Systematic modifications of amino acid-based organogelators for the investigation of structure-property correlations in drug delivery system

Thermogels, used as multi-functional drug-loading materials, have properties that mainly rely on their gelator structure. Although a large variety of organogel systems are used as drug delivery carriers, relatively few have been investigated in terms of their structure-property correlations based on amino acid derivative gelators. Here, a series of amino acid based gelators were synthesized to explore the role of the gelator structure on functional properties, with the aim of establishing a connection between the molecular parameters and gel properties. By varying the three substitutions of the gelator backbone, it was found that a comprehensive interaction, consisting of hydrophobic forces, H-bonding interactions, conformational flexibility and steric repulsion, play a crucial role in determining the gelation properties. Hansen solubility parameters were employed to explore the solvent effect on the network forming and gel properties. From an analysis of the morphologies obtained from polarized optical microscope (POM), atomic force microscopic images (AFM) and scanning electron microscopy (SEM), the gelator structure was found to have an impact on the self-assembly. According to the X-ray diffraction (XRD), the possible conformations adopted by the gelators were revealed through molecular modelling. The ability to form intermolecular H-bonding is vital in molecular packing and, thus, gelation. A structure-property relationship was developed and proposed to provide a theoretical basis for controllable drug delivery implants.