Blend Hydrogel Research Articles

Methacrylated gellan gum and hyaluronic acid hydrogel blends for image-guided neurointerventions.

Cell-based therapies delivered via intrathecal injection are considered as one of the most promising solutions for the treatment of amyotrophic lateral sclerosis (ALS). Herein, injectable manganese-based biocompatible hydrogel blends were developed, that can allow image-guided cell delivery. The hydrogels can also provide physical support for cells during injection, and at the intrathecal space after transplantation, while assuring cell survival. In this regard, different formulations of methacrylated gellan gum/hyaluronic acid hydrogel blends (GG-MA/HA) were considered as a vehicle for cell delivery. The hydrogels blends were supplemented with paramagnetic Mn2+ to allow a real-time monitorization of hydrogel deposition via T1-weighted magnetic resonance imaging (MRI). The developed hydrogels were easily extruded and formed a stable fiber upon injection into the cerebrospinal fluid. Hydrogels prepared with a 75 : 25 GG-MA to HA ratio supplemented with MnCl2 at 0.1 mM showed controlled hydrogel degradation, suitable permeability, and a distinct MRI signal in vitro and in vivo. Additionally, human-derived adipose stem cells encapsulated in 75 : 25 GG-MA/HA hydrogels remained viable for up to 14 days of culture in vitro. Therefore, the engineered hydrogels can be an excellent tool for injectable image-guided cell delivery approaches.

Perfusion-based co-culture model system for bone tissue engineering.

In this work, we report on a perfusion-based co-culture system that could be used for bone tissue engineering applications. The model system is created using a combination of Primary Human Umbilical Vein Endothelial Cells (HUVECs) and osteoblast-like Saos-2 cells encapsulated within a Gelatin Methacrylate (GelMA)-collagen hydrogel blend contained within 3D printed, perfusable constructs. The constructs contain dual channels, within a custom-built bioreactor, that were perfused with osteogenic media for up to two weeks in order to induce mineral deposition. Mineral deposition in constructs containing only HUVECs, only Saos-2 cells, or a combination thereof was quantified by microCT to determine if the combination of endothelial cells and bone-like cells increased mineral deposition. Histological and fluorescent staining was used to verify mineral deposition and cellular function both along and between the perfused channels. While there was not a quantifiable difference in the amount of mineral deposited in Saos-2 only versus Saos-2 plus HUVEC samples, the location of the deposited mineral differed dramatically between the groups and indicated that the addition of HUVECs within the GelMA matrix allowed Saos-2 cells, in diffusion limited regions of the construct, to deposit bone mineral. This work serves as a model on how to create perfusable bone tissue engineering constructs using a combination of 3D printing and cellular co-cultures.

Agarose-Based Gel-Phase Microextraction Technique for Quick Sampling of Polar Analytes Adsorbed on Surfaces.

Sampling and extraction of chemical residues present on flat or curved surfaces as well as touch-sensitive objects are challenging. Hydrogels are characterized by high mechanical flexibility and water content. Thus, they are an ideal medium for transferring water-soluble analytes from a sampled surface to the next stage of an analytical workflow. Here, we demonstrate gel-phase microextraction (GPME), in which disks of blended hydrogels are utilized to lift traces of water-soluble substances adsorbed on surfaces. The protocol has been optimized in a series of tests involving fluorometric and mass spectrometric measurements. Compared with the pure agarose hydrogel, most of the tested blended hydrogels provide a higher efficiency for the sampling/extraction of a model analyte, fluorescein. The blended hydrogel disks are incorporated into three-dimensional (3D)-printed acrylonitrile–butadiene–styrene chips to create easy-to-use sampling probes. We exemplify the suitability of this improved GPME approach in sampling chemical residues present on the skin, glass, and daily use objects. In these tests, the extracts were analyzed on a triple quadrupole mass spectrometer fitted with an electrospray ion source operated in the positive- and negative-ion modes. The method enabled the detection of diclofenac on excised porcine skin fragments exposed to a topical nonsteroidal anti-inflammatory drug and sweat residues (lactic acid) left on surfaces touched by humans. The limits of detection for diclofenac and lactic acid in hydrogel extract were 6.4 × 10–6 and 2.1 × 10–5 M, respectively. In a model experiment, conducted using the presented approach, the amount of lactic acid on a glass slide with fingerprints was estimated to be ∼1.4 × 10–7 mol cm–2.

