Denoising Methods in Ultra-fast LIBS for Bioclinical Imaging
Cesar ALVAREZ LLAMAS1, Ruggeri Guerrini2, Lucie Sancey3, Vincent Motto-Ros1, Ludovic Duponchel2
1Institut Lumière Matière UMR 5306, Université Lyon 1. CNRS, Villeurbanne, France; 2Univ. Lille, CNRS, UMR 8516, LASIRE, Lille 59000, France; 3Université Grenoble Alpes, INSERM U1209, CNRS UMR 5309, IAB. Grenoble 38000, France
Laser-Induced Breakdown Spectroscopy (LIBS) is recognised as a powerful analytical tool that can provide multi-elemental information from a single laser pulse, requiring minimal sample preparation. LIBS is based on the spectroscopic analysis of a laser-induced plasma, whose spectral signature reveals the elemental composition of the sample. Furthermore, μLIBS imaging, i.e. LIBS analysis with a crater size of less than 20 µm, offers spatially resolved elemental analysis and has applications in diverse fields such as industry, geology, forensics, and biomedicine [1] .
Currently, most μLIBS imaging setups use lasers with a shooting rate of less than 100 Hz. However, the use of kHz lasers could represent a significant breakthrough for elemental imaging analysis [2]. Although the literature presents several examples of the use of kHz lasers in LIBS, mainly focusing on industrial or geological applications, this is not yet widespread. Despite their potential, implementing such lasers in μLIBS imaging would present various challenges, primarily relating to weak plasma emission and signal-to-noise ratio (SNR) degradation, particularly when applied to delicate biological samples.
As the complexity and size of spectral data increase the development of workflows for spectral processing to handle, analyze, and extract analytical information from these data becomes of capital importance. Using kHz lasers allows mapping of 10 million spectra in less than three hours. Therefore, the main limitation lies in processing these large data sets. In this context, we highlight the application of kHz-μLIBS-imaging for the analysis of samples of bioclinical interest, with a focus on a comparative evaluation of 5 different denoising methods. Furthermore, to our knowledge, this research applies principal component analysis (PCA) and Whittaker Smoothing to LIBS data for the first time, opening new ways to improve the accuracy of such analyses [3].
[1] Gardette V. et al, Anal. Chem., 95 (2023), 49-69
[2] Alvarez-Llamas C., et al, J. Anal. At. Spectrom, 39 (2024), pp. 1077-1086,
[3] Guerrini R. et al, Spectrochim Acta B, 227 (2025) pp 107167
Investigation of bacterial responses to antimicrobial surfaces through fluorescent tracking and statistical analysis
Margherita Izzi1,2,3, Gavino Bassu2,4, Adele Castellani4, Rosaria Anna Picca1,2,3, Emiliano Fratini2,4, Marco Laurati2,4, Nicola Cioffi1,2
1Chemistry Department, University of Bari Aldo Moro, Via Orabona, 4, 70126 Bari, Italy; 2Center for Colloid and Surface Science (CSGI), Via della Lastruccia 3, Sesto Fiorentino 50019, Italy; 3CNR-IFN Institute for Photonics and Nanotechnologies, Italy; 4Department of Chemistry “Ugo Schiff”, Via della Lastruccia 3, Sesto Fiorentino 50019, Italy
The uncontrolled spread of infectious diseases has accelerated the development of advanced materials and bioactive surfaces designed to limit microbial transmission. In the aftermath of the Covid-19 pandemic, significant efforts have been devoted to the creation of antimicrobial materials, with metal-based nanocomposites emerging as some of the most promising candidates for surface coatings. These coatings are now pivotal in sectors such as healthcare, food packaging, and furniture, where broad-spectrum pathogen control is essential.
While the antimicrobial potential of inorganic nanomaterials is well recognized, their exact mechanisms of action remain only partially understood, often involving multiple simultaneous pathways. Establishing a clear correlation between surface properties and bioactivity is therefore crucial for the development of safer, eco-friendly materials with tunable and controllable efficacy.
Our research focuses on achieving antimicrobial functionality through the controlled release of metallic ions from particles embedded in polymeric matrices. Despite the widespread use of such bioactive surfaces, understanding their precise mode of action remains a key challenge, particularly due to the coexistence of different antimicrobial mechanisms. A detailed analysis of surface characteristics and their relation to bioactivity is thus essential, not only for enhancing material safety and sustainability, but also for minimizing antimicrobial resistance through precise dose-response control.
To address this, we investigated the early-stage interaction between inorganic antimicrobial agents and Bacillus subtilis, concentrating on ZnO-based bioactive surfaces. Short-term bacterial motility on these surfaces was examined using laser scanning confocal microscopy (LSCM), coupled with a novel statistical method designed to distinguish between bacteriostatic and bactericidal effects. By employing single-cell tracking, we analysed the trajectories of hundreds to thousands of fluorescently labelled bacteria and calculated the corresponding mean squared displacements (MSD). Additionally, bacterial motility was correlated with the release profile of Zn²⁺ ions from different surfaces.
