Frédéric Bolze

Two-photon-excitable profluorogenic probes capable of undergoing bioorthogonal reactions in complex biological media remain exceedingly rare, despite their tremendous potential for live-cell imaging.

Photodynamic therapy is a non-invasive treatment strategy for various types of cancer, based on the use of light to activate a photosensitizer which triggers processes leading to cell death. Given the increasing interest in the development of mitochondria-targeted photosensitizers, in this study we synthesized two novel thiadiazol-substituted porphyrins, 5,10,15,20-tetra(2,1,3-benzothiadiazol-5-yl) porphyrin (C1) and 5,10,15,20-tetra(1,2,3-thiadiazol-4-yl) porphyrin (C2), designed to target mitochondria in cancer cells thanks to the azole residues present in their structure. The two porphyrinic compounds were characterized in terms of structural and photophysical properties, revealing high yields of singlet oxygen production. Their interaction with biological structures was analyzed in a triple-negative human breast carcinoma cell line (MDA-MB-231), either as free compounds or delivered via mitochondriotropic liposome formulations. Both newly synthesized porphyrins entered MDA-MB-231 cells, with compound C2 demonstrating more efficient localization in the cytoplasm and in mitochondria. Dark and phototoxicity tests were also performed: both compounds proved to be effective phototoxic agents, with C2 showing the highest activity, making it a promising photosensitizer for mitochondria-targeted photodynamic therapy.

We synthesized new para-dialkylaminonitrobiphenyl (ANBP) derivatives, s-ANBP and t-ANBP, functionalized with dimethyltrityl and phosphoramidite groups for incorporation into DNA backbones as photocleavable linkers via solid-phase synthesis. Both derivatives exhibited excellent chemical stability under diverse conditions, including acidic, alkaline, and high-salt environments and elevated temperatures. Their incorporation into DNA influenced duplex stability and antisense oligonucleotide (ASO) dissociation efficiency, depending on the number of ANBP units and adjacent nucleotide deletions. The s-/t-ANBP-conjugated DNA showed efficient one-photon photolysis at 415 nm and enhanced two-photon absorption for extended π-system in t-ANBP, with δ_uΦ_u values of 1.6 GM (740 nm) and 2.7 GM (800 nm). ANBP-conjugated DNA was used to construct a 3D DNA nanocage capable of light-triggered ASO 4625 release, validated by an in vitro RNA digestion assay, confirming antisense functionality. This platform demonstrates precise, light-mediated therapeutic delivery and offers potential for broader applications in drug delivery and clinical use.

Four BODIPY dyes (6a–6d) with electron-donating or electron-withdrawing groups at the meso-position were synthesized by the Sonogashira coupling reaction of 2,5-diethynylthieno[3,2-b]thiophene with mono-iodo-BODIPY moieties.

The emerging field of photopharmacology is a promising chemobiological methodology for optical control of drug activities that could ultimately solve the off‐target toxicity outside the disease location of many drugs for the treatment of a given pathology. The use of photolytic reactions looks very attractive for a light‐activated drug release but requires to develop photolytic reactions sensitive to red or near‐infrared light excitation for better tissue penetration. This review will present the concepts of triplet‐triplet annihilation upconversion‐based photolysis and their recent in vivo applications for light‐induced drug delivery using photoactivatable nanoparticles.

Fluorogenic bioorthogonal reactions are promising tools for tracking small molecules or biomolecules in living organisms. Two-photon excitation, by shifting absorption towards the red, significantly increases the signal-to-noise ratio and decreases photodamage, while allowing imaging about 10 times deeper than with a confocal microscope. However, efficient two-photon excitable fluorogenic probes are currently lacking. We report here the design and synthesis of fluorogenic probes based on a two-photon excitable fluorophore and a tetrazine quenching moiety. These probes react with bicyclo[6.1.0]no-4-yn-9ylmethanol (BCN) with a good to impressive kinetic rate constant (up to 1.1 × 10³ M⁻¹ s⁻¹) and emit in the red window with moderate to high turn-on ratios. TDDFT allowed the rationalization of both the kinetic and fluorogenic performance of the different probes. The best candidate displays a 13.8-fold turn-on measured by quantifying fluorescence intensities in live cells under one-photon excitation, whereas a value of 3 is sufficient for high contrast live-cell imaging. In addition, live-cell imaging under two-photon excitation confirmed that there was no need for washing to monitor the reaction between BCN and this probe since an 8.0-fold turn-on was measured under two-photon excitation. Finally, the high two-photon brightness of the clicked adduct (>300 GM) allows the use of a weak laser power compatible with in vivo imaging.

