J. Phys. Chem. C 2020 (ASAP)

The strong interaction between plasmonic metal nanoparticles and photosensitizers can significantly amplify their singlet oxygen (1O2) production. However, improving the performance of these hybrid plasmonic nanostructures is hampered by the lack of understanding of how their plasmonic properties impact the enhancement of 1O2 production. Here, we report that a Au core-based nanoparticle can outperform a Ag one. This result is striking as Ag is referred to as a better plasmonic metal than Au and forms the basis of our investigation. We use a novel approach based on a mini meta-analysis to elucidate and quantify the near- and far-field contributions to the plasmon-enhanced 1O2 production by using a highly tunable model hybrid photosensitizer–metal core@shellnanoparticle. The correlation between time-resolved 1O2 measurements and the experimental and simulated plasmonic optical properties was achieved by comparing the results of four new nanoparticles of differ...

Phys. Chem. Chem. Phys. 2019, 21, 25054-25064.

Liposomes carrying membrane-embedded porphyrin-phospholipid (PoP) are capable of chemo- and photo-therapeutic modes of action, which make them a potential candidate material for next-generation cancer treatments. This study examines singlet oxygen (1O2) production and release by PoP liposomes carrying either no chemotherapeutic cargo (EMPTY), or those carrying either doxorubicin (DOX) or irinotecan (IRT) chemotherapy drugs. Herein, we developed a strategy to quantify the fraction of 1O2 lifetime spent in the three distinct local liposomal environments by obtaining four key pieces of information for each system: average 1O2 deactivation rate constants (kΔ) for liposome suspensions in H2O and in D2O solvents, as well as the absolute and the apparent 1O2 production quantum yields (ΦΔ). Despite the characteristic differences in their photophysical behavior, namely in ΦΔ values, all three formulations of PoP liposomes were found to carry out 1O2...

Angew. Chem. Int. Ed. 2019, 58, 16815–16819. 

In aqueous electrochemical processes, the pH evolves spatially and temporally, and often dictates the process performance. Herein, a new method for the in‐operando monitoring of pH distribution in an electrochemical cell is demonstrated. A combination of pH‐sensitive fluorescent dyes, encompassing a wide pH range from ≈1.5 to 8.5, and rapid electrochemically coupled laser scanning confocal microscopy is used to observe pH changes in the cell. Using electrocoagulation as an example process, we show that the method provides new insights into the reaction mechanisms. The pH close to the aluminium electrode surface is influenced by the applied current density, hydrolysis of aluminium cations, and gas evolution. Through quantification of the pH at the anode, along with gas analysis, we find that hydrogen is evolved at the anode due to a non‐Faradaic chemical reaction. This leads to increased production of coagulant, which may open new routes to e...

J. Phys. Chem. Lett. 2019, 10, 3654-3660.

In plasmon-enhanced singlet oxygen (1O2) production, irradiation of a hybrid photosensitizer–metal nanoparticle leads to a significant alteration of the photosensitizer’s 1O2 yield. The quest for a more rational design of these nanomaterials calls for a better understanding of the enhancement mechanism that, to this day, remains largely unexplored. Herein, we introduce a new methodology to distinguish the near- and far-field contributions to the plasmon-enhanced 1O2 production using a tunable model nanoplatform, Rose Bengal-decorated silica-coated metal nanoparticles. By correlating 1O2 production to the experimental and simulated optical properties of our nanoparticles, we effectively discriminate how the near- and far-field effects contribute to the plasmonic interactions. We show that these effects work in synergy; i.e., for nanoparticles with a similar local field, the production of 1O2 correlates with maximized scattering yields. Our result...

ACS Omega2019, 4 (2), pp 3405–3408. 

The synthesis of six tetrathia–oligothiophene macrocycles is described with modest ring-closing yields between 21 and 55%. Single-crystal X-ray studies of four of the macrocycles indicated that encapsulated solvent or guest molecules were possible. A variety of guest molecules were explored for inclusion complexes via NMR, absorption, emission, and X-ray techniques. The solution-phase inclusion complexes were uninformative; yet the solid-state experiments revealed that solvent exchangeable channels exist through the macrocyclic pores.

