Temperature-Switchable Assembly of Supramolecular Virus-Polymer Complexes

Here a method is presented for the temperature-switchable assembly of viral particles into large hierarchical complexes. Dual-functional diblock copolymers consisting of poly(diethyleneglycol methyl ether methacrylate) (poly(DEGMA)) and poly((2-dimethylamino) ethyl methacrylate) (poly(DMAEMA)) blocks self-assemble electrostatically with cowpea chlorotic mottle virus (CCMV) particles into micrometer-sized objects as a function of temperature. The poly(DMAEMA) block carries a positive charge, which can interact electrostatically with the negatively charged outer surface of the CCMV capsid. When the solution temperature is increased above 40 degrees C, to cross the cloud point temperature (T-cp) of the DEGMA block, the polymer chains collapse on the surface of the virus particle, which makes them partially hydrophobic, and consequently causes the formation of large hierarchical assemblies. Disassembly of the virus-polymer complexes can be induced by reducing the solution temperature below the T-cp, which allows the poly(DEGMA) blocks to rehydrate and free virus particles to be released. The assembly process is fully reversible and can sustain several heating-cooling cycles. Importantly, this method relies on reversible supramolecular interactions and therefore avoids the irreversible covalent modification of the particle surface. This study illustrates the potential of temperature-responsive polymers for controlled binding and releasing of virus particles.