2020 Vol. 10, No. 5

Preface
Preface for the special issue on analysis of drug or drug targets by molecular imaging
Linghui Qian, Shao Q. Yao
2020, 10(5): 前插1-前插2.
Abstract(115) PDF(3)
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To increase the chance of a successful outcome in clinic and in the development of innovative drugs, researchers aim to provide more comprehensive information about the disease and drugs to adapt treatment decisions according to an individual disease's mo-lecular characteristics.

Review Papers
Recent progress in the molecular imaging of therapeutic monoclonal antibodies
Kaifeng He, Su Zeng, Linghui Qian
2020, 10(5): 397-413.
Abstract(94) PDF(2)
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Therapeutic monoclonal antibodies have become one of the central components of the healthcare system and continuous efforts are made to bring innovative antibody therapeutics to patients in need. It is equally critical to acquire sufficient knowledge of their molecular structure and biological functions to ensure the efficacy and safety by incorporating new detection approaches since new challenges like individual differences and resistance are presented. Conventional techniques for determining antibody disposition including plasma drug concentration measurements using LC-MS or ELISA, and tissue dis-tribution using immunohistochemistry and immunofluorescence are now complemented with molecular imaging modalities like positron emission tomography and near-infrared fluorescence imaging to obtain more dynamic information, while methods for characterization of antibody's interaction with the target antigen as well as visualization of its cellular and intercellular behavior are still under development. Recent progress in detecting therapeutic antibodies, in particular, the development of methods suitable for illustrating the molecular dynamics, is described here.

Catalysis-based specific detection and inhibition of tyrosinase and their application
Yunwei Qu, Qing Zhan, Shubo Du, Yang Ding, Bin Fang, Wei Du, Qiong Wu, Haidong Yu, Lin Li, Wei Huang
2020, 10(5): 414-425.
Abstract(125) PDF(1)
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Tyrosinase is an important enzyme in controlling the formation of melanin in melanosome, and plays a key role in the pigmentation of hair and skin. The abnormal expression or activation of tyrosinase is associated with several diseases such as albinism, vitiligo, melanoma and Parkinson disease. Excessive deposition of melanin could cause diseases such as freckles and brown spots in the human body, and it is also closely related to browning of fruits and vegetables and insect molting. Detecting and inhibiting the activity of tyrosinase is of extraordinary value in the progress of diagnosis and treatment of these dis-eases. Therefore, many selective optical detection probes and small molecular inhibitors have been developed, and have made significant contributions to the basic and clinical research on these diseases. In this paper, the detection and inhibition of tyrosinase and their application in whitening products are reviewed, with special emphasis on development of fluorescent probes and inhibitors. Hopefully, this review will help design more efficient and sensitive tyrosinase probes and inhibitors, as well as shed light on novel treatment of diseases such as melanoma.

Fluorescence imaging of drug target proteins using chemical probes
Hao Zhu, Itaru Hamachi
2020, 10(5): 426-433.
Abstract(90) PDF(4)
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Fluorescence imaging can provide valuable information on the expression, distribution, and activity of drug target proteins. Chemical probes are useful small-molecule tools for fluorescence imaging with high structural flexibility and biocompatibility. In this review, we briefly introduce two classes of fluorescent probes for the visualization of drug target proteins. Enzymatically activatable probes make use of the specific enzymatic transformations that generally produce a fluorogenic response upon reacting with target enzymes. Alternatively, specific imaging can be conferred with a ligand that drives the probes to target proteins, where the labeling relies on noncovalent binding, covalent inhibition, or traceless la-beling by ligand-directed chemistry.

Recent advances in construction of small molecule-based fluorophore-drug conjugates
Wenjie Lang, Chaonan Yuan, Liquan Zhu, Shubo Du, Linghui Qian, Jingyan Ge, Shao Q. Yao
2020, 10(5): 434-443.
Abstract(117) PDF(1)
Abstract:

As a powerful tool to advance drug discovery, molecular imaging may provide new insights into the process of drug effect and therapy at cellular and molecular levels. When compared with other detection methods, fluorescence-based strategies are highly attractive and can be used to illuminate pathways of drugs' transport, with multi-color capacity, high specificity and good sensitivity. The conjugates of fluorescent molecules and therapeutic agents create exciting avenues for real-time monitoring of drug delivery and distribution, both in vitro and in vivo. In this short review, we discuss recent developments of small molecule-based fluorophore-drug conjugates, including non-cleavable and cleavable ones, that are capable of visualizing drug delivery.

