Photochemical & Photobiological Sciences PAPER Cite this: Photochem. Photobiol. Sci., 2020, 19, 1088 Received 31st January 2020, Accepted 24th June 2020 DOI: 10.1039/d0pp00032a rsc.li/pps Curcumin encapsulated colloidal amphiphilic block co-polymeric nanocapsules: colloidal nanocapsules enhance photodynamic and anticancer activities of curcumin Linda Bechnak, a Christian Khalil, b Riham El Kurdi, a Rony S. Khnayzer * b and Digambara Patra * a Curcumin-based novel colloidal nanocapsules were prepared from amphiphilic poly(ethylene oxide)- block-poly(propylene oxide)-block-poly(ethylene oxide) (F108). These colloidal nanocapsules appeared as spherical particles with size ranging between 270 and 310 nm. Curcumin fluorescence spectra exhibi- ted an aggregation-induced 23 nm red-shift of the emission maximum in addition to the enhancement of the fluorescence quantum yield in these nanocapsules. The cytotoxicity of curcumin and colloidal nano- capsules was assessed using human derived immortalized cell lines (A549 and A375 cells) in the presence and absence of light irradiation. The nanocapsules exhibited a >30-fold decrease in IC 50 , suggesting enhanced anticancer activity associated with curcumin encapsulation. Higher toxicity was also reported in the presence of light irradiation (as shown by the IC 50 data), indicating their potential for future application in photodynamic therapy. Finally, A375 cells treated with curcumin and the nanocapsules showed a sig- nificant increase in single- and/or double-strand DNA breaks upon exposure to light, indicating promising biological effects. Introduction Cancer is a major “killer” in modern societies, with significant impacts on global health. According to the Centers for Disease Control and Prevention more than 14.1 million new cancer cases were identified in 2012 1 with an expected increase to 19.3 million by 2025. 2 Cancer is characterized by abnormal cell proliferation and growth often associated with gene mutations. 3 The conventional methods for cancer treatment consist mainly of surgery, chemotherapy and radiotherapy. These approaches have various serious side effects on cancer- ous and healthy tissues alike, in addition to low cure and high recurrence rates. Distant metastasis in cancer patients has been a challenging issue in clinical treatment due to its associ- ated high mortality rate. 4 During metastasis, various organs such as the brain, liver, bone, lungs, and others are invaded by cancerous cells. Chemotherapy, radiotherapy and surgical interventions risk the formation of metastatic lesions resulting from these conventional therapies. 5 The therapeutic potential of light has been reported since ancient times. However, in modern medicine phototherapy gained popularity after Niels Ryberg Finsen successfully used it in the treatment of lupus vulgaris. 6 Photodynamic therapy (PDT) has recently been widely applied for cancer control, especially malignant dis- eases. 7 In PDT, a molecule, known as a photosensitizer, is excited after absorption of light of a specific wavelength leading to a reaction with oxygen which leads to the formation of reactive oxygen species (ROS) such as radicals and singlet oxygen in the targeted tissues that leads to cell death. 8 Therefore, PDT is already being applied to treat certain types of diseases such as actinic keratoses, prostate cancer etc. over the last few years. Curcumin or 1,7-bis(4-hydroxy-3 methoxyphenyl)-1,6-hepta- diene-3,5-dione is a β-diketo structure which tautomerizes between an enol and keto structure under physiological con- ditions (Fig. 1). It is a major constituent of turmeric extract and has many therapeutic uses including anti-inflammatory, anti-oxidant, 9 and anti-cancer activities. 10 A prominent factor correlated with the advancement of all types of cancer is inflammation. 11 Curcumin has been demon- strated to have anti-inflammatory therapeutic effects. In addition, curcumin is a well-established anti-cancer agent due to its ability to suppress the growth of various tumor cell lines by targeting several pathways implicated in carcinogenesis. 12 a Department of Chemistry, American University of Beirut, Beirut, Lebanon. E-mail: dp03@aub.edu.lb; Fax: +961 1 365 217; Tel: +961 1 350 000, Ext: 3985 b Department of Natural Sciences, Lebanese American University, P.O. Box: 13-5053, Chouran, Beirut 1102-2801, Lebanon. E-mail: rony.khnayzer@lau.edu.lb; Fax: +961 1 867 098; Tel: +961 1 786 456, Ext: 1962 1088 | Photochem. Photobiol. Sci. , 2020, 19, 1088–1098 This journal is © The Royal Society of Chemistry and Owner Societies 2020