Filtern
Dokumenttyp
- Posterpräsentation (5) (entfernen)
Referierte Publikation
- nein (5)
Schlagworte
- Hybrid materials (1)
- Pyrethroids (1)
- Signal amplification (1)
- mesoporous material (1)
- nerve agent (1)
- sensor (1)
Organisationseinheit der BAM
Mercury is a highly toxic, bioaccumulative heavy metal that can cause serious health problems even at low concentrations, thus presenting a major threat for the natural water resources. Its high toxicity entails low MCL values (e.g., 2 ppb),[1] requiring at best materials that cannot only selectively detect Hg2+ at trace levels but also effectively remove it. Various such dual functional materials have been developed in the past.[2] However, most of these approaches have limitations with respect to sensitivity and selectivity, show slow responses or require complex instrumentation.
Here we report the development of mesoporous silica materials containing boron-dipyrromethene (BODIPY) probes in their pore systems that allow for the sensitive and selective detection of Hg2+ in water via fluorescence enhancement while at the same time efficiently scavenging the toxic heavy metal. For this purpose, we adopted an earlier strategy[3] and prepared a refined BODIPY probe which was directly adsorbed on the surface of SBA-15-type silica having been functionalized with different organic moieties. Of all the materials tested, SBA-15 expressing propyl chains responded best, allowing for an excellent discrimination against Ag+ and other metals as well as a high sensitivity for Hg2+ with a limit of detection of 1.5 ppb.
The performance of the hybrids with regard to sensing and scavenging was validated by ICP-OES measurements before and after exposure of the materials to Hg2+-containing solutions, allowing retentions of 0.07 g Hg2+ g solid-1. Control studies revealed that while the fluorescent probe is responsible for the very sensitive indication at low Hg2+ concentrations, the majority of the toxic metal ion is scavenged at the walls of the silica material. Current work is directed at the incorporation of these sensor particles into filtration systems for monitoring purposes.
The organophosphate nerve agents Tabun (GA), Sarin (GB) and Soman (GD) are among the most toxic chemical warfare agents (CWA) known, and exert their biological effects by irreversibly inhibiting acetylcholinesterase enzymes of the human nerve system. The use of these agents in the past century has killed millions of civilians around the world during World Wars I and II, and after that, approximately 40.000 tons of chemical ammunition were dumped into the Baltic Sea, containing ca. 13.000 tons of chemical warfare agents. Since their production, almost all the nations of the world have been strictly avoiding the development and use of CWA, participating in active destruction of CWA stockpiles, especially since the Chemical Weapon Convention (CWC) of 1993. However, CWA have been used in offensive ways against civilian population by terrorists, as for instance in the fatal Tokyo subway terror incident of 1995 or, most recently, against antigovernment demonstrators in Syria in 2013. Due to their higher toxicity and continuous use, it is therefore very important to develop simple and fast detection methods relying on new nerve agent sensing modalities for use in control and inspection.
A practically useful fluorescent probe must possess a rapid response and high sensitivity, and shall be implementable into easy-to-use devices for real time detection by untrained personnel. Taking into account this fact, in this work we have synthesized several mesoporous silica materials containing boron–dipyrromethene (BODIPY) moieties for the detection of nerve agents GA, GB and GD in the gas phase. Development of our system indicated that the most potent materials are able to respond to the presence of nerve agent simulants diethyl cyanophosphonate, diethyl chlorophosphate and diisopropyl fluorophosphate, which have to be used in a laboratory setting, yet also for the real nerve agents Sarin, Soman and Tabun, producing a strong quenching of the fluorescence. Furthermore, a portable device for the detection of GA, GB and GD in the gas phase has been prepared for in situ sensing and rapid screening applications, consisting of strips that are able to indicate the targets down to below 1 mgm-3 which is below the LD50 values.
The urgent necessity to carry out reliable and relevant analytical measurements directly at a point-of-need is one of the current drivers for the development of miniaturised analytical systems, quick tests and wearables. Despite their simplicity, this type of tests must guarantee analytical relevance and reliability like laboratory-based analysis, e.g., in terms of sensitivity, selectivity, immunity against false positives and false negatives as well as robustness and repeatability. Keeping in mind the high sensitivity offered by gated indicator-releasing micro- and nanoparticles due to their inherent features of signal amplification, we performed several optimisations to develop a potential biosensor platform for use in rapid tests. Conceptually, these gated materials are closely related to drug delivery systems, consisting of high porous materials usually closed with macromolecular “caps” and loaded with indicator molecules that are released in presence of a target analyte. However, the key difference between the two types of functional materials is that many drug delivery systems should deliver their cargo over a longer period, often many hours, whereas the gated materials prepared for sensing should show fast release kinetics, on the order of <5 min.
With the aim to optimise and adapt gated materials for sensing purposes, we prepared in this work several antibody-gated materials for small-molecule sensing. The materials consisted of porous silica particles containing indicator molecules in the pores and certain hapten molecules grafted to the particle surface close to the pore openings. The pores were then capped with antibodies binding to these haptens, thus inhibiting the escape of the indicators from inside of the pores. In presence of the corresponding analyte, the antibody is displaced from the surface of the material, allowing the escape of the indicators. This allows the detection of the analyte indirectly through an inherent signal amplification. In this work, the insecticide permethrin, a type-I pyrethroid, was selected as target model, because type-I pyrethroids play an important role in airplane disinfection. A first in-depth study of the various chemical tuning options of such antibody gated systems was performed. Different mesoporous silica supports, different functionalisation routes and different loading sequences were assessed. The materials’ performances were evaluated by studying their temporal response behaviour and detection sensitivity, including the tightness of pore closure (through the amount of blank release in absence of analyte) and the release kinetics. Our results indicate that the better the paratope-accommodating Fab region of the antibody “cap” fits into the host material’s pore openings, the better the closing/opening mechanism can be controlled. Because such materials can be used in various different formats from suspension assays[1] via microfluidic chips[2] to test strip-based lateral flow assays,[3] such materials present a powerful analytical particle platform for the sensitive analytics and diagnostics outside of a laboratory, realising sensitivities down to the µg kg–1 range in less analysis times of less than 5 min as we have recently demonstrated.[4]