Interactions of bismuth complexes with metallothionein(II)

A glutathione-activated bismuth-gallic acid metal-organic framework nano-prodrug for enhanced sonodynamic therapy of breast tumor

Sonodynamic therapy is a promising, noninvasive, and precise tumor treatment that leverages sonosensitizers to generate cytotoxic reactive oxygen species during ultrasound stimulation. Gallic acid (GA), a natural polyphenol, possesses certain anti-tumor properties, but exhibits significant toxicity toward normal cells, limiting its application in cancer treatment. To overcome this issue, we synthesized a bismuth-gallic acid (BGA), coordinated metal-organic framework (MOF) nano-prodrug. Upon encountering glutathione (GSH), BGA gradually dissociated and depleted GSH, releasing GA, which had anti-tumor effects. As an MOF with semiconductor properties, BGA primarily produced superoxide anion radical upon ultrasound excitation. After the release of GA, GA generated superoxide anion radical and further produced high toxic singlet oxygen under ultrasound stimulation, while further oxidizing and consuming GSH, enhancing sonocatalytic performance. Additionally, the released GA induced cell cycle arrest, ultimately leading to apoptosis. Our results revealed that BGA, as a GSH-activated, metal-polyphenol MOF nano-prodrug, showed potential for use in breast tumor sonodynamic therapy, providing a novel strategy for precise tumor treatment.

Bi(III) Binding Stoichiometry and Domain-Specificity Differences Between Apo and Zn(II)-bound Human Metallothionein 1a

Bismuth is a xenobiotic metal with a high affinity to sulfur that is used in a variety of therapeutic applications. Bi(III) induces the cysteine-rich metallothionein (MT), a protein known to form two-domain cluster structures with certain metals such as Zn(II), Cd(II), or Cu(I). The binding of Bi(III) to MTs has been previously studied, but there are conflicting reports on the stoichiometry and binding pathway, which appear to be highly dependent on pH and initial metal-loading status of the MT. Additionally, domain specificity has not been thoroughly investigated. In this paper, ESI-MS was used to determine the binding constants of [Bi(EDTA)]- binding to apo-MT1a and its individual αMT fragment. The results were compared to previous experiments using βMT1a and βαMT3. Domain specificity was investigated using proteolysis methods and the initial cooperatively formed Bi2MT was found to bind to cysteines that spanned across the traditional metal binding domain regions. Titrations of [Bi(EDTA)]- into Zn7MT were performed and were found to result in a maximum stoichiometry of Bi7MT, contrasting the Bi6MT formed when [Bi(EDTA)]- was added to apo-MT. These results show that the initial structure of the apo-MT determines the stoichiometry of new incoming metals and explains the previously observed differences in stoichiometry.

Development of Pan-Anti-SARS-CoV-2 Agents through Allosteric Inhibition of nsp14/nsp10 Complex

SARS-CoV-2 nsp14 functions both as an exoribonuclease (ExoN) together with its critical cofactor nsp10 and as an S-adenosyl methionine-dependent (guanine-N7) methyltransferase (MTase), which makes it an attractive target for the development of pan-anti-SARS-CoV-2 drugs. Herein, we screened a panel of compounds (and drugs) and found that certain compounds, especially Bi(III)-based compounds, could allosterically inhibit both MTase and ExoN activities of nsp14 potently. We further demonstrated that Bi(III) binds to both nsp14 and nsp10, resulting in the release of Zn(II) ions from the enzymes as well as alternation of protein quaternary structures. The in vitro activities of the compounds were also validated in SARS-CoV-2-infected mammalian cells. Importantly, we showed that nsp14 serves as an authentic target of Bi(III)-based antivirals in SARS-CoV-2-infected mammalian cells by quantification of both the protein and inhibitor. This study highlights the importance of nsp14/nsp10 as a potential target for the development of pan-antivirals against SARS-CoV-2 infection.

Xenobiotic Bi3+ Coordination by Cysteine-Rich Metallothionein-3 Reveals a Cooperatively Formed Thiolate-Sharing Bi2S5 Cluster

The field of designing artificial metalloproteins has yet to effectively tackle the incorporation of multimetal clusters, which is a key component of natural metalloproteins, such as metallothioneins (MTs) and calmodulin. MT is a physiological, essential, cysteine-rich metalloprotein that binds to a variety of metals but is only known to form metal-thiolate clusters with Cd2+, Zn2+, and Cu+. Bismuth is a xenobiotic metal and a component of metallodrugs used to treat gastric ulcers and cancer, as well as an emerging metal used in industrial practices. Electrospray ionization mass spectrometry, UV-visible spectroscopy, and extended X-ray absorption fine structure spectroscopy were used to probe the Bi3+ binding site structures in apo-MT3 (brain-located MT) at pH 7.4 and 2 and provide the complete set of binding affinities. We discovered the highly cooperative formation of a novel Bi3+ species, Bi2MT3, under physiological conditions, where each Bi3+ ion is coordinated by three cysteinyl thiolates, with one of the thiolates bridging between the two Bi3+ ions. This cluster structure was associated with a strong visible region absorption band, which was disrupted by the addition of Zn2+ and reversibly disrupted by acidification and increased temperature. This is the first reported presence of bridging cysteines for a xenobiotic metal in MT3 and the Bi2MT structure is the first Bi cluster found in a metalloprotein.

Biological Activities of Bismuth Compounds: An Overview of the New Findings and the Old Challenges Not Yet Overcome

Bismuth-based drugs have been used primarily to treat ulcers caused by Helicobacter pylori and other gastrointestinal ailments. Combined with antibiotics, these drugs also possess synergistic activity, making them ideal for multiple therapy regimens and overcoming bacterial resistance. Compounds based on bismuth have a low cost, are safe for human use, and some of them are also effective against tumoral cells, leishmaniasis, fungi, and viruses. However, these compounds have limited bioavailability in physiological environments. As a result, there is a growing interest in developing new bismuth compounds and approaches to overcome this challenge. Considering the beneficial properties of bismuth and the importance of discovering new drugs, this review focused on the last decade's updates involving bismuth compounds, especially those with potent activity and low toxicity, desirable characteristics for developing new drugs. In addition, bismuth-based compounds with dual activity were also highlighted, as well as their modes of action and structure-activity relationship, among other relevant discoveries. In this way, we hope this review provides a fertile ground for rationalizing new bismuth-based drugs.

Exploring the Inhibitory Effect of AgBiS2 Nanoparticles on Influenza Viruses

Influenza viruses are respiratory pathogens that are major threats to human health. Due to the emergence of drug-resistant strains, the use of traditional anti-influenza drugs has been hindered. Therefore, the development of new antiviral drugs is critical. In this article, AgBiS₂ nanoparticles were synthesized at room temperature, using the bimetallic properties of the material itself to explore its inhibitory effect on the influenza virus. By comparing the synthesized Bi₂S₃ and Ag₂S nanoparticles, it is found that after adding the silver element, the synthesized AgBiS₂ nanoparticles have a significantly better inhibitory effect on influenza virus infection than Bi₂S₃ and Ag₂S nanoparticles. Recent studies have shown that the inhibitory effect of AgBiS₂ nanoparticles on the influenza virus mainly occurs in the stages of influenza virus-cell internalization and intracellular replication. In addition, it is found that AgBiS₂ nanoparticles also have prominent antiviral properties against α and β coronaviruses, indicating that AgBiS₂ nanoparticles have significant potential in inhibiting viral activity.

Coronaviruses SARS-CoV, MERS-CoV, and SARS-CoV-2 helicase inhibitors: A systematic review of in vitro studies

Introduction

The recent outbreak of SARS-CoV-2 significantly increased the need to find inhibitors that target the essential enzymes for virus replication in the host cells. This systematic review was conducted to identify potential inhibitors of SARS-CoV, MERS-CoV, and SARS-CoV-2 helicases that have been tested by in vitro methods. The inhibition mechanisms of these compounds were discussed in this review, in addition to their cytotoxic and viral infection protection properties.

