High Gel Fraction Research Articles

Hydrogel Containing Propolis: Physical Characterization and Evaluation of Biological Activities for Potential Use in the Treatment of Skin Lesions.

Skin injury affects the integrity of the skin structure and induces the wound healing process, which is defined by a well-coordinated series of cellular and molecular reactions that aim to recover or replace the injured tissue. Hydrogels are a group of promising biomaterials that are able to incorporate active ingredients for use as dressings. This study aimed to synthesize hydrogels with and without propolis extract and evaluate their physical characteristics and biological activities in vitro for potential use as active dressings in the treatment of skin lesions. The antifungal [Candida albicans (C. albicans) and Candida tropicalis (C. tropicalis)] and antibacterial [Staphylococcus aureus (S. aureus), Pseudomonas aeruginosas (P. aeruginosas) and Escherichia coli (E. coli)] activity was assessed by the microdilution method in plates and antioxidant potential by the reduction of the phosphomolybdate complex. The hydrogels showed good water absorption capacity, high solubility, and high gel fraction, as well as good porosity, water retention, and vapor transmission rates. They revealed a totally amorphous structure. The extract and the hydrogels containing the propolis extract (1.0% and 2.5%) did not inhibit fungal growth. However, they showed antibacterial activity against strains of S. aureus and P. aeruginosas. Regarding the E. coli strain, only the extract inhibited its growth. It showed good antioxidant activity by the evaluation method used. Therefore, the hydrogels containing propolis extract can be a promising alternative with antibacterial and antioxidant action for use as dressings for the treatment of skin lesions.

The Influence of the Structural Architecture on the Swelling Kinetics and the Network Behavior of Sodium-Alginate-Based Hydrogels Cross-Linked with Ionizing Radiation.

The present work discusses the influence of the structural architecture of sodium alginate-co-acrylic acid-poly(ethylene) oxide hydrogels, crosslinked through electron beam (e-beam) radiation processing. The most important properties of the hydrogels were studied in detail to identify a correlation between the architecture of the hydrogels and their properties. Furthermore, the effect of sodium alginate (NaAlg) concentration, the amounts of the polymer blend, and the size of the samples on hydrogel properties were investigated. The results show that the hydrogels cross-linked (0.5% and 1% NaAlg) with 12.5 kGy exhibit improved physicochemical properties. High gel fraction levels (exceeding 83.5-93.7%) were achieved. Smaller hydrogel diameter (7 mm) contributed to a maximum swelling rate and degree of 20.440%. The hydrogel network was dependent on the hydrogels' diameter and the amount of polymer blend used. The hydrogels best suited the first-order rate constants and exhibited a non-Fickian diffusion character with diffusion exponent values greater than 0.5. This study indicates that the cross-linked hydrogel has good properties, particularly because of its high degree of swelling and extensive stability (more than 180 h) in water. These findings show that hydrogels can be effectively applied to the purification of water contaminated with metals, dyes, or even pharmaceuticals, as well as materials with a gradual release of bioactive chemicals and water retention.

Closed-loop circular economy in ‘upcycled’ acrylonitrile–butadiene–styrene vitrimer

Today, the issue of plastic waste pollution has reached unprecedented levels. The increasing production of plastics, combined with a decreasing rate of recycling, has significantly worsened this problem in recent years. While a wide range of plastics are manufactured, thermoplastics are a type that can be recycled relatively easily. However, recycled thermoplastics often have lower mechanical properties compared to new ones. Considering this challenge, making thermoplastics recyclable could revolutionize the recycling process and represent a major advancement towards establishing a circular economy for plastics. In this study, virgin acrylonitrile–butadiene–styrene (ABS) was transformed into a vitrimer through reactive melt extrusion using a bio-derived crosslinker containing dynamic imine linkages. This crosslinker results in a dynamic network, in the melt, as observed from the higher gel fraction and imparts recyclability to the resulting ABS vitrimer, which exhibits higher yield strength (by 15 %) and Young’s modulus (by 19 %). Remarkably, the mechanical and thermal properties of the vitrimer remain largely unchanged even after undergoing five cycles of reprocessing. In addition, the resulting vitrimer is dimensionally stable as inferred from creep studies and shows rapid stress relaxation at higher temperature following Arrhenius behaviour. The electron paramagnetic resonance (EPR) spectra were captured at room temperature for both ABS and its vitrimer. The difference in singlet band intensities in the spectra begins to suggest that the vitrimer is more stable post multiple recycling. While this research focused on virgin ABS, the approach outlined in the study has the potential to be applied to post-consumer recycled (PCR) ABS. This could introduce recyclability to PCR ABS and pave the way for a closed-loop circular economy for ABS plastics.

