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Positronium, a bound state of positron and electron has been proposed as a novel biomarker for examining cancer cells [1]. This atom is copiously created in cells during Positron Emission Tomography (PET) imaging [2-3].Our pre-clinical studies have shown significant differences in the lifetime of positronium between normal and neoplastic cells and tissues [4-5]. Due to the conversion process concentrations of free radicals, especially reactive oxygen species (ROS) have a significant influence on the properties of positronium, such as its lifetime and production intensity in the tissue [6-7]. We investigated the role of antioxidants, such as vitamin C and epigallocatechin gallate (EGCG), on the values of the newly proposed biomarker.
Studies were conducted on in vitro cell culture of normal human cell: melanocyte HEMa-LP cell line and two cell lines of melanoma: WM115 (primary melanoma) and WM266-4 (metastatic melanoma) as an example of cancer cells with different degree of malignancy. Cells were exposed to vitamin C in various concentrations (100, 1000 µM) and EGCG (10, 100 µM). Positronium lifetime was determined by means of Positron Annihilation Lifetime Spectroscopy and Na-22 isotope was used as a source of positrons.
Obtained results showed differences in positronium lifetime, between normal and cancer cell in relation to their malignancy. Resulting o-Ps lifetime in HEMa-LP, WM115, and WM266-4 cells was equal to 1.91(02)ns, 1.95(03)ns, 1.99(01)ns, respectively in control; 1.93(02)ns, 1.96(01)ns, 1.98(01)ns in 1000 µM concentration of vitamin C and 1.91(02)ns, 1.93(01)ns, 1.89(02)ns in 100µM concentration of EGCG. No significant differences were observed in measured solutions without the cells, resulting in o-Ps lifetime of 1.91(02)ns, 1.88(01)ns in vit. C and EGCG solution, respectively.
Outcome of our experiment confirmed the validity of employing positronium as an indicator, which may have a direct impact on better and more accurate diagnostics. The Jagiellonian Positron Emission Tomography scanner can be applied for simultaneous PET and positronium imaging [8-12].
References:
[1] Moskal, P. et al., Patent No: US 9851456; PL 227658; PCT/EP2014/068374.
[2] Moskal, P.et al., Nat. Rev. Phys. 1, 527–529 (2019).
[3] Moskal, P. 2019 IEEE Nucl. Scien. Sympo. and Medical Imaging Conference Proceedings, NSS/MIC 2019, doi:10.1109/NSS/MIC42101.2019.9059856 (2020).
[4] Moskal, P. et al., Developing a Novel Positronium Biomarker for Cardiac Myxoma Imaging, bioRxiv
[5] Kubicz, E. AIP Conf. Proc. 2182, 050004 (2019).
[6] Stepanov, P. S. et al., Phys. Chem. Chem. Phys. 22, 5123–5131 (2020).
[7] Shibuya, K. et al. Commun. Phys. 3, 173 (2020).
[8] Moskal, P. et al. Phys. Med. Biol. 61, 2025–2047 (2016).
[9] Gajos, A. et al. Adv. High Energy Phys. ID 8271280 (2018).
[10] Moskal, P. et al. Phys. Med. Biol. 64, 055017 (2019).
[11] Moskal, P. et al. EJNMMI Phys. 7, 44 (2020).
[12] Moskal, P. & Stępień, E. PET Clin. 15, 439–452 (2020).
