Antibiotic loading and development of antibacterial capsules by using porous CaCO3 microparticles as starting material

Porous calcium carbonate (CaCO3) particles have been shown to be highly advantageous for biological applications, mainly due to their large surface area and their stability in physiological media. Also, developing appropriate antibacterial materials presenting the benefits of non-formation of harmful compounds is of major interest. Two characteristics of CaCO3 particles were investigated herein: (i) antibiotic-loading capacity and (ii) the possibility of using CaCO3 particles as a template for the fabrication of biocapsules presenting inherent antibacterial capacity. The particles were tested against two representative pathogenic bacteria (Staphylococcus aureus and Escherichia coli). On one hand, a method for antibiotic (namely penicillin, ampicillin and ciprofloxacin) loading inside calcium carbonate particles was developed and antibacterial activity was investigated. Encapsulation efficiency and loading content were 95% and 5%, respectively. We showed that antibiotics prevented bacterial growth within 2 h, with no evidence of bacterial regrowth within 16 h; bactericidal effects were also observed. On the other hand, the self-assembly of charged polysaccharides, namely chitosan (chi+) and dextran sulfate (dex−), were assessed on calcium carbonate microparticles used as a sacrificial matrix. During bacterial growth in a liquid medium, an inhibitory effect of these particles was observed, i.e. Staphylococcus aureus (Gram-positive) (from 16.3% to 48.8% for (chi+/dex−)n-chi+ coated CaCO3 materials and from 41.9% to 93.0% for (chi+/dex−)n-chi+ capsules) and Escherichia coli (Gram-negative) (from 18.2% to 45.5% for (chi+/dex−)n-chi+ coated CaCO3 materials and from 40.0% to 89.1% for (chi+/dex−)n-chi+ capsules). Staining with acridine orange highlighted the bactericidal effect of the designed particles. These findings demonstrate the excellent potential of using calcium carbonate particles in antibiotic therapy as a starting point for the development of smart materials.