Methacryloyl Groups Research Articles

<strong>Effect of 3-methacryloxypropyltrimethoxysilane on diametral tensile strength of rice husk silica-based dental composite </strong>

ABSTRACTIntroduction: Rice husk silica has been studied as a filler in dental composite, however, the mechanical properties of the resulting composites are below the commercial due to the poor surface modification between silica and resin matrix. 3-methacryloxyprpyltrimethoxysilane (MPTS) is one of the coupling agents that are effective to modify the silica surface. The purpose of this study to analyze the effect of MPTS on the diametral tensile strength (DTS) of the self-made composite using rice husk silica. Methods: The research type of this study was an experimental research laboratory. The samples (26 samples) were divided into two groups, namely the test group (using MPTS-modified silica) and the control group (using non-modified silica). The samples were cylindrical in shape with a diameter of 6.0 ± 0.1 mm and a height of 3.0 ± 0.1 mm according to ANSI/ADAS No. 27, 1993 and ISO 4049, 1988. The Fourier Transform Infrared (FTIR), HORIBA, was used to characterize the MPTS grafting on the silica surface. The DTS value is measured by Universal Testing Machine (UTM), Lloyd LRX Plus. Results: FTIR presents the additional peak of carboxyl and methacryloyl group at 1716, 1555, and 1410 cm-1 wavenumber, respectively in MPTS-modified silica. The DTS value of the test group was 43.40 ± 4.43 MPa and the control group was 25.80 ± 2.63 MPa. The test group was significantly higher than the control group (p-value = 0.001). Conclusion: The MPTS is effective to enhance the DTS value of rice husk silica-based composite.Keywords: Rice husk silica; dental composite; diametral tensile strength; 3-methacryloxypropyltrimethoxysilane.

New Gelatin-Based Hydrogel Foams for Improved Substrate Conversion of Immobilized Horseradish Peroxidase.

Hydrogel foams provide an aqueous environment that is very attractive for the immobilization of enzymes. To this end, functional polymers are needed that can be converted into hydrogel foams and that enable bioconjugation while maintaining high enzyme activity. The present study demonstrates the potential of biotinylated gelatin methacryloyl (GM10EB) for this purpose. GM10EB is synthesized in a two-step procedure with gelatin methacryloyl (GM10) being the starting point. Successful biotinylation is confirmed by 2,4,6-trinitrobenzene sulfonic acid and 4'-hydroxyazobenzene-2-carboxylic acid/avidin assays. Most importantly, a high methacryloyl group content (DM) is maintained in GM10EB, so that solutions of GM10EB show both a sufficiently low viscosity for microfluidic foaming and a pronounced curing behavior. Thus, foamed and nonfoamed GM10EB hydrogels can be prepared via radical crosslinking of the polymer chains. Within both sample types, biotin groups are available for bioconjugation, as is demonstrated by coupling streptavidin-conjugated horseradish peroxidase to the hydrogels. When assessing the substrate conversion rate rA in foamed hydrogels by enzymatic conversion of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), a value for rA 12 times higher than the value for nonfoamed hydrogels of the same mass is observed. In other words, rA can be successfully tailored by the hydrogel morphology.

Phototethering of Collagen onto Polyetheretherketone Surfaces to Enhance Osteoblastic and Endothelial Performance

