# The effect of PEGylation on surface tethering of liposomes via DNA nanotechnology

## TL;DR

This study explores how PEGylation affects the surface tethering of DNA-liposomes, revealing that PEG can either block or enhance binding depending on the liposome composition.

## Contribution

The study systematically investigates the interplay between PEGylation and DNA-mediated liposome tethering, offering insights into optimizing liposome formulations.

## Key findings

- Low PEG content (0%-20%) reduced liposome size due to repulsive forces.
- High PEG content (30%-50%) increased polydispersity.
- PEGylation's effect on DNA-liposome surface binding depends on membrane composition.

## Abstract

Polyethylene glycol (PEG) is widely used in liposome formulation due to its blocking properties and ability to prolong circulation in vivo to create biomimetic liposomes and drug delivery devices. Similarly, membrane-embedded DNA nanotechnology is increasingly used to modulate cellular behaviour and communication. However, there is a gap in knowledge in how PEG-lipid formulations can be optimized for both liposome properties and control of selective DNA hybridization. To address this, we systematically investigated the effect of liposome PEG content on DNA mediated tethering of liposomes to glass surfaces. We formulated liposomes of two different lipid compositions (DOPE/DOPC or DPhPC), with varying amounts of PEGylated lipid (0%–50%). We measured the effect of increased PEG content on liposome size and polydispersity through dynamic light scattering (DLS). Small amounts of PEG (0%–20%) introduced repulsive forces that reduced size, while large amounts of PEG (30%–50%) increased polydispersity. PEG-liposomes were then decorated with cholesterol-DNA strands and labeled with either intercalating lipid dyes or fluorescently labeled lipids. Binding to surfaces via complementary DNA strands was quantified using total internal reflection fluorescence (TIRF) microscopy. We found that PEGylation of DNA-liposomes could either block or enhance surface binding, depending on the amount of PEG. DNA-liposomes with reduced surface binding included DPhPC/DiD with 10% or 20% PEG-lipid. In contrast, DNA-liposome surface binding increased for DOPE/DOPC/DiD with increasing PEG%. This study highlights that while PEG can act to stabilize liposome formulations, its ability to block specific DNA-binding interactions on membranes is variable and dependent on membrane composition.