Non-proteinogenic amino acid based supramolecular hydrogel material for enhanced cell proliferation

Supramolecular gel material built from low-molecular-weight (LMW) gelators finds potential applications in various fields, especially in drug delivery, cell encapsulation and delivery, and tissue engineering. The majority of the LMW gelators in these applications are based on functionalized peptides/amino acids consisting of proteinogenic amino acids which are proteolytically unstable. Herein, we have developed a new LMW gelator containing non-proteinogenic amino acid namely 2,3-diaminopropionic acid (Dap), a key precursor in the synthesis of many antibiotics namely viomycin and capreomycin, by functionalizing with fluorenylmethoxycarbonyl at both amino terminals of Dap [Fm-Dap(Fm)]. Hydrogelation test at different pH indicates that Fm-Dap(Fm) can form a hydrogel in a wide range of pH (4.9 to 9.1) with minimum hydrogelation concentration depends on the pH. The mechanical strength and thermal stability of the Fm-Dap(Fm) hydrogel material are found to decrease with increasing pH (acidic > neural/physiological > basic). The thermal stability of Fm-Dap (Fm) hydrogels is pH-dependent and elicits high stability at acidic pH. Also, Fm-Dap(Fm) hydrogels exhibit strong thixotropic property where regelation (self-healing) occurs upon release of stress. Morphological analysis indicates the formation of fibrils, which are entangled to form three dimensional network structures. Several spectroscopic measurements provided evidence for the self-assembly of Fm-Dap(Fm) molecules through intermolecular aromatic pi-pi stacking and hydrogen bonding interactions during hydrogelation. Interestingly, Fm-Dap (Fm) not only exhibits hydrogel formation but also shows cell viability and enhanced cell proliferation at physiological pH (7.4). Further, Fm-Dap(Fm) forms a hydrogel upon co-incubation with vitamin B-12 and also exhibits release of vitamin B-12 over a period. The current study thus demonstrates the development of a new hydrogel material, based on LMW gelator containing the non-proteinogenic amino acid, which can elicit cell viability, enhanced cell proliferation, drug encapsulation, and drug release properties. Hence, Fm-Dap(Fm) hydrogel could be an ideal material for biomedical applications, especially in tissue engineering and drug delivery.