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Hyaluronic acid (HA)-based antioxidant hydrogels have achieved remarkable results in diabetic wound repair. However, the realization of their glucose-responsive antioxidant functions remains a significant challenge. In this study, we modified hyaluronic acid methacrylate (HAMA) with phenylboronic acid (PBA) and developed a glucose-responsive HA derivative (HAMA-PBA). A glucose-responsive HAMA-PBA/catechin (HMPC) hydrogel platform was then fabricated by forming a borate ester bond between HAMA-PBA and catechin. The results showed that the HMPC hybrid hydrogel not only had a three-dimensional network structure and Young's modulus similar to those of skin tissue, but also possessed biocompatibility. The HMPC hydrogel also showed unique glucose-responsive catechin release behavior and remarkable antioxidant capability, which could effectively eliminate intracellular reactive oxygen species and protect cells from oxidative stress damage (increased superoxide dismutase activity, stabilized reduced glutathione/oxidized glutathione ratio, and reduced malondialdehyde content). Additionally, in vitro and in vivo experimental results showed that the HMPC hydrogel effectively promoted angiogenesis (enhanced VEGF and CD31 expression) and reduced inflammatory responses (decreased IL-6 level and increased IL-10 level), thus rapidly repairing diabetic wounds (within three weeks). This was a significant improvement as compared to that observed for the untreated control group and the HMP hydrogel group. These results indicated the potential for the application of the HMPC hydrogel for treating diabetic wounds. STATEMENT OF SIGNIFICANCE: At present, the delayed closure rate of diabetic chronic wounds caused by excessive reactive oxygen species (ROS) remains a worldwide challenge. Hyaluronic acid (HA)-based antioxidant hydrogels have made remarkable achievements in diabetic wound repair; however, the realization of their glucose-responsive antioxidant functions is a tough challenge. In this work, we developed a novel HA-based hydrogel platform with glucose-responsive antioxidant activity for rapid repair of diabetic wounds. In vitro and in vivo experimental results showed that the HMPC hydrogel could effectively promote angiogenesis (enhanced VEGF and CD31 expression) and reduce inflammatory response (decreased IL-6 level and increased IL-10 level), thus rapidly repairing diabetic wounds (within 3 weeks). These results indicated the potential of the HMPC hydrogel for application in diabetic wound treatment.

A two-stage mixed integer linear programming model (MILP) incorporating a novel method of stochastic scenario generation was proposed in order to optimize the economic performance of the synergistic combination of midstream and downstream petrochemical supply chain. The uncertainty nature of the problem intrigued the parameter estimation, which was conducted through discretizing the assumed probability distribution of the stochastic parameters. The modeling framework was adapted into a real-world scale of petrochemical enterprise and fed into optimization computations. Comparisons between the deterministic model and stochastic model were discussed, and the influences of the cost components on the overall profit were analyzed. The computational results demonstrated the rationality of using reasonable numbers of scenarios to approximate the stochastic optimization problem.

The detection of autoantibodies is critical for diagnosis of autoimmune diseases. However, the sensitivity is often limited by the properties of the antigens and the detection systems such as enzyme-linked immunosorbent assay (ELISA). Here, employing the multidisplay ability of ferritin, a highly sensitive nanocage-based capture-detection system is designed, of which the sensitivity is 100-1000-fold higher than that of conventional ELISA methods. The capture nanocages are constructed by displaying the primary Sjogren's syndrome (pSS)-related antigenic peptides on ferritin nanocage, which present epitopes effectively and high affinity, leading to tenfold higher capture capability for autoantibodies. Human IgG Fc-binding peptides are also engineered on ferritin nanocage, which enable high binding affinity and efficient horseradish peroxidase (HRP)-labeling. Compared with commercial HRP-conjugated anti-human IgG antibody, the nanocage-based detecting probe exhibited more than tenfold increased sensitivity. Autoantibodies are then examined in 91 sera from patients with pSS, 51 from rheumatoid arthritis, 54 from systemic lupus erythematosus, and 55 from healthy individuals by using the nanocage-based ELISA. The results indicate that the nanocage-based capture-detection system is an effective detection platform and provide a novel and more sensitive method for the diagnosis of autoimmune diseases.

