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Temperature-Controlled Conversion of Boc-Protected Methylene Blue: Advancing Solid-State Time-Temperature Indicators |
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| Authors: | Dr Jean Michel Merkes Dr Srinivas Banala |
| Institution: | 1. Institute of Organic Chemistry, RWTH Aachen University, 52074 Aachen, Germany.
Institute for Experimental Molecular Imaging, University Clinic, RWTH Aachen University, 52074 Aachen, Germany Fraunhofer Institute for Digital Medicine MEVIS, Max-von-Laue-Str. 2, 28359 Bremen, Germany;2. Institute of Organic Chemistry, RWTH Aachen University, 52074 Aachen, Germany. |
| Abstract: | Cold-chain management is of high importance in preserving perishable products and in retaining quality. A visible marker on packages indicating complete maintenance of the cold chain assures safe consumption of products by end-users and assists in reducing waste. Time-temperature indicators (TTIs) are integrated markers that provide information about exposure of packages to adverse temperature and have been gaining increased attention by consumers. Here we present a methylene-blue-based derivative, N,N,N′,N′-tetramethyl-N10-Boc-phenothiazine-3,7-diamine (BocPTDA), that can be used as a solid-state organic TTI dye, exhibiting an irreversible change from colorless to blue green upon heating. The conversion properties, studied using a silicagel-coated plate, confirmed that BocPTDA undergoes a color change above 20 °C. At temperatures of 4 °C and below, no visible changes are exhibited, making BocPTDA a well-suited marker for monitoring abrupt temperature deviations indicating improper cold-chain management. Thus, application of BocPTDA-based TTI systems on packages could inform consumers about the cold-chain maintenance, assuring quality and safe consumption. |
| Keywords: | cold-chain transport food packaging methylene blue solid-state indicators traceless conversion |