Dual role of proliferating cell nuclear antigen monoubiquitination in facilitating Fanconi anemia-mediated interstrand crosslink repair.

The Fanconi anemia (FA) repair pathway governs repair of highly genotoxic DNA interstrand crosslinks (ICLs) and relies on translesion synthesis (TLS). TLS is facilitated by REV1 or site-specific monoubiquitination of proliferating cell nuclear antigen (PCNA) (PCNA-Ub) at lysine 164 (K164). A PcnaK164R/K164R but not Rev1-/- mutation renders mammals hypersensitive to ICLs. Besides the FA pathway, alternative pathways have been associated with ICL repair (1, 2), though the decision making between those remains elusive. To study the dependence and relevance of PCNA-Ub in FA repair, we intercrossed PcnaK164R/+; Fancg-/+ mice. A combined mutation (PcnaK164R/K164R; Fancg-/- ) was found embryonically lethal. RNA-seq of primary double-mutant (DM) mouse embryonic fibroblasts (MEFs) revealed elevated levels of replication stress-induced checkpoints. To exclude stress-induced confounders, we utilized a Trp53 knock-down to obtain a model to study ICL repair in depth. Regarding ICL-induced cell toxicity, cell cycle arrest, and replication fork progression, single-mutant and DM MEFs were found equally sensitive, establishing PCNA-Ub to be critical for FA-ICL repair. Immunoprecipitation and spectrometry-based analysis revealed an unknown role of PCNA-Ub in excluding mismatch recognition complex MSH2/MSH6 from being recruited to ICLs. In conclusion, our results uncovered a dual function of PCNA-Ub in ICL repair, i.e. exclude MSH2/MSH6 recruitment to channel the ICL toward canonical FA repair, in addition to its established role in coordinating TLS opposite the unhooked ICL.

Reprocessable Polymer Networks Containing Sulfur-Based, Percolated Dynamic Covalent Cross-Links and Percolated or Non-Percolated, Static Cross-Links.

One method to improve the properties of covalent adaptable networks (CANs) is to reinforce them with a fraction of permanent cross-links without sacrificing their (re)processability. Here, a simple method to synthesize poly(n-hexyl methacrylate) (PHMA) and poly(n-lauryl methacrylate) (PLMA) networks containing static dialkyl disulfide cross-links (utilizing bis(2-methacryloyl)oxyethyl disulfide, or DSDMA, as a permanent cross-linker) and dynamic dialkylamino sulfur-sulfur cross-links (utilizing BiTEMPS methacrylate as a dissociative dynamic covalent cross-linker) is presented. The robustness and (re)processability of the CANs are demonstrated, including the full recovery of cross-link density after recycling. The authors also investigate the effect of static cross-link content on the stress relaxation responses of the CANs with and without percolated, static cross-links. As PHMA and PLMA have very different activation energies of their respective cooperative segmental mobilities, it is shown that the dissociative CANs without percolated, static cross-links have activation energies of stress relaxation that are dominated by the dissociation of BiTEMPS methacrylate cross-links rather than by the cooperative relaxations of backbone segments, i.e., the alpha relaxation. In CANs with percolated, static cross-links, the segmental relaxation of side chains, i.e., the beta relaxation, is critical in allowing for large-scale stress relaxation and governs their activation energies of stress relaxation.

Storage Life of Particle-Filled Polymer Composites Considering Aging Effects.

This study investigates the storage life of particle-filled polymer composites (PFPCs) under the influence of aging effects. High-temperature accelerated aging tests were conducted at 60 °C, 70 °C, and 80 °C for various days to analyze the impact of aging time and temperature on the mechanical behavior of the materials. A predictive model for crosslink density was established using the Arrhenius equation, and the relationship between crosslink density and relaxation modulus was determined based on polymer physics theory. On this basis, a viscoelastic constitutive model that incorporates aging effects was developed. Structural analyses of a PFPC column with a length of 2.3 m and outer diameter of 1.8 m were performed using the UMAT subroutine in ABAQUS. Subsequently, a safety margin assessment method based on dewetting strain was employed to predict the storage life of the PFPC column. The results indicate that the aging viscoelastic constitutive model effectively characterizes the hardening effects caused by aging in the composites during storage. The storage life for the PFPC column considering aging effects decreases from 22 years to 19 years compared to models that ignore such effects. This approach provides a reference for estimating the storage life of PFPC columns considering aging effects.

