Tethered lipid bilayers within nanostructured porous silicon: A biosensing platform for optical monitoring of membrane-associated processes

The importance of biological membranes in cell function led to tremendous interest in the development of membrane-like model systems serving as platforms for studying cell-membrane associated processes. These platforms can provide novel methodologies for basic biological and biophysical research and for the development of new biotechnological tools.

In the presented work, a novel and facile approach for the construction of tethered supported lipid bilayer (SLB) within an oxidized porous silicon (PSiO₂) nanostructure is demonstrated. SLB assembly is a two-step process, in which the lipid monolayer is tethered to the PSiO₂ inner surface, followed by self-assembly of the lipid bilayer in response to environment exchange. The SLB formation within the nanostructure was confirmed by fluorescence resonance energy transfer, and their propeties were characterized by environment-sensitive fluorophores. The unique optical properties of the PSiO₂ scaffold are employed to demonstrate the use of our platform for real-time and label-free monitoring of the interactions between antimicrobial peptides (AMPs) and model lipid bilayer membrane via reflective interferometric Fourier transform spectroscopy (RIFTS) method. Several SLB-PSiO₂ systems were constructed and characterized in terms of their detailed nanostructure, surface chemistry, bilayer nature (local environment polarity and micro-viscosity), and optical response to different AMPs, such as aurin and magainin I. Next, the SLB composition was successfully adjusted to mimic the outer membrane of relevant model bacteria, specifically, E. coli, and its interactions with model AMPs were studied optically using RIFTS.