Ranhua Xiong

Electrospun fibers for oil–water separation

The increasing worldwide oil pollution intensifies the needs for new techniques of separation of oil from oily water. Separation by the use of electrospun fibers with selective oil/water absorption is a relatively new but highly promising technique. Owing to their highly specific surface areas, interconnected nanoscale pore structures and the potential to incorporate active chemistry on a nanoscale surface, electrospun fibers have become a promising versatile platform for the separation of oil/water mixtures and emulsions. In this review, after a short introduction to the imperative for oil/water separation and electrospinning technique, we will focus on superhydrophobic/superoleophilic electrospun fibers for oil/water separation, including the preparation of electrospun fibers with superhydrophobic/superoleophilic surfaces, and superhydrophobic/superoleophilic fibrous membranes for oil absorption and oil filtration. Further, superoleophobic/superhydrophilic electrospun fibers and their application for oil–water separation will be discussed as well. Finally, conclusions about this review will be presented while addressing remaining problems and future challenges.

Comparison of Gold Nanoparticle Mediated Photoporation: Vapor Nanobubbles Outperform Direct Heating for Delivering Macromolecules in Live Cells

There is a great interest in delivering macromolecular agents into living cells for therapeutic purposes, such as siRNA for gene silencing. Although substantial effort has gone into designing nonviral nanocarriers for delivering macromolecules into cells, translocation of the therapeutic molecules from the endosomes after endocytosis into the cytoplasm remains a major bottleneck. Laser-induced photoporation, especially in combination with gold nanoparticles, is an alternative physical method that is receiving increasing attention for delivering macromolecules in cells. By allowing gold nanoparticles to bind to the cell membrane, nanosized membrane pores can be created upon pulsed laser illumination. Depending on the laser energy, pores are created through either direct heating of the AuNPs or by vapor nanobubbles (VNBs) that can emerge around the AuNPs. Macromolecules in the surrounding cell medium can then diffuse through the pores directly into the cytoplasm. Here we present a systematic evaluation of both photoporation mechanisms in terms of cytotoxicity, cell loading, and siRNA transfection efficiency. We find that the delivery of macromolecules under conditions of VNBs is much more efficient than direct photothermal disturbance of the plasma membrane without any noticeable cytotoxic effect. Interestingly, by tuning the laser energy, the pore size could be changed, allowing control of the amount and size of molecules that are delivered in the cytoplasm. As only a single nanosecond laser pulse is required, we conclude that VNBs are an interesting photoporation mechanism that may prove very useful for efficient high-throughput macromolecular delivery in live cells.

Towards Theranostic Multicompartment Microcapsules: in-situ Diagnostics and Laser-induced Treatment

Paving the way towards the application of polyelectrolyte multilayer capsules in theranostics, we describe diagnostic multi-functionality and drug delivery using multicompartment polymeric capsules which represent the next generation of drug delivery carriers. Their versatility is particularly important for potential applications in the area of theranostics wherein the carriers are endowed with the functionality for both diagnostics and therapy. Responsiveness towards external stimuli is attractive for providing controlled and on-demand release of encapsulated materials. An overview of external stimuli is presented with an emphasis on light as a physical stimulus which has been widely used for activation of microcapsules and release of their contents. In this article we also describe existing and new approaches to build multicompartment microcapsules as well as means available to achieve controlled and triggered release from their subcompartments, with a focus on applications in theranostics. Outlook for future directions in the area are highlighted.

A beneficiary role for neuraminidase in influenza virus penetration through the respiratory mucus.

