Nanostructures of colloidal complexes formed in oppositely charged polyelectrolyte/surfactant dilute aqueous solutions

Small-angle neutron scattering measurements were performed on dilute solutions of carboxymethylcellulose/DTAB complexes in water in order to determine their size, shape and internal structures. At low polymer content, the complexes are spherical, rather monodisperse and probably made of polymer chains intercalated between surfactant micelles. Moreover, we show that these micelles have a similar cubic arrangement than found in polymer/surfactant precipitates formed at higher surfactant concentrations. At larger polymer content, in the semi-dilute polyelectrolyte regime, the complexes are larger, softer and polydisperse. However, they possess a similar internal structure in both regimes. Carboxymethylcellulose/CTAB complexes are also large, soft and polydisperse but do not seem to exhibit well-defined internal structures.     

AC electrokinetic isolation and detection of extracellular vesicles from dental pulp stem cells: Theoretical simulation incorporating fluid mechanics

Extracellular vesicles (EVs) are cell-derived nanoscale vesicles involved in intracellular communication and the transportation of biomarkers. EVs released by mesenchymal stem cells have been recently reported to play a role in cell-free therapy of many diseases. However, the demand for better research tools to replace the tedious conventional methods used to study EVs is getting stronger. EVs' manipulation using alternating current (AC) electrokinetic forces in a microfluidic device has appeared to be a reliable and sensitive diagnosis and trapping technique. Given that different AC electrokinetic forces may contribute to the overall motion of particles and fluids in a microfluidic device, EVs' electrokinetic trapping must be examined considering all dominant forces involved depending on the experimental conditions. In this paper, AC electrokinetic trapping of EVs using an interdigitated electrode arrays is investigated. A 2D numerical simulation incorporating the two significant AC electrokinetic phenomena (Dielectrophoresis and AC electroosmosis) has been performed. Theoretical predictions are then compared with experimental results and allow for a plausible explanation of observations inconsistent with DEP theory. It is demonstrated that the inconsistencies can be attributed to a significant extent to the contribution of the AC electroosmotic effect.     

Biodegradable Polypeptide-based Vesicles with Intrinsic Blue Fluorescence for Antibacterial Visualization

Fluorescence imaging has been an indispensable tool to provide dynamic information about the localization and quantity of organisms.Meanwhile,due to the intrinsic hollow structure and modularized biofunctionalities,polymer vesicles have been widely applied in biomedical field.However,most polymer vesicles are embedded with organic fluorophores for fluorescence imaging,which have certain drawbacks such as leakage and possible cytotoxicity.Here,we present a biodegradable polypeptide-based vesicle with intrinsic blue fluorescence without introducing any fluorophore for real-time visualization of antibacterial process.Through modular design to integrate multiple functional fragments,poly(ε-caprolactone)-block-poly(tryptophan)-block-poly(lysine-stat-phenylalanine)[PCL25-b-PTrP2-b-P(Lys13-stat-Phe4)]was synthesized,where PCL chains form the hydrophobic membrane,P(Lys-stat-Phe) and PTrp provide intrinsic fluorescence and broad-spectrum antibacterial activity.It is noteworthy that the fluorescence emission was shifted from invisible ultraviolet range of amino acids to visible range (emission maximum at 436 nm),which makes it possible to visualize the antibacterial process.In addition,through utilizing the intrinsic fluorescence of vesicles,confocal fluorescent imaging of vesicles with bacteria validated the specific adhesion of vesicle towards bacteria,and the bacterial death through membrane disruption.Overall,we provided a novel approach to developing biodegradable fluorescent polypeptide-based vesicles for real-time visualization of antibacterial process.     

Self-assembly vesicles made from a cyclodextrin supramolecular complex

Self-assembly vesicles have been made from a cyclodextrin (CD) supramolecular complex, which is cooperatively formed with natural beta-CD, 1-naphthylammonium chloride (NA), and sodium bis(2-ethyl-1-hexyl)sulfosuccinate (AOT) by weak noncovalent interactions. In the complex structure, a NA molecule is included inside a beta-CD molecule while it is coupled with an AOT molecule on one side. The supramolecular structure and morphology of the vesicles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The mechanism of vesicle formation and transition is discussed along with the data obtained from induced circular dichroism (ICD) and UV/visible spectroscopy, polarized optical microscopy (POM), and (1)H NMR spectroscopy. Both the fabrication and the transition of vesicles are controlled by the inclusion equilibria and the cooperative binding of noncovalent interactions, which include the "key-lock" principle, electrostatic interactions, pi-pi stacking, and amphiphilic hydrophobic association.     

Self-assembling viral mimetics: one long journey with short steps

Recently, the Foresight Institute has pronounced six economic challenges that can be addressed through the progress of nanotechnology. One of these is the health and longevity of human life. Amongst applications anticipated to provide a solution to this challenge, gene therapy appears to be particularly promising. In theory, many diseases that result from genetic disorders can be cured by correcting defective genes. In practice, finding efficient and safe delivery vectors remains the stumbling point on the path of genetic therapies to the clinic. Viruses, otherwise the most efficient transfectors, pose safety concerns over immune reactions, whereas synthetic gene packages greatly lack the structural integrity of viruses. An ideal vector is therefore seen as a compromise between the two: a nanoscale device, which would mimic a virus and act as a virus, but would do this at the designer's whim. A strategy to achieve this is offered by the virus architecture itself, the principles of which are translated into the function via exquisitely reproducible self-assembly mechanisms. Thus, to mimic a virus is to mimic the way it is built, i.e., self-assembly. With just a few attempts made so far, the journey to an artificial virus has had a short lifetime, but the promise it holds is not expected to reduce any time soon.