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The novel photo-crosslinking ligand 6OTD-Bp, bearing an alkylamine benzophenone (Bp) with macrocyclic hexaoxazole (6OTD), was shown to preferentially ligate with hybrid G4s through recognizing both G-quartets and their characteristic wide groove. Higher crosslinking yield was observed for hybrid G4 with wider grooves. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are promising alternatives to traditional antibiotics for treating skin wound infections. Nonetheless, their short half‐life in biological environments restricts clinical applicability. Covalent immobilization of AMPs onto suitable substrates offers a comprehensive solution, creating contact‐killing surfaces with long‐term functionality. Here, a copolymer of poly[(hydroxy ethyl acrylamide)‐co‐(4‐benzophenone acrylamide)‐co‐(pentafluorophenyl acrylate)‐co‐(ECOSURF EH‐3 acrylate)], in short poly(HEAAm‐co‐BPAAm‐co‐PFPA‐co‐EH3A), is synthesized by free radical polymerization. Subsequent modification of active ester groups with the amine groups of SAAP‐148, results in a copolymer, that is non‐cytotoxic to human lung fibroblasts. UV photocrosslinking of the benzophenone units yields a polymer network that forms a hydrogel after swelling with aqueous medium. Both the SAAP‐148‐modified polymer in solution and the photocrosslinked hydrogels show good antimicrobial activity against strains of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, including multidrug‐resistant strains, frequently found in wound infections. The covalent attachment of SAAP‐148 prevents leaching, ensuring sustained antimicrobial activity for at least 48 h in diluted human blood plasma and 14 days in PBS. This prolonged retention of antimicrobial activity in human blood plasma significantly enhances its clinical potential. Overall, this study shows the potential of the AMP‐functionalized photocrosslinkable polymer as antimicrobial wound dressings, providing an effective alternative to antibiotics. [ABSTRACT FROM AUTHOR]

Protein homeostasis in bacteria is regulated by proteases such as the tetradecameric caseinolytic protease P (ClpP). Although substrates of ClpP have been successfully deciphered in genetically engineered cells, methods which directly trap processed proteins within native cells remain elusive. Here, we introduce an in situ trapping strategy which utilizes trifunctional probes that bind to the active site serine of ClpP and capture adjacent substrates with an attached photocrosslinking moiety. After enrichment using an alkyne handle, substrate deconvolution by mass spectrometry (MS) is performed. We show that our two traps bind substoichiometrically to ClpP, retain protease activity, exhibit unprecedented selectivity for Staphylococcus aureus ClpP in living cells and capture numerous known and novel substrates. The exemplary validation of trapped hits using a targeted proteomics approach confirmed the fidelity of this technology. In conclusion, we provide a novel chemical platform suited for the discovery of serine protease substrates beyond genetic engineering. [ABSTRACT FROM AUTHOR]

Conjugative dissemination of mobile genetic elements (MGEs) among bacteria is initiated by assembly of the relaxosome at the MGE's origin‐of‐transfer (oriT) sequence. A critical but poorly defined step of relaxosome assembly involves recruitment of the catalytic relaxase to its DNA strand‐specific nicking site within oriT. Here, we present evidence by AlphaFold modeling, affinity pulldowns, and in vivo site‐directed photocrosslinking that the TraK Ribbon–Helix–Helix DNA‐binding protein recruits TraI to oriT through a dynamic interaction in which TraI's C‐terminal unstructured domain (TraICTD) wraps around TraK's C‐proximal tetramerization domain. Upon relaxosome assembly, conformational changes disrupt this contact, and TraICTD instead self‐associates as a prerequisite for relaxase catalytic functions or substrate engagement with the transfer channel. These findings delineate key early‐stage processing reactions required for conjugative dissemination of a model MGE. [ABSTRACT FROM AUTHOR]

This study explores a new eco-friendly approach for developing bioactive gelatin films using UV-C irradiation-induced photo-crosslinking. Riboflavin, a food-grade photoinitiator, was selected at an optimal concentration of 1.25% (w/w) for crosslinking gelatin under UV-C exposure for 4 to 22 min. Physicochemical analyses revealed enhanced tensile strength, reduced water vapor permeability, and lower water solubility in films crosslinked for up to 13 min. FTIR analysis demonstrated significant molecular changes, confirming the formation of crosslinking connections in gelatin–riboflavin films. Antimicrobial nanoemulsion (NE) (0.5, 0.75, 1% v/v) was incorporated into crosslinked films and applied to fresh beef. The 1% NE film exhibited the strongest antimicrobial effect, extending shelf-life by 20 days. In vitro release study confirmed Fickian diffusion behavior in the 1% NE film. This study also investigated the synergy between 1% NE film and three different types of modified atmosphere packaging (MAP) on the microbiological and physicochemical properties of beef for 26 days. The best results were achieved with 1% NE film under MAP1 and MAP2, which preserved meat redness and prevented lipid oxidation, extending the shelf-life up to 26 days. Therefore, UV-C irradiation-induced crosslinked bioactive film combined with high-oxygen MAP offers a promising solution for prolonging the shelf-life of beef. [ABSTRACT FROM AUTHOR]

Polymer blends containing up to 70% organosolv lignin content and lyotropic cellulose derivatives have been established as "lignin inks" for direct ink writing of fully biobased 3D parts. However, a fast-crosslinking mechanism is needed to improve throughput and design space. In this paper, UV-photocrosslinkable organosolv lignin/hydroxypropyl cellulose inks are formulated through doping with common photocrosslinkers. The most potent photocrosslinkers for neat hydroxypropyl cellulose, lignin and their blends are determined through a series of DOEs. Hydroxypropyl cellulose is significantly more amenable to photocrosslinking than organosolv lignin. The optimal photocrosslinkable ink formulations are printable and exhibit up to 70% gel content, although thermal post-curing remains essential. Chemical, thermal, and mechanical investigations of the photocrosslinked 3D parts evidence efficient crosslinking of HPC through its hydroxyl groups, while lignin appears internally plasticized and/or degraded during inefficient photocrosslinking. Despite this, photocrosslinkable inks exhibit improved tensile properties, shape flexibility, and fidelity. The heterogeneous crosslinking and residual creep highlight the need to further activate lignin for homogeneous photocrosslinking in order to fully exploit the potential of lignin inks in DIW. [ABSTRACT FROM AUTHOR]

Bacterial collagen, produced via recombinant DNA methods, offers advantages including consistent purity, customizable properties, and reduced allergy potential compared to animal‐derived collagen. Its controlled production environment enables tailored features, making it more sustainable, non‐pathogenic, and compatible with diverse applications in medicine, cosmetics, and other industries. Research has focused on the engineering of collagen‐like proteins to improve their structure and function. The study explores the impact of introducing tyrosine, an amino acid known for its role in fibril formation across diverse proteins, into a newly designed bacterial collagen‐like protein (Scl2), specifically examining its effect on self‐assembly and fibril formation. Biophysical analyses reveal that the introduction of tyrosine residues didn't compromise the protein's structural stability but rather promoted self‐assembly, resulting in the creation of nanofibrils—a phenomenon absent in the native Scl2 protein. Additionally, stable hydrogels are formed when the engineered protein undergoes di‐tyrosine crosslinking under light exposure. The hydrogels, shown to support cell viability, also facilitate accelerated wound healing in mouse fibroblast (NIH/3T3) cells. These outcomes demonstrate that the targeted inclusion of functional residues in collagen‐like proteins enhances fibril formation and facilitates the generation of robust hydrogels using riboflavin chemistry, presenting promising paths for research in tissue engineering and regenerative medicine. [ABSTRACT FROM AUTHOR]

