Triplet-triplet annihilation photon-upconversion in hydrophilic media with biorelevant cholesteryl triplet energy acceptors

Funding Information: The Academy of Finland (Grant No. 316893) Funding Information: YJY is thankful for the support from the Kilpatrick Graduate Fellowship and the Starr Fieldhouse Research Fellowship Programs at Illinois Tech. The authors thank the National Science Foundation for the generous support to this work under a CAREER grant N° 1753012 Awarded to AJA. JI, ND and TL also thank the Academy of Finland for the generous support to this work under grant N° 316893. Publisher Copyright: © 2021 Elsevier B.V.We report two new biorelevant cholesteryl-based triplet energy acceptors, derivatives of DPA or 9,10-diphenylanthracene (C–DPA and C2–DPA). Using two different triplet sensitizers: QDN (ET ≈ 1.67 eV in PEG200) and PdTPP (ET ≈ 1.78 eV in PEG200), we were able to achieve both endothermic (with QDN) and exothermic (with PdTPP) triplet sensitization of DPA, C–DPA and C2–DPA in hydrophilic PEG200 media. While the maximum rate of triplet energy transfer (TET) was achieved with PdTPP and DPA (kTET = 4.7 × 107 M−1 s−1), for the cholesteryl-based acceptors, we found that the kinetic of the TET process was dependent upon the concentration of the acceptor. For PdTPP/C–DPA pair, the rate of the dynamic triplet energy quenching was kTET = 1.9 × 107 M−1 s−1; however, at higher concentrations of the quencher, the system reached a stationary state due to formation of self-assembled sub-domains of C–DPA that likely slowed the TET process. It was also found that this aggregation of C–DPA in PEG200 led to a 3.5 folds increase in the Ith compared to 133 mW cm2 for DPA. Subsequently, we estimated the ΦUC for these donor/acceptor pairs: QDN/DPA, PdTPP/DPA, and PdTPP/C–DPA. With respect to the estimated threshold intensity (Ith), we found that the quantum yields of TTA-UC were 2 ≤ QYUC≤12%.Peer reviewe

Nanoparticle release from anionic nanocellulose hydrogel matrix

Nanocellulose hydrogels have been shown to be excellent platforms for sustained delivery of drug molecules. In this study, we examine the suitability of anionic nanocellulose hydrogels for the sustained release of various nanoparticles. Systems releasing nanoparticles could produce applications especially for therapeutic nanocarriers, whose life-times in vivo might be limited. Micelles, liposomes and DNA origami nanostructures were incorporated into the nanocellulose hydrogels, and their release rates were measured. Two different hydrogel qualities (with 1% and 2% mass of fiber content) were used for each nanoparticle formulation. We showed that the drug release rates depend on nanoparticle size, shape, and charge. Smaller particles with neutral charge were released faster from 1% hydrogels than from 2% hydrogels. Nanoparticles with cationic labeling were retained in both hydrogels, whereas for the neutral nanoparticles, we were able to determine the cut-off size for released particles for both hydrogels. Rod-shaped DNA origami were released rapidly even though their length was above the cut-off size of spherical particles, indicating that their smaller radial dimension facilitates their fast release. Based on our results, anionic nanocellulose hydrogels are versatile platforms for the sustained release of the chosen model nanoparticles (liposomes, micelles, and DNA origami). Alternatively, for the tightly bound nanoparticles, this could lead to nanoparticle reservoirs within hydrogels, which could act as immobilized drug release systems.Peer reviewe

Triplet-triplet annihilation photon-upconversion in hydrophilic media with biorelevant cholesteryl triplet energy acceptors

We report two new biorelevant cholesteryl-based triplet energy acceptors, derivatives of DPA or 9,10-diphenylanthracene (C–DPA and C2–DPA). Using two different triplet sensitizers: QDN (ET ≈ 1.67 eV in PEG200) and PdTPP (ET ≈ 1.78 eV in PEG200), we were able to achieve both endothermic (with QDN) and exothermic (with PdTPP) triplet sensitization of DPA, C–DPA and C2–DPA in hydrophilic PEG200 media. While the maximum rate of triplet energy transfer (TET) was achieved with PdTPP and DPA (kTET = 4.7 × 107 M−1 s−1), for the cholesteryl-based acceptors, we found that the kinetic of the TET process was dependent upon the concentration of the acceptor. For PdTPP/C–DPA pair, the rate of the dynamic triplet energy quenching was kTET = 1.9 × 107 M−1 s−1; however, at higher concentrations of the quencher, the system reached a stationary state due to formation of self-assembled sub-domains of C–DPA that likely slowed the TET process. It was also found that this aggregation of C–DPA in PEG200 led to a 3.5 folds increase in the Ith compared to 133 mW cm2 for DPA. Subsequently, we estimated the ΦUC for these donor/acceptor pairs: QDN/DPA, PdTPP/DPA, and PdTPP/C–DPA. With respect to the estimated threshold intensity (Ith), we found that the quantum yields of TTA-UC were 2 ≤ QYUC≤12%.acceptedVersionPeer reviewe

