Magnetic Carbon Nanoparticles Derived from Candle soot for SALDI MS Analyses of Drugs and Heavy Metals in Latent Fingermarks

Matrix- and surface-assisted laser desorption/ionization-mass spectrometry analysis of fingermark components for forensic studies: current trends and future prospects

The chemical analysis of fingermarks (FMs) has attracted considerable attention in the realm of forensic investigations. Techniques based on direct ionization of a sample by laser irradiation, specifically matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS), have provided excellent figures of merit for analyzing high molecular-weight compounds. However, it can be challenging to analyze low molecular-weight compounds using MALDI-MS owing to potential interference produced by the organic matrices in the low molecular-weight region, which can impede the detection of small molecules (m/z < 700 Da). Alternately, surface-assisted laser desorption/ionization-mass spectrometry (SALDI-MS) has shown great promise for small molecules analysis owing to the unique properties of the nanostructures used, particularly, minimal chemical background in low m/z region improved the production of ions involved in this method. The advancement of MALDI-MS and SALDI-MS has propelled their application in the analysis of FM components, focused on gaining deep insights into individual traits. This review aims to outline the current role of MALDI-MS and SALDI-MS in the chemical analysis of FMs. It also describes the latest achievements in forensic intelligence derived from fingermark analysis using these powerful methods. The accomplishments include the understanding of certain characteristics and lifestyles of donors. The review offers a comprehensive overview of the challenges and demands in this field. It suggests potential enhancements in this rapidly expanding domain to bridge the gap between research and practical police casework.

Temporally and spatially resolved molecular profiling in fingerprint analysis using indium vanadate nanosheets-assisted laser desorption ionization mass spectrometry

This study presents the first-ever synthesis of samarium-doped indium vanadate nanosheets (IVONSs:Sm) via microemulsion-mediated solvothermal method. The nanosheets were subsequently utilized as a nano-matrix in laser desorption/ionization mass spectrometry (LDI-MS). It was discovered that the as-synthesized IVONSs:Sm possessed the following advantages: improved mass spectrometry signal, minimal matrix-related background, and exceptional stability in negative-ion mode. These qualities overcame the limitations of conventional matrices and enabled the sensitive detection of small biomolecules such as fatty acids. The negative-ion LDI mechanism of IVONSs:Sm was examined through the implementation of density functional theory simulation. Using IVONSs:Sm-assisted LDI-MS, fingerprint recognitions based on morphology and chemical profiles of endogenous/exogenous compounds were also achieved. Notably, crucial characteristics such as the age of an individual's fingerprints and their physical state could be assessed through the longitudinal monitoring of particular biomolecules (e.g., ascorbic acid, fatty acid) or the specific biomarker bilirubin glucuronide. Critical information pertinent to the identification of an individual would thus be facilitated by the analysis of the compounds underlying the fingerprint patterns.

Continuous synthesis of BaFe2O4 and BaFe12O19 nanoparticles in a droplet microreactor for efficient detection of antihistamine drugs in oral fluid using surface-assisted laser desorption/ionization mass spectrometry

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has received considerable attention as a complementary approach to matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), offering substantial potential for analyzing molecules in the low-mass region. Herein, we propose a facile method, a microreactor for the synthesis of two types of barium ferrite (BaFe2O4 and BaFe12O19) nanoparticles (NPs) within moving droplets for detecting antihistamine (AH) drugs in oral fluid (OF). The synthesized BaFe2O4 and BaFe12O19 NPs exhibited small particle size, good ultraviolet absorption, and excellent performance in SALDI-MS, as determined by survival yield measurements. The limits-of-detection for AH drugs were in the range of 1 pg mL-1 to 100 ng mL-1, and spot-spot reproducibility of the SALDI substrates was satisfactory. Moreover, when analyzing cetirizine in OF, the obtained recoveries of cetirizine were 101% and 99% using BaFe2O4 and BaFe12O19 NP, respectively. Furthermore, the proposed method was validated by analyzing OF samples from a healthy volunteer who consumed a 5 mg levocetirizine tablet for seven days. SALDI-MS analysis confirmed the successful detection of endogenous components, the parent ion of cetirizine, and other exogenous substances. This study reports an advanced application of droplet microreactor technology for designing and synthesizing a wide range of novel and efficient SALDI-MS substrates for various applications.

Predicting Fingerprint Age Based on Ozonolysis Kinetics of Unsaturated Triacylglycerol Degradation

Answering the question, "How old is a fingerprint?", is a highly sought-after aim in forensic science. Despite several decades of studies to find an empirical correlation in fingerprint aging, there has been no reliable method so far. In this study, we attempt to determine the time since deposition (TSD) of aged fingerprints from the chemical profile captured within a matrix-assisted laser desorption/ionization mass spectrometry data set. Our approach is based on the chemical kinetics associated with the ambient ozonolysis of unsaturated triacylglycerols (TGs), a major component in fingerprint lipids. First, ozone concentration and ambient temperature were determined to be the major factors in the degradation of unsaturated TGs. A simple kinetics model is then developed to describe the decay of unsaturated TGs, dictated only by the temperature and ozone concentration. This model is then applied to the degradation of TGs in a mixture of TG standards and multiple individuals' fingerprints. The overall decay of unsaturated TGs follows the pseudo-first-order reaction kinetics, validating our hypothesis; however, there are significant person-to-person variations in the initial abundance of unsaturated TGs and the decay rate, hampering the accurate prediction of TSD unless they are corrected for each individual. Nevertheless, the model's applicability for ambient fingerprint aging data was successfully demonstrated.

Magnetic Nanoparticle-Based Surface-Assisted Laser Desorption/Ionization Mass Spectrometry for Cosmetics Detection in Contaminated Fingermarks: Magnetic Recovery and Surface Roughness

In this work, we propose a matrix-free approach for the analysis of fingermarks (FMs) contaminated with five cosmetic products containing different active pharmaceutical ingredients (APIs) using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). For this purpose, a magnetic SALDI substrate based on Fe₃O₄-CeO₂ magnetic nanoparticles was prepared, characterized, and optimized for the analysis of contaminated FMs without sample pretreatment. Initially, groomed FM and cosmetic products were separately analyzed, and their major components were successfully detected. Subsequently, FMs contaminated with Ordinary serum and Skinoren, Dermovate, Bepanthen, and Eucerin creams were analyzed, and components of FM and cosmetics were detected. The stability of the cosmetics in FMs was studied over an interval of 28 days, and all components showed good stability in FM for 4 weeks. Recovery of contaminated FMs from different surfaces utilizing a few microliters of the magnetic substrate was carried out using a simple external magnetic field from ceramic, plastic, metal, and glass. Successful retrieval of the API and FM components was achieved with magnetic recovery, and glass exhibited the best recovery, whereas ceramic tile demonstrated the lowest recovery. This was supported by atomic force microscopy study, which revealed that the ceramic surface had higher roughness than the other surfaces employed in this study, which adversely affected the magnetic maneuvering. This proof-of-concept investigation extends the application of SALDI-MS in forensic analysis of contaminated FMs by exploring cosmetics as exogenous materials and their stability and recovery from different surfaces.