Colin G. Cameron

TLD1433 (Ruvidar®) is a Ru(II) polypyridyl complex currently in phase II clinical trials for the treatment of non-muscle invasive bladder cancer using photodynamic therapy (PDT). Previous studies have demonstrated that TLD1433 exhibits dual Type I/II photosensitization, arising from a combination of a prolonged intrinsic excited state lifetime and the redox-active α-terthienyl group, which together enable both singlet oxygen sensitization and light-driven redox processes. Despite this, molecular determinants contributing to its pronounced phototoxicity are still being elucidated. Herein, we investigated whether light-induced lipid membrane perturbation could represent a contributing photochemical property relevant to cytotoxic activity. To this end, all-atom molecular dynamics simulations and NMR experiments were employed to examine the insertion, partitioning, and residence of TLD1433 within a lipid bilayer in both dark and photoactivated states in normoxia and hypoxia, as well as the resulting effects on membrane structure integrity. Under normoxic conditions, oxidation events from the triplet excited state of TLD1433 promote localized accumulation of oxidized lipids and induce membrane deformations characterized by increased water penetration and transient pore-like features. In contrast, under low ROS-mediated lipid oxidation, membrane perturbations are more limited, although increased permeability and structural disorder are still observed. Taken together, these results suggest that light-induced lipid membrane perturbation, including poration, may represent a contributing factor to the phototoxic effects of TLD1433 under normoxic conditions. This combined computational and experimental study details how the photochemical properties of TLD1433 influence membrane response in a light- and oxygen-dependent manner, offering a framework for understanding how such effects may contribute to PDT efficacy at an unprecedented molecular level.

The ability to program excited-state pathways in Ru(II) polypyridyl complexes offers a powerful strategy for controlling phototherapeutic activity, yet how reliably such design principles translate across biological contexts remains unclear. In this work, we examine how systematic modulation of ligand structure alters excited-state accessibility and biological response across multiple test systems. Specifically, we investigate a complete series of oligothiophene-extended Ru(II) complexes, Ru(6,6′-dmb) ₂ (IP- n T) series ( n = 0–4), using spectroscopy, computation, photochemistry, and photobiology to define how oligothiophene length and coligand environment govern excited-state accessibility and biological response. Increasing oligothiophene chain length progressively suppresses photodissociative ³ MC pathways in favor of stabilized n T-centered ³ ILCT states. In mammalian cancer cells, only Ru-3T and Ru-4T exhibit light-dependent cytotoxicity, with Ru-4T emerging as the most effective compound under both normoxic and hypoxic conditions despite similar singlet-oxygen yields and triplet lifetimes. Antibacterial studies reveal additional biological constraints: while Ru-4T displays light-selective activity in Staphylococcus aureus , responses are attenuated in Enterococcus faecalis and absent in Gram-negative bacteria. Preliminary in vivo tolerability studies show that Ru-4T is well tolerated and exhibits reduced systemic toxicity relative to related analogues. Together, these results demonstrate that stabilized ILCT-based excited states, rather than ³ MC-driven photochemistry, underpin productive phototherapeutic activity in this family of compounds, while biological context ultimately defines the limits of predictability for excited-state design.

Ruthenium(II) polypyridyl complexes can be harnessed for photodynamic therapy. In this work, diprotic ligands which can be deprotonated to change the metal complexes from dicationic to neutral are combined with extended π systems for light absorption at longer wavelengths. Herein, the diprotic ligands are 4,4′-dhbp = 4,4′-dihydroxybipyridine or 4,7-dhphen = 4,7-dihydroxy-1,10-phenanthroline and the π-expanded ligands are bphen = bathophenanthroline, dppz = dipyrido[3,2-a:2′,3′-c]phenazine, and dppn = benzodipyrido[3,2-a:2′,3′-c]phenazine. This report describes the synthesis and characterization of [(bphen)₂Ru(4,4′-dhbp)]Cl₂ (1_A), [(dppz)₂Ru(4,4′-dhbp)]Cl₂ (2_A), [(dppn)₂Ru(4,4′-dhbp)]Cl₂ (3_A), [(bphen)₂Ru(4,7-dhphen)]Cl₂ (4_A), [(dppz)₂Ru(4,7-dhphen)]Cl₂ (5_A), and [(dppn)₂Ru(4,7-dhphen)]Cl₂ (6_A). Single crystal X-ray diffraction data are reported for 1_A, 2_A, and two known precursor compounds: [(ղ⁶-p-cymene)RuCl(diprotic ligand)]Cl (P1, P2 where diprotic ligand = 4,4′-dhbp and 4,7-dhphen, respectively). Compounds 1_A-6_A have been studied for their photocytotoxicity vs. breast and melanoma cancer cells, lipophilic vs. hydrophilic properties, thermodynamic acidities (pK_a values), singlet oxygen quantum yields, and luminescence which is heavily influenced by the nature of the π expanded ligand. Four compounds (bearing bphen and dppn ligands) have promising photocytotoxicity including activity with green light and one compound has a phototherapeutic index (PI) as high as 145.

