Photocrosslinking Reaction Research Articles

All-natural hydrogel composed of carboxymethyl chitosan and oxidized dextran for promoting wound healing by immune-microenvironment regulation

Chronic wound treatment has always been a major clinical challenge owing to complex and dynamic wound microenvironment. The design and development of effective management with antimicrobial activity, ROS-scavenging and regulation immune response is vital for tissue repair. Herein, we developed puerarin (PUE) loaded a double network hydrogel consisting of methacrylated carboxymethyl chitosan and oxidized dextran with Schiff base and photo-crosslinking reaction. The composite hydrogel presented fast self-healing and outstanding compressive performance to bear deformation. The hydrogel exhibits a cumulative drug release pattern with biphasic release, which offers great potential for accelerating tissue healing at all stages of wounding. In addition, the hydrogel has good biocompatibility, antimicrobial ability and tube-forming ability in vitro. The full-thickness skin wound model of Staphylococcus aureus infection showed that the hydrogel dressing can accelerate tissue repair. This study demonstrated that the design of combing natural biomacromolecules with traditional Chinese medicine could be severed as a promising candidate biomaterial for skin tissue recovery.

Self-healing cellulose nanocrystals/fluorinated polyacrylate with double dynamic interactions of coumarin groups and multiple hydrogen bonds

In this work, self-healing cellulose nanocrystals/fluorinated polyacrylate with dual dynamic networks of photoreversible crosslinking network and high-density hydrogen bonds was prepared by Pickering emulsion polymerization. The main work was to study the effects of 7-(2-methacryloyloxy)-4-methylcoumarin (CMA) and 2-ureido-4[1H]-pyrimidinone methyl methacrylate (UPyMA) monomer dosage on emulsion polymerization and latex film properties. The monomer conversion increased first and then decreased as the CMA and UPyMA monomer dosage increased, while a reverse trend was noted for the particle size and particle size distribution. Incorporating UPyMA allowed the rapid formation of hydrogen bonds at the crosslinking sites, which increased the interaction force between the healing surfaces. Besides, reversible photocrosslinking reaction of coumarin groups provided another support for self-healing performance. Moreover, the influence of self-healing temperature, self-healing time and UV irradiation on the self-healing ability was also systematically investigated The tensile strength of the prepared cellulose nanocrystals/fluorinated polyacrylate latex film exhibited a self-healing efficiency of 91.4 % under 365 nm UV irradiation and 80 °C for 12 h. The latex film had excellent thermal stability as was shown by TG and DTG analyses. The outstanding self-healing capability of latex film was attributed to the reversible photodimerization of coumarin groups and multiple hydrogen bonds. In addition, the water-oil repellent and mechanical properties of the latex films were improved as the CMA and UPyMA monomer dosage increased.

Computational modelling of scleral photocrosslinking: from rat to minipig to human.

Selective scleral crosslinking has been proposed as a novel treatment to increase scleral stiffness to counteract biomechanical changes associated with glaucoma and high myopia. Scleral stiffening has been shown by transpupillary peripapillary scleral photocrosslinking in rats, where the photosensitizer, methylene blue (MB), was injected retrobulbarly and red light initiated crosslinking reactions with collagen. Here, we adapted a computational model previously developed to model this treatment in rat eyes to additionally model MB photocrosslinking in minipigs and humans. Increased tissue length and subsequent diffusion and light penetration limitations were found to be barriers to achieving the same extent of crosslinking as in rats. Per cent inspired O2, injected MB concentration and laser fluence were simultaneously varied to overcome these limitations and used to determine optimal combinations of treatment parameters in rats, minipigs and humans. Increasing these three treatment parameters simultaneously resulted in maximum crosslinking, except in rats, where the highest MB concentrations decreased crosslinking. Additionally, the kinetics and diffusion of photocrosslinking reaction intermediates and unproductive side products were modelled across space and time. The model provides a mechanistic understanding of MB photocrosslinking in scleral tissue and a basis for adapting and screening treatment parameters in larger animal models and, eventually, human eyes.

