Protein nanocapsules containing doxorubicin as a pH-responsive delivery system

Area of Science:

• Biochemistry
• Nanotechnology
• Materials Science

Background:

• Pyruvate dehydrogenase E2 component engineered into a hollow dodecahedral protein assembly.
• Exploration of protein assemblies as scaffolds for drug delivery systems.

Purpose of the Study:

• To assess the feasibility of a protein scaffold (D381C) for drug delivery.
• To load and release an antitumor drug (doxorubicin) and a fluorescent dye (Alexa Fluor 532) from the nanocapsule.

Main Methods:

• Genetic engineering of pyruvate dehydrogenase E2 component to create a caged protein assembly.
• Covalent attachment of doxorubicin and Alexa Fluor 532 to the internal cavity via maleimide chemistry.
• Characterization of particle stability, drug release kinetics at different pH, and cellular uptake studies using fluorescence microscopy.
• Cytotoxicity assessment of the drug-loaded scaffold in MDA-MB-231 breast cancer cells.

Main Results:

• The protein scaffold (D381C) maintained structural integrity after loading guest molecules.
• pH-dependent doxorubicin release observed, with 90% release at pH 5.0 within 72 hours.
• Significant cellular uptake of the nanocapsule by breast cancer cells, suggesting endocytosis.
• Encapsulated doxorubicin demonstrated cytotoxicity (IC50 = 1.3 ± 0.3 microM), while the scaffold alone was non-toxic.

Conclusions:

• Macromolecular protein assemblies offer a viable alternative to polymeric nanoparticles for drug delivery.
• The engineered D381C scaffold shows potential for designing targeted nanomaterials for cancer therapy.
• This approach provides a novel platform for creating well-defined nanomaterials for therapeutic applications.