Chemical Approach to Positional Isomers of Glucose-Platinum Conjugates Reveals Specific Cancer Targeting through Glucose-Transporter-Mediated Uptake in Vitro and in Vivo

Nitroxide radical contrast agents for safe magnetic resonance imaging: progress, challenges, and perspectives

Magnetic resonance imaging (MRI) is considered one of the most valuable diagnostic technologies in the 21st century. To enhance the image contrast of anatomical features, MRI contrast agents have been widely used in clinical MRI diagnosis, especially those based on gadolinium, manganese, and iron oxide. However, these metal-based MRI contrast agents show potential toxicity to patients, which urges researchers to develop novel MRI contrast agents that can replace metal-based MRI contrast agents. Metal-free nitroxide radical contrast agents (NRCAs) effectively overcome the shortcomings of metal-based contrast agents and also have many advantages, including good biocompatibility, prolonged systemic circulation time, and easily functionalized structures. Importantly, since NRCAs acquire MRI signals with standard tissue water 1H relaxation mechanisms, they have great potential to realize clinical translation among many metal-free MRI contrast agents. At present, NRCAs have been proposed as an effective substitute for metal-based MRI contrast agents. Herein, this review first briefly introduces NRCAs, including their composition, classification, mechanism of action, application performances and advantages. Then, this review highlights the progress of NRCAs, including small molecule-based NRCAs and polymer-based NRCAs. Finally, this review also discusses the challenges and future perspectives of NRCAs.

Is ASCT2 a Suitable Vector for the Selective Delivery of Anticancer Drugs? Modification of Glutamine at Either the Carboxylate or the Side Chain Hinders Binding and Transport

The Alanine, Serine, and Cysteine Transporter 2 (ASCT2) transports glutamine into cells and is upregulated in many cancers. Attachment to glutamine to enable ASCT2 to transport anticancer agents into cells has been proposed, but the impact of such modifications is a critical determinant of the potential of this strategy. Transport via ASCT2 of two glutamine analogues modified in ways that reflect possible mechanisms for attaching anticancer agents was studied. The aim was to determine if the modification of glutamine interferes with its transport via ASCT2 and thereby establish whether the conjugation of drugs to glutamine can facilitate the accumulation of anticancer drugs in cancer cells. L-theanine and a glutamine derivative modified at the carboxylate (7) were applied to Xenopus laevis oocytes expressing ASCT2. Two-electrode voltage clamp electrophysiology was used to measure substrate-elicited currents over a range of membrane potentials. Compound 7 was identified as neither a substrate nor an inhibitor while L-theanine was identified as an inhibitor of ASCT2. Thus, modification of glutamine in these ways prevents it from acting as a substrate and suggests that ASCT2 may not be a suitable target for delivery of anticancer drugs attached via either the carboxylate or side chain positions.

Glucose Transporter-Targeting Chimeras Enabling Tumor-Selective Degradation of Secreted and Membrane Proteins

Tumor-selective degradation of target proteins has the potential to offer superior therapeutic benefits with maximized therapeutic windows and minimized off-target effects. However, the development of effective lysosome-targeted degradation platforms for achieving selective protein degradation in tumors remains a substantial challenge. Cancer cells depend on certain solute carrier (SLC) transporters to acquire extracellular nutrients to sustain their metabolism and growth. This current study exploits facilitative glucose transporters (GLUTs), a group of SLC transporters widely overexpressed in numerous types of cancer, to drive the endocytosis and lysosomal degradation of target proteins in tumor cells. GLUT-targeting chimeras (GTACs) were generated by conjugating multiple glucose ligands to an antibody specific for the target protein. We demonstrate that the constructed GTACs can induce the internalization and lysosomal degradation of the extracellular and membrane proteins streptavidin, tumor necrosis factor-alpha (TNF-α), and human epidermal growth factor receptor 2 (HER2). Compared with the parent antibody, the GTAC exhibited higher potency in inhibiting the growth of tumor cells in vitro and enhanced tumor-targeting capacity in a tumor-bearing mouse model. Thus, the GTAC platform represents a novel degradation strategy that harnesses an SLC transporter for tumor-selective depletion of secreted and membrane proteins of interest.

Imaging Diffusion and Stability of Single-Chain Polymeric Nanoparticles in a Multi-Gel Tumor-on-a-Chip Microfluidic Device

The performance of single-chain polymeric nanoparticles (SCPNs) in biomedical applications highly depends on their conformational stability in cellular environments. Until now, such stability studies are limited to 2D cell culture models, which do not recapitulate the 3D tumor microenvironment well. Here, a microfluidic tumor-on-a-chip model is introduced that recreates the tumor milieu and allows in-depth insights into the diffusion, cellular uptake, and stability of SCPNs. The chip contains Matrigel/collagen-hyaluronic acid as extracellular matrix (ECM) models and is seeded with cancer cell MCF7 spheroids. With this 3D platform, it is assessed how the polymer's microstructure affects the SCPN's behavior when crossing the ECM, and evaluates SCPN internalization in 3D cancer cells. A library of SCPNs varying in microstructure is prepared. All SCPNs show efficient ECM penetration but their cellular uptake/stability behavior depends on the microstructure. Glucose-based nanoparticles display the highest spheroid uptake, followed by charged nanoparticles. Charged nanoparticles possess an open conformation while nanoparticles stabilized by internal hydrogen bonding retain a folded structure inside the tumor spheroids. The 3D microfluidic tumor-on-a-chip platform is an efficient tool to elucidate the interplay between polymer microstructure and SCPN's stability, a key factor for the rational design of nanoparticles for targeted biological applications.

Dual-reactive single-chain polymer nanoparticles for orthogonal functionalization through active ester and click chemistry

Glucose has been extensively studied as a targeting ligand on nanoparticles for biomedical nanoparticles. A promising nanocarrier platform are single-chain polymer nanoparticles (SCNPs). SCNPs are well-defined 5-20 nm semi-flexible nano-objects, formed by intramolecularly crosslinked linear polymers. Functionality can be incorporated by introducing labile pentafluorophenyl (PFP) esters in the polymer backbone, which can be readily substituted by functional amine-ligands. However, not all ligands are compatible with PFP-chemistry, requiring different ligation strategies for increasing versatility of surface functionalization. Here, we combine active PFP-ester chemistry with copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) click chemistry to yield dual-reactive SCNPs. First, the SCNPs are functionalized with increasing amounts of 1-amino-3-butyne groups through PFP-chemistry, leading to a range of butyne-SCNPs with increasing terminal alkyne-density. Subsequently, 3-azido-propylglucose is conjugated through the glucose C1- or C6-position by CuAAC click chemistry, yielding two sets of glyco-SCNPs. Cellular uptake is evaluated in HeLa cancer cells, revealing increased uptake upon higher glucose-surface density, with no apparent positional dependance. The general conjugation strategy proposed here can be readily extended to incorporate a wide variety of functional molecules to create vast libraries of multifunctional SCNPs.

