The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions

Simo Kalliola; Eveliina Repo; Varsha Srivastava; Juha P Heiskanen; Juho Antti Sirviö; Henrikki Liimatainen; Mika Sillanpää

doi:10.1016/j.colsurfb.2017.02.025

The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions

Colloids Surf B Biointerfaces. 2017 May 1:153:229-236. doi: 10.1016/j.colsurfb.2017.02.025. Epub 2017 Feb 21.

Authors

Simo Kalliola¹, Eveliina Repo², Varsha Srivastava², Juha P Heiskanen³, Juho Antti Sirviö⁴, Henrikki Liimatainen⁴, Mika Sillanpää⁵

Affiliations

¹ Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland. Electronic address: simo.kalliola@lut.fi.
² Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland.
³ Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014, Finland.
⁴ Fibre and Particle Engineering Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Finland.
⁵ Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland; Department of Civil and Environmental Engineering, Florida International University, Miami, FL-33174, USA.

PMID: 28258031
DOI: 10.1016/j.colsurfb.2017.02.025

Abstract

In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca²⁺ ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca²⁺ ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH₃⁺ and COO^- groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances.

Keywords: Calcium; Carboxymethyl chitosan; Nanoparticle; pH sensitive.

MeSH terms

Calcium / chemistry*
Chitosan / analogs & derivatives*
Chitosan / chemistry
Cross-Linking Reagents / chemistry*
Hydrogen-Ion Concentration
Ions / chemistry
Nanoparticles / chemistry*
Particle Size
Surface Properties

Substances

Cross-Linking Reagents
Ions
carboxymethyl-chitosan
Chitosan
Calcium