Detection of hexahydro-1,3-5-trinitro-1,3,5-triazine (RDX) with a microbial sensor

Advancing biological investigations using portable sensors for detection of sensitive samples

Portable biosensors are emerged as powerful diagnostic tools for analyzing intricately complex biological samples. These biosensors offer sensitive detection capabilities by utilizing biomolecules such as proteins, nucleic acids, microbes or microbial products, antibodies, and enzymes. Their speed, accuracy, stability, specificity, and low cost make them indispensable in forensic investigations and criminal cases. Notably, portable biosensors have been developed to rapidly detect toxins, poisons, body fluids, and explosives; they have proven invaluable in forensic examinations of suspected samples, generating efficient results that enable effective and fair trials. One of the key advantages of portable biosensors is their ability to provide sensitive and non-destructive detection of forensic samples without requiring extensive sample preparation, thereby reducing the possibility of false results. This comprehensive review provides an overview of the current advancements in portable biosensors for the detection of sensitive materials, highlighting their significance in advancing investigations and enhancing sensitive sample detection capabilities.

The novel sandwich composite structure: a new detection strategy for the ultra-sensitive detection of cyclotrimethylenetrinitramine (RDX)

This study presents a novel sandwich composite structure that was designed for the ultra-sensitive detection of cyclotrimethylenetrinitramine (RDX). Au nanorod arrays (Au NRAs) were prepared and bound to 10^-7M 6-MNA as adsorption sites for RDX, while Au nanorods (Au NRs) were modified using 10^-5M 6-MNA as SERS probes. During detection, RDX molecules connect the SERS probe to the surface of the Au NRAs, forming a novel type of Au NRAs-RDX-Au NRs 'sandwich' composite structure. The electromagnetic coupling effect between Au NRs and Au NRAs is enhanced due to the molecular level of the connection spacing, resulting in new 'hot spots'. Meanwhile, Au NRAs and Au NRs have an auto-enhancement effect on 6-MNA. In addition, the presence of charge transfer in the formed 6-MNA-RDX complex induced chemical enhancement. The limits of detection of RDX evaluated by Raman spectroscopy using 6-MNA were as low as 10^-12mg ml^-1(4.5 × 10^-15M) with good linear correlation between 10^-12and 10^-8mg ml^-1(correlation coefficientR² = 0.9985). This novel sandwich composite structure accurately detected RDX contamination in drinking water and on plant surfaces in an environment with detection limits as low as 10^-12mg ml^-1and 10^-8mg ml^-1.

A bacterial bioreporter for the detection of 1,3,5-trinitro-1,3,5-triazinane (RDX)

We report the design, construction, and testing of Escherichia coli-based bioluminescent bioreporters for the detection of 1,3,5-trinitro-1,3,5-triazinane (RDX), one of the most prevalent military-grade explosives in use today. These sensor strains are based on a fusion between the promoter of either the hmp (nitric oxide dioxygenase) or the hcp (a high-affinity nitric oxide reductase) E. coli gene, to the microbial bioluminescence luxCDABEG gene cassette. Signal intensity was enhanced in ∆hmp and ∆hcp mutants, and detection sensitivity was improved when the two gene promoters were cloned in tandem. The Photobacterium leiognathi luxCDABEG reporter genes were superior to those of Aliivibrio fischeri in terms of signal intensity, but in most cases inferior in terms of detection sensitivity, due to a higher background signal. Both sensor strains were also induced by additional nitro-organic explosives, as well as by nitrate salts. Sensitive detection of RDX in a solid matrix (either LB agar or sand) was also demonstrated, with the bioreporters encapsulated in 1.5-mm calcium alginate beads. Lowest RDX concentration detected in sand was 1.67 mg/kg sand. The bioreporter strains described herein may serve as a basis for a standoff detection technology of RDX-based explosive devices, including buried landmines.

Modeling a synthetic aptamer-based riboswitch biosensor sensitive to low hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) concentrations

RNA aptamers are relatively short nucleic acid sequences that bind targets with high affinity, and when combined with a riboswitch that initiates translation of a fluorescent reporter protein, can be used as a biosensor for chemical detection in various types of media. These processes span target binding at the molecular scale to fluorescence detection at the macroscale, which involves a number of intermediate rate-limiting physical (e.g., molecular conformation change) and biochemical changes (e.g., reaction velocity), which together complicate assay design. Here we describe a mathematical model developed to aid environmental detection of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using the DsRed fluorescent reporter protein, but is general enough to potentially predict fluorescence from a broad range of water-soluble chemicals given the values of just a few kinetic rate constants as input. If we expose a riboswitch test population of Escherichia coli bacteria to a chemical dissolved in media, then the model predicts an empirically distinct, power-law relationship between the exposure concentration and the elapsed time of exposure. This relationship can be used to deduce an exposure time that meets or exceeds the optical threshold of a fluorescence detection device and inform new biosensor designs.