Hydrophilic Photocrosslinkers as a Universal Solution to Endow Water Affinity to a Polymer Photocatalyst for an Enhanced Hydrogen Evolution Rate.

A universal approach for enhancing water affinity in polymer photocatalysts by covalently attaching hydrophilic photocrosslinkers to polymer chains is presented. A series of bisdiazirine photocrosslinkers, each comprising bisdiazirine photophores linked by various aliphatic (CL-R) or ethylene glycol-based bridge chains (CL-TEG), is designed to prevent crosslinked polymer photocatalysts from degradation through a safe and efficient photocrosslinking reaction at a wavelength of 365nm. When employing the hydrophilic CL-TEG as a photocrosslinker with polymer photocatalysts (F8BT), the hydrogen evolution reaction (HER) rate is considerably enhanced by 2.5-fold compared to that obtained using non-crosslinked F8BT photocatalysts, whereas CL-R-based photocatalysts yield HER rates comparable to those of non-crosslinked counterparts. Photophysical analyses including time-resolved photoluminescence and transient absorption measurements reveal that adding CL-TEG accelerates exciton separation, forming long-lived charge carriers. Additionally, the in-depth study using molecular dynamics simulations elucidates the dual role of CL-TEG: it enhances water penetration into the polymer matrix and stabilizes charge carriers after exciton generation against undesirable recombination. Therefore, the strategy highlights endowing a high-permittivity environment within polymer photocatalyst in a controlled manner is crucial for enhancing photocatalytic redox reactivity. Furthermore, this study shows that this hydrophilic crosslinker approach has a broad applicability in general polymer semiconductors and their nanoparticulate photocatalysts.

Mechanisms and Performances of Physically and Chemically Crosslinked Gelatin-Based Hydrogels as Advanced Sustainable and Reusable "Jelly Ice Cube" Coolants.

A novel reusable, plastic-free, and stable cooling medium, Jelly Ice Cubes (JIC), is developed based on crosslinked gelatin hydrogels for sustainable temperature control. A novel process involving a rapid-freezing-slow-thawing treatment and a subsequent photo-crosslinking reaction induced by menadione sodium bisulfite, a newly discovered photosensitizer, is able to effectively consolidate a three-dimensional (3-D) hydrogel network to survive repeated application freeze-thaw cycles (AFTCs). This study reveals the mechanisms and evidence of the synergistic effects of the physical and chemical crosslinking reactions. The results experimentally prove that the rapid-freezing-slow-thawing treatment induces the generation of gelatin microcrystalline domains, refines the protein polymeric network, and reduces the intervening distance for subsequent photo-crosslinking sites. The refined hydrogel 3-D network is consolidated by the photo-crosslinking reaction occurring at the intersectional areas of the gelatin microcrystalline domains. The proposed crosslinking approach yields JICs with superior mechanical properties, robustness, and consistent water content, even after repeated AFTCs, all the while retaining cooling efficiency and biodegradability. The proposed crosslinked hydrogel structure is potentially applicable to engineering other hydrogel materials, offering sustainble and biodegradable solutions with enhanced resilience against phase changes.

Tandem photo-crosslinking/sol–gel reaction for the green synthesis of morphology-alterable, redox-responsive silica particles

Silica-based nanoparticles have been employed in versatile biomedical applications during the past decades and one of the important research focuses has been the synthesis of biothiol-degradable redox responsive silica to resolve the toxicity concerns of bioaccumulation. In the conventional sol-gel approach, the use of acidic or basic catalyst was always necessary. Solvent, heating, and templates were often applied. Besides, multi-step synthetic procedures were also frequently required to obtain the desired silane with disulfide-linkage for the following synthesis. We developed a facile and green photo-crosslinking coupled sol–gel reaction to produce disulfide-linked redox-responsive silica particles in water at room temperature. The reaction was template-free and initiated by visible light irradiation of photosensitizer (rose bengal). The particle size was tunable by adjusting the concentration of silica precursors, photosensitizer, and irradiation time of LED. The morphologies of the silica nanoparticles can be dramatically altered by simply changing the thiolated silica precursors. The kinetics of the silica precursors during the hydrolysis and photocrosslinking reactions played a critical role. Rose bengal served as a photosensitizer for silica nanoparticle formation and a photodynamic drug. The encapsulated rose bengal remained effective to generate singlet oxygen with superior performance than that of free ones. The disulfide bonds created in the silica matrix responded to reducing reagents, resulting in controllable self-disassembly. Additionally, we found that the presence of magnesium salts affected the rate of the photocrosslinking reaction, forming rod-shaped particles. The current results provide insights for future stimuli-responsive silica-based material development.

