Engineering dendrimers to produce dendrimer dipole excitation based terahertz radiation sources suitable for spectrometry, molecular and biomedical imaging

Bragg-Mirror-Assisted High-Contrast Plasmonic Interferometers: Concept and Potential in Terahertz Sensing

A Bragg-mirror-assisted terahertz (THz) high-contrast and broadband plasmonic interferometer is proposed and theoretically investigated for potential sensing applications. The central microslit couples the incident THz wave into unidirectional surface plasmon polaritons (SPPs) waves travelling to the bilateral Bragg gratings, where they are totally reflected over a wide wavelength range back towards the microslit. The properties of interference between the SPPs waves and transmitted THz wave are highly dependent on the surrounding material, offering a flexible approach for the realization of refractive index (RI) detection. The systematic study reveals that the proposed interferometric sensor possesses wavelength sensitivity as high as 167 μm RIU^-1 (RIU: RI unit). More importantly, based on the intensity interrogation method, an ultrahigh Figure-of-Merit (FoM) of 18,750% RIU^-1, surpassing that of previous plasmonic sensors, is obtained due to the high-contrast of interference pattern. The results also demonstrated that the proposed sensors are also quite robust against the oblique illumination. It is foreseen the proposed configuration may open up new horizons in developing THz plasmonic sensing platforms and next-generation integrated THz circuits.

The Role of Branch Cell Symmetry and Other Critical Nanoscale Design Parameters in the Determination of Dendrimer Encapsulation Properties

This article reviews progress over the past three decades related to the role of dendrimer-based, branch cell symmetry in the development of advanced drug delivery systems, aqueous based compatibilizers/solubilizers/excipients and nano-metal cluster catalysts. Historically, it begins with early unreported work by the Tomalia Group (i.e., The Dow Chemical Co.) revealing that all known dendrimer family types may be divided into two major symmetry categories; namely: Category I: symmetrical branch cell dendrimers (e.g., Tomalia, Vögtle, Newkome-type dendrimers) possessing interior hollowness/porosity and Category II: asymmetrical branch cell dendrimers (e.g., Denkewalter-type) possessing no interior void space. These two branch cell symmetry features were shown to be pivotal in directing internal packing modes; thereby, differentiating key dendrimer properties such as densities, refractive indices and interior porosities. Furthermore, this discovery provided an explanation for unimolecular micelle encapsulation (UME) behavior observed exclusively for Category I, but not for Category II. This account surveys early experiments confirming the inextricable influence of dendrimer branch cell symmetry on interior packing properties, first examples of Category (I) based UME behavior, nuclear magnetic resonance (NMR) protocols for systematic encapsulation characterization, application of these principles to the solubilization of active approved drugs, engineering dendrimer critical nanoscale design parameters (CNDPs) for optimized properties and concluding with high optimism for the anticipated role of dendrimer-based solubilization principles in emerging new life science, drug delivery and nanomedical applications.

Critical evaluation of the interaction of special proteins with human stratum corneum via terahertz scanning reflectometry and spectrometry

Many patients with chronic skin disease develop hemostatic abnormalities. The blood coagulation factor XII is a multifunctional protease, which is involved in thrombosis, fibrinolysis, and inflammatory processes. The aim of this investigation was to assess the autoactivation of FXII that leads to the generation of FXII fragments and their subsequent cell penetration compared to UM8190, a lipophilic selective prolyl carboxypeptidase inhibitor compound. Terahertz scanning reflectometry (TSR) and terahertz spectrometry (TS) were used to study the surface-mediated FXII activation, as well as penetration of the FXII and UM8190, their retardant property, diffusion kinetics and fragmentation profiles into human stratum corneum (SC). From the diffusion kinetics and profiling experiments it was found that FXII does not penetrate the SC but remains mostly on the surface. Compound UM8190 indicates penetration into the SC, as indicated by the increased reflected intensity of T-ray. The terahertz spectral analysis via absorbance spectra indicates that at a low frequency of 0.56 THz a prominent peak occurs due to water or moisture for the SC alone. This peak, however, exhibits a shift for post-diffusion samples of both FXII saturated SC and UM8190-saturated SC. This is indicative of adhesion of these proteins onto the SC. Though this process corroborates the binding of FXII to the cell membrane surface as reported in the in vitro findings, it does not appear to be activated and degraded. It was also found that there are a number of absorbance peaks characteristic for each molecule and these peaks are uniquely shifted relative to each other when compared with the SC alone. Thus, these absorbance peaks may be utilized for assigning identifying features of the protein and peptides in this present study. Further investigation will be conducted for assigning the absorbance peaks to the specific proteins and their resonances.

How a grafting anchor tailors the cellular uptake and in vivo fate of dendronized iron oxide nanoparticles

Superparamagnetic iron oxide nanoparticles synthesized by thermal decomposition have been grafted with two dendrons bearing respectively a monophosphonic anchor (D2) or a biphosphonic tweezer (D2-2P) at their focal point.