Nature's biomaterials such as peptides and proteins represent a valuable source of highly defined macromolecules. Herein we developed a nanoparticle drug delivery system based on the assembly of surface-modified proteins that can be transferred into organic solvents and represent the structural material of the carrier system. The particles are prepared by an oil-in-water nanoemulsion technique without the need of additional denaturation or cross-linking steps for stabilization. We achieve the necessary lipophilic solubility switch of the protein material by high surface PEGylation under conservation of the native three-dimensional protein structure. This study focuses on lysozyme as model enzyme for the preparation of empty and doxorubicin-loaded nanoparticles with an average diameter of 100 nm. The particles are stable in physiological buffers and only release their therapeutic payload into cancer cells after a time-dependent cellular uptake. We also transferred this approach to various proteins, exemplifying the universal applicability of our new preparation method for protein-based nanoparticles.

DNP are multifunctional liver-specific drug carriers which lack toxic side effects and may be utilized in clinical applications targeting liver macrophages.

We evaluated different methods for a high surface PEGylation of lysozyme. The resulting lipophilic enzymes can be used for the formation of stable nanoparticles.

Proteins represent a versatile biopolymer material for the preparation of nanoparticles due to their biocompatibility, biodegradability, and low immunogenicity. This study presents a protein-based nanoparticle system consisting of high surface PEGylated lysozyme polyethylene glycol-modified lysozyme (LYZ ). This protein modification leads to a solubility switch, which allows a nanoparticle preparation using a mild double emulsion method without the need of surfactants. The method allows the encapsulation of large hydrophilic payloads inside of the protein-based nanoparticle system. Native lysozyme (LYZ) was chosen as payload because of its innate activity as natural antibiotic. The mild particle preparation procedure retains the structure and activity of the enzyme which was successfully tested against the gram-positive bacteria strain M. Luteus. In comparison, the particle system shows no toxicity to human cells. This first report of a full protein-based particle material for the transport of large hydrophilic payloads opens up new therapeutic applications for biopolymer-based delivery systems.