Methods

The databases PUBMED/MEDLINE, EMBASE, SCOPUS, and Web of Science were searched using different combinations of the keywords "helicase", "nsp13", "inhibitors", "coronaviridae", "coronaviruses", "virus replication", "replication", and "antagonists and inhibitors".

Results

By the end of this search, a total of 6854 articles had been identified. Thirty-one articles were included in this review. These studies reported the inhibitory effects of 309 compounds on SARS-CoV, MERS-CoV, and SARS-CoV-2 helicase activities measured by in vitro methods. Helicase inhibitors were categorized according to the type of coronavirus and the type of tested enzymatic activity, nature, approval, inhibition level, cytotoxicity, and viral infection protection effects. These inhibitors are classified according to the site of their interaction with the coronavirus helicases into four types: zinc-binding site inhibitors, nucleic acid binding site inhibitors, nucleotide-binding site inhibitors, and inhibitors with no clear interaction site.

Conclusion

Evidence from in vitro studies suggests that helicase inhibitors have a high potential as antiviral agents. Several helicase inhibitors tested in vitro showed good antiviral activities while maintaining moderate cytotoxicity. These inhibitors should be clinically investigated to determine their efficiency in treating different coronavirus infections, particularly COVID-19.

Metallo-antiviral aspirants: Answer to the upcoming virusoutbreak

In light of the current SARS-CoV-2 outbreak, about one million research papers (articles, reviews, communications, etc.) were published in the last one and a half years. It was also noticed that in the past few years; infectious diseases, mainly those of viral origin, burdened the public health systems worldwide. The current wave of the Covid-19 pandemic has unmasked critical demand for compounds that can be swiftly mobilized for the treatment of re-emerging or emerging viral infections. With the potential chemical and structural characteristics of organic motifs, the coordination compounds might be a promising and flexible option for drug development. Their therapeutic consequence may be tuned by varying metal nature and its oxidation number, ligands characteristics, and stereochemistry of the species formed. The emerging successes of cisplatin in cancer chemotherapy inspire researchers to make new efforts for studying metallodrugs as antivirals. Metal-based compounds have immense therapeutic potential in terms of structural diversity and possible mechanisms of action; therefore, they might offer an excellent opportunity to achieve new antivirals. This review is an attempt to summarize the current status of antiviral therapies against SARS-CoV-2 from the available literature sources, discuss the specific challenges and solutions in the development of metal-based antivirals, and also talk about the possibility to accelerate discovery efforts in this direction.

Plate-Like Colloidal Metal Nanoparticles

The pseudo-two-dimensional (2D) morphology of plate-like metal nanoparticles makes them one of the most anisotropic, mechanistically understood, and tunable structures available. Although well-known for their superior plasmonic properties, recent progress in the 2D growth of various other materials has led to an increasingly diverse family of plate-like metal nanoparticles, giving rise to numerous appealing properties and applications. In this review, we summarize recent progress on the solution-phase growth of colloidal plate-like metal nanoparticles, including plasmonic and other metals, with an emphasis on mechanistic insights for different synthetic strategies, the crystallographic habits of different metals, and the use of nanoplates as scaffolds for the synthesis of other derivative structures. We additionally highlight representative self-assembly techniques and provide a brief overview on the attractive properties and unique versatility benefiting from the 2D morphology. Finally, we share our opinions on the existing challenges and future perspectives for plate-like metal nanomaterials.

63Cu(I) binding to human kidney 68Zn7-βα MT1A: determination of Cu(I)-thiolate cluster domain specificity from ESI-MS and room temperature phosphorescence spectroscopy

Mammalian metallothioneins (MTs) are important proteins in Zn(II) and Cu(I) homeostasis with the Zn(II) and Cu(I) binding to the 20 cysteines in metal-thiolate clusters. Previous electrospray ionization (ESI) mass spectrometric (MS) analyses of Cu(I) binding to Zn7-MT were complicated by significant overlap of the natural abundance isotopic patterns for Zn(II) and Cu(I) leading to impossibly ambiguous stoichiometries. In this paper, isotopically pure 63Cu(I) and 68Zn(II) allowed determination of the specific stoichiometries in the 68 Zn,63Cu-βα MT1A species formed following the stepwise addition of 63Cu(I) to 68Zn7-βα MT1A. These species were characterized by ESI-MS and room temperature emission spectroscopy. The key species that form and their emission band centres are Zn5Cu5-βα MT1A (λ = 684 nm), Zn4Cu6-βα MT1A (λ = 750 nm), Zn3Cu9-βα MT1A (λ = 750 nm), Zn2Cu10-βα MT1A (λ = 750 nm), and Zn1Cu14-βα MT1A (λ = 634 nm). The specific domain stoichiometry of each species was determined by assessing the species forming following 63Cu(I) addition to the 68Zn3-β MT1A and 68Zn4-α MT1A domain fragments. The domain fragment emission suggests that Zn5Cu5-βα MT1A contains a Zn1Cu5-β cluster and the Zn4Cu6-βα MT1A, Zn3Cu9-βα MT1A, and Zn2Cu10-βα MT1A each contain a Cu6-β cluster. The species forming with >10 mol. eq. of 63Cu(I) in βα-MT1A exhibit emission from the Cu6-β cluster and an α domain cluster. This high emission intensity is seen at the end of the titrations of 68Zn7-βα MT1A and the 68Zn4-α MT1A domain fragment suggesting that the initial presence of the Zn(II) results in clustered Cu(I) binding in the α domain.

Effects of Bismuth Exposure on the Human Kidney-A Systematic Review

The effects of bismuth toxicity on the kidney-the main organ responsible for blood filtration-were systematically reviewed. This review was motivated by availability of several sources of bismuth in contact with humans including environmental, medications, dental materials, and cosmetics, potentially leading to kidney filtration of this chemical. No previous studies have systematically reviewed the literature considering this association. A total of 22 studies with a total of 46 individuals met the inclusion criteria, 19 being case reports with only one patient enrolled. The included studies publication dates ranged from 1961 to 2021 and the countries of publication were the United States of America, United Kingdom, Germany, Turkey, Switzerland, and Canada. Bismuth sources affecting the kidneys were uniquely reported as from medical purposes and mostly associated to overdoses with several symptoms, apparently with dose-dependent consequences. Patient history of renal impairment seemed to affect the outcome of the case. Several therapies were conducted following bismuth intoxication, and few studies performed renal biopsies describing its histological findings. It is crucial to reconsider the nephrotoxicity of bismuth compounds, mainly in patients with previous history of renal impairment.

Biosafe Bi2O2Se ultrathin nanosheet for water disinfection via solar-induced photothermal synergistic effect

Solar-induced sterilization via photothermal synergy has attracted enormous attention due to its zero-energy consumption and the elimination of hazardous chemical disinfectant. Herein, we successfully synthesized a super biosafety Bi₂O₂Se with crossed nanosheet structure (Bi₂O₂Se-CN) for the sterilization of Escherichia coli (E. coli) via solar-induced photothermal synergistic effect. In comparison to bulk Bi₂O₂Se, the lower light reflection and more efficient photogenerated charge carrier separation under visible-infrared light irradiation resulted in the excellent sterilization effect of Bi₂O₂Se-CN, with a sterilization efficiency of 99.9% under the synergistic effect of light and heat. The crossed ultrathin nanosheet structure and suitable band gap width of Bi₂O₂Se-CN are fundamental reasons for its enhanced light absorption and charge carrier separation efficiency. Mechanistic studies showed that Bi₂O₂Se-CN can completely inactivate bacteria via generating a large amount of reactive oxygen species (•O₂^-, •OH, and ¹O₂) to attack the cell membrane, which further resulted in the reduced activity of intracellular enzymes and the leakage of intracellular contents. The biosafety property of Bi₂O₂Se-CN was confirmed by in vivo toxicological evaluation on the mice model. This work provided new ideas for the design of more efficient, energy-saving, biocompatible and environmental friendly solar water purification projects.

