Viruses are contagious, sometimes highly infectious pathogens that spread quickly and can lead to outbreaks of disease affecting many people. Viral pathogens can persist on inanimate surfaces, which is why compliance with hygiene guidelines is an essential step in combating virus-related in-fections. Targeted cleaning/disinfection measures facilitate disruption of infection chains; however, these require effective control measures as part of hygiene management.

The aim of the ongoing research project is to visualize viral contamination on surfaces using allo-steric aptamers: The allosteric aptamers recognize viral pathogens and trigger the aggregation of a large number of gold nanoparticles (AuNPs), which is accompanied by a visually perceptible color change. The cause of the coloration is the so-called plasmon resonance, a phenomenon that only occurs with metallic nanoparticles. If the agent to be developed (e.g., after a cleaning/disinfection measure as a process control) is dropped onto a surface (e.g., from a squeeze bottle), a color change becomes visible after a short time (ideally within a few minutes) in the presence of poten-tially infectious viruses.

Allosteric aptamers are synthetic DNA strands with a specific base sequence that change their three-dimensional structure upon binding to their target protein, a property that is exploited to ex-pose an initiator sequence. The initiator sequence triggers a chain reaction in which short DNA strands with specific base sequences (oligonucleotides), to which gold nanoparticles (AuNPs) are bound, assemble into tree-like branched networks (plasmonically active dendrons).

To obtain allosteric aptamers, aptamers described in the literature were analyzed for their binding to the SARS-CoV-2 spike protein, and their sequences were modified using computer-aided methods. This process, known as “post-selection engineering,” has not yet yielded any aptamers that bind to the target protein with sufficient affinity. A method is currently under development that allows allo-steric aptamers to be selected from a large number of DNA strands with different base sequences (DNA-library). In addition, oligonucleotides have been designed that form branched networks (den-drons) in the presence of the initiator sequence.

The research report is available on request from FRT.