Analytische Chemie
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Drug facilitated sexual assaults (chemical submission) consists in the criminal administration of psychoactive substances without the permission of the victim. Among these compounds, scopolamine (SCP) (commonly well-known as burundanga} has emerged as the perfect psychotropic substance for aggressors because its ingestion induces automatism in the brain of the victim causing a state of submission. Physiologically, an appealing feature of SCP is their relevant role as a non-competitive muscarinic acetylcholine receptor antagonist with rapid and robust antidepressant effects in humans and other species. Specifically, SCP is able to block or dampen the biological response because of binding to an allosteric recombinant human muscarinic acetylcholine receptor M2/CM2 (Mi-AChR) site that is separate from the active recognition site of acetylcholine, thereby inhibiting the effects of the natural substrate and even of a potent agonist such as bethanechol. Here, a straightforward portable strip in combination with bioinspired hybrid nanomaterials for SCP drug in situ and at site detection was developed. The strips allow direct identification of SCP in diluted saliva down to 40 nM in less than 15 min using a smartphone for readout. For this purpose, we prepared a nanosensor based on mesoporous silica nanoparticles {MSNs) loaded with a fluorescent dye and functionalized with bethanechol. Attachment of the M2-AChR 'cap' to the silica scaffold enabled pore closure through non-covalent recognition. interactions with the anchored bethanechol moieties. In the presence of SCP pores were opened, due to the preferential interaction of the drug with receptor, thus releasing the encapsulated reporter and allowing it to be detected. Additionally, to a single-track strip, the extraordinary modularity of the hybrid biosensor materials in combination with the strip-pattering technologies enabled us to obtain a dual-channel strip for SCP and cannibal drug detection in a simple way, providing comparable analytical performance, while enabling further tailoring to the user's needs.
Rapid tests and assays to be used outside of a laboratory for non-trained personal and also at a point of need are becoming increasingly important in areas such as health, food, security, or the environment. Specially on that regard, paper-based sensors are emerging as a new class of devices because they fulfil the requisites of the "World Health Organization" to be ASSURED: affordable, sensitive, specific, user-friendly, rapid and robust, equipment free and deliverable to end-users. The physical, chemical and mechanical properties of cellulose or glass fiber paper in combination with the facility of preparation are making these materials of great interest while looking for cost-efficient and green alternatives for device production technologies. To improve the sensitivity of these systems, a particularly promising approach is the employment of gated indicator delivery systems using preorganized nanoscopic solid structures incorporated on paper strips to produce an exponential amplification of the detectable signal. Having in mind these concepts, several examples of (bio)gated materials incorporated into sensing membranes will be presented for the detection of small organic molecules, having fluorescence or electrochemiluminescence signal as output signal. Compared with fluorescence, it has been demonstrated that the non-optical excitation has significantly reduced the background signal, and with the help of a portable potentiostat in combination with a home-made 3D-printed case fitted onto a smartphone, the sensitivity of the sensing system has been improved tremendously, from the lower ppb range (fluorescence) to the lower ppt range. With this study, the applicability of ECL detection on paper strips in combination with gated indicator-releasing materials has been demonstrated for the first time, presenting a novel synergistic match. Considering the modularity of the system developed, the platform technology potential is obvious, promising expansion of the general concept to many other analytes, applications and scenarios.