Pyrene as a membrane depth gauge: Wavelength selective fluorescence approach to monitor pyrene localizations in the membrane

Preparation, characterization, and evaluation of flaxseed oil liposomes coated with chitosan and pea protein isolate hydrolysates

The effect of layer-by-layer coating of liposomes with chitosan and pea protein isolate hydrolysates (PPIH) was evaluated. Traditional flaxseed oil liposomes (FL Lipo) were used as a model for comparison to liposomes coated with chitosan and PPIH (FL LipoCP). The potential of PPIH as a coating material was evaluated. Additionally, the influence of chitosan and PPIH on vesicle size and zeta potential of liposomes was investigated. The chitosan layer of liposomes exhibited a loose structure. After the second layer of coating with PPIH, chitosan molecules were rearranged on the liposome surface, leading to a more compact and dense shell structure of liposomes. Electrostatic interactions, hydrogen bonds, and hydrophobic interactions favored the stability of FL LipoCP. Compared to FL Lipo, FL LipoCP displayed higher oxidation stability during storage and a slower release of flaxseed oil during in vitro digestion.

Single-walled carbon-nanohorns improve biocompatibility over nanotubes by triggering less protein-initiated pyroptosis and apoptosis in macrophages

Single-walled carbon-nanohorns (SNH) exhibit huge application prospects. Notably, spherical SNH possess different morphology from conventional carbon nanotubes (CNT). However, there is a tremendous lack of studies on the nanotoxicity and mechanism of SNH, and their comparison with nanotubes. Here, the dissimilarity between SNH and CNT is found in many aspects including necrosis, pyroptosis, apoptosis, protein expression, hydrolases leakage, lysosome stress, membrane disturbance and the interaction with membrane proteins. The improved biocompatibility of SNH over four types of established CNT is clearly demonstrated in macrophages. Importantly, a key transmembrane protein, glycoprotein nonmetastatic melanoma protein B (GPNMB) is discovered to initiate the nanotoxicity. Compared to CNT, the weaker nano-GPNMB interaction in SNH group induces lower degree of cascade actions from nano/membrane interplay to final cell hypotoxicity. In conclusion, the geometry of single-construct unit, but not that of dispersive forms or intracellular levels of nanocarbons make the most difference.

Mastering Dendrimer Self-Assembly for Efficient siRNA Delivery: From Conceptual Design to In Vivo Efficient Gene Silencing

Self-assembly is a fundamental concept and a powerful approach in molecular science. However, creating functional materials with the desired properties through self-assembly remains challenging. In this work, through a combination of experimental and computational approaches, the self-assembly of small amphiphilic dendrons into nanosized supramolecular dendrimer micelles with a degree of structural definition similar to traditional covalent high-generation dendrimers is reported. It is demonstrated that, with the optimal balance of hydrophobicity and hydrophilicity, one of the self-assembled nanomicellar systems, totally devoid of toxic side effects, is able to deliver small interfering RNA and achieve effective gene silencing both in cells - including the highly refractory human hematopoietic CD34(+) stem cells - and in vivo, thus paving the way for future biomedical implementation. This work presents a case study of the concept of generating functional supramolecular dendrimers via self-assembly. The ability of carefully designed and gauged building blocks to assemble into supramolecular structures opens new perspectives on the design of self-assembling nanosystems for complex and functional applications.

The Three Possible 2-(Pyrenylethynyl) Adenosines: Rotameric Energy Barriers Govern the Photodynamics of These Structural Isomers

This article presents a comprehensive study of the photophysics of 2-(2-pyrenylethynyl) adenosine and 2-(4-pyrenylethynyl) adenosine, which are structural isomers of the well-established fluorescent RNA label 2-(1-pyrenylethynyl) adenosine. We performed steady-state and ultrafast transient absorption spectroscopy studies along with time-resolved fluorescence emission experiments in different solvents to work out the interplay of locally excited and charge-transfer states. We found the ultrafast photodynamics to be crucial for the fluorescence decay behavior, which extends up to tens of nanoseconds and is partially multi-exponential. These features in the ultrafast dynamics are indicative of the rotational energy barriers in the first excited state.

Depth-Dependent Heterogeneity in Membranes by Fluorescence Lifetime Distribution Analysis

Biological membranes display considerable anisotropy due to differences in composition, physical characteristics, and packing of membrane components. In this Letter, we have demonstrated the environmental heterogeneity along the bilayer normal in a depth-dependent manner using a number of anthroyloxy fatty acid probes. We employed fluorescence lifetime distribution analysis utilizing the maximum entropy method (MEM) to assess heterogeneity. Our results show that the fluorescence lifetime heterogeneity varies considerably depending on fluorophore location along the membrane normal (depth), and it is the result of the anisotropic environmental heterogeneity along the bilayer normal. Environmental heterogeneity is reduced as the reporter group is moved from the membrane interface to a deeper hydrocarbon region. To the best of our knowledge, our results constitute the first experimental demonstration of anisotropic heterogeneity in bilayers. We conclude that such graded environmental heterogeneity represents an intrinsic characteristics of the membrane bilayer and envisage that it has a role in the conformation and orientation of membrane proteins and their function.