Swine influenza virus (SIV) has a strong tropism for pig respiratory mucosa, which consists of a mucus layer, epithelium, basement membrane and lamina propria. Sialic acids present on the epithelial surface have long been considered to be determinants of influenza virus tropism. However, mucus which is also rich in sialic acids may serve as the first barrier of selection. It was investigated how influenza virus interacts with the mucus to infect epithelial cells. Two techniques were applied to track SIV H1N1 in porcine mucus. The microscopic diffusion of SIV particles in the mucus was analyzed by single particle tracking (SPT), and the macroscopic penetration of SIV through mucus was studied by a virus in-capsule-mucus penetration system, followed by visualizing the translocation of the virions with time by immunofluorescence staining. Furthermore, the effects of neuraminidase on SIV getting through or binding to the mucus were studied by using zanamivir, a neuraminidase inhibitor (NAI), and Arthrobacter ureafaciens neuraminidase. The distribution of the diffusion coefficient shows that 70% of SIV particles were entrapped, while the rest diffused freely in the mucus. Additionally, SIV penetrated the porcine mucus with time, reaching a depth of 65 µm at 30 min post virus addition, 2 fold of that at 2 min. Both the microscopic diffusion and macroscopic penetration were largely diminished by NAI, while were clearly increased by the effect of exogenous neuraminidase. Moreover, the exogenous neuraminidase sufficiently prevented the binding of SIV to mucus which was reversely enhanced by effect of NAI. These findings clearly show that the neuraminidase helps SIV move through the mucus, which is important for the virus to reach and infect epithelial cells and eventually become shed into the lumen of the respiratory tract.

Laser-assisted photoporation: fundamentals, technological advances and applications

Abstract Laser-assisted photoporation is a promising technique that is receiving increasing attention for the delivery of membrane impermeable nanoscopic substances into living cells. Photoporation is based on the generation of localized transient pores in the cell membrane using continuous or pulsed laser light. Increased membrane permeability can be achieved directly by focused laser light or in combination with sensitizing nanoparticles for higher throughput. Here, we provide a detailed account on the history and current state-of-the-art of photoporation as a physical nanomaterial delivery technique. We first introduce with a detailed explanation of the mechanisms responsible for cell membrane pore formation, following an overview of experimental procedures for realizing direct laser photoporation. Next, we review the second and most recent method of photoporation that combines laser light with sensitizing NPs. The different mechanisms of pore formation are discussed and an overview is given of the various types of sensitizing nanomaterials. Typical experimental setups to achieve nanoparticle-mediated photoporation are discussed as well. Finally, we discuss the biological and therapeutic applications enabled by photoporation and give our current view on this expanding research field and the challenges and opportunities that remain for the near future.

Cytosolic Delivery of Nanolabels Prevents Their Asymmetric Inheritance and Enables Extended Quantitative in Vivo Cell Imaging

Long-term in vivo imaging of cells is crucial for the understanding of cellular fate in biological processes in cancer research, immunology, or in cell-based therapies such as beta cell transplantation in type I diabetes or stem cell therapy. Traditionally, cell labeling with the desired contrast agent occurs ex vivo via spontaneous endocytosis, which is a variable and slow process that requires optimization for each particular label-cell type combination. Following endocytic uptake, the contrast agents mostly remain entrapped in the endolysosomal compartment, which leads to signal instability, cytotoxicity, and asymmetric inheritance of the labels upon cell division. Here, we demonstrate that these disadvantages can be circumvented by delivering contrast agents directly into the cytoplasm via vapor nanobubble photoporation. Compared to classic endocytic uptake, photoporation resulted in 50 and 3 times higher loading of fluorescent dextrans and quantum dots, respectively, with improved signal stability and reduced cytotoxicity. Most interestingly, cytosolic delivery by photoporation prevented asymmetric inheritance of labels by daughter cells over subsequent cell generations. Instead, unequal inheritance of endocytosed labels resulted in a dramatic increase in polydispersity of the amount of labels per cell with each cell division, hindering accurate quantification of cell numbers in vivo over time. The combined benefits of cell labeling by photoporation resulted in a marked improvement in long-term cell visibility in vivo where an insulin producing cell line (INS-1E cell line) labeled with fluorescent dextrans could be tracked for up to two months in Swiss nude mice compared to 2 weeks for cells labeled by endocytosis.

