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Cell-based therapies hold significant advantages in comparison with the traditional drug-based or injection-based treatments. However, for long-term functional cellular implants, immune acceptance must be established. To accomplish the acceptance of the implanted cells, various biomaterial systems have been studied. Nanogels have shown great potential for modulation of cellular microenvironments, acting as a physical barrier between the immune system and the implant. However, internalization of nano-scale materials by implanted cells is not desirable and is yet to be overcome. In this study, we incorporated acrylate modified cholesterol-bearing pullulan (CHPOA) nanogels into poly (ethylene glycol) diacrylate (PEGDA) hydrogels through covalent crosslinking, where we used visible light-induced photopolymerization. We characterized morphology and swelling properties of CHPOA incorporated PEG composite hydrogels using FE-SEM and gravimetric analysis. Also, we investigated the biocompatibility properties of composite hydrogels in vivo, where we used both healthy and diabetic mice. We induced diabetes in mice using a low dose streptozotocin (STZ) injections and implanted composite hydrogels in both diabetic and healthy mice through subcutaneous route. Immune cell infiltration of the retrieved tissue was examined through histological analysis, where we observed minimum immune response levels of 0–2 rareness, according to ISO standard of biological evaluation of medical devices. Our observation suggests that the composite hydrogel developed here can be used to introduce nanostructured domains into bulk hydrogels and that this system has potential to be used as immunologically acceptable composite material in cellular therapy without internalization of nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] Immunization is a straightforward concept but remains for some pathogens like HIV-1 a challenge. Thus, new approaches towards increasing the efficacy of vaccines are required to turn the tide. There is increasing evidence that antigen exposure over several days to weeks induces a much stronger and more sustained immune response compared to traditional bolus injection, which usually leads to antigen elimination from the body within a couple of days. Therefore, we developed a poly(ethylene) glycol (PEG) hydrogel platform to investigate the principal feasibility of a sustained release of antigens to mimic natural infection kinetics. Eight-and four-armed PEG macromonomers of different MWs (10, 20, and 40 kDa) were end-group functionalized to allow for hydrogel formation via covalent cross-linking. An HIV-1 envelope (Env) antigen in its trimeric (Env tri) or monomeric (Env mono) form was applied. The soluble Env antigen was compared to a formulation of Env attached to silica nanoparticles (Env-SiNPs). The latter are known to have a higher immunogenicity compared to their soluble counterparts. Hydrogels were tunable regarding the rheological behavior allowing for different degradation times and release timeframes of Env-SiNPs over two to up to 50 days. Affinity measurements of the VCR01 antibody which specifically recognizes the CD4 binding site of Env, revealed that neither the integrity nor the functionality of Env mono -SiNPs (K d = 2.1 ± 0.9 nM) and Env tri -SiNPs (K d = 1.5 ± 1.3 nM), respectively, were impaired after release from the hydrogel (K d before release: 2.1 ± 0.1 and 7.8 ± 5.3 nM, respectively). Finally, soluble Env and Env-SiNPs which are two physico-chemically distinct compounds, were co-delivered and shown to be sequentially released from one hydrogel which could be beneficial in terms of heterologous immunization or single dose vaccination. In summary, this study presents a tunable, versatile applicable, and effective delivery platform that could improve vaccination effectiveness also for other infectious diseases than HIV-1. [ABSTRACT FROM AUTHOR]

Since articular cartilage does not regenerate itself, researches are underway to heal damaged articular cartilage by applying biomaterials such as a hydrogel. In this study, we have constructed a dual-layer composite hydrogel mimicking the layered structure of articular cartilage. The top layer consists of a high-density PEG hydrogel prepared with 8-arm PEG and PEG diacrylate using thiol-norbornene photo-click chemistry. The compressive modulus of the top layer was 700.1 kPa. The bottom layer consists of a low-density PEG hydrogel reinforced with a 3D silk fiber construct. The low-density PEG hydrogel was prepared with 4-arm PEG using the same cross-linking chemistry, and the compressive modulus was 13.2 kPa. Silk fiber was chosen based on the strong interfacial bonding with the low-density PEG hydrogel. The 3D silk fiber construct was fabricated by moving the silk fiber around the piles using a pile frame, and the compressive modulus of the 3D silk fiber construct was 567 kPa. The two layers were joined through a covalent bond which endowed sufficient stability against repeated torsions. The final 3D silk fiber construct embedded dual-layer PEG hydrogel had a compressive modulus of 744 kPa. Chondrogenic markers confirmed the chondrogenic differentiation of human mesenchymal stem cells encapsulated in the bottom layer.

