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Low-Energy Electron Irradiation Damage in Few-Monolayer Pentacene Films.

ABSTRACT: Crystalline films of pentacene molecules, two to four monolayers in thickness, are grown via in situ sublimation on silicon substrates in the ultrahigh vacuum chamber of a low-energy electron microscope. It is observed that the diffraction pattern of the pentacene layers fades upon irradiation with low-energy electrons. The damage cross section is found to increase by more than an order of magnitude for electron energies from 0 to 10 eV and by another order of magnitude from 10 to 40 eV. Close to 0 eV, damage is virtually nil. Creation of chemically reactive atomic centers after electron attachment or impact ionization is thought to trigger chemical reactions between neighboring molecules that gradually transform the layer into a disordered carbon nanomembrane. Additionally, diminishing spectroscopic features related to the unoccupied band structure of the layers, accompanied by loss of definition in real-space images, and an increase in the background intensity of diffraction images during irradiation point to chemical changes and formation of a disordered layer.

SUBMITTER: Tebyani A

PROVIDER: S-EPMC8647077 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature

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Low-Energy Electron Irradiation Damage in Few-Monolayer Pentacene Films.

Tebyani A A Baalbergen F B FB Tromp R M RM van der Molen S J SJ

The journal of physical chemistry. C, Nanomaterials and interfaces 20211118 47

Crystalline films of pentacene molecules, two to four monolayers in thickness, are grown via in situ sublimation on silicon substrates in the ultrahigh vacuum chamber of a low-energy electron microscope. It is observed that the diffraction pattern of the pentacene layers fades upon irradiation with low-energy electrons. The damage cross section is found to increase by more than an order of magnitude for electron energies from 0 to 10 eV and by another order of magnitude from 10 to 40 eV. Close t ...[more]

PMID: 34887975

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Project description:NK-92 cells and their CAR-modified derivatives exhibit strong cytotoxic activity against tumors and are promising "off-the-shelf" therapeutics compared to CAR-T cells. In order to ensure safety and prevent the occurrence of secondary tumors, (CAR-)NK-92 cells need to be inactivated before transfusion. With increasing clinical use, there is a growing demand for enhanced safety and an efficient method that stops cell proliferation, but better maintains the cytotoxic effector functions of the cells compared to commonly used gamma irradiation. Recently, low-energy electron irradiation (LEEI) was successfully applied for inactivation of bacteria and viruses for vaccine production, and was described as a method for NK-92 inactivation for the first time. In the present publication, data on extensive characterization of LEEI and its comparison with gamma irradiation for the inactivation of parental NK-92 cells as well as CD123-directed CAR-NK-92 cells are provided. Our results show that both irradiation methods cause a progressive decrease in cell viability and are therefore suitable for inhibition of proliferation. Notably, cytotoxicity of the NK cells was significantly reduced by gamma irradiation, but not by LEEI three days after irradiation, compared to non-irradiated cells. Both gamma irradiation as well as LEEI led to substantial DNA-damage and an accumulation of irradiated cells in the G2/M phase. In addition, transcriptomic analysis of cells irradiated with both methods revealed approximately 12-fold more differentially expressed genes after gamma irradiation compared to LEEI. Analysis of surface molecules revealed an irradiation-induced decrease in CD56 expression but no changes in the levels of the activating receptors NKp46, NKG2D, and NKp30. Conclusions: The present data show that LEEI efficiently inactivates (CAR )NK-92 cells and sustains their cytotoxic capacity better than gamma irradiation. Taking into account additional logistic advantages of LEEI proves a potent alternative in the manufacturing of (CAR-)NK-92 cells for clinical application.

Project description:BackgroundWith increasing clinical use of NK-92 cells and their CAR-modified derivatives in cancer immunotherapy, there is a growing demand for efficient production processes of these "off-the-shelf" therapeutics. In order to ensure safety and prevent the occurrence of secondary tumors, (CAR-)NK-92 cell proliferation has to be inactivated before transfusion. This is commonly achieved by gamma irradiation. Recently, we showed proof of concept that low energy electron irradiation (LEEI) is a new method for NK-92 inactivation. LEEI has several advantages over gamma irradiation, including a faster reaction time, a more reproducible dose rate and much less requirements on radiation shielding. Here, LEEI was further evaluated as a promising alternative to gamma irradiation yielding cells with highly maintained cytotoxic effector function.MethodsEffectiveness and efficiency of LEEI and gamma irradiation were analyzed using NK-92 and CD123-directed CAR-NK-92 cells. LEE-irradiated cells were extensively characterized and compared to gamma-irradiated cells via flow cytometry, cytotoxicity assays, and comet assays, amongst others.ResultsOur results show that both irradiation methods caused a progressive decrease in cell viability and are, therefore, suitable for inhibition of cell proliferation. Notably, the NK-mediated specific lysis of tumor cells was maintained at stable levels for three days post-irradiation, with a trend towards higher activities after LEEI treatment as compared to gamma irradiation. Both gamma irradiation as well as LEEI led to substantial DNA damage and an accumulation of irradiated cells in the G2/M cell cycle phases. In addition, transcriptomic analysis of irradiated cells revealed approximately 12-fold more differentially expressed genes two hours after gamma irradiation, compared to LEEI. Analysis of surface molecules revealed an irradiation-induced decrease in surface expression of CD56, but no changes in the levels of the activating receptors NKp46, NKG2D, or NKp30.ConclusionsThe presented data show that LEEI inactivates (CAR-)NK-92 cells as efficiently as gamma irradiation, but with less impact on the overall gene expression. Due to logistic advantages, LEEI might provide a superior alternative for the manufacture of (CAR-)NK-92 cells for clinical application.

Dataset Information

Low-Energy Electron Irradiation Damage in Few-Monolayer Pentacene Films.

Publications

Low-Energy Electron Irradiation Damage in Few-Monolayer Pentacene Films.

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