Room-temperature-storable PCR Mixes for SARS-CoV-2 Detection

Xu, Jiasu; Wang, Jin; Zhong, Zecheng; Su, Xiaosong; Yang, Kunyu; Chen, Zhongfu; Zhang, Dongxu; Li, Tingdong; Wang, Yingbin; Zhang, Shiyin; Ge, Shengxiang; Zhang, Jun; Xia, Ningshao

OBJECTIVES: A novel coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) emerged in late 2019, causing an outbreak of pneumonia [coronavirus disease 2019 (COVID-19)] globally. Although the use of ready-made reaction mixes can enable more rapid PCR-based diagnosis of COVID-19, the need to transport and store these mixes at low temperatures presents challenges to already overburdened logistics networks. METHODS: Here, we present an optimized freeze-drying procedure that allows SARS-CoV-2 PCR mixes to be transported and stored at ambient temperatures, without loss of activity. Additive-supplemented PCR mixes were freeze-dried. The residual moisture of the freeze-dried PCR mixes was measured by Karl-Fischer titration. RESULTS: We found that freeze-dried PCR mixes with ∼1.2% residual moisture are optimal for storage, transport, and reconstitution. The sensitivity, specificity, and repeatability of the freeze-dried reagents were similar to those of freshly prepared, wet reagents. The freeze-dried mixes retained activity at room temperature (18∼25℃) for 28 days, and for 14 and 10 days when stored at 37℃ and 56℃, respectively. CONCLUSION: The uptake of this approach will ease logistical challenges faced by transport networks and make more cold storage space available at diagnosis and hospital laboratories.