Lumenogenesis within the epiblast represents a critical step in early human development, priming the embryo for future specification and patterning events. However, little is known about the specific mechanisms that drive this process due to the inability to study the early embryo in vivo. While human pluripotent stem cell (hPSC)-based models recapitulate many aspects of the human epiblast, most approaches for generating these 3D structures rely on ill-defined, reconstituted basement membrane matrices. Here, we designed synthetic, nonadhesive polyethylene glycol (PEG) hydrogel matrices to better understand the role of matrix mechanical cues in iPSC morphogenesis, specifically elastic modulus. First, we identified a narrow range of hydrogel moduli that were conducive to the hPSC viability, pluripotency, and differentiation. We then used this platform to investigate the effects of the hydrogel modulus on lumenogenesis, finding that matrices of intermediate stiffness yielded the most epiblast-like aggregates. Conversely, stiffer matrices impeded lumen formation and apico-basal polarization, while the softest matrices yielded polarized but aberrant structures. Our approach offers a simple, modular platform for modeling the human epiblast and investigating the role of matrix cues in its morphogenesis.

Synthetic hydrogels, such as poly(ethylene glycol) (PEG), are promising for a range of in vivo applications. However, like all non-biological biomaterials, synthetic hydrogels including PEG elicit a foreign body response (FBR). The FBR is thought to be initiated by adsorbed protein that is recognized by and subsequently activates inflammatory cells, notably macrophages, and culminates with fibrotic encapsulation. However, the molecular mechanisms that drive the FBR are not well understood. Toll-like receptors (TLRs) are key receptors that recognize pathogens, but also recognize altered host proteins that display damage-associated molecular patterns (DAMPs). Thus TLRs may play a role in the FBR. Here, we investigated myeloid differentiation primary response gene 88 (MyD88), a signaling adaptor protein that mediates inflammatory cytokine production induced by most TLRs. An in vitro model was used consisting of macrophages cultured on the surface of synthetic hydrogels, specifically PEG, with pre-adsorbed serum proteins. Our in vitro findings demonstrate that MyD88-dependent signaling is the predominant inflammatory pathway in macrophage activation to synthetic hydrogels. When stimulated with TLR agonists to mimic additional DAMPs present in vivo , MyD88-dependent signaling was also the predominant pathway in macrophage activation. An in vivo model of PEG hydrogels implanted subcutaneously in wild-type and MyD88−/− mice also demonstrated that MyD88 is the key contributor to the recruitment of inflammatory cells and formation of the fibrous capsule surrounding the implanted hydrogel. Taken together, findings from this study identify MyD88-mediated inflammation as being a critical pathway involved not only in the inflammatory response, but in formation of the fibrous capsule to PEG hydrogels. Synthetic hydrogels are promising for in vivo applications but, like all non-biological biomaterials, synthetic hydrogels elicit a foreign body response (FBR). The molecular mechanisms that drive the FBR are not well understood. This work identifies the myeloid differentiation primary response gene 88 (MyD88) as a central mediator to macrophage activation in response to a poly(ethylene glycol) hydrogel with pre-adsorbed proteins in vitro. Moreover, MyD88 was also central to the recruitment of inflammatory cells, which included neutrophils, monocytes, and macrophages, to implanted PEG hydrogels and to fibrous encapsulation. These findings demonstrate that MyD88-mediated inflammation is responsible in part for the formation of the fibrous capsule of the FBR. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Decellularized matrix is of great interest as a scaffold for the tissue engineering heart valves due to its naturally three-dimensional structure and bioactive composition. A primary challenge of tissue engineered heart valves based on decellularized matrix is to grow a physiologically appropriate cell population within the leaflet tissue. In this study, a composite scaffold was fabricated by the combination of a porous matrix metalloproteinase (MMP) degradable poly (ethylene glycol) (PEG) hydrogel that were loaded with stromal cell-derived factor-1α (SDF-1α) and a mechanically supportive decellularized porcine aortic valve. Results demonstrated that the modified scaffold enhanced bone marrow mesenchymal stem cells (BMSC) adhesion, viability and proliferation, and promoted BMSC differentiate into valve interstitial-like cells. Furthermore, these modifications lead to enhanced protection of the scaffold from thrombosis. In vivo assessment by rat subdermal model showed the modified scaffold was highly biocompatible with tissue remodeling characterized by promoting mesenchymal stem cells recruitment and facilitating M2 macrophage phenotype polarization. The surface layers of PEG hydrogel not only could provide a niche for cell migration, proliferation and differentiation, but also protect the scaffolds from rapid degeneration, inflammation and calcification. The intermediate layer of decellularized valve could maintain the organization of the scaffold and perform the valve function. The promising results emphasize the potential of our scaffolds to improve recellularization and promote remodeling of implanted decellularized valves. These findings suggest that the SDF-1α loaded MMP degradable PEG hydrogel modification could be an efficient approach to develop functional decellularized heart valve. Statement of significance A composite scaffold was fabricated by the combination of a porous matrix metalloproteinase (MMP) degradable poly (ethylene glycol) (PEG) hydrogel that were loaded with SDF-1α and a mechanically supportive decellularized porcine aortic valve. The surface layers of PEG hydrogel not only could provide a niche for cell migration, proliferation and differentiation, but also protect the scaffolds from rapid degeneration, inflammation and calcification. The intermediate layer of decellularized valve could maintain the organization of the scaffold and perform the valve function. The promising results emphasize the ability of our scaffolds to improve recellularization and promote remodeling of implanted decellularized valves. This suggests that the extracellular matrix-based valve scaffolds have potential for clinical applications. [ABSTRACT FROM AUTHOR]

