Biosurfactant assisted in situ green and clean preparation route for layered double hydroxides and their green metrics-based sustainability assessment

Abstract

Hybrid advanced multifunctional materials based on layered double hydroxides (LDH) and intercalated guest biomolecule(s) are of high industrial and academic importance and have found promising applications in diverse fields such as biomedical, energy, environment, agriculture, etc. This report strategically develops a new innovative green sonochemical route to incorporate rhamnolipid (RL) and surfactin (SR) into 3D hierarchical flower-like Mg-Al-LDH micro-nano-structures. When compared to traditional mechanochemical co-precipitation and ion-exchange methods, the designed one-pot and scalable method was sustainable and green chemistry compliant, with improved time, energy, and solvent efficiency. RL/SR anions act as an interlayer anion and a template for the fabrication of LDH sheets leads to the increase in the basal spacing and impair LDH sheet interaction. Consequently the vesicle-type phase can be fabricated using biosurfactant in aqueous media under the influence of metal cations induced the curved growth of RL/SR-intercalated LDH nuclei and the flower-like assemblage of LDH particles. The structure, morphology, surface properties, and thermal stability were evaluated. The release profile and kinetics of RL/SR of the intercalated LDHs was studied. Slow and controlled release of SR from the Mg/Al-LDH micro-nano-structures was observed for a prolonged time up to 10 h and followed zeroth-order kinetics, whereas RL release was well described in Higuchi model, indicating the release of the biomolecule via a diffusion mechanism. Cytotoxicity (in L929 and 3T3 fibroblast cells) and haemolytic tests suggested that cytotoxic effect in the range of 25–400 mg/ml and the haemolytic ratio was <4 % at 25–600 mg/ml, showing good biocompatibility of the biosurfactant-intercalated LDHs. Taken together, these micro-nano-structures can be used as potential sustained- or extended-release candidate for agricultural, biomedical or water treatment applications.