Self-assembly triggered by self-assembly: Optically active, paramagnetic micelles encapsulated in protein cage nanoparticles

•Optically active, paramagnetic micelles have been encapsulated inside protein cages.•Encapsulation occurs through a hierarchical self-assembly process.•These protein cages are formed by the cowpea chlorotic mottle virus (CCMV) protein.•The resulting biohybrid nanostructures are potential contrast agents for MRI.

In this contribution, optically active and paramagnetic micelles of the ligand 1,4,7,10-tetraaza-1-(1-carboxymethylundecane)-4,7,10-triacetic acid cyclododecane (DOTAC10) have been incorporated inside capsids of the cowpea chlorotic mottle virus (CCMV) protein through a hierarchical process of self-assembly triggered by self-assembly. The DOTAC10 ligand was used to complex GdIII, in order to form paramagnetic micelles, as well as to encapsulate an amphiphilic ZnII phthalocyanine (ZnPc) dye that optically confirmed the encapsulation of the micelles. The incorporation of ZnPc molecules in the paramagnetic micelles led to high capsid loading of both GdIII and ZnPc, as the micelles were stabilized by the amphiphilic dye encapsulation. The resulting protein cage nanoparticles (PCNs) show an improved r1 relaxivity, suggesting the possible use of these nanostructures as contrast agents (CAs) for magnetic resonance imaging (MRI). Since the encapsulated ZnPc dye also has a potential therapeutic value, the present results represent a first step towards the consecution of fully self-assembled PCNs for multimodal imaging and therapy.

Graphical abstractOptically active, paramagnetic micelles have been incorporated inside capsids of the cowpea chlorotic mottle virus (CCMV) protein, through a hierarchical process of self-assembly triggered by self-assembly. The resulting biohybrid nanostructures are potential contrast agents for magnetic resonance imaging (MRI).Figure optionsDownload full-size imageDownload as PowerPoint slide