Dual-Color Emissive Upconversion Nanocapsules for Differential Cancer Bioimaging In Vivo
Oh Seok Kwon,†,‡,∇ Hyun Seok Song,§,∥,∇ Joaõ Conde,§,⊥ Hyoung-il Kim,† Natalie Artzi,*,§,# and Jae-Hong Kim*,† †
Department of Chemical and Environmental Engineering, School of Engineering and Applied Science, Yale University, New Haven, Connecticut 06511, United States ‡ BioNanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Yuseong, Daejeon 305-600, Republic of Korea § Harvard−MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States ∥ Division of Bioconvergence Analysis, Korea Basic Science Institute (KBSI), Yuseong, Daejeon 169-148, Republic of Korea ⊥ School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, U.K. # Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, United States S Supporting Information *
ABSTRACT: Early diagnosis of tumor malignancy is crucial for timely cancer treatment aimed at imparting desired clinical outcomes. The traditional fluorescencebased imaging is unfortunately faced with challenges such as low tissue penetration and background autofluorescence. Upconversion (UC)-based bioimaging can overcome these limitations as their excitation occurs at lower frequencies and the emission at higher frequencies. In this study, multifunctional silica-based nanocapsules were synthesized to encapsulate two distinct triplet−triplet annihilation UC chromophore pairs. Each nanocapsule emits different colors, blue or green, following a red light excitation. These nanocapsules were further conjugated with either antibodies or peptides to selectively target breast or colon cancer cells, respectively. Both in vitro and in vivo experimental results herein demonstrate cancer-specific and differential-color imaging from single wavelength excitation as well as far greater accumulation at targeted tumor sites than that due to the enhanced permeability and retention effect. This approach can be used to host a variety of chromophore pairs for various tumor-specific, color-coding scenarios and can be employed for diagnosis of a wide range of cancer types within the heterogeneous tumor microenvironment. KEYWORDS: upconversion, triplet−triplet annihilation, dual-color, nanocapsule, cancer, imaging, diagnosis
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improve the accumulation at the tumor site and provide selectivity toward specific cancer cell populations. Most of the conventional imaging approaches rely on fluorescence that exhibits ineffective tissue penetration at the excitation range of ultraviolet or low wavelength visible light.1,10−13 This inevitably dictates the use of high power irradiation, which further results in optical noise from background autofluorescence and potential cell damage. With the goal of achieving photoluminescence imaging using a light source with wavelength that lies within the phototherapeutic
anomedicine has gained growing interest in diagnosing and treating cancers. Various organic and inorganic photoluminescence nanoparticles made of dye-doped or loaded polymers, quantum dots, magnetic nanoparticles, and upconverting nanophosphors have been developed in the past decades for in vivo detection and imaging.1 More recently, core−shell structured nanoparticles have been explored for simultaneous tumor targeting, imaging, and in situ treatment.2−4 The core hosts not only imaging agents but also therapeutic drugs that can be released at the target site for treatment, while the nanometric particles enable enhanced permeability and retention (EPR), leading to effective accumulation at the tumor site.1,5−9 However, imparting targeting capabilities to the nanocarriers may © 2016 American Chemical Society
Received: November 9, 2015 Accepted: January 4, 2016 Published: January 4, 2016 1512
DOI: 10.1021/acsnano.5b07075 ACS Nano 2016, 10, 1512−1521
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Scheme 1. TTA-UC Process Leading to the Delayed Fluorescence from Acceptors, Perylene (Blue) and BPEA (Green)a
a
For emission of a single higher-energy photon from one 1ACC*, two TTET processes are required to form two 3ACC*, which then undergo TTA.
Figure 1. A procedure to fabricate bioprobe-attached SNC-B and SNC-G (A−E) and the schematic illustration of the cancer-specific, dual color imaging of (F) breast and (G) colorectal-cancer cells.
window of 600−1000 nm, photon frequency upconversion (UC) has been pursued as an alternative strategy.14 The UC is an anti-Stokes process through which two or more photons of low frequency are converted into a single photon with higher frequency.15 Lanthanide ion-doped inorganic crystals have been benchmark materials for decades,
wherein UC occurs through sequential absorption of two photons by long-lived excited-state lanthanide activators or by sensitized energy transfer between excited states. Bioimaging application based on trivalent lanthanide-doped inorganic nanoparticles has been attempted mostly with infrared excitation, but it suffers from requirement for extremely high 1513
DOI: 10.1021/acsnano.5b07075 ACS Nano 2016, 10, 1512−1521
Article
ACS Nano
Figure 2. SEM and TEM images (insets) of SNCs (A) before and (B) after the introduction of the bioprobes on their surfaces. The inset in (A) shows the size distribution of the SNCs. (C) Fluorescence image of SNC-B coated with anti-MUC1 antibody. For the visualization, Alexa Fluor 488-conjugated antibody that specifically binds to anti-MUC1 antibody was treated. (D) Fluorescence image of SNC-G coated with fluorescein isothiocyanate (FITC)-conjugated TCP1 peptide.
power excitation (101−104 W cm−2) and inherently poor quantum yield owing to low absorption and emission cross sections.16 Such limitations sparked the recent surge in search for an alternative UC strategy, particularly an organic chromophore-based system that achieves efficient triplet− triplet annihilation (TTA)-based UC under low power density excitation (