[Display omitted] • Helical dendronized PPA homopolymers were synthesized, which showed characteristic thermoresponsive behavior and tunable helicities. • Thermally-induced assembly of these helical homopolymers was investigated, dependent on their worm-like molecular geometry and radial amphiphilicity. • Hexagonal chain packing was formed through thermal collapse of these dendronized homopolymers in water, simultaneously enhanced the supramolecular chirality. • In situ photo-crosslinking of the thermal aggregates from these dendronized homopolymers afforded hierarchical structures with high stability both in the morphologies and the memorized chiralities. • Photo-crosslinking of the thermal aggregates was happened within individual aggregates due to protection of the dendritic pendants. Supramolecular assembly of helical homopolymers to form stable chiral entities in water is highly valuable for creating chiral nanostructures and fabricating chiral biomaterials. Here we report on thermally induced supramolecular assembly of helical dendronized poly(phenylacetylene)s (PPAs) in aqueous solutions, and their in-situ photo-crosslinking at elevated temperatures to afford crosslinked nano-assemblies with hierarchical structures and stabilized helicities. These helical dendronized homopolymers carry cinnamate-cored dendritic oligoethylene glycol (OEG) pendants, which exhibit characteristic thermoresponsive behavior. Their thermal aggregation confers hexagonal packing of the polymer chains, and simultaneously resulting in enhancement of their chiralities. Assisted by radial amphiphilicity and worm-like molecular geometry, these dendronized PPAs form supramolecular twisted fibers, spheroid particles or toroids via thermal aggregation. Through UV photoirradiation above their cloud points (T cp s), cycloaddition of cinnamate moieties from the dendritic pendants promotes intermolecular crosslinking of dendronized PPA chains within the thermal aggregates, and simultaneously, the dynamic morphologies and supramolecular chirality from the dendronized PPAs through thermally induced aggregation can be fixed. In addition, photo-crosslinking can be occurred solely within individual aggregates due to the protection of densely packed dendritic OEGs. Therefore, various crosslinked assemblies from the dendronized homopolymers with tailorable morphologies and stabilized chirality are fabricated by tuning their thermally induced dynamic aggregations followed by in-situ photo-crosslinking. We believe that this work paves a convenient route to fabricate chiral assemblies with stabilized morphologies and fixed chiralities from dynamic helical homopolymers through intermolecular crosslinking, which can be promising for various chiral applications. [ABSTRACT FROM AUTHOR]

Chemical modification of messenger RNA (mRNA) has paved the way for advancing mRNA‐based therapeutics. The intricate process of mRNA translation in eukaryotes is orchestrated by numerous proteins involved in complex interaction networks. Many of them bind specifically to a unique structure at the mRNA 5′‐end, called 5′‐cap. Depending on the 5′‐terminal sequence and its methylation pattern, different proteins may be involved in the translation initiation and regulation, but a deeper understanding of these mechanisms requires specialized molecular tools to identify natural binders of mRNA 5′‐end variants. Here, a series of 8 new synthetic 5′‐cap analogs that allow the preparation of RNA molecules with photoreactive tags using a standard in vitro transcription reaction are reported. Two photoreactive tags and four different modification sites are selected to minimize potential interference with cap‐protein contacts and to provide complementary properties regarding crosslinking chemistry and molecular interactions. The tailored modification strategy allows for the generation of specific crosslinks with model cap‐binding proteins, such as eIF4E and Dcp2. The usefulness of the photoreactive cap analogs is also demonstrated for identifying the cap‐binding subunit in a multi‐protein complex, which makes them perfect candidates for further development of photoaffinity labeling probes to study more complex mRNA‐related processes. [ABSTRACT FROM AUTHOR]

Cataract is the leading cause of the blindness worldwide. Natural lens removal followed with intraocular lens (IOL) implantation is the main clinical treatment for cataract. However, the shape and the optical power of current IOLs were fixed, which were not favorable for patients, especially for children with congenital cataracts. An injectable IOL is an immerging replacement for a regular IOL due to the accommodation of external packing shapes. In this study, we developed a rapid, in situ gelation of an injectable photo-crosslinked hydrogel as an injectable IOL material. In this investigation, injectable hydrogel (G/D hydrogel) was fabricated from Gelatin methacrylate (GelMA) and N- (3, 4-dihydroxyphenylidene ethyl) methacrylamide (DMA) via photo-crosslinking for injectable IOL applications. Different preparation parameters such as the concentration, proportion, light intensity, and curing time were optimized based on the gelation time, swelling ratio, and mechanical properties of the produced G/D hydrogels. The results of in vitro cellular experiments showed that the G/D hydrogel had good and stable clearance of lens epithelial cells. The hydrogel was implanted into the eyes of the young rabbits for 1 month, and the results also showed that injectable G/D hydrogel can obtain good intraocular implants and have inhibitory effects on posterior capsular opacification. Thus such photo-crosslinked G/D hydrogel can serve as an injectable IOL application in cataract surgery. [ABSTRACT FROM AUTHOR]

Despite chronic fibrosis occurring in many pathological conditions, few in vitro studies examine how fibrosis impacts lymphatic endothelial cell (LEC) behavior. This study examined stiffening profiles of PhotoCol®—commercially available methacrylated type I collagen—photo-crosslinked with the photoinitiators: Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), Irgacure 2959 (IRG), and Ruthenium/Sodium Persulfate (Ru/SPS) prior to evaluating PhotoCol® permeability and LEC response to PhotoCol® at stiffnesses representing normal and fibrotic tissues. Ru/SPS produced the highest stiffness (~6 kilopascal (kPa)) for photo-crosslinked PhotoCol®, but stiffness did not change with burst light exposures (30 and 90 s). The collagen fibril area fraction increased, and dextran permeability (40 kilodalton (kDa)) decreased with photo-crosslinking, showing the impact of photo-crosslinking on microstructure and molecular transport. Human dermal LECs on softer, uncrosslinked PhotoCol® (~0.5 kPa) appeared smaller with less prominent vascular endothelial (VE)-cadherin (cell–cell junction) expression compared to LECs on stiffer PhotoCol® (~6 kPa), which had increased cell size, border irregularity, and VE-cadherin thickness (junction zippering) that is consistent with LEC morphology in fibrotic tissues. Our quantitative morphological analysis demonstrates our ability to produce LECs with a fibrotic phenotype, and the overall study shows that PhotoCol® with Ru/SPS provides the necessary physical properties to systematically study LEC responses related to capillary growth and function under fibrotic conditions. [ABSTRACT FROM AUTHOR]

