Nanoparticle-gel hybrid material designed with bile acid analogues

A novel design of gold nanoparticles (NP)-hydrogel hybrid material using facially amphiphilic steroid analogs, is described. The gold NPs were prepared by the NaBH4 reduction of the yellow homogeneous solution of HAuCl4 in the presence of steroidal thiols in methanol, keeping a 1:1 molar ratio between the gold salt and the steroidal thiol. These steroid-capped AuNPs are stable through several crystals of drying and re-dissolution. They can be easily dispersed in protic and polar aprotic organic solvents. It was observed that the incorporation of the steroid-capped AuNPs into bile acid-derived hydrogelator 4 shows no change in the melting behavior of the gel. This super hydrogelator forms a fibriller network upon aggregation in the AcOH/water medium. It was also found that the steroid capped AuNPs are significantly stabilized by the supramolecular structures present in the gel.