Controlling the aggregation of amyloid-β (Aβ) peptides offers a promising strategy to mitigate Alzheimer's disease (AD). Herein, we introduce a series of photoactivatable Ru(II) complexes (Ru1-8) designed to efficiently generate singlet oxygen (¹O₂) and subsequently oxidatively modify the Aβ peptide. Upon light activation, these complexes rapidly direct Aβ_1-42 aggregation toward high molecular weight amorphous species, with Ru1 demonstrating the most pronounced effect. Transmission electron microscopy (TEM) revealed that the amorphous aggregates formed immediately and persist over time. Complementary assays, including bicinchoninic acid (BCA) quantification and Western blotting, demonstrated rapid photoinduced aggregation and a decrease of soluble peptide upon photoactivation, while proteinase-K digestion showed that the resulting amorphous species are more susceptible to proteolysis in comparison to canonical fibrils. Control experiments under anaerobic conditions and in the presence of an ¹O₂ scavenger suggest that these effects are oxygen-dependent. Notably, photoactivation of Ru1 in the presence of preformed fibrils results in a morphology change to degradable amorphous aggregates, providing both preventive and disruptive activity. Together, these findings establish photoactivatable Ru1 as a light-controlled chemical tool capable of redirecting Aβ aggregation, enhancing aggregate protease degradation, and offering a versatile platform for therapeutic exploration.

Six bis-terpyridine Ru(II) and Os(II) complexes (nT-Ru/Os, n = 2-4) incorporating oligothienyl-substituted terpyridines were synthesized and compared with analogous Ir(III) complexes to evaluate how metal centers and thienyl substitution affect photophysics and photodynamic therapeutic (PDT) activity against SKMEL28 melanoma and MDA-MB-231 breast cancer cells under normoxia and hypoxia. Increasing thienyl groups induced bathochromic shifts in absorption, with nT-Ru/Os displaying more intense, narrower, and red-shifted bands than nT-Ir; nT-Os also showed a broad 600-750 nm band. All complexes emitted near-IR phosphorescence with triplet lifetimes of 0.12-47.5 μs and produced singlet oxygen (Φ_Δ = 0.13-0.84). Generally, nT-Ir/Ru gave higher Φ_Δ than nT-Os, though 4T-Os matched 4T-Ir under green light irradiation. In vitro, all complexes exhibited minimal dark cytotoxicity but strong photocytotoxicity under broadband visible, blue, green, or red-light activation, except 2T-Ir, which was red-inactive. Importantly, 3T-Ir, 4T-Ir, and 4T-Ru maintained phototoxicity toward SKMEL28 cells under hypoxia, and 2T-Ru-4T-Ru toward MDA-MB-231 cells. Notably, 4T-Ru retained strong red-light activity under hypoxia against both cell lines. Mechanistic studies suggest that singlet oxygen, superoxide, and peroxynitrite contribute to activity. These findings highlight nT-Ru/Os/Ir complexes as promising PDT agents with distinct photophysical tunability and hypoxia resilience.

IPG K ⁺ chemosensors are effective for Ba ²⁺ detection in aqueous solution and low-background single-ion fluorescence microscopy.

Phototherapy approaches include photodynamic therapy (PDT), which utilizes chemically stable photocatalysts to sensitize the conversion of endogenous molecules such as oxygen (O ₂ ) to form transient reactive species such as ¹ O ₂ , and photopharmacology, a complementary approach that relies on molecules that undergo self‐modifying photochemistry, such as bond cleavage reactions or isomerization, for the creation of biologically active products. While Ru(II) polypyridyl systems have demonstrated utility for both approaches, related organometallic systems are relatively less explored. Here, the photochemistry and photobiological responses were compared for five Ru(II) arene compounds containing photolabile monodentate azine ligands and the π‐expansive bidentate ligands dipyrido[3,2‐a:2′,3′‐c]phenazine (dppz), 4,5,9,16‐tetraaza‐dibenzo[a,c]naphthacene (dppn), and α‐terthienyl‐appended imidazo[4,5‐ f ][1,10]phenanthroline (IP‐3T). The compounds demonstrated significant light‐mediated photocytotoxicity in lung cancer and melanoma cell lines, with up to 6000‐fold increases in cytotoxicity upon irradiation. The arene systems were capable of partitioning between different excited state relaxation pathways, both releasing the monodentate ligand and generating ¹ O ₂ , but with notably low yields that did not correlate with the photocytotoxicity of the systems. The organometallic compounds exhibit less mixing of the metal‐associated and ligand‐centered excited states than analogous polypyridyl coordination compounds, providing a structurally, photochemically, and photobiologically distinct class of compounds that can support both metal‐ and ligand‐centered reactivity.

