Intercalation of Ga3 +-salicylidene-amino acid Schiff base complexes into layered double hydroxides: Synthesis, characterization, acid resistant property, in vitro release kinetics and antimicrobial activity

• Ga3 + salicylidene amino acid Schiff base complexes are intercalated into Mg/Al-LDH.
• Monolayer, bilayer and trilayer models of guest molecules in hybrids are proposed.
• Protection of LDH increases Ga3 + complexes’ acid resistance in wide pH range of 7–1.
• The hybrids release guests following first-order kinetics via ion exchange.
• The hybrids keep the antibacterial activity of guests against P. Aeruginosa.

This study is aimed to evaluate the potential application of a drug delivery system of Ga3 + complexes in layered double hydroxide, i.e. [Ga(L)2]−-LDH (L represents Schiff base ligands made up of salicylidene with glycine, alanine, tyrosine, phenylalanine, aspartic acid and glutamic acid for complexes 1–6, respectively). The successful intercalation of Ga3 + complexes into Mg/Al-NO3-LDH by delaminating/restacking method was proved by elemental analysis, XRD, FTIR spectra, UV–vis DR spectra, TG analysis and SEM measurements. A monolayer intercalation of 5 and 6, bilayer of 1 and 3 and trilayer of 2 and 4 in interlayer region of hybrids which have extended gallery height of 11.86–21.22 Å were deduced. Better acid resistance than the pristine complexes in wide pH range from 7 to 1 was revealed by UV–vis spectra. The cumulative release profile of Ga3 + complexes from the hybrids in phosphate buffer (pH 7.4) following first-order kinetics via ion-exchange between guest anions and phosphate anions was established by UV–vis spectra. Antibacterial activity of hybrids with MIC values of 65–137 μmol/L against Pseudomonas aeruginosa was demonstrated by the broth twofold dilution method. These results suggest that LDH is a promising host material for carry and controlled delivery of biologically active Ga3 + complexes.

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