Historical climate change and vicariance events contributed to the intercontinental disjunct distribution pattern of ash species (Fraxinus, Oleaceae).

The Northern Hemisphere temperate forests exhibit a disjunct distributional pattern in Europe, North America, and East Asia. Here, to reveal the promoter of intercontinental disjunct distribution, Fraxinus was used as a model organism to integrate abundant fossil evidence with high-resolution phylogenies in a phytogeographic analysis. We constructed a robust phylogenetic tree using genomic data, reconstructed the geographic ancestral areas, and evaluated the effect of incorporating fossil information on the reconstructed biogeographic history. The phylogenetic relationships of Fraxinus were highly resolved and divided into seven clades. Fraxinus originated in western North America during Eocene, and six intercontinental dispersal events and five intercontinental vicariance events were occured. Results suggest that climate change and vicariance contributed to the intercontinental disjunct distribution pattern of Fraxinus. Moreover, results highlight the necessity of integrating phylogenetic relationship and fossil to improve the reliability of inferred biogeographic events and our understanding of the processes underlying disjunct distributions.

Tryptophan catabolism via the kynurenine pathway regulates infection and inflammation: from mechanisms to biomarkers and therapies.

BACKGROUND: L-Tryptophan (L-Trp), an essential amino acid, is the only amino acid whose level is regulated specifically by immune signals. Most proportions of Trp are catabolized via the kynurenine (Kyn) pathway (KP) which has evolved to align the food availability and environmental stimulation with the host pathophysiology and behavior. Especially, the KP plays an indispensable role in balancing the immune activation and tolerance in response to pathogens. SCOPE OF REVIEW: In this review, we elucidate the underlying immunological regulatory network of Trp and its KP-dependent catabolites in the pathophysiological conditions by participating in multiple signaling pathways. Furthermore, the KP-based regulatory roles, biomarkers, and therapeutic strategies in pathologically immune disorders are summarized covering from acute to chronic infection and inflammation. MAJOR CONCLUSIONS: The immunosuppressive effects dominate the functions of KP induced-Trp depletion and KP-produced metabolites during infection and inflammation. However, the extending minor branches from the KP are not confined to the immune tolerance, instead they go forward to various functions according to the specific condition. Nevertheless, persistent efforts should be made before the clinical use of KP-based strategies to monitor and cure infectious and inflammatory diseases.

Time and Space Dual-Blockade Strategy for Highly Invasive Nature of Triple-Negative Breast Cancer in Enhanced Sonodynamic Therapy Based on Fe-MOF Nanoplatforms.

Triple-negative breast cancer (TNBC), due to its high malignant degree and strong invasion ability, leads to poor prognosis and easy recurrence, so effectively curbing the invasion of TNBC is the key to obtaining the ideal therapeutic effect. Herein, a therapeutic strategy is developed that curbs high invasions of TNBC by inhibiting cell physiological activity and disrupting tumor cell structural function to achieve the time and space dual-blockade. The time blockade is caused by the breakthrough of the tumor-reducing blockade based on the ferroptosis process and the oxidation-toxic free radicals generated by enhanced sonodynamic therapy (SDT). Meanwhile, alkyl radicals from 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) and 1 O2 attacked the organelles of tumor cells under ultrasound (US), reducing the physiological activity of the cells. The attack of free radicals on the cytoskeleton, especially on the proteins of F-actin and its assembly pathway, achieves precise space blockade of TNBC. The damage to the cytoskeleton and the suppression of the repair process leads to a significant decline in the ability of tumor cells to metastasize and invade other organs. In summary, the FTM@AM nanoplatforms have a highly effective killing and invasion inhibition effect on invasive TNBC mediated by ultrasound, showcasing promising clinical transformation potential.

ZFP541 and KCTD19 regulate chromatin organization and transcription programs for male meiotic progression.