Significant advancements have been achieved in polymer nanogel synthesis, yet there is a dearth of methods for easily preparing size‐adjustable, surface‐modifiable, and biocompatible nanogels. This study introduces a straightforward method for fabricating hyperbranched polyglycerol (HPG) nanogels in water through self‐assembly and disulfide bond crosslinking, avoiding the use of surfactants. The process involves modifying HPG with thioctic acid (TA) to create amphiphilic HPG‐TA rich in disulfide bonds, which is then reduced to facilitate water introduction and self‐assembly. Photocrosslinking is used to finalize the formation of HPG nanogels. These nanogels feature a uniform size distribution, with hydrodynamic diameters tunable from around 90 to 400 nm by tweaking synthesis variables. They have shown low cytotoxicity and high stability in aqueous media, with notable sensitivity to pH, especially in acidic conditions (e.g., pH 3), and redox‐responsiveness, as evidenced by reactions to 10 mM dithiothreitol (DTT). The nanogels' multiple hydroxyl groups enable easy functionalization, exemplified by the synthesis of fluorescent HPG‐RB nanogels. This work presents an efficient strategy for producing robust HPG nanogels, potentially spurring further advancements in the field of polymer nanogel synthesis and application. [ABSTRACT FROM AUTHOR]

Collagen crosslinking employing ultraviolet A rays and riboflavin (UVA/R) has emerged as a pivotal technique in clinical therapies, especially in ophthalmology since the 1990s. Despite its clinical adoption, the lack of clarity of the detailed mechanism and the imperative for a refined manufacturing process necessitates further investigation. This study advances the understanding of UVA/R crosslinked collagen, concentrating on identifying the primary crosslinking sites using seven synthetic peptides and exploring the pathways of riboflavin‐mediated crosslinking. The results demonstrate that tyrosine residues are key crosslinking sites, and riboflavin plays a dual role as both a catalyst and a competitive inhibitor in the crosslinking process. Furthermore, the UVA/R crosslinked collagen matrix exhibits a more harmonious balance between stability and degradability compared with chemically crosslinked collagen matrices, coupled with superior mechanical properties and augmented biocompatibility. In vivo experiments further validate its excellent biocompatibility, reduced tissue inflammation, and promotion of tissue regeneration. The research provides crucial insights into collagen crosslinking mechanisms, paving the way for the development of sophisticated collagen‐based biomaterials tailored for biomedical applications. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) bioprinting using photocrosslinkable hydrogels has gained considerable attention due to its versatility in various applications, including tissue engineering and drug delivery. Egg White (EW) is an organic biomaterial with excellent potential in tissue engineering. It provides abundant proteins, along with biocompatibility, bioactivity, adjustable mechanical properties, and intrinsic antiviral and antibacterial features. Here, a photocrosslinkable hydrogel derived from EW is developed through methacryloyl modification, resulting in Egg White methacryloyl (EWMA). Upon exposure to UV light, synthesized EWMA becomes crosslinked, creating hydrogels with remarkable bioactivity. These hydrogels offer adjustable mechanical and physical properties compatible with most current bioprinters. The EWMA hydrogels closely resemble the native extracellular matrix (ECM) due to cell‐binding and matrix metalloproteinase‐responsive motifs inherent in EW. In addition, EWMA promotes cell growth and proliferation in 3D cultures. It facilitates endothelialization when investigated with human umbilical vein endothelial cells (HUVECs), making it an attractive replacement for engineering hemocompatible vascular grafts and biomedical implants. In summary, the EWMA matrix enables the biofabrication of various living constructs. This breakthrough enhances the development of physiologically relevant 3D in vitro models and opens many opportunities in regenerative medicine. [ABSTRACT FROM AUTHOR]

The miniaturization and high-power density of modern electronic devices pose significant thermal management issues, particularly affecting their performance and lifetime. Ladder-like polysilsesquioxanes (LPSQs) offer a promising solution due to their remarkable thermal, mechanical, and chemical properties. By incorporating thermally conductive fillers, LPSQ composites can achieve high thermal conductivity (TC), making them ideal for thermal management in advanced electronic applications. In this study, LPSQ-based nanocomposites containing functionalized alumina nanoparticles were prepared by solution casting and UV curing, and the effects of varying amounts of Irgacure-184 photoinitiator on their structural and thermal properties were investigated. Three sets of samples were prepared with a fixed amount of LPSQs, 80 wt.% of nanoparticles, and 1, 5, or 10 wt.% of photoinitiator with respect to the matrix. TC was evaluated from the measured values of heat capacity, density, and thermal diffusivity. TC values increased by 60%, 71.2%, and 93.1% for the three samples, respectively, compared to the neat matrix. Results indicate that an intermediate amount of photoinitiator (5%) preserved LPSQs' structural integrity, namely the presence of long linear silsesquioxane chains, and provided good filler dispersion and distribution, high polymerization degree, thermal stability, and high TC. [ABSTRACT FROM AUTHOR]

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 365 nm. 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. [ABSTRACT FROM AUTHOR]

Oleuropein-loaded photocrosslinked hydrogels, consisting of methacrylated pectin (PEC-MA) and methacrylated hyaluronic acid (HA-MA), were developed as a new hydrogel wound dressing. Pectin and hyaluronic acid were methacrylated and the composite hydrogels were developed by photocrosslinking of the methacrylated polymer precursors. Methacrylation and the photocrosslinking reactions were approved by 1H-NMR and FTIR analyses. In addition to thermal and morphological characterizations, swelling and in vitro degradation studies were performed. More importantly, bioactivity studies, such as cytotoxicity, genotoxicity and hemolysis were performed to reveal the potential of the oleuropein-loaded photocrosslinked hybrid hydrogels for wound dressing applications. In vitro scratch assay studies showed that oleuropein-loaded wound dressing effectively promoted the wound healing compared to the control in 24 hrs. Oleuropein-loaded photocrosslinked hydrogels had no genotoxic and cytotoxic effects on L929 cells and could have a potential for wound healing applications. [ABSTRACT FROM AUTHOR]

Thermoresponsive hydrogels were 3D-printed with embedded gold nanorods (GNRs), which enable shape change through photothermal heating. GNRs were functionalized with bovine serum albumin and mixed with a photosensitizer and poly(N-isopropylacrylamide) (PNIPAAm) macromer, forming an ink for 3D printing by direct ink writing. A macromer-based approach was chosen to provide good microstructural homogeneity and optical transparency of the unloaded hydrogel in its swollen state. The ink was printed into an acetylated gelatin hydrogel support matrix to prevent the spreading of the low-viscosity ink and provide mechanical stability during printing and concurrent photocrosslinking. Acetylated gelatin hydrogel was introduced because it allows for melting and removal of the support structure below the transition temperature of the crosslinked PNIPAAm structure. Convective and photothermal heating were compared, which both triggered the phase transition of PNIPAAm and induced reversible shrinkage of the hydrogel–GNR composite for a range of GNR loadings. During reswelling after photothermal heating, some structures formed an internally buckled state, where minor mechanical agitation recovered the unbuckled structure. The BSA-GNRs did not leach out of the structure during multiple cycles of shrinkage and reswelling. This work demonstrates the promise of 3D-printed, photoresponsive structures as hydrogel actuators. [ABSTRACT FROM AUTHOR]