Bismuth Reduces Cisplatin-Induced Nephrotoxicity Via Enhancing Glutathione Conjugation and Vesicular Transport

Bismuth drugs have long been used against gastrointestinal diseases, especially the gastric infection of Helicobacter pylori. Cisplatin is a widely used anticancer drug that tends to accumulate at renal proximal tubules and causes severe nephrotoxicity. It was found that bismuth pretreatment reduces cisplatin-induced nephrotoxicity, but the mechanism of action remains unclear. To understand bismuth’s effect on renal tubules, we profiled the proteomic changes in human proximal tubular cells (HK-2) upon bismuth treatment. We found that bismuth induced massive glutathione biosynthesis, glutathione S-transferase activity, and vesicular transportation, which compartmentalizes bismuth to the vesicles and forms bismuth–sulfur nanoparticles. The timing of glutathione induction concurs that of bismuth-induced cisplatin toxicity mitigation in HK-2, and bismuth enhanced cisplatin sequestration to vesicles and incorporation into bismuth–sulfur nanoparticles. Finally, we found that bismuth mitigates the toxicity of general soft metal compounds but not hard metal compounds or oxidants. It suggests that instead of through oxidative stress reduction, bismuth reduces cisplatin-induced toxicity by direct sequestration.

Effects of arsenic on the topology and solubility of promyelocytic leukemia (PML)-nuclear bodies

Promyelocytic leukemia (PML) proteins are involved in the pathogenesis of acute promyelocytic leukemia (APL). Trivalent arsenic (As3+) is known to cure APL by binding to cysteine residues of PML and enhance the degradation of PML-retinoic acid receptor α (RARα), a t(15;17) gene translocation product in APL cells, and restore PML-nuclear bodies (NBs). The size, number, and shape of PML-NBs vary among cell types and during cell division. However, topological changes of PML-NBs in As3+-exposed cells have not been well-documented. We report that As3+-induced solubility shift underlies rapid SUMOylation of PML and late agglomeration of PML-NBs. Most PML-NBs were toroidal and granular dot-like in GFPPML-transduced CHO-K1 and HEK293 cells, respectively. Exposure to As3+ and antimony (Sb3+) greatly reduced the solubility of PML and enhanced SUMOylation within 2 h in the absence of changes in the number and size of PML-NBs. However, the prolonged exposure to As3+ and Sb3+ resulted in agglomeration of PML-NBs. Exposure to bismuth (Bi3+), another Group 15 element, did not induce any of these changes. ML792, a SUMO activation inhibitor, reduced the number of PML-NBs and increased the size of the NBs, but had little effect on the As3+-induced solubility change of PML. These results warrant the importance of As3+- or Sb3+-induced solubility shift of PML for the regulation intranuclear dynamics of PML-NBs.

Bismuth Drugs Reverse Tet(X)-Conferred Tigecycline Resistance in Gram-Negative Bacteria

Antibiotic resistance has caused a serious threat to public health and human safety. Recently, the emergence of novel resistance gene tet(X4) and its variants threatens the clinical utility of tigecycline, one of the last-line antibiotics for multidrug-resistant (MDR) bacterial infections. It is highly promising to develop effective antibiotic adjuvants to restore the clinical efficacy of existing drugs and extend their life spans. Metal compounds, such as silver, have been widely used as potential antimicrobial agents for decades. However, the potentiating effect of metallo-agents on the existing antibiotics is not fully understood. Here, we found that five bismuth drugs, especially bismuth nitrate [Bi(NO₃)₃], commonly used in clinical treatment of stomach-associated diseases, effectively boost the antibacterial activity of tigecycline against tet(X)-positive bacteria by inhibiting the enzymatic activity of Tet(X) protein. Furthermore, the combination of Bi(NO₃)₃ and tigecycline prevents the development of higher-level resistance in Tet(X)-expressing Gram-negative bacteria. Using molecular docking and dynamics simulation assays, we revealed that Bi(NO₃)₃ can competitively bind to the active center of Tet(X4) protein, while the bismuth atom targets the Tet(X4) protein in a noncompetitive manner and changes the structure of the primary binding pocket. These two mechanisms of action both antagonize the enzymatic activity of Tet(X4) resistance protein on tigecycline. Collectively, these findings indicate the high potential of bismuth drugs as novel Tet(X) inhibitors to treat tet(X4)-positive bacteria-associated infections in combination with tigecycline.

IMPORTANCE Recently, high-level tigecycline resistance mediated by tet(X4) and its variants represents a serious challenge for global public health. Antibiotic adjuvant strategy that enhances the activity of the existing antibiotics by using nonantibiotic drugs offers a distinct approach to combat the antibiotic resistance crisis. In this study, we found that bismuth drugs involve bismuth nitrate, a compound previously approved for treatment of stomach-associated diseases, remarkably potentiates tigecycline activity against tet(X)-positive bacteria. Mechanistic studies showed that bismuth drugs effectively suppress the enzymatic activity of Tet(X) resistance protein. Specifically, bismuth nitrate targets the active center of Tet(X4) protein, while bismuth binds to the resistance protein in a noncompetitive manner. Our data open up a new horizon for the treatment of infections caused by tet(X)-bearing superbugs.

Orally administered bismuth drug together with N-acetyl cysteine as a broad-spectrum anti-coronavirus cocktail therapy

A cocktail therapy comprising bismuth drugs and N-acetyl-l-cysteine is reported to suppress the replication of SARS-CoV-2 via the oral route. The broad-spectrum inhibitory activities of the combination upon key viral cysteine enzymes are verified.

Comparison of Rhenium and Iodine as Contrast Agents in X-Ray Imaging

Purpose

The majority of X-ray contrast agents (XCA) are made with iodine, but iodine-based XCA (I-XCA) exhibit low contrast in high kVp X-rays due to iodine's low atomic number (Z = 53) and K-edge (33.1 keV). While rhenium is a transition metal with a high atomic number (Z = 75) and K-edge (71.7 keV), the utilization of rhenium-based XCA (Re-XCA) in X-ray imaging techniques has not been studied in depth. Our study had two objectives: (1) to compare both the image quality and the absorbed dose of I- and Re-XCA and (2) to prepare and image a rhenium-doped scaffold. Procedures. I- and Re-XCA were prepared and imaged from 50 to 120 kVp by Micro-computed tomography (µCT) and digital radiography and from 120 to 220 kVp by planar X-ray imaging. The scans were repeated using 0.1 to 1.6 mm thick copper filters to harden the X-ray beam. A rhenium-doped scaffold was prepared via electrospinning, used to coat catheters, and imaged at 90 kVp by µCT.

Results

I-XCA have a greater contrast-to-noise ratio (CNR) at 50 and 80 kVp, but Re-XCA have a greater CNR at >120 kVp. The difference in CNR is increased as the thickness of the copper filters is increased. For instance, the percent CNR improvement of rhenium over iodine is 14.2% with a 0.6 mm thick copper filter, but it is 59.1% with a 1.6 mm thick copper filter, as shown at 120 kVp by µCT. Upon coating them with a rhenium-doped scaffold, the catheters became radiopaque.

Conclusions

Using Monte Carlo simulations, we showed that it is possible to reduce the absorbed dose of high kVp X-rays while allowing the acquisition of high-quality images. Furthermore, radiopaque catheters have the potential of enhancing the contrast during catheterizations and helping physicians to place catheters inside patients more rapidly and precisely.

Tumor Microenvironment Modulation Platform Based on Composite Biodegradable Bismuth-Manganese Radiosensitizer for Inhibiting Radioresistant Hypoxic Tumors

Solid tumors possess a unique internal environment with high-level thiols (mainly glutathione), over-expressed H₂ O₂ , and low oxygen partial pressure, which severely restrict the radiotherapy (RT) efficacy. To overcome the imperfections of RT alone, there is vital to design a multifunctional radiosensitizer that simultaneously achieves multimodal therapy and tumor microenvironment (TME) regulation. Bismuth (Bi)-based nanospheres are wrapped in the MnO₂ layer to form core-shell-structured radiosensitizer (Bi@Mn) that can effectively load docetaxel (DTX). The solubility of Bi@Mn-DTX is further improved via folic acid-modified amphiphilic polyethylene glycol (PFA). Bi@Mn-DTX-PFA can specifically respond to the TME to realize multimodal therapy. Primarily, the outer MnO₂ layer responds with H₂ O₂ and glutathione to release oxygen and generate •OH, thereby alleviating hypoxia and achieving chemodynamic therapy (CDT). Afterward, the strong coordination between Bi³⁺ and deprotonated thiol groups in glutathione allows the mesoporous Bi-containing core bonding with glutathione to form a water-soluble complex. These actions conduce Bi@Mn-DTX-PFA degradation, further releasing DTX to implement chemotherapy (CHT). In addition, the degradation in vivo and tumor enrichment of Bi@Mn-PFA are explored via T₁ -weighted magnetic resonance and computed tomography imaging. The biodegradable composite Bi@Mn-DTX-PFA can simultaneously modulate the TME and achieve multimodal treatment (RT/CDT/CHT) for hypoxic tumors.