Polyetheretherketone (PEEK) is a candidate material for bone implants as an alternative to metals. However, PEEK exhibits poor osseointegration and low endothelial compatibility. This study demonstrates the phototethering of collagen onto PEEK surfaces to facilitate osteoblastic and vascular endothelial performance. In particular, collagen with methacryloyl groups is covalently tethered to the PEEK surface via surface-initiated photopolymerization. This process is simpler than the conventional method of collagen-tethering and can be extended to the surface-patterning treatment of collagen. The collagen is confirmed to be tethered to the PEEK surface using attenuated total reflection Fourier transform infrared measurements, bicinchoninic acid assays, and atomic force microscopic observations. When human bone marrow-derived mesenchymal stem cells (HbmMSCs) are cultured on collagen-tethered PEEK (COL-PEEK) surfaces, the cells favorably adhere and proliferate. After inducing osteogenic differentiation, the cells on the COL-PEEK surfaces show higher expression levels of osteoblast-related genes and mineralization than those on the PEEK surface. Moreover, the tethering of collagen greatly improves endothelial proliferation. The COL-PEEK surfaces promotes endothelial networking in coculture with HbmMSCs. These results suggest that COL-PEEK is highly compatible with both osteoblasts and vascular endothelial cells. COL-PEEK is a promising implant that induces osteogenesis and angiogenesis to repair bone tissues.

Diselenide as a Dual Functional Mechanophore Capable of Stress Self-Reporting and Self-Strengthening in Polyurethane Elastomers

Diselenide as a Dual Functional Mechanophore Capable of Stress Self-Reporting and Self-Strengthening in Polyurethane Elastomers

Human Protein-Based Porous Scaffolds as Platforms for Xeno-Free 3D Cell Culture.

Extracellular matrix and protein-based biomaterials emerge as attractive sources to produce scaffolds due to their great properties regarding biocompatibility and bioactivity. In addition, there are concerns regarding the use of animal-derived supplements in cell culture not only due to the risk of transmission of xenogeneic contaminants and antigens but also due to ethical issues associated with collection methods. Herein, a novel human protein-derived porous scaffold produced from platelet lysates (PL) as platform for xeno-free 3D cell culture has been proposed. Human PL are chemically modified with methacryloyl groups (PLMA) to make them photocrosslinkable and used as precursor material to produce PLMA-based sponges. The herein reported human-based sponges have highly tunable morphology and mechanical properties, with an internal porous structure and Young's modulus dependent on the concentration of the polymer. Human adipose-derived stem cells (hASCs) are cultured on top of PLMA sponges to validate their use for 3D cell culture in xeno-free conditions. After 14 days hASCs remained viable, and results show that cells are able to proliferate during time even in the absence of animal-derived supplementation. This study reveals for the first time that such scaffolds can be promising platforms for culture of human cells avoiding the use of any animal-derived supplement.

Highly Adhesive, Stretchable and Breathable Gelatin Methacryloyl-based Nanofibrous Hydrogels for Wound Dressings.

Adhesive and stretchable nanofibrous hydrogels have attracted extensive attraction in wound dressings, especially for joint wound treatment. However, adhesive hydrogels tend to display poor stretchable behavior. It is still a significant challenge to integrate excellent adhesiveness and stretchability in a nanofibrous hydrogel. Herein, a highly adhesive, stretchable, and breathable nanofibrous hydrogel was developed via an in situ hybrid cross-linking strategy of electrospun nanofibers comprising dopamine (DA) and gelatin methacryloyl (GelMA). Benefiting from the balance of cohesion and adhesion based on photocross-linking of methacryloyl (MA) groups in GelMA and the chemical/physical reaction between GelMA and DA, the nanofibrous hydrogels exhibited tunable adhesive and mechanical properties through varying MA substitution degrees of GelMA. The optimized GelMA60-DA exhibited 2.0 times larger tensile strength (2.4 MPa) with an elongation of about 200%, 2.3 times greater adhesive strength (9.1 kPa) on porcine skin, and 3.1 times higher water vapor transmission rate (10.9 kg m-2 d-1) compared with gelatin nanofibrous hydrogels. In parallel, the GelMA60-DA nanofibrous hydrogels could facilitate cell growth and accelerate wound healing. This work presented a type of breathable nanofibrous hydrogels with excellent adhesive and stretchable capacities, showing great promise as wound dressings.

Reinforcing Poly(methyl methacrylate) with Bacterial Cellulose Nanofibers Chemically Modified with Methacryolyl Groups.