The design of lignin nanostructures where interfacial interactions enable enhanced entanglement of colloidal networks can broaden their applications in hydrogel‐based materials and light‐based 3D printing. Herein, an approach for fabricating surface‐active dendritic colloidal microparticles (DCMs) characterized by fibrous structures using nanostructured allylated lignin is proposed for the development of lignin‐based photocurable resins. With allyl‐terminated surface functionality of 0.61 mmol g−1, the entanglement between lignin‐DCM fibrils with a size of 1.4 µm successfully produces only lignin‐based hydrogels with structural integrity through photo‐crosslinking. The colloidal network of lignin dendricolloids reinforces the poly(ethylene glycol) (PEG) hydrogels during a digital light processing (DLP) 3D printing process by generating bicontinuous morphologies, resulting in six‐fold increases in toughness values with respect to the neat PEG hydrogel. The dual effectiveness of photoabsorption and free‐radical reactivity of lignin‐DCMs allow the light‐patterning of rather dilute PEG hydrogels (5–10%) with high geometric fidelity and structural complexity via DLP 3D printing. This study demonstrates a green and effective strategy for the design of 1D lignin‐DCMs that increases the versatility of the nanostructured biopolymer, opening up numerous opportunities for formulating functional hydrogels with robust structure‐property correlations. [ABSTRACT FROM AUTHOR]

Silk fibroin hydrogels are extensively explored for tissue engineering and regenerative medicine as an artificial extracellular matrix (ECM) that can support tissue growth. However, the nanometer pore size of hydrogels limits adequate cell, tissue, and vascular infiltration. Microgel scaffolds are an emerging class of microporous biomaterials formed by annealing small microscale hydrogels (microgels) into a 3D construct. In this work, silk microgels are generated using a microfluidic device that allows tuning of the microgel diameter (100–400 µm) and are stabilized via visible light‐initiated photo‐crosslinking of native tyrosine residues in silk. Microgels are then covalently annealed using silk solution as glue and the same cytocompatible visible light‐initiated crosslinking to form microgel scaffolds. Unlike the nano‐porosity of bulk photo‐crosslinked silk hydrogels, the microgel scaffolds have an average pore diameter of 29 ± 17 or 192 ± 81 µm depending on the microgel size, with enhanced mechanical properties compared to bulk hydrogels. This microporosity supports enhanced cell spreading and proliferation in vitro and increases scaffold remodeling in vivo, encouraging improved tissue infiltration and matrix deposition. The microgel size and material format also affect inflammatory responses in vivo. This work demonstrates that silk microgels and microgel scaffolds are promising candidates for tissue engineering and regenerative medicine applications. [ABSTRACT FROM AUTHOR]

The diverse biomolecular landscape of tissue-specific decellularized extracellular matrix (dECM) biomaterials provides a multiplicity of bioinstructive cues to target cells, rendering them highly valuable for various biomedical applications. However, the isolation of dECM biomaterials entails cumbersome xenogeneic enzymatic digestions and also additional inactivation procedures. Such, increases processing time, increments costs and introduces residues of non-naturally present proteins in dECM formulations that remain present even after inactivation. To overcome these limitations, herein we report an innovative conjugation of light and ultrasound-mediated dECM biomaterial processing for fabricating dECM biomaterials. Such approach gathers on ultrasound waves to facilitate dECM-in-liquid processing and visible light photocrosslinking of tyrosine residues naturally present in dECM biomaterials. This dual step methodology unlocked the in-air production of cell laden dECM hydrogels or programmable dECM hydrogel spherical-like beads by using superhydrophobic surfaces. These in-air produced units do not require any additional solvents and successfully supported both fibroblasts and breast cancer cells viability upon encapsulation or surface seeding. In addition, the optimized photoacoustic methodology also enabled a rapid formulation of dECM biomaterial inks with suitable features for biofabricating volumetrically defined living constructs through embedded 3D bioprinting. The biofabricated dECM hydrogel constructs supported cell adhesion, spreading and viability for 7 days. Overall, the implemented photoacoustic processing methodology of dECM biomaterials offers a rapid and universal strategy for upgrading their processing from virtually any tissue. Leveraging decellularized extracellular matrix (dECM) as cell instructive biomaterials has potential to open new avenues for tissue engineering and in vitro disease modelling. The processing of dECM remains however, lengthy, costly and introduces non-naturally present proteins in the final biomaterials formulations. In this regard, here we report an innovative light and ultrasound two-step methodology that enables rapid dECM-in-liquid processing and downstream photocrosslinking of dECM hydrogel beads and 3D bioprinted constructs. Such photoacoustic based processing constitutes a universally applicable method for processing any type of tissue-derived dECM biomaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

While photo-cross-linking (PXL) with alkyl diazirines can provide stringent distance restraints and offer insights into protein structures, unambiguous identification of cross-linked residues hinders data interpretation to the same level that has been achieved with chemical cross-linking (CXL). We address this challenge by developing an in-line system with systematic modulation of light intensity and irradiation time, which allows for a quantitative evaluation of diazirine photolysis and photo-reaction mechanism. Our results reveal a two-step pathway with mainly sequential generation of diazo and carbene intermediates. Diazo intermediate preferentially targets buried polar residues, many of which are inaccessible with known CXL probes for their limited reactivity. Moreover, we demonstrate that tuning light intensity and duration enhances selectivity towards polar residues by biasing diazo-mediated cross-linking reactions over carbene ones. This mechanistic dissection unlocks the full potential of PXL, paving the way for accurate distance mapping against protein structures and ultimately, unveiling protein dynamic behaviors. Photo-cross-linking (PXL) with alkyl diazirines can provide stringent distance restraints and offer insights into protein structures, but unambiguous identification of cross-linked residues hinders data interpretation. Here, the authors report a quantitative analysis of alkyl diazirine photo-cross-linking reactions and reveal a two-step mechanism, enabling selective targeting of buried polar residues. [ABSTRACT FROM AUTHOR]

Biomimetic and thermoresponsive hemostatic hydrogels based on gelatin (G), hyaluronic acid (HA), and poly-N-isopropylacrylamide (PNIPAM) have emerged as promising hemostats, but their performances are currently limited by the drawbacks of conventional grafting strategies, and the complicated operation and safety risk associated with photo-cross-linking or chemical cross-linking. It is highly appealing yet challenging to develop a facile strategy to prepare a physically cross-linked hemostatic hydrogel with rapid gelation and a robust network. Herein, an injectable, thermosensitive, and physically cross-linked double-network hemostatic hydrogel was prepared through simply blending G/HA with the linear PNIPAM (L-P) synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The G/HA/L-P hydrogel could be conveniently injected via a syringe and cured in situ at body temperature. Its comprehensive performance could be tuned and optimized by adjusting the molecular weight of L-P and the proportions of components. Due to the non-covalent interactions including hydrogen bonding, hydrophobic interactions, and chain entanglements within the hydrogel network, the optimal performance of the G/HA/L-P hydrogel was achieved, i.e., gelation time 7–10 s, storage modulus 89 ± 3.5 kPa, adhesion strength 19.3 ± 2.5 kPa, and burst pressure 256 ± 27 mmHg. Meanwhile, the hydrogel exhibited significant coagulation effects in vitro and effective hemostatic properties in vivo. This work offers a simple and efficient strategy to fabricate high-performance smart hemostatic hydrogels. [ABSTRACT FROM AUTHOR]

