Specific Activation of Photosensitizer with Extrinsic Enzyme for Precisive Photodynamic Therapy

Abstract

Delivery of functional proteins into the intracellular space has been a challenging task that could lead to a myriad of therapeutic applications. We report herein a novel bioconjugation strategy for enzyme modification and selective delivery into cancer cells for lock-and-key-type activation of photosensitizers. Using a bifunctional linker containing a bis­(bromomethyl)­phenyl group and an o-phthalaldehyde moiety, it could induce cyclization of the peptide sequence Ac-NH-CRGDfC-CONH2 through site-specific dibenzylation with the two cysteine residues and further coupling with β-galactosidase via the phthalaldehyde-amine capture reaction. This facile two-step one-pot procedure enabled the preparation of cyclic RGD-modified β-galactosidase readily, which could be internalized selectively into αvβ3 integrin-overexpressed cancer cells. Upon encountering an intrinsically quenched distyryl boron dipyrromethene-based photosensitizer conjugated with a galactose moiety through a self-immolative linker inside the cells, the extrinsic enzyme induced specific cleavage of the β-galactosidic bond followed by self-immolation to release an activated derivative, thereby restoring the photodynamic activities and causing cell death effectively. The high specificity of this extrinsic enzyme-activated photosensitizing system was also demonstrated in vivo using nude mice bearing an αvβ3 integrin-positive U87-MG tumor. The specific activation at the tumor site resulted in lighting up and complete eradication of the tumor upon laser irradiation, while by using the native β-galactosidase, the effects were largely reduced. In contrast to the conventional activation using intrinsic enzymes, this extrinsic enzyme activatable approach can further minimize the nonspecific activation toward precisive photodynamic therapy.

Selective photodynamic eradication of senescent cells with a β-galactosidase-activated photosensitiser

“…Recently, we have developed a novel strategy to modify β-gal with a cyclic RGD peptide and selectively deliver it into α v β 3 integrin-overexpressed cancer cells. 16 This extrinsic enzyme can activate a galactosyl distyryl boron dipyrromethene (BODIPY)-based photosensitiser inside the cells in a highly specific manner, effectively causing cell death and tumour eradication in nude mice. In this work, the target is cancer cells to which β-gal is delivered from an external source, again not senescent cells with intrinsic β-gal.…”

A pH-Responsive Drug Delivery System Based on Conjugated Polymer for Effective Synergistic Chemo-/Photodynamic Therapy

“…Recently, photodynamic therapy (PDT) has provided a promising perspective for anticancer treatments [ 4 , 5 , 6 ]. Compared with conventional therapy methods, PDT possesses unique advantages, such as high spatial selectivity, negligible system toxicity and the prevention of multidrug resistance [ 7 , 8 , 9 , 10 ]. In the non-invasive PDT process, a photosensitizer (PS) plays a key role in the light-induced generation of cytotoxic reactive oxygen species (ROS) to eliminate cancer cells or pathogenic bacteria [ 11 , 12 ].…”

Aptamer-Gold Nanocage Composite for Photoactivated Immunotherapy

“…Because of the capability of spatiotemporal control, photothermal therapy (PTT) could achieve precise therapy through light targeting. − We are convinced that the combination of aptamer therapy and PTT could solve the side effects of ICB fundamentally and enhance the antitumor efficacy.…”