Synthesis of silver nanoparticles co-stabilized by carboxymethylcellulose using a sugarcane endophytic Aspergillus brasiliensis

The integration of green chemistry principles into nanoparticle production presents a promising alternative for large-scale production while ensuring colloidal stability, biocompatibility, and sustainability. In this context, microorganisms such as fungi offer bioactive compounds of interest for the synthesis of nanostructures, particularly metallic nanoparticles, with a view to biotechnological applications. In this study, employing a field-to-laboratory approach, we prospected for fungi present in sugarcane and utilized the endophytic extract of the identified species, Aspergillus brasiliensis , for the development of silver nanoparticles. The effect of adding carboxymethylcellulose (CMC) as a co-stabilizer on the stability of the mycosynthesized nanoparticles was also evaluated under different exposure conditions, such as UVB and UVC doses, and long-term analysis. Silver nanoparticles stabilized by the endophytic extract of A. brasiliensis ( Ab -AgNPs) and those co-stabilized by CMC ( Ab -AgNPs-CMC) exhibited a face-centered cubic crystalline structure and typical optical absorption ranging between 350 and 600 nm. Ab -CMC-AgNPs exhibited long-term colloidal stability over one year, as demonstrated by the consistent nanoparticle size and a significant change in surface zeta potential from an initial value of -25.0 mV to a final value of -27.5 mV. The Ab -CMC-AgNPs demonstrated antibacterial effects against Gram-positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis , at a concentration of 1.95 µg mL -1 . Our results suggest a mechanism where CMC acts as a co-stabilizer, effectively passivating the surface of silver nanoparticles through carboxyl groups, improving stability when used with A. brasiliensis extract against high UVB and UVC doses (at 20 J) and over extended periods. Our findings highlight the importance of developing synthetic approaches that align sustainability with mycosynthesis, offering a promising alternative for environmentally friendly synthesis of materials for biological applications in human health and agriculture. • Silver nanoparticles (AgNPs) were synthesized using Aspergillus brasiliensis extract and carboxymethylcellulose (CMC) as a co-stabilizer; • Mycosynthesized AgNPs stabilized with CMC were characterized using UV-Vis, FT-IR, XRD, and SEM-EDX techniques; • CMC-stabilized mycogenic AgNPs offer a promising approach for environmentally friendly materials synthesis; • AgNPs exhibited significant antibacterial activity against Gram-positive bacteria; • AgNPs demonstrated stability under prolonged exposure to high-dose UVB radiation.