Selection of Galectin-Binding Ligands from Synthetic Glycopeptide Libraries

Galectins, a class of carbohydrate-binding proteins, play a crucial role in various physiological and disease processes. Therefore, the identification of ligands that efficiently bind these proteins could potentially lead to the development of new therapeutic compounds. In this study, we present a method that involves screening synthetic click glycopeptide libraries to identify lectin-binding ligands with low micromolar affinity. Our methodology, initially optimized using Concanavalin A, was subsequently applied to identify binders for the therapeutically relevant galectin 1. Binding affinities were assessed using various methods and showed that the selected glycopeptides exhibited enhanced binding potency to the target lectins compared to the starting sugar moieties. This approach offers an alternative means of discovering galectin-binding ligands as well as other carbohydrate-binding proteins, which are considered important therapeutic targets.

2D and 3D anticancer properties of C2-functionalised glucosamine-Pt (IV) prodrugs based on cisplatin scaffold

A series of C2-functionalied Pt (IV) glycoconjugates based on glucosamine have been synthesised, characterised and tested as anticancer agents on a series of different 2D and 3D cancer cell lines. The carbohydrate will act as a targeted delivery system to improve the selectivity, exploiting the Warburg Effect and the GLUTs receptors that are overexpressed in most of the cancer cells. The hydroxyl at C2 of the carbohydrates does not participate in hydrogen bonding with the GLUTs receptors, making C2 an attractive position for drug conjugation as seen in literature. In this study, we use the amino functionality at the C2 position in glucosamine and Copper-catalysed Azide-Alkyne Cycloaddition "click" (CuAAC) reaction to connect the prodrug Pt (IV) scaffold to the carbohydrate. We have investigated complexes with different linker lengths, as well as acetyl protected and free derivatives. To the best of our knowledge, this study represents the first series of Pt (IV) glucosamine-conjugates functionalised at C2.

Glycosidase-activated H2S donorsto enhance chemotherapy efficacy

Hydrogen sulfide (H2S) plays a critical role in cancer biology. Herein, we developed a series of glycosidase-triggered hydrogen sulfide (H2S) donors by connecting sugar moieties (including glucose, galactose and mannose) to COS donors via a self-immolative spacer. In the presence of corresponding glycosidases, H2S was gradually released from these donors in PBS buffer with releasing efficiencies from 36 to 67 %. H2S release was also detected by H2S probe WSP-1 after treatment HepG2 cells with Man1. Cytotoxicities of these glycosylated H2S donors were evaluated against HepG2 by MTT assay. Among them, Man1 and Man2 exhibited an obvious reduction of cell viability in HepG2 cells, with cell viability as 37.6 % for 80 μM of Man. Consistently, significant apoptosis was observed in HepG2 cells after treatment with Man1 and Man2. Finally, We evaluated the potential of Man1 for combination therapy with doxorubicin. A synergistic effect was observed between Man1 and Doxorubicin in HepG2 and Hela cells. All these results indicated glycosidase-activated H2S donorshave promising potential for cancer therapy.

Design, synthesis and biological evaluation of the positional isomers of the galactose conjugates able to target hepatocellular carcinoma cells via ASGPR-mediated cellular uptake and cytotoxicity

Galactose as a recognizing motif for asialoglycoprotein receptor (ASGPR) is a widely accepted vector to deliver cytotoxic agents in the therapy of hepatocellular carcinoma (HCC), however, the individual hydroxyl group of galactose (Gal) contributed to recognizing ASGPR is obscure and remains largely unanswered in the design of glycoconjugates. Herein, we designed and synthesized five positional isomers of Gal-anthocyanin Cy5.0 conjugates and three Gal-doxorubicin (Dox) isomers, respectively. The fluorescence intensity of Gal-Cy5.0 conjugates accumulated in cancer cells hinted the optimal modification sites of positions C2 and C6. Comparing to the cytotoxicity of other conjugates, C2-Gal-Dox (11) was the most potent. Moreover, Gal-Dox conjugates significantly the toxicity of Dox. A progressively lower internalization capacity and siRNA technology implied the cellular uptake and cytotoxicity directly related to the ASGPR expression level. Accordingly, position C2 of galactose may be the best substitution site via ASGPR mediation in the design of anti-HCC glycoconjugates.

Synthesis and Biological Evaluation of a Novel Sugar-Conjugated Platinum(II) Complex Having a Tumor-Targeting Effect

We designed and synthesized a novel platinum complex conjugated with 2-fluorinated 2-deoxyglucoside, named FGC-Pt, to capitalize on the Warburg effect and metabolic trapping properties of [18F]2-deoxy-2-fluoro-d-glucose ([18F]FDG). Then, we conducted comprehensive in vitro and in vivo studies to evaluate the effects of FGC-Pt. In vitro cytotoxicity assays using HeLa cells revealed that FGC-Pt exhibited concentration-dependent cytotoxicity, even though its cytotoxic effect was less pronounced than that of cisplatin. In the evaluation of in vivo biodistribution in mice, platinum concentration in tumors and major organs (muscle, bone, blood, liver, and kidney) and the ratio of platinum concentration in tumors to major organs following the tail vein injection of FGC-Pt and cisplatin suggest that FGC-Pt is more retained in tumors than in other organs and tends to accumulate in tumors more than cisplatin. Furthermore, an in vivo assessment of the antitumor effect conducted in A549 cell-bearing mice demonstrated that FGC-Pt possesses substantial potential as an antitumor agent. It exhibited a tumor growth-inhibitory effect comparable to that of cisplatin while inducing lower toxicity, as evidenced by lower weight loss after administration. Herein, we successfully produced a novel compound with a tumor-growth-inhibitory effect comparable to that of cisplatin and low toxicity.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.

Chitosan-Biotin-Conjugated pH-Responsive Ru(II) Glucose Nanogel: A Dual Pathway of Targeting Cancer Cells and Self-Drug Delivery

The current study paves the way for improved chemotherapy by creating pH-responsive nanogels (NGs) (GC1 and GC2) loaded with synthetic ruthenium(II) arene complexes to increase biological potency. NGs are fabricated by the conjugation of chitosan (CTS)-biotin biopolymers that selectively target the cancer cells as CTS has the pH-responsive property, which helps in releasing the drug in cancer cells having pH ∼ 5.5, and biotin provides the way to target the cancer cells selectively due to the overexpression of integrin. The synthesized compounds and NGs were thoroughly characterized using various spectroscopic and analytical techniques such as NMR, electrospray ionization-mass spectrometry, Fourier transform infrared, UV-vis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, rheology, Brunauer-Emmett-Teller, and others. NGs displayed exceptional increased efficacy toward cancerous cells with IC50 values ranging from 7.50 to 18.86 μM via induced apoptosis in three human cancer cell lines. Apart from its potency, NGs were found to be highly selective toward cancer cells. Moreover, based on the results of immunoblot analysis, it was observed that the synthesized compounds exhibit a significant increase in the expression of cleaved caspase-3 and a decrease in the expression of the antiapoptotic protein BCL-XL. Interestingly, the complexes were discovered to have the additional capability of catalyzing the conversion of NADH to NAD+, leading to the generation of radical oxygen species within the cells. Additionally, it was discovered that NG-induced apoptosis depends on ROS production and DNA binding. A narrower range of LD50 values (1185.93 and 823.03 μM) was seen after administering NGs to zebrafish embryos in vivo. The results support the use of drug-loaded NGs as potential chemotherapeutic and chemopreventive agents for human cancer cells.

