Use of nail matrix in toxicological screening: a study on volunteers practicing chemsex in the pre-and post-COVID era

New psychoactive substances (NPS) encompass a vast array of primarily synthetic molecules that possess highly dangerous pharmacological and toxicological characteristics for consumer health. These substances fall into various structural categories, including synthetic cannabinoids, synthetic cathinones, opioids, tryptamines, piperazines, arylcyclohexylamines, and especially phenethylamines. However, they differ from the foundational molecules listed in UN tables. The molecular modifications create structural analogues that are entirely autonomous in terms of chemistry, toxicology, and legality. Globally, the consumption of these substances is recognized as a significant emergency, prompting a need for new strategies and suitable legal frameworks currently under development. The pandemic has dramatically altered patterns of substance abuse and has introduced new channels for supply and demand, which our detection and surveillance systems may not be fully equipped to handle. A substantial portion of the trafficking of these novel synthetic drugs takes place through communication networks, particularly the Internet. Social media increasingly serves as a critical platform for interaction between drug users and traffickers, facilitating discussions on drug costs, purity, desired effects, intake methods, dosages, and the characteristics of any new NPS emerging in these marketing channels, including the Dark Web. In this context, forensic toxicology, which originated in 1814 with Mathieu Orfilia's work "Trait Des Poisons," has evolved into a critical branch of forensic medicine and plays a pivotal role in numerous legal disputes. Ongoing technological advancements and the emergence of new techniques have enabled forensic toxicology to deliver increasingly precise information regarding not only the type of substance an individual has been exposed to but also the method of introduction, the timing of exposure, and the extent of contact. In forensic toxicology, the choice of sample for analysis is determined by the specific questions posed. Hair, given its unique properties, is becoming an essential biological sample for addressing many of these inquiries. Its wide detection window (ranging from three days to several years), non-invasive collection method, and capability to track usage history make hair an exceptionally valuable sample for coroners. However, hair is not always readily available, and when it is, its quality may be insufficient. Conditions such as alopecia, loss due to external factors (like burns), beauty treatments (such as bleaching), and haircuts driven by fashion trends or concealment needs are frequently encountered in forensic settings. This has created a demand for alternative biological samples that can provide the answers typically derived from hair analysis, leading to the identification of the nail matrix as a viable option. In recent years, there has been a surge in studies examining nails as samples for toxicological screening; however, more research is still required to reach the same level of analytical and interpretative proficiency that we possess for hair. This work contributes to that body of knowledge, supported by two key elements: the wide range of substances examined and the ability to correlate the concentrations detected in nail matrices with those found in hair. The research utilizes samples collected from volunteers engaged in Chemsex, a practice prevalent both within the gay community and beyond, which involves using drugs shortly before and/or during sexual activity. The presence of definitive biological samples for various drugs enabled us to confirm, with a high degree of accuracy, whether these substances had been incorporated into the nail matrix, as well as the values obtained from hair analysis. As a result, we gained a deeper understanding of the potential applications of the nail matrix, equipping legal authorities with additional resources to address the challenges they often face.