Nanoparticles of copper salts by in-situ surface modification and their effectiveness in antibacterial activity

Diseases caused by microorganism increasingly lead to mortality in humans and high costs of health care system. The microbial resistance to existing active substances is another source of problems related to providing... [ view full abstract ]

Diseases caused by microorganism increasingly lead to mortality in humans and high costs of health care system. The microbial resistance to existing active substances is another source of problems related to providing hygienic conditions at  hospitals. Although silver nanoparticles show promising results in providing high antimicrobial property, it is expensive. Another metal with high antimicrobial activity is Cu and its low price makes it a considerable candidate for new materials.

In this study, the particles of Cu salts of CuSO₄.Cu(OH)₂ and CuCO₃.Cu(OH)₂ were produced by the reaction of Cu ions with proper anions in the presence of sodium lignosulfonate (LS) as a in-situ surface modifier. The obtained Cu salt-particles were analyzed by AAS and characterized by DLS, FT-IR, XRD and TEM methods. The minimum inhibitory concentration (MIC) method was used to investigate their antibacterial activity.

As the ratio of Cu to LS in a solution with the Cu concentration  of 3 weight percentage for CuSO₄.Cu(OH)₂ synthesis is increased to from 0 to 3 stepwise, the particle size goes from 1-2 micrometer down to 100 nm. When the Cu concentration at the ratio of C to LS of 3 is lowered to 1 percentage, particles with the size of around 30 nm are obtained and are spherical (Figure 1). In the CuCO₃.Cu(OH)₂ synthesis, nanoparticles are produced without the use of in-situ surface modifier although the obtained nanoparticles are highly agglomerated in the range of micrometer.  As LS is added to the solution at the increasing ratio, nanoparticles become agglomerate-free, their size goes down to 30 nm and have rod-like shape (Figure 2). The minimum inhibitory concentration (MIC) of the synthesized samples of Cu salts are tested against E. Coli and the solutions of the sources of Cu ions are served as reference. MIC values of samples with smallest sizes of Cu salt particles are lowest (0.55 µg/mL and 0.25 µg/mL for CuSO₄.Cu(OH)₂ and CuCO₃.Cu(OH)₂ respectively), which are 5 to 12 folds lower than of solution containing the same amount of Cu ions.  With an increase in the amount of LS, the MIC values within the same type of Cu salt-particles diminish.