The successful progression of meiosis prophase I requires integrating information from the structural and molecular levels. In this study, we show that ZFP541 and KCTD19 work in the same genetic pathway to regulate the progression of male meiosis and thus fertility. The Zfp541 and/or Kctd19 knockout male mice show various structural and recombination defects including detached chromosome ends, aberrant localization of chromosome axis components and recombination proteins, and globally altered histone modifications. Further analyses on RNA-seq, ChIP-seq, and ATAC-seq data provide molecular evidence for the above defects and reveal that ZFP541/KCTD19 activates the expression of many genes by repressing several major transcription repressors. More importantly, we reveal an unexpected role of ZFP541/KCTD19 in directly modulating chromatin organization. These results suggest that ZFP541/KCTD19 simultaneously regulates the transcription cascade and chromatin organization to ensure the coordinated progression of multiple events at chromosome structural and biochemical levels during meiosis prophase I.

A Fully Elastic Wearable Electrochemical Sweat Detection System of Tree-Bionic Microfluidic Structure for Real-Time Monitoring.

Fresh sweat contains a diverse range of physiological indicators that can effectively reflect changes in the body. However, existing wearable sweat detection systems face challenges in efficiently collecting and detecting fresh sweat in real-time. Additionally, they often lack the necessary deformation capabilities, resulting in discomfort for the wearer. Here, a fully elastic wearable electrochemical sweat detection system is developed that integrates a sweat-collecting microfluidic chip, a multi-parameter electrochemical sensor, a micro-heater, and a sweat detection elastic circuit board system. The unique tree-bionic structure of the microfluidic chip significantly enhances the efficiency of fresh sweat collection and discharge, enabling real-time detection by the electrochemical sensors. The sweat multi-parameter electrochemical sensor offers high-precision and high-sensitivity measurements of sodium ions, potassium ions, lactate, and glucose. The electronic system is built on an elastic circuit board that matches perfectly to wrinkled skin, ensuring improved wearing comfort and enabling multi-channel data sampling, processing, and wireless transmission. This state-of-the-art system represents a significant advancement in the field of elastic wearable sweat detection and holds promising potential for extending its capabilities to the detection of other sweat markers or various wearable applications.

Gold Nanocage-Based Multifunctional Nanosensitizers for Programmed Photothermal /Radiation/Chemical Coordinated Therapy Guided by FL/MR/PA Multimodal Imaging.

Background: Radiotherapy is one of the main clinical methods for the treatment of malignant tumors at present. However, its application is limited by the radiation resistance of some tumor cells and the irradiation damage to the surrounding normal tissues, and the limitation of radiotherapy dose also affects the therapeutic effect. Therefore, developing diagnostic and therapeutic agents with imaging and radiosensitizing functions is urgently needed to improve the accuracy and efficacy of radiotherapy. Materials and Strategy: Herein, we synthesized multifunctional nanotheranostic FRNPs nanoparticles based on gold nanocages (GNCs) and MnO2 for magnetic resonance (MR)/photoacoustic (PA) imaging and combined photothermal, radiosensitive and chemical therapy. A programmed therapy strategy based on FRNPs is proposed. First, photothermal therapy is applied to ablate large tumors and increase the sensitivity of the tumor tissue to radiotherapy, then X-ray radiation is performed to further reduce the tumor size, and finally chemotherapeutic agents are used to eliminate smaller residual tumors and distant metastases. Results: As revealed by fluorescence, MR and PA imaging, FRNPs achieved efficient aggregation and retention at tumor sites of mice after intravenous injection. In vivo studies have shown that the programmed treatment of FRNPs-injected nude mice which were exposed to X-ray after 808 laser irradiation achieved the greatest inhibition of tumor growth compared with other treatment groups. Moreover, no obvious systemic toxicity was observed in all groups of mice, indicating the good biocompatibility of FRNPs and the safety of the treatment scheme. Conclusion: To sum up, our work not only showed a new radiosensitizer, but also provided a promising theranostic strategy for cancer treatment.

Artificial intelligence in theranostics of gastric cancer, a review.