A Whole-Body Physiologically Based Pharmacokinetic Model for Alpha Particle Emitting Bismuth in Rats

Introduction/Aim: α particle emitting bismuth (²¹²Bi) as decay product of ²¹²Pb-labeled pharmaceuticals has been effective in targeted α particle therapy (TAT). Estimating the contribution of ²¹²Bi released from its chelator to the absorbed doses in nontarget tissues is challenging in TAT. Physiologically based pharmacokinetic (PBPK) modeling can help overcome this limitation. Therefore, a whole-body ²¹²Bi-PBPK model was developed to describe the pharmacokinetics (PKs) of ²¹²Bi in rats. Materials and Methods: The rat ²¹²Bi-PBPK model was implemented using the modeling software SAAM II with data and parameter values from the literature. Besides other mechanisms, ²¹²Bi interactions with red blood cells, high molecular weight plasma protein, and intracellular biological thiols are described. Important PK parameters were fitted to time-activity data. Absorbed dose coefficients (ADCs) were calculated for injecting 0.774 fmol of ²¹²Bi. Results: ²¹²Bi uptake rates of liver, bone, small intestine, bone marrow, skin, and muscle were (0.86 ± 0.13), (3.85 ± 0.63), (0.27 ± 0.05), (1.44 ± 0.29), (0.04 ± 0.01), and (0.007 ± 0.007) per min with corresponding ADCs of 0.09, 0.03, 0.03, 0.07, 0.01, and 0.003 mGy/kBq, respectively. An ADC of 0.70 mGy/kBq was determined for kidneys. Conclusion: Kidneys are the dose-limiting organs in ²¹²Bi-based TAT. The ²¹²Bi-PBPK model is an effective tool to investigate the ²¹²Bi biodistribution in murine models. Integrating the ²¹²Bi-PBPK model into other murine and human PBPK models of α particle generators can help study the efficacy and safety of TAT.

Structurally restricted Bi(III) metallation of apo-βMT1a: metal-induced tangling

Non-toxic bismuth salts are used in anti-ulcer medications and to protect against nephrotoxicity from anticancer drugs. Bismuth salts also induce metallothionein (MT), a metal-binding protein that lacks a formal secondary structure. We report the impact on the metallation properties of Bi(III) to the 9-cysteine β fragment of MT as a function of cysteine accessibility using electrospray ionization mass spectrometry. At pH 7.4, Bi2βMT formed cooperatively. Cysteine modification shows that each Bi(III) was terminally bound to three cysteinyl thiolates. Non-cooperative Bi(III) binding was observed at pH 2.3, where cysteine accessibility is increased. However, competition from H4EDTA inhibited Bi(III) binding. When GdmCl, a well-known denaturing agent, was used to increase cysteine accessibility of the apoβMT at pH 7.4, a greater fraction of Bi3βMT formed using all nine cysteines. The change in binding profile and equilibrium of Bi2βMT was determined as a function of acidification, which changed as a result of competition with H4EDTA. There was no Bi(III) transfer between Bi2βMT, Cd3βMT, and Zn3βMT. This lack of metal exchange and the resistance towards binding the third Bi(III) suggest a rigidity in the Bi2βMT binding sites that inhibits Bi(III) mobility. These experiments emphasize the conformational control of metallation that results in substantially different metallated products: at pH 7.4 (many cysteines buried) Bi2βMT, whereas at pH 7.4 (all cysteines accessible) enhanced formation of Bi3βMT. These data suggest that the addition of the first two Bi(III) crosslinks the protein, blocking access to the remaining three cysteines for the third Bi(III), as a result of tangle formation.

A biodegradable bismuth–gadolinium-based nano contrast agent for accurate identification and imaging of renal insufficiency in vivo

A biodegradable gadolinium-doped mesoporous bismuth-based nanomaterial is used to diagnose kidneys with dysfunction accurately via magnetic resonance imaging in vivo.

Nanozyme-Incorporated Biodegradable Bismuth Mesoporous Radiosensitizer for Tumor Microenvironment-Modulated Hypoxic Tumor Thermoradiotherapy

Solid tumors inevitably develop radioresistance due to low oxygen partial pressure in the tumor microenvironment. Despite numerous attempts, there are still few effective ways to avoid the hypoxia-induced poor radiotherapeutic effect. To overcome this problem, platinum (Pt) nanodots were fabricated into a mesoporous bismuth (Bi)-based nanomaterial to construct a biodegradable nanocomposite BiPt-folic acid-modified amphiphilic polyethylene glycol (PFA). BiPt-PFA could act as a radiosensitizer to enhance the absorption of X-rays at the tumor site and simultaneously trigger response behaviors related to the tumor microenvironment due to the enrichment of materials in the tumor area. During this process, the Bi-based component consumed glutathione via coordination, thus altering the oxidative stress balance, while Pt nanoparticles catalyzed the decomposition of hydrogen peroxide to generate oxygen, thereby relieving tumor hypoxia. Both Pt and Bi thus co-modulated the tumor microenvironment to improve the radiotherapeutic effect. In addition, Pt dots in BiPt-PFA had strong near-infrared absorption ability and created an intensive photothermal therapeutic effect. Modulation of the tumor microenvironment could thus improve the therapeutic effect in hypoxic tumors by a combination of photothermal therapy and enhanced radiotherapy. BiPt-PFA, as a biodegradable nanocomposite, may thus modulate the tumor microenvironment to enhance the hypoxic tumor therapeutic effect by thermoradiotherapy.

A Review on the Biodistribution, Pharmacokinetics and Toxicity of Bismuth-Based Nanomaterials

Here, bismuth-based nanomaterials (Bi-based NMs) are introduced as promising theranostic agents to enhance image contrast as well as for the therapeutic gain for numerous diseases. However, understanding the interaction of such novel developed nanoparticles (NPs) within a biological environment is a requisite for the translation of any promising agent from the lab bench to the clinic. This interaction delineates the fate of NPs after circulation in the body. In an ideal setting, a nano-based therapeutic agent should be eliminated via the renal clearance pathway, meanwhile it should have specific targeting to a diseased organ to reach an effective dose and also to overcome off-targeting. Due to their clearance pathway, biodistribution patterns and pharmacokinetics (PK), Bi-based NMs have been found to play a determinative role to pass clinical approval and they have been investigated extensively in vivo to date. In this review, we expansively discuss the possible toxicity induced by Bi-based NMs on cells or organs, as well as biodistribution profiles, PK and the clearance pathways in animal models. A low cytotoxicity of Bi-based NMs has been found in vitro and in vivo, and along with their long-term biodistribution and proper renal clearance in animal models, the translation of Bi-based NMs to the clinic as a useful novel theranostic agent is promising to improve numerous medical applications.

