Qi, Xu, Jiang, Hu, and Zou (2004) reported that chitosan nanoparticles exhibit higher antibacterial activity against Escherichia coli, Staphylococcus aureus and Salmonella typhimurium than chitosan on account of the special character of the nanoparticles, likely the nanoparticle's larger surface area and higher affinity with bacteria cells, which yields a
quantum-size effect.
Conversely, Sadeghi et al. (2008) reported that chitosan nanoparticles have less inhibition effect on S. aureus than the polymers in free soluble form since nanoparticles have less positive charge available to bind to the negative bacterial cell wall.
Du et al. (2009), reported that chitosan tripolyphosphate nanoparticles
loaded with various metal ions exhibit higher antibacterial
activity against E. coli, Salmonella choleraesuis and S. aureus.