Statistical 3D morphology characterization of vaterite microspheres produced by engineered Escherichia coli

Alex Y.W. Lin, Zong Yen Wu, Alexander J. Pattison, Isaak E. Müller, Yasuo Yoshikuni, Wolfgang Theis, Peter Ercius*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Hollow vaterite microspheres are important materials for biomedical applications such as drug delivery and regenerative medicine owing to their biocompatibility, high specific surface area, and ability to encapsulate a large number of bioactive molecules and compounds. We demonstrated that hollow vaterite microspheres are produced by an Escherichia coli strain engineered with a urease gene cluster from the ureolytic bacteria Sporosarcina pasteurii in the presence of bovine serum albumin. We characterized the 3D nanoscale morphology of five biogenic hollow vaterite microspheres using 3D high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) tomography. Using automated high-throughput HAADF-STEM imaging across several sample tilt orientations, we show that the microspheres evolved from a smaller more ellipsoidal shape to a larger more spherical shape while the internal hollow core increased in size and remained relatively spherical, indicating that the microspheres produced by this engineered strain likely do not contain the bacteria. The statistical 3D morphology information demonstrates the potential for using biogenic calcium carbonate mineralization to produce hollow vaterite microspheres with controlled morphologies. Statement of significance: The nanoscale 3D structures of biomaterials determine their physical, chemical, and biological properties, however significant efforts are required to obtain a statistical understanding of the internal 3D morphology of materials without damaging the structures. In this study, we developed a non-destructive, automated technique that allows us to understand the nanoscale 3D morphology of many unique hollow vaterite microspheres beyond the spectroscopy methods that lack local information and microscopy methods that cannot interrogate the full 3D structure. The method allowed us to quantitatively correlate the external diameters and aspect ratios of vaterite microspheres with their hollow internal structures at the nanoscale. This work demonstrates the opportunity to use automated transmission electron microscopy to characterize nanoscale 3D morphologies of many biomaterials and validate the chemical and biological functionality of these materials.

Original languageEnglish
Article number213711
Number of pages9
JournalBiomaterials advances
Volume156
Early online date27 Nov 2023
DOIs
Publication statusPublished - Jan 2024

Bibliographical note

Funding Information:
This work was supported by the Laboratory Directed Research and Development program (LDRD) at Lawrence Berkeley National Laboratory. This work was partially funded by the US Department of Energy in the program “4D Camera Distillery: From Massive Electron Microscopy Scattering Data to Useful Information with AI/ML.” Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 . Work conducted by the U.S. Department of Energy Joint Genome Institute, a DOE Office of Science User Facility, is supported by the Office of Science of the U.S. Department of Energy operated under Contract No. DE-AC02-05CH11231 .

Publisher Copyright:
© 2023 The Authors

Keywords

  • 3D morphology
  • Biomineralization
  • MICP
  • Scanning transmission electron microscopy
  • Vaterite

ASJC Scopus subject areas

  • Bioengineering
  • Biomaterials
  • Biomedical Engineering

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