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    Biomaterials

    Assessment of the susceptibility of Clinical Bacterial Strains to Copper and Zinc Nanoparticles

    (C-82) Assessment of the susceptibility of Clinical Bacterial Strains to Copper and Zinc Nanoparticles

    Friday, October 13, 2023
    9:30 AM – 10:30 AM PDT
    Location: Exhibit Hall - Row C - Poster # 82
    Introduction::

    The most prevalent complication associated with hospitalization is known as hospital acquired infections (HAI). According to the Center of Disease Control (CDC), roughly 1 in 31 patients will develop HAI while getting treated in a hospital (1)These infections are acquired associated with complications caused by bacterial species present in clinical settings such as Staphylococcus aureus and Pseudomonas aeruginosa when a medical device such as a catheter is implanted into a patient for an extended period (2). Current therapies for HAIs include the usage of antibiotics and fluid resuscitation (3). Integrating metals with antibacterial effects into these existing therapies could prove to be more efficient at eradicating bacteria. Metals generate reactive oxygen species to promote apoptosis (4). The purpose of this research project is to compare the impact of zinc and copper nanoparticle solutions to clinical strains of CDC AR Isolate Bank Difficult-to-detect Staphylococcus aureus harboring mecA 0977 and 1000 and Pseudomonas aeruginosa 0254 and 0256. The mechanism by which these metals interact with the tested clinical strains in vitro allows for the assessment of how the solutions tested affect their viability across various concentrations and conditions. This research, when finalized, will provide insight as to which metal; zinc oxide or copper, has a greater impact on preventing complications associated with bacterial infections.



    Materials and Methods:: The clinical strains used in this study are CDC AR Isolate Bank difficult-to-detect Staphylococcus aureus 0977 and 1000, and CDC Pseudomonas aeruginosa 0256 and 0264 and were acquired from the Centers for Disease Control and Prevention (Atlanta, GA). These strains were chosen since both S,aureus 0977 and P.aeruginosa 0256 only hav 1 drug resistant factor, whereas S.aureus 1000 and P.aeruginosa 0264 have 3 drug resistant factors. Copper nanoparticles (Cu) are 99.9%, 40-60 nm and zinc oxide nanoparticles (ZnO) are 99.8%, 10-30 nm acquired from SkySpring Nanomaterials, Inc. (Houston, Tx). The nanoparticle(NP) solutions Staphylococcus aureus strains are 0.005 wt% Cu NPs or ZnO NPs in sterile phosphate buffered saline (PBS).The NP solutions Pseudomonas aeruginosa strains are 0.005 wt% Cu NPs or 0.032 wt% ZnO NPs in sterile PBS. The bacterial growth curve experiments use double dilutions; each dilution halves the prior concentration, of the NP solutions starting at 1120 μg/mL for Cu, and 31.2 μg/mL for ZnO for Staphylococcus aureus and at 400 μg/mL for copper, and 16000 μg/mL for zinc oxide for Pseudomonas aeruginosa. Concentrations are derived from known minimum inhibitory concentration (MIC) values of 140 μg/mL and 3.9 μg/mL, and 50 μg/mL and 2000 μg/mL respectively (5-8). The bacterial adhesion experiments uses 100 μL diluted bacteria and 100 μL NP solution in a 96-well plate. After 24-hours incubation, 10 μL bacteria is taken from MIC value wells, diluted, and plated onto Petri dishes for observation post incubation.

    Results, Conclusions, and Discussions:: Cu and ZnO had the largest antibacterial effect at 560 μg/mL and 7.8 μg/mL for the Staphylococcus aureus strains and 200 μg/mL and 16000 μg/mL for the Pseudomonas aeruginosa strains growth curves. Since these values vary largely from Cu to ZnO, closer values were analyzed for quantitative comparison. Staphylococcus aureus 0977 used Cu concentration of 280 μg/mL and ZnO concentration of 0.975 μg/mL (Figure 1), and Staphylococcus aureus 1000 used Cu of 1120 μg/mL and ZnO of 31.2 μg/mL (Figure 2). Pseudomonas aeruginosa 0256 and 0264 used Cu of 200 μg/mL and ZnO of 250 μg/mL (Figure 3 and Figure 4). This evidence shows that while ZnO has a higher antibacterial effect at higher concentrations, Cu NPs can have a similar effect using a lesser, safer concentration. In clinical applications, this would present Cu NPs whether in solution-based therapies or surface modifications, when compared to ZnO NPs, have a higher bactericidal impact, and exhibit more cytocompatible properties. The bacterial adhesion experiment used the same bacterial strains from the 96-well plates of the growth curve experiment. The resulting data shows that ZnO NPs have a larger bactericidal effect than Cu NPs with Pseudomonas aeruginosa strains, and that the reverse is true for Staphylococcus aureus strains. With Pseudomonas aeruginosa strains, ZnO uses a higher concentration of NPs than Cu, attributing to its larger log reduction (Figure 5). Factors such as metal-mediated antibacterial mechanisms for membrane disruption contribute to all the results obtained (9).

    Data collected was likely affected by the nanoparticles’ tendency to settle out of their solutions. Further testing with varying particle sizes and the addition of testing zinc would establish greater conclusive significance. Since zinc oxide has a neutral charge, this alters how it approaches gram negative bacteria’s lipopolysaccharide exterior (10). Regarding CDC clinical strains Staphylococcus aureus 0977 and 1000 and Pseudomonas aeruginosa 0256 and 0264, Cu NP solutions have a greater applicable antibacterial effect than ZnO NP solution. At higher tested concentrations ZnO NP solutions have a greater antibacterial effect, however further cytotoxicity test would need to be done to verify the safety of their usage.





    Acknowledgements (Optional): : This material is based upon work supported by a National Science Foundation Research Experiences for Undergraduates (REU) site program under Grant No. 1950581.

    References (Optional): :

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