Acrylic acid-chitosan blend hydrogel: a novel polymer adsorbent for adsorption of lead(II) and copper(II) ions from wastewater

Abstract Environmental pollution due to heavy metal contamination is a major environmental concern. A fully biodegradable and reusable adsorbent hydrogel for removal of heavy metal ions has been developed. The hydrogel was prepared from acrylic acid and chitosan using an irradiation method. The adsorbent was characterized using Fourier transform infrared analysis. Uptake of copper(II) and lead(II) at different contact times, pH, and metal ion concentrations was investigated by a batch method using atomic absorption spectroscopy. Kinetic adsorption data were studied using pseudo-first-order and pseudo-second-order equations. Experimental metal adsorption data were fitted with the Langmuir isotherm model. The maximum adsorption capacity of the hydrogel was found to be 192 and 171 mg/g for lead(II) and copper(II), respectively, from the Langmuir isotherm model. Reuse and desorption of the hydrogel were also successful. The adsorbent can be used to adsorb Cu(II) and Pb(II) by the column method with high removal efficiency. The data indicated that the designed hydrogel was environment friendly, regenerative, and can be used effectively for the removal of toxic heavy metal cations from wastewater for a sustainable environment.

Examination of Hydrogels and Mesenchymal Stem Cell Sources for Bioprinting of Artificial Osteogenic Tissues

Mesenchymal stem cells (MSCs) represent a very important cell source in the field of regenerative medicine and for bone and cartilage tissue engineering applications. Three-dimensional (3D) bioprinting has the potential to improve the classical tissue engineering concept as this technique allows the printing of cells with high spatial control of cell allocation within a 3D construct. In this study, we systematically compared different hydrogel blends for 3D bioprinting of MSCs by testing their cytocompatibility, ability to support osteogenic differentiation and their mechanical properties. In addition, we compared four different MSC populations isolated from different human tissues for their osteogenic differentiation capacity in combination with different hydrogels. The aim of this study was to identify the best MSC source and the most suitable hydrogel blend for extrusion-based bioprinting of 3D large-scaled osteogenic constructs. MSCs were isolated from different tissues (umbilical cord, adipose tissue, bone marrow). MSCs were seed onto or into different hydrogels and analyzed for cell viability, proliferation and osteogenic differentiation. In addition, viscoelastic properties of the hydrogels were determined. MSC-containing cubes with the size of 1 cm3 were printed by means of 3D extrusion-based bioprinting and analyzed by (immuno)histology for cell survival and production of a calcified extracellular matrix. Adipose tissue derived MSCs (ASCs) showed the highest osteogenic differentiation potential. A complex hydrogel blend consisting of fibrin, gelatin, hyaluronic acid, glycerol (F/G/H/Gl), tuned with hydroxyapatite, showed the best viscoelastic properties in combination with an excellent biocompatibility towards ASCs. This cell/hydrogel combination was used to bioprint 3D cubes. The cubes showed good mechanical stability and the printed ASCs were viable and able to calcify the hydrogel after bioprinting. The combination of the HA-tuned F/G/H/Gl hydrogel blend along with ASCs can be considered as a very promising bioink for 3D bioprinting of artificial bone tissue equivalents for prospective applications in tissue engineering and regenerative medicine.