Expanding excitation wavelengths for azobenzene photoswitching into the near-infrared range via endothermic triplet energy transfer

Developing azobenzene photoswitches capable of selective and efficient photoisomerization by long-wavelength excitation is an enduring challenge. Herein, rapid isomerization from the Z- to E-state of two ortho-functionalized bistable azobenzenes with near-unity photoconversion efficiency was driven by triplet energy transfer upon red and near-infrared (up to 770 nm) excitation of porphyrin photosensitizers in catalytic micromolar concentrations. We show that the process of triplet-sensitized isomerization is efficient even when the sensitizer triplet energy is substantially lower (>200 meV) than that of the azobenzene used. This makes the approach applicable for a wide variety of sensitizer-azobenzene combinations and enables the expansion of excitation wavelengths into the near-infrared spectral range. Therefore, indirect excitation via endothermic triplet energy transfer provides efficient and precise means for photoswitching upon 770 nm near-infared light illumination with no chemical modification of the azobenzene chromophore, a desirable feature in photocontrollable biomaterials.Peer reviewe

Structure and Dynamics of Thermosensitive pDNA Polyplexes Studied by Time-Resolved Fluorescence Spectroscopy

Combining multiple stimuli-responsive functionalities into the polymer design is an attractive approach to improve nucleic acid delivery. However, more in-depth fundamental understanding how the multiple functionalities in the polymer structures are influencing polyplex formation and stability is essential for the rational development of such delivery systems. Therefore, in this study the structure and dynamics of thermosensitive polyplexes were investigated by tracking the behavior of labeled plasmid DNA (pDNA) and polymer with time-resolved fluorescence spectroscopy using fluorescence resonance energy transfer (FRET). The successful synthesis of a heterofunctional poly(ethylene glycol) (PEG) macroinitiator containing both an atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) initiator is reported. The use of this novel PEG macroinitiator allows for the controlled polymerization of cationic and thermosensitive linear triblock copolymers and labeling of the chain-end with a fluorescent dye by maleimide-thiol chemistry. The polymers consisted of a thermosensitive poly(N-isopropylacrylamide) (PNIPAM, N), hydrophilic PEG (P), and cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, D) block, further referred to as NPD. Polymer block D chain-ends were labeled with Cy3, while pDNA was labeled with FITC. The thermosensitive NPD polymers were used to prepare pDNA polyplexes, and the effect of the N/P charge ratio, temperature, and composition of the triblock copolymer on the polyplex properties were investigated, taking nonthermosensitive PD polymers as the control. FRET was observed both at 4 and 37 degrees C, indicating that the introduction of the thermosensitive PNIPAM block did not compromise the polyplex structure even above the polymer's cloud point. Furthermore, FRET results showed that the NPD- and PD-based polyplexes have a less dense core compared to polyplexes based on cationic homopolymers (such as PEI) as reported before. The polyplexes showed to have a dynamic character meaning that the polymer chains can exchange between the polyplex core and shell. Mobility of the polymers allow their uniform redistribution within the polyplex and this feature has been reported to be favorable in the context of pDNA release and subsequent improved transfection efficiency, compared to nondynamic formulations.Peer reviewe

Zinc phthalocyanine activated by conventional indoor light makes a highly efficient antimicrobial material from regular cellulose

Zn phthalocyanine with improved synthesis suitable for bulk production shows extremely high antimicrobial efficacies even under weak indoor light. The dye-impregnated cellulose material inactivates over 99.996% of drug-resistant C. albicans, S. aureus and E. faecalis in just one hour exposure with consumer-grade fluorescent lamps and diodes.publishedVersionPeer reviewe

Efficient photon upconversion at remarkably low annihilator concentrations in a liquid polymer matrix: when less is more

