Abstract

Background: Synthesis of spherical silver nanoparticles is mostly reported, but the use of DNA, especially short oligonucleotides, to mediate the production of anisotropic AgNPs is still questioned.

Objective: This work aims to use 30-mer oligo(dA) and oligo(dC) (or A30 and C30) to assist the formation of anisotropic AgNPs under blue LED irradiation.

Methods: We reported a simple synthesis reaction containing AgNO₃, A30 (or C30), and sodium borohydride, which were exposed to 460 nm LED light for 24 h. The obtained AgNPs were characterized and assayed for antioxidant and antibacterial activities.

Results: With exposure to 460 nm LED light, A30 and C30 could mediate the transition from spherical to hexagonal shapes of AgNPs with average sizes of 16 − 18 nm. Analyses of X-ray diffraction and selected area electron diffraction indicated the face-centered cubic crystal structure of AgNPs. A30- and C30-AgNPs exhibited similar antioxidant activities; IC₅₀ of 78.68 ± 0.83 and 73.91 ± 0.46 μg mL⁻¹, respectively. They also possessed antibacterial activities against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Scanning electron micrographs revealed surface pores and rupture of bacterial cells in response to AgNPs.

Conclusion: Oligonucleotides of only 30 residues are shown to assist the generation of anisotropic AgNPs under activation of blue LED irradiation, in which the synthesized AgNPs still exhibited antioxidant and antibacterial activities, suggesting a simple method to synthesize non-spherical AgNPs using short-length DNA.

Keywords: Anisotropic nanoparticle, antibacterial activity, green synthesis, light-emitting diode, oligonucleotide, silver nanoparticles.

Graphical Abstract