Nanofibrillated bacterial cellulose (NFBC), a type of cellulose nanofiber biosynthesized by Gluconacetobacter sp., has extremely long (i.e., high-aspect-ratio) fibers that are expected to be useful as nanofillers for fiber-reinforced composite resins. In this study, we investigated a composite of NFBC and poly(methyl methacrylate) (PMMA), a highly transparent resin, with the aim of improving the mechanical properties of the latter. The abundant hydroxyl groups on the NFBC surface were silylated using 3-(methacryloyloxy)propyltrimethoxysilane (MPTMS), a silane coupling agent bearing a methacryloyl group as the organic functional group. The surface-modified NFBC was homogeneously dispersed in chloroform, mixed with neat PMMA, and converted into PMMA composites using a simple solvent-casting method. The tensile strength and Young’s modulus of the composite increased by factors of 1.6 and 1.8, respectively, when only 0.10 wt% of the surface-modified NFBC was added, without sacrificing the maximum elongation rate. In addition, the composite maintained the high transparency of PMMA, highlighting that the addition of MPTMS-modified NFBC easily reinforce PMMA. Furthermore, interactions involving the organic functional groups of MPTMS were found to be very important for reinforcing PMMA.

Nonglutaraldehyde crosslinked bioprosthetic heart valves based on 2-isocyanatoethyl methacrylate crosslinked porcine pericardium with improved properties of stability, cytocompatibility and anti-calcification

Valvular heart diseases (VHD) have a high incidence in the elderly, and the morbidity and fatality rate of VHD increase gradually. To save the lives of patients at the end stage of VHD, valve replacement is the most effective treatment. Owning to the good hydrodynamic performance and application of transcatheter aortic valve replacement (TAVR), bioprosthetic heart valves (BHVs) fabricated from glutaraldehyde crosslinked porcine or bovine pericardium have become a popular choice for patients. However, BHVs fail within 10–15 years of implantation due to the structural degradation and calcification which are greatly attributed to glutaraldehyde crosslinking. In this work, 2-isocyanatoethyl methacrylate (ICM) was used as crosslinking agent for the first time to stabilize porcine pericardium by radical polymerization crosslinking. The ICM-crosslinked pericardium (PICM10-PP) was demonstrated to exhibit better cytocompatibility, mechanical property, and milder immune responses compared with glutaraldehyde crosslinked porcine pericardium (GA-PP). In addition, the PICM10-PP was less calcific than GA-PP after 30 and 90 days of subcutaneous implantation. Following the guidance of ISO5840-3, the hydrodynamic performance and durability of PICM10-PP were evaluated and demonstrated to conform the requirements for BHVs. These results indicate that ICM is a potential alternative of glutaraldehyde in crosslinking BHVs. A nonglutaraldehyde crosslinked bioprosthetic heart valve based 2-isocyanatoethyl methacrylate (ICM) crosslinked porcine pericardium. Methacryloyl groups were introduced to the porcine pericardium through the reaction between collagen and ICM, and the crosslinking was achieved through subsequent radical polymerization. The crosslinked porcine pericardium exhibited enhanced stability, cytocompatibility, mechanical property, anti-calcification hemocompatibility, and its hydrodynamic performance and durability were met the requirements of ISO5840-3. • 2-isocyanatoethyl methacrylate (ICM) was used as nonglutaraldehyde crosslinking agent for the first time for porcine pericardium. • The ICM-crosslinked pericardium (PICM10-PP) exhibited improved cytocompatibility and mechanical property.. • PICM10-PP was shown to be dramatically less calcific than GA-PP. • The hydrodynamic performance and durability of PICM10-PP met the requirement of ISO5840-3 for BHVs.

