Controlled Release of Fragrant Molecules with Visible Light

Photoinduced movement: how photoirradiation induced the movements of matter

Pioneered by the success on active transport of ions across membranes in 1980 using the regulation of the binding properties of crown ethers with covalently linked photoisomerizable units, extensive studies on the movements by using varied interactions between moving objects and environments have been reported. Photoinduced movements of various objects ranging from molecules, polymers to microscopic particles were discussed from the aspects of the driving for the movements, materials design to achieve the movements and systems design to see and to utilize the movements are summarized in this review.

Stimulus responsive microcapsules and their aromatic applications

Fragrances and essential oils are promising for a wide range of applications due to their pleasant odors and diverse effects. However, direct addition to consumer products has the disadvantages of short retention time and easy deterioration of odor. At the same time, releasing a large amount of odor in a short time may be an unpleasant experience, which severely limits the practical application of aromatic substances. Microencapsulation perfectly solves these problems. Stimuli-responsive microcapsules, which combine environmental stimulation with microencapsulation, can not only effectively prevent the rapid decomposition and evaporation of aroma components, but also realize the "on-off" intelligent release of aroma substances to environmental changes, which have great promise in the field of fragrances. In this review, the application of stimuli-responsive microcapsules in fragrances is highlighted. Firstly, various encapsulation materials used to prepare stimuli-responsive aromatic microcapsules are described, mainly including some natural polymers, synthetic polymers, and inorganic materials. Subsequently, there is a detailed description of the common release mechanisms of stimuli-responsive aromatic microcapsules are described in detail. Finally, the application and future research directions are given for stimuli-responsive aromatic microcapsules in new textiles, food, paper, and leather.

Facile anchoring mussel adhesive mimic tentacles on biodegradable polymer cargo carriers via self-assembly for microplastic-free cosmetics

Enhancing the deposition of fragrance delivery systems contained in personal care products on target surfaces is crucial for increasing the longevity of scent, efficiently utilizing expensive functional compounds and limiting the generation of microplastics in domestic waste water. In this work, we designed and synthesized a new type of biomimetic macromolecules, chitosan-graft-L-lysine-L-DOPA (C-L-D), as a versatile biodegradable adhesion promoter to facilitate the deposition of biodegradable fragrance carriers on diverse surfaces including hair, cotton and skin. The C-L-D has hyperbranched chain architecture with many oligopeptide adhesive tentacles, each being a simple mimic of mussel adhesive proteins. It also exhibits unique amphiphilic characteristic. As a result, it could be facilely anchored on cargo-loaded poly(lactic-co-glycolic acid) nanoparticle surface via self-assembly in the particle preparation process. The C-L-D-modified nanoparticles show significantly higher deposition efficiencies than polyvinyl alcohol- and chitosan-coated particles when deposited on the target surfaces in different aqueous media as the lysine and DOPA units are capable of providing multi-noncovalent interactions, including electrostatic, polar, hydrophobic interactions, and bidentate hydrogen bonds, with the target surfaces, and possibly also inducing oxidative cross-linking. A much higher retention rate of the C-L-D-modified nanoparticles on cotton surface is also observed after washing with a soap solution, which could be attributed to the significant role played by bidentate hydrogen bonds. These findings suggest that C-L-D is a versatile biodegradable adhesion promoter and has the potential to be applied for various personal care applications and beyond.

Reversible photo control of proton chemistry

Spatial, temporal, and remote control of proton chemistry can be achieved by using photoacids, which are molecules that transform from weak to strong acids under light. Most of proton chemistry is driven by a high concentration of protons ([H⁺]), which is difficult to obtain using excited-state photoacids. Metastable-stable state photoacids (mPAHs) can reversibly generate a high [H⁺] under visible light with a moderate intensity. It has been widely applied in different fields, e.g. fueling dissipative assemblies, driving molecular machines, controlling organic reactions, powering nanoreactors, curing diseases, manipulating DNA and proteins, developing smart materials, capturing carbon dioxide in air etc. This article compares mPAH with excited-state photoacid as well as common acids e.g. HCl to explain its advantages. Recent studies on the thermal dynamics, kinetics, and photoreaction of mPAHs are reported. The advantages and disadvantages of the three types of mPAHs, i.e. merocyanine, indazole, and TCF mPAHs, are compared with regard to photo-induced [H⁺], switching rate, and other properties. The mechanisms of controlling or driving functional systems, which involve acid-base reactions, acid catalyzed reactions, ionic bonding, coordination bonding, hydrogen bonding, ion exchange, cation-π interaction, solubility, swellability, permeability, and pH change in biosystems, are described. Applications of mPAHs in the chemical, material, energy, biotechnology and biomedical fields published in the past 5 years are reviewed. Prospects in the development and application of mPAHs are discussed.

