Enzymatic time-temperature indicator with cysteine-loaded chitosan microspheres/silver nanoparticles

Area of Science:

• Materials Science
• Chemical Engineering
• Biotechnology

Background:

• Developing reliable time-temperature indicators (TTIs) is crucial for monitoring product quality and safety.
• Existing TTIs often lack sensitivity or specificity for certain applications.
• Novel pH-sensitive materials offer potential for improved TTI performance.

Purpose of the Study:

• To develop a new time-temperature indicator (TTI) based on an acid-base reaction.
• To utilize cysteine-loaded chitosan (Cys-CS) microspheres and silver nanoparticles (AgNPs) for colorimetric detection.
• To investigate the relationship between microsphere disintegration, cysteine release, and color change.

Main Methods:

• Cysteine-loaded chitosan (Cys-CS) microspheres were synthesized using a water-in-oil emulsion method with paraffin oil.
• Fourier-transform infrared (FTIR) spectroscopy confirmed cysteine encapsulation within the microspheres.
• The pH-triggered disintegration of Cys-CS microspheres and the color change of the TTI were evaluated through titration and pH monitoring.

Main Results:

• Cys-CS microspheres were successfully produced in paraffin oil, with an average diameter of 335 ± 100 µm.
• FTIR analysis verified the successful encapsulation of cysteine within the chitosan microspheres.
• The Cys-CS microspheres disintegrated at a critical pH of 6.18, and the TTI exhibited a distinct color change at pH 6.10, closely matching the disintegration point.

Conclusions:

• A novel TTI based on the acid-base reaction of cysteine-loaded chitosan microspheres and silver nanoparticles was successfully developed.
• The TTI demonstrates a clear color change at a specific pH, indicating its potential as a visual spoilage indicator.
• The findings suggest that this TTI system can effectively signal critical pH changes relevant to product degradation.