The effect of nanoparticle size on the ability to cross the blood-brain barrier: an in vivo study

AIM

Our goal was to develop an efficient nanoparticle-based system that can overcome the restrictive mechanism of the blood-brain barrier (BBB) by targeting insulin receptors and would thus enable drug delivery to the brain.

METHODS

Insulin-coated gold nanoparticles (INS-GNPs) were synthesized to serve as a BBB transport system. The effect of nanoparticle size (20, 50 and 70 nm) on their ability to cross the BBB was quantitatively investigated in Balb/C mice.

RESULTS

The most widespread biodistribution and highest accumulation within the brain were observed using 20 nm INS-GNPs, 2 h post injection. In vivo CT imaging revealed that particles migrated to specific brain regions, which are involved in neurodegenerative and neuropsychiatric disorders.

CONCLUSION

These findings promote the optimization of nanovehicles for transport of drugs through the BBB. The insulin coating of the particles enabled targeting of specific brain regions, suggesting the potential use of INS-GNPs for delivery of various treatments for brain-related disorders.

Advances in imaging strategies for in vivo tracking of exosomes

Exosomes have many biological functions as short- and long distance nanocarriers for cell-to-cell communication. They allow the exchange of complex information between cells, and thereby modulate various processes such as homeostasis, immune response and angiogenesis, in both physiological and pathological conditions. In addition, due to their unique abilities of migration, targeting, and selective internalization into specific cells, they are promising delivery vectors. As such, they provide a potentially new field in diagnostics and treatment, and may serve as an alternative to cell-based therapeutic approaches. However, a major drawback for translating exosome treatment to the clinic is that current understanding of these endogenous vesicles is insufficient, especially in regards to their in vivo behavior. Tracking exosomes in vivo can provide important knowledge regarding their biodistribution, migration abilities, toxicity, biological role, communication capabilities, and mechanism of action. Therefore, the development of efficient, sensitive and biocompatible exosome labeling and imaging techniques is highly desired. Recent studies have developed different methods for exosome labeling and imaging, which have allowed for in vivo investigation of their bio-distribution, physiological functions, migration, and targeting mechanisms. These improved imaging capabilities are expected to greatly advance exosome-based nanomedicine applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

A dynamin-related protein contributes to Trichomonas vaginalis hydrogenosomal fission

Trichomonas vaginalis is a highly divergent, unicellular eukaryote of the phylum Metamonada, class Parabasalia, and the source of a common sexually transmitted infection. This parasite lacks mitochondria, but harbors an evolutionarily related organelle, the hydrogenosome. We explored the role of dynamin-related proteins (DRPs) in the division of the hydrogenosome. Eight DRP homologues [T. vaginalis DRPs (TvDRPs)], which can be grouped into 3 subclasses, are present in T. vaginalis. We examined 5 TvDRPs that are representative of each subclass, by introducing dominant negative mutations analogous to those known to interfere with mitochondrial division in yeast, worms, and mammals. Microscopic and cell fractionation analyses of parasites expressing one of the mutated TvDRPs (TVAG_350040) demonstrated that this protein localizes to hydrogenosomes. Moreover, these organelles were found to be increased in size and reduced in number in cells expressing this dominant negative protein, relative to parasites expressing the corresponding wild-type TvDRP, the other 4 mutant TvDRPs, or an empty vector control. Our data indicate a role for a TvDRP in the fission of T. vaginalis hydrogenosomes, similar to that described for peroxisomes and mitochondria. These findings reveal a conservation of core components involved in the division of diverse eukaryotic organelles across broad phylogenetic distances.

Imaging of nanoparticle dynamics in live and apoptotic cells using temporally-modulated polarization

Gold nanoparticles are widely exploited in phototherapy. Owing to their biocompatibility and their strong visible-light surface plasmonic resonance, these particles also serve as contrast agents for cell image enhancement and super-resolved imaging. Yet, their optical signal is still insufficiently strong for many important real-life applications. Also, the differentiation between adjacent nanoparticles is usually limited by the optical resolution and the orientations of non-spherical particles are unknown. These limitations hamper the progress in cell research by direct optical microscopy and narrow the range of phototherapy applications. Here we demonstrate exploiting the optical anisotropy of non-spherical nanoparticles to achieve super-resolution in live cell imaging and to resolve the intracellular nanoparticle orientations. In particular, by modulating the light polarization and taking advantage of the polarization-dependence of gold nanorod optical properties, we realize the 'lock-in amplification', widely-used in electronic engineering, to achieve image enhancement in live cells and in cells that undergo apoptotic changes.