Direct mapping of kidney function by DCE-MRI urography using a tetrazinanone organic radical contrast agent

Chronic kidney disease (CKD) and acute kidney injury (AKI) are ongoing global health burdens. Glomerular filtration rate (GFR) is the gold standard measure of kidney function, with clinical estimates providing a global assessment of kidney health without spatial information of kidney- or region-specific dysfunction. The addition of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) to the anatomical imaging already performed would yield a 'one-stop-shop' for renal assessment in cases of suspected AKI and CKD. Towards urography by DCE-MRI, we evaluated a class of nitrogen-centered organic radicals known as verdazyls, which are extremely stable even in highly reducing environments. A glucose-modified verdazyl, glucoverdazyl, provided contrast limited to kidney and bladder, affording functional kidney evaluation in mouse models of unilateral ureteral obstruction (UUO) and folic acid-induced nephropathy (FAN). Imaging outcomes correlated with histology and hematology assessing kidney dysfunction, and glucoverdazyl clearance rates were found to be a reliable surrogate measure of GFR.

Single-chain polymer nanoparticles in biomedical applications

Single-chain polymer nanoparticles (SCNPs) are a well-defined and uniquely sized class of polymer nanoparticles. The advances in polymer science over the past decades have enabled the development of a variety of intramolecular crosslinking systems, leading to particles in the 5-20 nm size regime. Which is aligned with the size regime of proteins and therefore making SCNPs an interesting class of NPs for biomedical applications. The high modularity of SCNP design and the ease of their functionalization have led to growing research interest. In this review, we describe different crosslinking systems, as well as the preparation of functional SCNPs and the variety of biomedical applications that have been explored.

Development of Novel Pt(IV)-Carbohydrate Derivatives as Targeted Anticancer Agents against Osteosarcoma

Despite the enormous importance of cisplatin as a chemotherapeutic agent, its application is impacted by dose-limiting side effects and lack of selectivity for cancer cells. Researchers can overcome these issues by taking advantage of the pro-drug nature of the platinum(IV) oxidation state, and by modifying the coordination sphere of the metal centre with specific vectors whose receptors are overexpressed in tumour cell membranes (e.g., carbohydrates). In this paper we report the synthesis of four novel carbohydrate-modified Pt(IV) pro-drugs, based on the cisplatin scaffold, and their biological activity against osteosarcoma (OS), a malignant tumour which is most common in adolescents and young adults. The carbohydrate-targeting vectors and Pt scaffold are linked using copper-catalysed azide-alkyne cycloaddition (CuAAC) chemistry, which is synonymous with mild and robust reaction conditions. The novel complexes are characterised using multinuclear 1D-2D NMR (¹H, ¹³C and ¹⁹⁵Pt), IR, HR-MS, Elem. Analyses, and CV. Cytotoxicity on 2D and 3D and cell morphology studies on OS cell lines, as well as non-cancerous human foetal osteoblasts (hFOBs), are discussed.

Platinum glycoconjugates: "Sweet bullets" for targeted cancer therapy?

Cancer, which is characterized by uncontrolled proliferation of abnormal cells, is a leading cause of morbidity and mortality worldwide. Cytotoxic chemotherapy, especially with platinum drugs, remains the mainstay of cancer treatment in the clinical setting. Despite phenomenal success, small-molecule chemotherapeutic drugs suffer from some serious drawbacks. Lack of cancer selectivity and the ensuing side effects mar the therapeutic potential of these drugs. Glycoconjugation has emerged as an attractive strategy for imparting selectivity and improving pharmacokinetics of cytotoxic agents. In this review, we provide an overview of the glycoconjugation strategy and then illustrate the application of this strategy with the help of some concrete examples of platinum based glycoconjugates. At the end we discuss a few important aspects of these glycoconjugates which merit further investigations.

The Role of Solute Carrier Transporters in Efficient Anticancer Drug Delivery and Therapy

Transporter-mediated drug resistance is a major obstacle in anticancer drug delivery and a key reason for cancer drug therapy failure. Membrane solute carrier (SLC) transporters play a crucial role in the cellular uptake of drugs. The expression and function of the SLC transporters can be down-regulated in cancer cells, which limits the uptake of drugs into the tumor cells, resulting in the inefficiency of the drug therapy. In this review, we summarize the current understanding of low-SLC-transporter-expression-mediated drug resistance in different types of cancers. Recent advances in SLC-transporter-targeting strategies include the development of transporter-utilizing prodrugs and nanocarriers and the modulation of SLC transporter expression in cancer cells. These strategies will play an important role in the future development of anticancer drug therapies by enabling the efficient delivery of drugs into cancer cells.

Synthesis and Antiparasitic Activity of New Trithiolato-Bridged Dinuclear Ruthenium(II)-arene-carbohydrate Conjugates

Eight novel carbohydrate-tethered trithiolato dinuclear ruthenium(II)-arene complexes were synthesized using CuAAC ‘click’ (Cu(I)-catalyzed azide-alkyne cycloaddition) reactions, and there in vitro activity against transgenic T. gondii tachyzoites constitutively expressing β-galactosidase (T. gondii β-gal) and in non-infected human foreskin fibroblasts, HFF, was determined at 0.1 and 1 µM. When evaluated at 1 µM, seven diruthenium-carbohydrate conjugates strongly impaired parasite proliferation by >90%, while HFF viability was retained at 50% or more, and they were further subjected to the half-maximal inhibitory concentration (IC50) measurement on T. gondii β-gal. Results revealed that the biological activity of the hybrids was influenced both by the nature of the carbohydrate (glucose vs. galactose) appended on ruthenium complex and the type/length of the linker between the two units. 23 and 26, two galactose-based diruthenium conjugates, exhibited low IC50 values and reduced effect on HFF viability when applied at 2.5 µM (23: IC50 = 0.032 µM/HFF viability 92% and 26: IC50 = 0.153 µM/HFF viability 97%). Remarkably, compounds 23 and 26 performed significantly better than the corresponding carbohydrate non-modified diruthenium complexes, showing that this type of conjugates are a promising approach for obtaining new antiparasitic compounds with reduced toxicity.

