Design an anticancer copper(II) pro-drug based on the flexible IIA subdomain of human serum albumin

Thermodynamics-based rules of thumb to evaluate the interaction of chelators and kinetically-labile metal ions in blood serum and plasma

Metal ions play a very important role in nature and their homeostasis is crucial. A lot of metal-related chemical research activities are ongoing that concern metal-based drugs or tools, such as chelation therapy, metal- and metabolite sensors, metallo-drugs and prodrugs, PET and MRI imaging agents, etc. In most of these cases, the applied chelator/ligand (L) or metal-ligand complex (M-L) has at least to pass the blood plasma to reach the target. Hence it is exposed to several metal-binding proteins (mainly serum albumin and transferrin) and to all essential metal ions (zinc, copper, iron, etc.). This holds also for studies in cultured cells when fetal calf serum is used in the medium. There is a risk that the applied compound (L or M-L) in the serum is transformed into a different entity, due to trans-metallation and/or ligand exchange reactions. This depends on the thermodynamics and kinetics. For kinetically-labile complexes, the complex stability with all the ligands and all metal ions present in serum is decisive in evaluating the thermodynamic driving force towards a certain fate of the chelator or metal-ligand complex. To consider that, an integrative view is needed on the stability constants, by taking into account all the metal ions present and all the main proteins to which they are bound, as well as the non-occupied metal binding site in proteins. Only then, a realistic estimation of the complex stability, and hence its potential fate, can be done. This perspective aims to provide a simple approach to estimate the thermodynamic stability of labile metal-ligand complexes in a blood plasma/serum environment. It gives a guideline to obtain an estimation of the plasma and serum complex stability and metal selectivity starting from the chemical stability constants of metal-ligand complexes. Although of high importance, it does not focus on the more complex kinetic aspects of metal-transfer reactions. The perspective should help for a better design of such compounds, to perform test tube assays which are relevant to the conditions in the plasma/serum and to be aware of the importance of ternary complexes, kinetics and competition experiments.

Transition Metal Complexes with Tridentate Schiff Bases (O N O and O N N) Derived from Salicylaldehyde: An Analysis of Their Potential Anticancer Activity

Although it is known that the first case of cancer was recorded in ancient Egypt around 1600 BC, it was not until 1917 during the First World War and the development of mustard gas that chemotherapy against cancer became relevant; however, its properties were not recognised until 1946 to later be used in patients. In this sense, the use of metallopharmaceuticals in cancer therapy was extensively explored until the 1960s with the discovery of cisplatin and its anticancer activity. From that date to the present, the search for more effective, more selective metallodrugs with fewer side effects has been an area of continuous exploration. Efforts have led to considering a wide variety of metals from the periodic table, mainly from the d-block, as well as a wide variety of organic ligands, preferably with proven biological activity. In this sense, various research groups have found an ideal binder in Schiff bases, since their raw materials are easily accessible, their synthesis conditions are friendly and their denticity can be manipulated. Therefore, in this review, we have explored the anticancer and antitumor activity reported in the literature for coordination complexes of d-block metals coordinated with tridentate Schiff bases (O N O and O N N) derived from salicylaldehyde. For this work, we have used the main scientific databases CCDC® and SciFinder®.

Lipoic Acid Restores Binding of Zinc Ions to Human Serum Albumin

Human serum albumin (HSA) is the main zinc(II) carrier in blood plasma. The HSA site with the strongest affinity for zinc(II), multi-metal binding site A, is disrupted by the presence of fatty acids (FAs). Therefore, the FA concentration in the blood influences zinc distribution, which may affect both normal physiological processes and a range of diseases. Based on the current knowledge of HSA’s structure and its coordination chemistry with zinc(II), we investigated zinc interactions and the effect of various FAs, including lipoic acid (LA), on the protein structure, stability, and zinc(II) binding. We combined NMR experiments and isothermal titration calorimetry to examine zinc(II) binding to HSA at a sub-atomic level in a quantitative manner as well as the effect of FAs. Free HSA results indicate the existence of one high-affinity zinc(II) binding site and multiple low-affinity sites. Upon the binding of FAs to HSA, we observed a range of behaviors in terms of zinc(II) affinity, depending on the type of FA. With FAs that disrupt zinc binding, the addition of LA restores HSA’s affinity for zinc ions to the levels seen with free defatted HSA, indicating the possible mechanism of LA, which is effective in the treatment of diabetes and cardiovascular diseases.

Designing biotin-human serum albumin nanoparticles to enhance the targeting ability of binuclear ruthenium(III) compound

On the one hand, to obtain a novel next-generation anticancer metal agent; on the other hand, to improve the targeting ability and decrease side effects of metal agent, we proposed to design active-targeting human serum albumin (HSA) nanoparticles (NPs) to achieve the end. Thus, we not only designed and synthesized two ruthenium (Ru) thiosemicarbazone compounds (C1 and C2) but also succeeded in constructing active Biotin-HSA NPs for Ru(III) compounds. Importantly, Biotin-HSA-C2 NPs not only possessed a stronger capacity for killing MCF-7 cells and inhibiting their migration versusC2 alone but also increased accumulation compared to non-malignant WI-38 cells. Additionally, C2 and Biotin-HSA-C2 NPs act against MCF-7 cells by the following potential mechanism: 1) arresting the cell cycle in the S phase by regulating cyclin and cyclin-dependent kinases; 2) inducing apoptosis by releasing cytochrome c to activate caspase-9/3; 3) inhibiting the expression of p-EGFR and regulating its neighboring cellular pathways, followed by the inactivation of PI3K/Akt and activation of p38 MAPK signaling pathways.