3D‐printed cell‐laden hydrogels as tissue constructs show great promise in generating living tissues for medicine. Currently, the maturation of 3D‐printed constructs into living tissues remains challenge, since commonly used hydrogels struggle to provide an ideal microenvironment for the seeded cells. In this study, a cell‐adaptable nanocolloidal hydrogel is created for 3D printing of maturable tissue constructs. The nanocolloidal hydrogel is composed of interconnected nanoparticles, which is prepared by the self‐assembly and subsequent photocrosslinking of the gelatin methacryloyl solutions. Cells can get enough space to grow and migrate within the hydrogel through squeezing the flexible nanocolloidal networks. Meanwhile, the nanostructure can promote the seeded cells to proliferate and produce matrix proteins through mechanotransduction. Using digital light process‐based 3D printing technology, it can rapidly customize cartilage tissue constructs. After implantation, these tissue constructs efficiently matured into cartilage tissues for the articular cartilage defect repair and ear cartilage reconstruction in vivo. The 3D printing of maturable tissue constructs using the nanocolloidal hydrogel shows potential for future clinical applications. [ABSTRACT FROM AUTHOR]

This article explores the synthesis of methyl-substituted psoralen derivatives and their potential for DNA photocrosslinking. Psoralen is a natural compound used in skin disease treatment, but it can have toxic and mutagenic effects. The researchers aimed to enhance the reactivity of psoralen and control crosslinked product formation by adding methyl substituents at specific positions. They developed a synthetic method for creating psoralen derivatives and tested their photocrosslinking abilities with DNA. The results showed that the presence of methyl substituents reduced the formation of harmful diadducts. The article suggests further research to explore different psoralen derivatives and investigate their photocrosslinking properties. [Extracted from the article]

New gelatin methacryloyl (GelMA)—strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair. [ABSTRACT FROM AUTHOR]

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Abstract Photoalignment technology is serving as an emerging technology for programming liquid crystalline polymer (LCP) materials due to its advantages including noncontact, high resolution, spatial control, programmability, and high efficiency. In this review, we report the research progress in implementing polarized light to design the anisotropy of LCPs, which is categorized based on the photoalignment mechanisms. The alignment approaches and the different stimulus‐responsive behaviors of the materials after photoalignment are discussed. Additionally, we have summarized the applications of photoaligned LCPs such as liquid crystal displays, optical components, intelligent soft actuators, and beyond. Finally, the challenges and future directions of the technology are outlined.

A pioneering method is reported for creating thermoresponsive biofunctional hydrogel microstructures using maskless multiphoton lithography. Departing from conventional multiphoton‐triggered polymerization‐based techniques, this approach relies on simultaneous photocrosslinking and attachment of already pre‐synthesized polymer chains onto solid substrates. The method allows improving control over polymer network characteristics and enables facile integration of additional functionalities through postmodification with biomolecules at specific sites. Exploring two distinct benzophenone‐ and anthraquinone‐based photocrosslinkers incorporated into specially designed poly(N‐isopropyl acrylamide)‐based co‐ and terpolymers, the photocrosslinking efficacy is scrutinized with the use of a custom femtosecond near‐infrared laser lithographer. Comprehensive characterization via surface plasmon resonance imaging, atomic force microscopy, and optical fluorescence microscopy reveals swelling behavior and demonstrates postmodification feasibility. Notably, within a specific range of multiphoton photocrosslinking parameters, the surface‐attached microstructures exhibit a quasiperiodic topography akin to wrinkle‐pattern formation. Leveraging the capabilities of established multiphoton lithographer systems that offer fast pattern writing with high resolution, this approach holds great promise for the versatile fabrication of multifunctional 3D micro‐ and nanostructures. Such tailored responsive biofunctional materials with spatial control over composition, swelling behavior, and postmodification are particularly attractive in the areas of bioanalytical and biomedical technologies. [ABSTRACT FROM AUTHOR]

Over the past decade, molecular‐switch‐embedded memory devices, particularly field‐effect transistors (FETs), have gained significant interest. Molecular switches are integrated to regulate the resistance or current levels in FETs. Despite substantial efforts, realizing large memory window with a long retention time, a critical factor in memory device functionality, remains a challenge. This is due to the inability of an isomeric state of a molecular switch to serve as a stable deep trap state within the semiconductor layer. Herein, the study addresses this limitation by introducing chemical bonding between molecular switch and conjugated polymeric semiconductor, facilitating closed isomer of diarylethene (DAE) to operate as a morphologically stable deep trap state. Azide‐ and diazirine‐anchored DAEs are synthesized, which form chemical bonds to the polymer through photocrosslinking, thereby implementing permanent and controllable trapping states nearby conjugated backbone of polymer semiconductor. Consequently, when diazirine‐anchored DAE is blended with F8T2 and subjected to photocrosslinking, the resulting organic FETs exhibit remarkable memory performance, including a memory window of 22 V with a retention time over 106 s, a high photoprogrammable on/off ratio over 103, and a high operational stability over 100 photocycles. Further, photophore‐anchored DAEs can achieve precise patterning, which enables meticulous control over the semiconductor layer structure. [ABSTRACT FROM AUTHOR]

This manuscript aims to three‐dimensional bioprint and evaluate new polymer composite scaffolds based on synthesized poly(ethylene glycol) dimethacrylate (PEGDMA) as well as methyl cellulose and gelatin. The PEGDMA was synthesized by a simple microwave‐assisted method using three distinct molecular weights (MWs) of poly(ethylene glycol) (PEG), 3, 6, and 12 kDa, and methacrylic anhydride. The percent functionalization of the PEGDMA was analyzed using the nuclear magnetic resonance spectrum, and the theoretical calculations indicated that over 50% of methacrylation was achieved in all samples, with the PEGDMA synthesized from 6 kDa PEG surpassing 66% methacrylation. These three PEGDMA‐based bioinks were investigated for their suitability for bioprinting scaffolds. It was observed that lower MW PEGDMA resulted in a higher degree of crosslinking, leading to more stable composite scaffolds. However, higher crosslinking degree did not support long‐term cell viability when encapsulated with cells. Higher MW PEGDMA showed higher cell viability over time though overall stability was lower. Synthesized PEGDMA with 6 kDa PEG showed both stability and long‐term cell viability after postprinting. Over 80% of cell viability was maintained for a 7‐day study period, showing potential use in tissue engineering applications as a cell delivery vehicle. [ABSTRACT FROM AUTHOR]

Although several technologies have been developed to isolate cells of interest from a heterogenous sample, clogging and impaired cell viability limit such isolation. We have developed the Enrich TROVO system as a novel, nonfluidic technology to sort live cells. The TROVO system combines imaging-based cell selection and photo-crosslinking of (gelatin methacrylate) gelMA-hydrogel to capture cells. After capture, cells are released by enzymatic digestion of the hydrogel and then retrieved for downstream analysis or further cell culturing. The system can capture cells with a recovery rate of 48% while maintaining 90% viability. Moreover, TROVO can enrich rare cells 506-fold with 93% efficiency using single step isolation from a 1:104 cell mixture, and can also capture one target cell from 1 million cells, reaching an enrichment ratio of 9128. In addition, 100% purity and 49% recovery rate can be achieved by a following negative isolation process. Compared to existing technologies, the TROVO system is clog-resistant, highly biocompatible, and can process a wide range of sample sizes. • A fluidics free platform to isolate rare cells from complicated samples. • Touchless, high throughput capture via parallel micro light beams. • Image based phenotypes used as sorting criteria. • Flexible isolation strategies such as positive and negative capture. • CTCs, cell pools, cell-cell interaction events can be visualized and isolated. [ABSTRACT FROM AUTHOR]