The progress of biomaterials and tissue engineering has led to significant advances in wound healing, but the clinical therapy to regenerate perfect skin remains a great challenge. The implantation of biomaterial scaffolds to heal wounds inevitably leads to a host immune response. Many recent studies revealed that the immune system plays a significant role in both the healing process and the outcome. Immunomodulation or immuno-engineering has thus become a promising approach to develop pro-regenerative scaffolds for perfect skin regeneration. In this paper, we will review recent advancements in immunomodulating biomaterials in the field of skin repair and regeneration, and discuss strategies to modulate the immune response by tailoring the chemical, physical and biological properties of the biomaterials. Understanding the important role of immune responses and manipulating the inherent properties of biomaterials to regulate the immune reaction are approaches to overcome the current bottleneck of skin repair and regeneration.

In order to fabricate nanofiltration (NF) membranes with high flux and anti-fouling properties, polyethylene glycol-functionalized polyhedral oligomeric silsesquioxane (PEG-POSS) nanoparticles were incorporated into the polyamide membrane during the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on polyethersulfone ultrafiltration substrate. The hydrophilicity, surface smoothness and electronegativity of the hybrid membrane were increased compared with the pristine polyamide membrane. The optimal preparation condition determined according to desalination performance was as follows, PEG-POSS content of 0.5% (w/v), PIP and TMC concentration of 0.1% (w/v) and reaction time of 2 min. The PEG-POSS nanoparticles constructed water channels networks and increased free volume of polyamide layer, contributing to the enhanced water permeation of hybrid membrane. The highest pure water flux of 38.7 L m−2 h−1 at 0.2 MPa which was nearly twice that of pristine polyamide membrane was achieved without reducing the salt rejection of Na2SO4 (87.1–91.6%). Meanwhile, the as-fabricated membranes exhibited exceptional anti-fouling performance. The flux recovery ratio (FRR) of the hybrid membrane reached up to 97.0%, 98.4% and 94.5% using bovine serum albumin, humid acid and sodium alginate as model foulants.

Lubrication is the key to efficient function of human tissues and has significant impact on the comfort level. However, the construction of a lubricating nanofibrous membrane has not been reported as yet, especially using a one-step surface modification method. Here, bioinspired by the superlubrication mechanism of articular cartilage, we successfully construct hydration-enhanced lubricating nanofibers via one-step in situ grafting of a copolymer synthesized by dopamine methacrylamide (DMA) and 2-methacryloyloxyethyl phosphorylcholine (MPC) onto electrospun polycaprolactone (PCL) nanofibers. The zwitterionic MPC structure provides the nanofiber surface with hydration lubrication behavior. The coefficient of friction (COF) of the lubricating nanofibrous membrane decreases significantly and is approximately 65% less than that of pure PCL nanofibers, which are easily worn out under friction regardless of hydration. The lubricating nanofibers, however, show favorable wear-resistance performance. Besides, they possess a strong antiadhesion ability of fibroblasts compared with pure PCL nanofibers. The cell density decreases approximately 9-fold, and the cell area decreases approximately 12 times on day 7. Furthermore, the in vivo antitendon adhesion data reveals that the lubricating nanofiber group has a significantly lower adhesion score and a better antitissue adhesion. Altogether, our developed hydration-enhanced lubricating nanofibers show promising applications in the biomedical field such as antiadhesive membranes.

The success of repair or regeneration depends greatly on the architecture of 3D scaffolds that finely mimic natural extracellular matrix to support cell growth and assembly. Polysaccharides have excellent biocompatibility with intrinsic biological cues and they have been extensively investigated as scaffolds for tissue engineering and regenerative medicine (TERM). The physical and biochemical structures of natural polysaccharides, however, can barely meet all the requirements of tissue-engineered scaffolds. To take advantage of their inherent properties, many innovative approaches including chemical, physical, or joint modifications have been employed to improve their properties. Recent advancement in molecular and material building technology facilitates the fabrication of advanced 3D structures with desirable properties. This review focuses on the latest progress of polysaccharide-based scaffolds for TERM, especially those that construct advanced architectures for tissue regeneration.

