Vesicles made from functionally folded, globular proteins that perform specific biological activities, such as catalysis, sensing, or therapeutics, show potential applications as artificial cells, microbioreactors, or protein drug delivery vehicles. The mechanical properties of vesicle membranes, including the elastic modulus and hardness, play a critical role in dictating the stability and shape transformation of the vesicles under external stimuli triggers. Herein, we have developed a strategy to tune the mechanical properties and integrity of globular protein vesicle (GPV) membranes of which building molecules are recombinant fusion protein complexes: A mCherry fused with an acidic leucine zipper (mCherry-ZE) and a basic leucine zipper fused with an elastin-like polypeptide (ZR-ELP). To control the mechanical properties of GPVs, we introduced a nonstandard amino acid (para-azidophenylalanine (pAzF)) into the ELP domains (ELP-X), which enabled the creation of crosslinked vesicles under ultraviolet (UV) irradiation. Crosslinked GPVs made from mCherry-ZE/ZR-ELP-X complexes presented higher stability than noncrosslinked GPVs under hypotonic osmotic stress. The degree of swelling of GPVs increased as less crosslinking was achieved in the vesicle membranes, which resulted in the disassembly of GPVs into membraneless coacervates. Nanoindentation by atomic force microscopy (AFM) confirmed that the stiffness and Young's elastic modulus of GPVs increase as the blending molar ratio of ZR-ELP-X to ZR-ELP increases to make vesicles. The results obtained in this study suggest a rational design to make GPVs with tunable mechanical properties for target applications by simply varying the blending ratio of ZR-ELP and ZR-ELP-X in the vesicle self-assembly.
Bibliographical noteFunding Information:
This research was financially supported by Prof. J.Y.’s startup funds (19030100-211-CRRNT-00128948 and 19030100-211-CRRNT-00128694) provided by the Department of Chemical Engineering and Herbert Wertheim College of Engineering at the University of Florida. A portion of this work was performed in the University of Florida’s McKnight Brain Institute at the National High Magnetic Field Laboratory’s Advanced Magnetic Resonance Imaging and Spectroscopy (AMRIS) Facility, which is supported by the US National Science Foundation Cooperative Agreement No. DMR-1644779 and the State of Florida. Some NMR spectra were acquired using a unique 1.5 mm high-temperature superconducting cryogenic probe developed with support from the US National Institutes of Health award R01EB009772. Mass spectra were obtained from the Mass Spectrometry Research and Education Center at the University of Florida, funded from NIH S10 OD021758-01A1.
Copyright © 2020 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Polymers and Plastics
- Materials Chemistry