Evaluation of cartilage regeneration of chondrocyte encapsulated gellan gum-based hyaluronic acid blended hydrogel

Hydrogels have shown to be advantageous in supporting damaged cartilage because of its analogous to the extracellular matrix (ECM) of cartilage tissue. However, problems such as infection and inflammation are still a challenge to be solved. In terms of tissue engineering, natural materials are more advantageous than synthetic materials in biocompatibility and biodegradability status. Herein, physically blended nature-derived gellan gum (GG) hydrogel and hyaluronic acid (HA) hydrogel is suggested as a one of solution for cartilage tissue engineering material. The purpose of this study is to determine the effect of GG/HA hydrogel in vitro and in vivo. The chemical and mechanical properties were measured to confirm the compatibility of hydrogels for cartilage tissue engineering. The viability, proliferation, morphology, and gene expression of chondrocytes encapsulated in hydrogels were examined in vitro. Furthermore, the beneficial effect of the blended hydrogel was confirmed by performing the in vivo experiment. The chemical properties of hydrogels confirmed the well physically blended hydrogels. The mechanical studies of hydrogels displayed that as the content of HA increases, the swelling ratio was higher, compressive strength decreased and degradation was faster. Therefore, to use the hydrogel of GG and HA network, the proper amount must be blended. The in vitro study of chondrocytes encapsulated GG/HA hydrogel showed that the proper amount of HA enhanced the cell growth, attachment, and gene expression. The in vivo examination verified the advantageous effect of GG/HA hydrogel. Overall results demonstrate that GG/HA hydrogel is suitable for culturing chondrocyte and can be further applied for the treatment of cartilage defects.

Extrusion-based 3D printing of photo-crosslinkable gelatin and κ-carrageenan hydrogel blends for adipose tissue regeneration

Current soft tissue repair techniques for women with breast cancer remain associated with several drawbacks including surgical complications and a high resorption rate for lipofilling techniques. Hence, the need to develop improved adipose tissue reconstruction strategies. Additive manufacturing can be a promising tool towards the development of patient-specific scaffolds which are able to support adipose tissue engineering. In the present work, scaffolds composed of both methacrylamide-modified gelatin (Gel-MA) and methacrylated κ-carrageenan (Car-MA), i.e. hydrogel blends, were developed using extrusion-based 3D printing in order to establish a close resemblance to the native extracellular matrix. The hydrogel blends were benchmarked to scaffolds constituting of only Gel-MA. Our results indicate that both types of scaffolds remain stable over time (21 days), are able to absorb large amounts of water and exhibit mechanical properties comparable to those of native breast tissue (2 kPa). Furthermore, a similar cell viability (> 90%) and proliferation rate after 14 days was obtained for adipose tissue-derived stem cells (ASCs) upon seeding onto both types of scaffolds. Additionally, the ASCs were able to differentiate into the adipogenic lineage on the hydrogel blend scaffolds, although their differentiation potential was lower compared to that of ASCs seeded onto the Gel-MA scaffolds.

Customized tracheal design using 3D printing of a polymer hydrogel: influence of UV laser cross-linking on mechanical properties

BackgroundThe use of 3D printing of hydrogels as a cell support in bio-printing of cartilage, organs and tissue has attracted much research interest. For cartilage applications, hydrogels as soft materials must show some degree of rigidity, which can be achieved by photo- or chemical polymerization. In this work, we combined chemical and UV laser polymeric cross-linkage to control the mechanical properties of 3D printed hydrogel blends. Since there are few studies on UV laser cross-linking combined with 3D printing of hydrogels, the work here reported offered many challenges.MethodsPolyethylene glycol diacrylate (PEGDA), sodium alginate (SA) and calcium sulphate (CaSO4) polymer paste containing riboflavin (vitamin B2) and triethanolamine (TEOHA) as a biocompatible photoinitiator was printed in an extrusion 3D plotter using a coupled UV laser. The influence of the laser power on the mechanical properties of the printed samples was then examined in unconfined compression stress-strain tests of 1 × 1 × 1 cm3 sized samples. To evaluate the adhesion of the material between printed layers, compression measurements were performed along the parallel and perpendicular directions to the printing lines.ResultsAt a laser density of 70 mW/cm2, Young’s modulus was approximately 6 MPa up to a maximum compression of 20% in the elastic regime for both the parallel and perpendicular measurements. These values were within the range of biological cartilage values. Cytotoxicity tests performed with Vero cells confirmed the cytocompatibility.ConclusionsWe printed a partial tracheal model using optimized printing conditions and proved that the materials and methods developed may be useful for printing of organ models to support surgery or even to produce customized tracheal implants, after further optimization.