Suppressed Defects by Functional Thermally Cross-Linked Fullerene for High-Efficiency Tin-Lead Perovskite Solar Cells.

Mixed tin-lead (Sn-Pb) perovskites have attracted the attention of the community due to their narrow bandgap, ideal for photovoltaic applications, especially tandem solar cells. However, the oxidation and rapid crystallization of Sn2+ and the interfacial traps hinder their development. Here, cross-linkable [6,6]-phenyl-C61-butyric styryl dendron ester (C-PCBSD) is introduced during the quenching step of perovskite thin film processing to suppress the generation of surface defects at the electron transport layer interface and improve the bulk crystallinity. The C-PCBSD has strong coordination ability with Sn2+ and Pb2+ perovskite precursors, which retards the crystallization process, suppresses the oxidation of Sn2+, and improves the perovskite bulk and surface crystallinity, yielding films with reduced nonradiative recombination and enhanced interface charge extraction. Besides, the C-PCBSD network deposited on the perovskite surface displays superior hydrophobicity and oxygen resistance. Consequently, the devices with C-PCBSD obtain PCEs of up to 23.4% and retained 97% of initial efficiency after 2000 h of storage in a N2 atmosphere.

Photocrosslinked carboxymethylcellulose-based hydrogels: Synthesis, characterization for curcumin delivery and wound healing.

Skin could protect our body and regenerate itself to against dysfunctional and disfiguring scars when faced with external injury. As wound dressings, hydrogels are biocompatible, hydrophilic and have a 3D structure similar to the extracellular matrix (ECM). In particular, hydrogels with drug-releasing capabilities are in acute wound healing. In this paper, photocrosslinked hydrogels served as wound dressing based on sodium carboxymethylcellulose (CMC) were prepared to promote wound healing. Photocrosslinked hydrogels were prepared by grafting lysine and allyl glycidyl ether (AGE) onto CMC and encapsulating curcumin (Cur). The synthesized hydrogels had the unique 3D porous structure with a swelling ratio up to 1300 % in aqueous solution. The drug release ratios of the hydrogels were 20.8 % in acid environment, and 14.4 % in alkaline environment. Notably, the hydrogels showed good biocompatibility and antibacterial properties and also exhibited the ability to accelerate the process of skin wound healing while prevent inflammation and scar formation when applied to a mouse skin wound model. As a result, the prepared hydrogels Gel-CLA@Cur showed great potential in wound healing.

A Cellulose-Based Dual-Crosslinked Framework with Sensitive Shape and Color Changes in Acid/Alkaline Vapors.

Cellulose detectors, as green sensors, are some of the defensive mechanisms of plants which combat environmental stresses. However, extracted cellulose struggles to fulfil these functionalities due to its rigid physical/chemical properties. In this study, a novel cellulose dual-crosslinked framework (CDCF) is proposed. This comprises a denser temporary physical crosslinking bond (hydrogen bonding) and a looser covalent crosslinking bond (N,N-methylenebisacrylamide), which create deformable spaces between the two crosslinking sites. Abundant pH-sensitive carboxyl groups and ultralight, highly porous structures make CDCF response very sensitive in acid/alkaline vapor environments. Hence, a significant shrinkage of CDCF was observed following exposure to vapors. Moreover, a curcumin-incorporated CDCF exhibited dual shape and color changes when exposed to acid/alkaline vapors, demonstrating great potential for the multi-detection of acid/alkaline vapors.

Mechanical Properties of Alkasite Material with Different Curing Modes and Simulated Aging Conditions.