Green electrospun and crosslinked poly(vinyl alcohol)/poly(acrylic acid) composite membranes for antibacterial effective air filtration

Air pollution has become a major environmental concern given the ever increasing levels of particulate matter (PM) and the increased in treatment-resistant bacterial and viral strains. Major efforts are therefore required into the development of air filtration and purification technology as well as novel, alternative antiviral and antibacterial treatment modalities. Here, we report an environmentally friendly method for the generation of multifunctional poly(vinyl alcohol)/poly(acrylic acid) (PVA-PAA) composite membranes via green electrospinning and thermal crosslinking. Superhydrophobic silica nanoparticles were then incorporated into the fibers resulting in a rough surface, after which AgNO3 was introduced, resulting in the formation of Ag nanoparticles through UV reduction. The PVA-PAA-SiO2-Ag NPs membranes were found to possess high air filtration performance (with >98% filtration efficiency for PM2.5) as well as potent antibacterial and antiviral activities. The green synthesis approach avoids the use of hazardous organic solvents, thereby bypassing any potential toxicity concerns caused by organic solvent residues. These newly designed PVA-PAA-SiO2 NPs-Ag NPs nanofibrous membranes with many superior features (e.g. high filtration efficiency, high tensile strength, biological compatibility, and antibacterial properties) can be applied in eco-friendly air filtration materials, in particular for personal air filtration devices.

Comparing photoporation and nucleofection for delivery of small interfering RNA to cytotoxic T cells

ABSTRACT The success of cancer immunotherapy through the adoptive transfer of cytotoxic T lymphocytes (CTLs) is highly dependent on the potency of the elicited anti‐tumor responses generated by the transferred cells, which can be hindered by a variety of upregulated immunosuppressive pathways. Downregulation of these pathways in the T cells via RNA interference (RNAi) could significantly boost their capacity to infiltrate tumors, proliferate, persist, and eradicate tumor cells, thus leading to a durable anti‐tumor response. Unfortunately, it is well known that primary T cells are hard‐to‐transfect and conventional non‐viral transfection agents are generally ineffective. Viral transduction and electroporation are more efficient but their use is restricted by high cost, safety issues, and cytotoxicity. Photoporation has recently gained interest as a more gentle alternative physical approach to deliver membrane‐impermeable macromolecules into cells. By attaching gold nanoparticles (AuNPs) to the cell surface followed by pulsed laser illumination, transient membrane pores can be generated that allow the diffusion of macromolecules directly into the cell cytosol. Here, we evaluated this technique for the non‐toxic and effective delivery of small interfering RNA (siRNA) and subsequent silencing of target genes in activated CTLs. We compared photoporation with nucleofection, the current standard physical technique for T cell transfection, and demonstrated a significantly reduced cytotoxicity and higher average dose per cell for the photoporation technique. Graphical abstract Figure. No caption available.

Fast spatial-selective delivery into live cells

ABSTRACT Intracellular delivery of functional compounds into living cells is of great importance for cell biology as well as therapeutic applications. Often it is sufficient that the compound of interest (being a molecule or nanoparticle) is delivered to the cell population as a whole. However, there are applications that would benefit considerably from the possibility of delivering a compound to a certain subpopulation of cells, or even in selected single cells. Here we report on an integrated platform for high‐throughput spatially resolved nanoparticle‐enhanced photoporation (SNAP) of adherent cells. SNAP enables safe, intracellular delivery of exogenously administered nanomaterials in selected subpopulations of cells, even down to the single cell level. We demonstrate the power of SNAP by selectively delivering a safe contrast agent into a subpopulation of polynucleated keratinocytes, enabling their downstream purification for unraveling their role in neoplasm formation. The flexibility and speed with which individual cells can be labeled make SNAP an ideal tool for high‐throughput applications, not only for selective labeling but also for targeted drug delivery. Graphical abstract Figure. No caption available.

Sizing nanomaterials in bio-fluids by cFRAP enables protein aggregation measurements and diagnosis of bio-barrier permeability

Sizing nanomaterials in complex biological fluids, such as blood, remains a great challenge in spite of its importance for a wide range of biomedical applications. In drug delivery, for instance, it is essential that aggregation of protein-based drugs is avoided as it may alter their efficacy or elicit immune responses. Similarly it is of interest to determine which size of molecules can pass through biological barriers in vivo to diagnose pathologies, such as sepsis. Here, we report on continuous fluorescence recovery after photobleaching (cFRAP) as a analytical method enabling size distribution measurements of nanomaterials (1–100 nm) in undiluted biological fluids. We demonstrate that cFRAP allows to measure protein aggregation in human serum and to determine the permeability of intestinal and vascular barriers in vivo. cFRAP is a new analytical technique that paves the way towards exciting new applications that benefit from nanomaterial sizing in bio-fluids.