Disclosed is a general methodology to create nano fibers of therapeutic molecules that have a dual role, as both the delivery vehicle and the drug itself. It is shown that with proper molecular design, the integration of enzymatic reaction and self-assembly provides a powerful method to create molecular hydrogels of clinically-used therapeutics without compromising their bioactivities. In addition, the results disclosed herein demonstrate enzyme-instructed self-assembly as a facile strategy for generating the supramolecular hydrogels of molecules that inherently have poor solubility in water. For example, by covalently connecting paclitaxel with a motif that is prone to self-assemble, a hydrogel of paclitaxel can be formed without compromising the activity of the paclitaxel.