This study aimed to evaluate the micro-mechanical and macro-mechanical properties of self-cured and light-cured alkasite and to investigate how accelerated degradation in acidic, alkaline, and ethanol solutions affects the macro-mechanical properties of self-cured and light-cured alkasite. The specimens of the alkasite material (Cention Forte, Ivoclar Vivadent) were prepared according to the following three curing modes: (1) light-cured immediately, (2) light-cured after a 5-min delay, and (3) self-cured. Microhardness was tested before and after immersion in absolute ethanol to indirectly determine crosslink density, while flexural strength and flexural modulus were measured using a three-point bending test after accelerated aging in the following solutions: (1) lactic acid solution (pH = 4.0), (2) NaOH solution (pH = 13.0), (3) phosphate-buffered saline solution (pH = 7.4), and (4) 75% ethanol solution. The data were statistically analyzed using a two-way ANOVA and Tukey post hoc test. The results showed that the microhardness, flexural strength, and flexural modulus were significantly lower in self-cured specimens compared to light-cured specimens. A 5-min delay between the extrusion of the material from the capsule and light curing had no significant effect on any of the measured properties. A significant effect of the accelerated aging solutions on macro-mechanical properties was observed, with ethanol and alkaline solutions having a particularly detrimental effect. In conclusion, light curing was preferable to self-curing, as it resulted in significantly better micro- and macro-mechanical properties, while a 5-min delay between mixing the capsule and light curing had no negative effects.

Water Transport-Induced Liquid-Liquid Phase Separation Facilitates Gelation for Controllable and Facile Fabrication of Physically Crosslinked Microgels.

Physically crosslinked microgels (PCMs) offer a biocompatible platform for various biomedical applications. However, current PCM fabrication methods suffer from their complexity and poor controllability, due to their reliance on altering physical conditions to initiate gelation and their dependence on specific materials. To address this issue, a novel PCM fabrication method is devised, which employs water transport-induced liquid-liquid phase separation (LLPS) to trigger the intermolecular interaction-supported sol-gel transition within aqueous emulsion droplets. This method enables the controllable and facile generation of PCMs through a single emulsification step, allowing for the facile production of PCMs with various materials and sizes, as well as controllable structures and mechanical properties. Moreover, this PCM fabrication method holds great promise for diverse biomedical applications. The interior of the PCM not only supports the encapsulation and proliferation of bacteria but also facilitates the encapsulation of eukaryotic cells after transforming the system into an all-aqueous emulsion. Furthermore, through appropriate surface functionalization, the PCMs effectively activate T cells in vitro upon coculturing. This work represents an advancement in PCM fabrication and offers new insights and perspectives for microgel engineering.

A dynamically cross-linked catechol-grafted chitosan/gelatin hydrogel dressing synergised with photothermal therapy and baicalin reduces wound infection and accelerates wound healing.

Superior multifunctional hydrogel dressings are of considerable interest in wound healing. In clinical practice, it is useful to investigate hydrogel dressings that offer multifunctional benefits to expedite the process of wound healing. In this study, Catechol-grafted Chitosan, Gelatin, and Fe3+ as substrates to construct a hydrogel network. The network was dynamically cross-linked to form Ccg@Fe hydrogel substrate. Fe3O4 nanoparticles and baicalin, which possess antimicrobial and anti-inflammatory properties, were loaded onto the substrate to form a photothermal antibacterial composite hydrogel dressing (Ccg@Fe/Bai@Fe3O4 NPs). The Ccg@Fe hydrogel was characterised using Fourier transform infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometry (UV-Vis). The morphological, mechanical, and adhesion properties of the hydrogel were determined using scanning electron microscopy (SEM) and a universal testing machine. The hydrogel's swelling, hemostasis, and self-healing properties were also evaluated. Additionally, the study determined the release rate of hydrogel-loaded antimicrobial and anti-inflammatory Baicalin (Ccg@Fe/Bai) and evaluated the photothermal antimicrobial properties of hydrogel-loaded Fe3O4 nanoparticles (Ccg@Fe/Bai@Fe3O4 NPs) through synergistic photothermal therapy (PTT). Histological staining of mice skin wound tissues using Masson and H&E revealed that the Ccg@Fe/Bai@Fe3O4 NPs hydrogel dressing demonstrated potential healing ability with the aid of PTT. The study suggests that this multifunctional hydrogel dressing has great potential for wound healing.

Streamlined Full-Length Total RNA Sequencing of Paraformaldehyde-Fixed Brain Tissues.

