Multifunctional protein microspheres for bioanalytical and biomedical applications

Abstract

Microspheres have been a growing field of study in the recent decades. Their small homogeneous structure enabled them to be candidates in many nowadays micro-focused applications including drug delivery, tissue imaging, bead-based assays, biosensors, etc. Apart from their small size, they are also capable of carrying specific properties and functions to accomplish different purposes. These parameters can be varied by making use for different combinations of building materials and fabrication protocols. This thesis presents a novel method for the production of microspheres composed of pure proteins. Proteins are naturally available materials which has great plasticity. The proposed approach aimed to fabricate protein microspheres which has adjustable physical properties such as size and porosity by changing the protocol parameters. Additional biological functions can also be incorporated to the final product whenever necessary. This work also illustrates their possible applications in both analytical and biomedical situations. The protein microspheres successfully produced were characterized for their physical, chemical and biological aspects. Their physical properties including morphology, size, and porosity were done by electronic microscopes and particle analyzers. Their chemical characteristics such as composition, surface charge, etc. were determined by various types of spectroscopy. Their biological properties for example biocompatibility and biodegradability were tested by cell cultures, enzymatic treatments, etc. It was found that protein spheres with size ranged from about 400 nm to 2000 nm could be mass produced (10⁸ microspheres/mL) within two hours. They composed of pure protein with natural properties preserved. They were also harmless to cells and decomposable by enzymatic digestion. Upon successful characterizations of the above properties, protein microspheres were tested for their practical potentials in applying into bioanalytical and biomedical scenarios. In analytical aspect, the microspheres were designed to carry an enzyme (horseradish peroxidase) for colorimetric analyte detection. Due to the porous nature of microspheres, the enzymatic products can be accumulated inside the cavity of microspheres for signal amplification. Furthermore, fluorescent immunoassay was incorporated to form a dual channel detection system. Both signals could be detected quantitatively for analysis. In biomedical aspect, the drug delivery capability of the microspheres was revealed using porcine ear as a skin model. The sizes of microspheres were customizable to a range that is most favorable for penetration into the hair follicles. With the addition of massaging over the skin, the microspheres were able to reach the bottom part of the hair follicles. We have developed a two phase system to release the encapsulated content of microspheres in order to achieve the drug delivery purpose. It was found that the released content was capable of going inside the sebaceous gland. The research results showed that protein microspheres can be prepared facilely without sacrificing their native structure and functions. This will be an advantage for applying them into real life situations where the action of proteins are necessary. This work opens more opportunities in both basic and applied researches as the proposed protocol can act as a platform to produce customizable protein microspheres for specific needs.

Date of Award	2013
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology