The overall objective was to develop a novel therapy for the treatment of phenylketonuria (PKU), a genetic disorder characterized by a loss of hepatic phenylalanine hydroxylase (PAH) activity. PAH catalyzes the conversion of L-phenylalanine (Phe) to L-tyrosine and in the healthy population this would reduce the level of Phe entering the systemic circulation. Loss of PAH activity results in an increase in plasma Phe to the point that neurophysiological side effects are observed. The research was focused on the development of spray dried ethylcellulose (EC) microcapsules that provide phenylalanine ammonia lyase (PAL) that converts Phe to nontoxic trans-cinnamic acid. In this strategic approach, oral administration of these microcapsules will decrease the level of Phe in the gastrointestinal tract to lower its absorption. In the first phase of this research, a generally applicable method was developed to determine the encapsulation efficiency of the protein in polymer matrices to guide formulation development. PAL-loaded microcapsules were produced and characterized to discover whether or not PAL was degraded or inactivated during microcapsule manufacture. Design of experiments was used to study formulation and process variables to improve yield and protein encapsulation efficiency. In the next phase, various approaches to reduce protein leakage were investigated by using different viscosity grades of EC, polymer concentration in the microemulsion to be spray dried, emulsification instruments, and feed flow rates. In subsequent experiments, Phe was encapsulated and its efflux from the microcapsules was determined. The rate of Phe release from the microcapsules was used as a measure of the porosity of the EC microcapsule membrane. In the last phase of the research, low permeability of phenylalanine through the EC membrane was evident. Therefore, the diffusion rate was improved by addition of pore formers to the EC region of the microcapsules.
|Advisor:||D'mello, Anil P.|
|Commitee:||Wigent, Rodney J., Neau, Steven H., Jonnalagadda, Sriramakamal, Bentzley, Catherine M.|
|School:||University of the Sciences in Philadelphia|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 81/10(E), Dissertation Abstracts International|
|Keywords:||Enzyme therapy, Ethylcellulose polymer, Microcapsules, Phenylalanine ammonia lyase, Protein formulation, Spray drying|
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