Mixed-Charge Nanocarriers Allow for Selective Targeting of Mitochondria by Otherwise Nonselective Dyes

Current advances in modulating tumor hypoxia for enhanced therapeutic efficacy

Hypoxia is a common feature of most solid tumors, which promotes the proliferation, invasion, metastasis, and therapeutic resistance of tumors. Researchers have been developing advanced strategies and nanoplatforms to modulate tumor hypoxia to enhance therapeutic effects. A timely review of this rapidly developing research topic is therefore highly desirable. For this purpose, this review first introduces the impact of hypoxia on tumor development and therapeutic resistance in detail. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are also systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We provide a detailed discussion of the rationale and research progress of these strategies. Through a review of current trends, it is hoped that this comprehensive overview can provide new prospects for clinical application in tumor treatment. STATEMENT OF SIGNIFICANCE: As a common feature of most solid tumors, hypoxia significantly promotes tumor progression. Advanced nanoplatforms have been developed to modulate tumor hypoxia to enhanced therapeutic effects. In this review, we first introduce the impact of hypoxia on tumor progression. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We discuss the rationale and research progress of the above strategies in detail, and finally introduce future challenges for treatment of hypoxic tumors. By reviewing the current trends, this comprehensive overview can provide new prospects for clinical translatable tumor therapy.

On-nanoparticle monolayers as a solute-specific, solvent-like phase

In addition to modifying surface properties, self-assembled monolayers, SAMs, on nanoparticles can selectively incorporate small molecules from the surrounding solution. This selectivity has been used in the design of substrate-specific catalytic systems but its degree has not been quantified. This work uses catalytic centers embedded in on-nanoparticle hydrophobic SAMs to monitor and quantify the partitioning of molecules between the bulk solvent and these monolayers. A combination of experiments and theory allows us to relate the logarithm of the incorporation-into-SAM constant to the "bulk" log P values, characterizing the incoming substrates. These results are in line with classic, semi-empirical linear free energy relationships between partitioning solvent systems; in this way, they substantiate the view of nanoscopic on-particle SAMs acting akin to a bulk solvent phase.

Protocol and Software for Automated Detection of Lysosome Active "Runs" and "Flights" with Wavelet Transform Approach

Lysosomes are highly dynamic degradation/recycling organelles that harbor sophisticated molecular sensors and signal transduction machinery through which they control cell adaptation to environmental cues and nutrients. The movements of these signaling hubs comprise persistent, directional runs-active, ATP-dependent transport along the microtubule tracks-interspersed by short, passive movements and pauses imposed by cytoplasmic constraints. The trajectories of individual lysosomes are usually obtained by time-lapse imaging of the acidic organelles labeled with LysoTracker dyes or fluorescently-tagged lysosomal-associated membrane proteins LAMP1 and LAMP2. Subsequent particle tracking generates large data sets comprising thousands of lysosome trajectories and hundreds of thousands of data points. Analyzing such data sets requires unbiased, automated methods to handle large data sets while capturing the temporal heterogeneity of lysosome trajectory data. This chapter describes integrated and largely automated workflow from live cell imaging to lysosome trajectories to computing the parameters of lysosome dynamics. We describe an open-source code for implementing the continuous wavelet transform (CWT) to distinguish trajectory segments corresponding to active transport (i.e., "runs" and "flights") versus passive lysosome movements. Complementary cumulative distribution functions (CDFs) of the "runs/flights" are generated, and Akaike weight comparisons with several competing models (lognormal, power law, truncated power law, stretched exponential, exponential) are performed automatically. Such high-throughput analyses yield useful aggregate/ensemble metrics for lysosome active transport.

Recent advances in nanotechnology mediated mitochondria-targeted imaging

Mitochondria play a critical role in cell growth and metabolism. And mitochondrial dysfunction is closely related to various diseases, such as cancers, and neurodegenerative and cardiovascular diseases. Therefore, it is of vital importance to monitor mitochondrial dynamics and function. One of the most widely used methods is to use nanotechnology-mediated mitochondria targeting and imaging. It has gained increasing attention in the past few years because of the flexibility, versatility and effectiveness of nanotechnology. In the past few years, researchers have implemented various types of design and construction of the mitochondrial structure dependent nanoprobes following assorted nanotechnology pathways. This review presents an overview on the recent development of mitochondrial structure dependent target imaging probes and classifies it into two main sections: mitochondrial membrane targeting and mitochondrial microenvironment targeting. Also, the significant impact of previous research as well as the application and perspectives will be demonstrated.

Shining Light on Polymeric Drug Nanocarriers with Fluorescence Correlation Spectroscopy

The use of nanoparticles as carriers is an extremely promising way for administration of therapeutic agents, such as drug molecules, proteins and nucleic acids. Such nanocarriers (NCs) can increase the solubility of hydrophobic compounds, protect their cargo from the environment, and if properly functionalized, deliver it to specific target cells and tissues. Polymer-based NCs are especially promising, because they offer high degree of versatility and tunability. However, in order to get a full advantage of this therapeutic approach and develop efficient delivery systems, a careful characterization of the NCs is needed. This Feature Article highlights the fluorescence correlation spectroscopy (FCS) technique as a powerful and versatile tool for NCs characterization at all stages of the drug delivery process. In particular, FCS can monitor and quantify the size of the NCs and the drug loading efficiency after preparation, the NCs stability and possible interactions with, e.g., plasma proteins in the blood stream and the kinetic of drug release in the cytoplasm of the target cells. This article is protected by copyright. All rights reserved.

Large-Scale, Wavelet-Based Analysis of Lysosomal Trajectories and Co-Movements of Lysosomes with Nanoparticle Cargos

Lysosomes—that is, acidic organelles known for degradation/recycling—move through the cytoplasm alternating between bursts of active transport and short, diffusive motions or even pauses. While their mobility is essential for lysosomes’ fusogenic and non-fusogenic interactions with target organelles, their movements have not been characterized in adequate detail. Here, large-scale statistical analysis of lysosomal movement trajectories reveals that lysosome trajectories in all examined cell types—both cancer and noncancerous ones—are superdiffusive and characterized by heavy-tailed distributions of run and flight lengths. Consideration of Akaike weights for various potential models (lognormal, power law, truncated power law, stretched exponential, and exponential) indicates that the experimental data are best described by the lognormal distribution, which, in turn, can be related to one of the space-search strategies particularly effective when “thorough” search needs to balance search for rare target(s) (organelles). In addition, automated, wavelet-based analysis allows for co-tracking the motions of lysosomes and the cargos they carry—particularly the nanoparticle aggregates known to cause selective lysosome disruption in cancerous cells. The methods we describe here could help study nanoparticle assemblies, viruses, and other objects transported inside various vesicle types, as well as coordinated movements of organelles/particles in the cytoplasm. Custom-written code that includes integrated workflow for our analyses is made available for academic use.