Antibacterial and Anticancer Evaluation of Copper-Aluminum (CuAl) Layered Double Hydroxides (LDH) Synthesized Using...

The advancement of nanotechnology has significantly accelerated the development of antibacterial and anticancer therapeutics for biomedical applications. Among emerging nanomaterials, layered double hydroxides (LDHs) offer several advantages, including ease of synthesis and inherent therapeutic properties. In this study, the antibacterial and anticancer activities of copper-aluminum (CuAl) LDHs were assessed.

CuAl LDHs were synthesized via the co-precipitation method and characterized. Antibacterial activity was evaluated through broth microdilution, colony-forming unit (CFU) counts, followed by biofilm inhibition assays. Cytotoxicity experiments were conducted in monolayer and 3D tumor spheroid cultures, followed by mechanistic studies including reactive oxygen species (ROS), mitochondrial superoxide, apoptosis/necrosis, and cell cycle assays.

The particle sizes were 619.2 and 604.3 nm, with polydispersity index (PDI) values of 0.16 and 0.13 at pH 6 and 7.4, respectively. Zeta potential values ranged from +37.81 to +38.53 mV across pH 3 to 10, indicating good colloidal stability. The CuAl LDHs were effective against Gram-positive bacteria Streptococcus gallolyticus and Staphylococcus epidermidis, while showing lower activity against the Gram-negative bacteria Klebsiella aerogenes and Proteus vulgaris. Scanning electron microscopy (SEM) analysis showed that the LDHs resulted in envelope disruption, morphological deformation, and aggregation in all tested bacteria. In contrast, stronger antibiofilm activity was observed against Gram-negative bacteria. CuAl LDHs showed dose-dependent growth inhibition in both colorectal cancer (CRC) cell lines, HCT-116 and HT-29, particularly in 3D tumor spheroid models. Mechanistic studies revealed that CuAl LDH induced total ROS and mitochondrial superoxide production and triggered apoptosis in CRC cells, primarily through the downregulation of the anti-apoptotic genes BCL-2 and BCL2L1 (BCL-XL). While CuAl LDHs did not significantly alter cell cycle progression, a reduction in the expression of cell cycle-related genes, CCNE1 and CCNB1 was observed.

CuAl LDHs exhibit antibacterial, antibiofilm, and anticancer activities, indicating their potential as multifunctional materials for CRC-related biomedical applications. Their cytotoxic effects in CRC cells are associated with increased ROS generation, mitochondrial superoxide production, and apoptosis induction. Further studies are needed to assess their biocompatibility and selectivity toward normal cells, improve tumor-targeting capability, evaluate the implications of their relatively large particle size, and confirm the molecular mechanisms underlying their biological effects.