Abstract
Titanium dioxide nanoparticles (TiO(2)-NPs) were synthesized using the molten salt method and systematically characterized. TiO(2)-NPs were evaluated for their capacity to promote the growth of Capsicum annuum cultivars together with the plant growth-promoting microorganisms (PGPMs) Bacillus thuringiensis (Bt) and Trichoderma harzianum (Th). The variables analyzed included physiological parameters and antioxidant responses. The capacity of TiO(2)-NPs to scavenge free radicals was also investigated, along with their biocompatibility, using Artemia salina as an in vivo model. The results demonstrated that TiO(2)-NPs exhibited a nanocuboid-type morphology, negative surface charge, and small surface area. It was noted that TiO(2)-NPs enhanced the CFU and spore production of Bt (1.56-2.92 × 10(8) CFU/mL) and Th (2.50-3.90 × 10(8) spores/mL), respectively. It was observed that TiO(2)-NPs could scavenge DPPH, ABTS, and H(2)O(2) radicals (IC(50) 48.66-109.94 μg/mL), while not compromising the viability of A. salina at 50-300 μg/mL. TiO(2)-NPs were determined to enhance the root length and fresh and dry weights of chili peppers. Similarly, TiO(2)-NPs in synergy with Bt and Th increased the activity of β-1,3-Glucanase (2.45 nkat/g FW) and peroxidase (69.90 UA/g FW) enzyme activity, and increased the TPC (29.50 GA/g FW). The synergy of TiO(2)-NPs with the PGPMs consortium also upregulated the total chlorophyll content: 210.8 ± 11.4 mg/mg FW. The evidence from this study unveils the beneficial application of TiO(2)-NPs with Bt and Th as an efficient approach to promote the physiology and antioxidant responses of chili peppers.