Synthesis and characterisation of layered double hydroxide-palmitic acid for controlled release and antimicrobial activity studies

An effective drug delivery system enhances bioavailability to improve therapeutic outcomes. Incomplete drug administration can reduce effectiveness, requiring higher or more frequent doses. This study focuses on developing nanocomposites that use layered double hydroxides (LDHs) as drug carriers to improve bioavailability. Zinc-aluminium (ZnAl-LDH) and calcium-aluminium (CaAl-LDH) LDHs were synthesized, and palmitic acid (PA) was intercalated into these structures using the co-precipitation method, forming ZnAl-LDH-PA and CaAl-LDH-PA nanocomposites. Powder X-ray diffraction (PXRD) analysis confirmed successful intercalation, with increased interlayer spacing from 8.60 Å to 14.95 Å for 0.05 M CaAl-LDH-PA and from 8.92 Å to 14.35 Å for 0.2 M ZnAl-LDH-PA. Fourier transform infrared (FTIR) spectroscopy further validated PA incorporation by showing the absence of nitrate peaks at 1,347 cm-1 and the presence of asymmetrical and symmetrical COOˉ stretching vibrations in the 1,540 to 1,577 cm-1 range. Energy dispersive X-ray (EDX) analysis confirmed intercalation by detecting no nitrogen, while carbon accounted for 56.8% in CaAl-LDH-PA and 71.9% in ZnAl-LDH-PA. Brunauer-Emmett-Teller (BET) surface area measurements indicated significant increases, from 7.93 m²g-1 to 19.8 m²g-1 for CaAl-LDH-PA and from 4.82 m²g-1 to 21.35 m²g-1 for ZnAl-LDH-PA, confirming anion exchange. Thermal stability assessments demonstrated improved decomposition temperatures, shifting maximum weight loss to 260°C for CaAl-LDH-PA and 220°C for ZnAl-LDH-PA compared from 205°C for pure PA. Controlled release studies of PA confirmed both nanocomposite exhibit pH-dependent release behaviour. CaAl-LDH-PA showing highly sustained at pH 4.8 with a maximum release of 75%, while ZnAl-LDH-PA show the highest release efficiency in pH 4.8 but the most sustained release in pH 7.4. Antibacterial tests showed the intercalation of PA into both nanocomposites preserve the antimicrobial ability of PA against gram-positive and gram-negative bacteria. These findings highlight the potential of LDH-PA nanocomposites as promising carriers for drug delivery applications.