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Abstract Carbon dots (CDs) have been extensively investigated as prime candidates for developing tumour theranostic platform due to their tunable fluorescence emission and excitation, good photostability, high water solubility and biocompatibility. Herein, we will update the recent research and latest development on the preparation, hydrophilicity, biotoxicity and optical property of CDs, as well as their applications in multimodal bioimaging and anticancer drug delivery. We will mainly highlight their applications in in vivo imaging and tumour‐targeted theranostics with a special emphasis on large amino acid‐mimicking carbon quantum dots‐based tumour theranostics through a large neutral amino acid transporter 1 (LAT1)‐mediated targeted strategy. Finally, we will also discuss the current status, key challenges and future directions of CDs in tumour theranostics. We expect that this review will summarize recent advances to inspire more researches on CDs for biomedical and clinical applications in the near future.

Carbon dots (CDs) have been extensively investigated as prime candidates for developing tumour theranostic platform due to their tunable fluorescence emission and excitation, good photostability, high water solubility and biocompatibility. Herein, we will update the recent research and latest development on the preparation, hydrophilicity, biotoxicity and optical property of CDs, as well as their applications in multimodal bioimaging and anticancer drug delivery. We will mainly highlight their applications in in vivo imaging and tumour‐targeted theranostics with a special emphasis on large amino acid‐mimicking carbon quantum dots‐based tumour theranostics through a large neutral amino acid transporter 1 (LAT1)‐mediated targeted strategy. Finally, we will also discuss the current status, key challenges and future directions of CDs in tumour theranostics. We expect that this review will summarize recent advances to inspire more researches on CDs for biomedical and clinical applications in the near future. [ABSTRACT FROM AUTHOR]

α‐Methyl‐l‐tyrosine (AMT) has a high affinity for the cancer‐specific l‐type amino acid transporter 1 (LAT1). Therefore, we established an anti‐cancer therapy, with 211At‐labeled α‐methyl‐l‐tyrosine (211At‐AAMT) as a carrier of 211At into tumors. 211At‐AAMT had high affinity for LAT1, inhibited tumor cell growth, and induced DNA double‐stranded breaks in vitro. We evaluated the accumulation of 211At‐AAMT in vivo and the role of LAT1. Treatment with 0.4 MBq/mouse 211At‐AAMT inhibited tumor growth in the PANC‐1 tumor model and 1 MBq/mouse 211At‐AAMT inhibited metastasis in the lung of the B16F10 metastasis model. Our results suggested that 211At would be useful for anti‐cancer therapy and that LAT1 is suitable as a target for radionuclide therapy. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disorder that causes progressive paralysis. L-Citrulline is a non-essential neutral amino acid produced by L-arginine via nitric oxide synthase (NOS). According to previous studies, the pathogenesis of ALS entails glutamate toxicity, oxidative stress, protein misfolding, and neurofilament disruption. In addition, L-citrulline prevents neuronal cell death in brain ischemia; therefore, we investigated the change in the transport of L-citrulline under various pathological conditions in a cell line model of ALS. We examined the uptake of [ 14 C]L-citrulline in wild-type (hSOD1wt/WT) and mutant NSC-34/ SOD1 G93A (MT) cell lines. The cell viability was determined via MTT assay. A transport study was performed to determine the uptake of [ 14 C]L-citrulline. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was performed to determine the expression levels of rat large neutral amino acid transported 1 (rLAT1) in ALS cell lines. Nitric oxide (NO) assay was performed using Griess reagent. L-Citrulline had a restorative effect on glutamate induced cell death, and increased [ 14 C]L-citrulline uptake and mRNA levels of the large neutral amino acid transporter (LAT1) in the glutamate-treated ALS disease model (MT). NO levels increased significantly when MT cells were pretreated with glutamate for 24 h and restored by co-treatment with L-citrulline. Co-treatment of MT cells with L-arginine, an NO donor, increased NO levels. NSC-34 cells exposed to high glucose conditions showed a significant increase in [ 14 C]L-citrulline uptake and LAT1 mRNA expression levels, which were restored to normal levels upon co-treatment with unlabeled L-citrulline. In contrast, exposure of the MT cell line to tumor necrosis factor alpha, lipopolysaccharides, and hypertonic condition decreased the uptake significantly which was restored to the normal level by co-treating with unlabeled L-citrulline. L-Citrulline can restore NO levels and cellular uptake in ALS-affected cells with glutamate cytotoxicity, pro-inflammatory cytokines, or other pathological states, suggesting that L-citrulline supplementation in ALS may play a key role in providing neuroprotection.

α-Methyl-l-tyrosine (AMT) has a high affinity for the cancer-specific l-type amino acid transporter 1 (LAT1). Therefore, we established an anti-cancer therapy, with 211 At-labeled α-methyl-l-tyrosine ( 211 At-AAMT) as a carrier of 211 At into tumors. 211 At-AAMT had high affinity for LAT1, inhibited tumor cell growth, and induced DNA double-stranded breaks in vitro. We evaluated the accumulation of 211 At-AAMT in vivo and the role of LAT1. Treatment with 0.4 MBq/mouse 211 At-AAMT inhibited tumor growth in the PANC-1 tumor model and 1 MBq/mouse 211 At-AAMT inhibited metastasis in the lung of the B16F10 metastasis model. Our results suggested that 211 At would be useful for anti-cancer therapy and that LAT1 is suitable as a target for radionuclide therapy., (© 2020 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)