Microfluidic encapsulation of nanoparticles in alginate microgels gelled via competitive ligand exchange crosslinking.

Efficient delivery of nanometric vectors complexed with nanoparticles at a target tissue without spreading to other tissues is one of the main challenges in gene therapy. One means to overcome this problem is to confine such vectors within microgels that can be placed in a target tissue to be released slowly and locally. Herein, a conventional optical microscope coupled to a common smartphone was employed to monitor the microfluidic production of monodisperse alginate microgels containing nanoparticles as a model for the encapsulation of vectors. Alginate microgels (1.2%) exhibited an average diameter of 125 ± 3 µm, which decreased to 106 ± 5 µm after encapsulating 30 nm fluorescent nanoparticles. The encapsulation efficiency was 70.9 ± 18.9%. In a 0.1 M NaCl solution, 55 ± 5% and 92 ± 4.7% of nanoparticles were released in 30 minutes and 48 hours, respectively. Microgel topography assessment by atomic force microscopy revealed that incorporation of nanoparticles into the alginate matrix changes the scaffold's interfacial morphology and induces crystallization with the appearance of oriented domains. The high encapsulation rate of nanoparticles, alongside their continuous release of nanoparticles over time, makes these microgels and the production unit a valuable system for vector encapsulation for gene therapy research.

Multilamellar-to-Unilamellar Transition Induced by Diphenylalanine in Lipid Vesicles.

In the present work, we investigate the effect of two short phenylalanine-based peptides on lipid membranes. A simplified model membrane composed of lecithin vesicles was used to incorporate different amounts of the two amino acid sequences, the dimmer l,l-diphenylallanine (FF) and the trimmer cysteine-diphenylallanine (CFF). Spectroscopic and scattering techniques were applied to probe in detail the structural behavior of lipid membranes in the presence of the peptides. The experimental results demonstrate that both peptides are located mainly at the interface of the membrane interacting with phosphate groups modifying membrane thickness and flexibility. The multilamellar structure of the vesicles is preserved with inclusion of small amounts of FF, accompanied by changes in membrane thickness and elasticity. Finally, a multi- to unilamellar transition is observed as a result of peptide self-association into a crystalline structure onto the membrane interface.

Shear Alignment of Bola-Amphiphilic Arginine-Coated Peptide Nanotubes.

The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1-1 s-1). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rates, very similar to that observed in the bulk using the Couette geometry. A small isotope effect (comparing H2O/D2O solvents) is noted in the CD spectra indicating increased interpeptide hydrogen bonding in D2O, although this does not influence nanotube self-assembly. These results provide new insights into the controlled alignment of peptide nanotubes for future applications.