The effect of coffee as a bio reductant in the synthesis of silver nano particles combined with laser photodynamics for bacteria inactivation

Abstract

Abstract Silver nanoparticles (AgNPs) have gained significant attention in antimicrobial treatments due to their potent antibacterial properties and potential applications in combating antibiotic-resistant pathogens. Green synthesis of AgNPs using natural extracts provides an eco-friendly and scalable alternative to chemical methods, leveraging plant bioactive compounds to enhance nanoparticle efficacy. Coffee extract, rich in polyphenols, effectively reduces mixed silver ions into pure silver nanoparticles at the nanoscale. This process not only provides an eco-friendly and sustainable method for AgNP synthesis but also ensures the production of high-quality nanoparticles with enhanced antibacterial properties, making it a promising alternative to traditional chemical reduction methods. This study investigates the biosynthesis of AgNPs using robusta, excelsa, and arabica coffee extracts as bioreductors, capitalizing on coffee’s abundance and richness in polyphenols to produce efficient, customizable nanoparticles with improved antibacterial properties. The synthesized AgNPs were characterized using Ultraviolet-Visible (UV-Vis) spectroscopy and a Particle Size Analyzer (PSA). Antimicrobial photodynamic therapy (aPDT) with red laser exposure was employed to evaluate the effect of various energy densities on bacterial samples. Antibacterial efficacy was assessed using the diffusion well and Total Plate Count (TPC). The UV-Vis analysis revealed peak absorbance wavelengths of 425 nm, 450 nm, and 500 nm for robusta, arabica, and excelsa coffee extracts, respectively. PSA results indicated particle sizes at D50 of 73.08 nm (AgNPs-Arabica), 67.85 nm (AgNPs-Robusta), and 67.67 nm (AgNPs-Excelsa), confirming their nanoscale range (1–100 nm). Antibacterial tests showed the highest Escherichia coli bacterial death rate (95.73%) with AgNPs-Arabica and red laser treatment. Compared, Staphylococcus aureus bacterial death peaked at 94.97% with AgNPs-Excelsa and red laser treatment. These findings highlight the potential of green-synthesized AgNPs as effective antimicrobial agents, particularly when combined with laser-based therapies, offering innovative approaches for treating bacterial infections.

Keywords

• AgNPsArabica
• AgNPsRobusta
• AgNPsExcelsa
• Escherichia coli
• Staphylococcus aureus