Date of Award
Santa Clara : Santa Clara University, 2019.
Master of Science (MS)
Milkguard is an alginate-based biosensor developed to detect E. coli in human breast milk via the metabolism of X-gal (5-Bromo-4-Chloro-3-Indolyl β-D-Galactopyranoside) by β-galactosidase. In order to deconvolute metabolic reproducibility from scaling laws, the commercial enzyme β-galactosidase was used to mimic the biological function of the bacterial lac operon. Downscaling was explored as an optimization of the biosensor design based on numerical solutions to Fickian-based diffusion models. The characterization of large capsules (d ≅ 3 mm) and atomized microcapsules (d ≅ 300 ± 60 μm) yielded size-specific Michaelis-Menten constants. Small capsules (Km = 3.6 x 10-4 M; Vmax ’’ = 1.2 x 10-3) produced a significantly faster response time versus large capsules when loaded at a substrate concentration of 5 mg/mL (p = 7.7x 10-3 at 𝛼 = 0.01) and 2.5 mg/mL (p = 1.5 x 10-4 at 𝛼 < 0.001). Comparisons of effectiveness factors between small (η = 0.58) and large (η = 0.43) capsules indicates a lesser degree of diffusion limitations in small capsules. Large bootstrapping errors produced by nonlinear regression of Michaelis-Menten models for the capsules suggests that additional mechanisms to diffusion are involved in producing sensor response. A new sensor mechanism combining Fickian diffusion and experimental results is proposed and modeled numerically.
Madamba, Jerard Roniel Del Rosario, "Scale Optimization of Milkguard Biosensor for Detecting E. coli in Human Breast Milk" (2019). Bioengineering Master's Theses. 6.