Tuning the Organelle-Specific Imaging and Photodynamic Therapeutic Efficacy of Theranostic Mono- and Trinuclear Organometallic Iridium(III) Complexes

Cyclometalated Iridium(III) Complex with Substituted Benzimidazole: pH Directed Organelle-Specific Localization Within Lysosome

We report the synthesis and pH dependent emission spectral behaviour of four emissive iridium(III) complexes (Ir1-Ir4) with two isomeric pairs of bis-trifluoromethyl appended benzimidazole ligands. The imidazolyl hydrogen(N-H) has been replaced by phenyl groups (N-Ph) in two ligands to understand the impact of hydrogen bonding on the photophysical properties of the complexes and it indeed plays interesting role in the charge-transfer dynamics. The pH dependent electronic spectral change is observed for two of the complexes. The enhancement of emission intensity is observed at different wavelength for pH<7 and pH>7 for Ir1 and Ir3. The emission sensing of biogenic amines with pka values ranging from 5.80-9.74 is reported along with cellular imaging. The complex Ir1 specifically localizes within lysosome (pH=4.5-5) and thus image this organelle with great precision. The detail electronic spectra and electrochemical behaviour were reported here along with TDDFT results.

Transition Metal Complex-Loaded Nanosystems: Advances in Stimuli-Responsive Cancer Therapies

Transition metal complex-loaded nanosystems (TMCNs) represent a cutting-edge platform for stimuli (light, ultrasound)-responsive cancer therapies. These nanosystems, incorporating metals such as manganese(II), zinc(II), ruthenium(II), rhenium(I), iridium(III), and platinum(IV), significantly enhance the efficacy of light-activated therapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), as well as ultrasound-activated treatments like sonodynamic therapy (SDT). TMCNs based on ruthenium(II), rhenium(I), and iridium(III) improve PDT, while manganese(II) and iridium(III) demonstrate exceptional sonosensitizing properties. In PTT, ruthenium(II) and iridium(III)-based TMCNs efficiently absorb light and generate heat. Emerging synergistic approaches that combine SDT, PTT, PDT, chemotherapy, and immunotherapy are demonstrated to be powerful strategies for precision cancer treatment. Zinc(II), ruthenium(II), iridium(III), and platinum(IV)-based TMCNs play a critical role in optimizing these therapies, enhancing tumor targeting, and reducing side effects. Furthermore, TMCNs can amplify immunotherapy by inducing immunogenic cell death, thus strengthening the immune response. These advances address key challenges such as tumor hypoxia and therapeutic resistance, opening new possibilities for innovative photosensitizer-based cancer treatments. This review highlights the latest progress in TMCNs design and applications, demonstrating their potential to revolutionize stimuli-responsive cancer therapies.

Modulatory Role of Pantropic Cell Signaling Pathways in the Antimigratory and Antiproliferative Action of Triazole Chelated Iridium(III) Complexes in Cervical Cancer Cells

In the current study, the antimigratory and antiproliferative effect of three substituted triazole-chelated iridium(III) complexes Ir-TRN, Ir-TRH, and Ir-TRF were studied with special emphasis on modulation of P53 activity, a cell cycle regulator. ERK2/MAPK, another crucial cell signaling pathway protein, was also shown to play a crucial role in cell migration and proliferation. The complexes increase the ROS generation within the cell, further supporting apoptotic induction by exerting cellular oxidative stress. These metal complexes also affect ER stress by altering ERp29, an ER-resident chaperone, further inducing the process of apoptosis. The iridium(III) complexes restrict cervical cancer cell migration and proliferation by exerting pronounced effects as P53 activators and downregulation of ERK2/MAPK activity in cervical cancer cells. The underpinning mechanism of P53 and ERK2/MAPK activity in cervical cancer cells in the presence of iridium(III) complexes was studied in detail in this study, which paves the way for developing promising avenues for cancer therapeutics.

