Tuning the Enzymatic Degradability of Polyhydroxybutyrate

  • Author / Creator
    Anbukarasu, Preetam
  • Enzyme-responsive degradable polymers are of great interest both from fundamental science and real-world application perspectives. Enzyme-responsive polymers, because of their ability to interface with and sense biological processes, can have many applications in systems that operate at the edge of biology and materials science. In this thesis, the methods and physical processes to control and characterize the enzyme response of a biodegradable polymer film – Polyhydroxybutyrate (PHB) – have been explored. The properties of PHB were controlled by altering the processing and physical parameters to yield PHB films that have a range of degradation characteristics, with the aim of integrating this material in food quality sensing and biological applications. A simple, solvent casting process was used to prepare PHB films with acetic acid as a food-safe solvent. The use of acetic acid allowed for more flexible processing conditions and a more extensive range of final properties. The acetic acid based solvent casting process was used to prepare flexible PHB films with thickness ranging from 50 μm to 40 nm, which is challenging to obtain using existing solvents for PHB. Since the degradation characteristics of thin films can vary substantially from their thicker counterparts, the effect of reducing the polymer film thickness on their degradation characteristics was studied. A diffraction-based degradation sensor was developed and validated to determine the change in the degradation of polymer thin films. It was found that the enzymatic degradation rate increases substantially with a decrease in thickness of the PHB film. However, constraining the film thickness down to the nanoscale was found to impede enzymatic degradation, which could be attributed to the lack of ordered, crystalline structures in the constrained film. The knowledge acquired from these degradation studies was utilized to create a time- temperature indicator (TTI) that works based on the temperature dependent degradation behavior of a dye-loaded PHB film. With elapsing time, the degradation of the dye-loaded PHB film was found to result in a gradual change in color of the enzyme solution, which correlated with the integrated time and temperature history to which it was exposed.

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  • Degree
    Doctor of Philosophy
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