DNA preservation in silk

Yawen Liu; Zhaozhu Zheng; He Gong; Meng Liu; Shaozhe Guo; Gang Li; Xiaoqin Wang; David L. Kaplan

doi:10.1039/C6BM00741D

DNA preservation in silk†

Yawen Liu,

‡^a Zhaozhu Zheng,

‡^a He Gong,

‡^a Meng Liu,

^b Shaozhe Guo,

^a Gang Li,^a Xiaoqin Wang

*^a and David L. Kaplan

*^c

Author affiliations

* Corresponding authors

^a National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, People's Republic of China
E-mail: wangxiaoqin@suda.edu.cn
Fax: +86 512 65883371

^b The Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, People's Republic of China

^c Department of Biomedical Engineering, 4 Colby Street, Tufts University, Medford, MA 02155, USA
E-mail: david.kaplan@tufts.edu
Fax: +1 617 627 3231
Tel: +1 617 627 3251

Abstract

The structure of DNA is susceptible to alterations at high temperature and on changing pH, irradiation and exposure to DNase. Options to protect and preserve DNA during storage are important for applications in genetic diagnosis, identity authentication, drug development and bioresearch. In the present study, the stability of total DNA purified from human dermal fibroblast cells, as well as that of plasmid DNA, was studied in silk protein materials. The DNA/silk mixtures were stabilized on filter paper (silk/DNA + filter) or filter paper pre-coated with silk and treated with methanol (silk/DNA + PT-filter) as a route to practical utility. After air-drying and water extraction, 50–70% of the DNA and silk could be retrieved and showed a single band on electrophoretic gels. 6% silk/DNA + PT-filter samples provided improved stability in comparison with 3% silk/DNA + filter samples and DNA + filter samples for DNA preservation, with ∼40% of the band intensity remaining at 37 °C after 40 days and ∼10% after exposure to UV light for 10 hours. Quantitative analysis using the PicoGreen assay confirmed the results. The use of Tris/borate/EDTA (TBE) buffer enhanced the preservation and/or extraction of the DNA. The DNA extracted after storage maintained integrity and function based on serving as a functional template for PCR amplification of the gene for zinc finger protein 750 (ZNF750) and for transgene expression of red fluorescence protein (dsRed) in HEK293 cells. The high molecular weight and high content of a crystalline beta-sheet structure formed on the coated surfaces likely accounted for the preservation effects observed for the silk/DNA + PT-filter samples. Although similar preservation effects were also obtained for lyophilized silk/DNA samples, the rapid and simple processing available with the silk–DNA–filter membrane system makes it appealing for future applications.

Biomaterials Science

DNA preservation in silk†

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