Subzymes: Regulating DNAzymes for point of care nucleic acid sensing

Abstract

Rapid, sensitive and affordable nucleic acid sensors that can operate in a point of care (POC) setting are highly desired; however, their availability and implementation remain limited. We report the development of a strategy for building sensors which use novel catalytic nucleic acid structures, herein referred to as ‘Subzymes’. We examine the effectiveness of Subzymes to mediate signal amplification in a universal manner allowing faster rates of detection. We created Subzymes by manufacturing composite oligonucleotides that contain a catalytic nucleic acid component and a substrate component. We demonstrate that the activity of some catalytic DNAzyme components can be inhibited by attaching the Subzymes to micro-particles. Subsequent cleavage of a Subzyme’s internal substrate results in the release and activation of the surface-bound DNAzyme, thus providing a mechanism to control the catalytic activity of the DNAzyme. We demonstrate that released DNAzymes are capable of cleaving fluorescent-labelled reporter substrates to generate a signal, thus confirming the restoration of their catalytic activity. The addition of Subzymes to reactions where the detection of a target is achieved by multi-component nucleic acid enzymes, known as PlexZymes, showed improved target sensitivities in a shorter amount of time (10 pM of target detected in under 60 min), demonstrating rapid detection of nucleic acid targets without the use of protein-enzymes. Subzymes are constructed from low-cost materials and operate under isothermal reaction conditions which are advantageous for on-site diagnostic testing. Thus, Subzymes offer a universal, rapid and affordable tool for nucleic acid sensing, providing new avenues for POC testing.