Recent Development of Rhenium-Based Materials in the Application of Diagnosis and Tumor Therapy

Rhenium (Re) is widely used in the diagnosis and treatment of cancer due to its unique physical and chemical properties. Re has more valence electrons in its outer shell, allowing it to exist in a variety of oxidation states and to form different geometric configurations with many different ligands. The luminescence properties, lipophilicity, and cytotoxicity of complexes can be adjusted by changing the ligand of Re. This article mainly reviews the development of radionuclide 188Re in radiotherapy and some innovative applications of Re as well as the different therapeutic approaches and imaging techniques used in cancer therapy. In addition, the current application and future challenges and opportunities of Re are also discussed.

Protein Cages: From Fundamentals to Advanced Applications

Proteins that self-assemble into polyhedral shell-like structures are useful molecular containers both in nature and in the laboratory. Here we review efforts to repurpose diverse protein cages, including viral capsids, ferritins, bacterial microcompartments, and designed capsules, as vaccines, drug delivery vehicles, targeted imaging agents, nanoreactors, templates for controlled materials synthesis, building blocks for higher-order architectures, and more. A deep understanding of the principles underlying the construction, function, and evolution of natural systems has been key to tailoring selective cargo encapsulation and interactions with both biological systems and synthetic materials through protein engineering and directed evolution. The ability to adapt and design increasingly sophisticated capsid structures and functions stands to benefit the fields of catalysis, materials science, and medicine.

V, Kar B, Das U, Paira P. Target-specific mononuclear and binuclear rhenium(i) tricarbonyl complexes as upcoming anticancer drugs

Metal complexes have gradually been attracting interest from researchers worldwide as potential cancer therapeutics. Driven by the many side effects of the popular platinum-based anticancer drug cisplatin, the tireless endeavours of researchers have afforded strategies for the design of appropriate metal complexes with minimal side effects compared to cisplatin and its congeners to limit the unrestricted propagation of cancer. In this regard, transition metal complexes, especially rhenium-based complexes are being identified and highlighted as promising cancer theranostics, which are endowed with the ability to detect and annihilate cancer cells in the body. This is attributed the amazing photophysical properties of rhenium complexes together with their ability to selectively attack different organelles in cancer cells. Therefore, this review presents the properties of different rhenium-based complexes to highlight their recent advances as anticancer agents based on their cytotoxicity results.

In this review, rhenium-based complexes are highlighted as promising cancer theranostics, which are endowed with the ability to detect and annihilate cancer cells in the body.

New approach for the synthesis of water soluble fac-[MI(CO)3]+ bis(diarylphosphino)alkylamine complexes (M = 99Tc, Re)

A novel proof-of-concept is reported to modify the water solubility and potential biological effects of a bis(diphenylphosphino)alkylamine (PNP) ligand and the corresponding metal complex, by introducing an amine group on the outer periphery of the pendant ligand arm. Thus, a tertiary butoxycarbonyl protected N'-Boc-ethylenediamine-N,N-bis(diphenylphosphino) (N'-Boc-PNP) ligand (1) was synthesized by reacting the protected ethylenediamine and chlorodiphenylphosphine in a 1 : 2 molar ratio. The corresponding fac-[Re(CO)₃(N'-Boc-PNP)Br] (1A) complex was then obtained by reacting N'-Boc-PNP (1) with (Et₄N)₂fac-[Re(CO)₃Br₃] in equimolar amounts in DCM at 50 °C. De-protection of the N'-Boc pendant amine group in 1A with TFA leads to fac-[Re(NH₃⁺-PNP)(CO)₃Br]·CF₃COO^- (1B) which is soluble in D₂O (>0.05 M). Treating 1B with saturated aqueous NaHCO₃ yields fac-[Re(NH₂-PNP)(CO)₃Br]·MeOH (1C) in near quantitative yield. Although both 1A and 1C are not soluble in D₂O, addition of TFA easily generates 1B (³¹P NMR), confirming the formation of the protonated amine. Isolation of fac-[⁹⁹Tc(CO)₃(N-Boc-PNP)(Cl)] (1D) confirmed that the rhenium and technetium (⁹⁹Tc) can be easily interchanged in this process. Reported are hence the unique rhenium series of compounds 1A, 1B and 1C and the corresponding technetium complex 1D, unequivocally characterized by single crystal XRD, as well as IR and ¹H NMR spectroscopy. Preliminary antimicrobial evaluation indicates that ligand 1 and its respective rhenium complexes (1A-1C) were not active against selected fungi (Candida albicans and Cryptococcus neoformans) and bacteria (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus). These types of ligands and complexes therefore present themselves as excellent radio models for further evaluation using ¹⁸⁶Re, ¹⁸⁸Re and ^99mTc to potentially study the radiotoxicity of appropriately designed complexes.

Exploring preliminary structural relationships and mitochondrial targeting of fac-[MI(CO)3]-bis(diarylphosphino)alkylamine complexes (M = 99Tc, Re)

Preliminary structural relationships in fac-[MI(CO)3]-bis(diarylphosphino)alkylamine complexes (M = 99Tc, Re), antimicrobial and mitochondrial targeting are reported.