Synthesis of Amino Acid Schiff Base Nickel (II) Complexes as Potential Anticancer Drugs In Vitro

Three hexacoordinated octahedral nickel (II) complexes, [Ni (Trp-sal) (phen) (CH3OH)] (1), [Ni (Trp-o-van) (phen) (CH3OH)]•2CH3OH (2), and [Ni (Trp-naph) (phen) (CH3OH)] (3) (where Trp-sal = Schiff base derived from tryptophan and salicylaldehyde, Trp-o-van = Schiff base derived from tryptophan and o-vanillin, Trp-naph = Schiff base derived from tryptophan and 2-hydroxy-1-naphthaldehyde, phen = 1, 10-phenanthroline), have been synthesized and characterized as potential anticancer agents. Details of structural study of these complexes using single-crystal X-ray crystallography showed that distorted octahedral environment around nickel (II) ion has been satisfied by three nitrogen atoms and three oxygen atoms. All these complexes displayed moderate cytotoxicity toward esophageal cancer cell line Eca-109 with the IC50 values of 23.95 ± 2.54 μM for 1, 18.14 ± 2.39 μM for 2, and 21.89 ± 3.19 μM for 3. Antitumor mechanism studies showed that complex 2 can increase the autophagy, reactive oxygen species (ROS) levels, and decrease the mitochondrial membrane potential remarkably in a dose-dependent manner in the Eca-109 cells. Complex 2 can cause cell cycle arrest in the G2/M phase. Additionally, complex 2 can regulate the Bcl-2 family and autophagy-related proteins.

Interactions of Schiff base compounds and their coordination complexes with the drug cisplatin

There is a complex interplay between the structural and other physicochemical properties of new compounds and the molecules in living organisms.

Cytotoxic activity and structural features of Ru(II)/phosphine/amino acid complexes

Thirteen new ruthenium amino acid complexes were synthesized and characterized. They were obtained by the reaction of α-amino acids (AA) with [RuCl₂(P-P)(N-N)], where P-P=1,4-bis(diphenylphosphino)butane (dppb) or 1,3-bis(diphenylphosphino)propane (dppp) and N-N=4,4'-dimethyl-2,2'-bipyridine (4'-Mebipy), 5,5'-dimethyl-2,2'-bipyridine (5'-Mebipy) or 4,4'-Methoxy-2-2'-bipyridine (4'-MeObipy). This afforded a family of complexes formulated as [Ru(AA-H)(P-P)(N-N)]PF₆, where AA=glycine (Gly), L-alanine (Ala), L-valine (Val), L-tyrosine (Tyr), L-tryptophan (Trp), L-histidine (His) and L-methionine (Met). All compounds were characterized by elemental analysis, spectroscopic and electrochemical techniques. The [Ru(AA-H)(P-P)(N-N)]PF₆ complexes are octahedral (the AA-H ligand binding involves N-amine and O-carboxylate), diamagnetic (low-spin d⁶, S=0) and present bands due to electronic transitions in the visible region. ¹H, ¹³C{¹H} and ³¹P{¹H} NMR spectra of the complexes indicate the presence of C₂ symmetry, and the identification of diastereoisomers. In vitro cytotoxicity assays of the compounds and cisplatin were carried out using MDA-MB-231 (human breast) tumor cell line and a non-tumor breast cell line (MCF-10A). Most complexes present promising results with IC₅₀ values comparable with the reference drug cisplatin and high selectivity indexes were found for the complexes containing L-Trp. The binding of two Ru-precursors of the type [RuCl₂(dppb)(NN)] (N-N=4'-MeObipy or 4'-Mebipy) to the blood transporter protein human serum albumin (HSA) was evaluated by fluorescence and circular dichroism spectroscopy. Both complexes bind HSA, probably in the hydrophobic pocket near Trp214, and the Ru-complex containing 4'-MeObipy shows higher affinity for HSA than the 4'-Mebipy one.

Protein based therapeutic delivery agents: Contemporary developments and challenges

As unique biopolymers, proteins can be employed for therapeutic delivery. They bear important features such as bioavailability, biocompatibility, and biodegradability with low toxicity serving as a platform for delivery of various small molecule therapeutics, gene therapies, protein biologics and cells. Depending on size and characteristic of the therapeutic, a variety of natural and engineered proteins or peptides have been developed. This, coupled to recent advances in synthetic and chemical biology, has led to the creation of tailor-made protein materials for delivery. This review highlights strategies employing proteins to facilitate the delivery of therapeutic matter, addressing the challenges for small molecule, gene, protein and cell transport.