Silver-Ion-Exchanged Nanostructured Zeolite X as Antibacterial Agent with Superior Ion Release Kinetics and Efficacy against Methicillin-Resistant Staphylococcus aureus

Abstract

As antibiotic resistance continues to be a major public health problem, antimicrobial alternatives have become critically important. Nanostructured zeolites have been considered as an ideal host for improving popular antimicrobial silver-ion-exchanged zeolites, because with very short diffusion path lengths they offer advantages in ion diffusion and release over their conventional microsized zeolite counterparts. Herein, comprehensive studies are reported on materials characteristics, silver-ion release kinetics, and antibacterial properties of silver-ion-exchanged nanostructured zeolite X with comparisons to conventional microsized silver-ion-exchanged zeolite (∼2 μm) as a reference. The nanostructured zeolites are submicrometer-sized aggregates (100-700 nm) made up of primary zeolite particles with an average primary particle size of 24 nm. The silver-ion-exchanged nanostructured zeolite released twice the concentration of silver ions at a rate approximately three times faster than the reference. The material exhibited rapid antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentration (MIC) values ranging from 4 to 16 μg/mL after 24 h exposure in various growth media and a minimum bactericidal concentration (MBC; >99.9% population reduction) of 1 μg/mL after 2 h in water. While high concentrations of silver-ion-exchanged nanostructured zeolite X were ineffective at reducing MRSA biofilm cell viability, efficacy increased at lower concentrations. In consideration of potential medical applications, cytotoxicity of the silver-ion-exchanged nanostructured zeolite X was also investigated. After 4 days of incubation, significant reduction in eukaryotic cell viability was observed only at concentrations 4-16-fold greater than the 24 h MIC, indicating low cytotoxicity of the material. Our results establish silver-ion-exchanged nanostructured zeolites as an effective antibacterial material against dangerous antibiotic-resistant bacteria.

Metal‐Based Nanomaterials in Biomedical Applications: Antimicrobial Activity and Cytotoxicity Aspects

“…Silver atoms can react with enzymes containing thiol (SH) functional groups to produce stable SAg bonds that result in inactivation of cell membrane enzymes responsible for transmembrane energy generation and ion transport in methicillin‐resistant S. aureus (MRSA). [ 132 ] Respiratory enzymes present on bacterial membranes may also be altered by metallic nanomaterials, resulting in the production of ROS that react with proteins and lipids on the cell membrane. [ 133 ]…”

Silver bullets: A new lustre on an old antimicrobial agent

“…Particles may reside on the sub-mucosal region of the intestine and be absorbed into the lymphatic or the capillary system. (Chen andSchluesener 2008, Eckhardt, Brunetto et al 2013) Female urogenital: silver impregnated sanitary napkins for prevention of odor and infections. (Brandtzaeg 1997) Brain: silver nanoparticles and colloidal formulations in the blood stream circulate to the blood-brain barriers.…”

Superior ion release properties and antibacterial efficacy of nanostructured zeolites ion-exchanged with zinc, copper, and iron

“…In our previous work, 16 we demonstrated that Ag + -ion-exchanged highly-crystalline nanostructured zeolite X offers superior release kinetics and rapid antibacterial activity compared to their microsized counterparts. 16 For example, Demirci et al .…”

“…11 Indeed, zeolites loaded with antimicrobial metal ions consistently demonstrate activity against a broad spectrum of microorganisms. 12–16 Ion release from zeolites occurs when the ions in zeolite diffuse through the zeolite body to the external surface, so the increased surface area and nanoscopic dimension of nanozeolites are desirable for an enhanced ion release performance. The antimicrobial applications of the nanozeolites are particularly timely in the age of continuously emerging antimicrobial resistance, where the fight to prevent the spread of infection is critical and cannot be understated.…”