Mechanically Interlocked Profragrances for the Controlled Release of Scents

The synthesis of a series of interlocked profragrances and the study of the controlled release of the corresponding scents are reported. The structures of the profragrances are based on a [2]pseudorotaxane scaffold with a fumaramate thread derived from perfumery alcohols and a tetrabenzylamido ring. The delivery of the scents was accomplished by sequential thermal dethreading and further enzymatic hydrolysis. Alternatively, the dethreading can be achieved by increasing the polarity of the solvent or photochemical isomerization. The temperature of dethreading can be modulated by the steric demand of the ends of the thread, which allows the selection of different precursor structures depending on the desired rates of delivery. The inputs and outputs for the controlled release of the interlocked profragrances correspond to those of YES or AND logic gates.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Thermodynamics and kinetics of protonated merocyanine photoacids in water

Metastable-state photoacids (mPAHs) are chemical species whose photo-activated state is long-lived enough to allow for proton diffusion. Liao's photoacid (1) represents the archetype of mPAHs, and is being widely used on account of its unique capability to change the acidity of aqueous solutions reversibly. The behavior of 1 in water, however, still remains poorly understood. Herein, we provide in-depth insights on the thermodynamics and kinetics of 1 in water through a series of comparative 1H NMR and UV-Vis studies and relative modelling. Under dark conditions, we quantified a three-component equilibrium system where the dissociation (K a) of the open protonated form (MCH) is followed by isomerization (K c) of the open deprotonated form (MC) to the closed spiropyran form (SP) - i.e., in the absence of light, the ground state acidity can be expressed as K GS a = K a(1 + K c). On the other hand, under powerful and continuous light irradiation we were able to assess, for the first time experimentally, the dissociation constant (K MS a) of the protonated metastable state (cis-MCH). In addition, we found that thermal ring-opening of SP is always rate-determining regardless of pH, whereas hydrolysis is reminiscent of what is found for Schiff bases. The proposed methodology is general, and it was applied to two other compounds bearing a shorter (ethyl, 2) and a longer (butyl, 3) alkyl-1-sulfonate bridge. We found that the pK a remains constant, whereas both pK c and pK MS a linearly increase with the length of the alkyl bridge. Importantly, all results are consistent with a four-component model cycle, which describes perfectly the full dynamics of proton release/uptake of 1-3 in water. The superior hydrolytic stability and water solubility of compound 3, together with its relatively high pK GS a (low K c), allowed us to achieve fully reversible jumps of 2.5 pH units over 18 consecutive cycles (6 hours).

Thermal Triggered Release of Menthol from Different Carriers: A Comparative Study

The design of appropriate thermally responsive fragrance carrier systems is of significant importance for the application of fragrance in the food and tobacco industries. In this study, we investigate the potential of sorbitan monostearate and guar gum for the stabilization of menthol under ambient conditions and the thermally-induced release of menthol. Our results show that the sorbitan monostearate carrier could well stabilize the menthol for at least up to 15 days with neglectable menthol loss due to the favorable binding of menthol on the sorbitan monostearate carrier. In addition, rapid and controlled release of menthol could take place at a temperature of 80 °C in the sorbitan monostearate carrier system. As a comparison, guar gum could not stabilize menthol as a result of its poor compatibility. Our results suggest that sorbitan monostearate can be an ideal carrier material for the support of fragrance. In addition, our results also provide a useful guide for the tailored design of thermally responsive fragrance carriers.