Cisplatin conjugation with an exopolysaccharide extracted from Lactobacillus gasseri potentiates its efficacy and attenuates its toxicity

The development of newer cisplatin analogs is constantly being investigated owing to its low solubility, poor pharmacokinetics, and dose-related toxicity. In order to address the limitations of current cisplatin therapy, the present study was undertaken. Cisplatin conjugation with an exopolysaccharide extracted from Lactobacillus gasseri (LG-EPS) showed remarkably enhanced and selective anticancer activity by targeting tumor cells overexpressing glucose transporter 1 (GLUT1). The EPS-cisplatin complex exhibited a 600-fold increase in aqueous solubility with a better pharmacokinetic profile (longer half-life) in comparison to cisplatin. Cell viability assay and western blotting demonstrated a strong correlation between the cytotoxicity profile and GLUT1 expressions in different cell lines. The concentration of DNA-bound platinum was also found to be significantly higher in EPS-cisplatin-treated cells. Quercetin, a competitive inhibitor of GLUTs, was shown to prevent this selective uptake of EPS-cisplatin complex. Surprisingly, EPS-cisplatin complex showed an exceptionally safer profile (4 times the maximum tolerated dose of cisplatin) in the acute toxicity study and was also more efficacious against the xenograft mice model. The study suggests that this green glycoconjugation can be an effective and safer strategy to broaden the therapeutic potential of anti-cancer drugs in general and cisplatin in particular.

Discovery of highly potent and selective 7-ethyl-10-hydroxycamptothecin-glucose conjugates as potential anti-colorectal cancer agents

7-Ethyl-10-hydroxycamptothecin (SN38), a highly potent metabolite of irinotecan, has an anticancer efficacy 100-1000 folds more than irinotecan in vitro. However, the clinical application of SN38 has been limited due to the very narrow therapeutic window and poor water solubility. Herein, we report the SN38-glucose conjugates (Glu-SN38) that can target cancer cells due to their selective uptake via glucose transporters, which are overexpressed in most cancers. The in vitro antiproliferative activities against human cancer cell lines and normal cells of Glu-SN38 were investigated. One of the conjugates named 5b showed high potency and selectivity against human colorectal cancer cell line HCT116. Furthermore, 5b remarkably inhibited the growth of HCT116 in vivo. These results suggested that 5b could be a promising drug candidate for treating colorectal cancer.

Antitumor effects of new glycoconjugated PtII agents dual-targeting GLUT1 and Pgp proteins

A novel and highly efficient dual-targeting Pt^II system was designed to improve the drug delivery capacity and selectivity in cancer treatment. The dual-targeting monofunctional Pt^II complexes (1-8) having glycosylated pendants as tridentated ligand were achieved by introducing glycosylation modification in the thioaminocarbazone compounds with potential lysosomal targeting ability. The structures and stability of 1-8 were further established by various techniques. Molecular docking studies showed that 2 was efficiently docked into glucose transporters protein 1 (GLUT1) and P-glycoprotein (Pgp) proteins with the optimal CDocker-interaction-energy of -64.84 and -48.85 kcal mol^-1. Complex 2 with higher protein binding capacity demonstrated significant and broad-spectrum antitumor efficacy in vitro, even exhibiting a half maximal inhibitory concentration (IC₅₀) value (∼10 μM) than cisplatin (∼17 μM) against human lung adenocarcinoma cells (A549). The inhibitor experiment revealed GLUT-mediated uptake of 2, and the subcellular localization experiment in A549 also proved that 2 could be localized in the lysosome, thereby causing cell apoptosis. Moreover, cellular thermal shift assay (CETSA) confirmed the binding of 2 with the target proteins of GLUT1 and Pgp. The above results indicated that 2 represents a potential anticancer candidate with dual-targeting functions.

Glycosylation and its research progress in endometrial cancer

Endometrial cancer (EC) is one of the most common tumors in the female reproductive system, which seriously threatens women's health, particularly in developed countries. 13% of the patients with EC have a poor prognosis due to recurrence and metastasis. Therefore, identifying good predictive biomarkers and therapeutic targets is critical to enable the early detection of metastasis and improve the prognosis. For decades, extensive studies had focused on glycans and glycoproteins in the progression of cancer. The types of glycans that are covalently attached to the polypeptide backbone, usually via nitrogen or oxygen linkages, are known as N‑glycans or O‑glycans, respectively. The degree of protein glycosylation and the aberrant changes in the carbohydrate structures have been implicated in the extent of tumorigenesis and reported to play a critical role in regulating tumor invasion, metabolism, and immunity. This review summarizes the essential biological role of glycosylation in EC, with a focus on the recent advances in glycomics and glycosylation markers, highlighting their implications in the diagnosis and treatment of EC.

Bioorthogonal Light-Up Fluorescent Probe Enables Wash-Free Real-Time Dynamic Monitoring of Cellular Glucose Uptake

As a significant energy source for living systems, the aberrant cellular glucose uptake is seriously implicated in numerous metabolic diseases. Unfortunately, current shortage of robust tools leaves the limitation to understand its precise biology. Herein we presented a bioorthogonal light-up fluorescent probe consist of two reagents, Glu-HT-Me+AzGlu2, for rapidly responsive (within 25 min), highly specific and sensitive (20-folds enhancement) detection of live-cell glucose uptake based on arylphosphine-induced a-PET effect and Staudinger ligation. Especially, taking the advantage of wash-free characteristic, the probe displayed the real-time dynamic monitoring of cellular glucose uptake. Furthermore, it was successfully capable of not only differentiating cancer cells from normal cells, but also allowing evaluation of anticancer/glycolysis/transport mediated glucose flux. Importantly, it was employed to monitor the fluctuations of glucose uptake in a doxycycline-inducible K-ras^G12 V expression oncogenic cell system, implying its potential as a valuable tool to explore glucose uptake biology.

Design, synthesis of novel triptolide-glucose conjugates targeting glucose Transporter-1 and their selective antitumor effect

Six positional isomers of triptolide-glucose conjugates (TG1α, TG1β, TG2, TG3, TG4 and TG6) were designed and synthesized. These conjugates exhibited better water solubility, and had selective cytotoxicity between tumor cells with high expression of glucose transport-1 (Glut-1) and non-tumor cells with low expression of Glut-1, in which TG2 formed by triptolide (TPL) and d-glucose C2-OH had the strongest cytotoxicity to tumor cells and lowest toxicity in non-tumor cells, therefore the highest relative therapeutic index, which was 5.7 times that of triptolide and consequent the most powerful selective antitumor activity in vitro. The cytotoxicity of TG2 was highly correlated with Glut-1 function. As a prodrug of triptolide, TG2 could promote RNA Pol II degradation and induce apoptosis as TPL does. TG2 had a stronger dose-dependent antitumor effect in vivo than TPL and no adverse reaction occurred when its tumor inhibition was higher than 90%, which was associated with its selective distribution in tumor tissues. TG2 could be used as a promising drug candidate for the treatment of solid tumors with high expression of Glut-1, which is worthy of further study.