In-situ mineralization of calcium carbonate in pectin based edible hydrogel for the delivery of protein at colon

Protein administration through oral route remains to be an attractive strategy due to lesser pain, greater convenience and increased patient compliance, thus promoting its pharmaceutical research. Oral delivery, however, suffers from high susceptibility to digestive enzymes in the gastrointestinal tract. Hence, developing colon-specific protein delivery systems, especially with high bioavailability, becomes essential. In this study, calcium carbonate microparticles were in-situ mineralized in pectin/poly(ethylene glycol) (PEG) hydrogel blend to protect and release protein drug at the colon site. Further, bovine serum albumin (BSA) as a model drug was loaded during the fabrication of pectin/PEG blend containing in-situ mineralized calcium carbonate particles. The interaction of loaded BSA with calcium carbonate by physical forces was evidenced by FTIR analysis. BSA could also be visualized around the mineralized calcium carbonate by TEM throughout the hydrogel matrix. Rheological studies on the oral delivery vehicle revealed dynamic nature of the hydrogel, an essential property required for drug carriers for its interaction with the target site. In-vitro swelling and protein release studies of pectin based hydrogel indicated the potentiality of the drug carrier in releasing protein at the colon site. The conformational stability of the released BSA from the hydrogel blend (PPCB) was confirmed by SDS-PAGE and CD spectropolarimetry.

Blended alginate/collagen hydrogels promote neurogenesis and neuronal maturation.

Brain extracellular matrix (ECM) is complex, heterogeneous and often poorly replicated in traditional 2D cell culture systems. The development of more physiologically relevant 3D cell models capable of emulating the native ECM is of paramount importance for the study of human induced pluripotent stem cell (iPSC)-derived neurons. Due to its structural similarity with hyaluronic acid, a primary component of brain ECM, alginate is a potential biomaterial for 3D cell culture systems. However, a lack of cell adhesion motifs within the chemical structure of alginate has limited its application in neural culture systems. This study presents a simple and accessible method of incorporating collagen fibrils into an alginate hydrogel by physical mixing and controlled gelation under physiological conditions and tests the hypothesis that such a substrate could influence the behaviour of human neurons in 3D culture. Regulation of the gelation process enabled the penetration of collagen fibrils throughout the hydrogel structure as demonstrated by transmission electron microscopy. Encapsulated human iPSC-derived neurons adhered to the blended hydrogel as evidenced by the increased expression of α1, α2 and β1 integrins. Furthermore, immunofluorescence microscopy revealed that encapsulated neurons formed complex neural networks and matured into branched neurons expressing synaptophysin, a key protein involved in neurotransmission, along the neurites. Mechanical tuning of the hydrogel stiffness by modulation of the alginate ionic crosslinker concentration also influenced neuron-specific gene expression. In conclusion, we have shown that by tuning the physicochemical properties of the alginate/collagen blend it is possible to create different ECM-like microenvironments where complex mechanisms underpinning the growth and development of human neurons can be simulated and systematically investigated.