A green-to-blue triplet-triplet annihilation upconversion of 24.5% quantum yield was achieved at a remarkably low 600 μM annihilator concentration in a viscous polymer matrix. This was made possible by utilizing a ZnTPP-based photosensitizer with exceptionally long 11 ms phosphorescence lifetime. Higher 3 mM annihilator concentration resulted in lower 24% upconversion quantum yield.acceptedVersionPeer reviewe

Electron-Deficient Phenanthrenequinone Derivative for Photoactivated Hydrogen Atom Transfer Mediated Oxidation of Secondary Alcohols

In 2000, Fukuzumi and co-workers reported a seminal study on the photochemical oxidation of benzylic alcohols with visible-light-excited 9,10-phenanthrenequinone (PQ) under argon atmosphere (J. Am. Chem. Soc.2000, 122, 8435). We optimized the reaction conditions they reported and were able to oxidize 1-(4-methoxyphenyl)ethanol quantitatively to 4 ́-methoxyacetophenone in only 15 min with 10 mol% PQ as a photocatalyst under oxygen. However, we observed a significant decrease in the oxidation rate with more electron-deficient benzylic alcohols as starting materials. To improve the photooxidation performance, we designed a high-yielding synthetic route for a novel, more electron-deficient PQ derivative, 3,6-bis(trifluoromethyl)-9,10-phenanthrenequinone (PQ-CF3). Its efficiency as a photocatalyst in the fast oxidation of secondary alcohols was demonstrated not only with several electronically diverse benzylic alcohols but also with aliphatic substrates. The comprehensive mechanistic studies based on Hammett plot construction, kinetic isotope experiments, and DFT computations suggest that the mechanistic pathway of the alcohol oxidation is dependent on the electronic properties of both the catalyst and the substrate. As the key mechanistic discovery, we showed that the newly developed PQ-CF3 operates as a highly efficient hydrogen atom transfer (HAT)catalystPeer reviewe

Nanoparticle release from anionic nanocellulose hydrogel matrix

Nanocellulose hydrogels have been shown to be excellent platforms for sustained delivery of drug molecules. In this study, we examine the suitability of anionic nanocellulose hydrogels for the sustained release of various nanoparticles. Systems releasing nanoparticles could produce applications especially for therapeutic nanocarriers, whose life-times in vivo might be limited. Micelles, liposomes and DNA origami nanostructures were incorporated into the nanocellulose hydrogels, and their release rates were measured. Two different hydrogel qualities (with 1% and 2% mass of fiber content) were used for each nanoparticle formulation. We showed that the drug release rates depend on nanoparticle size, shape, and charge. Smaller particles with neutral charge were released faster from 1% hydrogels than from 2% hydrogels. Nanoparticles with cationic labeling were retained in both hydrogels, whereas for the neutral nanoparticles, we were able to determine the cut-off size for released particles for both hydrogels. Rod-shaped DNA origami were released rapidly even though their length was above the cut-off size of spherical particles, indicating that their smaller radial dimension facilitates their fast release. Based on our results, anionic nanocellulose hydrogels are versatile platforms for the sustained release of the chosen model nanoparticles (liposomes, micelles, and DNA origami). Alternatively, for the tightly bound nanoparticles, this could lead to nanoparticle reservoirs within hydrogels, which could act as immobilized drug release systems.Peer reviewe

Triplet-Sensitized Bidirectional Isomerization of Bridged Azobenzene

Diazocine is a bridged azobenzene with both phenyl rings connected by a CH2-CH2 group. Despite this rather small structural difference, diazocine exhibits improved properties over azobenzene as a photoswitch, such as high switching efficiencies, very high quantum yields, switching wavelengths in the visible range, and most importantly, the fact that it is more stable in the Z configuration, which is particularly expedient in photopharmacology and mechanophore applications. According to our studies presented here, another advantage over conventional azobenzene is now added. In contrast to azobenzenes and other photochromes, diazocine can be switched with two different triplet sensitizers present at the same time in both directions: Z→E as well as E→Z. Experimental and theoretical (CASPT2) studies of triplet excitation energies provide an explanation for this fact. The triplet energies in Z and E azobenzene are almost equal, which prevents selective sensitization of either isomer. In diazocine, the two excitation energies are well-separated, so they can be accessed selectively. Besides offering fundamental physical insight to diazocines, an emerging class of photoswitches, our work opens up a number of potential avenues for utilizing them for example in photopharmacology and smart materials design due to the significant redshift of excitation wavelengths to from blue to green (Z→E) and green to far-red (E→Z), which triplet sensitization offers