Polymeric Photoacids Based on Naphthols-Design Criteria, Photostability, and Light-Mediated Release

The implementation of photoswitches within polymers offers an exciting toolbox in the design of light-responsive materials as irradiation can be controlled both spatially and temporally. Herein, we introduce a range of water-soluble copolymers featuring naphthol-based chromophores as photoacids in the side chain. With that, the resulting materials experience a drastic increase in acidity upon stimulation with UV light and we systematically studied how structure and distance of the photoacid from the copolymer backbone determines polymerizability, photo-response, and photostability. Briefly, we used RAFT (reversible addition-fragmentation chain transfer) polymerization to prepare copolymers consisting of nona(ethylene glycol) methyl ether methacrylate (MEO9 MA) as water-soluble comonomer in combination with six different 1-naphthol-based ("N") monomers. Thereby, we distinguish between methacrylates (NMA, NOeMA), methacrylamides (NMAm, NOeMAm), vinyl naphthol (VN), and post-polymerization modification based on [(1-hydroxynaphthalen-2-amido)ethyl]amine (NOeMAm, NAmeMAm). These P(MEO9 MAx -co-"N"y ) copolymers typically feature a 4:1 MEO9 MA to "N" ratio and molar masses in the range of 10 kg mol-1 . After synthesis and characterization by using NMR spectroscopy and size exclusion chromatography (SEC), we investigated how potential photo-cleavage or photo-degradation during irradiation depends on the type and distance of the linker to the copolymeric backbone and whether reversible excited state proton transfer (ESPT) occurs under these conditions. In our opinion, such materials will be strong assets as light-mediated proton sources in nanostructured environments, for example, for the site-specific creation of proton gradients. We therefore exemplarily incorporated NMA into an amphiphilic block copolymer and could demonstrate the light-mediated release of Nile red from micelles formed in water as selective solvent.

Magnetic and light-responsive nanogels based on chitosan functionalized with Au nanoparticles and poly(N-isopropylacrylamide) as a remotely triggered drug carrier

Synthesis of thermosensitive nanogels based on functionalized chitosan with Au nanoparticles (NPs) and poly(NIPAM) to release of drug molecules under light exposure.

Ti3 C2 MXene Paper for the Effective Adsorption and Controllable Release of Aroma Molecules

Olfactory sensing and perception play an important role in people's daily lives and greatly affects senses, emotions, and behavior. In particular, the development of the controlled release of aroma enhances human's well-being and strengthens interactions with surroundings through olfactory display, especial when combined with visual and audial cues. Here, Ti₃ C₂ MXene plays a dual-function role as the adsorption site of aroma molecules and the heating source for the controlled release of aroma molecules. Due to abundant termination groups on the surface and the metallic nature, Ti₃ C₂ MXene provides abundant active sites for the interaction with aroma molecules; simultaneously, MXene can be electrically heated to thermally desorb the aroma molecules from the interaction sites. This approach eliminates the interface incompatibility issues between the heating source and the molecular encapsulation layer in conventional olfactory display system. This work presents the controlled release of the aroma molecule phenethyl alcohol (PA) using Ti₃ C₂ MXene paper. Ti₃ C₂ MXene paper serves as the adsorption material and a heating source that achieves 100 °C within 1 s. The relative amount of PA released reaches nearly 100% after 1 min of heating.

Controlled drug delivery systems for cancer based on mesoporous silica nanoparticles

The implementation of nanotechnology in medicine has opened new research horizons particularly in the field of therapeutic delivery. Mesoporous silica particles have emerged as biocompatible drug delivery systems with an enormous potential in the treatment of cancer among many other pathologies. In this review, we focus on the unique properties of these particles as chemotherapy delivery carriers. Here, we summarize the general characteristics of these nanomaterials - including their physicochemical properties and customizable surfaces - different stimuli that can be used to trigger targeted drug release, biocompatibility and finally, the drawbacks of these types of nanomaterials, highlighting some of the most important features of mesoporous silica nanoparticles in drug delivery.

Effects of Substituents on Metastable-State Photoacids: Design, Synthesis, and Evaluation of their Photochemical Properties

Recently, metastable-state photoacids have been widely used to control proton transfer in numerous chemical and biological processes as well as applications with visible light. Generally, substituents have a great influence on the photochemical properties of molecules, which will further affect their applications. Yet, the effects of substituents on metastable-state photoacids have not been studied systematically. In this work, 16 metastable-state photoacid derivatives were designed and synthesized on the basis of substituents having a large range of σ-π electron-donor-acceptor capabilities. The effects of substituents on the color display [or maximum absorption band(s)], solubility, pK_a values, dark/photoacidity, photosensitivity, and relaxation kinetic(s) were investigated in detail. This study will be helpful for the targeted design and synthesis of promising photoacids and the application of their photocontrolled proton-release processes in functional materials/devices.