Near-infrared light control of GelMA/PMMA/PDA hydrogel with mild photothermal therapy for skull regeneration

The development of bone tissue engineering indicates some new paths for bone defect repair. Mild photothermal therapy (PTT) is flourishing as an exciting potential method for bone regeneration. Polydopamine nanoparticles exhibit good absorption at infrared wavelengths and can be used as a viable option for the application of mild PTT to bone defects. Herein, a gelatin-methacryloyl/poly(methyl methacrylate)/polydopamine (GelMA/PMMA/PDA) hydrogel was formulated and assessed in terms of mechanical and biological features. We observed that the addition of methacryloyl groups into gelatin and the introduction of PMMA improved the mechanical properties of the hydrogel and ensure the biosecurity. The GelMA/PMMA/PDA hydrogel demonstrated favorable photothermal ability, biocompatibility, and osteogenic effect. In the rat skull defect model, the GelMA/PMMA/PDA hydrogel with mild PTT possesses better bone repair compared with hydrogel-only and control groups. Thus, this mild photothermal hydrogel platform has a beneficial osteogenic ability and provides a novel approach to treat bone defects.

Methacrylated Cartilage ECM-Based Hydrogels as Injectables and Bioinks for Cartilage Tissue Engineering

Articular cartilage (AC) possesses a limited healing potential, meaning that untreated focal joint defects typically progress, leading to the development of degenerative diseases such as osteoarthritis. Several clinical strategies exist that aim to regenerate AC; however, recapitulation of a fully functional, load-bearing tissue remains a significant challenge. This can be attributed, at least in part, to a paucity of biomaterials that truly mimic the native tissue and provide appropriate cues to direct its regeneration. The main structural component of articular cartilage, type II collagen, does not readily gelate at body temperature, challenging the development of cartilage extracellular matrix (cECM)-derived injectable hydrogels and bioinks for AC tissue engineering and bioprinting applications. Here, we describe the development and rheological characterisation of a methacrylated cartilage ECM-based hydrogel/bioink (cECM-MA), which could be photocrosslinked when exposed to ultraviolet (UV) light. Functionalisation of the collagen backbone with methacryloyl groups had a negligible effect on triple helix stability, as demonstrated by circular dichroism spectroscopy. These cECM-MA bioinks demonstrated shear-thinning properties and could be loaded with bone marrow mesenchymal stem cells (BM-MSCs), micro-extruded to generate self-supporting 3D constructs of predefined size and shape, and then photocrosslinked using UV light. Analysis of the cell-laden constructs showed that the BM-MSCs were viable post-printing and underwent chondrogenesis in vitro, generating a tissue rich in sulphated glycosaminoglycans and collagens. These results support the use of methacrylated, tissue-specific ECM-derived hydrogels as bioinks for 3D bioprinting and/or as injectables for cartilage tissue engineering applications.

INVESTIGATION OF 3D CULTURE OF HUMAN ADIPOSE TISSUE-DERIVED MESENCHYMAL STEM CELLS IN A MICROFLUIDIC PLATFORM

Mesenchymal stem cells (MSCs) are multipotent stem cells that can support various tissues including bone marrow, adipose tissue, and synovial fluids, from which they can be readily isolated. The objective of this study is to harness the advantages of microfluidic systems for controlling and enhancing the maintenance and viability, and regenerative properties of MSCs by providing a 3D culture microenvironment with gelatin methacrylate (GelMA) hydrogel and exposing the cells to a slow fluid flow and low shear stress conditions. GelMA has methacryloyl groups and can be crosslinked by a photocuring process using biocompatible photoinitiators. The most common used photoinitiator for cellular encapsulation within hydrogels is the ultraviolet (UV) initiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959 or I2959), but due to its low water solubility and the necessity of using a shorter wavelength light (365 nm), it can lead to cellular phototoxic and genotoxic effects. To overcome these limitations, lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) have recently been used with GelMA as an alternative photoinitiator. Because LAP is highly water soluble and has a 10 times faster polymerization rate, and it requires a visible light (λ = 405 nm) which makes it much safer for the cells, we use 10% GelMA together with 0.05% LAP photoinitiator for bioprinting human adipose tissue derived MSCs (hAT-MSCs) onto a membrane that has a 40 µm mesh size. To demonstrate a microfluidic culture advancement for improving the biological activities and regenerative capacity of the cells including cell adhesion, growth, viability and proliferation capacity as ultimate goals of this study, the membrane carrying the bioprinted construct was placed in a PDMS microchannel and exposed to the fluid to obtain dynamic microenvironments found in the human body. As a result, the cells were successfully maintained in the microfluidic 3D cell culture for two days, with a high cell viability of 99%.

