Nanoparticle tracking analysis as a process analytical tool for characterising magnetosome preparations

Alfred Fernandez-Castane*, Tim W. Overton, Hong Li, Stephan Joseph, Moritz Ebeler, Matthias Franzreb, Daniel Bracewell, Owen R.T. Thomas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Nanoparticle Tracking Analysis (NTA) has been employed to measure the particle concentration and size distribution of magnetosomes extracted and purified from Magnetospirillum gryphiswaldense MSR-1, and then exposed to probe ultrasonication for various times, or 1% (w/v) sodium dodecyl sulphate (SDS) for 1 h. Particle concentration increased 3.7-fold over the first 15 min of ultrasonication (from 2 × 108 to >7.3 × 108 particles mL−1), but fell steeply to ∼3.6 × 108 particles mL−1 after 20 min. NTA of untreated magnetosome preparation confirmed a wide particle distribution dominated by larger species (D[1,0] = 312 nm; Dn50 = 261 nm; mode = 243 nm) with no particles in the size range of isolated single magnetosomes. After 5 min of ultrasonication the whole particle size distribution shifted to smaller size (D[1,0] = 133 nm; Dn50 = 99 nm; mode = 36 nm, corresponding to individual magnetosomes), but longer treatment times (15 and 20 min) reversed the previous transition; all characteristic numbers of the particle size distributions increased and very few small particles were detected. Side-by-side comparison of NTA and TEM sizing data revealed remarkable similarity at low ultrasonication times, with both showing single magnetosomes accounted for ∼30% population after 5 min. Exposure of magnetosomes to SDS resulted in a ∼3-fold increase in particle concentration to 5.8 × 108 particles mL−1, narrowing of the size distribution and gross elimination of particles below 60 nm. We conclude that NTA is a rapid cost-effective technique for measuring particle concentration, size distribution and aggregation state of magnetosomes in solution.
Original languageEnglish
Pages (from-to)426-434
Number of pages9
JournalFood and Bioproducts Processing
Early online date26 Mar 2021
Publication statusPublished - May 2021

Bibliographical note

© 2021, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International


  • Biomanufacturing
  • Bioprocessing
  • Magnetic nanoparticles
  • Nanobiotechnology
  • Process analytical technology
  • Quality control


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