Localized pH Pulses in PBS Buffer Repeatedly Induced by Visible Light

The pH of biological systems is important for the activity of enzymes, and abnormal cellular pH is related to many diseases. Spatial and temporal modulation of pH with light will be useful for studying the pH effects on enzymatic functions and disease mechanisms and may lead to new drug delivery and therapeutic methods. However, the pH of biological systems is maintained by pH buffers, which implies that only temporary pH change (pH pulse) can be induced in an open system. A key fundamental problem is whether a photoinduced pH pulse can be strong and long enough to generate a significant effect. In this work, a photoinduced pH pulse in a micrometer hydrophilic film in PBS buffer has been demonstrated. The thin film was made of an metastable-state photoacid (mPAH) polymer. It is an open system that allows exchange of protons. A quick release of the protons from the mPAHs and the proton exchange between the film and PBS resulted in a pH pulse generated by moderate visible-light irradiation. The magnitude of the pulse is 1.4-1.9 units with maximum pH change occurring after ∼18 s of the irradiation. Since the mPAH is a reversible photoacid, the pH pulse could be repeatedly generated after the photoacid recovered in the dark. This work shows that photochemical modulation of pH is possible even in buffered solutions.

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

Spiropyrans have played a pivotal role in the emergence of the field of chromism following their discovery in the early 20th century, with almost ubiquitous use in materials applications especially since their photochromism was discovered in 1952.

A Reversible Proton Generator with On/Off Thermoswitch

A reversible polymer photoacid with a thermal on/off switch at physiological temperature able to trigger a large pH modulation of its environment is prepared. Light is used to control the acidity of the solution. Additionally, the temperature could be used to modulate the photoacid efficiency, practically turning on and off the ability of the polymer to produce protons. The behavior of this thermoresponsive photoacid copolymer is the result of the combined action of the temperature-responsive N-isopropylacrylamide and of a reversible photoacid monomer based on a spiropyran derivative. The acidification of the aqueous medium is activated by irradiation at λ = 460 nm. The reverse reaction is achieved by removing the light stimuli or by exposing the solution to UV-light. Increasing the temperature above the lower critical solution temperature of the copolymer deactivates the photoacid and irradiation at λ = 460 nm does not lead to the generation of protons or to any detectable change in the pH value of the solution. Hence, the addition of N-isopropylacrylamide as a comonomer acts as a thermal on/off switch for the photoacid and the coupling of temperature-and light-responsiveness in the polyphotoacids yields a "thermophotoacid".

Visible light-triggered fluorescence and pH modulation using metastable-state photoacids and BODIPY

Small changes in the pH gradient play a critical role in numerous biological and chemical pathways. Systems capable of monitoring and regulating these changes with high sensitivity and minimum photo-fatigue are in demand. Herein, we propose a visible light-triggered molecular system that allows for reversible regulation of acidity and fluorescence. This robust bi-functional system opens a new horizon towards novel studies that rely on small changes in acid-mediated controlled processes with high sensitivity. The two photosensitive compounds employed, a metastable-state photoacid (mPAH) and a boron-dipyrromethene (BODIPY) derivative, allow for consistent modulation of both fluorescence (based on the working principle of the inner filter effect) and pH (around a magnitude) over multiple cycles.

Cargo delivery on demand from photodegradable MOF nano-cages

We report the photo-induced degradation of and cargo release from a nanoscale metal-organic framework (nMOF) incorporating photo-isomerizable 4,4'-azobenzenedicarboxylate (AZB) linkers. The structure matches a UiO-type framework where 12 4,4'-azobenzenedicarboxylate moieties are connected to a Zr₆O₄(OH)₄ cluster, referred to as UiO-AZB. Due to the incorporation of photo-isomerizable struts, the degradation of UiO-AZB is accelerated by irradiation with white light (1.3 ± 0.1% h^-1 under dark conditions vs. 8.4 ± 0.4% h^-1 when irradiated). Additionally, we show slow release of Nile Red (NR) which is triggered by irradiation (0.04 ± 0.01% h^-1 under dark conditions vs. 0.36 ± 0.02% h^-1 when irradiated).

