Encapsulating blood samples in air-dried silk protein can preserve them for long periods of time at high temperatures without refrigeration, scientists have found.
The technique developed at Tufts University in the US 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, jeopardising 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 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 Celsius. At set intervals, encapsulated blood samples were recovered by dissolving the films in water and analysed.
"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 centralised testing facilities," said David L Kaplan, professor at Tufts School of Engineering.
"For example, this could support large-scale epidemiologic studies or remote pharmacological trials," Kaplan said.
"We found that biomarkers could be successfully analysed even after storage for 84 days at temperatures up to 113 degrees F," said Jonathan A Kluge, who was a postdoctoral associate in the Kaplan lab at the time of the research.
"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 Kluge.
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, researchers said.
Researchers demonstrated silk's ability to stabilise a variety of bioactive materials including antibiotics, vaccines, enzymes and monoclonal antibiotics with numerous biomedical and biomaterial applications.
The study was published in the journal PNAS.
