Boguang Yang

A thermoresponsive poly(N-vinylcaprolactam-co-sulfobetaine methacrylate) zwitterionic hydrogel exhibiting switchable anti-biofouling and cytocompatibility

Non-specific protein adsorption adversely affects the application of thermoresponsive polymers in the biomedical field. To overcome this disadvantage, thermoresponsive N-vinylcaprolactam (VCL) and anti-biofouling zwitterionic sulfobetaine methacrylate (SBMA) monomers with various VCL/SBMA ratios were used for the synthesis of poly(VCL-co-SBMA) (P(VCL-co-SBMA)) copolymers via free radical solution polymerization. The P(VCL-co-SBMA) copolymers exhibited both a lower critical solution temperature (LCST) and an upper critical solution temperature (UCST) in aqueous solutions. Furthermore, both the UCST and LCST of the copolymer shift to higher temperatures with the increase of PSBMA segments, and they shift to lower temperatures with the increase of salt concentrations in the solution. Based on these results, P(VCL-co-SBMA) hydrogels were prepared using N,N′-methylenebisacrylamide (MBAA) as the crosslinker. Compared with the PVCL hydrogel, the P(VCL-co-SBMA) hydrogels exhibit better mechanical properties. Notably, the P(VCL-co-SBMA) hydrogel retained the temperature sensitivity of PVCL, and it could be modulated by varying the PVCL/PSBMA segment ratios. In addition, all the hydrogels exhibit good cytocompatibility. More importantly, the protein adsorption and cell adhesion of the hydrogel can be controlled by temperature. The non-specific protein adsorption was effectively suppressed at physiological temperatures. The switchable anti-biofouling nature of P(VCL-co-SBMA) hydrogel together with their temperature sensitivity can be potentially used in drug, cell or enzyme delivery.

Physical Cross-Linking Starch-Based Zwitterionic Hydrogel Exhibiting Excellent Biocompatibility, Protein Resistance, and Biodegradability

In this work, a novel starch-based zwitterionic copolymer, starch-graft-poly(sulfobetaine methacrylate) (ST-g-PSBMA), was synthesized via Atom Transfer Radical Polymerization. Starch, which formed the main chain, can be degraded completely in vivo, and the pendent segments of PSBMA endowed the copolymer with excellent protein resistance properties. This ST-g-PSBMA copolymer could self-assemble into a physical hydrogel in normal saline, and studies of the formation mechanism indicated that the generation of the physical hydrogel was driven by electrostatic interactions between PSBMA segments. The obtained hydrogels were subjected to detailed analysis by scanning electron microscopy, swelling ratio, protein resistance, and rheology tests. Toxicity and hemolysis analysis demonstrated that the ST-g-PSBMA hydrogels possess excellent biocompatibility and hemocompatibility. Moreover, the cytokine secretion assays (IL-6, TNF-α, and NO) confirmed that ST-g-PSBMA hydrogels had low potential to trigger the activation of macrophages and were suitable for in vivo biomedical applications. On the basis of these in vitro results, the ST-g-PSBMA hydrogels were implanted in SD rats. The tissue responses to hydrogel implantation and the hydrogel degradation in vivo were determined by histological analysis (Hematoxylin and eosin, Van Gieson, and Massons Trichrome stains). The results presented in this study demonstrate that the physical cross-linking, starch-based zwitterionic hydrogels possess excellent protein resistance, low macrophage-activation properties, and good biocompatibility, and they are a promising candidate for an in vivo biomedical application platform.

Iota-carrageenan/chitosan/gelatin scaffold for the osteogenic differentiation of adipose-derived MSCs in vitro.