Efficient control of movement in non-photoresponsive molecular machines by a photo-induced proton-transfer strategy

The first successful application of a PIPT strategy executed by the photoacid 1-MEH in controlling the switch of MIM systems has been demonstrated.

Design and Applications of Metastable-State Photoacids

Proton transfer is one of the most common processes in nature, and many chemical, material, and biological processes are sensitive to proton concentration, from acid-catalyzed reactions to the activities of many enzymes. Photoacids that reversibly undergo proton dissociation upon irradiation promise remote spatial and temporal control over proton-sensitive processes and could provide a way to convert photoenergy into other types of energy. The recently discovered metastable-state photoacids can produce a large proton concentration with high efficiency and good reversibility. A reversible pH change of over 2 units has been demonstrated using an aqueous solution of a metastable-state photoacid. Additionally, moderate-intensity visible light, for example, from LEDs and sunlight, can be used to activate this type of photoacid. This photocontrolled proton release occurs in aqueous and nonaqueous solutions and in polymeric materials. Therefore, this type of photoacid can be conveniently incorporated into different systems to control various proton transfer processes. Metastable-state photoacids are generally designed by linking an electron-accepting moiety and a weakly acidic nucleophilic moiety with a double bond. Photoinduced trans-cis isomerization of the double bond allows a nucleophilic cyclization reaction to occur between the two moieties. The tandem reaction generates a highly acidic metastable form, which releases a proton. In the dark, the metastable form relaxes to the original form and takes back the proton. Several electron-accepting and nucleophilic moieties have been used to construct different types of metastable-state photoacids for different applications. The advantages and disadvantages of these photoacids in terms of their photoacidity, dark acidity, reversibility, stability, etc. will be discussed in this Account. Metastable-state photoacids have been used to catalyze bond formation and bond-breaking reactions in which the reactions can be activated and stopped by turning on and off irradiation, respectively. They have been used to reversibly protonate molecules to affect the ionic and hydrogen bonding between molecules or between different moieties of a molecule. Protonation can also alter the electronic configuration of molecules to change their electronic and optical properties. Since a proton has a positive charge, photoacids have been used to control ion exchange processes. Applying metastable-state photoacids to control Fisher esterification, volume-changing hydrogels, the killing of bacteria, odorant release, the color of materials, the formation of nanoparticles, and polymer conductivity has been reported by our group. Metastable-state photoacids have also been utilized to control supramolecular assemblies, molecular switches, microbial fuel cells, cationic sensors, nanoparticle aggregation, and ring-opening polymerizations. The future prospects of this research area will be discussed at the end of this Account.

Proton-coupled charge-transfer reactions and photoacidity of N,N-dimethyl-3-arylpropan-1-ammonium chloride salts

Excited-state, intermolecular proton-transfers of aromatics tethered to ammonium groups are solvent mediated and coupled to either the formation of an exciplex or a solvent-separated ion pair.

Reversible dissolution/formation of polymer nanoparticles controlled by visible light

Noncovalent crosslinking between polyvinyl pyridine and a copolymer of acrylic acid led to the formation of a polymer nanoparticle. In the presence of a metastable-state photoacid, reversible dissolution and formation of the nanoparticle can be controlled by visible light. Photo-induced proton transfer from the photoacid to the polymers broke the hydrogen bonding and ionic bonding and led to the dissolution of the nanoparticle. Cycles of dissolution and formation were controlled by turning on and off irradiation, and were demonstrated by the transmittance change.

Near-Infrared-Sensitive Materials Based on Upconverting Nanoparticles

The near-infrared (NIR) region of the spectrum is called the "therapeutic window" because NIR light can penetrate deeply into tissue. Therefore, NIR-sensitive materials are attractive for biomedical applications. Recently, upconverting nanoparticles (UCNPs) were used to construct NIR-sensitive materials. UCNPs convert NIR light to UV or visible light, which can trigger photoreactions of photosensitive materials. Here, how to use UCNPs to construct NIR-sensitive materials is introduced, applications of NIR-sensitive materials with a focus on biomedical applications are highlighted, and the associated challenges are discussed.