4'-Nitrobiphenyl thioglucoside as the Smallest, fluorescent photosensitizer with cancer targeting ligand

We have previously developed a glucose-linked biphenyl photosensitizer that can pass through glucose transporters, aiming for cancer-selective photodynamic therapy (PDT). Its small size (MW: 435) will allow oral administration and a fast clearance avoiding photosensitivity. However, its fluorescence efficiency was quite low, causing difficulty in monitoring cellular uptake. We thus synthesized a series of monosaccharide-linked biphenyl derivatives with a sulfur atom replacing an oxygen atom, in search of a photosensitizer with a brighter fluorescence. Among them, 4'-nitrobiphenyl thioglucoside showed a fluorescence emission extending to near infra-red region with a strength three times greater than that of the previous compound. This compound was found to have a higher ¹O₂-producing efficiency (Φ_Δ: 0.75) than the previous compound (Φ_Δ: 0.65). The thioglucoside indicated a significant photodamaging effect (IC₅₀: 250 μM) against cancer cells. Although the galactose and mannose analogs exerted similar photodamaging effects, they were moderately toxic in the dark at a concentration of 300 μM. The thioglucoside and thiomannoside were at least partially uptaken through glucose transporters as demonstrated by inhibition with cytochalasin B, whereas no inhibition was observed for the galactoside. The behavior of d-glucose toward the cellular uptakes of these photosensitizers was bipolar: inhibitory at a low concentration and recovery or acceleratory at a higher concentration. These results indicate that 4'-nitrobiphenyl thioglucoside is the smallest (MW: 393) cancer-targeting photosensitizer with a trackable fluorescence property.

Wirelessly Activated Nanotherapeutics for In Vivo Programmable Photodynamic-Chemotherapy of Orthotopic Bladder Cancer

Photochemical internalization (PCI) is a promising intervention using photodynamic therapy (PDT) to enhance the activity of chemotherapeutic drugs. However, current bladder cancer treatments involve high-dose chemotherapy and high-irradiance PDT which cause debilitating side effects. Moreover, low penetration of light and drugs in target tissues and cumbersome light delivery procedures hinder the clinical utility of PDT and chemotherapy combination for PCI. To circumvent these challenges, a photodynamic-chemotherapy approach is developed comprising tumor-targeting glycosylated nanocarriers, coloaded with chlorin e6 (Ce6) and gemcitabine elaidate (GemE), and a miniaturized implantable wirelessly powered light-emitting diode (LED) as a light source. The device successfully delivers four weekly light doses to the bladder while the nanocarrier promoted the specific accumulation of drugs in tumors. This approach facilitates the combination of low-irradiance PDT (1 mW cm-2 ) and low-dose chemotherapy (≈1500× lower than clinical dose) which significantly cures and controls orthotopic disease burden (90% treated vs control, 35%) in mice, demonstrating a potential new bladder cancer treatment option.

Dual-imaging magnetic nanocatalysis based on Fenton-like reaction for tumor therapy

Sequential nano-catalytic therapy has emerged as a novel therapeutic modality for cancer treatment as it utilizes the unique tumor microenvironment for selective tumor treatment. This study reports a magnetic nanoparticle to achieve Fenton-like reaction and dual-imaging guidance/monitoring. Natural glucose oxidase (GOx) and superparamagnetic Fe₃O₄ nanoparticles have been integrated into poly(lactic-co-glycolic acid) (PLGA) to fabricate a sequential nanocatalyst (designated as GOx@PLGA-Fe₃O₄). This nanocatalyst can functionally deplete glucose in tumor tissues, producing a considerable amount of highly cytotoxic hydroxyl radicals via the sequential Fenton-like reaction, and meanwhile maximizing the potential imaging capability as a contrast agent for magnetic resonance imaging and photoacoustic imaging. By ribonucleic acid sequencing (RNA-seq) technology, GOx@PLGA-Fe₃O₄ nanoparticles are demonstrated to induce tumor cell death by inhibiting multiple gene regulation pathways involving tumor growth and recurrence. Therefore, this finding provides a novel strategy to achieve promising therapeutic efficacy by the rational design of multifunctional nanoparticles with various features, including magnetic targeting, sequential nano-catalytic therapy, and dual-imaging guidance/monitoring.

Selective Targeting of Cancer Cells by Copper Ionophores: An Overview

Conventional cancer therapies suffer from severe off-target effects because most of them target critical facets of cells that are generally shared by all rapidly proliferating cells. The development of new therapeutic agents should aim to increase selectivity and therefore reduce side effects. In addition, these agents should overcome cancer cell resistance and target cancer stem cells. Some copper ionophores have shown promise in this direction thanks to an intrinsic selectivity in preferentially inducing cuproptosis of cancer cells compared to normal cells. Here, Cu ionophores are discussed with a focus on selectivity towards cancer cells and on the mechanisms responsible for this selectivity. The proposed strategies, to further improve the targeting of cancer cells by copper ionophores, are also reported.

Photocatalytic glucose-appended bio-compatible Ir(III) anticancer complexes

Rationally-designed glucose-appended Ir(III) photo-catalysts ([Ir(N,C)2(N,N-Glc)]+, Ir1-Ir3) show visible light-induced catalytic NAD(P)H oxidation in aqueous solution. Highly in-vivo biocompatible complex, Ir3, shows lysosome and mitochondria targeting necro-apoptotic photo-cytotoxicity against various cancer...

Ultrasmall Luminescent Metal Nanoparticles: Surface Engineering Strategies for Biological Targeting and Imaging

In the past decade, ultrasmall luminescent metal nanoparticles (ULMNPs, d < 3 nm) have achieved rapid progress in addressing many challenges in the healthcare field because of their excellent physicochemical properties and biological behaviors. With the sharp shrinking size of large plasmonic metal nanoparticles (PMNPs), the contributions from the surface characteristics increase significantly, which brings both opportunities and challenges in the application-driven surface engineering of ULMNPs toward advanced biological applications. Here, the systematic advancements in the biological applications of ULMNPs from bioimaging to theranostics are summarized with emphasis on the versatile surface engineering strategies in the regulation of biological targeting and imaging performance. The efforts in the surface functionalization strategies of ULMNPs for enhanced disease targeting abilities are first discussed. Thereafter, self-assembly strategies of ULMNPs for fabricating multifunctional nanostructures for multimodal imaging and nanomedicine are discussed. Further, surface engineering strategies of ratiometric ULMNPs to enhance the imaging stability to address the imaging challenges in complicated bioenvironments are summarized. Finally, the phototoxicity of ULMNPs and future perspectives are also reviewed, which are expected to provide a fundamental understanding of the physicochemical properties and biological behaviors of ULMNPs to accelerate their future clinical applications in healthcare.