Bioinspired H-bond cross-linking of nanostructured gelatine by inorganic goethite α-FeOOH

This paper reports the effect of goethite nanowire filler on hydrogen (H) linking in gelatine. Nanostructured gelatine that would otherwise be soluble becomes insoluble in water at room temperature if goethite nanowire filler is added. The experimental results reveal a significant increase in the gel fraction of the composite with 6 vol% α-iron (III) oxide-hydroxide (α-FeOOH) additive, reaching over 73% after being kept in water, compared with that of pristine gelatine, with a mere 13% gel fraction. In the presented composite, the solubility of gelatine can also be controlled by visible light, as absorption in the narrow-band-gap α-iron (III) oxide-hydroxide results in local heating of nanowires. The illuminated 6 vol% α-iron (III) oxide-hydroxide/gelatine composite shows a gel fraction of 13.4%, while the control sample kept in the dark exhibits a high gel fraction value of 73.8%. The observed remotely switchable disintegration of gelatine by visible light presents a feature that can be used in designing temporary tissue engineering and drug delivery substrates.

Synthesis of polyethylene-based covalent adaptable networks including 1,2,3-triazolium or imine dynamic cross-links by reactive processing

Polyethylene-based covalent adaptable networks (PE CANs) are obtained by reactive extrusion in a micro-compounder of a commercial maleic anhydride-grafted polyethylene (PE-g-MA) with two tailor-made α,ω-diamine cross-linkers carrying either imine or 1,2,3-triazolium groups as dissociative covalent dynamic bonds. Depending on the chemical nature of the exchangeable bonds, drastically different properties are demonstrated by FTIR, swelling/extractible, reactive dissolution and rheological experiments. The imine-containing PE CAN yields a high gel fraction but rheology and reactive dissolution experiments demonstrate the lack of dynamicity due to side-reactions promoting the formation of non-dynamic covalent cross-links. Such undesirable reaction occurs already during the processing stage from the premature cleavage of the imine bonds into amines, and further formation of permanent imide cross-links by reaction with pendent maleic anhydrides. Conversely, the 1,2,3-triazolium-containing PE CAN presents a lower gel fraction but exhibits viscoelastic properties typical of dissociative CANs. While this material is easily reprocessable by compression moulding, the evolution of the rheological properties at high temperatures (160–200 °C) points toward the occurrence of side reactions slowing down the relaxation dynamics which we attribute to the chemical rearrangement of the 1,2,3-triazolium cross-links. These two examples illustrate the difficulty of using amine-functionalized dynamic cross-links in the synthesis of PE CANs by reactive extrusion using PE-g-MA.

Enhancement of Poly(vinyl alcohol) Hydrogel Properties by N-Succinyl Chitosan and Mesona chinensis Extract for Use as Wound Dressings

