Elsevier

Biomaterials

Volume 167, June 2018, Pages 216-225
Biomaterials

Near infrared-emitting persistent luminescent nanoparticles for Hepatocellular Carcinoma imaging and luminescence-guided surgery

https://doi.org/10.1016/j.biomaterials.2018.01.031Get rights and content

Abstract

Hepatocellular carcinoma (HCC), the fifth most common cancer worldwide, is increasing nowadays and poses a serious threat to human health. However, if treated effectively and timely, it is clinically manageable or curable. Therefore, accurate detection and complete surgical resection remain priorities for HCC with a high potential of improving both survival and quality of life. Lacking of real-time guide technology, traditional surgery are usually relied on the subjective experience of surgeon, which have the limitation of high sensitivity detection tumor. Here, we developed a contrast agent, ZnGa2O4Cr0.004 (ZGC), used for guided surgery during operation to accurate delineation of HCC. ZGC showed excellent long-lasting afterglow properties that lasted for hours, which can aid in real-time guided surgery. Meanwhile, ZGC display high spatial resolution and deep penetration during pre-operation for diagnostic computed tomography (CT). Interestingly, we observed reverse imaging in the tumor region, known as a “dark hole”, which further improves the contrast for surgery. This new multi-modality nanoparticle has great potential for accurate liver cancer imaging and resection guidance.

Graphical abstract

The scheme of ZnGa2O4Cr0.004 (ZGC) used for Hepatocellular carcinoma (HCC) multi-modal diagnosis and treatment, which provided attractive synergistic advantages for biomedical applications in the future.

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Introduction

Surgery is the mainstay of Hepatocellular Carcinoma(HCC)treatment. However, tumor recurrence rate complicates 75% of cases at 5 years after resection. Therefore, complete surgical resection remains priorities for HCC with a high potential of improving both survival and quality of life [1]. Optical imaging has be received significant attention used for surgery guided owing to its highly sensitive, noninvasive, and cost-effective characteristics, and for allowing real-time imaging of whole organs at the macroscopic scale with the potential to zoom in and to visualize macroscopic structures to microcosmic structures in regions of interest (ROI) [[2], [3], [4]]. To date, various fluorescence imaging studies have been conducted in vitro and ex vivo. A series of fluorescent probes, ranging from organic fluorophores to plasmonic nanoparticles, such as quantum dots [5], metal nanoclusters [6,7], and upconversion nanocrystals [8], have been applied to fluorescence imaging [[9], [10], [11]]. However, conventional fluorescent probes have limited by tissue penetration depth, and are subject to photobleaching and optical quenching [12,13]. Moreover, the required in situ excitation of conventional fluorescent probes during in vivo imaging produces strong tissue autofluorescence, light scattering and poor signal-to-noise ratio (SNR) [14]. Near-infrared (NIR) fluorescence imaging, with shows higher sensitivity and deeper penetration, is an attractive modality for cancer diagnosis among potential fluorescence imaging technologies [15,16]. Recently, several types of NIR emission agents such as CH1055 [17], Mn-dopant NaYF4:Yb/Er UCNPs [18], and C-dot [19] have been reported for reducing background noise in in vitro and in vivo imaging, however, in situ excitation during imaging is still needed.