In this study, we have developed ι-carrageenan/chitosan/gelatin (CCG) scaffold containing multiple functional groups (-NH2 , -OH, -COOH, and -SO3 H) to resemble the native extracellular matrix (ECM), using the ion-shielding technology and ultrasonic dispersion method. Fourier transform infrared spectroscopy (FTIR) of the CCG scaffolds suggests that the formation of CCG network involves electrostatic interactions between ι-carrageenan (ι-CA) and chitosan/gelatin, and the covalent cross-linking among amino groups of chitosan and/or gelatin. Scanning electron microscopic (SEM) observation reveals that the porous structure of scaffolds can be modulated by the ratio of ι-CA to chitosan/gelatin. The swelling ratio of the hydrogels increases as the ι-CA contents increase. Using differential scanning calorimetry, we found that the double helix structure of ι-CA is only stabilized at low contents of ι-CA in the CCG scaffolds (e.g., 5 wt %). The scaffolds containing 5% ι-CA showed the best protein adsorption capacity (4.46 ± 0.63 μg protein/mg scaffold) and elastic modulus (5.37 ± 1.03 MPa). In addition, the CCG scaffolds exhibit excellent support for adipose-derived mesenchymal stem cells (ADMSCs) attachment and proliferation, and they can improve the osteogenic differentiation and neovascularization capacities of ADMSCs. Overall, we conclude that the CCG may represent an ideal scaffold material for bone tissue engineering.

Development of Electrically Conductive Double-Network Hydrogels via One-Step Facile Strategy for Cardiac Tissue Engineering.

Cardiac tissue engineering is an effective method to treat the myocardial infarction. However, the lack of electrical conductivity of biomaterials limits their applications. In this work, a homogeneous electronically conductive double network (HEDN) hydrogel via one-step facile strategy is developed, consisting of a rigid/hydrophobic/conductive network of chemical crosslinked poly(thiophene-3-acetic acid) (PTAA) and a flexible/hydrophilic/biocompatible network of photo-crosslinking methacrylated aminated gelatin (MAAG). Results suggest that the swelling, mechanical, and conductive properties of HEDN hydrogel can be modulated via adjusting the ratio of PTAA network to MAAG network. HEDN hydrogel has Youngs moduli ranging from 22.7 to 493.1 kPa, and its conductivity (≈10(-4) S cm(-1)) falls in the range of reported conductivities for native myocardium tissue. To assess their biological activity, the brown adipose-derived stem cells (BADSCs) are seeded on the surface of HEDN hydrogel with or without electrical stimulation. Our data show that the HEDN hydrogel can support the survival and proliferation of BADSCs, and that it can improve the cardiac differentiation efficiency of BADSCs and upregulate the expression of connexin 43. Moreover, electrical stimulation can further improve this effect. Overall, it is concluded that the HEDN hydrogel may represent an ideal scaffold for cardiac tissue engineering.

Injectable Fullerenol/Alginate Hydrogel for Suppression of Oxidative Stress Damage in Brown Adipose-Derived Stem Cells and Cardiac Repair

Stem cell implantation strategy has exhibited potential to treat the myocardial infarction (MI), however, the low retention and survival limit their applications due to the reactive oxygen species (ROS) microenvironment after MI. In this study, the fullerenol nanoparticles are introduced into alginate hydrogel to create an injectable cell delivery vehicle with antioxidant activity. Results suggest that the prepared hydrogels exhibit excellent injectable and mechanical strength. In addition, the fullerenol/alginate hydrogel can effectively scavenge the superoxide anion and hydroxyl radicals. Based on these results, the biological behaviors of brown adipose-derived stem cells (BADSCs) seeded in fullerenol/alginate hydrogel were investigated in the presence of H2O2. Results suggest that the fullerenol/alginate hydrogels have no cytotoxicity effects on BADSCs. Moreover, they can suppress the oxidative stress damage of BADSCs and improve their survival capacity under ROS microenvironment via activating the ERK and p38 pathways while inhibiting JNK pathway. Further, the addition of fullerenol can improve the cardiomyogenic differentiation of BADSCs even under ROS microenvironment. To assess its therapeutic effects in vivo, the fullerenol/alginate hydrogel loaded with BADSCs were implanted in the MI area in rats. Results suggest that the fullerenol/alginate hydrogel can effectively decrease ROS level in MI zone, improve the retention and survival of implanted BADSCs, and induce angiogenesis, which in turn promote cardiac functional recovery. Therefore, the fullerenol/alginate hydrogel can act as injectable cell delivery vehicles for cardiac repair.