SARS-Coronavirus-2 Nsp13 Possesses NTPase and RNA Helicase Activities That Can Be Inhibited by Bismuth Salts

The ongoing outbreak of Coronavirus Disease 2019 (COVID-19) has become a global public health emergency. SARS-coronavirus-2 (SARS-CoV-2), the causative pathogen of COVID-19, is a positive-sense single-stranded RNA virus belonging to the family Coronaviridae. For RNA viruses, virus-encoded RNA helicases have long been recognized to play pivotal roles during viral life cycles by facilitating the correct folding and replication of viral RNAs. Here, our studies show that SARS-CoV-2-encoded nonstructural protein 13 (nsp13) possesses the nucleoside triphosphate hydrolase (NTPase) and RNA helicase activities that can hydrolyze all types of NTPs and unwind RNA helices dependently of the presence of NTP, and further characterize the biochemical characteristics of these two enzymatic activities associated with SARS-CoV-2 nsp13. Moreover, we found that some bismuth salts could effectively inhibit both the NTPase and RNA helicase activities of SARS-CoV-2 nsp13 in a dose-dependent manner. Thus, our findings demonstrate the NTPase and helicase activities of SARS-CoV-2 nsp13, which may play an important role in SARS-CoV-2 replication and serve as a target for antivirals.

Bismuth(III) Flavonolates: The Impact of Structural Diversity on Antibacterial Activity, Mammalian Cell Viability and Cellular Uptake

A series of homoleptic and heteroleptic bismuth(III) flavonolate complexes derived from six flavonols of varying substitution have been synthesised and structurally characterised. The complexes were evaluated for antibacterial activity towards several problematic Gram-positive (Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE)) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. The cell viability of COS-7 (monkey kidney) cells treated with the bismuth flavonolates was also studied to determine the effect of the complexes on mammalian cells. The heteroleptic complexes [BiPh(L)₂ ] (in which L=flavonolate) showed good antibacterial activity towards all of the bacteria but reduced COS-7 cell viability in a concentration-dependent manner. The homoleptic complexes [Bi(L)₃ ] exhibited activity towards the Gram-positive bacteria and showed low toxicity towards the mammalian cell line. Bismuth uptake studies in VRE and COS-7 cells treated with the bismuth flavonolate complexes indicated that Bi accumulation is influenced by both the substitution of the flavonolate ligands and the degree of substitution at the bismuth centre.

Biotransformation of arsenic and toxicological implication of arsenic metabolites

Arsenic is a well-known environmental carcinogen and chronic exposure to arsenic through drinking water has been reported to cause skin, bladder and lung cancers, with arsenic metabolites being implicated in the pathogenesis. In contrast, arsenic trioxide (As₂O₃) is an effective therapeutic agent for the treatment of acute promyelocytic leukemia, in which the binding of arsenite (iAs^III) to promyelocytic leukemia (PML) protein is the proposed initial step. These findings on the two-edged sword characteristics of arsenic suggest that after entry into cells, arsenic reaches the nucleus and triggers various nuclear events. Arsenic is reduced, conjugated with glutathione, and methylated in the cytosol. These biotransformations, including the production of reactive metabolic intermediates, appear to determine the intracellular dynamics, target organs, and biological functions of arsenic.

Upregulation of nuclear factor (erythroid-derived 2)-like 2 protein level in the human colorectal adenocarcinoma cell line DLD-1 by a heterocyclic organobismuth(III) compound: Effect of organobismuth(III) compound on NRF2 signaling

An increasing number of metal-based compounds, including arsenic trioxide, auranofin, and cisplatin, have been reported to have antitumor activity. Their beneficial effects are controlled by a transcription factor, nuclear factor (erythroid-derived 2)-like 2 (NRF2). In response to oxidative stress, NRF2 induces the expression of cytoprotective genes. NRF2 protein levels are regulated by Kelch-like ECH-associated protein 1 (KEAP1) via ubiquitination. Bi-chlorodibenzo[c,f][1,5]thiabismocine (compound 3), a bismuth compound, is known for its potent anti-proliferative activity against various cancer cell lines. In the present study, we investigated the effect of compound 3 on NRF2 signaling in the human colorectal adenocarcinoma cell line DLD-1 in terms of cell viability as well as mRNA and protein expression levels of NRF2. Compound 3 upregulated NRF2 protein levels in a time- and concentration-dependent manner, accompanied by a marked increase in heme-oxygenase-1 (HO-1) mRNA and protein levels. We observed that brusatol, an NRF2 inhibitor, as well as small interfering RNA (siRNA)-mediated knockdown of NRF2 in DLD-1 cells suppressed compound 3-induced HO-1 expression. The anticancer activity of compound 3 was enhanced by compounds that downregulate NRF2. These results suggest that compound 3 upregulates HO-1 via NRF2 activation and that the NRF2-HO-1 pathway is the cellular response to compound 3. We also discovered that compound 3 slightly downregulated KEAP1; thus, NRF2 activation may be associated with KEAP1 modification. Collectively, our results indicate that compound 3 simultaneously activates an anti-oxidative stress pathway, such as NRF2 and HO-1, and a pro-cell death signal in DLD-1 cells. Our findings may provide useful information for the development of a potent anticancer organobismuth(III) compound.

pH dependence of the non-cooperative binding of Bi3+ to human apo-metallothionein 1A: kinetics, speciation, and stoichiometry

ESI-MS along with cysteine modification show that the binding of Bi³⁺ to apo-metallothionein is non-cooperative with a coordination of BiS(cys)₃ up to Bi₆MT. Stopped flow kinetics reveal that the rate of binding depends on the pH and the Bi³⁺ anion.

Rod-shape theranostic nanoparticles facilitate antiretroviral drug biodistribution and activity in human immunodeficiency virus susceptible cells and tissues

Human immunodeficiency virus theranostics facilitates the development of long acting (LA) antiretroviral drugs (ARVs) by defining drug-particle cell depots. Optimal drug formulations are made possible based on precise particle composition, structure, shape and size. Through the creation of rod-shaped particles of defined sizes reflective of native LA drugs, theranostic probes can be deployed to measure particle-cell and tissue biodistribution, antiretroviral activities and drug retention.

Methods: Herein, we created multimodal rilpivirine (RPV) ¹⁷⁷lutetium labeled bismuth sulfide nanorods (¹⁷⁷LuBSNRs) then evaluated their structure, morphology, configuration, chemical composition, biological responses and adverse reactions. Particle biodistribution was analyzed by single photon emission computed tomography (SPECT/CT) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) imaging.

Results: Nanoformulated RPV and BSNRs-RPV particles showed comparable physicochemical and cell biological properties. Drug-particle pharmacokinetics (PK) and biodistribution in lymphoid tissue macrophages proved equivalent, one with the other. Rapid particle uptake and tissue distribution were observed, without adverse reactions, in primary blood-derived and tissue macrophages. The latter was seen within the marginal zones of spleen.

Conclusions: These data, taken together, support the use of ¹⁷⁷LuBSNRs as theranostic probes as a rapid assessment tool for PK LA ARV measurements.

The pathways and domain specificity of Cu(i) binding to human metallothionein 1A

We describe the sequential formation of 3 key Cu(i)–thiolate clusters in human metallothionein 1A using a combination of ESI-MS and phosphorescence lifetime methods.

Biosynthesis of bismuth selenide nanoparticles using chalcogen-metabolizing bacteria

Cost and energy reductions in the production process of bismuth chalcogenide (BC) semiconductor materials are essential to make thermoelectric generators comprised of BCs profitable and CO₂ neutral over their life cycle. In this study, as an eco-friendly production method, bismuth selenide (Bi₂Se₃) nanoparticles were synthesized using the following five strains of chalcogen-metabolizing bacteria: Pseudomonas stutzeri NT-I, Pseudomonas sp. RB, Stenotrophomonas maltophilia TI-1, Ochrobactrum anthropi TI-2, and O. anthropi TI-3 under aerobic conditions. All strains actively volatilized selenium (Se) by reducing selenite, possibly to organoselenides. In the growth media containing bismuth (Bi) and Se, all strains removed Bi and Se concomitantly and synthesized nanoparticles containing Bi and Se as their main components. Particles synthesized by strain NT-I had a theoretical elemental composition of Bi₂Se₃, whereas those synthesized by other strains contained a small amount of sulfur in addition to Bi and Se, making strain NT-I the best Bi₂Se₃ synthesizer among the strains used in this study. The particle sizes were 50-100 nm in diameter, which is sufficiently small for nanostructured semiconductor materials that exhibit quantum size effect. Successful synthesis of Bi₂Se₃ nanoparticles could be attributed to the high Se-volatilizing activities of the bacterial strains. Selenol-containing compounds as intermediates of Se-volatilizing metabolic pathways, such as methane selenol and selenocysteine, may play an important role in biosynthesis of Bi₂Se₃.

