Chemical Synthesis of Innovative Silver Nanohybrids with Synergistically Improved Antimicrobial Properties

Background: The wide use of antibiotics has created challenges related to antibiotic-resistant bacteria, which have been increasingly found in recent decades. Antibiotic resistance has led to limited choices of antibiotics. Multiple old antimicrobial agents have high antimicrobial properties toward bacteria, but they unfortunately also possess high toxicity toward humans. For instance, silver (Ag) compounds were frequently used to treat tetanus and rheumatism in the 19th century and to treat colds and gonorrhea in the early 20th century. However, the high toxicity of Ag has limited its clinical use. Purpose: We aimed to reformulate Ag to reduce its toxicity toward human cells like osteoblasts and to optimize its antimicrobial properties. Results: Ag, an old antimicrobial agent, was reformulated by hybriding nanomaterials of different dimensions, and silver nanoparticles (AgNPs) of controllable sizes (95-200 nm) and varying shapes (cube, snowflake, and sphere) were synthesized on carbon nanotubes (CNTs). The obtained AgNP-CNT nanohybrids presented significantly higher killing efficacy against Staphylococcus aureus (S. aureus) compared to AgNPs at the same molar concentration and showed synergism in killing S. aureus at 0.2 and 0.4 mM. AgNPs presented significant osteoblast toxicity; in contrast, AgNP-CNT nanohybrids demonstrated significantly enhanced osteoblast viability at 0.04-0.8 mM. The killing of S. aureus by AgNP-CNT nanohybrids was fast, occurring within 15 min. Conclusion: Ag was successfully reformulated and Ag nanohybrids with various AgNP shapes on CNTs were synthesized. The nanohybrids presented significantly enhanced antimicrobial properties and significantly higher osteoblast cell viability compared to AgNPs, showing promise as an innovative antimicrobial nanomaterial for a broad range of biomedical applications.