Background & Hypothesis: Enzymes are biological catalysts that have many promising biomedical applications. Since most enzymes are derived from non-human sources, their clinical translation faces two main challenges: limited bioactivity due to degradation by proteases and immunogenicity. Therefore, there is a need for a versatile enzyme-encapsulation strategy that increases the functional half-life and safety of enzymes while preserving their efficacy. We developed a method to encapsulate enzymes in nanoporous silica nanoparticles that shield the enzyme from large macromolecules yet still allows the entrance of small molecule substrates. We hypothesize that this versatile encapsulation method will improve the stability of enzymes in blood, eliminate immune responses, and prolong their functional half-life. We used catalase (CAT) as a model enzyme because it has oxygen-generating properties that can be used for hypoxia relief and radiosensitization of tumors. Materials & Methods: We directly modified the surface of the enzyme with N-acryloyloxysuccinimide and (3-aminopropyl)trimethoxysilane to generate a silica precursor, then coated it with silica by hydrolyzing tetraethyl orthosilicate in basic conditions. Lastly, we conjugated polyethylene glycol groups to the surface of the particles to improve biocompatibility. We used dynamic light scattering, nanoparticle tracking analysis, and transmission electron microscopy to characterize the particles, and we measured CAT activity electrochemically. Results & Discussion: We encapsulated CAT in silica nanoparticles (CAT-SiNPs) with a mean diameter of 230 ± 10 nm and a concentration of 1.3 ± 0.8 × 1012 NPs/mL. We measured 44% enzyme activity retained in CAT-SiNPs relative to free CAT. We also conjugated anti-EGFR antibodies to the surface of CAT-SiNPs and demonstrated their targeting to head and neck cancer cells in vitro. Lastly, the ability of CAT-SiNPs to generate oxygen when exposed to H2O2 was demonstrated in vivo using a rat model. Conclusion: We encapsulated CAT in silica nanoparticles with high retention of activity and optimal protection from proteolysis, and conjugated antibodies to the particles’ surface to target cancer cells. The ability of these CAT-SiNPs to generate oxygen has the potential to relieve hypoxia in tissues and sensitize tumors against radiation therapy. We are currently continuing in vivo studies with CAT-SiNPs and applying this technology to the encapsulation of other enzymes.

Using hybrid enzyme-loaded nanoparticles (HELP) for potential therapeutic applications

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.