Singlet Oxygen Quantum Yield Determination for a Fluorene-Based Two-Photon Photosensitizer

Transurethral Resection of Non-Muscle Invasive Bladder Tumors Combined with Fluorescence Diagnosis and Photodynamic Therapy with Chlorin e6-Type Photosensitizers

Bladder cancer is a common disease with a high recurrence rate. In order to improve the treatment of superficial bladder tumors, we evaluated the efficacy and safety of transurethral resection (TURB) followed by fluorescence diagnosis (FD) and photodynamic therapy (PDT) with chlorin e6 photosensitizers (PSs), viz. "Fotoran e6" and "Fotoditazin". It was found that both PSs generated singlet oxygen and revealed moderate affinity toward the lipid-like compartment. Between November 2018 and October 2020, 12 patients with verified non-muscle invasive bladder cancer (NMIBC) were treated by TURB combined with FD and PDT. Eight patients received "Fotoran e6" intravenously, while four patients received intravesical PSs. The patient ages were between 31 and 79 years, with a median age of 64.5 years (mean 61.3 ± 14.2). The total light dose was 150 J/cm2 for the local irradiation of the tumor bed with a red light at the λ = 660 nm wavelength, and 10-25 J/cm2 were additionally delivered for diffuse irradiation of the entire bladder mucosa. At the median follow-up period of 24 months (mean 24.5 ± 5.4 months, range 16-35 months), 11 patients remained tumor-free. One 79-year-old patient developed a recurrence without progression to the muscle layer. This pilot study shows that the TURB + FD + PDT technique is an effective and safe option for the first-line treatment of superficial bladder tumors.

Porphyrin-Containing MOFs and COFs as Heterogeneous Photosensitizers for Singlet Oxygen-Based Antimicrobial Nanodevices

Visible-light irradiation of porphyrin and metalloporphyrin dyes in the presence of molecular oxygen can result in the photocatalytic generation of singlet oxygen (¹O₂). This type II reactive oxygen species (ROS) finds many applications where the dye, also called the photosensitizer, is dissolved (i.e., homogeneous phase) along with the substrate to be oxidized. In contrast, metal-organic frameworks (MOFs) are insoluble (or will disassemble) when placed in a solvent. When stable as a suspension, MOFs adsorb a large amount of O₂ and photocatalytically generate ¹O₂ in a heterogeneous process efficiently. Considering the immense surface area and great capacity for gas adsorption of MOFs, they seem ideal candidates for this application. Very recently, covalent-organic frameworks (COFs), variants where reticulation relies on covalent rather than coordination bonds, have emerged as efficient photosensitizers. This comprehensive mini review describes recent developments in the use of porphyrin-based or porphyrin-containing MOFs and COFs, including nanosized versions, as heterogeneous photosensitizers of singlet oxygen toward antimicrobial applications.

One- and Two-Photon Singlet Oxygen Generation with New Fluorene-Based Photosensitizers

The spectral properties of new fluorene-based photosensitizers for efficient singlet oxygen production are investigated at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives are measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation (phi(delta) and 2PAphi(delta), respectively), are determined by the direct measurement of singlet oxygen luminescence at approximately 1270 nm. The values of phi(delta) are independent of excitation wavelength, ranging from 0.6-0.9. The singlet oxygen quantum yields under two-photon excitation are 2PAphi(delta) approximately 1/2 phi(delta), indicating that the two processes exhibit the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.

Novel ruthenium(ii) and zinc(ii) complexes for two-photon absorption related applications

Two new fluorene derivatized 1,10-phenanthroline ligands and related tris-chelate Ru(II) or Zn(II) coordination complexes have been synthesised. The linear and nonlinear (two-photon induced fluorescence) photophysical measurements have contributed to highlight the possibility to tune the absorption spectral range and excited lifetime, depending on ligand substitution and nature of the metal. More significantly, the observation of two-photon absorption (TPA) associated with long-lived metal-to-ligand charge-transfer (MLCT) excited states in the Ru(II)-based chromophores, opens a wide range of applications in the near infrared.