Nonmulberry silk protein sericin blend hydrogels for skin tissue regeneration - in vitro and in vivo

The damage to the skin is most prominent and evident as it is our first line of defense and unremittingly under attack by biological and environmental factors. The restoration of the skin is dependent on the extent of the injury. To explore the prospects of new biomimetic material, bi-layered skin construct is fabricated in vitro with nonmulberry silk protein sericin and chitosan hydrogels using human dermal fibroblasts and keratinocytes. The in vitro analysis of the hydrogels showed enhanced adhesion, proliferation, and migration of skin cells with coordinated interaction amongst themselves leading to the synthesis of collagen IV and matrix metalloproteinase (MMP2 and MMP9). The in vivo evaluation indicates the regeneration of skin with densely packed collagen and formation of matured blood vessels in the animals implanted with sericin containing hydrogels. Moreover, the local and systemic immune response determined in vivo exhibits the biosafety of sericin based hydrogels. In addition, the cross-sectional analysis of the implanted hydrogels displays infiltration of the skin tissue cells into the hydrogels marking their biocompatibility and non-toxicity. The cumulative analysis of the in vitro and in vivo observations demonstrates that the sericin based hydrogels are non-inflammatory, supports the regeneration and repair of the skin tissue.

Pectin/PEG food grade hydrogel blend for the targeted oral co-delivery of nutrients

Food grade oral delivery vehicles for the targeted delivery of nutrients are currently fabricated by adapting pharmaceutical approaches to promote human health. In this study, Ca2+ with vitamin D / Fe2+ with vitamin C were entrapped in edible pectin/PEG polymer blend matrix to obtain hydrogels namely PPCaD and PPFeC. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) analysis of pectin based hydrogels confirmed the existence of metal ion content in the hydrogel matrix and their corresponding interaction with the pectin matrix through electrostatic and hydrogen bonding. Rheological measurements revealed a higher elastic nature of PPCaD compared to PPFeC and were in good agreement with the swelling studies. In-vitro release studies concluded that the lowest release of metal ion and vitamin from the corresponding hydrogel samples in simulated gastric fluid (SGF) was observed at pH 1.2 for 3 h. It indicated that protection of nutrients from the gastric environment was conferred by the hydrogels. The release studies carried out in the next 3 h in simulated intestinal fluid (SIF) at pH 6.8 indicated not only the highest swelling of the hydrogel samples but also the highest co-release of nutrients at the intestinal site.

Development of potentially biocompatible hydrogels with cylindrical pores prepared from polyvinyl alcohol and low‐molecular weight polyacrylic acid

In the present work, blend hydrogels from PVA and two different low PAA molecular weights, Mw 1800 g/mol and 5000 g/mol were prepared through the freezing thawing (F‐T) physical crosslinking method. The obtained materials were fully characterized by means of scanning electron microscopy (SEM) in order to analyze their morphology, gel fraction (GF) to determine the crosslinking degree and Fourier transformed infrared spectroscopy (FTIR) to analyze the PVA‐PAA interactions. Thermal characterizations [thermogravimetric analysis (TGA) and dynamic scanning calorimetry (DSC)] were conducted to study the relevant thermal characteristics. Sorption tests at different pH values (4 and 7) obtained from different aqueous systems were also inquired. The effects of PAA contents (between 1 and 5 wt%) and Mw of the used PAA on the hydrogel final properties were analyzed and related to the most probably PVA‐PAA interactions. POLYM. ENG. SCI., 59:1479–1488 2019. © 2019 Society of Plastics Engineers

Evaluation of Cartilage Regeneration in Gellan Gum/agar Blended Hydrogel with Improved Injectability

Gellan gum is known to be one of the biocompatible materials that resemble living tissues, continuously delivering stem cells or general cells, and filling voids in the wound. In spite of the many advantages of gellan gum, it has difficulty in the application by inserting the scaffolds into the body. In order to generalize gellan gum for medical purpose, it is necessary to increase the injectability of gellan gum. In this study, gellan gum solutions with 0.2, 0.4, 0.6, 0.8 wt% of agar were prepared. The obtained hydrogels were tested for rheological properties and chondrocytes adhesion, morphology and proliferation. Results showed that the addition of agar, in the starting GG solution, allows extruding the material producing micro-porous scaffolds. The biological evaluation demonstrated that the adhesion and proliferation of chondrocytes increase with the presence of agar in the final structure. The solutions composed of GG and agar represent an efficient, fast and high reproducible methodology with the potential to be used as an injectable hydrogel for cartilage regeneration purposes.