In this work a novel, relatively simple, and fast method for patterning of gold nanoparticles (Au NPs) on poly(ethylene glycol) (PEG)-based hydrogels is presented. In the hereby exploited reactive micro-contact printing (reactive-μ-CP) process, the surface of a micro-relief patterned PDMS-stamp is first functionalized with an amino-silane self-assembled monolayer (SAM), which is then inked with Au NPs. The stamp is subsequently brought into conformal contact with thiol-functionalized PEG-based hydrogel films. Due to the strong gold-thiol interactions the Au NPs are adequately and easily transferred onto the surfaces of these soft, multifunctional PEG hydrogels. In this way, defined μ-patterns of Au NPs on PEG hydrogels are achieved. These Au NPs patterns allow specific biomolecular interactions on PEG surfaces, and cell adhesion has been studied. Cells were found to effectively adhere only on Au NPs micro-patterns and to avoid the anti-adhesive PEG background. Besides the cell adhesion studies, these Au NPs μ-patterns can be potentially applied as biosensors in plasmon-based spectroscopic devices or in medicine, e.g., for drug delivery systems or photothermal therapies.

While various static cues such as matrix stiffness have been known to regulate stem cell differentiation, it is unclear whether or not dynamic cues such as degradation rate along with the change of material chemistry can influence cell behaviors beyond simple integration of static cues such as decreased matrix stiffness. The present research is aimed at examining effects of degradation rates on adhesion and differentiation of mesenchymal stem cells (MSCs) in vitro on well-defined synthetic hydrogel surfaces. Therefore, we synthesized macromers by extending both ends of poly(ethylene glycol) (PEG) with oligo(lactic acid) and then acryloyl, and the corresponding hydrogels that were obtained after photopolymerization of the macromers were biodegradable. Combining the unique techniques of block copolymer micelle nanolithography with transfer lithography, we prepared a nanoarray of cell-adhesive arginine-glycine-aspartate peptides on this nonfouling biodegradable hydrogel. The biodegradation is caused by hydrolysis of the ester bonds, and different degradation rates in the cell culture medium were achieved by different stages of accelerated pre-hydrolysis in an acidic medium. For the following cell culture and induction, both the matrix stiffness and degradation rate varied among the examined groups. While adipogenic differentiation of MSCs can be understood by the lowered stiffness, the osteogenic differentiation was contradictory with common sense because we found enhanced osteogenesis on soft hydrogels. Higher degradation rates were suggested to account for this interesting phenomenon in the sole osteogenic/adipogenic induction and even more complicated trends in the co-induction. Hence, the degradation rate is a dynamic cue influencing cell behaviors, which should be paid attention to for degradable biomaterials. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor in adults because of its highly invasive behavior. The existing treatment for GBM, which involves a combination of resection, chemotherapy, and radiotherapy, has a very limited success rate with a median survival rate of

We describe the preparation, characterization and evaluation of a biodegradable radiopaque water-triggered shape memory embolization plug for temporary vascular occlusion. The shape memory occluding device consists of a composite of a radio-opaque filler and a poly ( dl -lactide- co -glycolide) (PLGA) blend, which was coated with a crosslinked poly (ethylene glycol) diacrylate (PEGDA) hydrogel. The mechanical properties, the degradation timeframe, the effect of programming conditions on the shape memory behaviour and the extent of radio-opacity for imaging were evaluated. Based on the tests, the mechanism responsible for the water-induced shape memory effect in such an embolization plug was elucidated. Suitable materials were optimized to fabricate an embolic plug prototype and its in vitro performance was evaluated as an occlusion rate (using a custom-built set up) and its biocompatibility. Finally, a feasibility study was conducted in vivo in a rabbit model to investigate the ease of device deployment, device migration and extent of vessel occlusion. The in vivo results demonstrated that the prototypes were visible under fluoroscopy and complete vascular occlusion occurred within 2 min of deployment of the prototypes in vivo . In conclusion, the developed embolization plug enables controlled and temporary vascular embolization, and is ready for safety studies. [ABSTRACT FROM AUTHOR]