Inactivation of NikR from Helicobacter pylori by a bismuth drug

The NikR protein is an essential DNA regulator of Helicobacter pylori, a human pathogen, which infects almost half of the world's population. Herein, we comprehensively characterized the interaction of a bismuth drug with Helicobacter pylori NikR. We show that Bi(III) can occupy the high-affinity Ni(II) site of NikR. The highly-conserved residue Cys107 at this site is critical for Bi(III) binding. Importantly, such a binding disassembles physiologically functional NikR tetramer into inactive dimer, leading to abrogation of the DNA-binding capability of NikR. Bi(III)-binding also significantly disturbs regulatory function of Helicobacter pylori NikR in vivo. Therefore, NikR might serve as a potential intracellular target of a bismuth drug.

A Novel Synthetic Compound, Bismuth Zinc Citrate, Could Potentially Reduce Cisplatin-Induced Toxicity Without Compromising the Anticancer Effect Through Enhanced Expression of Antioxidant Protein

Cisplatin is a common anticancer drug, but it comes with significant nephrotoxicity. Further cisplatin-induced oxidative stress contributes to the pathogenesis of the nephrotoxicity. A new compound, BiZn, can potentially prevent this complication. We verified our postulation by in vitro and in vivo models. From our findings, BiZn did not affect cisplatin-induced cytotoxicity on neuroblastoma cells under both in vitro and in vivo settings. However, BiZn significantly reduced the blood urea nitrogen and creatinine levels in cisplatin-treated mice. Under the lethal dosage of cisplatin, co-treatment of BiZn significantly increased the survival rate. BiZn stimulated antioxidant proteins metallothionein (MT) and glutathione (GSH) generation from kidney cells and minimized cisplatin-induced apoptosis. Knocking down MT-IIA and inhibiting GSH abolished such protection. In conclusion, pretreatment of BiZn decreased cisplatin-induced renal toxicity without affecting its antitumor activity. BiZn-induced antioxidant proteins MT and GSH may contribute to the renal protection effect.

Water-Dispersible Bismuth-Organic Materials with Computed Tomography Contrast Properties

Two bismuth-organic network polymers were synthesized by means of a one-step polycondensation reaction between an aromatic dithiol/trithiol and triphenylbismuth. The materials were characterized by solid-state UV-vis spectroscopy, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, elemental microanalysis, and thermogravimetric analysis. Uniform dispersion of the hydrophobic and water-insoluble bismuth-containing polymers in aqueous media was achieved by the addition of 2 kDa poly(ethylene glycol) methyl ether thiol. This enabled quantitative phantom imaging experiments on a clinical computed tomography (CT) scanner, which showed that the coordination polymers possessed strong CT contrast properties. The observed X-ray attenuation properties of each coordination polymer were correlated with its bismuth payload. The X-ray opacity, thermal and chemical stabilities, and aqueous dispersibility of this novel class of bismuth-organic materials make them potentially useful as biomedical CT contrast agents and radiopaque materials.

Unravelling the mechanistic details of metal binding to mammalian metallothioneins from stoichiometric, kinetic, and binding affinity data

Metallothioneins (MTs) are small, cysteine-rich proteins, found throughout Nature. Their ability to bind a number of different metals with a range of stoichiometric ratios means that this protein family is critically important for essential metal (Zn²⁺ and Cu⁺) homeostasis, metal storage, metal donation to nascent metalloenzymes as well as heavy metal detoxification. With its 20 cysteines, metallothionein is also considered to protect cells against oxidative stress. MT has been studied by a large number of researchers over the last 6 decades using a variety of spectroscopic techniques. The lack of distinguishing chromophores for the multitude of binding sites has made the evaluation of stoichiometric properties for different metals challenging. Initially, only ¹¹³Cd-NMR spectroscopy could provide strong evidence for the proposed cluster formation of Cd-MT. The extraordinary development of electrospray ionization mass spectrometry (ESI-MS), where all coexisting species in solution are observed, revolutionized MT research. Prior to the use of ESI-MS data, a range of "magic numbers" representing metal-to-MT molar ratios were reported from optical spectroscopic studies. The availability of ESI mass spectral data led to (i) the confirmation of cluster formation, (ii) a conceptual understanding of the cooperativity involved in multiple metal binding events, (iii) the presence of domain specificity between regions of the protein and (iv) mechanistic details involving both binding affinities and rate constants. The kinetic experiments identified the presence of multiple individual binding sites, each with a unique rate constant and an analogous binding affinity. The almost linear trend in rate constants as a function of bound As³⁺ provided a unique insight that became a critical step in the complete understanding of the mechanistic details of the metalation of MT. To fully define the biological function of this sulfur-rich protein it is necessary to determine kinetic rate constants and binding affinities for the essential metals. Recently, Zn²⁺ competition experiments between both of the isolated fragments (α and β) and the full-length protein (βα-MT 1a) as well as Zn²⁺ competition between βα-MT 1a and carbonic anhydrase were reported. From these data, the trend in binding affinities and the values of the K_f of the 7 bimolecular reactions involved in metalation were determined. From the analysis of ESI-MS data for Cu⁺ binding to βα-MT 1a at different pH-values, a trend in the 20 binding affinities for the complete metalation mechanism was reported. This review details a personal view of the historical development of the determination of stoichiometry for metal binding, the structure of the binding sites, the rates of the metalation reactions and the underlying binding affinities for each metalation step. We have attempted to summarize the experimental developments that led to the publication in May 2017 of the experimental determination of the 20 binding constants for the 20 sequential bimolecular reactions for Cu⁺ binding to the 20 Cys of apoMT as a function of pH that show the appearance and disappearance of clusters. We report both published data and in a series of tables an assembly of stoichiometries, and equilibrium constants for Zn²⁺ and Cu⁺ for many different metallothioneins.

Exposure and nephrotoxicity concern of bismuth with the occurrence of autophagy

Metal nanoparticles or metal-based compounds have drawn attention in various fields ranging from industry to medicine because of their unique physicochemical properties. Bismuth (Bi) compounds and nanomaterials have been commonly used in alloys, electronic industry, batteries, and as flame retardants as well as for anti- Helicobacter pylori therapy, while the nanomaterial form has great potential for computed tomography imaging and thermotherapy, both of which will be introduced in this review. Although Bi was used for several decades, there is a lack of detailed information concerning their toxicity and mechanisms on human health. We described the toxicity of Bi on the kidney that seemed to be relatively known by researchers, while the mechanisms remain unclear. Recently, our group has found that Bi compounds, including bismuth nitrate (BN) and Bi nanomaterials, can induce autophagy in kidney cells. We also extended our findings by selecting five Bi compounds, and the results showed that BN, bismuth oxychloride, bismuth citrate, colloidal bismuth subcitrate, and Bi nanomaterials all induced slight cytotoxicity accompanied with autophagy. Although the role of autophagy in Bi-induced cytotoxicity and kidney injury is under investigation by us, autophagy may help with the exploration of the mechanisms of nephrotoxicity by Bi.

Functionalized Cu3BiS3 nanoparticles for dual-modal imaging and targeted photothermal/photodynamic therapy

Multifunctional nano-biomaterials with the integration of diagnostic and therapeutic functions have shown great promise in improving the efficacy of cancer therapy. Herein, a new nanoplatform based on functionalized Cu₃BiS₃ nanoparticles (NPs) is fabricated for tumour-targeted combination phototherapy. The as-synthesized hydrophobic Cu₃BiS₃ NPs are modified with DSPE-PEG/DSPE-PEG-NH₂, followed by the conjugation of the photosensitizer chlorin e6 (Ce6) and the target ligand folic acid (FA). The introduced Ce6 can further form a chelate complex with Gd³⁺. The rationally designed Cu₃BiS₃-PEG-(Ce6-Gd³⁺)-FA NPs, which have high physiological stability and good biocompatibility, can specifically target FA-receptor over-expressed tumour cells. The Cu₃BiS₃-PEG-(Ce6-Gd³⁺)-FA NPs exhibit effective dual-modal CT and MR imaging in the xenografted HeLa tumours. Importantly, excellent in vivo anti-tumour effects have been achieved by synergistic photothermal/photodynamic therapy using the multifunctional NPs. We expect that this versatile nanoplatform will play a role in exploring precise cancer diagnosis and therapy.

