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Air-Dryable Direct DNA and RNA/DNA qPCR Saliva

Air-Dryable Direct DNA qPCR and RNA/DNA qPCR Saliva mixes are glycerol-free mixes that contain optimized excipients compatible with air and oven drying and they designed for the direct molecular quantitation of DNA and RNA from saliva.

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Air-Dryable Direct DNA qPCR Saliva, MDX130

Available in 5 mL (1,000 Rxns) or 50 mL (10,000 Rxns) aliquots

Air-Dryable Direct RNA/DNA qPCR Saliva, MDX131

Available in 5 mL (1,000 Rxns) or 50 mL (10,000 Rxns) aliquots

Over the last decade, saliva has been extensively studied as a diagnostic specimen due to its non-invasive and simple sample collection/logistics, and similar to serum, saliva contains hormones, antibodies, growth factors, enzymes, microbes that can be used as biomarkers for disease detection. However, there have been challenges in adopting saliva for molecular diagnostics due to the low concentration of analytes and high concentration of PCR inhibitors in saliva. Cumbersome sample preparation steps have been required to homogenize the specimen and adequately purify the DNA/RNA.

Meridian’s new Air-Dryable direct saliva molecular mixes are unique in that they enable the highly sensitive detection of target DNA or RNA from crudely processed saliva or sputum samples. These mixes have been formulated specifically to overcome the inhibitors found in saliva samples – no further optimization is required aside from the addition of primers and probes. Furthermore, these mixes can be used in a wet format or dried down by oven or air drying to create ambient-temperature stable assays.

FAQs: Important Principles for Air-Drying Molecular Assays

No, air-drying requires specific stabilizers, excipients, and preservatives which are different from those required for lyophilization.

Yes, we recommend optimizing the oven temperature and drying time for each new assay formulation (mix including primers and probes), vessel used and lot size. High drying temperatures may affect the integrity of the mix and its components, including enzymes.

Ideally, 70% moisture should be removed from Air-Dryable 1-step RT-qPCR Mix (MDX095) and 95% from the Air-Dryable Mix (MDX082). However, the optimal moisture loss requires optimization for each assay. Retaining too much moisture may impact the shelf-life of the assay and over-drying may make the mixture difficult to rehydrate and cause a loss of performance. Moisture loss can be calculated by comparing the weight of the initial wet mix in the vessel to the dry mix (refer to the basic workflow for further information). Please note that the air-dried material must be packaged immediately after the drying cycle.

The air-dried mix rehydrates in seconds after the addition of the sample. We do recommend, if possible, to gently shake/mix the vessels in order to resuspend the reaction mix before running the reaction, or alternatively mix the solution when adding the patient sample.

If a mix becomes over-dried, the integrity of the enzymes will be compromised. Conceptually, the ideal “dryness” of a mix will be the highest percentage of moisture loss achieved without losing assay performance. If the Ct value of your dry mix is lower to the comparable wet mix, then the mix has been over-dried and further optimization is required.

We did not observe any effect of the fluorophore type (Cy5, FAM, JOE or ROX) on the performance of the mix after air-drying.

We did not observe any contamination during air-drying however we do recommend good laboratory cleaning practices to minimize possible environmental contamination. Examples include surface cleaning or allocating separate locations for the oven drying, qPCR reaction setup, and analysis. In addition, we recommend maintaining the oven following the cleaning instructions provided by the manufacturer.

We did not observe any cross-contamination from fan-forced oven drying. Given the mix resides at the bottom of the vessel, it is very unlikely that cross-contamination can occur between the wells. In addition, in accordance with good manufacturing practices, we would discourage oven drying two different types of assay in the same drying cycle.

Other vessels can be used such as plates, vials or various microchips, but the drying conditions for each vessel/assay would need to be optimized. Once the ideal conditions and parameters are established, they would need to be verified during validation and scale up.

We recommend using a precision drying oven (temperature uniformity of +/- 1.5°C) with convection, fan-forced or vacuum capabilities. In our testing, we used a Memmert UF260Plus oven with fan and air flap settings at 100% and 20% respectively. Please note that different ovens will have different specifications and adjustable parameters that will need to be optimized based your assay, reaction volume, vessel type, batch size, relative humidity, and altitude.

If the first attempt is not successful and does not provide the correct moisture loss value, we do not recommend putting the tubes back in the oven for additional drying or adding water. We recommend re-starting the experiment in order to control all of the variables so that they are reproducible. In addition, opening the door during the drying process is also not recommended unless it is done in a controllable manner and will be part of the process moving forward.

Unlike the effects with lyophilization, there is no impact of the environment to the moisture loss with air-drying.

We recommend that different drying cycles are performed to test the effect of altering any assay variable such as vessel type, reaction volume, primer/probes, and lot size. This will ensure that the conditions and outcomes are reproducible.

No, the balance does not have to be next to the oven, just close the vessel once it is out of the oven and go to the balance (even if in a different room) for measurement.

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