The amazing disappearing swab: Dissolving swabs for enhanced DNA Recovery

Daisy Bond

The efficient recovery of genetic material from forensic swabs is a persistent and well-documented challenge. Standard extraction methods suffer inefficient deoxyribonucleic acid (DNA) release, with studies reporting that over 50% of the collected cellular material can be irreversibly lost due to physical entrapment and chemical binding within the swab matrix. This DNA retention critically impacts the analysis of low-template or "touch" DNA samples, often leading to partial or failed profiles. While a substantial portion of the literature has explored incremental optimisations, such as modified swabbing solutions and enhanced extraction protocols, these strategies fail to address the fundamental problem and still contend with the inefficient elution of DNA from a solid substrate. This systematic literature review examines a novel strategy for addressing this bottleneck by targeting the chemical dissolution of the swab matrix itself. The review synthesises literature from forensic science, materials science, and chemical engineering to evaluate potential chemical and enzymatic reagents for the four most common forensic swab types: cotton, rayon, flocked nylon, and polyurethane (PU) foam. The primary goal was to identify reagents capable of digesting the swab fibres under conditions that preserve the integrity of the target DNA. For cellulosic swabs (cotton and rayon), promising options include enzymatic digestion with cellulase, alkaline sodium hydroxide (NaOH)/urea solvents, or deep eutectic solvents (DESs). For PU foam swabs, promising reagents include enzymatic digestion, DESs, and polar solvents, including Dimethyl sulfoxide (DMSO) or Dimethylformamide (DMF). Conversely, polyamide (nylon) swabs presented the most significant challenge, as their chemical inertness typically requires aggressive solvents, such as strong acids, that are destructive to the DNA molecule. This review identifies potential, albeit less-proven, alternatives for nylon, including Hexafluoroisopropanol (HFIP) and aqueous salt systems. A key finding is that while many of these dissolution methods are established in materials science, primarily for recycling, there is a significant research gap regarding their compatibility with forensic workflows. Specifically, the literature lacks data on the preservation of DNA integrity during these processes and the specific application of these solvents to the fibrous matrix of swabs. Therefore, this literature review provides a comprehensive theoretical foundation and establishes the clear necessity for a novel proof-of-concept study to validate these strategies for forensic application.

The amazing disappearing swab: Dissolving swabs for enhanced DNA Recovery

Files and links (1)

Abstract

Details

Metrics