The separation and purification of exosomes is essential for the application of exosomes. Previously we have developed a new strategy based on superparamagnetic nanoparticle clusters for the separation of exosomes. Here, to optimize this method for the direct separation of body fluid exosomes using endogenous ligands, we unveiled the influence of free ligands on the formation of clusters and the efficiency of exosome separation. Transferrin was chosen as a model endogenous ligand and the concentration of free serum transferrins was adjusted by different times of serum dialysis. To directly separate most of the exosomes from 1 mL untreated serum, at least 360 μg of labelled ligands needed to be used. However, the required amount of labelled ligands reduced to 10 μg when serum was pre-dialyzed for 24 hours. The results demonstrate that the free ligands can compete with ligands labelled on superparamagnetic nanoparticles to affect the formation of clusters. And to separate exosomes from body fluids sufficiently and directly, the amount of labelled ligands must reach a minimum value (i.e., equivalent to the amount of free ligands). In addition, eliminating free ligands by the mild pre-treatment of body fluids facilitates the separation and purification of body fluid exosomes. This study can improve the universality of current immunoaffinity magnetic particle-based methods for exosome separation and facilitate the in vivo clinical translation of exosomes.

In this study, highly porous and low density silica–gelatin composite aerogels with excellent absorption capacity were obtained. The preparation process was as follows: firstly, the gel with stable network structure was formed by sol–gel method; secondly, after soaking the gel with hexamethyldisilazane solution, the aerogel was prepared by freeze-drying; finally, the aerogel was coated with hexamethyldisilazane via chemical vapor deposition. The composite aerogels with 30% gelatin showed optimal performance in practical applications: lowest bulk density (0.068 g/cm3), highest porosity (96%), largest pore volume (1.24 cm3/g), and maximum oil/organic solvents absorption capacity (12–27 g/g). The excellent oil/solvent absorption capacity and recyclability indicated that the hydrophobic gelatin–silica composite aerogels could be a promising candidate for oil absorption.Open image in new window

Prompt and strong reconnection of severed peripheral nerves is crucial to nerve regeneration. The development of biocompatible nerve adhesives that are stronger than commonly used fibrin glue would be extremely beneficial to this field. We designed an in situ forming nerve adhesive hydrogel composed of chitosan and ε-polylysine (PL), which mimics the polysaccharides/protein structure of natural epineurium matrices, thus, enhancing the compatibility with nerves. Michael-type addition between the maleimide and thiol group was employed as a cross-linking reaction to eliminate foreign damage to nerves and to ensure a fast hydrogel formation speed (curing speed). Gelation occurred within 10 s, quick enough to promptly seal the transected nerve. Catechol groups conjugated onto PL molecules were demonstrated to reinforce both the bulk cohesive force of the hydrogel and the interfacial adhesive force between the hydrogel and epineurium. The storage modulus of the hydrogel was elevated to more than 2400 Pa. A superior nerve adhesion property that can tolerate 0.185 N of force (8× higher than fibrin glue) was obtained. After 8 weeks, the morphology of the repaired nerve fiber coapted by our hydrogel was very close to the morphology of normal nerve, and the axon cross ratio of the regenerated nerves coapted using hydrogel (57%) was much higher than employing the suture technique (35%). Thus, the in situ rapid gelling system offers a promising approach to the repair of severed peripheral nerves.

•An attractive hydrogel adhesive sealant was prepared via Michael addition.•The hydrogel formed rapidly in situ within several seconds.•The hydrogel demonstrated a much higher adhesion strength than commercial fibrin glue.•The hydrogel showed almost no cytotoxicity.•The hydrogel showed excellent prompt hemostatic property.A novel in situ forming polysaccharides/polypeptide hydrogel composed of naturally derived materials for applications as adhesive sealant and hemostatic material was developed via Michael addition crosslinking, taking advantage of its mild condition. Thiol-modified chitosan (CSS) was fast in situ crosslinked by an efficient polypeptide crosslinker (EPLM) which was prepared by introducing maleimide groups onto ε-polylysine. Gelation can happen swiftly within 15–215 s depending on the CSS concentration, the degree of substitution (DS) of maleimide groups, and the molar ratio of maleimide group to thiol group. Results indicated that storage modulus of the hydrogel increased dramatically with the increase of CSS concentration and DS of maleimide. The obtained adhesive hydrogel had an adhesion strength 4 times higher than that of the commercial fibrin glue. Notably, it is non-toxic to L929 cells and exhibits excellent prompt hemostatic property. Polysaccharides/polypeptide structure designed here facilitates to improve both the biocompatibility and the adhesive property.

Polyethylene glycol-maleimide modified ε-polylysine (EPL-PEG-MAL) with a unique comb-shaped structure was designed and used as a novel crosslinker for thiolated chitosan (CSS). Novel polysaccharide/polypeptide bionic hydrogels based on CSS and EPL-PEG-MAL could form rapidly in situ within 1 min via Michael addition under physiological conditions. Rheological studies showed that introduction of PEG can dramatically improve the storage modulus (G′) of the hydrogels and the optimal hydrogel system showed superior G′ of 1,614 Pa. The maximum adhesion strength reached 148 kPa, six times higher than that of fibrin glue. Cytotoxicity test indicated that the hydrogel is nontoxic toward growth of L929 cells. Gelation time, swelling ratio, storage modulus and adhesion strength of the hydrogels can be modulated by the content of PEG-maleimide, CSS concentration and molar ratio of maleimide group to thiol group. Benefiting from the fast gelation behaviors, desirable mechanical properties, relatively high adhesive performance and no cytotoxicity, these hydrogels have the potential applications as promising biomaterials for tissue adhesion and sealing.

Poly(lactic-co-glycolic acid) (PLGA)/gelatin (Gt) ultrafine composite fibers were fabricated via electro-spinning. The effect of gelatin on the morphology and tensile property of the electrospun fiber mats was investigated. Mineralization was carried out in 10×simulated body fluid (10SBF). The deposited calcium phosphate (CaP) was identified by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Results indicated that the average diameter of PLGA/Gt electrospun fibers was much smaller than that of PLGA fibers and the addition of gelatin increased the tenacity of wet mats. Two types of calcium phosphate deposits with different molar ratios of Ca/P were obtained when the electrospun PLGA/Gt mat was incubated in 10SBF. CaP crystals nucleated and grew faster on PLGA/Gt fiber mats rather than on PLGA membranes. “Honeycomb-like” crystals grew on the surface of PLGA/Gt electrospun fibers. After 4 h, the surface of the fibers was entirely coated with these crystals.