The use of upconverting nanoparticles to drive organic photoreactions

One of the primary disadvantages of organic photochemistry is the need for high-energy UV light, light that has many detrimental qualities. A viable solution to this problem is the use of upconverting nanoparticles (UCNP) that can locally convert near infrared (NIR) laser light into UV light or visible light of sufficient energy to drive organic photoreactions. In an initial study (Chapter 3), the use of UCNPs to drive both UV and visible light dependent photoreactions with NIR light was demonstrated using 1,2-dithienylethene (DTE) molecular switches functioning as probes. In this study the concept of NIR-to-visible ‘remote-control’ photorelease was also introduced. In a second study (Chapter 4), two multicolour UCNPs were developed. It was demonstrated that by only altering the power-density of the one wavelength NIR excitation source, the photochemistry of two DTE molecular switches could be selectively and bi-directionally driven along its two reaction pathways. In a third study (Chapter 5), fluorescence modulation bioimaging was demonstrated in vivo in C. elegans nematodes. The fluorescence modulation in aqueous medium was achieved by decorating the surface of an UCNP with polyethylene glycol functionalized DTE molecular switches by ‘click’ chemistry. In a fourth study (Chapter 6), multimodal fluorescence modulation of a multicolour UCNP by two DTE molecular switches decorated on the surface of the UCNP was demonstrated. Apart from a greater degree of control in this more advanced system, it is also capable of NIR-to-UV ‘remote-control’ photoswitching. In a fifth study (Chapter 8), the surface of an UCNP was decorated with 3’,5’-dialkoxybenzoin photocages and the concept of NIR-to-UV ‘remote-control’ photorelease for potential use in drug-delivery was demonstrated. In a sixth study (Chapter 9), a fully water dispersible drug-delivery system was synthesized. Unfortunately the system proved impractical due to the choice of both photorelease system and therapeutic payload. In a seventh study (Chapter 10), a donor-acceptor 4-dimethylamino-3’,5’-dimethoxybenzoin photocage with both red-shifted absorbance and a significantly enhanced molar absorbance coefficient was synthesized and its initial and unique photochemistry was studied

Formation of an heterochiral supramolecular cage by diastereomer self-discrimination: fluorescence enhancement and C(60) sensing.

Diastereomer discrimination was observed in the formation of a metallomacrocycle from a racemic ligand based on Tröger's base. The metallomacrocycle exhibited a dramatic increase in fluorescence intensity compared to the ligand and its fluorescence was efficiently quenched by C(60)

Efficient red light photo-uncaging of active molecules in water upon assembly into nanoparticles

International audienceWe introduce a means of efficiently photo-uncaging active compounds from amino-1,4-benzoquinone in aqueous environments. Aqueous photochemistry of this photocage with one-photon red light is typically not efficient unless the photocaged molecules are allowed to assemble into nanoparticles. A variety of biologically active molecules were functionalized with the photocage and subsequently formulated into water-dispersible nanoparticles. Red light irradiation through various mammalian tissues achieved efficient photo-uncaging. Co-encapsulation of NIR fluorescent dyes and subsequent photomodulation provides a NIR fluorescent tool to assess both particle location and successful photorelease

Near-Infrared-Induced Heating of Confined Water in Polymeric Particles for Efficient Payload Release

Near-infrared (NIR) light-triggered release from polymeric capsules could make a major impact on biological research by enabling remote and spatio­temporal control over the release of encapsulated cargo. The few existing mechanisms for NIR-triggered release have not been widely applied because they require custom synthesis of designer polymers, high-powered lasers to drive inefficient two-photon processes, and/or coencapsulation of bulky inorganic particles. In search of a simpler mechanism, we found that exposure to laser light resonant with the vibrational absorption of water (980 nm) in the NIR region can induce release of payloads encapsulated in particles made from inherently non-photo-responsive polymers. We hypothesize that confined water pockets present in hydrated polymer particles absorb electromagnetic energy and transfer it to the polymer matrix, inducing a thermal phase change. In this study, we show that this simple and highly universal strategy enables instantaneous and controlled release of payloads in aqueous environments as well as in living cells using both pulsed and continuous wavelength lasers without significant heating of the surrounding aqueous solution