Targeted colon cancer therapy using lapatinib-encapsulated chitosan nanoparticles conjugated with lactoferrin and melatonin with integrated <i>in silico in vitro</i> and <i>in vivo</i> evaluation

Colorectal cancer is major cause of mortality, necessitating improved treatments. Lapatinib-loaded chitosan nanoparticles conjugated with lactoferrin and melatonin (LAP-CS-LF-MLT-NPs) developed using ionic gelation and carbodiimide coupling to improve bioavailability and minimise toxicity. Nanoparticles had a size of 184.36 ± 1.25 nm, a zeta potential of +31.88 ± 1.21 mV, and an entrapment efficiency of 68.23 ± 1.69%. FTIR, XRD, DSC, Raman, and NMR validated drug encapsulation, whereas FE-SEM, TEM, and AFM displayed uniform, smooth, spherical structures. <i>In vitro</i>, LAP-CS-LF-MLT-NPs displayed an IC₅₀ of 0.17 µg/mL in HCT116 cells compared to 127 µg/mL for free lapatinib, indicating a 700-fold enhancement in potency. Further investigations revealed a 48.29% arrest in G1-phase, a 233.44% disruption of mitochondrial membrane potential, and a 4.15% occurrence of late apoptosis, while ROS levels decreased to 54.13%, indicating melatonin's facilitation of ROS-independent apoptosis. Molecular docking demonstrated strong binding to EGFR (-12.014), SRC (-10.778), and MAPK14 (-10.298). Pharmacokinetic studies in Wistar rats showed a longer half-life (9.69 vs. 5.28 h), higher AUC₀-∞ (452.880 vs. 159.715 µg/mL·h), and improved MRT (15.260 vs. 7.696 h). Focused colon retention (8.20 ± 1.38 µg/g), minimal toxicity, and confirmed safety and stability underscore its potential as an accurate, efficient treatment for colon cancer.