Stimuli‐Responsive Reversible Switching of Intersystem Crossing in Pure Organic Material for Smart Photodynamic Therapy

Abstract

Photosensitizers (PSs) with stimuli-responsive reversible switching of intersystem crossing (ISC) are highly promising for smart photodynamic therapy( PDT), but achieving this goal remains at remendous challenge.T his study introduces astrategy to obtain such reversible switching of ISC in an ew class of PSs,w hiche xhibit stimuli-initiated twisting of conjugated backbone.W ep resent am ultidisciplinary approachthat includes femtosecond transient absorption spectroscopyand quantum chemical calculations.The organic structures reported showr emarkably enhanced ISC efficiency (F ISC ), switching from nearly 0to90%,through an increase in the degree of twisting,p roviding an innovative mechanism to promote ISC.T his leads us to propose here and demonstrate the concept of smart PDT,w here pH-induced reversible twisting maximizes the ISC rate,a nd thus enables strong photodynamic action only under pathological stimulus (such as change in pH, hypoxia, or exposure to enzymes). The ISC process is turned off to deactivate PDT ability,when the PS is transferred or metabolized away from pathological region.

Manipulating Charge‐Transfer States in BODIPYs: A Model Strategy to Rapidly Develop Photodynamic Theragnostic Agents

“…Trying to overcome these drawbacks, some heavy‐atom‐free ROS‐PSs based on organic dyes have been reported recently . Although the origin of the photosensitizing capability in these dyes is still controversial, it has been suggested that structural distortion and charge‐transfer (CT) promotion upon the excitation could be involved in the enhanced probability of the ISC required to generate 1 O 2 (Figure ). In this context, promoting a charge‐transfer state (CTS) has been used recently to switch between fluorescence and ROS generation .…”

Elucidation of the Intersystem Crossing Mechanism in a Helical BODIPY for Low‐Dose Photodynamic Therapy

“…Efficient long‐wavelength heavy atom‐free triplet photosensitizers are rare (Table S3). In this study, we got inspiration from distorted conjugated systems, which display elevated ISC efficiency . In particular, the removal of the mirror‐plane symmetry of a planar π‐system is considered to allow for a stronger spin orbit coupling (SOC) between π–π* states with different spin manifolds (the singlet state and triplet state), hence facilitating ISC .…”

An Ultrasmall SnFe2O4 Nanozyme with Endogenous Oxygen Generation and Glutathione Depletion for Synergistic Cancer Therapy

“…photodynamic therapy (PDT) and photothermal therapy (PTT), has aroused wide attention on account of its unique advantages, such as deeper tissue penetration, negligible tissue injury, high efficiency, and specificity for cancer treatment. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Phototherapy also has its inevitable imperfection in spite of great progress achieved in the fields of PDT and PTT. For example, the hypoxia tumor microenvironment (TME) deteriorates the PDT efficiency and the heat shock response weakens the PTT effect.…”