Background: Injuries to the human native cartilage tissue are particularly problematic because cartilage has little to no ability to heal or regenerate itself. Employing a tissue engineering strategy that combines suitable cell sources and biomimetic hydrogels could be a promising alternative to achieve cartilage regeneration. However, the weak mechanical properties may be the major drawback to use fully degradable hydrogels. Besides, most of the fully degradable hydrogels degrade too fast to permit enough extracellular matrix (ECM) production for neocartilage formation. In this study, we demonstrated the feasibility of neocartilage regeneration using swine articular chondrocytes photoencapsualted into poly (ethylene glycol) dimethacrylate (PEGDM) copolymer hydrogels composed of different degradation profiles: degradable (PEG-LA-DM) and nondegradable (PEGDM) macromers in molar ratios of 50/50, 60/40, 70/30, 80/20, and 90/10.Methods: Articular chondrocytes were isolated enzymatically from juvenile Yorkshire swine cartilage. 6 × 10(7) cells cells were added to each milliliter of macromer/photoinitiator (I2959) solution. Nonpolymerized gel containing the cells (100 μL) was placed in cylindrical molds (4.5 mm diameter × 6.5 mm in height). The macromer/photoinitiator/chondrocyte solutions were polymerized using ultraviolet (365 nm) light at 10 mW/cm(2) for 10 mins. Also, an articular cartilaginous ring model was used to examine the capacity of the engineered cartilage to integrate with native cartilage. Samples in the pilot study were collected at 6 weeks. Samples in the long-term experimental groups (60/40 and 70/30) were implanted into nude mice subcutaneously and harvested at 6, 12 and 18 weeks. Additionally, cylindrical constructs that were not implanted used as time zero controls. All of the harvested specimens were examined grossly and analyzed histologically and biochemically.Results: Histologically, the neocartilage formed in the photochemically crosslinked gels resembled native articular cartilage with chondrocytes in lacunae and surrounded by new ECM. Increases in total DNA, glycosaminoglycan, and hydroxyproline were observed over the time periods studied. The neocartilage integrated with existing native cartilage.Conclusions: Articular cartilage generation was achieved using swine articular chondrocytes photoencapsulated in copolymer PEGDM hydrogels, and the neocartilage tissue had the ability to integrate with existing adjacent native cartilage. [ABSTRACT FROM AUTHOR]

Lung tissue biopsies can result in a leakage of blood (hemothorax) and air (pneumothorax) from the biopsy tract, which threatens the patient with a collapsed lung and other complications. We have developed a lung biopsy tract sealant based on a thiol-ene-crosslinked PEG hydrogel and polyurethane shape memory polymer (SMP) foam composite. After insertion into biopsy tracts, the PEG hydrogel component contributes to sealing through water-driven swelling, whereas the SMP foam contributes to sealing via thermal actuation. The gelation kinetics, swelling properties, and rheological properties of various hydrogel formulations were studied to determine the optimal formulation for composite fabrication. Composites were then fabricated via vacuum infiltration of the PEG hydrogel precursors into the SMP foam followed by thermal curing. After drying, the composites were crimped to enable insertion into biopsy tracts. Characterization revealed that the composites exhibited a slight delay in shape recovery compared to control SMP foams. However, the composites were still able to recover their shape in a matter of minutes. Cytocompatibility testing showed that leachable byproducts can be easily removed by washing and washed composites were not cytotoxic to mouse lung fibroblasts (L929s). Benchtop testing demonstrated that the composites can be easily deployed through a cannula, and the working time for deployment after exposure to water was 2 min. Furthermore, testing in an in vitro lung model demonstrated that the composites were able to effectively seal a lung biopsy tract and prevent air leakage. Collectively, these results show that the PEG hydrogel/SMP foam composites have the potential to be used as lung biopsy tract sealants to prevent pneumothorax post-lung biopsy.

In this study, hydrophilic and hydrolytically degradable poly (ethylene glycol) (PEG) hydrogels were formed via Michael-type addition and employed for sustained delivery of a monoclonal antibody against the protective antigen of anthrax. Taking advantage of the PEG-induced precipitation of the antibody, burst release from the matrix was avoided. These hydrogels were able to release active antibodies in a controlled manner from 14 days to as long as 56 days in vitro by varying the polymer architectures and molecular weights of the precursors. Analysis of the secondary and tertiary structure and the in vitro activity of the released antibody showed that the encapsulation and release did not affect the protein conformation or functionality. The results suggest the promise for developing PEG-based carriers for sustained release of therapeutic antibodies against toxins in various applications. [ABSTRACT FROM AUTHOR]

Expanded polytetrafluoroethylene (ePTFE) grafts were coated on the luminal surface with a cell-adhesive fluorosurfactant (FSP) polymer to promote endothelialization, followed by ethanol hydration to degas the pores and subsequent cell-adhesive, enzymatically degradable poly(ethylene glycol)- based hydrogel incorporation into the graft interstices to accommodate potential smooth muscle cell integration in the graft wall. The FSP coating on ePTFE was stable as demonstrated by a significantly reduced receding water contact angle on FSPcoated ePTFE (14.566.4°) compared to uncoated ePTFE (105.3±4.5°, P<0.05) after ethanol exposure. X-ray photoelectron spectroscopy analysis of the same surfaces confirmed FSP presence. Localization of the FSP and hydrogel within the ePTFE graft construct was assessed using fluorescently labeled polymers, and demonstrated hydrogel infiltration throughout the thickness of the graft wall, with FSP coating limited to the lumen and adventitial surfaces. FSP at the luminal surface on dualcoated grafts was able to bind endothelial cells (EC) (98.7±23.1 cells/mm²) similar to fibronectin controls (129.4±40.7 cells/ mm²), and significantly higher than uncoated ePTFE (31.6±19 cells/mm², P<0.05). These results indicate that ePTFE grafts can be simultaneously modified with two different polymers that have potential to directly address both endothelialization and intimal hyperplasia. Such a construct is a promising candidate for an off-the-shelf synthetic graft for small-diameter graft applications. [ABSTRACT FROM AUTHOR]