Hydrogels composed of different ratios of poly(vinyl alcohol), N-succinyl chitosan (NSC), and Mesona chinensis extract, for use as a wound dressing, were synthesized via thermal polymerization. Potassium persulfate was chosen as the initiator and glutaraldehyde as the crosslinking agent. NSC was prepared by modification of chitosan with succinic anhydride. It was found that this preparation method gave a high gel fraction percentage. The structures of the prepared hydrogels were characterized by Fourier-transform infrared spectroscopy, and their morphology by scanning electron microscopy (SEM). In addition, water transport properties, mechanical properties and cytotoxicity were also studied. The SEM results show that the hydrogels exhibited porous structures and that pore size and size distribution increased with increasing NSC content. Hydrogel-water interactions and water transport properties were also studied in terms of swelling ratio, equilibrium water retention, and water vapour transmission rate. These showed an increase, from 637 to 1240 %, 17.8 to 21.4 %, and 110 to 121 g h−1 m−2 respectively with an increase in NSC content. These gels exhibit a lower water vapour transmission rate compared to that of second and third degree burns but higher than normal skin. Similarly, NSC improved the mechanical properties, presented in terms of stress and percentage strain, of the hydrogels. The stress, percentage strain, and Young’s modulus were found to increase from 15 to 32 kPa, 197 to 294 %, and 0.078 to 0.133 kPa respectively. The hydrogels can be considered to be non-toxic based on the in vitro cytotoxicity assay results. In conclusion, the results showed that, by varying composition, hydrogel properties can be tuned to the specific requirements of an ideal wound dressing.

Reconstructing Curves: A Bottom-Up Approach toward Adipose Tissue Regeneration with Recombinant Biomaterials.

The potential of recombinant materials in the field of adipose tissue engineering (ATE) is investigated using a bottom-up tissue engineering (TE) approach. This study explores the synthesis of different photo-crosslinkable gelatin derivatives, including both natural and recombinant materials, with a particular emphasis on chain growth and step growth polymerization. Gelatin type B (Gel-B) and a recombinant collagen peptide (RCPhC1) are used as starting materials. The gel fraction and mass swelling properties of 2D hydrogel films are evaluated, revealing high gel fractions exceeding 94% and high mass swelling ratios >15. In vitro experiments with encapsulated adipose-derived stem cells (ASCs) indicate viable cells (>85%) throughout the experiment with the RCPhC1-based hydrogels showing a higher number of stretched ASCs. Triglyceride assays show the enhanced differentiation potential of RCPhC1 materials. Moreover, the secretome analysis reveal the production of adipose tissue-specific proteins including adiponectin, adipsin, lipocalin-2/NGAL, and PAL-1. RCPhC1-based materials exhibit higher levels of adiponectin and adipsin production, indicating successful differentiation into the adipogenic lineage. Overall, this study highlights the potential of recombinant materials for ATE applications, providing insights into their physico-chemical properties, mechanical strength, and cellular interactions.

Controlling the Porosity of Starch Hydrogels with Poly(Methyl Methacrylate) (PMMA) Beads

AbstractStarch is a natural, biodegradable polymer that can be used to prepare hydrogels with various applications in food, pharmacy, medicine, agriculture, etc. In this study, a method of preparation using poly(methyl methacrylate) (PMMA) beads to control the porosity of starch hydrogels is proposed. The hydrogels are crosslinked with trisodium trimetaphosphate and dried in a vacuum oven. Results show that increasing the amount of PMMA beads result in higher porosity hydrogels ranging from ≈35% for hydrogels where no PMMA beads are used to ≈88% for hydrogels where the mass ratio of PMMA beads to starch is 10:1. Higher porosity hydrogels have a higher equilibrium water content and swelling degree, but lower mechanical properties. All hydrogels have a low solubility (<≈5%) and a high gel fraction (>≈90%) percentage. Upon degradation in α‐amylase at 37 °C, low porosity hydrogels (prepare with 0:1 and 1:10 PMMA beads:starch) degrade within 30 min, while high porosity hydrogels (prepare with 1:1 and 10:1 PMMA beads:starch) degrade within 3 weeks. The release of a dye that is incorporated into the hydrogel walls follows similar kinetics. Therefore, the use of PMMA beads is an efficient method to control starch hydrogel's porosity and properties.