Biocompatible PEGylated bismuth nanocrystals: "All-in-one" theranostic agent with triple-modal imaging and efficient in vivo photothermal ablation of tumors

Biocompatible single-component theranostic agents integrating multimodal imaging and therapeutic functions (namely, "all-in one" agents) are highly desired for clinical cancer treatments. Herein, PEGylated pure metallic bismuth nanocrystals (Bi-PEG NCs) have been developed to be a competent theranostic agent for in vivo high-performance multimodal bio-imaging and photothermal ablation of tumors. The resultant Bi-PEG NCs show excellent physiological stability, biocompatibility, prolonged blood circulation half-life and preferential tumor accumulation. Thanking to the strong near-infrared (NIR) absorbance as well as the high photothermal conversion efficiency and conversion stability, highly effective in vivo photothermal ablation on tumors has been realized upon NIR irradiation, without noticeable toxicity. Impressively, the Bi-PEG NCs show ultrahigh X-ray computed topography (CT) enhancement efficiency (∼60.3 HU mL mg^-1), overwhelming all CT contrast agents reported so far. Combining the strong CT contrast ability and photoacoustic/photothermal effect, high-contrast CT, photoacoustic (PA) and infrared thermal (IRT) triple-modal imaging have been demonstrated both in vitro and in vivo. This work highlights the potentials of such NCs as a powerful "all-in-one" theranostic nanoplatform for bioimaging and antitumor therapy, and may have provided a rather promising candidate for clinically-applied antitumor treatments based on single-component agents.

Autophagy associated cytotoxicity and cellular uptake mechanisms of bismuth nanoparticles in human kidney cells

Bismuth compounds have been used for treatment of bacterial infection, and recently bismuth nanoparticles (BiNP) were synthesized for imaging and diagnostic purpose, while safety concern of bismuth cannot be ignored. Here, we prepared ultrasmall BiNP and showed an enhanced tumor imaging, but BiNP revealed a differentiated cytotoxicity in human embryonic kidney 293 cells (HEK293) compared to other cell types. For the first time, we found that BiNP can induce autophagy, shown as the increase of monodansylcadaverine fluorescence staining and the amount of LC3II that can be inhibited by 3-MA. BiNP were capable of entering cells in a dose and time dependent manner by fluorescence and element detection methods BiNP were found to be localized in the cytoplasm observed by transmission electron microscopy and intracellular bismuth element confirmed by energy dispersive X-ray analysis. Using endocytic inhibitors, BiNP were found to require ATP and endosomal trafficking pathways for their cellular uptake. Internalized BiNP did not co-localize with EEA1, but co-localized with Lysotracker/LAMP1/LAMP2 at late time points, indicating BiNP may be retained in the non-early endosomal vacuoles and late endosomes. With our novel finding of bismuth induced autophagy and endocytic mechanisms, potential approaches may be applied to reduce the toxicity by bismuth.

Compound Copper Chalcogenide Nanocrystals

This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), energy storage (lithium-ion batteries, hydrogen generation), emissive materials (plasmonics, LEDs, biolabelling), sensors (electrochemical, biochemical), biomedical devices (magnetic resonance imaging, X-ray computer tomography), and medical therapies (photochemothermal therapies, immunotherapy, radiotherapy, and drug delivery). The confluence of advances in the synthesis, assembly, and application of these NCs in the past decade has the potential to significantly impact society, both economically and environmentally.

Functional disruption of peroxiredoxin by bismuth antiulcer drugs attenuates Helicobacter pylori survival

Bismuth drugs have been used clinically to treat infections from Helicobacter pylori, a pathogen that is strongly related to gastrointestinal diseases even stomach cancer. Despite extensive studies, the mechanisms of action of bismuth drugs are not fully understood. Alkyl hydroperoxide reductase subunit C (AhpC) is the most abundant 2-cysteine peroxiredoxin, crucial for H. pylori survival in the host by defense of oxidative stress. Herein we show that a Bi(III) antiulcer drug (CBS) binds to the highly conserved cysteine residues (Cys49 and Cys169) with a dissociation constant (K _d) of Bi(III) to AhpC of 3.0 (±1.0) × 10^-24 M. Significantly the interaction of CBS with AhpC disrupts the peroxiredoxin and chaperone activities of the enzyme both in vitro and in bacterial cells, leading to attenuated bacterial survival. Moreover, using a home-made fluorescent probe, we demonstrate that Bi(III) also perturbs AhpC relocation between the cytoplasm and membrane region in decomposing the exogenous ROS. Our study suggests that disruption of redox homeostasis by bismuth drugs via interaction with key enzymes such as AhpC contributes to their antimicrobial activity.

Radiopaque UHMWPE sublaminar cables for spinal deformity correction: Preclinical mechanical and radiopacifier leaching assessment

Polymeric sublaminar cables have a number of advantages over metal cables in the field of spinal deformity surgery, with decreased risk of neurological injury and potential for higher correction forces as the two most predominant. However, currently available polymer cables are radiolucent, precluding postoperative radiological assessment of instrumentation stability and integrity. This study provides a preclinical assessment of a woven UHMWPE cable made with radiopaque UHMWPE fibers. Our primary goal was to determine if the addition of a radiopacifier negatively affects the mechanical properties of UHMWPE woven cables. Tensile mechanical properties were determined and compared to suitable controls. Radiopacity was evaluated and radiopacifier leaching was assessed in vitro and in vivo. Finally, in vivo bismuth organ content was quantified after a 24-week implantation period in sheep. Results show that the mechanical properties of woven UHMWPE cables were not deleteriously affected by the addition of homogenously dispersed bismuth oxide particles within each fiber. Limited amounts of bismuth oxide were released in vitro, well below the toxicological threshold. Tissue concentrations lower than generally accepted therapeutic dosages for use against gastrointestinal disorders, well below toxic levels, were discovered in vivo. These results substantiate controlled clinical introduction of these radiopaque UHMWPE cables. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 771-779, 2018.

Improved safety and efficacy of 213Bi-DOTATATE-targeted alpha therapy of somatostatin receptor-expressing neuroendocrine tumors in mice pre-treated with L-lysine

Background

Targeted alpha therapy (TAT) offers advantages over current β-emitting conjugates for peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors. PRRT with ¹⁷⁷Lu-DOTATATE or ⁹⁰Y-DOTATOC has shown dose-limiting nephrotoxicity due to radiopeptide retention in the proximal tubules. Pharmacological protection can reduce renal uptake of radiopeptides, e.g., positively charged amino acids, to saturate in the proximal tubules, thereby enabling higher radioactivity to be safely administered. The aim of this preclinical study was to evaluate the therapeutic effect of ²¹³Bi-DOTATATE with and without renal protection using L-lysine in mice. Tumor uptake and kinetics as a function of injected mass of peptide (range 0.03–3 nmol) were investigated using ¹¹¹In-DOTATATE. These results allowed estimation of the mean radiation absorbed tumor dose for ²¹³Bi-DOTATATE. Pharmacokinetics and dosimetry of ²¹³Bi-DOTATATE was determined in mice, in combination with renal protection. A dose escalation study with ²¹³Bi-DOTATATE was performed to determine the maximum tolerated dose (MTD) with and without pre-administration of l-lysine as for renal protection. Neutrophil gelatinase-associated lipocalin (NGAL) served as renal biomarker to determine kidney injury.