Fluorescent antibiotics for real-time tracking of pathogenic bacteria
Lu Miao, Weiwei Liu, Qinglong Qiao, Xiaolian Li, Zhaochao Xu
2020, 10(5): 444-451.
Abstract(126) PDF(2)
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The harm of pathogenic bacteria to humans has promoted extensive research on physiological processes of pathogens, such as the mechanism of bacterial infection, antibiotic mode of action, and bacterial antimicrobial resistance. Most of these processes can be better investigated by timely tracking of fluorophore-derived antibiotics in living cells. In this paper, we will review the recent development of fluorescent antibiotics featuring the conjugation with various fluorophores, and focus on their applica-tions in fluorescent imaging and real-time detection for various physiological processes of bacteria in vivo.

Original Articles
Strategies for PET imaging of the receptor for advanced glycation endproducts (RAGE)
Lindsey R. Drake, Allen F. Brooks, Jenelle Stauff, Phillip S. Sherman, Janna Arteaga, Robert A. Koeppe, Aimee Reed, Timothy J. Montavon, Marc B. Skaddan, Peter J.H. Scott
2020, 10(5): 452-465.
Abstract(95) PDF(3)
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The implication of the receptor for advanced glycation end-products (RAGE) in numerous diseases and neurodegenerative disorders makes it interesting both as a therapeutic target and as an inflammatory biomarker. In the context of investigating RAGE as a biomarker, there is interest in developing radio-tracers that will enable quantification of RAGE using positron emission tomography (PET) imaging. We have synthesized potential small molecule radiotracers for both the intracellular ([18F]InRAGER) and extracellular ([18F]RAGER) domains of RAGE. Herein we report preclinical evaluation of both using in vitro (lead panel screens) and in vivo (rodent and nonhuman primate PET imaging) methods. Both radiotracers have high affinity for RAGE and show good brain uptake, but suffer from off-target binding. The source of the off-target PET signal is not attributable to binding to melatonin receptors, but remains unexplained. We have also investigated use of lipopolysaccharide (LPS)-treated mice as a possible animal model with upregulated RAGE for evaluation of new imaging agents. Immunoreactivity of the mouse brain sections revealed increases in RAGE in the male cohorts, but no difference in the female groups. However, it proves challenging to quantify the changes in RAGE due to off-target binding of the radio-tracers. Nevertheless, they are appropriate lead scaffolds for future development of 2nd generation RAGE PET radiotracers because of their high affinity for the receptor and good CNS penetration.

Selective and sensitive fluorescence imaging reveals microenvironment-dependent behavior of NO modulators in the endothelial system
Ying Dong, Xiao-Rong Li, Jia Li, Yi Zang, Xin Li
2020, 10(5): 466-472.
Abstract(83) PDF(4)
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Nitric oxide (NO) is a second messenger playing crucial roles in the signaling of a variety of cellular functions. Due to its pathophysiological significance, various NO modulators have been developed to explore NO pathways and some have been used as therapies. These modulators are often used directly to observe pharmacological effects in cell lines, but their actual effect on intracellular NO level is seldom analyzed. Herein, facilitated by a selective and sensitive fluorescence probe, we observed that some NO modulators displayed unexpected behaviors with both NO scavenger carboxy-PTIO and endothelial nitric oxide synthase (eNOS) inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) failing to decrease intra-cellular free NO level in EA. hy926 cells while NO donor diethylamine-NONOate (DEA?NONOate) and eNOS activator calcimycin (A23187) failing to increase free NO level in human umbilical vein endothelial cell line (HUV-EC-C), although the reagents were confirmed to work normally in the primary human umbilical vein endothelial cells (primary HUVECs) and RAW 264.7 macrophage cells. Further research suggested that these unusual behaviors might be attributed to the cellular microenvironments including both the NO synthase (NOS) level and the endogenous glutathione (GSH) level. Genetically manipulating eNOS level in both cells restores the expected response, while decreasing GSH level restores the ability of DEA?NONOate to increase NO level in HUV-EC-C. These results reveal that the cellular microenvironment has a profound impact on pharmacological effect. Our study suggests GSH as a reservoir for NO in live cells and highlights the value of chemical probes as valuable tools to reveal microenvironment-dependent pharmacological effects.