Synthesis and Characterization of Poly(glycerol sebacate), Poly(glycerol succinate) and Poly(glycerol sebacate-co-succinate)

In recent years, thermoset elastomers, particularly polyesters derived from the polycondensation of glycerol and non-toxic diacids, have garnered significant interest. This study focuses on the synthesis of poly(glycerol-co-diacids) polymers using varying molar ratios of glycerol (G), sebacic acid (S), and succinic acid (Su). Seven distinct ratios were investigated (PGS (1:1), PGSSu (1:0.9:0.1), PGSSu (1:0.8:0.2), PGSSu (1:0.5:0.5), PGSSu (1:0.2:0.8), PGSSu (1:0.1:0.9) and PGSu (1:1)). The resulting polymers were analyzed using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic mechanical analyses (DMA), tensile tests, scanning electron microscopy (SEM), gel fraction and degree of swelling determination. Among the synthesized polymers, PGS (1:1) and PGSu (1:1) exhibited superior mechanical robustness than the polymers obtained by mixing diacids. The results show that the incorporation of succinic acid in the synthesis of the polymers progressively led to rougher surfaces and a reduction in thermal resistance compared to PGS (1:1). PGSu (1:1) showed the highest surface roughness and the lowest thermal resistance. The glass transition temperature (Tg) for these elastomers ranged from − 30 °C to 30 °C. Additionally, higher ratios of succinic acid led to increased polymer density and less degree of swelling. The gel fraction of these polymers ranged from 70 to 95%. PGS (1:1) with the lowest and PGSu (1:1) with the highest gel fraction, respectively.Graphical

Renewable whey-based hydrogel with polysaccharides and polyvinyl alcohol as a soil amendment for sustainable agricultural application

This work describes the preparation of a novel biopolymer hydrogel based on acid whey, cellulose derivatives and polyvinyl alcohol (PVA). The hydrogel was prepared and characterized with the aim of producing an environmentally-friendly soil amendment to increase water retention capacity of the soil. The findings showed considerable swelling properties of the hydrogels depending on the PVA content and crosslinking density. The samples with PVA in a concentration 2.5 % and 5 % were more rigid, the gel fraction increased with a subsequently decrease in their swelling capacity. The hydrogels crosslinked with 15 % of citric acid demonstrated a constant swelling ratio (SR) of around 500 % within 10 swelling/drying cycles. The hydrogels crosslinked with 10 % citric acid and supplemented with 1 % of PVA showed SR of 1000–1400 % caused by less crosslinked polymer network and increased pore volume for water uptake. It was found that hydrogel with a higher gel fraction had a stable structure. Supplementing PVA at 5 % extended the period of decomposition of the hydrogel material by almost 60 % in the soil environment and soil humidity was maintained for longer. Applying 2 % of the hydrogel 5PVA to soil increased the water retention capacity by 19 %.

Xanthan-Gum/Pluronic-F-127-Based-Drug-Loaded Polymeric Hydrogels Synthesized by Free Radical Polymerization Technique for Management of Attention-Deficit/Hyperactivity Disorder.

Smart and intelligent xanthan gum/pluronic F-127 hydrogels were fabricated for the controlled delivery of atomoxetine HCl. Different parameters such as DSC, TGA, FTIR, XRD, SEM, drug loading, porosity, swelling index, drug release, and kinetics modeling were appraised for the prepared matrices of hydrogels. FTIR confirmed the successful synthesis of the hydrogel, while TGA and DSC analysis indicated that the thermal stability of the reagents was improved after the polymerization technique. SEM revealed the hard surface of the hydrogel, while XRD indicated a reduction in crystallinity of the reagents. High gel fraction was achieved with high incorporated contents of the polymers and the monomer. An increase in porosity, drug loading, swelling, and drug release was observed with the increase in the concentrations of xanthan gum and acrylic acid, whereas Pluronic F-127 showed the opposite effect. A negligible swelling index was shown at pH 1.2 and 4.6 while greater swelling was observed at pH 7.4, indicating a pH-responsive nature of the designed hydrogels. Furthermore, a higher drug release was found at pH 7.4 compared to pH 1.2 and 4.6, respectively. The first kinetics order was followed by the prepared hydrogel formulations. Thus, it is signified from the discussion that smart xanthan gum/pluronic F-127 hydrogels have the potential to control the release of the atomoxetine HCl in the colon for an extended period of time.