Liposome-based nanoparticles able to release, via a photolytic reaction, a payload anchored at the surface of the phospholipid bilayer were prepared. The liposome formulation strategy uses an original drug-conjugated blue light-sensitive photoactivatable coumarinyl linker. This is based on an efficient blue light-sensitive photolabile protecting group modified by a lipid anchor, which enables its incorporation into liposomes, leading to blue to green light-sensitive nanoparticles. In addition, the formulated liposomes were doped with triplet-triplet annihilation upconverting organic chromophores (red to blue light) in order to prepare red light sensitive liposomes able to release a payload, by upconversion-assisted photolysis. Those light-activatable liposomes were used to demonstrate that direct blue or green light photolysis or red light TTA-UC-assisted drug photolysis can effectively photorelease a drug payload (Melphalan) and kill tumor cells in vitro after photoactivation.

Fluorogenic bioorthogonal reactions are promising tools for tracking small molecules or biomolecules in living organisms. Two-photon excitation, by shifting absorption towards the red, significantly increases the signal-to-noise ratio and decreases photodamages, while allowing to image about 10 times deeper than with a confocal. However, efficient two-photon excitable fluorogenic probes are currently lacking. We report here the design and synthesis of fluorogenic probes based on a two-photon excitable fluorophore and a tetrazine quenching moiety. These probes react with bicyclo[6.1.0]no-4-yn-9yl)methanol (BCN) with good to impressive kinetic rate constant (up to 1.1x103 M-1.s-1) and emit in the red window with moderate to high turn-on. TDDFT allowed to rationalize both the kinetic and fluorogenic performance of the different probes. The best candidate displays a turn-on of 13.8-fold measured by fluorescence intensities quantification in living cells under one-photon excitation, whereas a value of 3 is enough for live-cell imaging with high contrast. Moreover, live-cell imaging under two-photon excitation confirmed that there was no need for washing to monitor the reaction between BCN and this probe as a turn-on of 8.0-fold was measured under two-photon excitation. Finally, the high two-photon brightness of the clicked adduct (>300 GM) allows the use of a weak laser power compatible with in vivo imaging.

In this study, we synthesized two phosphoramidites based on 2,7-bis-{4-nitro-8-[3-(2-propyl)-styryl]}-9,9-bis-[1-(3,6-dioxaheptyl)]-fluorene (BNSF) and 4,4'-bis-{8-[4-nitro-3-(2-propyl)-styryl]}-3,3'-di-methoxybiphenyl (BNSMB) structures as visible light-cleavable linkers for oligonucleotide conjugation. In addition to the commercial ultraviolet (UV) photocleavable (PC) linker, the BNSMB linker was further applied as a building component to construct photoregulated DNA devices as duplex structures, which are functionalized with fluorophores and quenchers. Selective cleavage of PC and BNSMB is achieved in response to ultraviolet (UV) and visible light irradiations as two inputs, respectively. This leads to controllable dissociation of pieces of DNA fragments, which is followed by changes of fluorescence emission as signal outputs of the system. By tuning the number and position of the photocleavable molecules, fluorophores, and quenchers, various DNA devices were developed, which mimic the functions of Boolean logic gates and achieve logic operations in AND, OR, NOR, and NAND gates in response to two different wavelengths of light inputs. By sequence design, the photolysis products can be precisely programmed in DNA devices and triggered to release in a selective and/or sequential manner. Thus, this photoregulated DNA device shows potential as a wavelength-dependent drug delivery system for selective control over the release of multiple individual therapeutic oligonucleotide-based drugs. We believe that our work not only enriches the library of photocleavable phosphoramidites available for bioconjugation but also paves the way for developing spatiotemporal-controlled, orthogonal-regulated DNA-based logic devices for a range of applications in materials science, polymers, chemistry, and biology.

Photolytic reactions allow the optical control of the liberation of biological effectors by photolabile protecting groups. The development of versatile technologies enabling the use of deep‐red or NIR light excitation still represents a challenging issue, in particular for light‐induced drug release (e.g., light‐induced prodrug activation). Here, light‐sensitive biocompatible lipid nanocapsules able to liberate an antitumoral drug through photolysis are presented. It is demonstrated that original photon upconverting nanoparticles (LNC‐UCs) chemically conjugated to a coumarin‐based photocleavable linker can quantitatively and efficiently release a drug by upconversion luminescence‐assisted photolysis using a deep‐red excitation wavelength. In addition, it is also able to demonstrate that such nanoparticles are stable in the dark, without any drug leakage in the absence of light. These findings open new avenues to specifically liberate diverse drugs using deep‐red or NIR excitations for future therapeutic applications in nanomedicine.