The emerging microbial drug resistance has limited the choices of treatments for infectious diseases. Application of drugs conjugated with nanoparticles is among the strategies to subside the chance of acquiring resistance and increase the potency of current antibiotics. This study was conducted to produce gold nanoparticles (GNPs) by Fusarium oxysporum to evaluate the antibacterial activity of GNPs conjugated with tetracycline under different conditions.

GNPs were synthesized using the culture supernatants of F. oxysporum treated with a chloroauric acid solution. Production of GNPs and their conjugation with tetracycline was confirmed by noticing the change in color, spectrophotometry, X-ray diffraction analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy spectra. The antibacterial activity of the conjugated GNPs was then assessed.

The formation of GNPs was confirmed by appearance of purple color and an absorption peak at 530nm The produced GNPs were found to be spherical and hexagonal. FTIR confirmed the binding of functional groups of tetracycline to the GNPs surface. The minimum inhibitory concentration of conjugated GNPs demonstrated a much greater antibacterial activity against Gram-positive and Gram -negative bacteria as compared to tetracycline and free GNPs.

Biosynthesis of GNPs by F. oxysporum has advantages including fast growth rate, inexpensive biomass handling, safety and easy processing. Conjugation of tetracycline with GNPs enhances antibacterial activity, which may have significant therapeutic applications.