Synthesis and Evaluation of Methacrylated Poly(2-ethyl-2-oxazoline) as a Mucoadhesive Polymer for Nasal Drug Delivery

Methacrylated poly(2-ethyl-2-oxazoline) (PEOZ) was synthesized by partial hydrolysis of 500 kDa PEOZ, and the resulting poly[(2-ethyl-2-oxazoline)-co-ethylenimine] P(EOZ-co-EI) was subsequently reacted with methacrylic anhydride. The successful synthesis of methacrylated PEOZ (MAPEOZ) was confirmed by proton nuclear magnetic resonance (1H NMR), infrared spectroscopy, and differential scanning calorimetry. The degrees of hydrolysis and methacrylation were determined by 1H NMR spectra. MAPEOZ exhibited temperature-responsive properties, which were dependent on the degree of methacrylation. On that basis, three soluble MAPEOZ derivatives with different degrees of methacrylation were selected and investigated in cell toxicity studies, showing no significant cytotoxicity against the HEK293 cell line. A slug mucosal irritation assay showed that PEOZ and MAPEOZ do not cause mucosal irritation. The presence of methacryloyl groups and residual amines had a remarkable synergistic effect on the mucoadhesive properties of these polymers. These poly(2-ethyl-2-oxazoline) derivatives have excellent potential as mucoadhesive materials for developing formulations for drug delivery via mucosal routes of administration.

Double cross-linked poly(vinyl alcohol) microcomposite hydrogels with high strength and cell compatibility

Polyvinyl alcohol (PVA) hydrogels, due to their excellent tissue viscoelasticity and biocompatibility, are widely used in biomedical fields e.g. tissue engineering. However, their poor mechanical properties greatly limit their applications, especially as load-bearing implants in the body. To address this issue, we first synthesize photocrosslinkable PVA-glycidyl methacrylate (PVAGMA) with the extremely low substitution degree (DS = 0.01) of methacryloyl groups, which can undergo chemical crosslinking to form a hydrogel network with good compression performance. Microcrystalline cellulose (MCC)/PVAGMA hydrogels are subsequently fabricated by photopolymerization approach followed by physical crosslinking with tannic acid (TA) as a cross-linking agent. By combing chemical and physical crosslinking, the double crosslinked PVA microcomposite hydrogels exhibit excellent tensile/compression strengths. Specifically, the hydrogels present 23-fold, 20-fold, and 25-fold increase in fracture stress, elastic modulus, and toughness respectively, compared to the pure PVAGMA hydrogels. Notably, a hydrogel with the optimum composition can lift a weight of 3.775 kg, which is about 2220 times of its own weight. Moreover, the hydrogels are cytocompatible at a relatively low extraction concentration, demonstrating their potential in biomaterials.

Direct Surface Modification of Polycaprolactone-Based Shape Memory Materials to Introduce Positive Charge Aiming to Enhance Cell Affinity.

In this study, the introduction of a positive charge on the surface of a shape memory material was investigated to enhance cell affinity. To achieve this, the direct chemical modification of a material surface was proposed. Sheet-type, crosslinked poly(caprolactone-co-α-bromo-ɤ-butyrolactone) (poly(CL-co-BrBL)) were prepared, and the direct reaction of amino compounds with bromo groups was conducted on the material surface with a positive charge. Branched poly(CL-co-BrBL) was prepared, followed by the introduction of methacryloyl groups to each chain end. Using the branched macromonomers, stable and sheet-type materials were derived through UV-light irradiation. Then, the materials were soaked in an amino compound solution to react with the bromo groups under various conditions. Differential scanning calorimetry and surface analysis of the modified materials indicated that 10 vol% of N, N-dimethylethylenediamine in n-hexane and 1 h soaking time were optimal to maintain the inherent thermal properties. The achievement of increased luminance and a positive zeta potential proved that the direct modification method effectively introduced the positive charge only on the surface, thereby enhancing cell affinity.