Click Pt(IV)-Carbohydrates Pro-Drugs for Treatment of Osteosarcoma

The selectivity vs. cancer cells has always been a major challenge for chemotherapeutic agents and in particular for cisplatin, one of the most important anticancer drugs for the treatment of several types of tumors. One strategy to overtake this challenge is to modify the coordination sphere of the metallic center with specific vectors whose receptors are overexpressed in the tumoral cell membrane, such as monosaccharides. In this paper, we report the synthesis of four novel glyco-modified Pt(IV) pro-drugs, based on cisplatin scaffold, and their biological activity against osteosarcoma (OS), a malignant tumor affecting in particular adolescents and young adults. The sugar moiety and the Pt scaffold are linked exploiting the Copper Azide Alkyne Cycloaddition (CUAAC) reaction, which has become the flagship of click chemistry due to its versatility and mild conditions. Cytotoxicity and drug uptake on three different OS cell lines as well as CSCs (Cancer Stem Cell) are described.

Glycocalixarene with luminescence for Warburg effect-mediated tumor imaging and targeted drug delivery

Fluorescently labeled calix[4]arene glycoconjugates demonstrate multifunctional potential in both Warburg effect mediated tumor imaging and GLUT1 targeted drug delivery. Nitrobenzoxadiazole and mannose conjugated NBD-Man-CA was found to be selectively recognized by GLUT1 and act as a "molecular carrier" for selective tumor targeting.

Recent Progresses in Conjugation with Bioactive Ligands to Improve the Anticancer Activity of Platinum Compounds

Platinum (Pt) drugs, including cisplatin, are widely used for the treatment of solid tumors. Despite the clinical success, side effects and occurrence of resistance represent major limitations to the use of clinically available Pt drugs. To overcome these problems, a variety of derivatives have been designed and synthetized. Here, we summarize the recent progress in the development of Pt(II) and Pt(IV) complexes with bioactive ligands. The development of Pt(II) and Pt(IV) complexes with targeting molecules, clinically available agents, and other bioactive molecules is an active field of research. Even if none of the reported Pt derivatives has been yet approved for clinical use, many of these compounds exhibit promising anticancer activities with an improved pharmacological profile. Thus, planning hybrid compounds can be considered as a promising approach to improve the available Pt-based anticancer agents and to obtain new molecular tools to deepen the knowledge of cancer progression and drug resistance mechanisms.

Design, physico-chemical characterization and in vitro biological activity of organogold(III) glycoconjugates

To develop new metal-based glycoconjugates as potential anticancer agents, four organometallic gold(iii)-dithiocarbamato glycoconjugates of the type [AuIII(2-Bnpy)(SSC-Inp-GlcN)](PF6) (2-Bnpy: 2-benzylpyridine; Inp: isonipecotic moiety; GlcN: amino-glucose scaffold; Au3-Au6) and the corresponding model non-glycosylated counterparts [AuIII(2-Bnpy)(SSC-Inp-R)](PF6) (R: OEt (Au1), NH2 (Au2)) have been generated and characterized by means of several analytical techniques (elemental analysis, FT-IR, 1H-/13C-NMR, ESI-MS, UV-Vis, X-ray crystallography). Their stability under physiologically-relevant conditions (PBS solution) and n-octanol/PBS distribution coefficient (D7.4) have also been evaluated. Gold(iii) glycoconjugates showed an antiproliferative effect against ovarian carcinoma A2780 cells, with GI50 values in the low micromolar range. Remarkably, their cell growth inhibitory effect increases upon the addition of a glucose transporter 1 (GLUT1) inhibitor, thus ruling out the involvement of GLUT1 in their transport inside the cell. Additional mechanistic studies have been carried out in A2780 cells, supporting the hypothesis of a facilitated diffusion mechanism (possibly mediated by glucose transporters other than GLUT1), and revealing their capability to act as topoisomerase I and II inhibitors and to disrupt mitochondrial membrane integrity, leading to the generation of ROS, thus resulting in the promotion of oxidative stress and, eventually, cell death.

Optical glucose biosensor built-in disposable strips and wearable electronic devices

On-demand screening, real-time monitoring and rapid diagnosis of ubiquitous diseases, such as diabetes, at early stages are indispensable in personalised treatment. Emerging impacts of nano/microscale materials on optical and portable biosensor strips and devices have become increasingly important in the remarkable development of sensitive visualisation (i.e. visible inspection by the human eye) assays, low-cost analyses and personalised home testing of patients with diabetes. With the increasing public attention regarding the self-monitoring of diabetes, the development of visual readout, easy-to-use and wearable biosensors has gained considerable interest. Our comprehensive review bridges the practical assessment gap between optical bio-visualisation assays, disposable test strips, sensor array designs and full integration into flexible skin-based or contact lens devices with the on-site wireless signal transmission of glucose detection in physiological fluids. To date, the fully modulated integration of nano/microscale optical biosensors into wearable electronic devices, such as smartphones, is critical to prolong periods of indoor and outdoor clinical diagnostics. Focus should be given to the improvements of invasive, wireless and portable sensing technologies to improve the applicability and reliability of screen display, continuous monitoring, dynamic data visualisation, online acquisition and self and in-home healthcare management of patients with diabetes.

In Vitro and In Vivo Efficacy of a Novel Glucose-Methotrexate Conjugate in Targeted Cancer Treatment

Methotrexate (MTX) is a commonly used antimetabolite, which inhibits folate and DNA synthesis to be effective in the treatment of various malignancies. However, MTX therapy is hindered by the lack of target tumor selectivity. We have designed, synthesized and evaluated a novel glucose–methotrexate conjugate (GLU–MTX) both in vitro and in vivo, in which a cleavable linkage allows intracellular MTX release after selective uptake through glucose transporter−1 (GLUT1). GLU–MTX inhibited the growth of colorectal (DLD-1), breast (MCF-7) and lung (A427) adenocarcinomas, squamous cell carcinoma (SCC-25), osteosarcoma (MG63) cell lines, but not in WI-38 healthy fibroblasts. In tumor cells, GLU–MTX uptake increased 17-fold compared to unconjugated MTX. 4,6-O-ethylidene-α-D-glucose (EDG), a GLUT1 inhibitor, significantly interfered with GLU–MTX induced growth inhibition, suggesting a glucose-mediated drug uptake. Glu-MTX also caused significant tumor growth delay in vivo in breast cancer-bearing mice. These results show that our GLUT-MTX conjugate can be selectively uptake by a range of tumor cells to cause their significant growth inhibition in vitro, which was also confirmed in a breast cancer model in vivo. GLUT1 inhibitor EDG interfered with these effects verifying the selective drug uptake. Accordingly, GLU–MTX offers a considerable tumor selectivity and may offer cancer growth inhibition at reduced toxicity.