Trisulfonated poly(arylene thioether phosphine oxide)s (tsPTPO) were synthesized for the first time. Compared with mono-sulfonated poly(arylene thioether phosphine oxide)s (msPTPO), tsPTPO possessed identical polymer backbone but different distribution and content of sulfonic acid side groups. This particular distribution of sulfonic acid side groups was employed to adjust the microstructure of membranes. As a result, tsPTPO showed larger but less connective ionic channels in comparison with the corresponding msPTPO bearing equal ion exchange capacity. Because of this distinct microstructure, tsPTPO achieved much better overall properties than the corresponding msPTPO. The tsPTPO membrane with 100% sulfonation degree showed a swelling and proton conductivity comparable to those of Nafion 117 as well as a methanol permeability of only 0.98×10 −7 cm 2 /s. Moreover, it also displayed high thermal stability, excellent oxidative stability, and superior mechanical properties. Hence, trisulfonation approach was an effective strategy to enhance the properties of poly(arylene thioether phosphine oxide)s based proton exchange membranes.

Current approaches fail at obtaining adequate functional human dermal papilla cells (DPCs) to regenerate hair follicles (HFs). Here we induce human dermal fibroblasts (hDFs) into hDPC-like cells (hDF-DPCs) through alginate-poly-L-lysine-alginate (APA) microencapsulation. Our results show that the derived hDF-DPCs are comparable to primary DPCs on the molecular level, and they can induce the formation of hair follicle-like structures and hair pigmentation in nude mice. RNA-seq analyses indicate the activation of Wnt signaling pathway during the hDF-DPCs conversion. Likewise, we demonstrate that mouse DFs differentiate into mouse DPC-like cells within the hydrogel microcapsules. The induction of dermal fibroblasts into DPC-like cells through biomimetic microencapsulation, devoid of chemical or gene reprogramming, would provide an alternative, abundant, and safe source of DPCs, which would help circumvent the bottleneck in DPC-based HF regeneration.

Ferritin, a widely expressed iron binding protein, has emerged as a promising drug delivery vehicle due to its unique architecture, intrinsic tumor targeting property, and excellent biocompatibility. However, the translation studies of ferritin drug carrier are impeded by the low efficiency and low yield of the drug loading process, which typically employed Urea and pH dependent dis-assembly/reassembly methods. Here, based on crystal structure and protein mutation analyses, we identified a natural drug entry channel existed on the shell of recombinant human H-ferritin (HFn). Moreover, the opening state of this drug entry channel is sensitive to temperature changes. Based on these findings, we develop a simple channel-based drug loading strategy that avoids the denaturation of HFn protein cage with denaturing agents. Loading doxorubicin (Dox) into the HFn protein cage (HFn-Dox) by the channel-based strategy yields significantly higher drug loading efficiency, increased HFn recovery rate, and better stability than that of the denaturation-based methods. Importantly, animal experiments showed that the channel-loaded HFn-Dox had excellent biosafety and significantly improved antitumor activity when compared with the HFn-Dox prepared by the denaturation-based methods. We also found that the drug entry channel appears unique for HFn protein cage and is accessible to multiple small molecule anticancer drugs. Thus, the drug entry channel of HFn protein cage identified in this study provides a novel and highly effective drug loading approach for preparing HFn-drug formulations, which will greatly facilitate the translational study of ferritin drug carriers in cancer-targeting therapies.

Sulfonated poly(arylene thioether phosphine oxide)s (sPTPO) were prepared, which showed high swelling at elevated temperatures. To reduce the swelling, sPTPO were blended with sulfonated polybenzothiazoles (sPBT) to prepare composite proton exchange membranes (PEMs) because the sulfonic acid groups of sPTPO and the benzothiazole moieties of sPBT can form strong acid–base interactions. Herein, sPBT were for the first time employed as a blend component to fabricate blend PEMs. The resulting blend membranes exhibited low swelling and remarkably enhanced overall properties compared to the raw sPTPO membranes. For example, one of them exhibited a swelling of only 30% even at 100 °C, a proton conductivity of 0.085 S cm−1 at 80 °C (higher than that of Nafion 117), and a methanol permeability of 1.02 × 10−7 cm2 s−1. Moreover, it also displayed excellent thermal stability, oxidative stability and mechanical properties. Therefore, sPBT are an ideal blend component to improve the resistance to swelling and the other properties of PEMs.