Application of Mono and Trinuclear Cyclometalated Iridium (III) Complexes in Differential Bacterial Imaging and Antimicrobial Photodynamic Therapy

The application of transition metal complexes for antimicrobial photodynamic therapy (PDT) has emerged as an attractive alternative in mitigating a broad range of bacterial pathogens, including multidrug-resistant pathogens. In view of their photostability, long excited-state lifetimes, and tunable emission properties, transition metal complexes also contribute as bioimaging agents. In the present work, we designed mono and trinuclear cyclometalated iridium (III) complexes to explore their imaging application and antibacterial potential. For this, we used Methicillin-resistant S. aureus (MRSA), the most prevalent of community-associated (CA) multidrug-resistant (MDR) bacteria (CA MDR) and Lactococcus lactis (L. lactis) as Gram-positive while Campylobacter jejuni (C. jejuni) and E. coli as Gram-negative bacteria. In addition to differential bioimaging of these bacteria, we assessed the antibacterial effects of both mono and trinuclear Ir(III) complexes under exposure to 427 nm LED light. The data presented herein strongly suggest better efficacy of trinuclear Ir(III) complex over the mononuclear complex in imparting photoinduced cell death of MRSA. Based on the safety profile of these complexes, we propose that trinuclear cyclometalated iridium(III) complex holds great promise for selective recognition and targeting MDR bacteria with minimal off-target effect.

Synergizing Nanomaterials and Artificial Intelligence in Advanced Optical Biosensors for Precision Antimicrobial Resistance Diagnosis

Antimicrobial resistance (AMR) poses a critical global One Health concern, ensuing from unintentional and continuous exposure to antibiotics, as well as challenges in accurate contagion diagnostics. Addressing AMR requires a strategic approach that emphasizes early stage prevention through screening in clinical, environmental, farming, and livestock settings to identify nonvulnerable antimicrobial agents and the associated genes. Conventional AMR diagnostics, like antibiotic susceptibility testing, possess drawbacks, including high costs, time-consuming processes, and significant manpower requirements, underscoring the need for intelligent, prompt, and on-site diagnostic techniques. Nanoenabled artificial intelligence (AI)-supported smart optical biosensors present a potential solution by facilitating rapid point-of-care AMR detection with real-time, sensitive, and portable capabilities. This Review comprehensively explores various types of optical nanobiosensors, such as surface plasmon resonance sensors, whispering-gallery mode sensors, optical coherence tomography, interference reflection imaging sensors, surface-enhanced Raman spectroscopy, fluorescence spectroscopy, microring resonance sensors, and optical tweezer biosensors, for AMR diagnostics. By harnessing the unique advantages of these nanoenabled smart biosensors, a revolutionary paradigm shift in AMR diagnostics can be achieved, characterized by rapid results, high sensitivity, portability, and integration with Internet-of-Things (IoT) technologies. Moreover, nanoenabled optical biosensors enable personalized monitoring and on-site detection, significantly reducing turnaround time and eliminating the human resources needed for sample preservation and transportation. Their potential for holistic environmental surveillance further enhances monitoring capabilities in diverse settings, leading to improved modern-age healthcare practices and more effective management of antimicrobial treatments. Embracing these advanced diagnostic tools promises to bolster global healthcare capacity to combat AMR and safeguard One Health.

Iridium(III)-based minor groove binding complexes as DNA photocleavage agents

Transition metal complexes containing the qtpy ligand (2':4,4'':4',4'''-quaterpyridyl) are known to be DNA intercalators or minor groove binders. In this study, new tricationic iridium(III) complexes of qtpy are reported. Both [Ir(bpy)2(qtpy)]3+1 and [Ir(phen)2(qtpy)]3+2 display good water solubility as chloride salts. The complexes possess high-energy excited states, which are quenched in the presence of duplex DNA and even by the mononucleotides guanosine monophosphate and adenosine monophosphate. Further studies reveal that although the complexes bind to quadruplex DNA, they display a preference for duplex structures, which are bound with an order of magnitude higher affinities than their isostructural dicationic RuII-analogues. Detailed molecular dynamics simulations confirm that the complexes are groove binders through the insertion of, predominantly, the qtpy ligand into the minor groove. Photoirradiation of 1 in the presence of plasmid DNA confirms that this class of complexes can function as synthetic photonucleases by cleaving DNA.