3D-Printable Hierarchical Nanogel-GelMA Composite Hydrogel System.

The strength of the extracellular matrix (ECM) is that it is hierarchical in terms of matrix built-up, matrix density and fiber structure, which allows for hormones, cytokines, and other small biomolecules to be stored within its network. The ECM-like hydrogels that are currently used do not possess this ability, and long-term storage, along with the need for free diffusion of small molecules, are generally incompatible requirements. Nanogels are able to fulfill the additional requirements upon successful integration. Herein, a stable hierarchical nanogel–gelatin methacryloyl (GelMA) composite hydrogel system is provided by covalently embedding nanogels inside the micropore network of GelMA hydrogel to allow a controlled local functionality that is not found in a homogenous GelMA hydrogel. Nanogels have emerged as a powerful tool in nanomedicine and are highly versatile, due to their simplicity of chemical control and biological compatibility. In this study, an N-isopropylacrylamide-based nanogel with primary amine groups on the surface was modified with methacryloyl groups to obtain a photo-cross-linking ability similar to GelMA. The nanogel-GelMA composite hydrogel was formed by mixing the GelMA and the photo-initiator within the nanogel solution through UV irradiation. The morphology of the composite hydrogel was observed by scanning electron microscopy, which clearly showed the nanogel wrapped within the GelMA network and covering the surface of the pore wall. A release experiment was conducted to prove covalent bonding and the stability of the nanogel inside the GelMA hydrogel. In addition, 3D printability studies showed that the nanogel-GelMA composite ink is printable. Therefore, the suggested stable hierarchical nanogel-GelMA composite hydrogel system has great potential to achieve the in situ delivery and controllable release of bioactive molecules in 3D cell culture systems.

Synthesis of Photo-degradable Polyphthalaldehyde Macromonomer and Adhesive Property Changes of its Copolymer with Butyl Acrylate on UV-irradiation

We prepared a new polyphthalaldehyde (PPA) macromonomer by introducing a polymerizable methacryloyl group at the terminal of PPA main-chain. Resulting macromonomer was copolymerized with butyl acrylate to obtain pressure-sensitive adhesives (PSAs). We also compared the behavior of the copolymers with those of polymer blends of poly(butyl acrylate) and linear PPA polymers to clarify the role of polymerization. Higher peel strengths were observed for copolymers than those of corresponding polymer blends. As an increase in irradiation time, the strength generally decreased, although once increased for the copolymer films at the early stage. These results suggest that the introduction and the depolymerization of PPA side-chains caused drastic changes in adhesive properties.

Electromagnetic Shielding Effectiveness of Polyaniline/Modified-Poly(vinyl Alcohol) Film Composite

This work reports the preparation of a conductive composite film, from one of the most conductive polymers, polyaniline (PAn), and a methacryloyl group attached-poly(vinyl alcohol) (M-PVA), in a few straightforward process steps. First, the -OH groups of PVA were modified through trans-esterification reaction using glycidyl methacrylate (GMA), in the presence of N, N, N, N-tetramethylethylenediamine (TEMED) as a catalyst at 60 ℃. After casting the M-PVA into the film in the organic media, the polymerization of aniline was performed onto this surface using APS as an oxidant in 1.0 M HCl. The effects of conditions, including the concentrations of M-PVA used for film-casting, and aniline, were investigated on PAn content (%) and conductivity. It was observed that the conductivity of the thin and almost transparent composite films (containing 17.5% of PAn) reached to 10-4 Scm-1. The characterization of the samples was conducted by ATR-FTIR, contact angle-wetting time measurements, and SEM-EDX techniques. The usability of the conductive composite film in the electromagnetic interference (EMI) shielding was examined within 30 MHz-3 GHz, through the measurement of electromagnetic interference shielding effectiveness (EMSE) and relative shielding efficiency values of absorption (Ab) and reflection (Re). Twice PAn deposited-composite film showed an average 5.6 dB EMSE value that corresponds to 71% of shielding through the Ab mechanism, dominantly.

