Integration of chitosan, watermelon pulp lycopene, and zinc oxide nanoparticles: A green nanocomposite with anticancer and antimicrobial potential

A green, two-step approach was used to synthesize chitosan- and watermelon-extract-functionalized ZnO nanoparticles (WRZCLNPs) by combining rind-mediated ZnO formation with a chitosan and lycopene-rich pulp extract coating. Spectroscopic and microscopic analyses confirmed a crystalline ZnO core with an amorphous organic shell, supported by UV-Vis shifts, XRD broadening, FTIR bands, XPS signal, and TEM core-shell morphology. SEM showed progressively smoother and more compact aggregates after coating, while EDX recorded increased carbon and nitrogen content, consistent with chitosan and extract incorporation. Dynamic light scattering indicated reduced polydispersity (PDI 1.44) in WRZCLNPs compared with uncoated ZnO (PDI 57.58), and the zeta potential remained near neutral. WRZCLNPs showed selective cytotoxicity toward MCF-7 and HT-29 cells, with IC₅₀ values of 40.96 μg/mL (95% CI: 38.13-44.25) and 38.87 μg/mL (95% CI: 36.53-41.37), while normal cell lines maintained >90% viability. Mechanistic assays demonstrated increased ROS, mitochondrial depolarization, G2/M arrest, DNA fragmentation, and apoptosis, accompanied by reduced PI3K and pAkt/Akt levels. WRZCLNPs also exhibited concentration-dependent antibacterial activity with MIC values between 250 and 495 μg/mL. These findings present a sustainable rind-to-core and pulp-to-shell strategy for generating a multifunctional nanocomposite with dual anticancer and antibacterial potential suitable for further preclinical evaluation.