Paraformaldehyde (PFA) fixation is the preferred method for preserving tissue architecture for anatomical and pathological observations. Meanwhile, PFA reacts with the amine groups of biomolecules to form chemical cross-linking, which preserves RNA within the tissue. This has great prospects for RNA sequencing to characterize the molecular underpinnings after anatomical and pathological observations. However, RNA is inaccessible due to cross-linked adducts forming between RNA and other biomolecules in prolonged PFA-fixed tissue. It is also difficult to perform reverse transcription and PCR, resulting in low sequencing sensitivity and reduced reproducibility. Here, we developed a method to perform RNA sequencing in PFA-fixed tissue, which is easy to use, cost-effective, and allows efficient sample multiplexing. We employ cross-link reversal to recover RNA and library construction using random primers without artificial fragmentation. The yield and quality of recovered RNA significantly increased through our method, and sequencing quality metrics and detected genes did not show any major differences compared with matched fresh samples. Moreover, we applied our method for gene expression analysis in different regions of the mouse brain and identified unique gene expression profiles with varied functional implications. We also find significant dysregulation of genes involved in Alzheimer's disease (AD) pathogenesis within the medial septum (MS)/vertical diagonal band of Broca (VDB) of the 5×FAD mouse brain. Our method can thus increase the performance of high-throughput RNA sequencing with PFA-fixed samples and allows longitudinal studies of small tissue regions isolated by their in situ context.

Recurrent Duplication and Diversification of a Vital DNA Repair Gene Family Across Drosophila.

Maintaining genome integrity is vital for organismal survival and reproduction. Essential, broadly conserved DNA repair pathways actively preserve genome integrity. However, many DNA repair proteins evolve adaptively. Ecological forces like UV exposure are classically cited drivers of DNA repair evolution. Intrinsic forces like repetitive DNA, which also imperil genome integrity, have received less attention. We recently reported that a Drosophila melanogaster-specific DNA satellite array triggered species-specific, adaptive evolution of a DNA repair protein called Spartan/MH. The Spartan family of proteases cleave hazardous, covalent crosslinks that form between DNA and proteins ("DNA-protein crosslink repair"). Appreciating that DNA satellites are both ubiquitous and universally fast-evolving, we hypothesized that satellite DNA turnover spurs adaptive evolution of DNA-protein crosslink repair beyond a single gene and beyond the D. melanogaster lineage. This hypothesis predicts pervasive Spartan gene family diversification across Drosophila species. To study the evolutionary history of the Drosophila Spartan gene family, we conducted population genetic, molecular evolution, phylogenomic, and tissue-specific expression analyses. We uncovered widespread signals of positive selection across multiple Spartan family genes and across multiple evolutionary timescales. We also detected recurrent Spartan family gene duplication, divergence, and gene loss. Finally, we found that ovary-enriched parent genes consistently birthed functionally diverged, testis-enriched daughter genes. To account for Spartan family diversification, we introduce a novel mechanistic model of antagonistic coevolution that links DNA satellite evolution and adaptive regulation of Spartan protease activity. This framework promises to accelerate our understanding of how DNA repeats drive recurrent evolutionary innovation to preserve genome integrity.

Tailoring Mechanical Properties of a Ceramic Nanowire Aerogel with Pyrolytic Carbon for In Situ Resilience at 1400 °C.

Resilient ceramic aerogels with a unique combination of lightweight, good high-temperature stability, high specific area, and thermal insulation properties are known for their promising applications in various fields. However, the mechanical properties of traditional ceramic aerogels are often constrained by insufficient interlocking of the building blocks. Here, we report a strategy to largely increase the interlocking degree of the building blocks by depositing a pyrolytic carbon (PyC) coating onto Si3N4 nanowires. The results show that the mechanical performances of the Si3N4 nanowire aerogels are intricately linked to the microstructure of the PyC nodes. The compression resilience of the Si3N4@PyC nanowire aerogels increases with an increase of the interlayer cross-linking in PyC. Additionally, benefiting from the excellent high-temperature stability of PyC, the Si3N4@PyC nanowire aerogels demonstrate significantly superior in situ resilience up to 1400 °C. The integrated mechanical and high-temperature properties of the Si3N4@PyC nanowire aerogels make them highly appealing for applications in harsh conditions. The facile method of manipulating the microstructure of the nodes may offer a perspective for tailoring the mechanical properties of ceramic aerogels.