Synthesis and Evaluation of Alginate-Based Nanogels as Sustained Drug Carriers for Caffeine.

The objective of this study is to design a polymeric network of nanogels for sustained release of caffeine. Therefore, alginate-based nanogels were fabricated by a free-radical polymerization technique for the sustained delivery of caffeine. Polymer alginate was crosslinked with monomer 2-acrylamido-2-methylpropanesulfonic acid by crosslinker N',N'-methylene bisacrylamide. The prepared nanogels were subjected to sol-gel fraction, polymer volume fraction, swelling, drug loading, and drug release studies. A high gel fraction was seen with the increasing feed ratio of polymer, monomer, and crosslinker. Greater swelling and drug release were observed at pH 4.6 and 7.4 as compared to pH 1.2 due to the deprotonation and protonation of functional groups of alginate and 2-acrylamido-2-methylpropanesulfonic acid. An increase was observed in swelling, loading, and release of the drug with the incorporation of a high feed ratio of polymer and monomer, while a reduction was seen with the increase in crosslinker feed ratio. Similarly, an HET-CAM test was used to evaluate the safety of the prepared nanogels, which showed that the prepared nanogels have no toxic effect on the chorioallantoic membrane of fertilized chicken eggs. Similarly, different characterizations techniques such as FTIR, DSC, SEM, and particle size analysis were carried out to determine the development, thermal stability, surface morphology, and particle size of the synthesized nanogels, respectively. Thus, we can conclude that the prepared nanogels can be used as a suitable agent for the sustained release of caffeine.

Fine-Tuning the Endcap Chemistry of Acrylated Poly(Ethylene Glycol)-Based Hydrogels for Efficient Burn Wound Exudate Management.

Most commercial dressings with moderate to high exudate uptake capacities are mechanically weaker and/or require a secondary dressing. The current research article focuses on the development of hydrogel-based wound dressings combining mechanical strength with high exudate absorption capacities using acrylate-endcapped urethane-based precursors (AUPs). AUPs with varying poly(ethylene glycol) backbone molar masses (10 and 20kg mol-1 ) and endcap chemistries are successfully synthesized in toluene, subsequently processed into UV-cured hydrogel sheets and are benchmarked against several commercial wound dressings (Hydrosorb, Kaltostat, and Mepilex Ag). The AUP materials show high gel fractions (>90%) together with strong swelling degrees in water, phosphate buffered saline and simulated wound fluid (12.7-19.6g g-1 ), as well as tunable mechanical properties (e.g., Young's modulus: 0.026-0.061MPa). The AUPs have significantly (p < 0.05) higher swelling degrees than the tested commercial dressings, while also being mechanically resistant. The elasticity of the synthesized materials leads to an increased resistance against fatigue. The di- and hexa-acrylated AUPs show excellent in vitro biocompatibility against human foreskin fibroblasts, as evidenced by indirect MTS assays and live/dead cell assays. In conclusion, the processed AUP materials demonstrate high potential for wound healing application and can even compete with commercially available dressings.

Soft Elastomers Based on the Epoxy–Amine Chemistry and Their Use for the Design of Adsorbent Amphiphilic Magnetic Nanocomposites

Poly(ethylene glycol) (PEG)-based soft elastomers, bearing tertiary amine and hydroxyl groups, were synthesized in bulk from the epoxy–amine reaction between poly(ethylene glycol) diglycidyl ether (PEGDE) and a poly(etherdiamine), Jeffamine ED600. High gel fractions (≥0.95) and low glass transition temperatures (Tg ≈ −50 °C) were attained after complete curing of the systems in bulk. The amphiphilicity of the network allowed the swelling of the materials in both aqueous solutions and a variety of organic solvents. Magnetic nanocomposites were synthesized by in situ coprecipitation of magnetic nanoparticles (MNPs) in the elastomeric matrix. The obtained materials were processed by cryogenic milling to obtain powders that were tested as potential magnetic adsorbents and that showed a fast and strong response to the action of a permanent magnet. These materials showed removal rates of at least 50% in 10 min when used in the adsorption of Cu+2 ions from an aqueous solution, making them interesting candidates for the design of magnetically separable metal ion adsorbents.

