The Integrated Study Of A Novel Nanoprobe For MR/NIRF Imaging And Photodynamic Therapy Of Nasopharyngeal Carcinoma

Objective: Nasopharyngeal carcinoma?NPC?is a common malignant tumor in the Guangdong area,and there is no effective integrate method of diagnosis and treatment.At present,its diagnosis was mainly by means of epipharyngoscope biopsy and magnetic resonance imaging technique.However,these diagnostic methods have different advantages and disadvantages.As the main diagnostic method,magnetic resonance?MR?imaging can provide fine spatial resolution of deep tissue and diagnose the nasopharyngeal carcinoma and its surrounding tissues.But due to its low sensitivity,the development is limited.Near infrared fluorescence?NIRF?imaging has high sensitivity,and the near infrared fluorescent probes can produce different signals to image by the excition luminescer of specific spectral range.This phenomenon causing by the long wave of light to stimulate the short wave of light is also called up conversion luminescence.Compared with the visible light of traditional optical imaging,near infrared fluorescence penetrates tissue deeper.The complementary advantages of the two imaging techniques can achieve more accurate imaging results.Nasopharyngeal carcinoma is mainly treated with radiation therapy,which causes serious effect on the quality of life of patients.With the rapid development of nanotechnology based molecular imaging and photodynamic therapy,it provides a new idea for the integration of targeted diagnosis and treatment of nasopharyngeal carcinoma.Therefore,we tried to develop a safe and efficient MR/NIRF double mode up conversion nanoprobe and provide a theoretical basis for the integration of the diagnosis and treatment for nasopharyngeal carcinoma.In this paper,we transferred the luminescent rare earth into the gadolinium oxide nanoparticles and synthesized a new stable and safe MR/NIRF double mode up conversion nanoprobe namely Gd₂O₃:Yb³⁺/Er³⁺ by a simple and environment-friendly technique of laser ablation in liquid?LAL?.We observed the nanoparticles were ball-shape and well dispersed by the transmission electron microscopy.The average size was about 7.8nm.Steady state fluorescence spectra showed that the strongest fluorescence signal was at 672 nm.The results of in vitro magnetic resonance showed that the longitudinal relaxation rate of our nanoprobes was 14.52 s-1m M-1,3.5 times compared with the commonly used contrast agent Gd-DTPA?4.16 s-1m M-1?.We systematically evaluated the compatibility of our nanoprobes including cell viability and apoptosis,immunotoxicity,pathological section and subcellular distribution.The results indicated that the toxicity of Gd₂O₃: Yb³⁺/Er³⁺ nanoprobes were very low.Therefore it can be used for further study on the dual model imaging.The nanoprobes entered into the cells successfully and showed red fluorescence under the excitation at 980 nm by the confocal fluorescence microscopy.Meanwhile,the xenografted tumor could be successfully imaged in short time and showed a high contrast enhancement at 30 min post-injection,which indicated that our nanoprobes might be a good MRI contrast agent for biomedical application.In addition,the limited excitation light penetration depth of photosensitizer result in poor treatment of cancer in the traditional photodynamic therapy.Therefore,Gd₂O₃: Yb³⁺/Er³⁺ up conversion nanoparticles were used in the photodynamic therapy of nasopharyngeal carcinoma.As a light conversion medium,the materials can indirectly activate photosensitizer to produce singlet oxygen under near infrared irradiation and achieve the therapeutic effect of nasopharyngeal carcinoma.In this article,we combined photosensitizer with Gd₂O₃: Yb³⁺/Er³⁺ nanoprobes for the photodynamic therapy study and preliminarily evaluated the treatment effects of nasopharyngeal carcinoma.Thus,we synthesized Gd₂O₃: Yb³⁺/Er³⁺ nanoprobes successfully by the technique of laser ablation in liquid.The nanoprobes showed good optical and magnetic characteristics,satisfactory biocompatibility and achieved good dual model image of MR and NIRF.Moreover,there were preliminarily therapeutic effects in vitro photodynamic therapy for nasopharyngeal carcinoma.It provides a theoretical basis for the integration of diagnosis and treatment of nasopharyngeal carcinoma.Methods: 1.We transferred the luminescent rare earth into the gadolinium oxide nanoparticles and synthesized a new nanocomposites namely Gd₂O₃: Yb³⁺/Er³⁺ by LAL and characterized the physical properties of Gd₂O₃:Yb³⁺/Er³⁺ nanoparticles by transmission electron microscopy.2.We systematically evaluated the compatibility of our nanoprobes including cell viability,cell apoptosis and immunotoxicity.3.Tissue damage was detected by pathological biopsy assay.The subcellular distribution of the Gd₂O₃: Yb³⁺/Er³⁺ nanoparticles was analyzed by transmission electron microscopy.4.We tested the fluorescence spectrum by steady-state fluorescence spectroscopy and used fluorescence microscopy to observe the fluorescence of the probes in cells.5.The imaging effect of the Gd₂O₃: Yb³⁺/Er³⁺ nanoparticles was analyzed by magnetic resonance imaging in vitro and in vivo.6.We combined photosensitizer with Gd₂O₃: Yb³⁺/Er³⁺ nanoprobes for the photodynamic therapy study and preliminarily evaluated the treatment effects.Results: 1.We synthesized Gd₂O₃: Yb³⁺/Er³⁺ nanoprobes by the technique of laser ablation in liquid.We observed the nanoparticles were ball-shape and well dispersed by the transmission electron microscopy.The average size was about 7.8 ± 0.3nm.2.Our nanoprobes have satisfactory biocompatibility.There were no significant differences between the experimental group and the negative control group in the cell proliferation and apoptosis.The Superoxide dismutase?SOD?level of Gd₂O₃: Yb³⁺/Er³⁺ group was slightly increased comparing to the positive control group.However,no significant difference was seen between the negative control group and the Gd₂O₃: Yb³⁺/Er³⁺ group.The ROS levels of the Gd₂O₃: Yb³⁺/Er³⁺ group was decreased compared to the positive control group.There was no significant difference in peripheral blood immune factors CD69,CD71,CD25,CD11 b,CD206,respectively.3.The cellular integrity and morphology were not damaged in pathological sections.The transmission electron microscopy showed that there were few nanoparticles were localized in the liver,heart,lung,spleen,kidney,brain and tumor.4.Steady state fluorescence spectra showed that the strongest fluorescence signal was at 672 nm.The red fluorescence of the nanoparticles in cells was observed by the confocal laser scanning microscope.5.The xenografted tumor could be successfully imaged in short time and showed a high contrast enhancement at 30 min post-injection,which indicated that our nanoprobes might be a good MRI contrast agent for biomedical applications.6.CCK-8 results showed that the survival rate of CNE-2 cells decreased after photodynamic therapy.Conclusion: Our group synthesized Gd₂O₃: Yb³⁺/Er³⁺ nanoprobes by the technique of laser ablation in liquid.The nanoprobes showed good optical and magnetic characteristics,satisfactory biocompatibility and achieved good dual model image of MR and NIRF.Moreover,there were preliminarily therapeutic effects in vitro photodynamic therapy for nasopharyngeal carcinoma.It provides a theoretical basis for the integration of diagnosis and treatment of nasopharyngeal carcinoma.