Virus imprinted particles

Living organisms are capable of identifying and neutralizing exogenous threats. Such a distinguishing feature, developed over millions of years of evolution, is achieved thanks to the immune system, and in particular through the molecular recognition capabilities of antibodies. Besides its importance for immunity, molecular recognition is also crucial to living organisms in other aspects, for example providing them with the possibility of controlling and regulating complex feedback to external and extracellular stimuli (e.g. olfactory stimulatory molecules or hormones through G protein-coupled membrane receptors). Over the past decades, the possibility of creating man-made systems with molecular recognition properties similar to Nature has been a driving force in the design of recognition materials. Among possible target molecules, viruses represent one of the most challenging. Indeed, despite advancement achieved in the design of recognition materials for low molecular weight molecules, a synthetic strategy leading to the production of recognition materials targeting viruses remains challenging. In fact, the main stumbling blocks in the design of materials possessing virus recognition properties are the large size of the target and the fragility of its self-assembled architecture.
The presence of viruses in the environment (e.g. water, air and soil) or in biological fluids (e.g. blood, milk) is a concern for human health in various industrial sectors including pharmaceuticals, the environment, and agro-food. Different, tedious and energy-consuming strategies are currently applied to detect, inactivate or remove viruses, including quantitative polymerase chain reaction (qPCR), enzyme-linked immuno sorbent assay (ELISA), ultraviolet treatment and nanofiltration. The use of synthetic virus recognition material for the removal and detection of such pathogens could represent a new approach that will benefit from the robustness of synthetic recognition materials, ease of production, and cost and time efficiency.
Following a surface molecular imprinting approach (i.e. template-assisted polymerization of specific monomers), it was developed a synthetic strategy to produce nanoparticulate organic/inorganic hybrids that recognize a major category of viruses (i.e. icosahedral non-enveloped) in aqueous environments at concentrations down to the picomolar range. The strategy is based on a sequential process that consists of covalent immobilization of an icosahedral virus at the surface of silica nanoparticles followed by the thickness-controlled growth of a polysilsesquioxane layer at the surface of the particles. A variety of organosilanes, sharing chemical similarities with lateral chains of natural amino acids, were used as building blocks to grow the polysilsesquioxane layer, named the recognition layer. After removing the virus, this procedure allowed the formation of negative, open replica imprints of the virus. The replication-imprinting process described goes beyond simple shape imprinting. Indeed, several experimental sources of evidence have suggested that the viruses were “self-sorting” the building blocks during recognition layer growth. Therefore, the formation of a chemical imprint of the surface of the virus was achieved.
In addition, the developed chemical strategy allows the preservation of the native structure of the 180-subunits viral assembly throughout the organosilanes polycondensation. The so-produced particles, named virus-imprinted particles or VIPs, were characterized by means of scanning electron microscopy. Their molecular recognition performances were tested in a batch rebinding study in aqueous conditions using enzyme-linked immunosorbent assay (ELISA) for virus quantification. Those binding assay results showed that VIPs specifically recognized the template virus. The control of the depth of the imprints provides control of the affinity of the produced VIPs for its target virus. The interaction assays ultimately confirmed that immobilized viruses were self-sorting the organosilanes during the growth of the recognition layer, thus creating specific binding sites possessing both chemical- and size-recognition properties at the surfaces of the VIPs.