Multimodal optical studies of single and clustered colloidal quantum dots for the long-term optical property evaluation of quantum dot-based molecular imaging phantoms

Fluorescent nanotechnology for in vivo imaging

Fluorescent imaging in living animals gives an intuitive picture of the dynamic processes in the complex environment within a living being. However, animal tissues present a substantial barrier and are opaque to most wavelengths of visible light. Fluorescent nanoparticles (NPs) with new photophysical characteristics have shown excellent performance for in vivo imaging. Hence, fluorescent NPs have been widely studied and applied for the detection of molecular and biological processes in living animals. In addition, developments in the area of nanotechnology have allowed materials to be used in intact animals for disease detection, diagnosis, drug delivery, and treatment. This review provides information on the different types of fluorescent particles based on nanotechnology, describing their unique individual properties and applications for detecting vital processes in vivo. The development and application of new fluorescent NPs will provide opportunities for in vivo imaging with better penetration, sensitivity, and resolution. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

Enhanced Emission of Zinc Nitride Colloidal Nanoparticles with Organic Dyes for Optical Sensors and Imaging Application

Herein, we have reported on the efficiency of inorganic Zn₃N₂ nanoparticles for labeling plant cells and animal cells toward imaging applications with negligible toxicity. We have synthesized zinc nitride (Zn₃N₂) colloidal nanoparticles with an average size of 25 nm at room temperature. The optical band gap of the prepared Zn₃N₂ nanoparticles is 2.8 eV and gives a visible range emission at 415 nm. With the addition of Zn₃N₂ colloids to organic dyes such as protoporphyrin, flavin adenine dinucleotide, fluorescein, and neutral red, the emission intensity of the organic dyes enhanced from 3 to 20 times. The molecular simulation and lifetime studies evidence the possibility of energy transfer from zinc nitride to organic dyes. The enhancement of dye intensity in the presence of Zn₃N₂ enhanced the vicinity of the cellular environment during confocal imaging of plant cells and animal cells. The detailed results suggested Zn₃N₂ for bioimaging and biosensor applications.

Photon Antibunching in Small Clusters of CdSe/ZnS Core/Shell Quantum Dots

Coincident photon histogram measurements of fluorescence antibunching via confocal microscopy correlated with atomic force microscopy were carried out on (i) individual CdSe/ZnS core/shell quantum dots (QDs), (ii) several well separated QDs, and (iii) clusters of QDs. Individual QDs and well separated QDs showed the expected degree of antibunching for a single emitter and several independent emitters, respectively. The degree of antibunching in small, compact clusters was more characteristic of a single emitter than multiple emitters. The antibunching in clusters provides strong evidence of nonradiative energy transfer between QDs in a cluster. A minimal phenomenological model of energy transfer gives reasonable quantitative agreement with the experimental results.

Quantum dot-based nanoprobes for in vivo targeted imaging

Fluorescent semiconductor quantum dots (QDs) have attracted tremendous attention over the last decade. The superior optical properties of QDs over conventional organic dyes make them attractive labels for a wide variety of biomedical applications, whereas their potential toxicity and instability in biological environment have puzzled scientific researchers. Much research effort has been devoted to surface modification and functionalization of QDs to make them versatile probes for biomedical applications, and significant progress has been made over the last several years. This review article aims to describe the current state-of-the-art of the synthesis, modification, bioconjugation, and applications of QDs for in vivo targeted imaging. In addition, QD-based multifunctional nanoprobes are also summarized.

Electrospray differential mobility analysis for nanoscale medicinal and pharmaceutical applications

Nanoscale characterization tools hold the potential to overcome long-standing medicinal and pharmaceutical challenges. For example, electrospray differential mobility analysis (ES-DMA) is an emerging tool that rapidly provides label-free multimodal size distributions for proteins and particles from ~1 nm to <500 nm with subnanometer precision. Here we critically review the contributions of this tool to medicine, pharmaceutical practice, and pharmaceutical production. Our review critically evaluates, first, the use of ES-DMA for diagnostic strategies that detect and quantify lipoproteins, bacterial infections, viruses and amyloid fibrillation and then focuses on ES-DMA's contribution to treatment strategies that employ tailored virus-like particles as vaccines and decorated nanoparticle vectors for gene delivery. Our review also highlights ES-DMA's contribution to viral clearance and antibody aggregation and potential as a process analytical technology (PAT).

FROM THE CLINICAL EDITOR

Electrospray differential mobility analysis is an emerging nanotechnology-based tool with potential clinical utility in the detection and quantification of lipoproteins, glycoproteins, viruses, amyloids, bacterial infections. Its contribution to treatment strategies and pharmaceutical production is also discussed in this comprehensive review.

Color-matched and fluorescence-labeled esophagus phantom and its applications

We developed a stable, reproducible three-dimensional optical phantom for the evaluation of a wide-field endoscopic molecular imaging system. This phantom mimicked a human esophagus structure with flexibility to demonstrate body movements. At the same time, realistic visual appearance and diffuse spectral reflectance properties of the tissue were simulated by a color matching methodology. A photostable dye-in-polymer technology was applied to represent biomarker probed "hot-spot" locations. Furthermore, fluorescent target quantification of the phantom was demonstrated using a 1.2 mm ultrathin scanning fiber endoscope with concurrent fluorescence-reflectance imaging.

Glassy Interfacial Dynamics of Ni Nanoparticles: Part I Colored Noise, Dynamic Heterogeneity and Collective Atomic Motion

Most condensed materials exhibit a significant fraction of atoms, molecules or particles that are strongly interacting with each other, while being configured geometrically at any instant of time in an 'amorphous' state having a relatively uniform density. Recently, both simulations and experiments have revealed that the dynamics of diverse condensed amorphous materials is generally characterized by significant heterogeneity in the local mobility and by progressively increasing collective motion upon cooling that takes the form of string-like collective particle rearrangements. The direct experimental observation of this type of collective motion, which has been directly linked to the growing relaxation times of glass-forming materials, and its quantification under different thermodynamic conditions, has so far been restricted to colloidal and driven granular fluids. The present work addresses the fundamental problem of how to determine the scale of this type of collective motion in materials composed of molecules or atoms. The basic premise of our work is that large scale dynamic particle clustering in amorphous materials must give rise to large fluctuations in particle mobility so that transport properties, especially those related to particle mobility, should naturally exhibit noise related to the cooperative motion scale. In our initial exploratory study seeking a relationship of this kind, we find 1/fα or 'colored noise', in both potential energy and particle displacements fluctuations of the atoms within the glassy interfacial layer of Ni nanoparticles (NPs). A direct relation between the particle displacement (mobility) noise exponent α and the average polymerization index of the string-like collective motion L is observed for a range of NP sizes, temperatures and for surface doping of the NPs with other metal atoms (Ag, Au, Pt) to change of fragility of the glassy interfacial layer at the surface of the Ni NPs. We also introduce a successful analytic model to understand this relationship between α and L.