J. Am. Chem. Soc. 2019, 141 (1), pp 684–692.

Plasmonic nanoparticles can strongly interact with adjacent photosensitizer molecules, resulting in significant alteration of their singlet oxygen (1O2) production. In this work, we report the next generation of metal-enhanced 1O2 nanoplatforms exploiting the lightning rod effect, or plasmon hot spots, in anisotropic (non-spherical) metal nanoparticles. We describe the synthesis of Rose Bengal decorated silica-coated silver nanocubes (Ag@SiO2-RB NCs) with silica shell thicknesses ranging from 5 to 50 nm based on an optimized protocol yielding highly homogeneous Ag NCs. Steady-state and time-resolve 1O2 measurements demonstrate not only the silica shell thickness dependence on the metal-enhanced 1O2 production phenomenon, but also the superiority of this next generation of nanoplatforms. A maximum enhancement of 1O2 of approximately 12-fold is observed with a 10 nm silica-shell, which is amongst the largest 1O2 production metal enhancement fac...

Molecular Therapy Oncolytics, 2018, 10, 14-27.

Oncolytic virus (OV) therapy is an emerging cancer treatment that uses replicating viruses to infect and kill tumor cells and incite anticancer immunity. While the approach shows promise, it currently fails most patients, indicating strategies to improve OV activity are needed. Developing these will require greater understanding of OV biology, particularly in the context of OV delivery and clearance, the infection process within a complex tumor microenvironment, and the modulation of anticancer immunity. To help achieve this, we have established a technique for high-resolution 4D imaging of OV-host interactions within intact tissues of live mice using intravital microscopy (IVM). We show that oncolytic vesicular stomatitis virus (VSV) directly labeled with Alexa Fluor dyes is easily visualized by single- or multiphoton microscopy while retaining bioactivity in vivo. The addition of fluorophore-tagged antibodies and genetically encoded repor...

Chem. Commun., 2018, 54, 6320-6323

Working with silica nanoparticle encapsulated BODIPY and xanthene photosensitizers, we have determined that singlet oxygen spends up to 78% of its lifetime inside the nanocarriers. Our systematic investigation indicates that hydrophobicity rules the photosensitizer distribution in nanoparticles, which in turn dictates the ability of these structures to release singlet oxygen.

Glia, 2018, 66(2), 327-347.

For decades lysophosphatidylcholine (LPC, lysolecithin) has been used to induce demyelination, without a clear understanding of its mechanisms. LPC is an endogenous lysophospholipid so it may cause demyelination in certain diseases. We investigated whether known receptor systems, inflammation or nonspecific lipid disruption mediates LPC-demyelination in mice. We found that LPC nonspecifically disrupted myelin lipids. LPC integrated into cellular membranes and rapidly induced cell membrane permeability; in mice, LPC injury was phenocopied by other lipid disrupting agents. Interestingly, following its injection into white matter, LPC was cleared within 24 hr but by five days there was an elevation of endogenous LPC that was not associated with damage. This elevation of LPC in the absence of injury raises the possibility that the brain has mechanisms to buffer LPC. In support, LPC injury in culture was significantly ameliorated by albumin buffering. These resul...

Organometallics, 2017, 36(14), 2685-2691

Two highly water-soluble phosphaviologens were synthesized via effective protocols requiring as little as two steps and only minimal purification. The new species were purposefully designed for potential application in photocatalysis as a binary system in conjunction with titanium dioxide (anatase). To this end, the efficacy of the new materials for effective charge separation was investigated via photodegradation of methylene blue. In addition to improved aqueous solubility of the phosphaviologens, we successfully inhibited the photodegradation of methylene blue in comparison to pristine TiO2 due to the highly electron accepting properties of phosphaviologens, which can effectively accept a photoexcited electron from TiO2. We also went on to compare our phosphaviologens to traditional viologens, revealing that they are equally as effective in creating a charge-separated state for TiO2.

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