Construction of ion bonds in gel-free polydiene-based ionomers without compromising molecular weight

Rubber-based ionomers have attracted extensive research interest from academy and industry attributing to their distinct physical mechanical properties. However, currently reported approaches to performing polar modification on common tire rubber (such as natural rubber and butadiene rubber) typically demonstrate high gel fraction or low molecular weight. Herein, we prepared a gel-free rubber-based ionomer by the first epoxidation to elastomeric polymers and subsequent olefin metathesis reaction, which showed no degradation of molecular weight. Meanwhile, to investigate the reaction mechanism of epoxidation and olefin metathesis, high vinyl polybutadiene rubber (HVBR) with multi-site reactive units was used as the matrix. Experimental results showed that the incorporation of epoxy groups could effectively reduce the degradation of HVBR matrix caused by the olefin metathesis. The formation of multiple ion pair and ion cluster structures could significantly enhance the mechanical strength and damping properties of HVBR-based ionomers. And the dynamic measurements indicated that the increased skidding resistance and reduced rolling resistance of HVBR-based ionomers were also realized. It was acknowledged as a considerable challenge to simultaneously enhance these properties. The strategy developed here suggests a feasible pathway toward high-performance “green” tires with low noise, superior comfort and excellent auto-braking performance.

Bottlebrush Amphiphilic Polymer Co-Networks.

We report the synthesis of novel poly(ethylene glycol) and poly(dimethyl siloxane) (PEG and PDMS, respectively) bottlebrush amphiphilic polymer co-networks (B-APCNs) with high gel fractions by a grafting-through ring-opening metathesis polymerization. By varying the volume fraction of PEG (), we alter the crystallinity of the networks, achieving complete suppression of PEG crystallinity at . Furthermore, we show that the crystallinity of these networks can be tuned to alter their moduli. Through dynamic mechanical analysis, we show that the storage and loss moduli of networks with completely suppressed crystallinity () behave similarly to a PDMS homopolymer bottlebrush network. These bottlebrush networks represent an unexplored architecture for the field of amphiphilic polymer co-networks.

Influence of electron‐beam irradiation on plasticity‐controlled and crack‐growth‐controlled failure in high‐density polyethylene

AbstractIn the present study, the influence of electron‐beam irradiation on plasticity‐controlled and crack‐growth‐controlled failure in high‐density polyethylene (HDPE) is investigated and the effect of both molecular weight distribution (MWD) and short chain branching (SCB) content are taken into account. Size exclusion chromatography (SEC) is used to study the evolution of the MWD of the sol fraction as a function of irradiation dose. Here, it is seen that chains shorter than the percolation threshold (5 kDa) are largely unaffected by electron beam radiation, while the fraction of longest chains (M &gt; 300 kDa) is nearly entirely incorporated into the cross‐linked network. Both yield stress and Young's modulus increased with irradiation dose, where the magnitude of the increase appears to be connected to the gel fraction. The (fatigue) crack growth kinetics of the grades changed relatively little with irradiation dose, which is unexpected. Furthermore, convergence of the crack growth kinetics parameter to a narrow range of values could be observed for the investigated grades at relatively high gel fractions. This would imply that the crack growth kinetics become increasingly independent of the MWD upon irradiation cross‐linking, which could be attributed to a shift in the underlying crack growth mechanism from chain slip to chain scission.

Enzymatically Crosslinked In Situ Synthesized Silk/Gelatin/Calcium Phosphate Hydrogels for Drug Delivery.

