title: In-situ second harmonic generation by cancer cell targeting ZnO nanocrystals to effect photodynamic action in subcellular space.
abstract: This paper introduces the concept of in-situ upconversion of deep penetrating near infrared light via second harmonic generation from ZnO nanocrystals delivered into cells to effect photo activated therapies, such as photodynamic therapy, which usually require activation by visible light with limited penetration through biological tissues. We demonstrated this concept by subcellular activation of a photodynamic therapy drug, Chlorin e6, excited within its strong absorption Soret band by the second harmonic (SH) light, generated at 409 nm by ZnO nanocrystals, which were targeted to cancer cells and internalized through the folate-receptor mediated endocytosis. By a combination of theoretical modeling and experimental measurements, we show that SH light, generated in-situ by ZnO nanocrystals significantly contributes to activation of photosensitizer, leading to cell death through both apoptotic and necrotic pathways initiated in the cytoplasm. This targeted photodynamic action was studied using label-free Coherent Anti-Stokes Raman Scattering imaging of the treated cells to monitor changes in the distribution of native cellular proteins and lipids. We found that initiation of photodynamic therapy with upconverted light led to global reduction in the intracellular concentration of macromolecules, likely due to suppression of proteins and lipids synthesis, which could be considered as a real-time indicator of cellular damage from photodynamic treatment. In prospective applications this in-situ photon upconversion could be further extended using ZnO nanocrystals surface functionalized with a specific organelle targeting group, provided a powerful approach to identify and consequently maximize a cellular response to phototherapy, selectively initiated in a specific cellular organelle.
authors.affiliation: Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082, China; Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: Bobo
authors.initials: B
authors.lastname: Gu
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: Artem
authors.initials: A
authors.lastname: Pliss
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: Andrey N
authors.initials: AN
authors.lastname: Kuzmin
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Baev
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: Tymish Y
authors.initials: TY
authors.lastname: Ohulchanskyy
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA.
authors.forename: Jossana A
authors.initials: JA
authors.lastname: Damasco
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore.
authors.forename: Ken-Tye
authors.initials: KT
authors.lastname: Yong
authors.affiliation: Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha, 410082, China. Electronic address: scwen@hnu.cn.
authors.forename: Shuangchun
authors.initials: S
authors.lastname: Wen
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA. Electronic address: pnprasad@buffalo.edu.
authors.forename: Paras N
authors.initials: PN
authors.lastname: Prasad
mesh_terms: D002735:Chlorophyllides; D005492:Folic Acid / Q000737:chemistry / Q000493:pharmacokinetics*; D006367:HeLa Cells; D006801:Humans; D007259:Infrared Rays; D053769:Nanocapsules / Q000737:chemistry* / Q000528:radiation effects; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000378:metabolism*; D010778:Photochemotherapy / Q000379:methods*; D011166:Porphyrins / Q000008:administration & dosage*; D000073798:Second Harmonic Generation Microscopy; D016896:Treatment Outcome; D015034:Zinc Oxide / Q000528:radiation effects / Q000627:therapeutic use*
chemical_list: D002735:Chlorophyllides; D053769:Nanocapsules; D011166:Porphyrins; C062985:phytochlorin; D005492:Folic Acid; D015034:Zinc Oxide
keywords: CARS imaging; Nonlinear nanocrystals; Photodynamic therapy; Second harmonic generation