The persistent luminescent nanoparticles (PLNPs) get increasing attention in bioimaging recently, for the afterglow can last for several hours after been excited in vitro [[20], [21], [22]]. Without continuous excitation, the SNR can be significantly improved account of avoiding background noise from in situ excitation [[23], [24], [25]]. NIR-emitting PLNPs (NPLNPs) fall within the tissue transparency window, which is advantageous for long-term in vivo imaging with high SNR [26], deep penetration and no need for in situ excitation [27,28]. The temporal separation of excitation and luminescence properties of NPLNPs makes them ideal as in vivo luminescence imaging contrast reagents [29], providing new possibilities for long-term in vivo high-sensitivity imaging of tumor [30,31]. Therefore, increasing attention has focused on the development and application of NPLNPs. Some NPLNPs have been successfully applied in bioimaging. Yan et al. synthesized functional NPLNPs (Zn2.94Ga1.96Ge2O10:Cr3+, Pr3+) for in vivo bioimaging, monitoring more than 450 min in vivo without any excitation source [32]. Qiu et al. utilized FA-conjugated Zn1.1Ga1.8Sn0.1O4:Cr3+ (ZGSC) nanoparticles for targeted optical imaging of colorectal carcinoma. The small-sized nanoparticles displayed remarkably long persistent luminescence for over 10 h in the NIR region, and rendered specific targeting abilities with enhanced SNR [33]. Richard and co-workers synthesized non-toxic NPLNPs (ZnGa1.995Cr0.005O4) to achieve the mechanism of in vivo imaging of colorectal carcinoma [34]. Most nanoparticles accumulated in the liver upon intravenous administration, which was probably associated with a global uptake by the reticulo-endothelial system (RES) [[35], [36], [37]]. The RES, especially in the liver, constituted of Kupffer cells, which represent the most abundant macrophage population in the body [38,39]. The RES swallows the nanoparticles, yet tumor cells do not [40], this phenomenon coincidentally create a “dark hole” for imaging, which has exhibited great advantages for NPLNP in in vivo luminescence imaging with high signal-to-background ratio (SBR).

In the current study, we developed a ZnGa2O4Cr0.004 NPLNPs (ZGC) used for luminescence imaging guidance during HCC operation, and supplied a pre-operation CT imaging. ZGC aided in accurately delineating HCC in live mice and more radical excision of tumor tissue. ZGC exhibited excellent NIR emission at 696 nm, with long afterglow luminescence lasting for 5 h, indicating the capacity for real-time in vivo imaging continuously for long periods. In addition, ZGC have great advantages for luminescence-guided liver-resection with high SBR. Interestingly, we found ZGC accumulated in the liver tissue, but less taken up by the HCC tumor tissue. The tumor in the liver looked like a “dark hole” under all imaging technologies. Taken together, the results indicate that ZGC offers attractive synergistic advantages for biomedical applications (Scheme 1).

Section snippets

Materials

Zn(NO3)2·6H2O (98%), Cr(NO3)3·9H2O (99.90%), Ga(NO3)3·H2O (99.90%), isopropanol, hydrochloric acid (36%) and ammonium hydroxide (28%) were purchased from Alfa Aesar (Beijing, China). All chemicals used without further purification.

ZGC synthesis

ZGCs synthesized following a previously published synthetic method with minor modification [41]. The synthetic route shown in Scheme 1A. Zn(NO3)2·6H2O (2 mmol), Ga(NO3)3·H2O (2 mmol) and Cr(NO3)3·9H2O (0.04 mmol) were added to 15 mL of deionized water (DI water) under

Synthesis and characterization of ZGC NPLNPs

The ZGC NPLNPs synthesized by a previously reported hydrothermal method. Ga(NO3)3, Zn(NO3)2, and Cr(NO3)3 precursor solutions were mixed, and ammonium hydroxide (28%, wt) was added to achieve a pH of 9. The mixed solution was stirred at 220 °C for 10 h. The ZGC NPLNPs used for biological applications in our study, as shown in Scheme 1B. The nanoparticles size and size distribution shown in 1A-C. ZGC showed a narrow size distribution, with an average of approximately 10 nm (Fig. 1C), as observed

Conclusion

We synthesized a “dark hole” multi-modal nanoparticle ZnGa2O4Cr0.004 NPLNP (ZGC) for liver cancer imaging and luminescence-guided surgery. ZGC, as a non-toxic multi-modality nanoparticle based on CT and NIR persistent luminescence, could guide orthotopic tumor surgery in deep tissues, especially in the liver. ZGC exhibited a CT contrast effect because of its attenuation of X-rays caused by the large number of Zn and Ga molecules in ZGC. ZGC helped in accurately delineating HCC in live mice, and

Acknowledgments

The authors thank Ziyu Han, Hongmei Jiang, Xiaodong Song, Shixin Jiang, Yuhao Liu, Yujie Zhang and Kun Su for assistance with finishing the experiments. This study was supported by the National Natural Science Foundation of China [grant number 81627805, 81601576, 81227901, 61231004, 81501540, 61671449, 81401471, 81527805]; the National Key Research and Development Program of China [grant number 2016YFC0106500, 2017YFA0205200, 2016YFA0201401, 2016YFC0102601]; the United Fund of National Natural

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