title: Field detection capability of immunochemical assays during criminal investigations involving the use of TNT.
abstract: The capability to collect timely information about the substances employed on-site at a crime scene is of fundamental importance during scientific investigations in crimes involving the use of explosives. TNT (2,4,6-trinitrotoluene) is one of the most employed explosives in the 20th century. Despite the growing use of improvised explosives, criminal use and access to TNT is not expected to decrease. Immunoassays are simple and selective analytical tests able to detect molecules and their immunoreactions can occur in portable formats for use on-site. This work demonstrates the application of three immunochemical assays capable of detecting TNT to typical forensic samples from experimental tests: an indirect competitive ELISA with chemiluminescent detection (CL-ELISA), a colorimetric lateral flow immunoassay (LFIA) based on colloidal gold nanoparticles label, and a chemiluminescent-LFIA (CL-LFIA). Under optimised working conditions, the LOD of the colorimetric LFIA and CL-LFIA were 1 μg mL(-1) and 0.05 μg mL(-1), respectively. The total analysis time for LFIAs was 15 min. ELISA proved to be a very effective laboratory approach, showing very good sensitivity (LOD of 0.4 ng mL(-1)) and good reproducibility (CV value about 7%). Samples tested included various materials involved in controlled explosions of improvised explosive devices (IEDs), as well as hand swabs collected after TNT handling tests. In the first group of tests, targets covered with six different materials (metal, plastic, cardboard, carpet fabric, wood and adhesive tape) were fixed on top of wooden poles (180 cm high). Samples of soil from the explosion area and different materials covering the targets were collected after each explosion and analysed. In the second group of tests, hand swabs were collected with and without hand washing after volunteers simulated the manipulation of small charges of TNT. The small amount of solution required for each assay allows for several analyses. Results of immunoassays confirmed that they were suitable to detect post-blast residues in soil and target materials and post transfer residues on hands, allowing further confirmation by more selective techniques. ELISA and LFIAs results obtained from the same solution were consistently in good agreement, and were confirmed by gas chromatography coupled to mass spectrometry (GC-MS). The reported immunoassays data demonstrates the suitability of LFIAs as on-site rapid and effective assays to detect TNT traces. The CL-ELISA proved useful in obtaining very sensitive detection in forensic investigations and testing, while CL-LFIA had performances in between LFIA and CL-ELISA.
authors.affiliation: Legal Medicine Section-SAIMLAL Department, SAPIENZA University of Rome, Viale Regina Elena, 336, 00161 Roma, Italy; Institut de Police Scientifique, Université de Lausanne, Batiment Batochimie, CH-1015 Lausanne, Switzerland. Electronic address: francescosaverio.romolo@uniroma1.it.
authors.forename: Francesco Saverio
authors.initials: FS
authors.lastname: Romolo
authors.affiliation: Department of Pharmacy and Biotechnology, University of Bologna, Via San Donato 15, 40127 Bologna, Italy.
authors.forename: Elida
authors.initials: E
authors.lastname: Ferri
authors.affiliation: Department of Chemistry, University of Bologna, Via Selmi, 2, 40126 Bologna, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Mirasoli
authors.affiliation: Emilia Romagna Regional Bureau of Scientific Police, Via Volto Santo 3, 40123 Bologna, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: D'Elia
authors.affiliation: Scientific Investigation Unit, Carabinieri Roma, Viale Tor di Quinto, 151, 00191 Roma, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Ripani
authors.affiliation: Scientific Investigation Unit, Carabinieri Roma, Viale Tor di Quinto, 151, 00191 Roma, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Peluso
authors.affiliation: Department of Chemistry, SAPIENZA University of Rome, Piazzale Aldo Moro 5, 00185 Roma, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Risoluti
authors.affiliation: Department of Pharmacy and Biotechnology, University of Bologna, Via San Donato 15, 40127 Bologna, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Maiolini
authors.affiliation: Department of Pharmacy and Biotechnology, University of Bologna, Via San Donato 15, 40127 Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Girotti
mesh_terms: D003124:Colorimetry; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005107:Explosions; D053834:Explosive Agents / Q000032:analysis*; D044707:Forensic Sciences / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry; D006225:Hand; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements / Q000379:methods*; D015203:Reproducibility of Results; D012867:Skin / Q000737:chemistry; D012987:Soil / Q000737:chemistry; D014303:Trinitrotoluene / Q000032:analysis*
chemical_list: D053834:Explosive Agents; D012987:Soil; D014303:Trinitrotoluene
keywords: 2,4,6-Trinitrotoluene (TNT); Chemiluminescence; ELISA; Explosives; LFIA; On-site tests