Directly visualizing individual polyorganophosphazenes and their single-chain complexes with proteins

Published

March 14, 2024

Author(s)

Raman Hlushko, Vivek Prabhu, Alexander Andrianov

Abstract

Polyorganophosphazenes are water-soluble macromolecules with immunoadjuvant activity that self-assemble with proteins to enable biological functionality. Direct imaging by cryogenic electron microscopy uncovers the coil structure of those highly charged macromolecules. Here, we successfully visualize individual polymer chains within the vitrified state in the absence of additives for contrast enhancement which is attributed to the high mass contrast of the inorganic backbone. Upon assembly with proteins, multiple protein copies bind at the single polymer chain level resulting in structures reminiscent of compact spherical complexes or stiffened coils. The outcome depends on protein characteristics and cannot be deduced by commonly used characterization techniques, such as light scattering, thus revealing direct morphological insights crucial for understanding biological activity. Atomic force microscopy supports the morphology outcomes while advanced analytical techniques confirm protein-polymer binding. The chain visualization methodology provides tools for gaining insights into the processes of supramolecular assembly and mechanistic aspects of polymer-enabled vaccine delivery.

Citation

Nature Communications Materials

Volume

5

Pub Type

Journals

Download Paper

https://doi.org/10.1038/s43246-024-00476-6

Local Download

Keywords

polyorganophosphazene, polyelectrolyte, antigenic protein, complexation, vaccine, cryogenic electron microscopy

Citation

Hlushko, R. , Prabhu, V. and Andrianov, A. (2024), Directly visualizing individual polyorganophosphazenes and their single-chain complexes with proteins, Nature Communications Materials, [online], https://doi.org/10.1038/s43246-024-00476-6, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956626 (Accessed October 14, 2025)