3D printed colloidal biomaterials based on photo-reactive gelatin nanoparticles

Biomaterials-based strategies have shown great promise for tissue regeneration. 3D printing technologies can deliver unprecedented control over architecture and properties of biomaterial constructs when combined with innovative material design strategies. Colloidal gels made of polymeric nanoparticles are attractive injectable and self-healing systems, but their use as bio-inks for extrusion-based printing is largely unexplored. Here, we report 3D printing of novel biomaterial constructs with shape memory behavior using photo-reactive gelatin nanoparticles as colloidal building blocks. These nanoparticles are stabilized with intraparticle covalent crosslinks, and also contain pendant methacryloyl groups as photo-reactive moieties. While non-covalent interactions between nanoparticles enable formation of colloidal gel inks that are printable at room temperature, UV-induced covalent interparticle crosslinks based on methacryloyl moieties significantly enhance mechanical properties of printed constructs. Additionally, the UV crosslinking modality enables remarkable control over swelling, degradation, and biomolecule release behavior of 3D constructs. Finally, by exploiting the mechanical properties of colloidal biomaterials after UV crosslinking, 3D constructs can be designed with shape memory properties, returning to their original programmed geometry upon re-hydration. Accordingly, these novel colloidal inks exhibit great potential to serve as bio-inks for 3D printing of biomaterials with shape-morphing features for a wide range of tissue engineering and regenerative medicine applications.

3D-Printed Gelatin Methacryloyl-Based Scaffolds with Potential Application in Tissue Engineering.

The development of materials for 3D printing adapted for tissue engineering represents one of the main concerns nowadays. Our aim was to obtain suitable 3D-printed scaffolds based on methacrylated gelatin (GelMA). In this respect, three degrees of GelMA methacrylation, three different concentrations of GelMA (10%, 20%, and 30%), and also two concentrations of photoinitiator (I-2959) (0.5% and 1%) were explored to develop proper GelMA hydrogel ink formulations to be used in the 3D printing process. Afterward, all these GelMA hydrogel-based inks/3D-printed scaffolds were characterized structurally, mechanically, and morphologically. The presence of methacryloyl groups bounded to the surface of GelMA was confirmed by FTIR and 1H-NMR analyses. The methacrylation degree influenced the value of the isoelectric point that decreased with the GelMA methacrylation degree. A greater concentration of photoinitiator influenced the hydrophilicity of the polymer as proved using contact angle and swelling studies because of the new bonds resulting after the photocrosslinking stage. According to the mechanical tests, better mechanical properties were obtained in the presence of the 1% initiator. Circular dichroism analyses demonstrated that the secondary structure of gelatin remained unaffected during the methacrylation process, thus being suitable for biological applications.

Segmented Polyurethane Elastomers with Mechanochromic and Self‐Strengthening Functions

AbstractMechanochromic elastomers that exhibit force‐induced cross‐linking reactions in the bulk state are introduced. The synthesis of segmented polyurethanes (SPUs) that contain difluorenylsuccinonitrile (DFSN) moieties in the main chain and methacryloyl groups in the side chains was carried out. DFSN was selected as the mechanophore because it dissociates under mechanical stimuli to form pink cyanofluorene (CF) radicals, which can also initiate the radical polymerization of methacrylate monomers. The obtained elastomers generated CF radicals and changed color by compression or extension; they also became insoluble due to the mechanically induced cross‐linking reactions. Additionally, an SPU containing diphenylmethane units also exhibited highly sensitive mechanofluorescence. To the best of our knowledge, this is the first report to demonstrate damage detection ability and changes in the mechanical properties of bulk elastomers induced by simple compression or extension.