Three-Dimensional-Printed Oral Films Based on LCD: Influence Factors of the Film Printability and Received Qualities.

As an oral mucosal drug delivery system, oral films have been of wide concern in recent years because of their advantages such as rapid absorption, being easy to swallow and avoiding the first-pass effect common for mucoadhesive oral films. However, the currently utilized manufacturing approaches including solvent casting have many limitations, such as solvent residue and difficulties in drying, and are not suitable for personalized customization. To solve these problems, the present study utilizes liquid crystal display (LCD), a photopolymerization-based 3D printing technique, to fabricate mucoadhesive films for oral mucosal drug delivery. The designed printing formulation includes PEGDA as the printing resin, TPO as the photoinitiator, tartrazine as the photoabsorber, PEG 300 as the additive and HPMC as the bioadhesive material. The influence of printing formulation and printing parameters on the printing formability of the oral films were elucidated in depth, and the results suggested that PEG 300 in the formulation not only provided the necessary flexibility of the printed oral films, but also improved drug release rate due to its role as pore former in the produced films. The presence of HPMC could greatly improve the adhesiveness of the 3D-printed oral films, but excessive HPMC increased the viscosity of the printing resin solution, which could strongly hinder the photo-crosslinking reaction and reduce printability. Based on the optimized printing formulation and printing parameters, the bilayer oral films containing a backing layer and an adhesive layer were successfully printed with stable dimensions, adequate mechanical properties, strong adhesion ability, desirable drug release and efficient in vivo therapeutic efficacy. All these results indicated that an LCD-based 3D printing technique is a promising alternative to precisely fabricate oral films for personalized medicine.

Improving the catalytic ability of a peptide-based artificial glycosidase through a tyrosine strategy.

Recently, peptide-based artificial enzymes have attracted growing interest due to the similar composition of peptide assemblies to natural enzymes. However, low catalytic activity and stability are still the main challenges for these enzyme-like catalysts. In this study, a tyrosine strategy was developed to construct a peptide-based artificial glycosidase through engaging the Tyr residue into the peptide sequence. We found that the appropriate substitution of Tyr produced an enhanced catalytic ability, because the proximal Tyr residue around catalytic sites acts as a nucleophile, playing an important role in the substrate orientation and proton transfer. Moreover, inspired by the biological function of dityrosine bonds in structural proteins, a photo-crosslinking reaction between the phenolic side chains of Tyr was also employed to form intermolecular covalent bonds in peptide assemblies, which further improved the activity and stability of the artificial glycosidase. This work provides a simple avenue for the designing and construction of efficient glycosidase-like catalysts based on a peptide-based material platform.

A tumor-targetable NIR probe with photoaffinity crosslinking characteristics for enhanced imaging-guided cancer phototherapy.

Spatiotemporally manipulating the in situ immobilization of theranostic agents within cancer cells to improve their bioavailability is highly significant yet challenging in tumor diagnosis and treatment. Herein, as a proof-of concept, we for the first time report a tumor-targetable near-infrared (NIR) probe DACF with photoaffinity crosslinking characteristics for enhanced tumor imaging and therapeutic applications. This probe possesses great tumor-targeting capability, intensive NIR/photoacoustic (PA) signals, and a predominant photothermal effect, allowing for sensitive imaging and effective photothermal therapy (PTT) of tumors. Most notably, upon 405 nm laser illumination, DACF could be covalently immobilized within tumor cells through a photocrosslinking reaction between photolabile diazirine groups and surrounding biomolecules resulting in enhanced tumor accumulation and prolonged retention simultaneously, which significantly facilitates the imaging and PTT efficacy of tumor in vivo. We therefore believe that our current approach would provide a new insight for achieving precise cancer theranostics.

