Editors' ChoiceDrug Delivery

Getting Vaccines and Antibiotics “To Go”

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Science Translational Medicine  08 Aug 2012:
Vol. 4, Issue 146, pp. 146ec141
DOI: 10.1126/scitranslmed.3004703

Refrigeration is ubiquitous in many parts of the developed world, yet the occasional extended power loss highlights the fragility of food and medicine and underlines the need for more stable means of storage in the developing world. Some form of refrigeration is required to keep many vaccines, antibiotics, and other medicines stable before use. Maintaining this “cold chain” from manufacturer to patient often requires a substantial amount of effort and resources, because any breakdown in the “cold chain” lessens (and potentially abolishes) medicine efficacy. Zhang and colleagues now report that it may be possible to eliminate the need for cold storage of some vaccines and antibiotics by binding these medicines with silk.

Aqueous solutions of the antibiotic tetracycline were mixed with suspensions of silk protein, poured into a mold, and dried as thin films. Silk fibroin protein can bind many bioactive molecules to form very stable complexes in which the bioactive molecules remain active. The authors show that silk-tetracycline films retain full efficacy of tetracycline against the bacterium Staphylococcus aureus even after 4 months of storage at 60°C. In comparison, a tetracycline solution decreased to roughly 10% effectiveness after 1 week.

Similar silk films were created by using the measles-mumps-rubella (MMR) vaccine. The separate viral components each remained >85% stable even after 6 months of storage at 45°C for lyophilized MMR-silk films. Stabilization of these viral vaccines with silk may even improve shelf-life compared with current practice of vaccine storage as lyophilized powder alone: For the measles virus, storage at 45°C as a lyophilized silk-film increased the virus half-life by 20 times.

The potential to improve storage and handling of temperature-sensitive medicines by this silk-binding method is very promising. Implementing such technology offers the opportunity to improve vaccine and medicine delivery for many different settings, including remote and developing world locations and disaster relief situations in which refrigeration is not available.

J. Zhang et al., Stabilization of vaccines and antibiotics in silk and eliminating the cold chain. Proc. Natl. Acad. Sci. U.S.A. 109, 11981–11986 (2012). [Abstract]

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