Bio-orthogonal triazolinedione (TAD) crosslinked protein nanocapsules affect protein adsorption and cell interaction

Albumin-based protein nanocarriers have been widely exploited as drug delivery systems, since they show excellent degradability, low toxicity, but at the same time provide high loading capacity and relevant uptake into cells. For the formation of protein nanocapsules, bio-orthogonal reactions are important so that the material to be encapsulated is not effected by the shell formation. We show that protein nanocapsules with narrow size distributions and low protein adsorption upon contact with blood serum can be synthesized by inverse miniemulsion and interfacial crosslinking of the protein using triazolinediones (TADs) as powerful dienophiles and enophiles, which smoothly perform electrophilic aromatic substitutions and Diels-Alder reactions under ambient conditions. Additionally, we compare the physicochemical and biological properties of TAD-crosslinked protein nanocapsules with conventional diisocyanate crosslinked nanocapsules. We discovered that the type of crosslinker reaction controls the cell uptake of protein nanocapsules towards cancer cells and the interaction with blood proteins since the crosslinkers react with different functional groups within the proteins leading to different surfaces of the protein nanocarriers.