Synergistic effect of Silver-Nanodiamond composite as an efficient antibacterial agent against E. coli and S. aureus

Saman Iqbal; Muhammad Shahid Rafique; Nida Iqbal; Sultan Akhtar; Aftab Ahmad Anjum; M B Malarvili

doi:10.1016/j.heliyon.2024.e30500

Synergistic effect of Silver-Nanodiamond composite as an efficient antibacterial agent against E. coli and S. aureus

Heliyon. 2024 May 3;10(9):e30500. doi: 10.1016/j.heliyon.2024.e30500. eCollection 2024 May 15.

Authors

Saman Iqbal¹, Muhammad Shahid Rafique², Nida Iqbal³, Sultan Akhtar⁴, Aftab Ahmad Anjum⁵, M B Malarvili⁶

Affiliations

¹ Department of Physics, University of the Punjab, Lahore, Pakistan.
² Department of Physics, University of Engineering and Technology, Lahore, Pakistan.
³ Biomedical Engineering Centre, University of Engineering and Technology, Lahore, Kala Shah Kaku (KSK) Campus, Pakistan.
⁴ Department of Biophysics, Institute for Research and Medical Consultations, Imam Abdulrahman bin Faisal University, Dammam, Saudi Arabia.
⁵ Institute of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan.
⁶ Department of Biomedical and Health Science Engineering, Faculty of Electrical Engineering, Universiti Teknology Malaysia, Skudai, Johor Darul Takzim, Malaysia.

Abstract

Bacterial antimicrobial resistance (BAMR) seems to pose the greatest threat to public health, food safety, and agriculture in this century. The development of novel efficient antimicrobial agents to combat bacterial infections has become a global issue. Silver nanoparticles (Ag NPs) appeared as a feasible alternative to antibiotics. However, Ag NPs face cost, toxicity, and aggregation issues which limit their antibacterial activity. This work aims to stabilize Ag NPs with enhanced antimicrobial activity at comparatively lower Ag concentrations to prevent bacterial infections. For this purpose, the Ag core was covered with nanodiamonds (NDs). Ag-NDs composite have been synthesized by microplasma technique. TEM analysis confirmed the presence of both Ag and NDs in the Ag-NDs composite. A particle size (∼19 nm) was reported for Ag-NDs at the highest concentration as compared to Ag NPs (∼3 nm). The conduction band of the diamond acted as an extremely strong reducing agent for Ag NPs. The large surface area of NDs stabilized the Ag NPs. A redshift (∼400 nm-406 nm) in UV-visible spectra of the Ag-NDs composite indicated the formation of bigger-sized Ag NPs after incorporating NDs. XRD and LIBS analysis verified the increase in intensity of Ag-NPs by increasing ND concentration. The presence of functional groups including OH, CH, and Ag/Ag₂O was confirmed by FTIR. Bacterial inhibition growth appeared to be a dose-dependent process. The minimum inhibition concentration value of Ag-NDs composite at the highest NDs concentration against E. coli (∼ 0.69 μg/ml) and S. aureus (∼44 μg/ml). This is the first study to report the smallest MIC for E. coli (<1 μg/ml). Ag-ND composites emerged to be more efficient than Ag NPs and preferred to be used against BAMR. The enhanced antibacterial activity of the Ag-NDs composite makes it a potential candidate for antibiotics, food products, and pesticides.

Keywords: Bacterial antimicrobial resistance; Micro-dilution broth method; Microplasma; Minimum inhibition concentration; Nanodiamonds; Silver.