Electrochemical, spectroscopic, and molecular docking studies of the interaction between the anti-retroviral drug indinavir and dsDNA
Fariba Mollarasouli, Burcu Dogan-Topal, Mehmet Gokhan Caglayan, Tugba Taskin-Tok, Sibel A. Ozkan
2020, 10(5): 473-481.
Abstract(93) PDF(3)
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In this study, an electrochemical DNA biosensor was developed using a straightforward methodology to investigate the interaction of indinavir with calf thymus double-stranded deoxyribonucleic acid (ct-dsDNA) for the first time. The decrease in the oxidation signals of deoxyguanosine (dGuo) and deoxy-adenosine (dAdo), measured by differential pulse voltammetry, upon incubation with different con-centrations of indinavir can be attributed to the binding mode of indinavir to ct-dsDNA. The currents of the dGuo and dAdo peaks decreased linearly with the concentration of indinavir in the range of 1.0-10.0μg/mL. The limit of detection and limit of quantification for indinavir were 0.29 and 0.98μg/mL, respectively, based on the dGuo signal, and 0.23 and 0.78μg/mL, respectively, based on the dAdo signal. To gain further insights into the interaction mechanism between indinavir and ct-dsDNA, spectroscopic measurements and molecular docking simulations were performed. The binding constant (Kb) between indinavir and ct-dsDNA was calculated to be 1.64 × 108 M-1, based on spectrofluorometric measure-ments. The obtained results can offer insights into the inhibitory activity of indinavir, which could help to broaden its applications. That is, indinavir can be used to inhibit other mechanisms and/or hallmarks of viral diseases.

A carbon nanoparticle-peptide fluorescent sensor custom-made for simple and sensitive detection of trypsin
Shanshan Hou, Tingting Feng, Na Zhao, Jiaxin Zhang, Huibin Wang, Ning Liang, Longshan Zhao
2020, 10(5): 482-489.
Abstract(166) PDF(3)
Abstract:

Herein, we report a novel sensor to detect trypsin using a purpose-designed fluorescein-labelled peptide with negatively charged carbon nanoparticles (CNPs) modified by acid oxidation. The fluorescence of the fluorescein-labelled peptide was quenched by CNPs. The sensor reacted with trypsin to cleave the peptide, resulting in the release of the dye moiety and a substantial increase in fluorescence intensity, which was dose-and time-dependent, and trypsin could be quantified accordingly. Correspondingly, the biosensor has led to the development of a convenient and efficient fluorescent method to measure trypsin activity, with a detection limit of 0.7μg/mL. The method allows rapid determination of trypsin activity in the normal and acute pancreatitis range, suitable for point-of-care testing. Furthermore, the applicability of the method has been demonstrated by detecting trypsin in spiked urine samples.

Short Communication
A pyrene-based ratiometric fluorescent probe with a large Stokes shift for selective detection of hydrogen peroxide in living cells
Qingxin Chen, Ke Cheng, Wanhe Wang, Liu Yang, Yusheng Xie, Ling Feng, Jie Zhang, Huatang Zhang, Hongyan Sun
2020, 10(5): 490-497.
Abstract(169) PDF(4)
Abstract:

Hydrogen peroxide (H2O2) plays a significant role in regulating a variety of biological processes. Dys-regulation of H2O2 can lead to various diseases. Although numerous fluorescent imaging probes for H2O2 have been reported, the development of H2O2 ratiometric fluorescent probe with large Stokes shift re-mains rather limited. Such probes have shown distinct advantages, such as minimized interference from environment and improved signal-to noise ratio. In this work, we reported a new pyrene-based com-pound Py-VPB as H2O2 fluorescent probe in vitro. The probe demonstrated ratiometric detection behavior, large Stokes shift and large emission shift. In addition, the probe showed high sensitivity and selectivity towards H2O2 in vitro. Based on these excellent properties, we successfully applied Py-VPB to the visualization of exogenous and endogenous H2O2 in living cells. Cell imaging study also showed that our probe was localized in the mitochondria. We envision that the probe can provide a useful tool for unmasking the biological roles of mitochondrial H2O2 in living systems.

Gold Award for Top Cited Papers
2020, 10(5)
Abstract(170) PDF(7)
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Silver Award for Top Cited Papers
2020, 10(5)
Abstract(55) PDF(1)
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