Glioblastoma (GBM) is the most aggressive brain tumor, with 12–15 months median survival time despite current treatment efforts. Among the alternative treatment approaches that have gained acceptance over the last decade is the use of replication-competent oncolytic adenoviruses, which are promising due to their relatively low toxicity and tumor-specific targeting. Three-dimensional (3D) tumor models can mimic the physiological microenvironment of GBM tumors and provide valuable information about the interaction between tumor cells and adenoviruses. Therefore, robust in vitro 3D tumor models are critical to investigate the mechanisms underlying tumor progression and explore the cytotoxicity effect of the adenovirus on tumor cells. In this study, we used a hydrogel microwell platform to generate in vitro 3D GBM spheroids and studied their interactions with the Delta-24-RGD adenovirus. The results showed that the cultured 3D spheroids were successfully infected by the Delta-24-RGD. A significant cell lysis was observed. Cell viability was decreased approximately 37%, 54% and 65% with 10, 50, and 100 MOIs, respectively. The infection of the Delta-24-RGD was found more effective on 3D spheroids when compared to 2D monolayer cell culture. These results implicate that our hydrogel microwell platform could provide a promising 3D model to investigate the oncolytic potential of the viruses in vitro. [ABSTRACT FROM PUBLISHER]

Glioblastoma (GBM) is the most common form of primary brain tumor with a high infiltrative capacity, increased vascularity, and largely elusive tumor progression mechanism. The current GBM treatment methods do not increase the patient survival rate and studies using two-dimensional (2D) cell cultures and in vivo animal models to investigate GBM behavior and mechanism have limitations. Therefore, there is an increasing need for in vitro three-dimensional (3D) models that closely mimic in vivo microenvironment of the GBM tumors to understand the underlying mechanisms of the tumor progression. In this study we propose to use a 3D in vitro model to overcome these limitations, using poly (ethylene glycol) dimethyl acrylate (PEGDA) hydrogel-based microwells and co-culture GBM (U87) cells and endothelial cells (HUVEC) in the 3D microwells to provide a 3D in vitro simulation of the tumor microenvironment. Furthermore, we investigated the gene expression differences of co-cultures by quantitative real-time PCR. Our results suggested that the relative expression profiles of tumor angiogenesis markers, PECAM1/CD31, and VEGFR2, in co-cultures are consistent with in vivo GBM studies. Furthermore, we suggest that our microwell platform could provide robust and useful 3D co-culture models for high-throughput drug screening and treatment of the GBM. [ABSTRACT FROM PUBLISHER]

While cell condensation has been thought to enhance chondrogenesis, no direct evidence so far confirms that cell–cell contact itself increases chondrogenic differentiation of stem cells, since the change of cell–cell contact is usually coupled with those of other cell geometry cues and soluble factors in cell culture. The present study semi-quantitatively examined the effect of cell–cell contact in a decoupled way. We fabricated two-dimensional micropatterns with cell-adhesive peptide arginine-glycine-aspartate (RGD) microdomains on a nonfouling poly(ethylene glycol) (PEG) hydrogel. Mesenchymal stem cells (MSCs) were well localized on the microdomains for a long time. Based on our micropattern design, single MSCs or cell clusters with given cell numbers (1, 2, 3, 6 and 15) and a similar spreading area per cell were achieved on the same substrate, thus the interference of soluble factor difference from cell autocrine and that of cell spreading area were ruled out. After 9-day chondrogenic induction, collagen II was stained to characterize the chondrogenic induction results; the mRNA expression levels of SOX9, collagen II, aggrecan, HIF-1α and collagen I were also detected. The statistics confirmed unambiguously that the extent of the chondrogenic differentiation increased with cell–cell contact, and even a linear relation between differentiation extent and contact extent was established within the examined range. The cell–cell contact effect worked under both hypoxia (5% O 2 ) and normoxia (21% O 2 ) conditions, and the hypoxia condition promoted the chondrogenic induction of MSCs on adhesive microdomains more efficiently than the normoxia condition under the same cell–cell contact extents. [ABSTRACT FROM AUTHOR]

We report on the use of magnetic resonance imaging (MRI)-based non-invasive monitoring to document the role of protein adjuvants in hydrogel implant integration in vivo . Polyethylene glycol (PEG) hydrogels were formed with different protein constituents, including albumin, fibrinogen and gelatin. The hydrogels were designed to exhibit similar material properties, including modulus, swelling and hydrolytic degradation kinetics. The in vivo resorption properties of these PEG-based hydrogels, which contained a tethered gadolinium contrast agent, were characterized by MRI and histology, and compared to their in vitro characteristics. MRI data revealed that PEG–Albumin implants remained completely intact throughout the experiments, PEG–Fibrinogen implants lost about 10% of their volume and PEG–Gelatin implants underwent prominent swelling and returned to their initial volume by day 25. Fully synthetic PEG–diacrylate (PEG–DA) control hydrogels lost about half of their volume after 25 days in vivo . Transverse MRI cross-sections of the implants revealed distinct mechanisms of the hydrogel's biodegradation: PEG–Fibrinogen and PEG–Albumin underwent surface erosion, whereas PEG–Gelatin and PEG–DA hydrogels mainly underwent bulk degradation. Histological findings substantiated the MRI data and demonstrated significant cellular response towards PEG–DA and PEG–Gelatin scaffolds with relatively low reaction towards PEG–Fibrinogen and PEG–Albumin hydrogels. These findings demonstrate that PEG–protein hydrogels can degrade via a different mechanism than PEG hydrogels, and that this difference can be linked to a reduced foreign body response. [ABSTRACT FROM AUTHOR]