Disruption of the Microtubule Network and Inhibition of VEGFR2 Phosphorylation by Cytotoxic N,O-Coordinated Pt(II) and Ru(II) Complexes of Trimethoxy Aniline-Based Schiff Bases

Platinum-based complexes are one of the most successful chemotherapeutic agents having a significant ground in cancer chemotherapy despite their side effects. During the past few decades, Ru(II) complexes have been emerging as efficient alternatives owing to their promising activities against platinum-resistant cancer. The pathway of action, lipophilicity, and cytotoxicity of a Pt or Ru complex may be tuned by varying the attached ligands, the coordination mode, and the leaving group. In this work, we report a family of Pt(II) and Ru(II) complexes (1-5) of three N,O and N,N donor-based trimethoxyanilines containing Schiff bases with the general formula [Pt^II(L)(DMSO)Cl], [Ru^II(L)(p-cymene)Cl], [Ru^II(L)(p-cymene)Cl]⁺, and [Pt^II(L)Cl₂]. All of the complexes are characterized by different analytical techniques. ¹H NMR and electrospray ionization mass spectrometry (ESI-MS) data suggest that the N,O-coordinated Pt(II) complexes undergo slower aquation compared to the Ru(II) analogues. The change of the coordination mode to N,N causes the Ru complexes to be more inert to aquation. The N,O-coordinating complexes show superiority over N,N-coordinating complexes by displaying excellent in vitro antiproliferative activity against different aggressive cancer cells, viz., triple-negative human metastatic breast adenocarcinoma MDA-MB-231, human pancreatic carcinoma MIA PaCa-2, and hepatocellular carcinoma Hep G2. In vitro cytotoxicity studies suggest that Pt(II) complexes are more effective than their corresponding Ru(II) analogues, and the most cytotoxic complex 3 is 10-15 times more toxic than the clinical drugs cisplatin and oxaliplatin against MDA-MB-231 cells. Cellular studies show that all of the N,O-coordinated complexes (1-3) initiate disruption of the microtubule network in MDA-MB-231 cells in a dose-dependent manner within 6 h of incubation and finally lead to the arrest of the cell cycle in the G2/M phase and render apoptotic cell death. The disruption of the microtubule network affects the agility of the cytoskeleton rendering inhibition of tyrosine phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2), a key step in angiogenesis. Complexes 1 and 2 inhibit VEGFR2 phosphorylation in a dose-dependent fashion. Among the Pt(II) and Ru(II) complexes, the former displays higher cytotoxicity, a stronger effect on the cytoskeleton, better VEGFR2 inhibition, and strong interaction with the model nucleobase 9-ethylguanine (9-EtG).

Direct and simultaneous recognition of the positional isomers of aminobenzenesulfonic acid by TIMS-TOF-MS

Positional isomer recognition is a challenging scientific issue. Fast and accurate detection of isomers is required for understanding their chemical properties. Here, we describe a method for simultaneous recognition of three positional isomers of 2-aminobenzenesulfonic acid (2-ABSA), 3-ABSA, and 4-ABSA using trapped ion mobility spectroscopy-time-of-flight mass spectrometry (TIMS-TOF-MS). The three ABSA positional isomers were recognized by measuring the different ion mobility of the ternary complexes of [β-cyclodextrin (CD)+ABSA + Li]⁺ or [λ-CD + ABSA + Na]⁺, because their different collision cross-sections or different spatial conformations. The collision-induced dissociation mechanism of the different complexes of [β-CD + ABSA + Li]⁺ and [λ-CD + ABSA + Na]⁺ using tandem mass spectrometry exhibited the same dissociation process with slightly different dissociation energies, which the smaller cross-section requires higher collision energy that means the smaller complex with tighter and more stable conformation than a larger complex for the ABSA complexes. In addition, relative quantification of the ABSA isomers was studied by measuring any two of the three ABSA isomer complexes at different molar ratio of 10:1 to 1:10 in the μM range, good linearity (R² > 0.99) with precision between 2.14% and 2.58%, and accuracy ≥ 97.1% were obtained. The method for fast determination and recognition of ABSA positional isomers by combination with CD and alkali metal ions possesses the advantages of being simple, direct, rapid, sensitive, cost-effective, and needs no chemical derivatives or chromatographic separation before analysis. Therefore, the proposed method would be a powerful tool for the analysis of ABSA isomers or even other positional isomers.

Glycoconjugates for glucose transporter-mediated cancer-specific targeting and treatment

First observed in 1920s, the Warburg effects have inspired scientists to harness the unique glucose metabolism of cancer cells for targeted therapy for a century. Carbohydrate-drug conjugates are explicitly designed for selective uptake by cancer cells overexpressing glucose transporters. We summarize the progress in developing glycoconjugates for cancer-specific targeting and treatment over the past decade (2010-2020) and point to some future directions in this field.

Altered glycosylation in cancer: A promising target for biomarkers and therapeutics

Glycosylation is a well-regulated cell and microenvironment specific post-translational modification. Several glycosyltransferases and glycosidases orchestrate the addition of defined glycan structures on the proteins and lipids. Recent advances and systemic approaches in glycomics have significantly contributed to a better understanding of instrumental roles of glycans in health and diseases. Emerging research evidence recognized aberrantly glycosylated proteins as the modulators of the malignant phenotype of cancer cells. The Cancer Genome Atlas has identified alterations in the expressions of glycosylation-specific genes that are correlated with cancer progression. However, the mechanistic basis remains poorly explored. Recent researches have shown that specific changes in the glycan structures are associated with 'stemness' and epithelial-to-mesenchymal transition of cancer cells. Moreover, epigenetic changes in the glycosylation pattern make the tumor cells capable of escaping immunosurveillance mechanisms. The deciphering roles of glycans in cancer emphasize that glycans can serve as a source for the development of novel clinical biomarkers. The ability of glycans in intervening various stages of tumor progression and the biosynthetic pathways involved in glycan structures constitute a promising target for cancer therapy. Advances in the knowledge of innovative strategies for identifying the mechanisms of glycan-binding proteins are hoped to hold great potential in cancer therapy. This review discusses the fundamental role of glycans in regulating tumorigenesis and tumor progression and provides insights into the influence of glycans in the current tactics of targeted therapies in the clinical setting.

Anticancer therapeutics: a brief account on wide refinements

The flustering rise in cancer incidence along with treatment anomalies has made cancer the second leading cause of death globally. The total annual economic impact of cancer is pronounced and is increasing. Besides the lack of proper curative therapy, treatment associated adverse effects, drug resistance, and tumor relapse are the instigations behind increased morbidity and mortality. Meanwhile, the survival rate has inclined impressively. In the last few decades, cancer treatment has undergone wide refinements aiming towards cancer prevention, complete tumor regression, subsiding treatment adverse effects, improving patient's life standard and avoiding tumor relapse. Chemotherapy has been successfully extended towards natural, cheaper and bioactive anti-inflammatory agents manifesting potent anticancer activity. Antibody-based cancer therapy has become well established as a vital and effective strategy for treating hematological malignancies as well as solid tumors. Individualized immunotherapy is becoming the forefront of cancer treatment enabling personalized, precise and patient's cancer mutanome specific adjustable regimen. The emergence of anti-neoangiogenesis and cancer stem cell targeting techniques have dropped cancer recurrence significantly. Advancements in hyperthermia and photodynamic therapies along with improvements in cancer vaccination have declined death rate and amplified survival rate convincingly.

