Membrane-Coated Microsphere Functionalization with Polypeptides

Abstract

Functionalized microspheres made from various materials are widely used for multiple biotechnological purposes. Proteins and peptides are commonly used for microsphere functionalization to leverage their biological functions. However, the function of many proteins is modulated by plasma or organelle membranes; despite this, there is a scarcity of functionalized membrane-coated microspheres for applications that benefit from the presence of membranes. Here, we describe a simple and versatile method to functionalize microspheres of different sizes and materials with a synthetic membrane carrying integrated peptides designed for bioconjugation with other peptides and fully folded proteins. We have validated our method by producing membrane-coated microspheres functionalized with a fluorescent peptide and a DNA-binding protein. Using confocal fluorescence microscopy and optical traps, we demonstrate these functions and the possibility of measuring mechanical forces associated with protein-DNA binding. In addition, we have determined microsphere labeling efficiencies close to 100% by flow cytometry. Our results open the door to the fabrication of multifunctionalized membrane-coated microspheres for an ample range of purposes, and specifically, the study and leverage of protein function that requires or is enhanced by the presence of a lipid bilayer.