Monitoring Early Infection Dynamics in Live Spodoptera frugiperda (Sf) 9 Cells via Optical Photothermal Infrared (OPTIR) Spectroscopy.
4 affiliations
- 1Leibniz Institute of Photonic Technology, Member of Leibniz Health Technologies, Member of the Leibniz Centre for Photonics in Infection Research (LPI) , Albert-Einstein-Straße 9, 07745Jena, Germany.
- 2Department of Medical Engineering and Biotechnology, Ernst-Abbe-Hochschule, University of Applied Sciences, Carl-Zeiss-Promenade 2, 07745Jena, Germany.
- 3Abbe Center of Photonics (ACP), Friedrich Schiller University Jena, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Albert-Einstein-Straße 6, 07745Jena, Germany.
- 4Institute of Physical Chemistry (IPC), Friedrich Schiller University Jena, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Helmholtzweg 4, 07743Jena, Germany.
Abstract
Optical photothermal infrared (OPTIR) spectroscopy and imaging were combined with fluorescence microscopy to track infection progression. Baculovirus infection in Spodoptera frugiperda (Sf) 9 cells with mCherry as a fluorescence imaging reporter was analyzed 3, 6, 12, and 24 h postinfection (hpi). Cells were sandwiched between two CaF2 windows separated by a thin spacer, forming a sealed aqueous chamber that maintained hydration for 4-6 h, enabling IR spectral acquisition and imaging of living cells throughout. Fluorescence microscopy demonstrated a distinct onset of the mCherry reporter signal beginning 12 hpi. Early infection time points 3 and 6 hpi showed increased protein (amide II, 1545 cm-1) and asymmetric phosphate (1241 cm-1) bands, while 12 hpi, the symmetric phosphate (1087 cm-1) band profoundly reversed, consistent with nucleic acid changes associated with infection progression. The amide II to nucleic acid ratio (S1545/1086), obtained from discrete wavenumber imaging, tracked aggregate infection-associated protein changes (of which mCherry is a late-stage contributor), initially increasing 6 hpi, decreasing 12 hpi, and reaching its maximum value 24 hpi. The fluorescence reporter was absent at early stage infection (3 and 6 hpi), where IR spectroscopy and imaging successfully discriminated infected from uninfected cell populations. Fluorescence imaging validated IR measurements for later infection time points (12 and 24 hpi). Infected cells were classified from negative controls with balanced accuracies up to 90%. Overall, this approach identifies spectral signatures consistent with viral infection, providing a label-free method to discriminate infected populations from controls within their natural cellular environment.
Related
- Host-dependent salivary effector candidates and predicted plant immune targets in Spodoptera frugiperda
- Expression Profiles of Chitin Deacetylase Genes and Functional Characterization of Key Genes in Spodoptera frugiperda.
- Label-free identification and classification of leukocyte subpopulations in peripheral blood smears by optical photothermal infrared spectroscopy
- Evaluation of filter substrates for concurrent optical photothermal infrared and Raman spectroscopy in microplastic analysis
- Machine-learning-enhanced Optical Photothermal infrared (O-PTIR) spectroscopy for rapid simultaneous identification of multiple metabolites to monitor biotransformations: proof of concept on Brewer's spent grain (BSG)
BibTeX
@article{raghunathan2026monitoring,
title = {{Monitoring Early Infection Dynamics in Live Spodoptera frugiperda (Sf) 9 Cells via Optical Photothermal Infrared (OPTIR) Spectroscopy.}},
author = {Shravan Raghunathan and Kristina Worch and Christoph Krafft and Volker Deckert and Antje Burse and Juergen Popp and Tanveer Ahmed Shaik},
journal = {Analytical chemistry},
year = {2026},
month = sep,
doi = {10.1021/acs.analchem.6c03567},
url = {https://europepmc.org/article/MED/42915235},
note = {CC BY},
}
RIS
TY - JOUR
TI - Monitoring Early Infection Dynamics in Live Spodoptera frugiperda (Sf) 9 Cells via Optical Photothermal Infrared (OPTIR) Spectroscopy.
AU - Shravan Raghunathan
AU - Kristina Worch
AU - Christoph Krafft
AU - Volker Deckert
AU - Antje Burse
AU - Juergen Popp
AU - Tanveer Ahmed Shaik
PY - 2026
DA - 2026/09/01
JO - Analytical chemistry
DO - 10.1021/acs.analchem.6c03567
UR - https://europepmc.org/article/MED/42915235
AB - Optical photothermal infrared (OPTIR) spectroscopy and imaging were combined with fluorescence microscopy to track infection progression. Baculovirus infection in Spodoptera frugiperda (Sf) 9 cells with mCherry as a fluorescence imaging reporter was analyzed 3, 6, 12, and 24 h postinfection (hpi). Cells were sandwiched between two CaF2 windows separated by a thin spacer, forming a sealed aqueous chamber that maintained hydration for 4-6 h, enabling IR spectral acquisition and imaging of living cells throughout. Fluorescence microscopy demonstrated a distinct onset of the mCherry reporter signal beginning 12 hpi. Early infection time points 3 and 6 hpi showed increased protein (amide II, 1545 cm-1) and asymmetric phosphate (1241 cm-1) bands, while 12 hpi, the symmetric phosphate (1087 cm-1) band profoundly reversed, consistent with nucleic acid changes associated with infection progression. The amide II to nucleic acid ratio (S1545/1086), obtained from discrete wavenumber imaging, tracked aggregate infection-associated protein changes (of which mCherry is a late-stage contributor), initially increasing 6 hpi, decreasing 12 hpi, and reaching its maximum value 24 hpi. The fluorescence reporter was absent at early stage infection (3 and 6 hpi), where IR spectroscopy and imaging successfully discriminated infected from uninfected cell populations. Fluorescence imaging validated IR measurements for later infection time points (12 and 24 hpi). Infected cells were classified from negative controls with balanced accuracies up to 90%. Overall, this approach identifies spectral signatures consistent with viral infection, providing a label-free method to discriminate infected populations from controls within their natural cellular environment.
SN - 0003-2700
SN - 1520-6882
ER -