title: Imaging Upconverting Polymersomes in Cancer Cells: Biocompatible Antioxidants Brighten Triplet-Triplet Annihilation Upconversion.
abstract: Light upconversion is a very powerful tool in bioimaging as it can eliminate autofluorescence, increase imaging contrast, reduce irradiation damage, and increase excitation penetration depth in vivo. In particular, triplet-triplet annihilation upconverting (TTA-UC) nanoparticles and liposomes offer high upconversion efficiency at low excitation power. However, TTA-UC is quenched in air by oxygen, which also leads to the formation of toxic singlet oxygen. In this work, polyisobutylene-monomethyl polyethylene glycol block copolymers are synthesized and used for preparing polymersomes that upconvert red light into blue light in absence of oxygen. In addition, it is demonstrated that biocompatible antioxidants such as l-ascorbate, glutathionate, l-histidine, sulfite, trolox, or even opti-MEM medium, can be used to protect the TTA-UC process in these polymersomes resulting in red-to-blue upconversion under aerobic conditions. Most importantly, this approach is also functional in living cells. When A549 lung carcinoma cells are treated with TTA-UC polymersomes in the presence of 5 × 10-3m ascorbate and glutathionate, upconversion in the living cells is one order of magnitude brighter than that observed without antioxidants. These results propose a simple chemical solution to the issue of oxygen sensitivity of TTA-UC, which is of paramount importance for the technological advancement of this technique in biology.
authors: Leiden Institute of Chemistry, Leiden University, PO box 9502, 2300 RA, Leiden, The Netherlands.
authors: Sven H C
authors: SH
authors: Askes
authors: Leiden Institute of Physics, Leiden University, PO box 9504, 2300 RA, Leiden, The Netherlands.
authors: Wim
authors: W
authors: Pomp
authors: Leiden Institute of Chemistry, Leiden University, PO box 9502, 2300 RA, Leiden, The Netherlands.
authors: Samantha L
authors: SL
authors: Hopkins
authors: Leiden Institute of Chemistry, Leiden University, PO box 9502, 2300 RA, Leiden, The Netherlands.
authors: Alexander
authors: A
authors: Kros
authors: Max Planck Institute for Polymer Research, 55128, Mainz, Germany.
authors: Si
authors: S
authors: Wu
authors: Leiden Institute of Physics, Leiden University, PO box 9504, 2300 RA, Leiden, The Netherlands.
authors: Thomas
authors: T
authors: Schmidt
authors: Leiden Institute of Chemistry, Leiden University, PO box 9502, 2300 RA, Leiden, The Netherlands. bonnet@chem.leidenuniv.nl.
authors: Sylvestre
authors: S
authors: Bonnet
mesh_terms: D000072283:A549 Cells; D000975:Antioxidants / Q000494:pharmacology*; D001672:Biocompatible Materials / Q000494:pharmacology*; D045744:Cell Line, Tumor; D016166:Free Radical Scavengers / Q000737:chemistry; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D009369:Neoplasms / Q000473:pathology*; D010100:Oxygen / Q000737:chemistry; D010316:Particle Size; D017319:Photosensitizing Agents / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D012995:Solubility; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D014867:Water / Q000737:chemistry
chemical_list: D000975:Antioxidants; D001672:Biocompatible Materials; D016166:Free Radical Scavengers; D017319:Photosensitizing Agents; D011108:Polymers; D014867:Water; D010100:Oxygen
keywords: bioimaging; oxygen; quenching; upconversion; vesicles