Avastin® has been clinically proved to be effective in the treatment of intraocular neovascularization diseases. However, the short half-life of Avastin® need frequent administration to maintain its therapeutic efficiency. In this paper, we attempted to develop an in situ PEG hydrogels with great biocompatibility for sustained release of Avastin® to inhibit the corneal neovascularization. PEG hydrogels was formed via thiol-maleimide reaction using 4-arm PEG-Mal and 4-arm PEG-SH. The transparent hydrogel was rapidly formed under physiological conditions. By varying the concentration of 4-arm PEG-SH, PEG hydrogel with different gelling time, pore size, swelling ratio and mechanical property could be obtained. In vitro cytotoxicity indicated that the developed PEG hydrogel had no apparent cytotoxicity on L-929 cells after 7 days of incubation. In vitro release study showed the encapsulated Avastin® was sustained release from PEG hydrogels within a period of 14 days study. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis further confirmed that the released Avastin® did not undergo apparent hydrolysis within 14 days. As a conclusion, we could conclude that the developed PEG hydrogels as an injectable hydrogels might be suitable for extended Avastin® release to treat the corneal neovascularization. [ABSTRACT FROM AUTHOR]

Abstract: Dedifferentiation of chondrocytes is common in culturing, and seriously affects the restorative efficacy of cartilage repair. The present study examines the effect of initial cell shapes on dedifferentiation of chondrocytes in vitro. The cell shape was controlled with a unique material micropatterning technique. With this technique, a series of microarrays of cell-adhesive peptide arginine-glycine-aspartate (RGD) were generated on a persistent non-fouling poly(ethylene glycol) (PEG) hydrogel. After culturing chondrocytes derived from rats on the micropatterned surfaces, the cell shapes were adapted by the geometries of adhesive microislands with pre-defined diameters (10, 15, 20 and 30 μm) for round ones and aspect ratios (1, 1.2, 1.5, 2, 4 and 6) for elliptical ones. After 10 days, collagen II staining was demonstrated to identify normal chondrocytes and dedifferentiated cells for those single cells on microislands. Furthermore, the gene expression of collagen II, collagen I, aggrecan and SOX9 were detected by qRT-PCR. The statistical results illustrated that dedifferentiation of chondrocytes happened more probably in the cases of larger sizes and higher aspect ratios. The conclusions stand under circumstances of both normoxia (21% O2) and hypoxia (5% O2) atmospheres. [Copyright &y& Elsevier]

Transplantation of cells within poly(ethylene glycol) (PEG) hydrogel scaffolds as effective immunoisolation barriers is becoming increasingly important strategy for tissue engineering and regenerative medicine. In these applications, crosslink density of these membranes has significant effect on the control of diffusion of many biomolecules such as nutrients, cellular wastes, and hormones. When these networks are designed with crosslink density gradients, alterations in network structure may have an effect on biomolecule diffusivity. The goal of this work was to synthesize PEG hydrogels via surface initiated photopolymerization for use in applications involving physiological protein delivery and cell encapsulation. For this purpose, PEG hydrogels of differing crosslink density gradients were formed via surface initiated photopolymerization, and the diffusion of model proteins with various molecular weights were observed through these PEG hydrogel scaffolds with defined properties. Diffusion coefficients were on the order of 10−7−10−8 cm2/s and protein diffusion time scales varied from 5 min to 30 h. The results confirm that synthetic PEG hydrogels with crosslink density gradients are promising for controlled release of bioactive molecules and for covalent incorporation of ligands to support cell viability. [ABSTRACT FROM AUTHOR]

[Display omitted] Intraperitoneal (IP) drug delivery of chemotherapeutic agents, administered through hyperthermal intraperitoneal chemotherapy (HIPEC) and pressurized intraperitoneal aerosolized chemotherapy (PIPAC), is effective for the treatment of peritoneal malignancies. However, these therapeutic interventions are cumbersome in terms of surgical practice and are often associated with the formation of peritoneal adhesions, due to the catheters inserted into the peritoneal cavity during these procedures. Hence, there is a need for the development of drug delivery systems that can be administered into the peritoneal cavity. In this study, we have developed a nanocapsule (NCs)-loaded hydrogel for drug delivery in the peritoneal cavity. The hydrogel has been developed using poly(ethylene glycol) (PEG) and thiol-maleimide chemistry. NCs-loaded hydrogels were characterized by rheology and their resistance to dilution and drug release were determined in vitro. Using IVIS® to measure individual organ and recovered gel fluorescence intensity, an in vivo imaging study was performed and demonstrated that NCs incorporated in the PEG gel were retained in the IP cavity for 24 h after IP administration. NCs-loaded PEG gels could find potential applications as biodegradable, drug delivery systems that could be implanted in the IP cavity, for example at a the tumour resection site to prevent recurrence of microscopic tumours. [ABSTRACT FROM AUTHOR]