Red-Light-Responsive Supramolecular Valves for Photocontrolled Drug Release from Mesoporous Nanoparticles

Red-light-responsive supramolecular valves constructed by tetra-ortho-methoxy-substituted azobenzene (mAzo) and β-cyclodextrin (β-CD) were used to control drug release from mesoporous silica nanoparticles (MSNs). Doxorubicin (DOX) was used as a model drug and loaded into nanopores of mAzo modified MSNs. β-CD formed supramolecular valves with mAzo by host-guest interaction and closed the nanopores. Red light was able to open the supramolecular valves and induce DOX release even in deep tissue.

Photolabile acetals as profragrances: the effect of structural modifications on the light-induced release of volatile aldehydes on cotton

Dynamic headspace analysis above a cotton surface treated with a fabric softening formulation showed that, depending on the substitution pattern, the photoirradiation of 4,4-diphenyl-4H-benzo[d][1,3]dioxine profragrances released perfumery aldehydes in quantities spanning several orders of magnitude.

Photocontrolled proton transfer in solution and polymers using a novel photoacid with strong C–H acidity

A easily-prepared photoacid with low O–H dark acidity and high C–H photoacidity reversibly protonated different acidochromic dyes in polymer films.

Manipulating pH using near-infrared light assisted by upconverting nanoparticles

Control of pH was achieved using near-infrared light assisted by upconverting nanoparticles and a ruthenium complex photobase.

Supramolecular hydrogels constructed by red-light-responsive host-guest interactions for photo-controlled protein release in deep tissue

We report a novel red-light-responsive supramolecule. The tetra-ortho-methoxy-substituted azobenzene (mAzo) and β-cyclodextrin (β-CD) spontaneously formed a supramolecular complex. The substituted methoxy groups shifted the responsive wavelength of the azo group to the red light region, which is in the therapeutic window and desirable for biomedical applications. Red light induced the isomerization of mAzo and the disassembly of the mAzo/β-CD supramolecular complex. We synthesized a mAzo-functionalized polymer and a β-CD-functionalized polymer. Mixing the two polymers in an aqueous solution generated a supramolecular hydrogel. Red light irradiation induced a gel-to-sol transition as a result of the disassembly of the mAzo/β-CD complexes. Proteins were loaded in the hydrogel. Red light could control protein release from the hydrogel in tissue due to its deep penetration depth in tissue. We envision the use of red-light-responsive supramolecules for deep-tissue biomedical applications.

Photon upconversion lithography: patterning of biomaterials using near-infrared light

Photon upconversion lithography is demonstrated for the patterning of proteins using near-infrared light. Proteins and an upconverting-nanoparticle-decorated substrate are linked via blue-light-cleavable Ru complexes. The substrate is irradiated using near-infrared light with a photomask. In the exposed areas, upconverting nanoparticles convert the near-infrared light into blue light, which induces cleavage of the Ru complexes and release of the proteins.

Photoactive fluoropolymer surfaces that release sensitizer drug molecules

We describe a physical-organic study of two fluoropolymers bearing a photoreleasable PEGylated photosensitizer that generates (1)O2((1)Δg) [chlorin e6 methoxy tri(ethylene glycol) triester]. The surfaces are Teflon/poly(vinyl alcohol) (PVA) nanocomposite and fluorinated silica. The relative efficiency of these surfaces to photorelease the PEGylated sensitizer [shown previously to be phototoxic to ovarian cancer cells (Kimani, S. et al. J. Org. Chem 2012, 77, 10638)] was slightly higher for the nanocomposite. In the presence of red light and O2, (1)O2 is formed, which cleaves an ethene linkage to liberate the sensitizer in 68-92% yield. The fluoropolymers were designed to deal with multiple problems. Namely, their success relied not only on high O2 solubility and drug repellency but also on the C-F bonds, which physically quench little (1)O2, for singlet oxygen's productive use away from the surface. The results obtained here indicate that Teflon-like surfaces have potential uses in delivering sensitizer and singlet oxygen for applications in tissue repair and photodynamic therapy (PDT).

“Old” chemistry in a new context: photocleavable 2-oxoacetate-containing latex dispersions and core–shell microcapsules for the controlled release of volatile compounds

2-Oxoacetates polymerised into nanoparticles or encapsulated in microcapsules are stable against hydrolysis and release fragrances on UVA irradiation.