In order to detect and quantify bone-specific alkaline phosphatase (BAP) in a human biological sample, a binding agent (molecule) that specifically recognizes BAP in a sample is typically required. This binding agent can then be used in numerous assays/instruments to enable the detection and quantification of BAP.

BAP is a unique protein expressed in human serum, and no prior art has described a DNA-based molecule that binds to BAP. BAP levels in human serum may provide information related to bone metabolism in astronauts during long-duration exposure to microgravity.

Antibodies exist that bind specifically to BAP; however, they must be stored long-term in freezers. Additionally, antibodies are typically not stable to more than a few hours in ambient conditions, whereas the aptamer to BAP is ambient stable for years.

DNA-based molecules that are chemically synthesized and that bind to a specific protein (bone-specific alkaline phosphatase) in solution have been developed. A solution-based process for aptamer selection was used to identify specific DNA sequences that have affinity for BAP. Generally, a solution of many DNA strands was synthesized; the BAP protein was immobilized on a filter and also on magnetic beads. The library solution was passed over the target, and the DNA strands that bound to the target were amplified. These steps were repeated numerous times.

Several DNA sequences were isolated that bind with high affinity and good specificity to C-reactive protein (CRP). This binding to CRP enables quantification of CRP in a biological sample. CRP is an important protein in the human body, and measuring the quantity of CRP in a blood sample is of interest during the study and/or diagnosis of numerous diseases and conditions. The DNA-based aptamers do not require refrigeration.

This work was done by Xianbin Yang, Nancy Ward, and Ross Durland of AM Biotechnologies for Johnson Space Center. MSC-24629-1/5440-1


NASA Tech Briefs Magazine

This article first appeared in the May, 2015 issue of NASA Tech Briefs Magazine.

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