Recycling of Polymerase Chain Reaction (PCR) kits

During the outbreak of the SARS-CoV-2 pandemic, PCR (polymerase chain reaction) kits have been used as a common diagnosing method, with daily worldwide usage in the millions. It is well known that at the beginning of the pandemic there was a shortage of PCR kits. So far, the ecosystem of PCR kit is linear use, that is kits are produced, used one-time, and disposed in biolab wastes. Here we show that, to mitigate the risk of future shortages, it is possible to envision recyclable PCR kits, based on a more sustainable use of nucleic acid resources. A PCR kit is mainly composed of primers, nucleotides, and enzymes. In the case of a positive test, the free nucleotides are polymerized onto the primers to form longer DNA strands. Our approach depolymerizes such strands keeping the primers and regenerating the nucleotides, i.e., returning the nucleic acid materials to the original state. The polymerized long DNA strands are hydrolyzed into nucleotides monophosphates that are then phosphorylated in triphosphates using a method that is a development of a recently published one. We used oligonucleotides with 3-terminal phosphorothioate (PS) backbone modification as non-hydrolysable PCR primers, so to undergo the recycling process unchanged. We have successfully recycled both PCR primers ([~]65% yield for 4-PS modification, and [~]40% yield for 2-PS modification) and nucleotides ([~]75% yield). We demonstrate that the method allows for direct re-use of the PCR kits. We also show that the recycled primers can be isolated and then added to end point or quantitative PCR. This recycling approach provides a new path for circularly reusing PCR nucleic acids.