The present report is an extension of our preceding publication in Biomaterials (2013) entitled "Effect of RGD nanospacing on differentiation of stem cells." Cell-adhesive peptide arginine-glycine-aspartate (RGD) was nanopatterned on a non-fouling poly(ethylene glycol) (peG) hydrogel, and mesenchymal stem cells (Mscs) derived from rat bone marrow were cultured on the patterned surfaces at nanospacings from 37 to 124 nm. Cell adhesion parameters such as spreading areas varied with RGD nanospacings significantly. The differences were well observed at both the first and eighth days, which confirmed the persistence of this nanospacing efect on our nanopatterns. The proliferation rate also varied with the nanospacings. Osteogenic and adipogenic inductions were undertaken, and a significant influence of RGD nanospacing on stem cell differentiation was found. The effect on differentiation cannot be simply interpreted by differences in cell adhesion and proliferation. We further calculated the fractions of single, coupled, and multiple cells on those nanopatterns, and ruled out the possibility that the extent of cell-cell contact determined the different differentiation fractions, Accordingly, we reinforced the idea that RGD nanospacing might directly influence stem cell differentiation. [ABSTRACT FROM AUTHOR]

An amino acid possessing a maleimide side chain was developed and synthesized in good yield. With a propensity to undergo the Michael addition reaction, the creation of a maleimide amino acid derivative was targeted for use as a highly functional tool for enabling peptide conjugation and structural modifications. After addressing the inherent potential side reactions of maleimides during solid phase peptide synthesis, the ability to incorporate the maleimide amino acid in an RGDS peptide sequence was demonstrated. H NMR and mass spectroscopic techniques enabled thorough characterization of the peptide sequence, confirming the presence of the maleimide functionality. Once characterized, the ability to use the maleimide moiety as a peptide modification tool was investigated. Specifically, it was shown that the maleimide functional group could be exploited, given the proper reaction conditions, to anchor a peptide to a surface and create a cyclic conformation from a linear sequence. Furthermore, bioactivity of the peptide containing maleimide amino acid was evaluated by studying cellular interactions with surfaces functionalized with an integrin binding sequence. [ABSTRACT FROM AUTHOR]

Dynamic loading has emerged as an important part of cartilage tissue engineering strategies for enhancing tissue production and producing cartilage with functionally competent mechanical properties. As patients in need of cartilage span a range of age groups, questions arise as to the role of age in a cell's ability to respond to dynamic loading. Therefore, this study's goal was to characterize age-related anabolic and catabolic responses of chondrocytes to dynamic compressive loading. Bovine chondrocytes isolated from juvenile (3-week-old) and adult (2- to 3-year-old) donors were encapsulated in poly(ethylene glycol) hydrogels and subjected to dynamic loading applied intermittently in a sinusoidal waveform at 1 or 0.3 Hz with 5 or 10% amplitude strain up to 2 weeks. Loading significantly enhanced total sulfated glycosaminoglycan (sGAG) production by 220% for juvenile chondrocytes with 0.3 Hz/5% loading and by 88% for adult chondrocytes with 1 Hz/5% loading, while all other loading regimes did not affect or inhibited total sGAG production. Contrarily, deposition of larger matrix molecules of aggrecan and collagen II was either not affected or inhibited by loading. Collagen VI deposition was significantly upregulated by loading but only in adult chondrocytes and under different loading regimes (1 Hz/10% and 0.3 Hz/5%) when compared to total sGAGs. Both cell populations displayed catabolic activity, which appeared to be stimulated by loading. Taken together, findings from this study suggest that loading differentially regulates matrix synthesis and the response is highly dependent on donor age. Biotechnol. Bioeng. 2013; 110: 2046-2057. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: The present study is aimed to examine the shape effect on lineage commitment of stem cells in growth medium free of external chemical induction factors. Aspect ratios (ARs) of cells were controlled by micropatterns with cell-adhesive microislands of AR 1, 2 and 8 on the potent nonfouling background of poly(ethylene glycol) hydrogels, and the single stem cells were well shaped for 19 days. Mesenchymal stem cells (MSCs) derived from rat bone marrow were cultured in osteogenic medium, adipogenic medium, mixed coinduction medium, and also growth medium; alkaline phosphatase (ALP) and oil droplets were employed as indicators of osteoblasts and adipocytes, respectively. Those indicators were well observed in all of three induction media as early as day 7, and also in growth medium at a longer culture time till day 13. While a significant monotonic decrease of adipogenesis was observed with the increase of AR, a non-monotonic change of osteogenesis was found with optimal AR about 2. The relative gene expressions further verified the above findings. As a result, cell shape itself is an inherent cue to regulate stem cell differentiation, let alone with or without external chemical induction factors. Such a shape effect disappeared upon addition of a microfilament inhibitor cytochalasin D or a Rho-associated protein kinase (ROCK) inhibitor Y-27632. So, formation of cytoskeleton is necessary for the shape effect, and the ROCK-pathway-related cell tension is responsible for the shape effect on the lineage commitment of stem cells even in growth medium. [Copyright &y& Elsevier]