Engineering pectin-based hollow nanocapsules for delivery of anticancer drug

Multifunctional capsules have great applications in biomedical fields. In this study, novel polysaccharide-based nanocapsules were prepared via a layer-by-layer technique using silica as the templates. The shell was constructed based on the electrostatic interactions between pectin and chitosan. The pectin-chitosan nanocapsules ((Pec/Cs)3Pec) could keep good colloidal stability within 96h in PBS solution and 48h in BSA solution. Meanwhile, the nanocapsules exhibited a high drug loading and pH-sensitive release property for doxorubicin hydrochloride. Moreover, (Pec/Cs)3Pec nanocapsules had no cytotoxicity to both human hepatocellular carcinoma cells (HepG2 cells) and mouse fibroblast cells (L929 cells). More importantly, (Pec/Cs)3Pec nanocapsules could be more easily uptaken by HepG2 cells when compared with L929 cells. In vitro anticancer activity tests indicated the carriers could effectively kill HepG2 cells. Overall, (Pec/Cs)3Pec nanocapsules have great potential as a novel anticancer drug carrier as a result of their pH-sensitivity, good colloidal stability and anticancer activity.

Stable and pH-responsive polyamidoamine based unimolecular micelles capped with a zwitterionic polymer shell for anticancer drug delivery

To improve the circulation stability of polyamidoamine (PAMAM) based drug delivery systems in complex biological microenvironments, a series of generation-3.0 PAMAM-graft-poly[3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PAMAM3.0-g-PDMAPS) copolymers are synthesized via atom transfer radical polymerization. The zwitterionic PDMAPS segments serve as a shell to stabilize the unimolecular micelles, whereas the PAMAM3.0 dendrimers constitute a hydrophobic core. The sizes of the PAMAM3.0-g-PDMAPS unimolecular micelles range from 6.5 to 8.5 nm. Furthermore, PAMAM3.0-g-PDMAPS can keep the micelle-like structure when it is diluted by large volumes of fluids. More importantly, the PDMAPS shell layer can suppress non-specific protein adsorption on the surface of the micelles. The excellent stability to dilution and anti-biofouling are beneficial for prolonged circulation time in a complex biological microenvironment. In addition, anticancer doxorubicin (DOX) can be encapsulated both in the PAMAM3.0 core via hydrophobic interactions and the PDMAPS shell layer via hydrogen bonds. Drug release studies confirm the pH-responsive nature of PMAMA3.0-g-PDMAPS micelles by achieving 65.23% DOX release at pH 5.1 as compared to 16.38% at pH 7.4. Based on these results, the cytotoxicity and anticancer effects against human hepatocellular carcinoma cells (HepG2) of the PAMAM3.0-g-PDMAPS system loaded with DOX are investigated. The results suggest that the PDMAPS shell layer can significantly decrease the cytotoxicity via decreasing/shielding of the positive charges on the PAMAM dendrimers. After internalization by HepG2 cells, DOX is released from the micelles to the nucleus and further inhibits the proliferation of HepG2. Therefore, these PAMAM3.0-g-PDMAPS unimolecular micelles are a potential platform for anticancer drug delivery.

Fullerene mediates proliferation and cardiomyogenic differentiation of adipose-derived stem cells via modulation of MAPK pathway and cardiac protein expression

Zero-dimensional fullerenes can modulate the biological behavior of a variety of cell lines. However, the effects and molecular mechanisms of proliferation and cardiomyogenic differentiation in brown adipose-derived stem cells (BADSCs) are still unclear. In this study, we report the initial biological effects of fullerene-C60 on BADSCs at different concentrations. Results suggest that fullerene-C60 has no cytotoxic effects on BADSCs even at a concentration of 100 μg/mL. Fullerene-C60 improves the MAPK expression level and stem cell survival, proliferation, and cardiomyogenesis. Further, we found that the fullerene-C60 modulates cardiomyogenic differentiation. Fullerene-C60 improves the expression of cardiomyocyte-specific proteins (cTnT and α-sarcomeric actinin). At elevated concentration, fullerene-C60 reduces the incidence of diminished spontaneous cardiac differentiation of BADSCs with time. At the genetic level, fullerene-C60 (5 μg/mL) also improves the expression of cTnT. In addition, fullerene-C60 promotes the formation of gap junction among cells. These findings have important implications for clinical application of fullerenes in the treatment of myocardial infarction.