Glutathione-responsive CD-MOFs co-loading honokiol and indocyanine green biomimetic active targeting to enhance photochemotherapy for breast cancer.

Breast cancer has now replaced lung cancer as the most prevalent malignant tumor worldwide, posing a serious health risk to women. We have recently designed a promising option strategy for the treatment of breast cancer. In this work, cyclodextrin metal-organic frameworks with high drug-carrying properties were endo-crosslinked by 3,3'dithiodipropionyl chloride to form cubic phase gel nanoparticles, which were drug-loaded and then coated by MCF-7 cell membranes. After intravenous injection, this multifunctional nanomedicine achieved dramatically homologous targeting co-delivery of honokiol and indocyanine green to the breast tumor. Further, the disulfide bonds in the nanostructures achieved glutathione-responsive drug release, induced tumor cells to produce reactive oxygen species and promoted apoptosis, resulting in tumor necrosis, and at the same time, inhibited Ki67 protein expression, which enhanced photochemotherapy, and resulted in a 94.08 % in vivo tumor suppression rate in transplanted tumor-bearing mice. Thereby, this nanomimetic co-delivery system may have a place in breast cancer therapy due to its simple fabrication process, excellent biocompatibility, efficient targeted delivery of insoluble drugs, and enhanced photochemotherapy.

The interplay of homology-directed repair pathways in the repair of zebularine-induced DNA-protein crosslinks in Arabidopsis.

DNA-protein crosslinks (DPCs) are highly toxic DNA lesions represented by proteins covalently bound to the DNA. Persisting DPCs interfere with fundamental genetic processes such as DNA replication and transcription. Cytidine analog zebularine (ZEB) has been shown to crosslink DNA METHYLTRANSFERASE1 (MET1). Recently, we uncovered a critical role of the SMC5/6-mediated SUMOylation in the repair of DPCs. In an ongoing genetic screen, we identified two additional candidates, HYPERSENSITIVE TO ZEBULARINE 2 and 3, that were mapped to REGULATOR OF TELOMERE ELONGATION 1 (RTEL1) and polymerase TEBICHI (TEB), respectively. By monitoring the growth of hze2 and hze3 plants in response to zebularine, we show the importance of homologous recombination (HR) factor RTEL1 and microhomology-mediated end-joining (MMEJ) polymerase TEB in the repair of MET1-DPCs. Moreover, genetic interaction and sensitivity assays showed the interdependency of SMC5/6 complex, HR, and MMEJ in the homology-directed repair of MET1-DPCs in Arabidopsis. Altogether, we provide evidence that MET1-DPC repair in plants is more complex than originally expected.

Metal-ligand cross-link strategy engineered iron-doped dopamine-based superstructure as peroxidase-like nanozymes for detection of glucose.

Nanozymes are nanomaterials with mimetic enzyme properties and the related research has attracted much attention. It is of great value to develop methods to construct nanozymes and to study their application in bioanalysis. Herein, the metal-ligand cross-linking strategy was developed to fabricate superstructure nanozymes. This strategy takes advantage of being easy to operate, adjustable, cheap, and universal. The fabricated superstructure nanozymes possess efficient peroxidase-like catalytic activity. The enzyme reaction kinetic tests demonstrated that for TMB and H2O2, the Km is 0.229 and 1.308 mM, respectively. Furthermore, these superstructure nanozymes are applied to highly efficient and sensitive detection of glucose. The linear range for detecting glucose is 20-2000 µM, and the limit of detection is 17.5 µM. Furthermore, mechanistic research illustrated that this integrated system oxidizes glucose to produce hydrogen peroxide and further catalyzes the production of ·OH and O2·-, which results in a chromogenic reaction of oxidized TMB for the detection of glucose. This work could not only contribute to the development of efficient nanozymes but also inspire research in the highly sensitive detection of other biomarkers.

Replication-Independent ICL Repair: From Chemotherapy to Cell Homeostasis.

