR)-based cell sensing. Niosomes and chitosomes were synthesized by using Tween 20 and cholesterol in a 15 mM:15 mM ratio and then characterized by dynamic light scattering (DLS). DLS analysis demonstrated that bare niosomes had average sizes of ∼125 nm, polydispersity index (PDI) below 0.2, and a negative zeta (ζ)-potential of −35.6 mV. In turn, chitosomes had increased sizes up to ∼180 nm, with a PDI of 0.2-0.3 and a highly positive ζ-potential of +57.9 mV. The viability of HT29-MTX, Caco-2, and Caco-2/HT29-MTX cocultured cells showed that both niosomes and chitosomes are cytocompatible up to concentrations of 31.6 μg/mL for at least 240 min. SPR analysis demonstrated that chitosomes interact more efficiently with HT29-MTX, Caco-2, and Caco-2/HT29-MTX cocultures compared to bare niosomes. The resulting SPR measurements were further supported by confocal microscopy and flow cytometry studies, which demonstrated that this method is a useful complementary or even alternative tool to directly characterize the interactions between niosomes and in vitro cell models in label-free and real-time conditions.