Study On The Drug Loading And Delivery Properties Of Graphene Oxide

Graphene oxide (GO) has a high specific surface area with many hydroxyl groups,carboxyl groups and other active groups on its surface and edges, which greatly enhanceits water-solubility and biocompatibility. The skeleton of benzene rings offers largenumbers of π-π binding sites, and oxygen atoms can form hydrogen bonds with drugmolecules, which made GO an ideal drug carrier with promising application.This article reports the preparation of well-oxidated and high water-soluble GOfrom graphite by the modified Hummers method. The solution is bright brown in whichGO disperses as monolayers of a thickness of1.05nm. The loading and releaseproperties of three kinds of drugs: benazepril, captopril and losartan are studied. Resultsshow good loading and release properties. Among these three drugs, benazepril can beloaded on GO via both π-π interaction and hydrogen bonds, so the highest loadingcapacity of benazepril is as high as1.12mg/mg. Dialysis release tests show the releaseof drugs from GO is pH-dependent, that is, pH changes will affect the release rate andthe amount of drug released, which is very important for the controlled release of drugs.In order to further improve the loading capacity and biocompatibility of GO, theamidation and carboxylation modification for GO were carried out and the drug loadingand release properties of modified GO were studied. Results show that amide groupswere conjucted on GO after amidation process, but this process is accompanied by thedeoxidation process, result in poor water-solubility and not suitable for drug delivery.On the contrary, the water solubility of the carboxylated GO is enhanced, and thecontact angle reaches20°, showing a rather high hydrophilicity. TEM images show thatthe carbon skeleton has not been destroyed. Due to the number of carboxyl groups withstronger hydrogen bonding capability increases, the drug loading capacity ofcarboxylated GO is higher than GO, reaching1.45mg/mg. The release propertiy is alsopH-dependent.This article also develops a new gel drug loading system, that is, drug molecules(metformin hydrochloride) are used as the only cross-linking agent to introduce GO togenerate supramolecular hydrogels for drug loading. The hydrogel dosen’t containadditives, and a very small amount of the drug molecules will be able to convert GO tohydrogels by the strong hydrogen bonding between drug molecules and GO. The releaseprocess is also pH-dependent and the release kinetics features consistent with Fickdiffusion law.