Boron clusters are polyhedral boron hydrides with unique properties, and they are becoming increasingly widely used in biology and medicine, including for boron neutron capture therapy (BNCT) of cancers and in the design of novel bioactive molecules and potential drugs. Among boron cluster types, icosahedral boranes, carboranes, and metallacarboranes are particularly interesting, and there is a need for basic studies on their interaction with biologically important molecules, such as proteins. Herein, we report studies on the interaction of selected boron clusters and their derivatives with serum albumin, the most abundant protein in mammalian blood. The interaction of boron clusters with albumin was examined by fluorescence quenching, circular dichroism, dynamic and static light scattering measurements and MALDI-TOF mass spectrometry. Our results showed that metallacarboranes have the strongest interaction with albumin among the tested clusters. The observed strength of boron cluster interactions with albumin decreases in order: metallacarboranes [M(C₂B₉H₁₁)₂]⁻> carboranes (C₂B₁₀H₁₂) >> dodecaborate anion [B₁₂H₁₂]²⁻. Metallacarboranes first specifically interact with the binding cavity of albumin and then, with increasing compound concentrations, interact non-specifically with the protein surface. These findings can be of importance and are useful in the development of new bioactive compounds that contain boron clusters.

At present, effective anticancer therapy remains one of the most challenging tasks facing the scientific community. A major limitation to most conventional low‐molecular weight anticancer chemotherapeutics is their unfavourable uptake by healthy tissue, fast metabolism and lack of tumour cell selectivity. One way to solve this problem is the application of hybrid nanoparticles containing widely known therapeutic substances. This study was performed with the aim of investigating the potential of use hydroxyethyl starch (HES) as a high‐molecular weight carrier for anticancer drug (methotrexate, MTX). HES‐MTX conjugates were characterized in terms of MTX content, hydrodynamic size, zeta potential, and drug release kinetics. In vitro biological characteristics were determined using different cancer cell lines. The antitumor effect in vivo was tested in NOD/SCID mice subcutaneously inoculated with MV‐4‐11 human leukaemia cells and CDF1 mice intraperitoneally inoculated with P388 murine leukaemia cells. The in vivo experiments revealed the considerably higher antitumor efficacy of HES‐MTX conjugates in comparison to unconjugated drug. The results presented in this article demonstrate that the application of HES as an anticancer drug carrier can improve the treatment efficacy and have significant implications for the future design and implementation of drug‐carrier conjugates. The study should help create new opportunities in the design of HES‐based innovative drug‐carrier conjugates.

Pseudomonas aeruginosa is an opportunistic human pathogen that has become a nosocomial health problem worldwide. The pathogen has multiple drug removal and virulence secretion systems, is resistant to many antibiotics, and there is no commercial vaccine against it. Yersinia pestis is a zoonotic pathogen that is on the Select Agents list. The bacterium is the deadliest pathogen known to humans and antibiotic-resistant strains are appearing naturally. There is no commercial vaccine against the pathogen, either. In the current work, novel compounds based on metallacarborane cage were studied on strains of Pseudomonas aeruginosa and a Yersinia pestis substitute, Yersinia enterocolitica. The representative compounds had IC₅₀ values below 10 µM against Y. enterocolitica and values of 20–50 μM against P. aeruginosa. Artificial generation of compound-resistant Y. enterocolitica suggested a common mechanism for drug resistance, the first reported in the literature, and suggested N-linked metallacarboranes as impervious to cellular mechanisms of resistance generation. SEM analysis of the compound-resistant strains showed that the compounds had a predominantly bacteriostatic effect and blocked bacterial cell division in Y. enterocolitica. The compounds could be a starting point towards novel anti-Yersinia drugs and the strategy presented here proposes a mechanism to bypass any future drug resistance in bacteria.

Introduction: Icosahedral boron clusters have unique properties useful in medicinal chemistry: rigidity, chemical stability, and three-dimensional aromaticity. Furthermore, these abiotic compounds have low toxicity and are stable in the biological environment. All these features ultimately give them the ability to interact with biological molecules in a different mode than organic compounds. Areas covered: In the present article, we aim to introduce boron clusters as a class of entities suitable for modifications of biomolecules to obtain a specific biological effect. We will focus on icosahedral boron clusters, as well as metallacarboranes, and their biological activity and interaction with the biological environment. Expert opinion: Boron clusters are suitable for altering structural and functional features of biomolecules and can be used in the development of new drugs and drug delivery systems. The high affinity of boron clusters, especially metallacarboranes, to albumin creates a new possibility to use them to optimize the pharmacokinetics of biologically active peptides. Boron clusters have high potential in biological and medicinal applications. Due to their peculiar properties, they can be used to optimize parameters critical for the biological activity of therapeutic substances and their affinity toward biological targets.