Gastric cancer (GC) is one of the commonest cancers with high morbidity and mortality in the world. How to realize precise diagnosis and therapy of GC owns great clinical requirement. In recent years, artificial intelligence (AI) has been actively explored to apply to early diagnosis and treatment and prognosis of gastric carcinoma. Herein, we review recent advance of AI in early screening, diagnosis, therapy and prognosis of stomach carcinoma. Especially AI combined with breath screening early GC system improved 97.4 % of early GC diagnosis ratio, AI model on stomach cancer diagnosis system of saliva biomarkers obtained an overall accuracy of 97.18 %, specificity of 97.44 %, and sensitivity of 96.88 %. We also discuss concept, issues, approaches and challenges of AI applied in stomach cancer. This review provides a comprehensive view and roadmap for readers working in this field, with the aim of pushing application of AI in theranostics of stomach cancer to increase the early discovery ratio and curative ratio of GC patients.

Orchestrated feedback regulation between melatonin and sex hormones involving GPER1-PKA-CREB signaling in the placenta.

Maintaining placental endocrine homeostasis is crucial for a successful pregnancy. Pre-eclampsia (PE), a gestational complication, is a leading cause of maternal and perinatal morbidity and mortality. Aberrant elevation of testosterone (T0 ) synthesis, reduced estradiol (E2 ), and melatonin productions have been identified in preeclamptic placentas. However, the precise contribution of disrupted homeostasis among these hormones to the occurrence of PE remains unknown. In this study, we established a strong correlation between suppressed melatonin production and decreased E2 as well as elevated T0 synthesis in PE placentas. Administration of the T0 analog testosterone propionate (TP; 2 mg/kg/day) to pregnant mice from E7.5 onwards resulted in PE-like symptoms, along with elevated T0 production and reduced E2 and melatonin production. Notably, supplementation with melatonin (10 mg/kg/day) in TP-treated mice had detrimental effects on fetal and placental development and compromised hormone synthesis. Importantly, E2 , but not T0 , actively enhanced melatonin synthetase AANAT expression and melatonin production in primary human trophoblast (PHT) cells through GPER1-PKA-CREB signaling pathway. On the other hand, melatonin suppressed the level of estrogen synthetase aromatase while promoting the expressions of androgen synthetic enzymes including 17ß-HSD3 and 3ß-HSD1 in PHT cells. These findings reveal an orchestrated feedback mechanism that maintains homeostasis of placental sex hormones and melatonin. It is implied that abnormal elevation of T0 synthesis likely serves as the primary cause of placental endocrine disturbances associated with PE. The suppression of melatonin may represent an adaptive strategy to correct the imbalance in sex hormone levels within preeclamptic placentas. The findings of this study offer novel evidence that identifies potential targets for the development of innovative therapeutic strategies for PE.

ATF7IP2, a meiosis-specific partner of SETDB1, is required for proper chromosome remodeling and crossover formation during spermatogenesis.

Meiotic crossovers are required for the faithful segregation of homologous chromosomes and to promote genetic diversity. However, it is unclear how crossover formation is regulated, especially on the XY chromosomes, which show a homolog only at the tiny pseudoautosomal region. Here, we show that ATF7IP2 is a meiosis-specific ortholog of ATF7IP and a partner of SETDB1. In the absence of ATF7IP2, autosomes show increased axis length and more crossovers; however, many XY chromosomes lose the obligatory crossover, although the overall XY axis length is also increased. Additionally, meiotic DNA double-strand break formation/repair may also be affected by altered histone modifications. Ultimately, spermatogenesis is blocked, and male mice are infertile. These findings suggest that ATF7IP2 constraints autosomal axis length and crossovers on autosomes; meanwhile, it also modulates XY chromosomes to establish meiotic sex chromosome inactivation for cell-cycle progression and to ensure XY crossover formation during spermatogenesis.

Potential of plant DNA information in determining the provenance and identify of unknown victims.

