N‑Doped Carbon Quantum Dot (NCQD)-Deposited Carbon Capsules for Synergistic Fluorescence Imaging and Photothermal Therapy of Oral Cancer Rahul. K. Das, † Snigdharani Panda, † Chandra Sekhar Bhol, ‡ Sujit. K. Bhutia, ‡ and Sasmita Mohapatra* ,† † Department of Chemistry and ‡ Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India * S Supporting Information ABSTRACT: Use of nanomaterials blessed with both therapeutic and diagnostic properties is a proficient strategy in the treatment of cancer in its early stage. In this context, our paper reports the synthesis of uniform size N-rich mesoporous carbon nanospheres of size 65-70 nm from pyrrole and aniline precursors using Triton-X as a structure-directing agent. Transmission electron microscopy reveals that these carbons spheres contain void spaces in which ultrasmall nitrogen-doped quantum dots (NCQD) are captured within the matrix. These mesoporous hollow NCQD captured carbon spheres (NCQD-HCS) show fluorescence quantum yield up to 14.6% under λ ex = 340 nm. Interestingly, samples calcined at >800 °C clearly absorb in the wavelength range 700-1000 nm and shows light-to-heat conversion efficiency up to 52%. In vitro experiments in human oral cancer cells (FaDu) show that NCQD-HCS are internalized by the cells and induce a substantial thermal ablation effect in FaDu cells when exposed under a 980 nm near-infrared laser. ■ INTRODUCTION Cancer has been a leading cause of mortality in last few decades. 1,2 In spite of considerable efforts in treating cancer metastasis through primary clinical therapies such as surgery, radiotherapy, and chemotherapy, there remains chance of cancer recurrence caused by the residual survived cancer cells. 3-5 Such residual cells rapidly spread and become recurrent cancer after some days of initial treatment. 6 Hence, there is urgency to develop innovative cancer therapy methods to completely destroy cancer cells and prevent their reappearance in the future. Photothermal therapy (PTT) is a promising cancer therapy method which involves supply of high heat energy to cancer tissue with little detrimental effect on the normal tissue. 7-9 PTT may be adopted as an effective alternative or supplement to conventional cancer therapies. 10 Numerous reports have shown stimulating therapeutic effects of PTT in many preclinical animal experiments, using different light-absorbing nanomaterials as heat-generating agents. 11-13 An ideal PTT agent should absorb longer wavelength radiation preferably in the near-infrared (NIR) region, where most of the biomolecules do not absorb and could proficiently transfer the absorbed NIR optical energy into heat. The efficacy of in vivo PTT depends greatly on the accumulation of light- responsive nanoparticles, the light-to-heat conversion effi- ciency, and the light dose (i.e., light power density and light exciting time). A number of organic as well as inorganic materials such as indocyanine, 14 phthalocyanine, 15 diketopyr- role, 16 croconaine, 17 porphyrin, 18 Au Nanoparticles, 19 Pd nanoparticle, 20 metal chalcogenides, 21,22 iron oxides, 23 carbon nanotube, 24 and so forth have been demonstrated as potential NIR absorbers. However, for safe and personalized PTT treatment, it is crucial to identify the location and size of the cancer before therapy. In addition to this, real time monitoring of in vivo biodistribution of photothermal agents as well as curative response of the treatment is also equally impor- tant. 25-27 Therefore, theranostic agents with functions of both thermal therapy and imaging have attracted intensive research interests. 28,29 Oral cancer constitutes the sixth most abundant cancer in the world. The nanoparticle-based formulations which are under clinical for oral cancer have been well reviewed by Marcazzan et al. 30 Although a number of studies have shown the practicality of nanoparticle-driven PTT in different surface epithelial cancers using visible continuous wave and pulsed lasers, 31,32 there are very few reports on nanoparticle-mediated PTT in oral cancer. For instance, Stafford et al. have designed iron oxide@Au nanoparticles to target EGFR-positive head and neck tumors and have shown its efficacy in laser-induced thermal therapy. 33 Such hybrid nanoparticles offer new possibilities in clinical trials of MR-guided thermal ablation of head and neck cancer. Afifi et al. have reported the efficacy of Au nanorod-facilitated PTT in buccal pouch carcinoma in a hamster model. They have demonstrated that the improved Received: September 24, 2019 Revised: November 4, 2019 Published: November 4, 2019 Article pubs.acs.org/Langmuir Cite This: Langmuir 2019, 35, 15320-15329 © 2019 American Chemical Society 15320 DOI: 10.1021/acs.langmuir.9b03001 Langmuir 2019, 35, 15320-15329 Downloaded via NATL INST OF TECHNOLOGY ROURKELA on January 9, 2020 at 11:02:18 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.