8-Br-quinoline derivatives as sensitizers combining two-photon induced fluorescence and singlet oxygen generation

The Quinoline Photoremovable Group (PPG) Platform-A Medicinal Chemist's Approach for Photocage Development and Applications

Photoremovable protecting groups (PPGs) offer a straightforward solution for the temporary inactivation of biologically active substrates and their subsequent controlled release by light irradiation. Their relatively easy design and mode of application have made them useful tools for studying dynamic biological processes in vitro and in vivo. Recently, there has been a growing body of data investigating their potential application in the development of drug delivery systems. Of the various PPG scaffolds in use, quinoline photocages have a history of about 20 years. The structure-property relationships of quinoline PPGs, as well as alternative multibranch designs based on quinoline monomers have been thoroughly studied both experimentally and theoretically. Therefore, quinoline PPGs serve as a representative study of PPG development, showing how the various applications of quinoline photocages followed the chemical optimization or how the applications drove the chemical design. Since the raison d'être of PPGs lies in their application for light-activated release of various substrates or performing light-activated structural changes in materials, it is crucial to understand how PPGs are selected and utilized by their end-users, who are often not chemists themselves. Therefore, we discuss whether the conclusions drawn from the selected quinoline PPG family could lead to more general insights for the field as whole. As PPG-related applications still rely heavily on a limited number of chemical scaffolds, it is worth considering, what could be the reasons for the slow uptake of novel chemical scaffolds.

Reversal of Reactivity of Heyns Intermediate for the Concise Synthesis of Substituted 3-Hydroxyquinolines

An efficient and general method for the synthesis of 3-hydroxyquinolines has been achieved from o-acylanilines and α-hydroxyketones in good yields. The strategy involves the intramolecular reverse trapping of the in situ generated aminoenol intermediate with an electrophilic carbonyl, viz. an interrupted Heyns rearrangement, followed by aromatization. Important features include good functional group tolerance, operational simplicity, gram-scale synthesis, and broad synthetic utility.

Achiral Sm(III)-Based Metal-Organic Framework as a Luminescence Sensor for Enantiodiscrimination of Quinine and Quinidine

The effective discrimination and determination of the chiral antimalarial drugs quinine (QN) and quinidine (QD) are extremely important for human health. Herein, a 2D achiral Sm-based metal-organic framework (IMU-MOF1 = [Sm(tpba)(L)]n, where Htpba = 4-(2,2':6″,2'-terpyridin)-4'-ylbenzioc acid and H2L = 2,2'-biquinoline-4,4'-dicarboxylic acid) was successfully prepared by the solvothermal method. More importantly, IMU-MOF1 was designed as an ultrasensitive fluorescent probe for the identification of chiral enantiomer drugs. The limits of detection for QN and QD are 4.24 × 10-11 and 7.54 × 10-12 M, respectively. Furthermore, it was demonstrated that the stronger hydrogen-bonding interactions between IMU-MOF1 and quinine furnish a more efficient energy transfer to the ligands in the sensing process, resulting in a significant fluorescence enhancement of IMU-MOF1.

Two-Photon-Excited Silica and Organosilica Nanoparticles for Spatiotemporal Cancer Treatment

Coherent two-photon-excited (TPE) therapy in the near-infrared (NIR) provides safer cancer treatments than current therapies lacking spatial and temporal selectivities because it is characterized by a 3D spatial resolution of 1 µm³ and very low scattering. In this review, the principle of TPE and its significance in combination with organosilica nanoparticles (NPs) are introduced and then studies involving the design of pioneering TPE-NIR organosilica nanomaterials are discussed for bioimaging, drug delivery, and photodynamic therapy. Organosilica nanoparticles and their rich and well-established chemistry, tunable composition, porosity, size, and morphology provide ideal platforms for minimal side-effect therapies via TPE-NIR. Mesoporous silica and organosilica nanoparticles endowed with high surface areas can be functionalized to carry hydrophobic and biologically unstable two-photon absorbers for drug delivery and diagnosis. Currently, most light-actuated clinical therapeutic applications with NPs involve photodynamic therapy by singlet oxygen generation, but low photosensitizing efficiencies, tumor resistance, and lack of spatial resolution limit their applicability. On the contrary, higher photosensitizing yields, versatile therapies, and a unique spatial resolution are available with engineered two-photon-sensitive organosilica particles that selectively impact tumors while healthy tissues remain untouched. Patients suffering pathologies such as retinoblastoma, breast, and skin cancers will greatly benefit from TPE-NIR ultrasensitive diagnosis and therapy.

Fluorescent periodic mesoporous organosilica nanoparticles dual-functionalized via click chemistry for two-photon photodynamic therapy in cells

The synthesis of ethenylene-based periodic mesoporous organosilica nanoparticles for two-photon imaging and photodynamic therapy of breast cancer cells is described.