A Thioacetal Photocage Designed for Dual Release: Application in the Quantitation of Therapeutic Release by Synchronous Reporter Decaging

Abstract

Despite the immense potential, application of existing photocaging technology is limited by the paucity of advanced caging tools. Here we report on the design of a novel thioacetal ortho-nitrobenzaldehyde (TNB) dual arm photocage that enables control of the simultaneous release of two payloads linked to a single TNB unit. Using this cage which was prepared in a single step from commercial 6-nitroverataldehyde, three drug-fluorophore conjugates were synthesized, Taxol-TNB-Fluorescein, Taxol-TNB-Coumarin and Doxorubicin-TNB-Coumarin, and long wavelength UVA light-triggered release experiments demonstrated that dual payload release occurred with rapid decay kinetics for each conjugate. In cell based assays in vitro, dual release could also be controlled by UV exposure, resulting in increased cellular fluorescence and cytotoxicity as potent as unmodified drug towards the KB carcinoma cell line. The extent of such dual release was quantifiable by reporter fluorescence measured in situ, and found to correlate with the extent of cytotoxicity. Thus, this novel dual-arm cage strategy provides a valuable tool which enables both active control and real-time monitoring of drug activation at the delivery site.

Photocontrolled Release of Doxorubicin Conjugated through a Thioacetal Photocage in Folate-Targeted Nanodelivery Systems

“…were fully established by 1 H NMR spectroscopy and ultraperformance liquid chromatography (UPLC) analysis ( Figure S1, Supporting Information). Some of these compounds were further characterized by UV-vis spectrometry (5:  max = 498 nm (Dox),  = 7882.7 M −1 × cm −1 ); 355 nm (TNB),  = 4575.4 M −1 × cm −1 ) and by high resolution mass spectral data which confirmed an agreement between the calculated and experimental values (m/z calcd for C 48…”

“…1 TNB(OH) was synthesized from 6-nitroveratraldehyde by its reaction with 2-mercaptoethanol in a one-pot synthesis catalyzed by BF 3 •Et 2 O as reported previously (Scheme 1). 48 Each hydroxyl group in 1 was then activated by treatment with 4nitrophenyl (4-NP) chloroformate to an amine-reactive form, bis(4-nitrophenyl) carbonate 3.…”

“…With a practical perspective, to address these synthetic challenges in photocaging technologies, we have been interested in thioacetal ortho-nitrobenzaldehyde (TNB) 48 as a new type of photolinker ( Figure 2). As reported recently from our laboratories, 48 each TNB linker (1 and 2) has a photocaging group flanked by two identical arms. Because of their symmetry, each hydroxyl or carboxylic acid terminus can equally engage in either drug caging or NP tethering without incurring regioisomeric issues.…”

“…44 Both TNB and ONB share certain similarities in the initial step of the mechanism of cleavage which involves the generation of an aci-Nitro form in response to UV light ( Figure 2). 48 However, they show differences in subsequent fragmentation mechanisms and the distribution of release products as the TNB cleavage results in concomitant release of two species, proposed to be Dox(thiol) and Dox(thioester).…”

Bis‐Acetyl Carbazole: A Photoremovable Protecting Group for Sequential Release of Two Different Functional Groups and Its Application in Therapeutic Release

“…PRPGs based on a single chromophore for dual release are less in number than single release PRPGs . Known examples of single chromophore‐based PRPGs for dual release are thioacetal ortho ‐nitrobenzaldehyde (TNB), 3‐diethylaminobenzyl (DEABn), perylene‐3,4,9,10‐tetrayltetramethyl, and bimane …”