The potential application of gold-apoferritin nanocages conjugated with 2-amino-2-deoxy-glucose for imaging of breast cancer cells

Development of biocompatible and multifunctional nanoprobes for tumor targeting, imaging, and therapy still remains a great challenge. Herein, gold nanoparticles (AuNPs) were synthesized in the cavity of horse spleen apoferritin protein (HoSAF) and protein surface was labeled with 2-amino-2-deoxy-glucose (2DG) as a cell surface glucose transport protein specific targeting probe to study the feasibility of its usage as a computer tomography (CT) contrast agent with tumor targeting capability through in vitro experiments. 2DG conjugated and gold-loaded apoferritin (Au-HoSAF-2DG) nanoparticles (NPs) showed selective targeting for human breast adenocarcinoma (MCF-7) cells when compared to normal breast (MCF-10A) cells. This AuNP-based imaging agent was found to be non-cytotoxic in a given concentration range with an apoptotic effect upon longer exposure times towards MCF-7 cells, while MCF-10A cells were affected less. This selective cell death would also be useful for further cancer treatments with the ability of X-ray attenuation in in vitro X-ray and computed tomography (CT) imaging.

Magnetoferritin: Process, Prospects, and Their Biomedical Applications

Ferritin is a spherical iron storage protein composed of 24 subunits and an iron core. Using biomimetic mineralization, magnetic iron oxide can be synthesized in the cavity of ferritin to form magnetoferritin (MFt). MFt, also known as a superparamagnetic protein, is a novel magnetic nanomaterial with good biocompatibility and flexibility for biomedical applications. Recently, it has been demonstrated that MFt had tumor targetability and a peroxidase-like catalytic activity. Thus, MFt, with its many unique properties, provides a powerful platform for tumor diagnosis and therapy. In this review, we discuss the biomimetic synthesis and biomedical applications of MFt.

Potential of MRI in Radiotherapy Mediated by Small Conjugates and Nanosystems

Radiation therapy has made tremendous progress in oncology over the last decades due to advances in engineering and physical sciences in combination with better biochemical, genetic and molecular understanding of this disease. Local delivery of optimal radiation dose to a tumor, while sparing healthy surrounding tissues, remains a great challenge, especially in the proximity of vital organs. Therefore, imaging plays a key role in tumor staging, accurate target volume delineation, assessment of individual radiation resistance and even personalized dose prescription. From this point of view, radiotherapy might be one of the few therapeutic modalities that relies entirely on high-resolution imaging. Magnetic resonance imaging (MRI) with its superior soft-tissue resolution is already used in radiotherapy treatment planning complementing conventional computed tomography (CT). Development of systems integrating MRI and linear accelerators opens possibilities for simultaneous imaging and therapy, which in turn, generates the need for imaging probes with therapeutic components. In this review, we discuss the role of MRI in both external and internal radiotherapy focusing on the most important examples of contrast agents with combined therapeutic potential.

Ambient and high-pressure kinetic investigation of methanol substitution in fac-[Re(Trop)(CO)3(MeOH)] by different monodentate nucleophiles

First report of high-pressure methanol substitution by entering monodentate L forms fac-[Re(CO)₃(Trop)(L)] {ΔV^≠_(kL) = +9 – +14 cm⁻³ mol⁻¹}, indicating dissociative/dissociative interchange activation.

Cellular uptake and apoptotic potential of rhenium labeled magnetic protein cages in MDA-MB-231 cells

¹⁸⁸Re-magnetoferritin nanoparticles (NPs) provide an attractive platform for localized radiation therapy due to their magnetic targeting capability while enhancing contrast in magnetic resonans imaging (MRI) signals. In this study, cellular uptake, in vitro cytotoxicity, apoptotic potential of a non-radioactive isotope of rhenium in the form of ¹⁸⁷Re-magnetoferritin NPs were evaluated in both human normal mammary epithelial and breast metastatic adenocarcinoma cell lines. The results showed that, NP administration into the cells is through receptor mediated endocytosis and cancer cells displayed significantly higher uptake and cytotoxicity compared to normal cells. IC₅₀ values of nanoparticles were calculated as 0.96 mg/mL for cancer and 1.73 mg/mL for normal cells. Annexin V/ Propidium Iodide (PI) staining also showed that, NPs induced higher apoptotic rates in cancer cells compared to normal cells. Gene expression analyses confirming the results showed that, pro-apoptotic PUMA and BAX genes were significantly up-regulated while anti-apoptotic BCL-2 and SURVIVIN genes were down-regulated in cancer cells compared to normal cells. Overall, these in vitro results suggest that, ¹⁸⁷Re-magnetoferritin NPs have a promising potential for cancer therapy and can be used for imaging and diagnostic purposes for breast cancer at concentrations lower than 0.96 mg/mL. At concentrations above 1 mg/mL, NPs induce apoptosis which can also be used for cancer treatments.