A superhydrophobic neat graphene aerogel was fabricated for the first time by the facile chemical reduction of a graphene oxide dispersion. The chemical reduction of graphene oxide was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and thermogravimetric analysis (TGA). The resulting graphene aerogel showed complete water repellency, superoleophilicity, ultra-low density, large specific surface area, high absorption capacity of oils and organic solvents, superior absorption recyclability, and excellent mechanical properties. Its absorption capacity was higher than 100 g g−1 for all the utilized common organic solvents. In addition, the fabrication procedure was simple, scalable, and environmental friendly. Thus, it displays promising application prospects in the field of oil-absorption and oil–water separation.

Survival of tissue engineered constructs after implantation depends on proper vascularization. The differentiation of endothelial cells into mature microvasculature requires dynamic interactions between cells, scaffold, and growth factors, which are difficult to recapitulate in artificial systems. Previously, we reported photocrosslinked poly(ethylene glycol) diacrylate (PEGDA) hydrogels displaying collagen mimetic peptides (CMPs), dubbed PEGDA-CMP, that can be further conjugated with bioactive molecules via CMP-CMP triple helix hybridization. Here, we report that a bifunctional peptide featuring pro-angiogenic domain mimicking vascular endothelial growth factor (VEGF), and a collagen mimetic domain that can fold into a triple helix conformation can hybridize with CMP side chains of the PEGDA-CMP hydrogel, which results in presentation of insoluble VEGF-like signals to endothelial cells. Presentation of VEGF-like signals on the surface of micropatterned scaffolds in this way transforms cells from a quiescent state to elongated and aligned phenotype suggesting that this system could be used to engineer organized microvasculature. We also show that the pro-angiogenic peptide, when applied topically in combination with modified dextran/PEGDA hydrogels, can enhance neovascularization of burn wounds in mice demonstrating the potential clinical use of CMP-mediated matrix-bound bioactive molecules for dermal injuries.

Owing to its chemically reactive hydroxyl groups, dextran can be modified with different functional groups to form spherical, tubular and 3D network structures. The development of novel functional scaffolds for efficient controlled release and tissue regeneration has been a major research interest, and offers promising therapeutics for many diseases. Dextran-based scaffolds are naturally biodegradable and can serve as bioactive carriers for many protein biomolecules. The reconstruction of the in vitro microenvironment with proper signaling cues for large-scale tissue regenerative scaffolds has yet to be fully developed, and remains a significant challenge in regenerative medicine. This paper will describe recent advances in dextran-based polymers and scaffolds for controlled release and tissue engineering. Special attention is given to the development of dextran-based hydrogels that are precisely manipulated with desired structural properties and encapsulated with defined angiogenic growth factors for therapeutic neovascularization, as well as their potential for wound repair.

A biodegradable, temperature-sensitive dextran-allyl isocyanate-ethylamine (TSDAIE) as a nonenzymatic cell detachment polymeric substrate for human endothelial progenitor cells (EPCs) is developed and examined. The lower critical solution temperature of TSDAIE is determined; its phase transition occurrs at 18 to 22 °C. For EPC culture, cell culture flasks are coated with TSDAIE and type I collagen. The TSDAIE coating enables EPC detachment when the culture is cooled to 4 °C. The concentration of TSDAIE affects EPC attachment, which is thereby used to optimize the concentration of TSDAIE for coating. At the determined optimal concentration, TSDAIE is found to be compatible for use in EPC culture as revealed by cell attachment, spreading, proliferation, and phenotype. Overall, biodegradable TSDAIE shows promise for applications that culture and expand EPCs including vascular regenerative medicine and tissue engineering.