Bioresorbable Chitosan-Based Bone Regeneration Scaffold Using Various Bioceramics and the Alteration of Photoinitiator Concentration in an Extended UV Photocrosslinking Reaction.

Bone tissue engineering (BTE) is an ongoing field of research based on clinical needs to treat delayed and non-union long bone fractures. An ideal tissue engineering scaffold should have a biodegradability property matching the rate of new bone turnover, be non-toxic, have good mechanical properties, and mimic the natural extracellular matrix to induce bone regeneration. In this study, biodegradable chitosan (CS) scaffolds were prepared with combinations of bioactive ceramics, namely hydroxyapatite (HAp), tricalcium phosphate-α (TCP- α), and fluorapatite (FAp), with a fixed concentration of benzophenone photoinitiator (50 µL of 0.1% (w/v)) and crosslinked using a UV curing system. The efficacy of the one-step crosslinking reaction was assessed using swelling and compression testing, SEM and FTIR analysis, and biodegradation studies in simulated body fluid. Results indicate that the scaffolds had comparable mechanical properties, which were: 13.69 ± 1.06 (CS/HAp), 12.82 ± 4.10 (CS/TCP-α), 13.87 ± 2.9 (CS/HAp/TCP-α), and 15.55 ± 0.56 (CS/FAp). Consequently, various benzophenone concentrations were added to CS/HAp formulations to determine their effect on the degradation rate. Based on the mechanical properties and degradation profile of CS/HAp, it was found that 5 µL of 0.1% (w/v) benzophenone resulted in the highest degradation rate at eight weeks (54.48% degraded), while maintaining compressive strength between (4.04 ± 1.49 to 10.17 ± 4.78 MPa) during degradation testing. These results indicate that incorporating bioceramics with a suitable photoinitiator concentration can tailor the biodegradability and load-bearing capacity of the scaffolds.

Effects and Progress of Photo-Crosslinking Hydrogels in Wound Healing Improvement.

Wound healing is a dynamic physiological process, including three stages: inflammation, tissue formation, and remodeling. The quality of wound healing is affected by many topical and systemic factors, while any small factor may affect the process. Therefore, improving the quality of wound healing is a complex and arduous challenge. Photo-crosslinking reaction using visible light irradiation is a novel method for hydrogel preparation. Photo-crosslinking hydrogels can be controlled in time and space, and are not interfered by temperature conditions, which have been widely used in the fields of medicine and engineering. This review aims to summarize the application of photo-crosslinking hydrogels in improving the quality of wound healing, mainly including the material design, application mechanism, and effect of photo-crosslinking hydrogels applied in wound healing, followed by the applicable animal models for experimental research. Finally, this review analyzes the clinical application prospects of photo-crosslinking hydrogels in the field of wound healing.

Solvent-free electrospinning of liquid polybutadienes and their in-situ photocuring

A single-step approach to rapidly convert low molecular weight polybutadienes into fine rubber crosslinked fibers and nonwoven mats without using any heat or solvent was described. This environmentally friendly method consisted in the electrospinning at room temperature of liquid polybutadiene and polybutadiene-graft-maleic anhydride polymers without any solvent; the flying jet was irradiated to trigger the in-situ curing of the forming fibers at ambient conditions, obtaining a good control over the fibrous morphology and enhancing the performance of the membranes. The kinetics of the photo-crosslinking reaction was studied through FT-IR spectroscopy. Liquid polybutadiene-graft-maleic anhydride polymers demonstrated a faster rate of photocuring, compared to neat polybutadienes. In order to further speed up the reaction, a thiol-based crosslinker and a photoinitiator were introduced into the formulations. The photo-induced crosslinking was more efficient as different reactions concomitantly took place: besides the thiol-ene crosslinking involving the multifunctional thiol crosslinker, the oxidation of the polybutadiene chains and the esterification of the maleic anhydride moieties occurred. Moreover, a polar additive was used to control the electrospinning process by lowering the viscosity and increasing the electrical conductivity. The structural, thermal and surface properties of the fabricated polybutadiene-based electrospun membranes were assessed. The membranes exhibited an excellent morphology stability, high insolubility, good thermal properties and a pronounced hydrophobic character.