Objective: Incisional cerebrospinal fluid (CSF) leakage after cranial surgery is a significant cause of morbidity due to poor wound healing and infection, meningitis, and pseudomeningocele formation. Many common dural closure techniques, such as sutures, autologous grafts, gelatin or collagen sponges, and fibrin glues, are used to achieve watertight closure, although none are US Food and Drug Administration approved for this use. DuraSeal Dural Sealant System is a polyethylene glycol (PEG) hydrogel approved by the U.S. Food and Drug Administration for obtaining watertight dural closure when applied after standard dural suturing. This multicenter, prospective randomized study further evaluated the safety of a PEG hydrogel compared with common dural sealing techniques. Methods: A total of 237 patients undergoing elective cranial surgery at 17 institutions were randomized to dural closure augmented with the PEG hydrogel or a control “standard of care” dural sealing technique after Valsalva maneuver demonstrated an intraoperative nonwatertight dural closure. Data were collected on complications resulting in unplanned postoperative interventions or reoperations, surgical site infections, CSF leaks, and other neurological complications within 30 days. Surgeons also provided data on the ease of use of the dural sealing techniques, as well as preparation and application times. Results: The incidences of neurosurgical complications, surgical site infections, and CSF leaks were similar between treatment and control groups, with no statistically significant difference between the measures. In the PEG hydrogel group (n = 120), the incidence of neurosurgical complications was 5.8% (n = 7), the incidence of surgical site infections was 1.7% (n = 2), and the incidence of CSF leak was 0.8% (n = 1). In the control group (n = 117), the incidence of neurosurgical complications was 7.7% (n = 9), the incidence of surgical site infection was 2.6% (n = 3), and the incidence of CSF leak was 1.7% (n = 2). Sealant preparation time was less than 5 minutes in 96.6% of the PEG hydrogel group compared with 66.4% of controls (P < 0.001). The dural augmentation was applied in less than 1 minute in 85.7% of the PEG hydrogel group compared with 66.4% of the control group (P < 0.001). Conclusions: The PEG hydrogel dural sealant used in this study has a similar safety profile to commonly used dural sealing techniques when used as dural closure augmentation in cranial surgery. The PEG hydrogel dural sealant demonstrated faster preparation and application times than other commonly used dural sealing techniques. [Copyright &y& Elsevier]

Abstract: Age is a risk factor in developing osteoarthritis, but the link is not well understood. It is thought that age predisposes the tissue to osteoarthritis when other risk factors are involved, e.g. abnormal biomechanics. Therefore, this study aimed to test the hypothesis that chondrocyte response to injurious loading is dependent on donor age. Bovine chondrocytes were selected as model cells and isolated from skeletally immature (juvenile, 1–3 weeks) or mature (adult, 2–3 years) cartilage to represent different aged donors. Juvenile and adult chondrocytes were encapsulated in identical 3D poly(ethylene glycol) hydrogels and subjected to an initial compressive impact load of 25.6±7.5kN/m2 applied to 50% strain. Under free swelling culture, adult chondrocytes exhibited higher intracellular ROS levels and catabolism, specifically collagen degradation, when compared to juvenile chondrocytes. In response to injurious load, adult chondrocytes responded with higher cell death, while juvenile chondrocytes responded with greater apoptosis and greater increases in intracellular ROS. With respect to anabolism and catabolism in response to injurious load, adult chondrocytes exhibited decreased aggrecan and collagen deposition, while juvenile chondrocytes exhibited decreased proteoglycan synthesis and increased collagen degradation. Overall, chondrocytes responded to injury regardless of age, but exhibited age-dependent responses with respect to anabolism and catabolism. These findings confirm that age influences how chondrocytes respond to abnormal biomechanical cues, warranting further study into the mechanisms of how cells, age, and injury contribute to the onset of osteoarthritis. [Copyright &y& Elsevier]

The effects of microenvironmental geometric configurations on hepatocyte self-assembly were investigated for the first time. Primary hepatocytes were cultured on a flat surface and in differently shaped hollow lumens of two gel types: a native hydrogel (alginate) and a synthetic hydrogel (polyethylene glycol, PEG). The lumens were in the shapes of a cylinder, triangular prism and square column. The results of cell morphology and functionality revealed that a better culture environment for rapid spheroid formation was achieved in the hollow lumens of alginate gel than on the flat surface. Among the lumen configurations, the cylindrical one was the best. Additionally, differences between cell behaviors on a flat surface and in a hollow cylinder lumen were more evident in the PEG hydrogel. Hence, a microenvironment with the proper geometric morphology can benefit the aggregation of hepatocytes and facilitate spheroid formation. [ABSTRACT FROM AUTHOR]