Antibiotic Encapsulation and Release by Halloysite/Polymer Composites for Biomedical Applications

Undergraduate #322
Discipline: Technology and Engineering
Subcategory: Biomedical Engineering

Sean Bittner - Auburn University
Co-Author(s): Lee Robeson, Emma Adams, and Edward W. Davis, Auburn University, Auburn, AL

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Halloysite, an aluminosilicate clay, is a promising alternative for drug delivery as it is cheap, abundant and nontoxic. Halloysite can be loaded with up to 30 wt% chemical agent while encapsulation extends release from minutes to several hours or days. However, experiments with biologically relevant polymers are limited in literature. Additionally, most studies use tetracycline and other small, water soluble antibiotics. Novel antibiotics are larger, imposing release limitations. This project aims to advance understanding of controlled release from Halloysite/polymer systems by investigating these areas. Gentamicin sulfate and ofloxacin antibiotics are mixed with 1g halloysite. The mixture is placed in a vacuum desiccator; cycles of vacuum and pressurization result in fizzing of the paste, indicating removal of air. The solution is then mixed and left to dry under vacuum, and loading and vacuum procedures are repeated. The resulting drug-loaded halloysite is ground and stored under refrigeration. Films are prepared via solution casting; a 25% w/v PLGA solution is prepared by adding the polymer to a 3:1 v/v THF-DMF solution and mixing until dissolved. Halloysite and DLH (0, 3 and 10% halloysite to PLGA) are dissolved by stirring. The solutions are then cast and dried. To evaluate release from DLH, 0.1g DLH was added to 10mL deionized water or phosphate buffer in a centrifuge tube. The tubes were centrifuged and supernatant samples were tested by UV spectraphotometry. Release studies from PLGA films were conducted similarly, substituting 0.1g DLH with drug-loaded composite film. Control vials were prepared containing equivalents of pure drug, halloysite and drug-loaded PLGA. Progress on the project has yielded a consistent film-casting procedure and calibration curves for ofloxacin and gentamicin sulfate. Release rates are quantified by antibiotic concentration in the sample; concentration can be directly calculated from UV absorbance. Compared to pure PLGA, it is expected that antibiotic release from composites is retarded. Additionally, the effects of the LA:GL ratio on degradation will be studied. The use of drug loaded halloysite containing polymeric films is a promising technique for the long term controlled release of antibiotic agents. These composite materials are promising for the treatment of infected wounds, prophylactic treatment of battle field injuries and the development of antimicrobial surfaces.

Funder Acknowledgement(s): National Science Foundation

Faculty Advisor: Edward W. Davis, ewd0001@auburn.edu