Supramolecular self-assemblies are predominately driven by noncovalent molecular forces, and electrostatic interactions are the major force for charged molecules. In this paper, we demonstrate the self-assembly of hollow nanospheres from oppositely charged dextran-based hydrophilic macromers. Charged dextran derivatives were obtained by incorporating 2-bromoethylamine (Dex–BH) and chloroacetic acid (Dex–CA) into dextran. In a pH 5.0 buffer solution, Dex–BH and Dex–CA became protonated and deprotonated, respectively, and self-assembled into well-defined nanospheres. Dynamic light scattering (DLS) detected that these nanospheres have a uniform size distribution with a mean diameter of approximately 160 nm, but their size and distribution are largely dependent on molecular weight and pH value. Scanning electron microscopy (SEM) analysis revealed that these nanospheres could form a hollow architecture, which might be attributed to the hydrophilic characteristics of dextran macromers. An in vitro albumin release study indicates that the release rate reflects the nanosphere architecture, and further demonstrates their potential as drug delivery vehicles.

4′-Sulfonate-2,5-dicarboxyphenyl sulfone (SCPS) was synthesized by nucleophilic substitution reaction followed by oxidation reaction. A series of polybenzimidazoles (PBIs) with controlled contents of sulfophenylsulfonyl pendant groups were prepared by polycondensation of SCPS and 2,5-dicarboxyphenyl sulfone with 3,3′-diaminobenzidine. Different from the earlier reports, these soluble PBI with sulfonic acid groups were achieved by attachment of sulfophenylsulfonyl pendant groups. They showed excellent solubility in common organic solvents and thus could be cast into the membrane for fuel cell applications. Moreover, they exhibited high thermal properties as well as oxidative and hydrolytic stability. The sulfoarylated PBI membranes showed low water uptake and swelling, but they exhibited low proton conductivity due to the intermolecular acid–base interaction like sulfonated polybenzimidazoles reported previously. However, they are still interesting matrix materials for proton exchange membranes since their proton conductivity could be improved by the blending or doping method. In addition, the sulfoarylated PBI membranes showed an increasing hydrophilic/hydrophobic nanophase separation morphology with sulfonation degree, leading to the results that their water uptake, swelling, and proton conductivity increased but their oxidative stability decreased with increasing sulfonation degree.

Agents inducing O(6)-methylguanine (O(6)MeG) in DNA such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) are cytotoxic and a deficiency in mismatch repair (MMR) results in lack of sensitivity to this genotoxin (termed alkylation tolerance). Here, we show that ING2, a member of the inhibitor of growth family, is required for cell death induced by MNNG. We further observe that MNNG treatment increases cellular protein levels of ING2 that is dependent on intact MMR function and that MNNG-induced ING2 localizes and associates with p73alpha in the nucleus. Suppression of ING2 by short hairpin RNA (shRNA) in MMR-proficient colorectal cancer cells decreased its sensitivity to MNNG and, in addition, abrogated MNNG-induced stabilization and acetylation of p73alpha. Interestingly, suppression of p73alpha had a greater impact on MNNG-induced cell death than ING2 leading us to conclude that ING2 regulates the cell death response, in part, through p73alpha. Inhibition of c-Abl by STI571 or suppression of c-Abl expression by shRNA blocked ING2 induction and p73alpha acetylation induced by this alkylator. Similarly, suppression of MMR (MLH1) by shRNA abrogated ING2 induction/p73alpha acetylation. Taken together, these results demonstrate that MLH1/c-Abl-dependent activation of ING2p73alpha signaling regulates cell death triggered by MNNG and further suggests that dysregulation of this event may, in part, be responsible for alkylation tolerance observed in MMR compromised cells.

Self-assembly of supramolecular amphiphile consisting of 25,27-bispolyethyleneglycol-calix[4]arene (2mPEG-C[4]A) and phenol palmitate has been studied in a water/dioxane cosolvent. Based on the host-guest interaction of 2mPEG-C[4]A and phenol palmitate, a supramolecular calixarene amphiphile can be readily constructed. Interestingly, by only adjusting the molar ratio of calix[4]arene hosts to benzene derivatives, various morphologies with different size appear. Because of the weak interaction between 2mPEG-C[4]A and phenol palmitate, the formation of these assemblies is dynamic. Such a dynamic behavior can be applied in the controlled release of dyes and drugs.