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity

In situ monitoring of photo-crosslinking reaction of water-soluble bifunctional macromers using magnetic levitation

Crosslinking is one of the fundamental phenomena in polymer science, which happens by forming covalent bonds or relatively short sequences of chemical bonds to join two polymer chains. Crosslinking and the subsequent volume shrinkage of monomers/macromers result in changes in their corresponding density which can be measured using density-based measurement techniques (e.g., dilatometry). Here, we demonstrate a method that allows in situ monitoring of photopolymerization of water-soluble bifunctional macromers using magnetic levitation (MagLev) system. We use a hydrophobic paramagnetic solution to monitor the photopolymerization of water-soluble polyethylene glycol diacrylate (PEGDA) as a model of bifunctional macromers using a ring MagLev system. Based on changes in levitation heights (densities) after illumination of blue light, we have successfully monitored the double bond conversion of PEGDA 700 macromers at various polymerization conditions. Our findings suggest that MagLev can be used as a new and complementary analytical technique for rapid screening of the photopolymerization reactions and measurement of conversions using changes in the levitation height of the macromers.

Injectable and In Situ Gelling Dextran Derivatives Containing Hydrolyzable Groups for the Delivery of Large Molecules.

Recently, we reported the synthesis and characterization of a new dextran derivative obtained by grafting polyethylene glycol methacrylate to a polysaccharide backbone through a carbonate bond. This moiety was introduced because it allows for the fabrication, through a photo-induced crosslinking reaction, of biodegradable hydrogels particularly suitable for the release of high molecular weight molecules. Here, we investigate the influence of the oxyethylene chain length and the molecular weight of the starting dextran on the main properties of the polymeric solutions as well as those of the corresponding hydrogels. All synthesized polymeric derivatives were characterized by FTIR, NMR, and rheological analyses. The photo-crosslinking reaction of the polymers allowed us to obtain biodegradable networks tested for their mechanical properties, swelling, and degradation behavior. The results showed that both the oxyethylene chain length as well as the molecular weight of the starting dextran influenced swelling and degradation of the hydrogel network. As a consequence, the different behaviors in terms of swelling and degradability were able to affect the release of a large model molecule over time, making these matrices suitable candidates for the delivery of high molecular weight drug substances.

Poly(glycerol sebacate)-co-poly(ethylene glycol)/Gelatin Hybrid Hydrogels as Biocompatible Biomaterials for Cell Proliferation and Spreading.

Synthetic polymers have been widely employed to prepare hydrogels for biomedical applications, such as cell culture, drug delivery, and tissue engineering. However, the activity of cells cultured in the synthetic polymer-based hydrogels faces the challenges of limited cell proliferation and spreading compared to cells cultured in natural polymer-based hydrogels. To address this concern, a hybrid hydrogel strategy is demonstrated by incorporating thiolated gelatin (GS) into the norbornene-functionalized poly (glycerol sebacate)-co-polyethylene glycol (Nor_PGS-co-PEG, NPP) network to prepare highly biocompatible NPP/GS_UV hydrogels after the thiol-ene photo-crosslinking reaction. The GS introduces several desirable features (i.e., enhanced water content, enlarged pore size, increased mechanical property, and more celladhesion sites) to the NPP/GS_UV hydrogels, facilitating the cell proliferation and spreading inside the network. Thus, the highly biocompatible NPP/GS_UV hydrogels are promising materials for cell encapsulation and tissue engineering applications. Taken together, the hybrid hydrogel strategy is demonstrated as a powerful approach to fabricate hydrogels with a highly friendly environment for cell culture, expanding the biomedical applications of hydrogels.

