This paper reports the first antibiotic gelatorsvancomycin-pyrene (1)sthat forms hydrogels via hydrophobic interaction and hydrogenbonding-promoted self-assembly in water. Hydrogels, formed by three-dimensional, elastic networks whose interstitial spaces are filled with water, present many useful properties (e.g., response to the external stimuli) and applications (e.g., gel electrophoresis, chemical sensing, drug delivery, as a biointerface, and as actuators). 1,2 Biopolymers (e.g., collagens, 3 polysaccharide, 4 etc.) and hydrophilic synthetic polymers (e.g., polyacrylamide 2,5 and polypeptides 6 ) have been successfully employed to form hydrogels. Nonpolymeric hydrogelators, however, are rare despite that their counterpartsssmall molecular organogelators 7,8 shave expanded rapidly and received intensive studies in the past decade. Recently, Hamilton, 9 Shinkai, 10 Zhang, 11 and others 12 have reported low molecular weight hydrogelators that form hydrogels via carefully balancing the hydrophobic interactions and hydrogen bonds in water to induce aggregations of those small molecules. Their results inspired us to design and synthesize hydrogelators based on antibioticssan important class of biomoleculessin the hope of developing biomaterials that can treat infectious wounds, serve as an antiseptic matrix, and provide a new way of drug delivery. 13 We chose vancomycin (Van), one of the most important antibiotics, as the platform to make the hydrogelators because of (1) its clinical significance in treating Gram-positive bacterial infections; 14 (2) its relatively easy synthetic modifications; 15 and (3) its strong tendency to form multiple hydrogen bonds with suitable substrates or itself in aqueous solution, as revealed by Wash et al. in the decipherment of the molecular logic of vancomycin resistance enterococci (VRE), 16 by Williams et al. in the elucidation of binding mode of Van,17,18 and by Whitesides et al. in the studies of multivalency of Van. 19 Learning from the principles developed in the study of low molecular weight organogelators, 7,20 we successfully generated a hydrogelator based on Van by introducing a pyrene group to the C-terminal of the backbone of Van. Our results indicate that the π-π stacking and intermolecular hydrogen bonding in water provide driving forces to form a noncovalent polymer of 1, which is primarily responsible for the gelation. We believe that such an approach, which eliminates the biologically inactive molecules (e.g., cross linked polyacrylamide, etc.) in conventional hydrogels, could lead to a new kind of biomaterial for useful applicationssfor example, controlled releases of therapeutics or surface coatings of medical devices. Figure 1 shows the chemical structure of 1 and the picture of the hydrogel (formed by adding 6.5 mg of 1 into 1.8 mL of water, corresponding to ∼0.36 wt % (2.2 mM) of the gelator and ∼23 000 water molecules/gelator molecule). Figure 2a shows the emission spectra of the hydrogels of 1 at two different concentrations. The broad band of the emission...
