Silk-Based Technique Stabilizes Fluid Samples for Diagnostics or Research

Drying blood or other biological fluid samples together with silk fibroin has been suggested as an alternative to refrigeration or drying on paper for transporting specimens from the field to the laboratory.

Without proper temperature regulation, protein biomarkers in particular can degrade rapidly in blood samples, an effect that ultimately compromises the quality and reliability of laboratory tests. Existing alternative collection and storage solutions, such as drying blood on paper cards, still fail to effectively protect biomarkers from heat and humidity.

Investigators at Tufts University (Medford, MA, USA) have described an alternative silk matrix encapsulation technique that overcomes these limitations and can be deployed using a simple air-drying approach. They 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 for up to 84 days at temperatures between 22 and 45 degrees Celsius. At set intervals, encapsulated blood samples were recovered by dissolving the films in water and analyzed.

Results revealed that the silk-based technique required accurate starting volumes of the blood or other specimens to be analyzed. Salts or other buffers were needed in some cases to reconstitute samples for accurate testing of certain markers. When these conditions were met, the investigators found that the silk fiber drying process was compatible with a number of immunoassays and provided enhanced sample preservation in comparison with traditional air-drying paper approaches.

"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 author Dr. David L. Kaplan, professor of biomedical engineering at Tufts University.

The process was described in detail in the May 9, 2016, online edition of the journal Proceedings of the [U.S.] National Academy of Sciences.

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