An influenza virus-inspired polymer system for the timed release of siRNA

Small interfering RNA silences specific genes by interfering with mRNA translation, and acts to modulate or inhibit specific biological pathways; a therapy that holds great promise in the cure of many diseases. However, the naked small interfering RNA is susceptible to degradation by plasma and tissue nucleases and due to its negative charge unable to cross the cell membrane. Here we report a new polymer carrier designed to mimic the influenza virus escape mechanism from the endosome, followed by a timed release of the small interfering RNA in the cytosol through a self-catalyzed polymer degradation process. Our polymer changes to a negatively charged and non-toxic polymer after the release of small interfering RNA, presenting potential for multiple repeat doses and long-term treatment of diseases

Controlled Release of Doxorubicin Loaded within Magnetic Thermo-responsive Nanocarriers under Magnetic and Thermal Actuation in a Microfluidic Channel

We report a procedure to grow thermo-responsive polymer shells at the surface of magnetic nanocarriers made of multiple iron oxide superparamagnetic nanoparticles embedded in poly(maleic anhydride-alt-1-ocatadecene) polymer nanobeads. Depending on the comonomers and on their relative composition, tunable phase transition temperatures in the range between 26 and 47 °C under physiological conditions could be achieved. Using a suitable microfluidic platform combining magnetic nanostructures and channels mimicking capillaries of the circulatory system, we demonstrate that thermo-responsive nanobeads are suitable for localized drug delivery with combined thermal and magnetic activation. Below the critical temperature nanobeads are stable in suspension, retain their cargo, and cannot be easily trapped by magnetic fields. Increasing the temperature above the critical temperature causes the aggregation of nanobeads, forming clusters with a magnetic moment high enough to permit their capture by suitable magnetic g..

Synthesis and characterization of chitosan-g-poly(ethylene glycol)-folate as non viral carrier for tumor-targeted gene delivery

Poor water solubility and low transfection efficiency of chitosan are major drawbacks for its use as a gene delivery carrier. PEGylation can increase its solubility, and folate conjugation may improve gene transfection efficiency due to promoted uptake of folate receptorbearing tumor cells. The aim of this study was to synthesize and characterize folate-poly(ethylene glycol)-grafted chitosan (FA-PEG-Chi) for targeted plasmid DNA delivery to tumor cells. Gel electrophoresis study showed strong DNA binding ability of modified chitosan. The pH(50) values, defined as the pH when the transmittance of a polymer solution at 600nm has reached 50% of the original value, suggested that the water solubility of PEGylated chitosan had improved significantly. Regression analysis of pH50 value as a function of substitution degree of PEG yielded an almost linear correlation for PEG-Chi and FA-PEG-Chi. The solubility of PEGylated chitosan decreased slightly by further conjugation of folic acid due to the relatively more hydrophobic nature of folic acid when compared to PEG. In addition, the chitosan-based DNA complexes did not induce remarkable cytotoxicity against HEK 293 cells. FA-PEG-Chi can be a promising gene carrier due to its solubility in physiological pH, efficiency in condensing DNA, low cytotoxicity and targeting ability

Injectable biodegradable hydrogels with tunable mechanical properties for the stimulation of neurogenesic differentiation of human mesenchymal stem cells in 3D culture

We report an injectable hydrogel scaffold system with tunable stiffness for controlling the proliferation rate and differentiation of human mesenchymal stem cells (hMSCs) in a three-dimensional (3D) context in normal growth media. The hydrogels composed of gelatin-hydroxyphenylpropionic acid (Gtn-HPA) conjugate were formed using the oxidative coupling of HPA moieties catalyzed by hydrogen peroxide (H2O2) and horseradish peroxidase (HRP). The stiffness of the hydrogels was readily tuned by varying the H2O2 concentration without changing the concentration of polymer precursor. We found that the hydrogel stiffness strongly affected the cell proliferation rates. The rate of hMSC proliferation increased with the decrease in the stiffness of the hydrogel. Also, the neurogenesis of hMSCs was controlled by the hydrogel stiffness in a 3D context without the use of any additional biochemical signal. These cells which were cultured in hydrogels with lower stiffness for 3 weeks expressed much more neuronal protein markers compared to those cultured within stiffer hydrogels for the same period of time

The role of stiffness of gelatinehydroxyphenylpropionic acid hydrogels formed by enzyme-mediated crosslinking on the differentiation of human mesenchymal stem cell

We report the stimulation of neurogenesis and myogenesis of human mesenchymal stem cells (hMSCs) on the surfaces of biodegradable hydrogels with different stiffness. The hydrogels were composed of gelatin-hydroxyphenylpropionic acid (Gtn-HPA) conjugate were formed using the oxidative coupling of phenol moieties catalyzed by hydrogen peroxide (H(2)O(2)) and horseradish peroxidase (HRP). The storage modulus of the hydrogels was readily tuned from 600 to 12800 Pa. It was found that the stiffness of the hydrogel strongly affected the cell attachment, focal adhesion, migration and proliferation rate of hMSCs. The hMSCs on stiffer surfaces have a larger spreading area, more organized cytoskeletons, more stable focal adhesion, faster migration and a higher proliferation rate. The gene expression related to the extracellular matrix and adhesion molecules also differed when the cells were cultured on hydrogels with different stiffness. The differentiation of hMSCs on the surface of the hydrogel was closely linked to the hydrogel stiffness. The cells on a softer hydrogel (600 Pa) expressed more neurogenic protein markers, while cells on a stiffer hydrogel (12000 Pa) showed a higher up-regulation of myogenic protein marker

Modulation of chondrocyte functions and stiffness-dependent cartilage repair using an injectable enzymatically crosslinked hydrogelwith tunable mechanical properties

10.1016/j.biomaterials.2013.11.070Biomaterials3572207-2217BIMA

Extension of Polyphenolics by CWPO-C Peroxidase Mutant Containing Radical-Robust Surface Active Site

Expressed as insoluble forms in Escherichia coli, native cationic cell wall peroxidase (CWPO-C) from the poplar tree and mutant variants were successfully reactivated via refolding experiments and used to elucidate the previously presumed existence of an electron transfer (ET) pathway in the CWPO-C structure. Their catalytic properties were fully characterized through various analyses including steady-state kinetic, direct oxidation of lignin macromolecules and their respective stabilities during the polymerization reactions. The analysis results proved that the 74th residue on the CWPO-C surface plays an important role in catalyzing the macromolecules via supposed ETmechanism. By comparing the residual activities of wild-type CWPO-C and mutant 74W CWPO-C after 3 min, mutation of tyrosine 74 residue to tryptophan increased the radical resistance of peroxidase up to ten times dramatically while maintaining its capability to oxidize lignin macromolecules. Furthermore, extension of poly(catechin) as well as lignin macromolecules with CWPO-C Y74W mutant clearly showed that this radical-resistant peroxidase mutant can increase the molecular weight of various kinds of polyphenolics by using surface-located active site. The anti-oxidation activity of the synthesized poly(catechin) was confirmed by xanthine oxidase assay. The elucidation of a uniquely catalytic mechanism in CWPO-C may improve the applicability of the peroxidase/H2O2 catalyst to green polymer chemistryope