Scientists have developed vaccines for COVID-19 at record speed. The first two vaccines widely distributed in the USA are mRNA-based and require ultra-cold storage (-70 C for one and -20 C for the other). Now, the researchers are reporting ACS Omega They developed a tamper-resistant temperature indicator that alerts healthcare professionals when a vaccine vial reaches an unsafe temperature for a certain period of time, which can help ensure the delivery of effective mRNA vaccines.
The two COVID mRNA vaccines contain instructions for creating harmless parts of the SARS-CoV-2 spike protein. When the vaccine is injected into the body, human cells temporarily use mRNA instructions to make the spike protein they display on their surface and trigger an immune response. However, mRNA is highly unstable as vaccines require extremely cold storage and transport conditions to remain effective. Sung Yeon Hwang, Dongyeop Oh, Jeyoung Park and colleagues wanted to develop a time-temperature indicator (TTI) to identify mRNA vaccines exposed to undesirable temperatures during storage or transportation so that they could be discarded.
To make their TTI, the researchers added a mixture of ethylene glycol (antifreeze), water, and blue dye to a small tube and frozen it in liquid nitrogen. Then they added white cellulose absorbent to the top of the frozen cooler, inverted the tube and glued it to a larger glass bottle containing simulated vaccine at -70 C. At temperatures above -60 C, the antifreeze mixture melted and the paint spread over the white absorbent, turning it light blue. The color change occurred approximately 2 minutes after the simulated vaccine was exposed to a higher temperature. More importantly, exposures shorter than 2 minutes that were unlikely to impair vaccine efficacy did not turn TTI blue. If the tube was re-frozen at -70 C, the color change continued, making the system tamper-proof. By changing coolants or mixing ratios or using different absorbers, TTI can be adapted to monitor the ideal storage conditions of different mRNA vaccines, the researchers say.
The authors acknowledge that it has received funding from the Korea Chemical Technology Research Institute.
Materials provided by American Chemical Society. Note: Content can be edited for style and length.