Enzymes are catalysts bearing excellent properties (high activity, selectivity and specificity) that modulate the most complex chemical processes under the most benign conditions. They participate in every biological process and mediate various functions in living organisms. However, the poor stability largely limits the application of enzymes. As our knowledge on the structure and function of enzymes accumulated, more and more applications require additional properties beyond what nature has gifted.

In this dissertation, a novel strategy was successfully developed to address the stability issues while simultaneously introduce new functionality to enzymes. This is achieved by an aqueous in-situ polymerization around a single enzyme molecule, yielding a novel class of enzyme nanocapsules containing a single enzyme core and a thin layer of network polymer shell.

Nanocapsules of over twenty enzymes were successfully synthesized for various therapeutic, analytic and bio-catalytic applications briefly outlined below:

1. With the presented technique, we obtain enzyme nanocapsules with highly-retained activity and significantly enhanced stability against various inactivating factors. These properties provide the pre-conditions for prolonged storage and facile handling of enzymes, enabling the application of enzymes in non-physiological environment, such as field decontamination and sensor fabrication.

2. Our research demonstrated a general, effective, low-toxic intracellular protein delivery based on cationic single-protein nanocapsules. Additionally, the nanocapsules delivered intracellularly can exert their biological functions in cells, harboring great potentials for cellular imaging, cancer therapies, anti-aging, cosmetics, and many other applications.

3. By conjugating PEG and PEG-lipid on the nanocapsule surface, we obtained nanocapsules with high intracellular delivery efficiency and decreased cytotoxicity. The delivered protein is uniformly distributed in cytosol after cellular uptake. Moreover, similar levels of cellular uptake were achieved even in the presence of endocytosis inhibitors.

4. By conjugating quantum dot on bioluminescent nanocapsules, we obtain QD-nanocapsule conjugates with continuously tuned red-shifted emission, suitable for in-vivo bioluminescence imaging.

Overall, my research establishes a novel strategy to stabilize enzymes and create new surface functions of enzyme. With this technology, we can envision a promising prospect in industrial, environmental, therapeutic and analytical applications of the great gift from nature - the enzymes.