Top 10 Tips for Sampling DNA and RNA using Buccal Swabs

Buccal cell sampling offers a non-invasive alternative to blood collection; it is cheap, painless, and can easily be done by the subject. However, historically the problem with buccal swabs has been low yields.

The Isohelix range of Buccal Swabs has been designed to give increased yields of high-quality buccal cell and genomic DNA and RNA. Together with the Isohelix DNA Isolation and Stabilization kits, high yields of pure, intact DNA can be collected easily and quickly. Isohelix swabs are suitable for both human and veterinary use and offer significant advantages over other swab designs in terms of cell collection efficiency. Their unique swab matrix, combined with a quick-release surface, maximises yields of nucleic acids. DNA from Isohelix buccal swabs can be used for genotyping, diagnostics, paternity and heredity analysis, forensics, and population studies.

1. Maximize yield

Isohelix swabs incorporate a unique matrix that efficiently collects buccal cell samples and features a quick-release surface. Swabs are designed with a small flat head and strong handle, allowing pressure to be applied easily to the inside of the cheek without causing discomfort.

Isohelix products have been specifically developed to integrate all steps from sample collection and stabilisation to processing and isolation. An integrated workflow improves yields, reduces sample losses, and simplifies handling procedures, resulting in maximum yields and DNA/RNA quality. Buccal swab DNA extraction yields from 1 to 10µg can be routinely obtained from adult swab samples.

2. Stabilize samples

Studies have shown that DNA samples from swabs will degrade rapidly without proper stabilisation, making them useless for downstream applications, so if DNA extraction is to be done longer than 1-2 days after taking a swab sample, then stabilisation is necessary. Depending on your requirements, swabs can be frozen at -20 degrees; alternatively, several stabilization options do not require a cold chain.

If it is important to maintain the structural integrity of your DNA, then BuccalFix DNA stabilization and lysis kits are the ideal solution.

BuccalFix stabilizing buffers completely inhibit all enzymatic and microbial activity that occurs following sampling. As a result, DNA is fully stabilized, and importantly, the structure and integrity of the DNA are fully maintained for further downstream processing applications. DNA can be stored in BuccalFix at Room Temperature for periods in excess of 2 years.

Alternatively, cost-effective RapiDri™ Swab kits (RD-01) include a microporous moisture-wicking pouch that rapidly dries the swab, stabilizing the DNA on the swab matrix, where it is protected from degradation. DNA can be stabilized for 3 months at ambient temperature, allowing safe sample transport and storage.

Finally, Isohelix Dri-Capsules with SK-1S Swab pack Cat. No: SGC-50 are silica gel capsules that offer an easy-to-use alternative to chemical stabilization for the long-term stability of the buccal DNA on the swab head before isolation. DNA stabilized using Dri-Capsules is stable for 3 years at ambient temperature.

3. Choose the right nucleic acid extraction kit

Isohelix Buccal Cell Isolation Kits are fully optimised for use with buccal swab samples.

Depending on how your buccal cell sample has been collected and stored and the nature of your downstream analysis, there is a range of extraction kits to choose from.

BuccalFix Plus (BFP) and Buccal-Prep Plus (BPP) use a precipitation method ideal for scaling different sample volumes and is rapid and easy to automate, giving high yields and purity ratios. BuccalFix Plus is designed for use with swabs stored in BuccalFix buffers, whereas Buccal-Prep Plus is suitable for all buccal swab samples.

Silica membrane-based spin columns (e.g., as included in the Xtreme (XME) and Xtreme-RNA (XMR) kits allow the purification of very high-purity DNA or RNA that can be used for sequencing or array-based applications. Using a silica column ensures your nucleic acid is free of traces of PCR inhibitors and maintains the integrity of your DNA or RNA.

Finally, magnetic-bead-based methods such as Buccal-Mag (BMG) can be used to produce high yields and purities, are fast and reliable for medium-high throughout applications, and extraction is performed in the original sample collection tube, reducing waste and cost. Buccal-Mag kits include high binding capacity magnetic beads with a large surface area for fast attachment enabling rapid isolation of intact genomic DNA.

4. Isolate RNA

BuccalFix RNA stabilization and lysis kits include a non-toxic buffer that stabilizes RNA and DNA for 2 weeks at room temperature. The new Isohelix Xtreme-RNA kit is a spin-column based RNA purification kit for the rapid preparation of total human, viral, or microbial RNA from stabilized saliva and swab samples. Free from toxic reagents such as phenol, chloroform, & β-mercaptoethanol, Xtreme-RNA has been fully optimised for use with GeneFix GFX & RFX saliva collectors and swabs stored in BuccalFix stabilisation solution. Extracted samples are of high purity (expected A260/280: >1.9), ideal for use in downstream applications such as rt-qPCR and gene expression studies. The kit is also scalable and can accommodate various sample input volumes.

5. Prevent buccal swab contamination

Isohelix swabs are treated with ethylene oxide and routinely tested to ensure they are not contaminated with human DNA. To prevent sample contamination, buccal swab samples should be taken >1h after food or drink, and the sampler must take care not to touch the swab head with their fingers while removing the swab from its packaging.

The RapiDri™ pouch also protects the DNA from cross-contamination by acting as a physical transport pack to protect the DNA sample. The pouch actively repels any accidental wetting from the outside due to its hydrophobic structure, preventing any backward cross-flow contamination.

Isohelix swab collection tubes SK-2S, have a unique cap designed to detach swab heads so that they fall into the tube without further handling, avoiding potential contamination from touching the swab and making it easy to handle at the DNA isolation stage.

6. Avoid using hazardous reagents

Collection and stabilization kit should be free from toxic reagents, such as guanidium, for safe use in the field and for shipping and handling. Isohelix^TM devices are completely non-hazardous and non-toxic and do not contain ethanol or other solvents.

7. Buccal swabs for other sample types

Isohelix DNA buccal swabs have been designed for buccal applications but have also been used extensively in many other applications, including; skin, hard surface sampling, teeth and gums, tongue, and stools. MS-Mini swabs have reduced dimensions; the width of the swab has been reduced from 8mm to 6mm and employs a slightly different shaft attachment enabling yields similar to larger swabs. These smaller swabs are particularly useful for small mammals, other animals, and invertebrates. They are easy to automate for mouse genotyping.

8. Safe transport and tracking

One of the key benefits of using buccal swabs rather than blood as a source of nucleic acids is that samples can be collected remotely and mailed for analysis. If a stabilization reagent is included in the collection tube, keeping samples cold is not required, significantly reducing costs and logistical challenges associated with storage and transport. However, collection tubes must be manufactured from robust materials that can withstand the rigours of the mailing process – regulations on leak-proof sample transport specify that collection tubes must withstand defined physical pressures of 95KPA. IsohelixTM TPN-50 transport packs are pressure tested and include secure sealing strips and absorbent material that retains samples leaking from the primary tube within further layers of packaging.

9. Use high quality kits

Kits manufactured to recognised quality standards ensure safe use and high-quality nucleic acid isolation. Isohelix has ISO 9001, and ISO 13485 accreditation, and Isohelix Buccal Swab products are CE/MD and UKCA marked to ensure your samples are collected, transported, and stored securely and can be used to generate excellent results.

10. Reduce the environmental impact

Isohelix reduce the environmental impact of their products as much as possible. Hazardous reagents are avoided, swabs are manufactured using recyclable materials, and with magnetic-bead-based methods such as Buccal-Mag (BMG) extraction is performed in the original sample collection tube, reducing waste.