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Periodontal diseases are prevalent worldwide and are linked to numerous other health conditions due to dysbiosis and chronic inflammatory state. Most periodontal diseases are caused by pathogenic bacteria that colonize dental tissues in the form of biofilm. Eradication of bacterial biofilms can be difficult to achieve due to the complex architecture of the teeth and gums which complicates the removal. Orthodontic wires and dental devices introduce additional hurdles to the adequate removal of biofilms by traditional methods since mechanical disruption via direct contact with toothbrush bristles, floss, and abrasive toothpaste is limited. Magnetically activated nanoparticles (NPs), specifically iron oxide nanoparticles (IONPs) that can be functionalized as antimicrobial particles and remotely controlled by magnetic fields, are of interest for oral biofilm eradication. We present data in multi-species bacterial cultures, established biofilms, human gingival keratinocytes, and human gingival fibroblast cells alone and in the presence of multispecies biofilm co-cultures to determine the safest, most efficacious IONP size ranges and treatment concentrations of active magnetic NPs for removal of dental biofilms. We report enhanced efficacy for IONPs coated with alginate vs. dextran, and small sizes (~8 nm vs. >20 nm in size) appear to exhibit enhanced antimicrobial efficacy. Human gingival keratinocyte (TIGK) cells in co-culture with treated and untreated multispecies biofilms in an in-vitro periodontitis model also exhibited a trend of reduced inflammatory markers in wells with IONP-treated biofilms. 

Single-molecule localization microscopy (SMLM) strategies based on fluorescence photoactivation permit the imaging of live cells with subdiffraction resolution and the high-throughput tracking of individual biomolecules in their interior. They rely predominantly on genetically-encoded fluorescent proteins to label live cells selectively and allow the sequential single-molecule localization of sparse populations of photoactivated fluorophores. Synthetic counterparts to these photoresponsive proteins are limited to a few remarkable examples at the present stage, mostly because of the daunting challenges in engineering biocompatible molecular constructs with appropriate photochemical and photophysical properties for live-cell SMLM. Our laboratory developed a new family of synthetic photoactivatable fluorophores specifically designed for these imaging applications. They combine a borondipyrromethene (BODIPY) fluorophore and an ortho-nitrobenzyl (ONB) photocage in a single molecular skeleton. The photoinduced ONB cleavage extends electronic delocalization to shift bathochromically the BODIPY absorption and emission bands. As a result, these photochemical transformations can be exploited to switch fluorescence on in a spectral region compatible with bioimaging applications and allow the localization of the photochemical product at the single-molecule level. Furthermore, our compounds can be delivered and operated in the interior of live cells to enable the visualization of organelles with nanometer resolution and the intracellular tracking of single photoactivated molecules. 

Superconducting nanostripe single-photon detectors (SNSPDs) represent key components in silicon quantum photonic integrated circuits (SiQuPICs). They provide good timing precision, low dark counts, and high efficiency. The design, fabrication, and characterization of SiQuPICs comprising SNSPDs coupled to dielectric optical waveguides are the core objectives of our work. The detectors are positioned directly on the dielectric waveguide core to increase photon absorption by the superconducting nanostripes. We also present results on the SPICE circuit modeling of traveling-wave SNSPDs integrated with Si3N4/SiO2 optical waveguides. 

N-heterocyclic carbenes (NHCs) have attracted tremendous attention over the past decade, as it is expected to form strong coordination to transition metal complexes and surfaces. Here, we investigate the interactions between colloidal gold nanoparticles (AuNPs), or luminescent quantum dots (QDs) and a multidentate NHC-based polymer ligand. The ligand design relies on the nucleophilic addition reaction between several NHC anchoring groups, short polyethylene glycol (PEG) blocks, and a polymer chain. We find that such NHC-decorated ligands rapidly coordinate onto both sets of nanocrystals, which is attributed to the inherent σ-donating nature (soft Lewis base) of NHC groups combined with the soft Lewis acidic character of nanocrystal surfaces. We combine NMR spectroscopy, fluorescence spectroscopy, high-resolution transmission electron microscopy and dynamic light scattering to characterize the NHCstabilized nanocrystals and gain insights into the nature of the binding interactions. In particular, we find that the newly coated nanocrystals exhibit long-term colloidal stability over a broad range of conditions with no sign of degradation or aggregation build up, while preserving their photophysical properties, for at least one year of storage.