The Technology behind VPCIR
VPCIR stands for: 1) Viability, as it detects only viable bacteria as enzymes deteriorates, when released from lysed cells; 2) Polymerase, as VPCIR´s polymerase step in amplifying circular DNA yields rapid results; 3) Circle, as restriction enzymes are put to work to produce circular DNA products; 4) Reaction, as VPCIR reaction is much faster than other tests. Rapid results are ensured as each output molecule (O) is copied 500-1000 times and each copy binds one detection probe that gives a detectable signal.
VPCIR is a breakthrough innovation and takes another approach than our main competitor PCR. While one cell only contains exactly one such specific DNA sequence detectable by PCR, it contains numerous molecules of other kinds of chemical substances. In our research we have identified a class of enzymes called endonucleases (restriction enzymes) that not only differ in composition and chemical structure between the individual bacterial species, but also occur in thousands of copies in the living cell rather than in just one copy.
Proof of concept work has demonstrated the ability of VPCIR to discriminate between different bacteria based on the expression of an endonuclease. The discrimination allows identification of food pathogenic bacteria, while being insensitive to point mutations and small genome alterations that may give rise to false negatives in PCR based methods. Unlike PCR, for which each cell harbours only one to few target molecules (DNA), with VPCIR each cell harbours more than 1,000 target enzymes.
Also, unlike in PCR and enzyme-linked immunosorbent assay (ELISA) methods, with VPCIR enzymatic activity is detecting only living cells, which is not necessarily the case with PCR and ELISA methods, thus potentially presenting a false-positive result. Another unique feature of VPCIR is that each target enzyme can convert many DNA input molecules (iDNA) into detectable DNA output molecules (oDNA) – 500-1000 per conversions per target enzyme.
Additionally, as the number of circular DNA products correlates with the number of endonucleases, the VPCIR test is by default with a built-in quantitative aspect, meaning it renders a built-in option for enumeration of the pathogens in the sample. Moreover, by detecting the right assortment of endonucleases, the VPCIR has also a built-in “multiplex” feature.
Accordingly, VPCIR is a versatile test based on innovative technology for detection of individual bacteria and combinations hereof.
Using the VPCIR for testing food items for pathogen contamination is fast and easy to perform. Moreover, for an established analytic laboratory there will be no additional costs, as all the consumables are provided in the VPCIR kit, whereas standard off-the-shelf materials and equipment may be deployed that most laboratories are equipped with, rendering VPCIR plug-and-play capability.
The VPCIR test kit consists of the hydrogel beads functionalized with specific DNA substrates, (proprietary) bacteria species-specific VPCIR reagent preparation, (proprietary) pre-test sample procedure manual, and a manual on how to use and read-out the test results using the standard off-the-shelf benchtop flow cytometer reader.