Results

The maximum mean radiation absorbed tumor dose occurred at 0.03 nmol and the minimum at 3 nmol. Similar mean radiation absorbed tumor doses were determined for 0.1 and 0.3 nmol with a mean radiation absorbed dose of approximately 0.5 Gy/MBq ²¹³Bi-DOTATATE. The optimal mass of injected peptide was found to be 0.3 nmol. Tumor uptake was similar for ¹¹¹In-DOTATATE and ²¹³Bi-DOTATATE at 0.3 nmol peptide. Lysine reduced the renal uptake of ²¹³Bi-DOTATATE by 50% with no effect on the tumor uptake. The MTD was <13.0 ± 1.6 MBq in absence of l-lysine and 21.7 ± 1.9 MBq with l-lysine renal protection, both imparting an LD₅₀ mean renal radiation absorbed dose of 20 Gy. A correlation was found between the amount of injected radioactivity and NGAL levels.

Conclusions

The therapeutic potential of ²¹³Bi-DOTATATE was illustrated by significantly decreased tumor burden and improved overall survival. Renal protection with l-lysine immediately prior to TAT with ²¹³Bi-DOTATATE prolonged survival providing substantial evidence for pharmacological nephron blockade to mitigate nephrotoxicity.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-016-0240-5) contains supplementary material, which is available to authorized users.

Bio-coordination of bismuth in Helicobacter pylori revealed by immobilized metal affinity chromatography

Over 300 Bi-binding peptides from 166 proteins in H. pylori were identified by Bi-IMAC. Bi(3+) exhibits high selectivity towards peptide enriched by cysteines and histidines with dominated motif patterns of CXnC, CXnH and HXnH. Structural rationalization and functional categorization on the identified Bi-binding peptides and proteins provide an insight into the inhibitory action of bismuth drugs.

Multifunctional Inorganic Nanoparticles: Recent Progress in Thermal Therapy and Imaging

Nanotechnology has enabled the development of many alternative anti-cancer approaches, such as thermal therapies, which cause minimal damage to healthy cells. Current challenges in cancer treatment are the identification of the diseased area and its efficient treatment without generating many side effects. Image-guided therapies can be a useful tool to diagnose and treat the diseased tissue and they offer therapy and imaging using a single nanostructure. The present review mainly focuses on recent advances in the field of thermal therapy and imaging integrated with multifunctional inorganic nanoparticles. The main heating sources for heat-induced therapies are the surface plasmon resonance (SPR) in the near infrared region and alternating magnetic fields (AMFs). The different families of inorganic nanoparticles employed for SPR- and AMF-based thermal therapies and imaging are described. Furthermore, inorganic nanomaterials developed for multimodal therapies with different and multi-imaging modalities are presented in detail. Finally, relevant clinical perspectives and the future scope of inorganic nanoparticles in image-guided therapies are discussed.

PEGylated Cu3BiS3 hollow nanospheres as a new photothermal agent for 980 nm-laser-driven photothermochemotherapy and a contrast agent for X-ray computed tomography imaging

Developing multifunctional near-infrared (NIR) light-driven photothermal agents is in high demand for efficient cancer therapy. Herein, PEGylated Cu3BiS3 hollow nanospheres (HNSs) with an average diameter of 80 nm were synthesized through a facile ethylene glycol-mediated solvothermal route. The obtained PEGylated Cu3BiS3 HNSs exhibited strong NIR optical absorption with a large molar extinction coefficient of 4.1 × 10(9) cm(-1) M(-1) at 980 nm. Under the irradiation of a 980 nm laser with a safe power density of 0.72 W cm(-2), Cu3BiS3 HNSs produced significant photothermal heating with a photothermal transduction efficiency of 27.5%. The Cu3BiS3 HNSs also showed a good antitumoral drug doxorubicin (DOX) loading capacity and pH- and NIR-responsive DOX release behaviors. At a low dosage of 10 μg mL(-1), HeLa cells could be efficiently killed through a synergistic effect of chemo- and photothermo-therapy respectively based on the DOX release and the photothermal effect of Cu3BiS3 HNSs. In addition, Cu3BiS3 HNSs displayed a good X-ray computed tomography (CT) imaging capability. Furthermore, Cu3BiS3 HNSs could be used for efficient in vivo photothermochemotherapy and X-ray CT imaging of mice bearing melanoma skin cancer. This multifunctional theranostic nanomaterial shows potential promise for cancer therapy.

Similarities between N-Acetylcysteine and Glutathione in Binding to Lead(II) Ions

N-Acetylcysteine is a natural thiol-containing antioxidant, a precursor for cysteine and glutathione, and a potential detoxifying agent for heavy metal ions. However, previous accounts of the efficiency of N-acetylcysteine (H2NAC) in excretion of lead are few and contradicting. Here, we report results on the nature of lead(II) complexes formed with N-acetylcysteine in aqueous solution, which were obtained by combining information from several spectroscopic methods, including (207)Pb, (13)C, and (1)H NMR, Pb LIII-edge X-ray absorption, ultraviolet-visible (UV-vis) spectroscopy, and electro-spray ionization mass spectrometry (ESI-MS). Two series of solutions were used containing CPb(II) = 10 and 100 mM, respectively, varying the H2NAC/Pb(II) mole ratios from 2.1 to 10.0 at pH 9.1-9.4. The coordination environments obtained resemble those previously found for the Pb(II) glutathione system: at a ligand-to-lead mole ratio of 2.1, dimeric or oligomeric Pb(II) N-acetylcysteine complexes are formed, while a trithiolate [Pb(NAC)3](4-) complex dominates in solutions with H2NAC/Pb(II) mole ratios >3.0.

On-line coupling of continuous-flow gel electrophoresis with inductively coupled plasma-mass spectrometry to quantitatively evaluate intracellular metal binding properties of metallochaperones HpHypA and HpHspA in E. coli cells

On-line coupling of gel electrophoresis with inductively coupled plasma-mass spectrometry (GE-ICP-MS) offers a strategy to monitor intracellular metals and their associated proteins simultaneously. Herein, we examine the feasibility of the GE-ICP-MS system in the quantitative analysis of intracellular metal binding properties using two Helicobacter pylori metallochaperones HypA and HspA overexpressed in E. coli cells as showcases. We show that parallel detection of metal and sulfur signals allows accurate quantification of intracellular metal-protein stoichiometries, even for metalloproteins that bind metal ions with micromolar affinities. Using this approach, we demonstrate that only a trace amount of Ni(2+) is associated with HpHypA in cells, distinct from the in vitro observation of stoichiometric binding, while HpHypA exhibits high fidelity towards its structural metal Zn(2+) with stoichiometric Zn(2+) binding. In contrast, HpHspA associates with Zn(2+), Ni(2+), Cu(2+) and Co(2+) from an essential metal pool with ca. 0.5 molar equivalents of total metals bound per HpHspA monomer. The metal binding properties of both HpHypA and HpHspA were altered by Bi(3+). The binding of both Zn(2+) and Ni(2+) to HpHypA was suppressed under the stress of Bi(3+) in cells, different from in vitro studies that showed that Bi(3+) interfered with Zn(2+) but not Ni(2+) binding. This study provides an analytical approach to investigate the intracellular metal selectivity of overexpressed metalloproteins.

Glutathione and multidrug resistance protein transporter mediate a self-propelled disposal of bismuth in human cells

Glutathione and multidrug resistance protein (MRP) play an important role on the metabolism of a variety of drugs. Bismuth drugs have been used to treat gastrointestinal disorder and Helicobacter pylori infection for decades without exerting acute toxicity. They were found to interact with a wide variety of biomolecules, but the major metabolic pathway remains unknown. For the first time (to our knowledge), we systematically and quantitatively studied the metabolism of bismuth in human cells. Our data demonstrated that over 90% of bismuth was passively absorbed, conjugated to glutathione, and transported into vesicles by MRP transporter. Mathematical modeling of the system reveals an interesting phenomenon. Passively absorbed bismuth consumes intracellular glutathione, which therefore activates de novo biosynthesis of glutathione. Reciprocally, sequestration by glutathione facilitates the passive uptake of bismuth and thus completes a self-sustaining positive feedback circle. This mechanism robustly removes bismuth from both intra- and extracellular space, protecting critical systems of human body from acute toxicity. It elucidates the selectivity of bismuth drugs between human and pathogens that lack of glutathione, such as Helicobacter pylori, opening new horizons for further drug development.