In an effort to develop hypoxia-active iridium(III) complexes with long visible-light absorption, we synthesized and characterized five bis(terpyridine) Ir(III) complexes bearing oligothienyl substituents on one of the terpyridine ligands, i.e., nT-Ir (n = 0-4). The UV-vis absorption, emission, and transient absorption spectroscopy were employed to characterize the singlet and triplet excited states of these complexes and to explore the effects of varied number of thienyl units on the photophysical parameters of the complexes. In vitro photodynamic therapeutic activities of these complexes were assessed with respect to three melanoma cell lines (SKMEL28, A375, and B16F10) and two breast cancer cell lines (MDA-MB-231 and MCF-7) under normoxia (∼18.5% oxygen tension) and hypoxia (1% oxygen tension) upon broadband visible (400-700 nm), blue (453 nm), green (523 nm), and red (633 nm) light activation. It was revealed that the increased number of thienyl units bathochromically shifted the low-energy absorption bands to the green/orange spectral regions and the emission bands to the near-infrared (NIR) regions. The lowest triplet excited-state lifetimes and the singlet oxygen generation efficiency also increased from 0T to 2T substitution but decreased in 3T and 4T substitution. All complexes exhibited low dark cytotoxicity toward all cell lines, but 2T-Ir-4T-Ir manifested high photocytotoxicity for all cell lines upon visible, blue, and green light activation under normoxia, with 2T-Ir showing the strongest photocytotoxicity toward SKMEL28, MDA-MB-231, and MCF-7 cells, and 4T-Ir being the most photocytotoxic one for B16F10 and A375 cells. Singlet oxygen, superoxide anion radicals, and peroxynitrite anions were found to likely be involved in the photocytotoxicity exhibited by the complexes. 4T-Ir also showed strong photocytotoxicity upon red-light excitation toward all cell lines under normoxia and retained its photocytotoxicity under hypoxia toward all cell lines upon visible, blue, and green light excitation. The hypoxic activity of 4T-Ir along with its green to orange light absorption, NIR emission, and low dark cytotoxicity suggest its potential as a photosensitizer for photodynamic therapy applications.

Cetuximab (Cet)-IRDye800CW, among other antibody-IRDye800CW conjugates, is a potentially effective tool for delineating tumor margins during fluorescence image-guided surgery (IGS). However, residual disease often leads to recurrence. Photodynamic therapy (PDT) following IGS is proposed as an approach to eliminate residual disease but suffers from a lack of molecular specificity for cancer cells. Antibody-targeted PDT offers a potential solution for this specificity problem. In this study, we show, for the first time, that Cet-IRDye800CW is capable of antibody-targeted PDT in vitro when the payload of dye molecules is increased from 2 (clinical version) to 11 per antibody. Cet-IRDye800CW (1:11) produces singlet oxygen, hydroxyl radicals, and peroxynitrite upon activation with 810 nm light. In vitro assays on FaDu head and neck cancer cells confirm that Cet-IRDye800CW (1:11) maintains cancer cell binding specificity and is capable of inducing up to ∼90% phototoxicity in FaDu cancer cells. The phototoxicity of Cet-IRDye800CW conjugates using 810 nm light follows a dye payload-dependent trend. Cet-IRDye800CW (1:11) is also found to be more phototoxic to FaDu cancer cells and less toxic in the dark than the approved chromophore indocyanine green, which can also act as a PDT agent. We propose that antibody-targeted PDT using high-payload Cet-IRDye800CW (1:11) could hold potential for eliminating residual disease postoperatively when using sustained illumination devices, such as fiber optic patches and implantable surgical bed balloon applicators. This approach could also potentially be applicable to a wide variety of resectable cancers that are amenable to IGS-PDT, using their respective approved full-length antibodies as a template for high-payload IRDye800CW conjugation.