Mechanistic Investigation into DNA Modification by a RuII ,RhIII Bimetallic Complex.

Despite significant progress in the treatment of cancer, there remains an urgent need for more effective therapies that also have less impact on patient wellbeing. Photodynamic therapy employs targeted light activation of a photosensitizer in selected tissues, thereby reducing off-target toxicity. Our group previously reported a RuII ,RhIII bimetallic architecture that displays multifunctional covalent photomodification of DNA in the therapeutic window in an oxygen-independent manner, features that are essential for treating deep and hypoxic tumors. Herein, we explore the mechanism by which a new analogue, [(phen)2 Ru(dpp)Rh(phen)Cl2 ]3+ , or RuII -RhIII , interacts with DNA. We established that RuII -RhIII exhibits "light switch" behavior in the presence of DNA, undergoing strong electrostatic interactions that might involve groove binding. Furthermore, these noncovalent interactions play a major role in the covalent photobinding and photocleavage of DNA, which occur according to an oxygen-independent mechanism. Polymerase chain reaction (PCR) revealed that covalent modification of DNA by RuII -RhIII , especially photobinding, is critical to inhibiting amplification, thus suggesting that the complex could exert its toxic activity by interfering with DNA replication in cells. This new structural motif, with phenanthroline at all three terminal ligand positions, has a number of properties that are promising for the continued refinement of photodynamic-therapy strategies.

Detecting Chronic Post-Traumatic Osteomyelitis of Mouse Tibia via an IL-13Rα2 Targeted Metallofullerene Magnetic Resonance Imaging Probe.

Differential diagnosis of chronic post-traumatic osteomyelitis (CPO) from aseptic inflammation remains challenging, since both pathological processes share similar clinical symptoms. Here we utilized a novel targeted metallofullerene nanoparticle based magnetic resonance imaging (MRI) probe IL-13-TAMRA-Gd3N@C80(OH)30(CH2CH2COOH)20 to detect CPO in mouse tibia via overexpressed IL-13Rα2 receptors. The functionalized metallofullerene was characterized by X-ray photoelectron spectroscopy. Upon lipopolysaccharide (LPS) stimulation, macrophage Raw 264.7 cells showed elevated IL-13Rα2 expression via immunofluorescence staining and increased MRI probe binding via built-in TAMRA fluorescence imaging. Trauma was induced in both tibia of mice and bacteria soaked suture was inserted into the right tibia to initiate infection. During the acute phase (1.5 weeks), luminol-bioluminescence imaging revealed much higher myeloperoxidase activity in the infected tibia compared to the sham. In the chronic phase (4 weeks), X-ray radiography illustrated bone deformation in the infected tibia compared to the sham. With T1 weighted sequences, the probe clearly exhibited hyperintensity in the infection foci at both acute and chronic phases, which was not observed in the sham tibia. Histological analysis revealed severe bone structural destruction and massive inflammatory cell infiltration in the infected tibia. Immunohistochemistry confirmed abundant expression of IL-13Rα2 in the infection site. In summary, we developed a noninvasive imaging approach to detect and differentiate CPO from aseptic inflammation using a new IL-13Rα2 targeted metallofullerene MRI probe. In addition, for the first time, IL-13Rα2 was investigated as a unique biomarker in the context of osteomyelitis. Our data established a foundation for the translational application of this MRI probe in the clinical differentiation of CPO.

Editorial for 'Issue focus on 2nd Costa Rica biophysics symposium - March 11th-12th, 2021'.

This Editorial describes both the motivation for, and the five articles appearing in, the Issue Focus dedicated to the 2nd Costa Rica Biophysics Symposium which was held in March 2021. Some recent history about both the symposium and developments in science occurring within Costa Rica is described.

Announcing the call for the Issue Focus on the 2nd Costa Rican Biophysics Symposium-virtual meeting, March 2021.

This Commentary is a call for submissions for the upcoming Issue Focus that will highlight some of the scientific topics discussed during the 2nd Costa Rica Biophysics Symposium.

Biogardens as constructed wetlands in tropical climate: A case study in the Central Pacific Coast of Costa Rica.

In Costa Rica, <10% of wastewater is treated before its discharge. This generates a significant impact on the environment, public health, and tourism industry, which is one of the country's main economic activities. Biogardens, subsurface flow artificial wetlands, are alternative systems for the treatment of wastewater. The present study evaluated the removal of organic matter and nutrients in a biogarden located at a hotel in the Central Pacific Coast of Costa Rica between 2012 and 2017. Pretreatment involved septic tanks and grease traps for sewage and gray water, respectively. The biogarden, which is composed of seven wetlands with an average area of 12 m2 and a depth of 0.7 m, contains river cobble as support material, gravel as bed, and Cyperus papyrus and Heliconia sp. plants. Removal of the biochemical oxygen demand (BOD), the chemical oxygen demand (COD), and the total suspended solids (TSS) on average were 80%, 66%, and 72%, respectively, thus producing an effluent in compliance with current national legislation. Furthermore, the biogarden did not emit noxious odors or display an excessive presence of mosquitoes. The results showed consistent and efficient removal of organic matter and nutrients from the wastewater throughout different seasons and pollutant loads, verifying that such systems can be used in decentralized locations (e.g., tourist areas) in tropical climates.

Resazurin Live Cell Assay: Setup and Fine-Tuning for Reliable Cytotoxicity Results.

In vitro cytotoxicity tests allow for fast and inexpensive screening of drug efficacy prior to in vivo studies. The resazurin assay (commercialized as Alamar Blue®) has been extensively utilized for this purpose in 2D and 3D cell cultures, and high-throughput screening. However, improper or lack of assay validation can generate unreliable results and limit reproducibility. Herein, we report a detailed protocol for the optimization of the resazurin assay to determine relevant analytical (limits of detection, quantification, and linear range) and biological (growth kinetics) parameters, and, thus, provide accurate cytotoxicity results. Fine-tuning of the resazurin assay will allow accurate and fast quantification of cytotoxicity for drug discovery. Unlike more complicated methods (e.g., mass spectrometry), this assay utilizes fluorescence spectroscopy and, thus, provides a less costly alternative to observe changes in the reductase proteome of the cells.

A new class of Ru(II) polyazine agents with potential for photodynamic therapy.

Appending anthracene units to [(bpy)2Ru(dpp)](2+) results in Ru(II) agents that exhibit dynamic photoreactivity towards DNA and protein. [(Anthbpy)(bpy)Ru(dpp)](2+) and [(Anthbpy)2Ru(dpp)](2+) are the first metal-organic Ru(II) agent with dpp ligands shown to photomodify DNA in the presence or absence of oxygen, while also binding protein in an oxygen-dependent manner.

Exploring the activity of a polyazine bridged Ru(ii)-Pt(ii) supramolecule in F98 rat malignant glioma cells.

The mixed-metal supramolecular complex, [(Ph2phen)2Ru(dpp)PtCl2]2+, displays significant DNA modification, cell growth inhibition, and toxicity towards F98 malignant glioma cells following visible light irradiation. The design of this complex affords superior cellular uptake and antiproliferative activity compared to the classic chemotherapeutic agent, cisplatin.