Glycoconjugated Metal Complexes as Cancer Diagnostic and Therapeutic Agents

The possibility of selectively delivering metal complexes to a defined cohort of cells on the basis of their metabolic features is a highly challenging goal, which may be extremely useful for a series of purposes, including diagnosis and therapy of pathological states, such as cancer. Tumor cells display augmented requests for carbohydrates and, in particular, for glucose in order to sustain their high proliferation rate, which causes an increased glycolytic process (Warburg effect). Since several metal complexes display diagnostic and/or therapeutic properties, their conjugation to carbohydrate portions often induce their preferential accumulation in cancer cells, similarly to what is observed with fluorodeoxyglucose (FDG). In this review we have considered the latest developments of glycoconjugates containing metal complexes in their structures. These compounds are classified as diagnostic or therapeutic agents and are further systematically discussed on the basis of the metal atom they contain. Several diagnostic techniques are possible with these probes, since, depending on the metal species included in their structures, they may be employed in nuclear medicine (PET, SPECT), magnetic resonance imaging, luminescence and phosphorescence. At the same time, the lack of selective cytotoxicity displayed by several metal-based chemotherapeutic agents, may also be solved by the conjugation of these agents to carbohydrate portions. Overall, data so far available reveal the great potential of this chemical class in the early detection and in the cure of severe neoplastic diseases, which still needs to be fully explored in the clinic.

Role of Glucose Transporters in Drug Membrane Transport

BACKGROUND

Glucose is the main energy component of cellular activities. However, as a polar molecule, glucose cannot freely pass through the phospholipid bilayer structure of the cell membrane. Thus, glucose must rely on specific transporters in the membrane. Drugs with a similar chemical structure to glucose may also be transported through this pathway.

METHODS

This review describes the structure, distribution, action mechanism and influencing factors of glucose transporters and introduces the natural drugs mediated by these transporters and drug design strategies on the basis of this pathway.

RESULTS

The glucose transporters involved in glucose transport are of two major types, namely, Na+-dependent and Na+-independent transporters. Glucose transporters can help some glycoside drugs cross the biological membrane. The transmembrane potential is influenced by the chemical structure of drugs. Glucose can be used to modify drugs and improve their ability to cross biological barriers.

CONCLUSION

The membrane transport mechanism of some glycoside drugs may be related to glucose transporters. Glucose modification may improve the oral bioavailability of drugs or achieve targeted drug delivery.

Dually Enzyme- and Acid-Triggered Self-Immolative Ketal Glycoside Nanoparticles for Effective Cancer Prodrug Monotherapy

The use of glycoside prodrugs is a promising strategy for developing new targeted medicines for chemotherapy. However, the in vivo utility of such prodrugs is hindered by insufficient activation and the lack of convenient synthetic methods. We have developed an innovative strategy for synthesizing ketal glycoside prodrugs that are unique in being activated by a dual enzyme- and acid-triggered self-immolative mechanism. Amphiphilic glucosyl acetone-based ketal-linked etoposide glycoside prodrug isomers were synthesized and fabricated into excipient-free nanoparticles for effective cancer prodrug monotherapy. Hydrolysis of the glycosidic linkage or the ketal linkage triggered hydrolysis of the other linkage, which resulted in spontaneous self-immolative hydrolysis of the prodrugs. Nanoparticles of the prodrug isomer that was the most labile in a lysosome-mimicking environment displayed high intratumoral accumulation and strong antitumor activity in an A549 xenograft mouse model. Our strategy may be useful for the development of stimulus-responsive self-immolative prodrugs and their nanomedicines.

Reversing Reactivity: Stereoselective Desulfurative 1,2-trans-O-Glycosylation of Anomeric Thiosugars with Carboxylic Acids under Copper or Cobalt Catalysis

We have discovered a new mode of reactivity of 1-thiosugars in the presence of Cu(II) or Co(II) for a stereoselective O-glycosylation reaction. The process involves the use of a catalytic amount of Cu(acac)₂ or Co(acac)₂ and Ag₂CO₃ as an oxidant in α,α,α-trifluorotoluene. Moreover, this protocol turned out to have a broad scope, allowing the preparation of a wide range of complex substituted O-glycoside esters in good to excellent yields with an exclusive 1,2-trans-selectivity. The late-stage modification of pharmaceuticals by this method was also demonstrated. To obtain a closer insight into the reaction mechanism, cyclic voltammetry was performed.

'Prodrug-Like' Acetylmannosamine Modified Liposomes Loaded With Arsenic Trioxide for the Treatment of Orthotopic Glioma in Mice

Glioma is one of the fatal intracranial cancers that is a huge challenge to decrease the death rate currently. The deep penetration and high accumulation of therapeutic inorganic ions into the tumor site are extremely impeded due to the existence of physiological barriers, which limits to widen the indication of some drugs such as arsenic trioxide. The previous data have confirmed that the mannose substrate (MAN) without acetyl groups facilitates vesicles to go into the brain. Given that deacetylation of Ac₄MAN groups on the surface of liposomes under the enzyme incubation occurred, namely 'prodrug-like' features of vesicles, the liposomes could more easily penetrate the BBB, target the glioma site, release arsenic trioxide, and inhibit the growth of glioma cells in the brain. Besides, the possibility of Ac₄MAN binding to Gluts could be reduced due to the steric hindrance of acetyl groups, decreasing the off-target effects of vesicles. Here, we developed 'prodrug-like' arsenic trioxide (As₂O₃, ATO)-loaded liposomes inserted with distearoyl phospho-ethanolamine-polyethylene glycol-1000-p-carboxylpheny-α-d-acetylmannosamine (DSPE-PEG-1000-Ac₄MAN), which was named Ac₄MAN-ATO-LIP. Cytotoxic experiments of liposomes indicated that the toxicity of Ac₄MAN-ATO-LIP was lower than that of free ATO but stronger than that of ATO-LIP (without insertion of DSPE-PEG-1000-Ac₄MAN). The uptake of vesicles by U87 glioma cells displayed that the cellular uptake of Ac₄MAN-Rho-LIP (labeled by rhodamine) was remarkably improved, compared with Rho-LIP. The in vivo biodistribution results showed the superiority of Ac₄MAN-Rho-LIP in enhanced intracranial accumulation. Furthermore, the treatment of orthotopic glioma in Balb/c nude mice with Ac₄MAN-ATO-LIP elongated the survival time of the animals than that with physiological saline, free ATO, or ATO-LIP, respectively. All the results suggested that the Ac₄MAN-ATO-LIP had stronger anti-glioma effects as well as lower toxicities, and may be a promising approach for the treatment of brain cancer.

Boosting two-photon photodynamic therapy with mitochondria-targeting ruthenium-glucose conjugates

Herein, we present a series of dual-targeted ruthenium-glucose conjugates that can function as two-photon absorption (TPA) PDT agents to effectively destroy tumors by preferentially targeting both tumor cells and mitochondria. The in vivo experiments revealed an excellent tumor inhibitory efficiency of the dual-targeted TPA PSs.