Our research focuses on combining the valuable properties of silk fibroin (SF) and calcium phosphate (CaP). SF is a natural protein with an easily modifiable structure; CaP is a mineral found in the human body. Most of the new age biocomposites lack interaction between organic/inorganic phase, thus SF/CaP composite could not only mimic the natural bone, but could also be used to make drug delivery systems as well, which can ensure both healing and regeneration. CaP was synthesized in situ in SF at different pH values, and then crosslinked with gelatin (G), horseradish peroxide (HRP), and hydrogen peroxide (H2O2). In addition, dexamethasone phosphate (DEX) was incorporated in the hydrogel and drug delivery kinetics was studied. Hydrogel made at pH 10.0 was found to have the highest gel fraction 110.24%, swelling degree 956.32%, and sustained drug delivery for 72 h. The highest cell viability was observed for the hydrogel, which contained brushite (pH 6)—512.43%.

Ultraviolet-patterned acrylic pressure-sensitive adhesives for flexible displays

Acrylic pressure-sensitive adhesives (PSAs) are extensively used to fasten display layers. Although PSAs must show sufficient adhesion for application to existing displays, PSAs must utilize stretching and recovery to mitigate the effects of deformation for application to flexible displays. Therefore, in this study, an ultraviolet (UV)-patterned acrylic PSA was prepared by incorporating a region showing variable degrees of crosslinking achieved using a contrasting UV-patterned film. The gel fraction was measured to confirm the degree of crosslinking, and the adhesion was measured by peel strength, pull-off, and lap shear tests. Dynamic mechanical analysis (DMA) stress relaxation was used to measure the recovery. The highest gel fraction was obtained at a crosslinker content of 1 part per hundred resin (phr) and a UV dose of 1600 mJ/cm2. The low-crosslink-density area was optimized using the 50% gray patterned film. The acrylic PSA prepared with 0.001 phr of 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT), a light-emitting compound used to visualize the pattern formation, showed the clearest pattern. Although the adhesion of the UV-patterned acrylic PSA initially decreased, it gradually increased for the 2 mm pattern. However, the shear adhesion was maintained without appreciably changing. Although the acrylic PSA could not withstand certain deformation conditions during UV patterning, it was stretchable at a pattern size of 4 mm, and the recovery increased to approximately 60% at a pattern size of 2 mm. The results confirmed that the UV-patterned PSA is suitable for application to flexible displays.

Development of photo-crosslinkable collagen hydrogel building blocks for vascular tissue engineering applications: A superior alternative to methacrylated gelatin?

The present work targets the development of collagen-based hydrogel precursors, functionalized with photo-crosslinkable methacrylamide moieties (COL-MA), for vascular tissue engineering (vTE) applications. The developed materials were physico-chemically characterized in terms of crosslinking kinetics, degree of modification/conversion, swelling behavior, mechanical properties and in vitro cytocompatibility. The collagen derivatives were benchmarked to methacrylamide-modified gelatin (GEL-MA), due to its proven track record in the field of tissue engineering. To the best of our knowledge, this is the first paper in its kind comparing these two methacrylated biopolymers for vTE applications. For both gelatin and collagen, two derivatives with varying degrees of substitutions (DS) were developed by altering the added amount of methacrylic anhydride (MeAnH). This led to photo-crosslinkable derivatives with a DS of 74 and 96% for collagen, and a DS of 73 and 99% for gelatin. The developed derivatives showed high gel fractions (i.e. 74% and 84%, for the gelatin derivatives; 87 and 83%, for the collagen derivatives) and an excellent crosslinking efficiency. Furthermore, the results indicated that the functionalization of collagen led to hydrogels with tunable mechanical properties (i.e. storage moduli of [4.8–9.4 kPa] for the developed COL-MAs versus [3.9–8.4 kPa] for the developed GEL-MAs) along with superior cell-biomaterial interactions when compared to GEL-MA. Moreover, the developed photo-crosslinkable collagens showed superior mechanical properties compared to extracted native collagen. Therefore, the developed photo-crosslinkable collagens demonstrate great potential as biomaterials for vTE applications.