Construction and stabilization of a peptide-based peroxidase mimic for the colorimetric detection of uric acid and sarcosine

Abstract Peptide assembly provides a new approach for the construction of enzyme-like catalysts. However, low stability is still a big challenge for the peptide-based enzyme mimics because the non-covalently driven structures are often destroyed when exposed to environmental changes. Inspired by the catalytic centre of natural horseradish peroxidase (HRP) and the biological function of dityrosine in structural proteins, in this study, we presented the construction of a stable peptide-based HRP mimic (CCA-YH) through introducing covalent bonds. CCA-YH was obtained through the co-assembly of YYHYY and hemin, followed by a ruthenium-mediated photo-crosslinking reaction. Catalytic activity assay demonstrated that CCA-YH displayed enhanced catalytic ability than the non-covalent co-assemblies (CA-YH). Remarkably, CCA-YH exhibited superior long-term stability than CA-YH and natural HRP under different pH, temperature, ion strength and organic medium environments, as well as a favorable reusability. Finally, CCA-YH was applied to the colorimetric detection of uric acid and sarcosine in human urine, which displayed satisfactory sensitivity, specificity and reproducibility. This is the first report the construction of stable peptide-based enzyme mimic based on covalent co-assembly strategy.

The Latest Research Progress of New Self‐Repairing Energetic Composites†

This review summarizes research progress in self‐repairing energetic composites based on the design of chemical structure of binders and the introduction of self‐repairing properties between composite interfaces. Researchers have prepared the polyurethane‐urea binder and the GAP self‐repairing binder based on the disulfide bond, the polyurethane binder and FTPB‐PDMI binder based on the Diels‐Alder reaction, and the polyurethane binder based on dynamic photocrosslinking reaction. In addition, PVDF‐co‐HFP/EMIOTf/graphene achieves the self‐repairing behavior of the polymer bonded explosive (PBX). The future development of self‐repairing energetic composites is proposed. It is pointed out that the mechanical properties, processing properties and energy properties should be improved together with the introduction of self‐repairing properties, and the energetic composites which can be repaired in various ways should be prepared.

Systematic Evaluation of Hybridization Property and Photo-Crosslinking Ability of Modified Oligonucleotides Containing Benzophenone-Bearing Glycol Nucleoside Analogs

Antigene technology is the one strategy for the artificial regulation of gene expression by the formation of triple structure on triplex forming oligonucleotide (TFO) with dsDNA. For the enhancement of the thermal stability of triplex structure, photo-crosslinking reaction is attractive by the covalent bond formation between TFO and dsDNA. In this paper, we designed the novel TFOs containing benzophenone moiety as a photo-crosslinkable agent. Several types of glycol nucleoside analogs having glycol scaffold and benzophenone residues with different linker length were prepared, and the these were incorporated into TFOs. The thermal stability of triplex and the photo-crosslinking reaction efficiency of TFOs toward dsDNA was systematically evaluated.

Solvent‐resistant ultrafine nonwoven fibrous membranes by ultraviolet‐assisted electrospinning of organo‐soluble photosensitive polyimide resin

AbstractAn ultraviolet‐assisted electrospinning (UVAES) method was investigated to improve the solvent stability of soluble polyimide (PI) electrospun ultrafine fibrous membranes (UFMs) to assist in the development of fibrous polymeric materials with improved resistance to harsh environmental conditions and to expand the potential applications for such soft filaments. A preimidized soluble negative photosensitive polyimide (PSPI) was synthesized via an one‐step thermal polycondensation from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and 1,1′‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3′‐trifluoromethylphenyl)methane (TFMDA). The PI resin was then fabricated into UFMs by both conventional electrospinning (ES) and UVAES with N,N‐dimethylacetamide (DMAc) as the solvent. During spinning, photo crosslinking reaction occurred, accompanied by simultaneous micro‐jets of PI‐UV ultrafine fibers in the UVAES procedure. This created fibers that were thermally stable at higher than 500°C, reflection over 77% of the 457‐nm‐ wavelength light, whiteness index (WI) higher than 83, and enhanced solvent resistance in DMAc. Generally speaking, compared with the PI UFMs fabricated by conventional ES procedure, the PI‐UV UFMs obtained by the newly‐developed UVAES procedure showed much superior solvent resistance, comparable thermal stability, slightly decreased optical reflectance and WI values, and reduced fiber diameters. These properties are of great value to future applications in microelectronics and wearable technology.