Antimicrobial Colloidal Silver-Lignin Particles via Ion and Solvent Exchange

Kalle Lintinen, Sanna Luiro, Patrícia Figueiredo, Ekaterina Sakarinen, Zekra Mousavi, Jani Seitsonen, Guillaume N.S. Rivière, Ulriika Mattinen, Matti Niemelä, Päivi Tammela, Monika Österberg, Leena Sisko Johansson, Johan Bobacka, Hélder A. Santos, Mauri A. Kostiainen*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Acid-precipitated lignin nanoparticles with a cationic polymer coating exhibit antibacterial activity when infused with silver. While the use of such particles would be beneficial due to their high antibacterial activity with a low silver content, their production holds steps that are difficult to scale up to inexpensive industrial manufacture. For example, the production of acid-precipitated lignin nanoparticles requires the use of ethylene glycol, which is not easily recycled. Furthermore, the binding of silver to these particles is weak, and thus the particles need to be used rapidly after preparation. Here, we show that with a deprotonation reaction of an organic solution of anhydrous lignin and subsequent ion exchange with silver nitrate and colloid formation by solvent exchange, highly spherical silver carboxylate colloidal lignin particles (AgCLPs) can be prepared. Silver is not released from the particles in deionized water but can be released in physiological conditions, shown by their high antibacterial efficacy with low silver loading. In comparison to lignin nanoparticles with weakly bound silver, AgCLPs have high antibacterial activity even without cationic polyelectrolyte coating, and they retain their antibacterial activity for days. While the rapid depletion of silver from silver-infused lignin nanoparticles can be considered beneficial for some applications, the sustained antibacterial activity of the AgCLPs with ionically bound silver will enable their use in applications where silver nanoparticles have been previously used. Our results demonstrate that CLPs, which can be produced with a closed cycle process on a large scale, can be rapidly and quantitatively functionalized into active materials.

Original languageEnglish
Pages (from-to)15297-15303
Number of pages7
JournalACS Sustainable Chemistry and Engineering
Issue number18
Publication statusPublished - 16 Sep 2019
MoE publication typeA1 Journal article-refereed


  • antibacterial
  • colloid
  • lignin
  • particle
  • silver

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