Efferocytosis, an intrinsic regulatory mechanism to eliminate apoptotic cells, will be suppressed due to the delayed apoptosis process in aging‐related diseases, such as osteoarthritis (OA). In this study, cartilage lesion‐localized hydrogel microspheres are developed to remodel the in situ efferocytosis to reverse cartilage senescence and recruit endogenous stem cells to accelerate cartilage repair. Specifically, aldehyde‐ and methacrylic anhydride (MA)‐modified hyaluronic acid hydrogel microspheres (AHM), loaded with pro‐apoptotic liposomes (liposomes encapsulating ABT263, A‐Lipo) and PDGF‐BB, namely A‐Lipo/PAHM, are prepared by microfluidic and photo‐cross‐linking techniques. By a degraded porcine cartilage explant OA model, the in situ cartilage lesion location experiment illustrated that aldehyde‐functionalized microspheres promote affinity for degraded cartilage. In vitro data showed that A‐Lipo induced apoptosis of senescent chondrocytes (Sn‐chondrocytes), which can then be phagocytosed by the efferocytosis of macrophages, and remodeling efferocytosis facilitated the protection of normal chondrocytes and maintained the chondrogenic differentiation capacity of MSCs. In vivo experiments confirmed that hydrogel microspheres localized to cartilage lesion reversed cartilage senescence and promoted cartilage repair in OA. It is believed this in situ efferocytosis remodeling strategy can be of great significance for tissue regeneration in aging‐related diseases. [ABSTRACT FROM AUTHOR]

Photoclick reactions combine the advantages offered by light‐driven processes and classical click chemistry and have found applications ranging from surface functionalization, polymer conjugation, photo‐crosslinking, and protein labeling. Despite these advances, the dependency of most of the photoclick reactions on UV light poses a severe obstacle for their general implementation, as this light can be absorbed by other molecules in the system resulting in their degradation or unwanted reactivity. However, the development of a simple and efficient system to achieve bathochromically shifted photoclick transformations remains challenging. Here, we introduce triplet‐triplet energy transfer as a fast and selective way to enable visible light‐induced photoclick reactions. Specifically, we show that 9,10‐phenanthrenequinones (PQs) can efficiently react with electron‐rich alkenes (ERAs) in the presence of a catalytic amount (as little as 5 mol %) of photosensitizers. The photocycloaddition reaction can be achieved under green (530 nm) or orange (590 nm) light irradiation, representing a bathochromic shift of over 100 nm as compared to the classical PQ‐ERAs system. Furthermore, by combining appropriate reactants, we establish an orthogonal, blue and green light‐induced photoclick reaction system in which the product distribution can be precisely controlled by the choice of the color of light. [ABSTRACT FROM AUTHOR]

DNA nanomaterials have been widely employed for various biomedical applications. With rapid development of chemical modification of nucleic acid, serials of stimuli‐responsive elements are included in the multifunctional DNA nanomaterials. In this review, we summarize the recent advances in light responsive DNA nanomaterials based on photocleavage/photodecage, photoisomerization, and photocrosslinking for efficient bioimaging (including imaging of small molecule, microRNA, and protein) and drug delivery (including delivery of small molecule, nucleic acid, and gene editing system). We also discuss the remaining challenges and future perspectives of the light responsive DNA nanomaterials in biomedical applications. [ABSTRACT FROM AUTHOR]

Glycans on tumor cell surface have significant impacts in the immune‐killing process. Here an ultra‐galactocation to sialic acid (Sia) strategy is designed to hugely introduce galactose (Gal) to Sia and on tumor cells in vivo by using a penta‐functional dendritic probe (Den@5F), which efficiently enhances the immune‐killing of tumor cells. The Den@5F contains five different kinds of functional groups, including Gal, Cy5, amino, phenylboronic acid (PBA) and 4‐(4‐(hydroxymethyl)‐2‐methoxy‐5‐nitrophenoxy) butanoate (mNB), which can be conveniently prepared through a two‐step reaction. After injecting into the tumor‐bearing mouse, Den@5F can efficiently block Sia through the specific recognition between PBA and Sia on tumor cells and hugely introduce Gal through the subsequent photo‐crosslinking between mNB and amino groups to multiply conjugate excessive Den@5Fs. The comprehensively blocked Sia can prevent the immune escape, and the hugely introduced Gal can promote the immune stimulation of the immune cells, which lead to an efficient enhancement of the immune‐killing. The proposed strategy provides a significant and promising tool to promote the clinical immunotherapy of tumor. [ABSTRACT FROM AUTHOR]

The highly porous morphology of chitosan cryogels, with submicrometric-sized pore cell walls, provides a large surface area which leads to fast water absorption and elevated swelling degrees. These characteristics are crucial for the applications of nitric oxide (NO) releasing biomaterials, in which the release of NO is triggered by the hydration of the material. In the present study, we report the development of chitosan cryogels (CS) with a porous structure of interconnected cells, with wall thicknesses in the range of 340–881 nm, capable of releasing NO triggered by the rapid hydration process. This property was obtained using an innovative strategy based on the functionalization of CS with two previously synthesized S-nitrosothiols: S-nitrosothioglycolic acid (TGA(SNO)) and S-nitrosomercaptosuccinic acid (MSA(SNO)). For this purpose, CS was previously methacrylated with glycidyl methacrylate and subsequently submitted to photocrosslinking and freeze-drying processes. The photocrosslinked hydrogels thus obtained were then functionalized with TGA(SNO) and MSA(SNO) in reactions mediated by carbodiimide. After functionalization, the hydrogels were frozen and freeze-dried to obtain porous S-nitrosated chitosan cryogels with high swelling capacities. Through chemiluminescence measurements, we demonstrated that CS-TGA(SNO) and CS-MSA(SNO) cryogels spontaneously release NO upon water absorption at rates of 3.34 × 10−2 nmol mg−1 min−1 and 1.27 × 10−1 nmol mg−1 min−1, respectively, opening new perspectives for the use of CS as a platform for localized NO delivery in biomedical applications. [Display omitted] • Chitosan cryogels feature sub-micrometric sized pore cell walls for fast water absorption. • Innovative functionalization with S-nitrosothiol groups enables controlled nitric oxide release. • Chemiluminescence measurements confirm spontaneous NO release from S-nitrosated chitosan cryogels. • Potential applications include localized NO release from bodily fluid absorption. [ABSTRACT FROM AUTHOR]

Polymer network materials are interesting alternatives to thermoplastic polymers. Here, the preparation of polymer capsules is investigated, which are made from poly(ε‐caprolactone) (PCL) networks and are compartmentalized in a crosslinked PCL shell and a core that is suitable to enclose payloads of interest. Aided by microfluidic templating, PCL network capsules with a narrow size distribution (176 ± 5 µm) and thin shells (≈7.5 µm) are formed from 4‐arm star‐shaped 12 kDa PCL precursors by photoinitiator‐free UV light‐induced radical polymerization of methacrylate end‐groups. FITC‐BSA is encapsulated as a model protein. The physicochemical characterization of the capsules indicated a partial crosslinking of methacrylate endgroups into netpoints. Microscopy revealed a fraction of collapsed capsules that are discussed in the context of network stability and mechanical stress created at the capsule interfaces during solvent removal. The incubation of particles with human embryonic kidney (HEK) cells showed good cell compatibility, suggesting their potential use in biosciences and beyond. [ABSTRACT FROM AUTHOR]