Interstrand crosslinks (ICLs) are a type of covalent lesion that can prevent transcription and replication by inhibiting DNA strand separation and instead trigger cell death. ICL inducing compounds are commonly used as chemotherapies due to their effectiveness in inhibiting cell proliferation. Naturally occurring crosslinking agents formed from metabolic processes can also pose a challenge to genome stability especially in slowly or non-dividing cells. Cells maintain a variety of ICL repair mechanisms to cope with this stressor within and outside the S phase of the cell cycle. Here, we discuss the mechanisms of various replication-independent ICL repair pathways and how crosslink repair efficiency is tied to aging and disease.

Research progress of photo-crosslink hydrogels in ophthalmology: A comprehensive review focus on the applications.

Hydrogel presents a three-dimensional polymer network with high water content. Over the past decade, hydrogel has developed from static material to intelligent material with controllable response. Various stimuli are involved in the formation of hydrogel network, among which photo-stimulation has attracted wide attention due to the advantages of controllable conditions, which has a good application prospect in the treatment of ophthalmic diseases. This paper reviews the application of photo-crosslink hydrogels in ophthalmology, focusing on the types of photo-crosslink hydrogels and their applications in ophthalmology, including drug delivery, tissue engineering and 3D printing. In addition, the limitations and future prospects of photo-crosslink hydrogels are also provided.

Cdc48/p97 segregase: Spotlight on DNA-protein crosslinks.

The ATP-dependent molecular chaperone Cdc48 (in yeast) and its human counterpart p97 (also known as VCP), are essential for a variety of cellular processes, including the removal of DNA-protein crosslinks (DPCs) from the DNA. Growing evidence demonstrates in the last years that Cdc48/p97 is pivotal in targeting ubiquitinated and SUMOylated substrates on chromatin, thereby supporting the DNA damage response. Along with its cofactors, notably Ufd1-Npl4, Cdc48/p97 has emerged as a central player in the unfolding and processing of DPCs. This review introduces the detailed structure, mechanism and cellular functions of Cdc48/p97 with an emphasis on the current knowledge of DNA-protein crosslink repair pathways across several organisms. The review concludes by discussing the potential therapeutic relevance of targeting p97 in DPC repair.

Constructing gellan gum/konjac glucomannan/wheat fiber composite hydrogel to simulate edible cartilage by ionic cross-link and moisture regulation.

The utilization of non-animal-derived materials to imitate cartilage is critical for the advancement of plant-based simulated meat. In this study, gellan gum (GG), konjac glucomannan (KGM), and wheat fiber (WF) were used to construct hydrogel, and the mechanical strength, water properties, and microstructure were regulated by constructing Ca2+ cross-links and moisture control. The hardness, chewiness, resilience, shear force, and shear energy of the Ca2+ cross-linked samples were significantly improved. Extrusion dehydration further changes the related mechanical properties of the hydrogel and results in a tighter microstructure. The findings suggest that the establishment of Ca2+ cross-links and water regulation are efficacious techniques for modifying the texture of the GG/KGM/WF composite hydrogel. Correlation analysis and sensory evaluation showed that the test indexes and sensory scores of the samples with Ca2+ crosslinking and 80 % moisture content were similar to chicken breast cartilage, and the samples with Ca2+ crosslinking and 70 % moisture content were similar to pig crescent bone. This study presents a framework for designing edible cartilage simulators using polysaccharide hydrogels, with implications for enhancing the resemblance of plant-based meat products to real meat and expanding the range of vegetarian offerings available.

NEIL3: A unique DNA glycosylase involved in interstrand DNA crosslink repair.

Endonuclease VIII-like 3 (NEIL3) is a versatile DNA glycosylase that repairs a diverse array of chemical modifications to DNA. Unlike other glycosylases, NEIL3 has a preference for lesions within single-strand DNA and at single/double-strand DNA junctions. Beyond its canonical role in base excision repair of oxidized DNA, NEIL3 initiates replication-dependent interstrand DNA crosslink repair as an alternative to the Fanconi Anemia pathway. This review outlines our current understanding of NEIL3's biological functions, role in disease, and three-dimensional structure as it pertains to substrate specificity and catalytic mechanism.