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Silk stabilizes blood samples for months at high temperatures

Researchers at Tufts University have stabilized blood samples for long periods of time without refrigeration and at high temperatures by encapsulating them in air-dried silk protein. The technique, which is published online this week in the Proceedings of the National Academy of Sciences, has broad applications for clinical care and research that rely on accurate analysis of blood and other biofluids.

Blood contains proteins, enzymes, lipids, metabolites, and peptides that serve as biomarkers for health screening, monitoring and diagnostics. Both research and clinical care often require blood to be collected outside a laboratory. However, unless stored at controlled temperatures, these biomarkers rapidly deteriorate, jeopardizing the accuracy of subsequent laboratory analysis. Existing alternative collection and storage solutions, such as drying blood on paper cards, still fail to effectively protect biomarkers from heat and humidity.

The Tufts scientists successfully mixed a solution or a powder of purified silk fibroin protein extracted from silkworm cocoons with blood or plasma and air-dried the mixture. The air-dried silk films were stored at temperatures between 22 and 45 degrees C (71.6 to 113 degrees F). At set intervals, encapsulated blood samples were recovered by dissolving the films in water and analyzed.

“This approach should facilitate outpatient blood collection for disease screening and monitoring, particularly for underserved populations, and also serve needs of researchers and clinicians without access to centralized testing facilities. For example, this could support large-scale epidemiologic studies or remote pharmacological trials,” said senior and corresponding author David L. Kaplan, Ph.D., Stern Family Professor in the Department of Biomedical Engineering at Tufts School of Engineering.

“We found that biomarkers could be successfully analyzed even after storage for 84 days at temperatures up to 113 degrees F. Encapsulation of samples in silk provided better protection than the traditional approach of drying on paper, especially at these elevated temperatures which a shipment might encounter during overseas or summer transport,” said the paper’s co-first author Jonathan A. Kluge, who earned both his Ph.D. and B.S. from Tufts School of Engineering and was a postdoctoral associate in the Kaplan lab when the research was done.

The paper noted that the silk-based technique requires accurate starting volumes of the blood or other specimens to be known, and salts or other buffers are needed to reconstitute samples for accurate testing of certain markers.

Kaplan, whose specialty is biopolymer engineering, has studied the unique properties and applications of silk for more than 20 years. He and his collaborators have successfully demonstrated silk’s ability to stabilize a variety of bioactive materials including antibiotics, vaccines, enzymes and monoclonal antibiotics with numerous biomedical and biomaterial applications. He also holds Tufts faculty appointments in the Department of Chemical and Biomedical Engineering, School of Medicine, School of Dental Medicine and Department of Chemistry in the School of Arts and Sciences.

The work was supported by National Science Foundation Award IIP-1521898, Air Force Office of Scientific Research Grant FA9550-14-1-0015, Defense Threat Reduction Agency Grant HDTRA1-14-1-0061, National Institutes of Health Grant P41EB002520 and Defense Advanced Research Projects Agency Program SB112-005.

Silk-based blood stabilization for diagnostics.Jonathan A. Kluge, Adrian B. Li, Brooke T. Kahn, Dominique S. Michaud, Fiorenzo G. Omenetto, and David L. Kaplan.Proceedings of the National Academy of Sciences. DOI:10.1073/pnas.1602493113. Published online May 9, 2016.