In this paper, we studied the effects of molecular weight of poly(ethylene glycol diacrylate) (PEGDA) precursor, the degree of substitution (DS) of both allyl isocyanate (AI) and amine groups in dextran-based precursor (Dex-AE), and photoinitiator concentration on Dex-AE/PEGDA hydrogel formation and its ovalbumin (OVA) release. FT-IR spectra showed chemical bond interaction between amine and urethane groups of the hydrogel carriers with OVA. The increase in PEGDA molecular weight led to a faster OVA release because of a more open gel network structure. The study on the DS of AI in Dex-AE precursor showed that an increase in AI did not result in a prominent gel network structure difference. However, the urethane groups in Dex-AE precursor showed some interactions with OVA and, thus, resulted in a slower release rate. The incorporation of amine group into Dex-AE precursor did not affect the gel network structure, but reduced the OVA release rate, and the level of reduction increased with an increasing amine group substitution into the Dex-AE precursor. This reduction could be attributed to the interaction between the amine groups in the gel carrier and OVA. An increase in the photoinitiator concentration showed no effect on the gel network structure or OVA release.

Our prior study has shown that polyethylene glycol (PEG) played a crucial role in improving the properties of the physically crosslinked chitosan-PEG-poly(N-isopropylacrylamide) (PNIPAAm) hydrogels. In this paper, we further investigated the effect of the molecular weight (MW) of PEG on the properties of the chitosan-based physical hydrogels. Fourier Transform Infrared Spectroscopy (FTIR) study showed that the interaction between PEG and other components in the physically crosslinked hydrogels became stronger as the MW of PEG increased. The wide angle X-ray diffraction (WAXD) study indicated that the crystallinity of the physical hydrogels decreased with an increase in the MW of PEG. The thermal study using differential scanning calorimetry (DSC) revealed the crystallizability of the physical hydrogels first reduced with an increase in the MW of PEG, but slightly increased thereafter with a further increase in the MW of PEG. The swelling test showed the water uptake capability of the physical hydrogels increased with an increase in the MW of PEG. The results obtained by scanning electron microscope (SEM) found that the morphological changes of the physical hydrogels with MW of PEG were consistent with the results of swelling and thermal properties; and, contrary to pure PNIPAAm hydrogels which showed a compact and dense network structure at a temperature (37 degrees C) above its LCST, the physical chitosan-PEG-PNIPAAm hydrogels exhibited porous network structure at 37 degrees C instead. The mechanical property of the physical hydrogels was initially increased with an increase in PEG MW, but deteriorated with a further increase in PEG MW. Therefore, the MW of PEG played a key role in controlling the property of the chitosan-based physical hydrogels.

High molecular weight sulfonated poly(arylene thioether phosphine oxide)s (sPATPO) with various sulfonation degrees were prepared directly by aromatic nucleophilic polycondensation of 4,4′-thiobisbenzenethiol with sulfonated bis(4-fluorophenyl) phenyl phosphine oxide and bis(4-fluorophenyl) phenyl phosphine oxide. sPATPO in the acid form with sulfonation degrees of 60–100% exhibits a glass transition temperature higher than 230 °C and a 5% weight loss temperature above 400 °C, indicating high thermal stability. sPATPO with a high sulfonation degree shows high proton conductivity and good resistance to swelling as well. For instance, sPATPO-70 displays the conductivity of 0.0783 S/cm and a swelling ratio of 11.6% at 90 °C. TEM micrographs showed that sPATPO membranes with a high sulfonation degree could form continuous ion channels, which are favorable for improving the proton conductivity but harmful to remaining the mechanical property. The membranes are expected to show good performances in fuel cell applications.

A series of sulfonated poly(phthalazinone ether phosphine oxide)s (sPPEPO) were prepared via aromatic nucleophilic substitution polycondensation of 4-(4-hydroxyphenyl) phthalazinone (HPPZ) with sulfonated bis(4-fluorophenyl)phenyl phosphine oxide (sBFPPO) and bis(4-fluorophenyl)phenyl phosphine oxide (BFPPO) at various ratios. The properties such as molecular weight, ion exchange capacity (IEC), swelling, thermal stability, proton conductivity, and morphology were investigated. sPPEPO with high IEC exhibited high proton conductivity while they still showed low swelling. Typically, sPPEPO with IEC of 1.54 and 1.69 meq/g exhibited high conductivity of 0.091 and 0.19 S/cm, and low swelling ratios of 14.3% and 19.5% at 80 °C, respectively. The low swelling was attributed to the strong intermolecular interaction including the electrostatic force and hydrogen bond. sPPEPO would be promising candidates used as polyelectrolyte membranes for fuel cells.