Polyurethane/poly(vinyl alcohol) hydrogels: Preparation, characterization and drug delivery

Polyurethane based hydrogels were successfully prepared by freezing–thawing method of polyurethane (PU)/poly(vinyl alcohol) (PVA) mixtures in aqueous solution. The new materials were characterized by ATR-FTIR and SEM, confirming that the PU/PVA blend hydrogels form a network structure through hydrogen bonds and hydrophobic interactions. According to SEM analysis, an increase in the surface pore numbers and size was observed with increasing the polyurethane amount into the hydrogels. The average diameter of the pores was estimated as being between 4.05 and 39.05 µm. The PU/PVA blend hydrogels showed a lower tensile strength than pure PVA hydrogel, due to the extent of hydrogen bonding occurrence during the freezing–thawing process which determines a variation of porosity. The highest value of water swelling (1675%) was obtained for the hydrogel blend containing 50% PU, whereas pure PVA showed much lower ability for water (640%). These results can be explained by a denser structure of PVA network formed by applying successive freezing–thawing cycles. Three steps of water swelling were evidenced for the PU/PVA blend hydrogels: a fast one, a slow one and an equilibrium phase. In vitro technique was used for release of neomycin sulphate into a biological media model. The present investigations of the new PU/PVA blend hydrogels indicate their possible application as matrices for drug delivery.

Redox-responsive blend hydrogel films based on carboxymethyl cellulose/chitosan microspheres as dual delivery carrier

A simple method to fabricate redox-responsive composite hydrogel films via incorporating chitosan (CS) microspheres into carboxymethyl cellulose (CMC) hydrogel using a di-sulphide cross-linker cystamine dihydrochloride (CYS) have done in this paper. Dual drugs, an anticancer, 5-Fluorouracil (5-FU) and an antibiotic, Tetracycline Hydrochloride (TH) were used as model drugs. The prepared composite hydrogel films were characterized using FTIR, SEM, rheology measurement, mechanical and swelling tests. Our results showed that the well dispersed spherical CS microspheres endowed hydrogel film increased mechanical properties and swellability. In vitro drug release displayed an accelerated release under weak acidic or reducing media. The in vitro cytotoxicity and cell apoptosis studies showed the drug-loaded composite film caused enhanced inhibition to HepG2 cells in presence of glutathione (GSH). Moreover, the film has exhibited excellent antimicrobial efficacy against E.coli and Staphylococcus aureus. Therefore, our simple and effective dual drug-loaded system has the potential to be used for cancer therapy in the future.

Controlled Release Behaviors of Tribenuron Methyl Herbicide and Potassium Nitrate Fertilizer from Natural Polymer Blended Poly(Vinyl Alcohol) Hydrogel Microspheres

Polyvinyl Alcohol (PVA) hydrogel microspheres for controlled release of fertilizer (KNO3) and Tribenuron Methyl Herbicide (TBM) were prepared by blending the naturally occurring Alginate (AL) and Pectin (PE). The cross-linking in PVA hydrogel microspheres was carried out by varying the amount of glutaraldehyde from 0.5-1.0 wt%. To control the loading and release properties of PVA hydrogel microspheres, a small amount of NaCl (0.2 wt%) was also added in formulation of microspheres. The blending of PE and AL in PVA hydrogel microspheres was confirmed with FT-IR spectra and by increased thermal stability PVA hydrogel as determined by Differential Scanning Calorimetry (DSC) and Thermogravimetric (TGA) analysis. The PVA hydrogel microspheres were characterized for degree of swelling and for loading and cumulative release of fertilizer (KNO3) and herbicide (TBM), which were carried out in solutions of different pH and at different temperatures. The Scanning Electron Micrographs (SEM) of PVA hydrogel microspheres were recorded before and after the release of loaded agrochemicals and used to confirm the shape and homogeneous blending of PE/AL in PVA hydrogels. The enhanced brittle morphology form SEM images of PVA hydrogel microspheres after the release of loaded agrochemicals has suggested the controlled release of agrochemicals through a mechanism of degradation of polymer chains. Thus natural polymer blended PVA hydrogel microspheres are found to be a potential candidate for the formulation of controlled release systems for the application of agrochemicals in soils and to overcome the environmental problem, which usually encountered on applications of fertilizers and herbicides in agricultural fields by conventional methods.

