W. Yang, J. Xiao, B. Yang, G. Mathew, A. H. Schäfer, M. Hirtz

Adv. Mater. Interfaces 11 (2024) 2400200

The characterization of phospholipid membrane permeability for small molecules is crucial for many applications in drug discovery and biomedical research in general. Here, chemosensor-laden vesicles offer an attractive platform for permeability assays. In this work, the stability of immobilized chemosensor-filled vesicles is explored on anti-fouling polymer brush surfaces for potential use in monitoring small molecule membrane permeability. The study focuses on the development of a method for immobilizing sensor-loaded vesicles into arbitrary patterns on surfaces and characterizing their stability under changing temperatures and compositions. As substrate to enable intact, long-term stable vesicle immobilization reactive polymer brushes with anti-fouling properties are used. Utilizing microchannel cantilever spotting, biotin moieties are introduced on the polymer brush surface, enabling stable tethering of vesicles through streptavidin-biotin interactions. The immobilized vesicles are monitored through fluorescence microscopy for their response to analytes under changing environmental parameters and vesicle composition. A higher stability of immobilized vesicles compared to free-floating ones is observed, with permeability only at elevated temperatures. By tuning vesicle compositions, permeability at lower temperatures can be raised again. Overall, the study provides insights into a novel approach for vesicle immobilization, showcasing the potential of surface-bound vesicles for applications in microfluidic systems and as biosensors in various assays.