Membrane vesicles nanotheranostic systems: sources, engineering methods, and challenges.

Extracellular vesicles (EVs) are cell secretory native components with long-circulation, good biocompatibility, and physiologic barriers cross ability. EVs derived from different donor cells inherit varying characteristics and functions from their original cells and are favorable to serve as vectors for diagnosing and treating various diseases. However, EVs nanotheranostics are still in their infancy because of their limited accumulation at lesion sites and compromised therapy efficiency. Hence, engineering modification of EVs is usually needed to further enhance their stability, biological activity, and lesion-targeting capacity. Herein, we overview the characteristics of EVs from different sources, as well as the latest developments of surface engineering and cargo loading methods. We also focus especially on advances in EVs-based disease theranostics. At the end of the review, we predict the obstacles and prospects of the future clinical application of EVs.

Inch-sized aligned polymer nanofiber films with embedded CH3NH3PbBr3 nanocrystals: electrospinning fabrication using a folded aluminum foil as the collector.

Perovskite nanocrystal embedded polymer nanofibers with polarized emissions are interesting materials for down-shifting applications. By using a folded aluminum foil as a collector, we fabricated inch-size aligned polymer nanofiber films with embedded CH3NH3PbBr3 nanocrystals by adapting an electrospinning technique. It was found that the addition of an appropriate amount of cyanoethyl cellulose (CEC) makes the dispersion of MAPbBr3 in the nanofibers more uniform. Using a precursor solution with MAPbBr3 of 10% and CEC of 1 wt%, the resulting nanofiber films show strong polarized emission with quantum yields up to 51%. The emission dichroic ratio and emission polarization ratio can reach 5.21 and 0.43, respectively. These polarized emissive films can be potentially applied as down converters for liquid crystal display backlights and other polarization selective photonic devices.

Mesoporous Aluminum Hydroxide Synthesized by a Single-Source Precursor-Decomposition Approach as a High-Quantum-Yield Blue Phosphor for UV-Pumped White-Light-Emitting Diodes.

Strongly emissive (photoluminescence quantum yield up to 65%), thermally stable aluminum hydroxide blue phosphors are synthesized by a single-source precursor-decomposition approach. Blue-emitting UV-pumped light-emitting diodes (LEDs) based on the aluminum hydroxide phosphor reach luminous efficiency of 27.5 lm W-1 , while UV-white-LEDs integrating blue-emitting aluminum hydroxide and red-emitting CuInS2 nanocrystals achieve high color-rendering-index values of 94.3 and luminous efficiency of 23.5 lm W-1 .

Tumor-Targeted Multimodal Optical Imaging with Versatile Cadmium-Free Quantum Dots.

The rapid development of fluorescence imaging technologies requires concurrent improvements in the performance of fluorescent probes. Quantum dots have been extensively used as an imaging probe in various research areas because of their inherent advantages based on unique optical and electronic properties. However, their clinical translation has been limited by the potential toxicity especially from cadmium. Here, a versatile bioimaging probe is developed by using highly luminescent cadmium-free CuInSe2/ZnS core/shell quantum dots conjugated with CGKRK (Cys-Gly-Lys-Arg-Lys) tumor-targeting peptides. This probe exhibits excellent photostability, reasonably long circulation time, minimal toxicity, and strong tumor-specific homing property. The most important feature of this probe is that it shows distinctive versatility in tumor-targeted multimodal imaging including near-infrared, time-gated, and two-photon imaging in different tumor models. In a glioblastoma mouse model, the targeted probe clearly denotes tumor boundaries and positively labels a population of diffusely infiltrating tumor cells, suggesting its utility in precise tumor detection during surgery. This work lays a foundation for potential clinical translation of the probe.

Small GSH-Capped CuInS2 Quantum Dots: MPA-Assisted Aqueous Phase Transfer and Bioimaging Applications.

An efficient ligand exchange strategy for aqueous phase transfer of hydrophobic CuInS2/ZnS quantum dots was developed by employing glutathione (GSH) and mercaptopropionic acid (MPA) as the ligands. The whole process takes less than 20 min and can be scaled up to gram amount. The material characterizations show that the final aqueous soluble samples are solely capped with GSH on the surface. Importantly, these GSH-capped CuInS2/ZnS quantum dots have small size (hydrodynamic diameter <10 nm), moderate fluorescent properties (up to 34%) as well as high stability in aqueous solutions (stable for more than three months in 4 °C without any significant fluorescence quenching). Moreover, this ligand exchange strategy is also versatile for the aqueous phase transfer of other hydrophobic quantum dots, for instance, CuInSe2 and CdSe/ZnS quantum dots. We further demonstrated that GSH-capped quantum dots could be suitable fluorescence markers to penetrate cell membrane and image the cells. In addition, the GSH-capped CuInS2 quantum dots also have potential use in other fields such as photocatalysis and quantum dots sensitized solar cells.

Labeling of hematopoietic stem cells by Tat peptide conjugated quantum dots for cell tracking in mouse body.

Fluorescent quantum dots have great potential to act as labeling tools in biological research, especially cellular tracking and imaging. Tat peptide conjugated quantum dots were introduced into living human hematopoietic stem cells (HSCs). The internalized quantum dots were assessed by laser confocal microscope and flow cytometer. The quantum dots labeled HSCs were injected intravenously into the tail veins of NOD/SCID beta2M null mice. The tissue collections in the major organs were examined with fluorescence microscope to assess the distribution of transplanted stem cells. HSCs with internalized quantum dots offer a promising approach for stem cell transplantation, which will hold a significant impact on stem cell based therapy for several disorders, especially to cure leukemia in current China.

Fluorescence resonance energy transfer in conjugated polymer composites for radiation detection.

Fluorescence resonance energy transfer in conjugated polymer composite materials was exploited for the detection of gamma ray dosage with high sensitivity and response linearity.

Ultralong cadmium hydroxide nanowires: synthesis, characterization, and transformation into CdO nanostrands.

Ultralong Cd(OH)2 nanowires were fabricated by a hydrothermal method from Cd(CH3COO)2 x H2O (0.01 mol/L) and C6H12N4 (0.015 mol/L) aqueous solution at 95 degrees C for 16 h without using any templates and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The length of the nanowires reached several micrometers, giving an aspect ratio of a few thousands. The formation mechanism of the nanowires is attributed to the oriented attachment of small particles. The growth method for the 1D nanostructure presented here offers an excellent tool for the design of other advanced materials with anisotropic properties. The Cd(OH)2 nanowires efficiently captured negatively charged dye, and the adsorbed dye molecules can be released after the addition of EDTA. The Cd(OH)2 nanowires as template compounds were further transformed into CdO semiconductor nanomaterials with similar morphology by calcination under 350 degrees C in air for 3 h.