Herein, we synthesized a series of 10 core–shell silver–silica nanoparticles with a photosensitizer, Rose Bengal, tethered to their surface. Each nanoparticle possesses an identical silver core of about 67 nm, but presents a different silica shell thickness ranging from 5 to 100 nm. These hybrid plasmonic nanoparticles thus afford a plasmonic nanostructure platform with a source of singlet oxygen (1O2) at a well-defined distance from the metallic core. Via time-resolved and steady state spectroscopic techniques, we demonstrate the silver core exerts a dual role of enhancing both the production of 1O2, through enhanced absorption of light, and its radiative decay, which in turn boosts 1O2 phosphorescence emission to a greater extent. Furthermore, we show both the production and emission of 1O2 in vitro to be dependent on proximity to the plasmonic nanostructure. Our results clearly exhibit three distinct regimes as the plasmonic nanostructure moves apart from the 1O2 source, with a greater enhancement for silica shell thicknesses ranging between 10 and 20 nm. Moreover, these hybrid plasmonic nanoparticles can be delivered to both Gram-positive and Gram-negative bacteria boosting both photoantibacterial activity and detection limit of 1O2 in cells.

Plasmonic nanoparticles can strongly interact with adjacent photosensitizer molecules, resulting in a significant alteration of their singlet oxygen ( 1 O 2 ) production. In this work, we report the next generation of metal-enhanced 1 O 2 nanoplatforms exploiting the lightning rod effect, or plasmon hot spots, in anisotropic (nonspherical) metal nanoparticles. We describe the synthesis of Rose Bengal-decorated silica-coated silver nanocubes (Ag@SiO 2 -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 timeresolved 1 O 2 measurements demonstrate not only the silica shell thickness dependence on the metal-enhanced 1 O 2 production phenomenon but also the superiority of this next generation of nanoplatforms. A maximum enhancement of 1 O 2 of approximately 12-fold is observed with a 10 nm silica shell, which is among the largest 1 O 2 production metal enhancement factors ever reported for a colloidal suspension of nanoparticles. Finally, the Ag@SiO 2 -RB NCs were benchmarked against the Ag@SiO 2 -RB nanospheres previously reported by our group, and the superior 1 O 2 production of Ag@SiO 2 -RB NCs resulted in improved antimicrobial activities in photodynamic inactivation experiments using both Gram-positive and -negative bacteria model strains.

In plasmon-enhanced singlet oxygen ( 1 O 2 ) production, irradiation of a hybrid photosensitizer−metal nanoparticle leads to a significant alteration of the photosensitizer's 1 O 2 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 1 O 2 production using a tunable model nanoplatform, Rose Bengal-decorated silicacoated metal nanoparticles. By correlating 1 O 2 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 1 O 2 correlates with maximized scattering yields. Our results expound the critical plasmonic aspects in terms of near and far fields for the design of an efficient hybrid plasmonic nanoparticle photosensitizer.

Objective: The coronavirus disease 2019 (COVID-19) pandemic has resulted in shortages of personal protective equipment (PPE) underscoring the urgent need for simple, efficient, and inexpensive methods to decontaminate SARS-CoV-2-exposed masks and respirators. We hypothesized that methylene blue (MB) photochemical treatment, which has various clinical applications, could decontaminate PPE contaminated with coronavirus. Design: The two arms of the study included: 1) PPE inoculation with coronaviruses followed by MB with light (MBL) decontamination treatment, and 2) PPE treatment with MBL for 5 cycles of decontamination (5CD) to determine maintenance of PPE performance. Methods: MBL treatment was used to inactivate coronaviruses on three N95 filtering facepiece respirator (FFR) and two medical mask (MM) models. We inoculated FFR and MM materials with three coronaviruses, including SARS-CoV-2, and treated with 10 µM MB and exposed to 50,000 lux of white light or 12,500 lux of red light for 30 minutes. In parallel, integrity was assessed after 5CD using multiple US and international test methods and compared to the FDA-authorized vaporized hydrogen peroxide plus ozone (VHP+O3) decontamination method. Results: Overall, MBL robustly and consistently inactivated all three coronaviruses with 99.8 - to >99.9% virus inactivation across all FFRs and MMs tested. FFR and MM integrity was maintained after 5 cycles of MBL treatment, whereas one FFR model failed after 5 cycles of VHP+O3. Conclusions: MBL treatment decontaminated respirators and masks by inactivating three tested coronaviruses without compromising integrity through 5CD. MBL decontamination is effective, low-cost and does not require specialized equipment, making it applicable in all-resource settings.

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 reporter proteins to image target cells and the virus infection enables real-time imaging of dynamic interactions between VSV and host cells in blood, tumor, and visceral organs of live mice. The method has sufficient in vivo resolution to observe leukocytes in blood binding to and transporting VSV particles, foci of VSV infection spreading through a tumor, and antigen-presenting cells in the spleen interacting with and being infected by VSV. Visualizing OV-host interactions by IVM represents a powerful new tool for studying OV therapy.