In tissue engineering, crosslinking with carbodiimides such as EDC is omnipresent to improve the mechanical properties of biomaterials. However, in collagen biomaterials, EDC reacts with glutamate or aspartate residues, inactivating the binding sites for cellular receptors and rendering collagen inert to many cell types. In this work, we have developed a crosslinking method that ameliorates the rigidity, stability, and degradation rate of collagen biomaterials, whilst retaining key interactions between cells and the native collagen sequence. Our approach relies on the UV-triggered reaction of diazirine groups grafted on lysines, leaving critical amino acid residues intact. Notably, GxxGER recognition motifs for collagen-binding integrins, ablated by EDC crosslinking, were left unreacted, enabling cell attachment, spreading, and colonization on films and porous scaffolds. In addition, our procedure conserves the architecture of biomaterials, improves their resistance to collagenase and cellular contraction, and yields material stiffness akin to that obtained with EDC. Importantly, diazirine-crosslinked collagen can host mesenchymal stem cells, highlighting its strong potential as a substrate for tissue repair. We have therefore established a new crosslinking strategy to modulate the mechanical features of collagen porous scaffolds without altering its biological properties, thereby offering an advantageous alternative to carbodiimide treatment. This article describes an approach to improve the mechanical properties of collagen porous scaffolds, without impacting collagen's natural interactions with cells. This is significant because collagen crosslinking is overwhelmingly performed using carbodiimides, which results in a critical loss of cellular affinity. By contrast, our method leaves key cellular binding sites in the collagen sequence intact, enabling cell-biomaterial interactions. It relies on the fast, UV-triggered reaction of diazirine with collagen, and does not produce toxic by-products. It also supports the culture of mesenchymal stem cells, a pivotal cell type in a wide range of tissue repair applications. Overall, our approach offers an attractive option for the crosslinking of collagen, a prominent material in the growing field of tissue engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonic acid), abbreviated as PEDOT:PSS, is widely used in light-emitting diodes, solar cells, sensors, and other functional devices due to its high conductivity, transparency, and solution processability. In this study, the photo-reactive cross-linking agent 2,4-hexadiyne-1,6-diol (HOD) was introduced for a comparative study of photo-crosslinking in PEDOT:PSS AI 4083 (denoted as 4083) and PEDOT:PSS PH1000 (denoted as PH1000). The results showed that the aggregation state of 4083 was different from that of PH1000, ascribed to the composition of 4083 and PH1000 and the mechanism of the photo-crosslinking agent. Based on these findings, quantum dot light-emitting diode (QLED) devices were fabricated using direct photo-crosslinking PH1000. The work function based on PH1000 as a hole-injected layer (HIL) was increased from 5.03 eV to 5.22 eV, and the external quantum efficiency (EQE) was increased from 17.2% to 18.9%. This result provided a feasible solution for the application of PH1000 in high-performance QLED displays. [ABSTRACT FROM AUTHOR]

We herein report a method for site‐selective photo‐crosslinking of a DNA duplex. A stilbene pair was introduced into a DNA duplex and a ruthenium complex was conjugated with a triplex‐forming oligonucleotide. We demonstrated that [2+2] photocycloaddition of the stilbene pair occurred upon irradiation with visible light when the ruthenium complex was in close proximity due to triplex formation. No reaction occurred when the ruthenium complex was not in proximity to the stilbene pair. The wavelength of visible light used was of lower energy than the wavelength of UV light necessary for direct excitation of stilbene. Quantum chemical calculation indicated that ruthenium complex catalyzed the photocycloaddition via triplet‐triplet energy transfer. Site selectivity of this photo‐crosslinking system was evaluated using a DNA duplex bearing two stilbene pairs as a substrate; we showed that the site of crosslinking was precisely regulated by the sequence of the oligonucleotide linked to the ruthenium complex. Since this method does not require orthogonal photoresponsive molecules, it will be useful in construction of complex photoresponsive DNA circuits, nanodevices and biological tools. [ABSTRACT FROM AUTHOR]

The envelope of Escherichia coli contains approximately 100 different species of lipoproteins, most of which are localized to the inner leaflet of the outer membrane. The localization of lipoprotein (Lol) system, consisting of five Lol proteins, is responsible for the trafficking of lipoproteins to the outer membrane. LolCDE binds to lipoproteins destined for the outer membrane and transfers them to the periplasmic chaperone LolA. Although the cryo-EM structures of E. coli LolCDE have been reported, the mechanisms by which outer membrane lipoproteins are transferred to LolA remain elusive. In this study, we investigated the interaction between LolCDE and lipoproteins using site-specific photo-crosslinking. We introduced a photo-crosslinkable amino acid into different locations across the four helices which form the central lipoprotein-binding cavity, and identified domains that crosslink with peptidoglycan-associated lipoprotein (Pal) in vivo. Using one of the derivatives containing the photo-crosslinkable amino acid, we developed an in vitro system to analyze the binding of lipoproteins to LolCDE. Our results indicate that compound 2, a LolCDE inhibitor, does not inhibit the binding of lipoproteins to LolCDE, but rather promotes the dissociation of bound lipoproteins from LolCDE. [ABSTRACT FROM AUTHOR]

Abstract Chemical modification of messenger RNA (mRNA) has paved the way for advancing mRNA‐based therapeutics. The intricate process of mRNA translation in eukaryotes is orchestrated by numerous proteins involved in complex interaction networks. Many of them bind specifically to a unique structure at the mRNA 5′‐end, called 5′‐cap. Depending on the 5′‐terminal sequence and its methylation pattern, different proteins may be involved in the translation initiation and regulation, but a deeper understanding of these mechanisms requires specialized molecular tools to identify natural binders of mRNA 5′‐end variants. Here, a series of 8 new synthetic 5′‐cap analogs that allow the preparation of RNA molecules with photoreactive tags using a standard in vitro transcription reaction are reported. Two photoreactive tags and four different modification sites are selected to minimize potential interference with cap‐protein contacts and to provide complementary properties regarding crosslinking chemistry and molecular interactions. The tailored modification strategy allows for the generation of specific crosslinks with model cap‐binding proteins, such as eIF4E and Dcp2. The usefulness of the photoreactive cap analogs is also demonstrated for identifying the cap‐binding subunit in a multi‐protein complex, which makes them perfect candidates for further development of photoaffinity labeling probes to study more complex mRNA‐related processes.

