Evaluation of Justicia adhatoda-incorporated tin oxide nanoparticles and CuSe-doped SnO2 nanocomposites: characterization and enhancement of their antibacterial, antioxidant, and cytotoxic activities using an in vitro approach

Abstract

In this study, we carried out the green synthesis and biological evaluation of SnO₂ NPs and CuSe-doped SnO₂ NCs to assess their antibacterial activity, antioxidant activity and cytotoxicity. This is the first report demonstrating the green synthesis of CuSe-doped SnO₂ NCs using Justicia adhatoda extract, which exhibited synergistically enhanced antioxidant, antimicrobial and anticancer properties. The SnO₂ and CuSe NPs were synthesised using Malabar nut (J. adhatoda) plant leaf extract, with CuSe-doping concentrations optimized for enhanced efficacy. The synthesized nanoparticles were characterized using P-XRD, UV-visible, TEM, HRSEM-EDX, HRSEM-EDS, XPS, and FTIR spectroscopy. UV-visible spectroscopy analysis showed a band gap reduction from 3.6 eV (SnO₂) to 2.8 eV (30% CuSe doped SnO₂ NCs), indicating that the dopant material was effectively doped into the SnO₂ NPs. Moreover, such a bandgap change suggests enhanced electronic interactions, which would contribute to their biological activity. TEM analysis revealed an average particle size of 45.51 nm for the SnO₂ NPs and 17.36 nm for the CuSe NPs. The presence of phytochemicals on the surface of the NPs was confirmed through FTIR and XPS. Notably, 30% CuSe-doped SnO₂ NCs exhibited the highest antibacterial activity at 100 μg mL⁻¹ concentration, showing enhanced inhibition zones against the Gram-positive bacterium Staphylococcus aureus (13 mm) and Gram-negative bacteria Escherichia coli (10 mm), Pseudomonas aeruginosa (10 mm), and Klebsiella pneumoniae (8) compared with SnO₂ NPs. The nanocomposites also demonstrated stronger antioxidant potential, with a DPPH free radical scavenging IC₅₀ value of 56.49 μg mL⁻¹, compared with SnO₂ NPs, with a value of 99.58 μg mL⁻¹. Cytotoxicity studies against the HepG2 cell line revealed an IC₅₀ of 120.57 μg mL⁻¹, surpassing previously reported values. These results demonstrate the potential of the eco-friendly 30% CuSe-doped SnO₂ NCs for future applications in drug development, highlighting their promise for biomedical and pharmaceutical applications and paving the way for sustainable drug development.