Poly(ethylene glycol) (PEG) can form either the inclusion complex with α-cyclodextrins (α-CDs) through host–guest interactions or the interpolymer complex with poly(acrylic acid) (PAA) through hydrogen-bonding interaction. Mixing α-CD, PEG, and PAA ternary components in an aqueous solution, the competition between host–guest and hydrogen-bonding interactions occurs. Increasing feed ratio of α-CD:EG:AA from 0:1:1 to 0.2:1:1 (molar ratio), various interesting supramolecular polymer systems, such as hydrogen-bonding complex, dynamic polyrotaxane, crystalline inclusion complex, and thermoresponsive hydrogel, are successively obtained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1114–1120, 2008

Chitosan-based hydrogel films having both temperature and pH sensitivity were prepared by blending chitosan with temperature sensitive poly (N-isopropylacrylamide) (PNIPAAm) and polyethylene glycol (PEG, Mw 2000). PEG was added to enhance film properties, such as thermal, mechanical and swelling properties. Differential scanning calorimetry (DSC) study indicated that the physically blended films exhibited a lower critical solution temperature (LCST) identical to that of pure PNIPAAm (around 32 degrees C). FT-IR data indicated that the temperature sensitivity is due to the PNIPAAm component in the film. The thermal analysis showed that chitosan and PNIPAAm were compatible and the blended films are apt to crystallize. The X-ray diffraction study further showed that the blended films had a higher crystallinity level than chitosan or PNIPAAm alone. The newly formed crystalline domains acted as physical crosslinkers and greatly increased the crosslinking level of the blended films, which, in turn, affected the swelling behavior and mechanical property of the blended films. Scanning electron microscopy (SEM) revealed that the blended swollen films exhibited a more porous structure at 37 degrees C (LCST) than at room temperature (LCST), though their swelling ratios were reduced as temperature increased from room temperature to 37 degrees C because of the dehydration nature of PNIPAAm at temperatures above its LCST. The results demonstrated that physically blended temperature sensitive films could be formulated, which are capable of producing more pores upon heating. The blended films were also found to be pH sensitive due to the fact that chitosan, one of the film components, has many pendant amino groups.

Adipogenesis is essential for soft tissue reconstruction following trauma or tumor resection. We demonstrate that CD31−/34+/146− cells, a subpopulation of the stromal vascular fraction (SVF) of human adipose tissue, were robustly adipogenic. Insulin growth factor-1 (IGF1) promoted a lineage bias towards CD31−/34+/146− cells at the expense of CD31−/34+/146+ cells. IGF1 was microencapsulated in poly(lactic-co-glycolic acid) scaffolds and implanted in the inguinal fat pad of C57Bl6 mice. Control-released IGF1 induced remarkable adipogenesis in vivo by recruiting endogenous cells. In comparison with the CD31−/34+/146+ cells, CD31−/34+/146− cells had a weaker Wnt/β-catenin signal. IGF1 attenuated Wnt/β-catenin signaling by activating Axin2/PPARγ pathways in SVF cells, suggesting IGF1 promotes CD31−/34+/146− bias through tuning Wnt signal. PPARγ response element (PPRE) in Axin2 promoter was crucial for Axin2 upregulation, suggesting that PPARγ transcriptionally activates Axin2. Together, these findings illustrate an Axin2/PPARγ axis in adipogenesis that is particularly attributable to a lineage bias towards CD31−/34+/146− cells, with implications in adipose regeneration. Stem Cells 2015;33:2483–2495