Surface modification by deposition of IPA plasma and gellan gum/chitosan hybrid hydrogel onto thermoplastic polyurethane for controlled release of N‐acetylcysteine

A thin film system composed of gellan gum and chitosan was fabricated through a combination of polyelectrolyte blend and hybrid hydrogel gelation for controlled release of drug. In this study, precursor isopropyl alcohol (IPA) was used to plasma deposit on the surface of thermoplastic polyurethane (TPU) to form a hydrophilic film. The features of the thin film were evaluated using water contact angle (WCA) measurement, scanning electron microscopy (SEM), Fourier transform infra‐red (FTIR), UV/Vis spectroscopy, and studies of controlled release of drugs. The hybrid hydrogel, pH‐sensitive, was tested at pH values of 1.2 and 7.4 of buffer solution and at a temperature of 37°C to observe its swelling ratio and drug delivery properties with N‐acetylcysteine as a drug material for controlled release. Furthermore, at pH 7.4, the hybrid hydrogel has an outstanding release ratio of up to about 90% absorption amounts of N‐acetylcysteine after 8 hr. The mechanism of drug release from thin film devices (n = 0.684) is anomalous (non‐Fickian) transport, the value of n lies between 0.43 and 0.85.

Evaluation of polyvinyl alcohol\u2013borax/agarose (PVA\u2013B/AG) blend hydrogels for removal of deteriorated consolidants from ancient Egyptian wall paintings

This study concerns the assessment of a new polyvinyl alcohol–borax/agarose blend hydrogel (PVA–B/AG) tailored for the conservation of ancient Egyptian wall paintings. The increasing problems of deteriorated consolidants affecting ancient wall paintings have attracted the interest of conservation scientists in the last 20 years. The ability of a new blend for removing aged Paraloid® B-72 layers from painted stone and plaster samples has been evaluated. The hydrogel blend was used to expose the aged Paraloid in a controlled manner to six different cleaning system (CS). CS1–CS4 consist of solvents or solvent mixtures; CS5 and CS6 are nanostructured fluids (NSFs). The evaluation of the removal process was carried out by quantitative and qualitative methods, namely, visual examination, 3D microscopy, contact angle and colorimetric measurements and by Fourier transform infra-red spectrometry in reflectance mode. The results showed that the PVA–B/AG blend hydrogel, loaded with specific cleaning systems, was able to remove deteriorated B-72 and allowed to restore the painted surface to a state close to the original one. The PVA–B/AG blend showed good workability, permitting it to be easily cut, shaped, applied and removed. It could also be verified by means of different investigation methods that the blend left no detectable residues. As a final realistic check of the method, the PVA–B/AG hydrogel loaded with the best functioning cleaning system (CS3) was used to remove an aged consolidant layer from an ancient Egyptian wall painting.

Islet Plotting: 3D Bioprinting of Functional Islets of Langerhans in an Alginate/Methylcellulose Hydrogel Blend (Adv. Healthcare Mater. 7/2019)

Islet Plotting: 3D Bioprinting of Functional Islets of Langerhans in an Alginate/Methylcellulose Hydrogel Blend (Adv. Healthcare Mater. 7/2019)