University of Notre Dame du Lac has disclosed peptide-drug conjugates, their hydrogels and their self-assembling nanofibers comprising glucagon-like peptide 1 receptor (GLP-1R) and/or gastric inhibitory polypeptide receptor (GIPR) and/or glucagon receptor agonists linked to an amphiphile moiety through a hydrophobic or hydrophilic-comprising linker acting as vaccine adjuvants reported to be useful for the treatment of diabetes and obesity.