Based on dextran–allyl isocyanate–ethylamine (Dex-AE) and polyethylene glycol–diacrylate (PEGDA), a pH sensitive biodegradable hydrogel with improved protein release was prepared through UV photo-crosslinking. The Dex-AE precursor was prepared through a two-step chemical modification and characterized by FT-IR and 1H NMR. The effects of reaction conditions on the synthesis of Dex-AE were studied. The interior morphology data by scanning electron microscopy (SEM) revealed that an increase in Dex-AE content led to an initial decrease in pore size of the microstructure of the Dex-AE/PEGDA hydrogels, but a further increase in Dex-AE content resulted in a relatively looser network structure. The swelling data indicated that the swelling ratio depended on the precursor feed ratio and was correlated to the morphology of the microporous network structure. The pH sensitive property of the Dex-AE/PEGDA hydrogels was studied in different pH buffer solutions and was found that these hydrogels were pH sensitive due to the presence of ample pendant amino groups. The ionic strength data demonstrated that the Dex-AE/PEGDA hydrogels exhibit the highest swelling ratio in pure water, but the swelling ratio became lower as the ionic strength of the media increased. The in vitro albumin release from these hydrogels was examined in different pH (3.0, 7.4) buffer solutions. Both the protein loading and release data indicated that the Dex-AE/PEGDA hydrogels had more protein loading and sustained release capability than pure PEGDA hydrogel, and this ability increased as the Dex-AE composition increased; the Dex-AE/PEGDA hydrogel also showed a faster BSA release in a lower pH than a higher pH medium.

Sulfonated poly(phthalazinone ether ketone ketone)s (sPPEKK) and sulfonated poly(arylene ether ketone ketone sulfone)s (sPAEKK) were successfully synthesized by direct polycondensation. The water uptake and swelling of sPPEKK are much less compared with those of sPAEKK, especially in high temperature, which result from the powerful intermolecular hydrogen bonds of sPAEKK, confirmed by variable temperature IR spectra. The maximum operation temperature of proton exchange membranes made of sPPEKK is higher than 80 °C, improving the property of resistance to swelling.

The development of a new temperature sensitive hydrogel particle having biodegradable crosslinkages, composed of poly(N-isopropylacrylamide)/dextran-allyl isocyanate (PNIPAAm/Dex-AI) was prepared through precipitation polymerization. Dex-AI was used as a precursor as well as a biodegradable crosslinker for forming the network particles. Characterization data showed that these PNIPAAm/Dex-AI hydrogel particles had an average hydration diameter around 1.0 mm and showed a dendrite-like heterogeneous morphology with two different porous microstructures. The hydrogel particles exhibited a transition temperature or lower critical solution temperature (LCST) at around 25.7 °C through differential scanning calorimetry (DSC) measurement or temperature dependence study of particles volume. The freeze-dried particles swelled quickly when socked in distilled water at room temperature and large amounts of water were stored within the network before reaching the stable swollen state.

A partially biodegradable and thermosensitive hybrid hydrogel network (DAN series) based on dextran-allylisocyanate (Dex-AI) and poly(N-isopropylacrylamide) (PNIPAAm) was synthesized via UV photocrosslinking. These hybrid hydrogels were characterized in terms of their chemical structure, thermal, mechanical, morphological and temperature-induced swelling properties. The effect of the composition ratio of Dex-AI to PNIPAAm on such properties were examined. The differential scanning calorimetry data show that this Dex-AI/PNIPAAm hybrid network has an increased lower critical solution temperature (LCST) and glass transition temperature (Tg) with an increase in the Dex-AI content. The interior morphology of these hybrid hydrogels revealed a decreased porous microstructure with an increase in the Dex-AI content in the hybrid network. Furthermore, if the Dex-AI composition became too high, a distinctive network structure with two different microporous structures appeared. The mechanical properties of these hybrid hydrogels also increased with an increase in the Dex-AI content. The temperature dependence of the swelling ratio, the deswelling kinetics as well as the reswelling kinetics was also characterized by gravimetric method. When comparing with a normal PNIPAAm hydrogel, these Dex-AI/PNIPAAm hybrid networks, due to the presence of Dex-AI moiety, also show improved temperature-induced intelligent properties, such as the faster and controllable response dynamics, which may find promising applications in a wide variety of fields, such as biomedical and bioengineering fields.