Comparison of a new nanoform of the photosensitizer chlorin e6, based on plant phospholipids, with its free form

Abstract

Photodynamic therapy is an advanced method of treating cancer and various benign diseases, including infections. It uses light‐activated molecules [photosensitizers (PSs)] to generate reactive oxygen species ( ROS ) when irradiated with light of a specific wavelength. This study examined the photophysical and photosensitizing activity of the PS chlorin e6 incorporated in a delivery system based on plant phospholipids. This new nanoform of chlorin e6 comprised particles with a diameter of 18.4 ± 2.5 nm and zeta potential of −34.6 ± 3.0 mV. Incorporation of chlorin e6 in phospholipid nanoparticles was observed to cause a bathochromic shift of Q‐band absorption maximum by 14 nm without an absorption change in the range of the Soret band. Fluorescence intensity of chlorin e6 embedded in the phospholipid nanoparticles increased 1.7‐fold. Chlorin e6 in phospholipid nanoparticles, when irradiated, was able to generate ROS as shown by oxidation of polyunsaturated fatty acids of the phospholipid matrix of the delivery system and reduced l ‐glutathione. In vivo it was demonstrated that the new nanoform of chlorin e6 provides more accumulation of PSs in tumor tissue than its free form. Moreover, its accumulation in the skin was lower and its elimination from the skin almost five times faster than when administered in free form. The observed differences of this new nanoform of chlorin e6 should lead to enhancement of antitumor efficacy and a decrease in phototoxicity.

Coupling Chlorin e6 to the surface of Nanoscale Gas Vesicles strongly enhances their intracellular delivery and photodynamic killing of cancer cells

“…Upon reaching the cytoplasm and following light activation, Ce6 molecules are excited to their singlet → triplet states where their energy can be transferred to O 2 to generate reactive singlet oxygen ( 1 O 2 ) 22 . Alternatively, activated Ce6 can react directly with proteins, nucleic acids and lipids to form reactive oxygen species (ROS; superoxide anion, hydroxyl radical, hydrogen peroxide) causing oxidative damage leading to cell death 22,23 . The absorption spectrum for Ce6 released from acid-hydrolyzed Ce6-GVs was similar to that obtained for free Ce6 including peak absorption at 400 nm and 640 nm.…”

Light-Activated Nanoscale Gas Vesicles Selectively Kill Tumor Cells

“…17 Alternatively, activated Ce6 can react directly with proteins, nucleic acids and lipids to form reactive oxygen species (ROS; superoxide anion, hydroxyl radical, hydrogen peroxide) causing oxidative damage leading to cell death. 17,18 The cellular uptake of Ce6-GVs, WT GVs and free Ce6 by human breast carcinoma MCF-7 and human hypopharyngeal squamous cell carcinoma FaDu cells was thus assessed by flow cytometry and confocal microscopy. For both techniques, fluorescence emission signals arising from the chlorin e6 chromophore (λ exc 403 nm) were captured between 660-680 nm (Fig.…”

Photosensitizer Chlorin e6 Internalization into Tumor Cells in Phospholipid Nanoparticles Conjugated with Peptide Containing the NGR Sequence

“…Полученную ультратонкую эмульсию пропускали через фильтр 220 нм ("Merck Millipore", США). "Контрольные" наночастицы без NGR готовили так же, используя только соевый фосфатидилхолин (Lipoid S100), как описано ранее [10]. Встраивание хлорина е6 в наночастицы, как было показано ультрафильтрацией, достигало более 95%, размер частиц составлял 20-40 нм.…”

“…Следует также подчеркнуть, что это первая работа, показавшая результативность использования аффинного к опухолям пептида Asn-Gly-Arg (NGR) для повышения адресной доставки в опухолевые клетки хлорина е6, включенного в лекарственную транспортную систему. Полученные на опухолевых клетках HepG2 результаты в сочетании с показанным нами ранее снижением фототоксичности этого фотосенсибилизатора при включении его в фосфолипидные наночастицы [10] могут служить убедительным доводом в пользу перспективности такого подхода для оптимизации фотодинамической терапии сóлидных опухолей.…”

“…Нами ранее было проведено включение хлорина е6 в ультрамалые фосфолипидные наночастицы диаметром до 30 нм из соевого фосфатидилхолина, приводящее к снижению фототоксичности этого ФС вследствие ускоренного выведения из органов [10], а также исследована возможность повышения его проникновения в клетки HepG2 при добавлении гептааргинина (R7). Целью настоящей работы было введение в такую систему пептида NGR в качестве адресного лиганда и исследование его влияния на проникновение хлорина е6 в опухолевые клеточные линии HepG2 и MCF-7.…”