This work compares the delamination behavior of epoxy CFRPs nano‐modified with nitrile butadiene rubber/polyethylene oxide (NBR/PEO) blend nanofibrous membranes with a rubber content of 70 wt%. While the electrospun mat is able to retain the nanofibrous structure even without crosslinking, photocrosslinking is also carried to evaluate the potential different efficacy on the delamination hindering. Double cantilever beam (DCB) and end‐notched flexure (ENF) tests show significant improvements of the energy release rates (G) both in Mode I (up to ≈4 times) and Mode II (up to ≈1.5 times). In particular, the presence of "liquid" rubber (uncrosslinked mat) leads to the best reinforcing action in Mode I, while the crosslinked membrane gives the highest delamination hindering in Mode II. [ABSTRACT FROM AUTHOR]

Pluronic F127 dimethacrylate (F127-DM) inks exhibit potential for 3D printing biomaterials due to their combined gelation and photo-crosslinking capabilities. Previous studies have explored their application in extrusion 3D printing of medical devices, relying on their long-range micellar ordering to impart mechanical stability, stretchability, and control over drug delivery. However, there is a lack of information regarding the impact of the extrusion and photo-crosslinking processes on the micellar ordering of F127-DM. Herein, we employed in operando 3D printing synchrotron small-angle X-ray scattering (SAXS) to analyze the influence of various printing parameters, including nozzle shape, nozzle size, extrusion rate, ink composition, and photo-crosslinking, on the micellar ordering of F127-DM. Our findings from 2D SAXS patterns indicate orientation of the micellar packing clusters along the flow direction. The nozzle diameter and shape emerged as crucial parameters, leading to increased disruption of long-range ordering. Furthermore, 1D SAXS curves during UV-Vis light exposure and photo-crosslinking revealed a partial preservation of the micellar packing structure, with cluster size reduction, and coexisting with randomly distributed micelles and unimers. These results underscore the importance of in operando synchrotron experiments for the systematic study of 3D printing parameters from a nanostructure perspective. [ABSTRACT FROM AUTHOR]

Sphingolipid dysregulation is involved in a range of rare and fatal diseases as well as common pathologies including cancer, infectious diseases or neurodegeneration. Gaining insights into how sphingolipids are involved in these diseases would contribute much to our understanding of human physiology, as well as the pathology mechanisms. However, scientific progress is hampered by a lack of suitable tools that can be used in intact systems. To overcome this, efforts have turned to engineering modified lipids with small clickable tags and to harnessing the power of click chemistry to localize and follow these minimally modified lipid probes in cells. We hope to inspire the readers of this Review to consider applying existing click chemistry tools for their own aspects of sphingolipid research. To this end, we focus here on different biological applications of clickable lipids, mainly to follow metabolic conversions, their visualization by confocal or superresolution microscopy or the identification of their protein interaction partners. Finally, we describe recent approaches employing organelle-targeted and clickable lipid probes to accurately follow intracellular sphingolipid transport with organellar precision. [ABSTRACT FROM AUTHOR]

UV-crosslinking of protein and RNA in direct contacts has been widely used to study protein-RNA complexes while our understanding of the photo-crosslinking mechanisms remains poor. This knowledge gap is due to the challenge of precisely mapping the crosslink sites in protein and RNA simultaneously in their native sequence and structural contexts. Here we systematically analyze protein-RNA interactions and photo-crosslinking by bridging crosslinked nucleotides and amino acids mapped using different assays with protein-RNA complex structures. We developed a computational method PxR3D-map which reliably predicts crosslink sites using structural information characterizing protein-RNA interaction interfaces. Analysis of the informative features revealed that photo-crosslinking is facilitated by base stacking with not only aromatic residues, but also dipeptide bonds that involve glycine, and distinct mechanisms are utilized by different RNA-binding domains. Our work suggests protein-RNA photo-crosslinking is highly selective in the cellular environment, which can guide data interpretation and further technology development for UV-crosslinking-based assays. Feng et al. developed a computational method PxR3D-map to jointly analyze crosslinked nucleotides and amino acids in protein-RNA complexes, which revealed key structural features underlying photocrosslinking of protein and RNA in cells. [ABSTRACT FROM AUTHOR]

Additive manufacturing capable of controlling and dynamically modulating structures down to the nanoscopic scale remains challenging. By marrying additive manufacturing with self-assembly, we develop a UV (ultra-violet)-assisted direct ink write approach for on-the-fly modulation of structural color by programming the assembly kinetics through photo-cross-linking. We design a photo-cross-linkable bottlebrush block copolymer solution as a printing ink that exhibits vibrant structural color (i.e., photonic properties) due to the nanoscopic lamellar structures formed post extrusion. By dynamically modulating UV-light irradiance during printing, we can program the color of the printed material to access a broad spectrum of visible light with a single ink while also creating color gradients not previously possible. We unveil the mechanism of this approach using a combination of coarse-grained simulations, rheological measurements, and structural characterizations. Central to the assembly mechanism is the matching of the cross-linking timescale with the assembly timescale, which leads to kinetic trapping of the assembly process that evolves structural color from blue to red driven by solvent evaporation. This strategy of integrating cross-linking chemistry and out-of-equilibrium processing opens an avenue for spatiotemporal control of self-assembled nanostructures during additive manufacturing. [ABSTRACT FROM AUTHOR]

This study focuses on developing surface coatings with excellent antifouling properties, crucial for applications in the medical, biological, and technical fields, for materials and devices in direct contact with living tissues and bodily fluids such as blood. This approach combines thermoresponsive poly(2‐alkyl‐2‐oxazoline)s, known for their inherent protein‐repellent characteristics, with established antifouling motifs based on betaines. The polymer framework is constructed from various monomer types, including a novel benzophenone‐modified 2‐oxazoline for photocrosslinking and an azide‐functionalized 2‐oxazoline, allowing subsequent modification with alkyne‐substituted antifouling motifs through copper(I)‐catalyzed azide‐alkyne cycloaddition. From these polymers surface‐attached networks are created on benzophenone‐modified gold substrates via photocrosslinking, resulting in hydrogel coatings with several micrometers thickness when swollen with aqueous media. Given that poly(2‐alkyl‐2‐oxazoline)s can exhibit a lower critical solution temperature in water, their temperature‐dependent solubility is compared to the swelling behavior of the surface‐attached hydrogels upon thermal stimulation. The antifouling performance of these hydrogel coatings in contact with human blood plasma is further evaluated by surface plasmon resonance and optical waveguide spectroscopy. All surfaces demonstrate extremely low retention of blood plasma components, even with undiluted plasma. Notably, hydrogel layers with sulfobetaine moieties allow efficient penetration by plasma components, which can then be easily removed by rinsing with buffer. [ABSTRACT FROM AUTHOR]

Oncolytic Newcastle disease virus is a new type of cancer immunotherapy drug. This paper proposes a scheme for delivering oncolytic viruses using hydrogel microneedles. Gelatin methacryloyl (GelMA) was synthesized by chemical grafting, and GelMA microneedles encapsulating oncolytic Newcastle disease virus (NDV) were prepared by micro-molding and photocrosslinking. The release and expression of NDV were tested by immunofluorescence and hemagglutination experiments. The experiments proved that GelMA was successfully synthesized and had hydrogel characteristics. NDV was evenly dispersed in the allantoic fluid without agglomeration, showing a characteristic virus morphology. NDV particle size was 257.4 ± 1.4 nm, zeta potential was −13.8 ± 0.5 mV, virus titer TCID50 was 107.5/mL, and PFU was 2 × 107/mL, which had a selective killing effect on human liver cancer cells in a dose and time-dependent manner. The NDV@GelMA microneedles were arranged in an orderly cone array, with uniform height and complete needle shape. The distribution of virus-like particles was observed on the surface. GelMA microneedles could successfully penetrate 5% agarose gel and nude mouse skin. Optimal preparation conditions were freeze-drying. We successfully prepared GelMA hydrogel microneedles containing NDV, which could effectively encapsulate NDV but did not detect the release of NDV. [ABSTRACT FROM AUTHOR]