ZnO nanostructures (NSs) were synthesized via a scalable, aqueous-phase electrochemical method [1]. To modulate morphology, two stabilizing agents - Sodium Dodecyl Sulfate (SDS) and Poly-Diallyl-Dimethyl-Ammonium chloride (PDDA) - were employed. These inorganic antimicrobials were then incorporated into three different polymer matrices (polyethylene oxide, polylactic acid, and poly-vinyl-methyl-ketone) to develop nanocomposite coatings with tunable Zn²⁺ ion release profiles, enabling controlled bioactivity. Comprehensive surface characterization was carried out using UV-Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and both scanning and transmission electron microscopy (SEM/TEM).
To quantitatively assess dose-effect relationships, we monitored bacterial motility following surface contact via particle tracking of LSCM data [2]. MSD analysis revealed a clear transition in motility behaviour: from active run-and-tumble dynamics to constrained, sub-diffusive motion in response to increasing Zn²⁺ concentrations. This suppression of motility aligned with the progression from super-diffusive to sub-diffusive motion, confirming the bacteriostatic impact of ion release. Live/dead imaging further validated the link between Zn²⁺ exposure and bacterial viability.
To our knowledge, few studies have addressed the impact of metal-based antimicrobials on bacterial motility. This integrated analytical approach offers a powerful tool for distinguishing between bacteriostatic and bactericidal effects, supporting the rational design of antimicrobial coatings with spatiotemporally controlled activity.
References:
[1] M. Izzi, M.C. Sportelli, L. Torsi, R.A. Picca, N. Cioffi, Synthesis and Antimicrobial Applications of ZnO Nanostructures: A Review, ACS Appl. Nano Mater. 6 (2023) 10881–10902
[2] G. Bassu, M. Laurati, E. Fratini, Transition from active motion to anomalous diffusion for Bacillus subtilis confined in hydrogel matrices, Colloids and Surfaces B: Biointerfaces 236 (2024) 113797
Advancing Luminescence-Based Chemical Imaging: From Method Development to Real-World Applications (invited talk)
Andrey V. Kalinichev1,2, Martin R. Rasmussen1,3, Michael W. Hansen1, Klaus Koren1
1Aarhus University, Department of Biology — Microbiology, Ny Munkegade 116, 8000 Aarhus C, Denmark; 2Aarhus University, Aarhus Institute of Advanced Studies, Høegh-Guldbergs Gade 6B, 8000 Aarhus C, Denmark; 3Center for Landscape Research in Sustainable Agricultural Futures (Land-CRAFT), Aarhus University, Ole Worms Allé 3, 8000 Aarhus C, Denmark
Luminescent optodes have become essential tools for chemical imaging, allowing for spatially resolved measurements of key analytes such as oxygen and pH. In our laboratory, we have developed a range of advanced imaging strategies that enhance the capabilities of both planar and nanoparticle-based optode sensing, unlocking new applications in environmental and biological research.
This presentation will focus on two main aspects of our recent work. First, we focus on methodological innovations in imaging: from deconvolution-based hyperspectral unmixing for dual-analyte detection, to frame-straddling techniques for time-resolved lifetime imaging using conventional cameras. We also introduce sensPIV, a technique integrating chemical sensing with particle image velocimetry, and grid optodes that enable scalable, multiparameter imaging with pixel-level calibration and modular sensor integration.
Second, we demonstrate how these tools are applied in real-world systems. This includes high-resolution mapping of oxygen and pH dynamics in marine sediments, coral-associated microenvironments, and transparent soil analogs for 3D oxygen imaging. In terrestrial contexts, we present applications in soil systems using the multianalyte real-time in-situ imaging system (MARTINIS), demonstrating how luminescent sensing can support ecosystem monitoring and agricultural research.
A significant focus of our recent work has been on utilizing low-cost, commercially available imaging hardware, including RGB or monochrome cameras equipped with optical filters, to achieve high-performance sensing. We believe this approach lowers technical barriers and promotes the development of accessible tools for end-users in environmental sciences and applied biology. By designing optode-based systems that are modular and compatible with standard instrumentation, we aim to connect technical advancements with practical needs in ecological modeling, water quality monitoring, and soil management.
The presentation is supported by an AIAS-AUFF Fellowship (AK) from the Aarhus Institute of Advanced Studies and Aarhus Universitets Forskningsfond, the Pioneer Center for Research in Sustainable Agricultural Futures (Land-CRAFT), DNRF grant no. P2 (MRR), grants by the Novo Nordisk Foundation (no. 0079370), and by the Grundfos foundation (KK).
|