Reference-independent wide field fluorescence lifetime measurements using Frequency-Domain (FD) technique based on phase and amplitude crossing point

Fluorescence lifetime imaging microscopy (FLIM) is an essential tool in many scientific fields such as biology and medicine thanks to the known advantages of the fluorescence lifetime (FLT) over the classical fluorescence intensity (FI). However, the frequency domain (FD) FLIM technique suffers from its strong dependence on the reference and its compliance to the sample. In this paper, we suggest a new way to calculate the FLT by using the crossing point (CRPO) between the modulation and phase FLTs measured over several light emitting diode (LED) DC currents values instead of either method alone. This new technique was validated by measuring homogeneous substances with known FLT, where the CRPO appears to be the optimal measuring point. Furthermore, the CRPO method was applied in heterogeneous samples. It was found that the CRPO in known mixed solutions is the weighted average of the used solutions. While measuring B16 and lymphocyte cells, the CRPO of the DAPI compound in single FLT regions was measured at 3.5 ± 0.06 ns and at 2.83 ± 0.07 ns, respectively, both of which match previous reports and multi-frequency analyses. This paper suggests the CRPO as a new method to extract the FLT in problematic cases such as high MCP gains and heterogeneous environments. In traditional FD FLIM measurements, the variation in phase angle and modulation are measured. By measuring over varying DC currents, another variation is detected in the FLT determined through the phase and modulation methods, with the CRPO indicating the true FLT.

Automated tumor size assessment: Consistency of computer measurements with an expert panel

7566

Background: Manual tumor measurements for use in diagnosis and longitudinal assessment suffer from intra- and inter-observer variability. In practice they are also limited to 1-dimensional diameter measurements because manual contouring of 3D tumor boundaries is impractical. In this work we evaluated a fully automated tumor assessment system in the setting of lung nodules on CT by comparing its tumor size and density measurements against independent measurements made by an expert panel of radiologists. Methods: A new computer-aided detection (CAD) system has been developed that performs fully automated lung nodule detection and measurement. In order to identify the nodule boundary in 3D the system performs automated intensity thresholding, a Euclidean Distance Transformation, and segmentation based on watersheds. The system computes nodule diameter, volume, and mean density in Hounsfield Units (HU). The automated measurements were evaluated against data from the publically available Lung Imaging Database Consortium (LIDC), where each CT scan was reviewed and annotated (with volumetric tumor contours) by an expert panel of four radiologists. Nodule were included from consecutive subjects in the database that were ≥ 4 mm. The CT slice thickness ranged from 0.6 – 3.0 mm. For each nodule measure, the intra-class correlation coefficient (ICC) was computed among the four radiologists and then re-computed with CAD as a fifth observer. Results: 51 lung nodules from 44 subjects were analyzed. The ICCs were computed as shown in the table using a log transformation for volume and diameter. All nodule measures have similar ICCs and overlapping confidence intervals (CI). Conclusions: A new fully automated CAD system has been developed that provides CT lung nodule measurements that are consistent with an expert panel of radiologists. The automated computer system enables practical 3D tumor assessment and reduces measurement variability, which has implications for longitudinal studies. [Table: see text]

Computer-aided lung cancer screening with CT: A clinically usable nodule detection and assessment system

7562

Background: The National Lung Screening Trial (NLST) recently demonstrated that lung cancer screening with low-dose CT reduces mortality. Current protocols use 4–8 mm nodules as positive screens. While there are some computer-aided nodule detection (CAD) systems currently available, they are rarely used in clinical practice because they generate too many false positives and lack reliable measurement tools. The purpose of this work is to develop a new CAD system to overcome these limitations and evaluate it against an expert panel of radiologists. Methods: The CAD system developed for lung nodule detection and measurement incorporates computer vision techniques including intensity thresholding, Euclidean Distance Transformation, and watershed segmentation. Rules pertaining to volume and shape were applied to automatically discriminate between nodules and bronchovascular anatomy. CAD system performance was assessed using 108 consecutive cases from the publically available Lung Imaging Database Consortium (LIDC), in which four radiologists reviewed each case. CT slice thickness ranged from 0.6–3.0 mm. Nodules were included that were: (a) ≥ 4mm, and (b) marked by a majority of the LIDC readers, and (c) ≥ 4 x CT slice thickness (to ensure adequate spatial resolution). Results: 44 of 108 subjects had one or more nodules meeting criteria. Median CAD sensitivity per subject for these 44 cases is reported for all nodules ≥ 4mm and the subset of nodules ≥ 8mm. The false positive (FP) rate per subject is reported for all 108 cases. The overall concordance correlation coefficient (CCC) between the CAD volume of each nodule and the LIDC reference volume was measured. Conclusions: Based on clinical CT screening protocols, a CAD system has been developed with high nodule sensitivity and a much lower false positive rate than previously reported systems. Automated volume measurements show strong agreement with the reference standard, providing a comprehensive detection and assessment workflow for lung cancer screening. [Table: see text]