Determination of the personal identity of victims is particularly important for the settlement of criminal cases. Unfortunately, useful information for identification is not always available. We here propose that the particles (pollens) of some plants with specific geographical distributions extracted from human lung tissues contribute to further determining the provenance or long-term residence of unknown victims, thereby considerably narrowing the search scope of the victims. We collected lung tissues from 155 victims with diverse causes of death, extracted DNA from lung tissues, sequenced the DNA fragments of plants on the Illumina Hiseq platform, and barcoded the plant species using phylogenetic methods. Finally, 108 unique plant sequences were detected in 55 samples and identified to belong to 36 species in 32 genera of 29 families. These plants were predominantly insect-pollinated crops and ornamental plants. No significant difference was observed between male and female samples, between urban and rural samples, or among samples of different ages and different sample sizes. There were 16 samples with 21 wild plant species. The original sources of 15 samples were overlapped with the distribution regions of detected plants; 2 samples narrowed the original sources to 2 provinces, which were quite coincident with their source places; 1 sample had no overlapping with its victim source region. Although plant information was only found in one-third of the samples, we further demonstrated the great potential of plant eDNA in identifying the source of unnamed corpses in a real-world case. We used plant eDNA from lung tissues to explore the provenance of an unknown female corpse found in Beijing. The source place of this victim was narrowed to Guangdong and Guangxi provinces, and finally, we confirmed her true identity in the list of missing persons in Guangxi Province. In the presence of a well-covered local reference library, the plant species detected in the lungs can be accurately identified. In difficult criminal cases where physical evidence is relatively weak, plant DNA information may provide new clues. In conclusion, the plant particles trapped in the lungs are promising to help forensic experts narrow the search scope for the identity of unknown victims.

MnO2 Coated Mesoporous PdPt Nanoprobes for Scavenging Reactive Oxygen Species and Solving Acetaminophen-Induced Liver Injury.

As one of the most widely used drugs, acetaminophen, is the leading cause of acute liver injury. In addition, acetaminophen-induced liver injury (AILI) has a strong relationship with the overproduced reactive oxygen species, which can be effectively eliminated by nanozymes. To address these challenges, mesoporous PdPt@MnO2 nanoprobes (PPM NPs) mimicking peroxide, catalase, and superoxide dismutase-like properties are synthesized. They demonstrate nontoxicity, high colloidal stability, and exceptional reactive oxygen species (ROS)-scavenging ability. By scavenging excessive ROS, decreasing inflammatory cytokines, and inhibiting the recruitment and activation of monocyte/macrophage cells and neutrophils, the pathology mechanism of PPM NPs in AILI is confirmed. Moreover, PPM NPs' therapeutic effect and good biocompatibility may facilitate the clinical treatment of AILI.

Anticancer Activity of Bitter Melon-Derived Vesicles Extract against Breast Cancer.

Due to their low immunogenicity, high biocompatibility and ready availability in large quantities, plant-derived vesicles extracts have attracted considerable interest as a novel nanomaterial in tumor therapy. Bitter melon, a medicinal and edible plant, has been reported to exhibit excellent antitumor effects. It is well-documented that breast cancer gravely endangers women's health, and more effective therapeutic agents must be urgently explored. Therefore, we investigated whether bitter melon-derived vesicles extract (BMVE) has antitumor activity against breast cancer. Ultracentrifugation was used to isolate BMVE with a typical "cup-shaped" structure and an average size of approximately 147 nm from bitter melon juice. The experimental outcomes indicate that 4T1 breast cancer cells could efficiently internalize BMVE, which shows apparent anti-proliferative and migration-inhibiting effects. In addition, BMVE also possesses apoptosis-inducing effects on breast cancer cells, which were achieved by stimulating the production of reactive oxygen species (ROS) and disrupting mitochondrial function. Furthermore, BMVE could dramatically inhibit tumor growth in vivo with negligible adverse effects. In conclusion, BMVE exhibits a pronounced antitumor effect on 4T1 breast cancer cells, which has great potential for use in tumor therapy.

Discovery and Functional Analysis of Secondary Hair Follicle miRNAs during Annual Cashmere Growth.

Secondary hair follicles (SHFs) produce the thermoregulatory cashmere of goats. MicroRNAs (miRNAs) play indispensable roles in hair follicle formation and growth. However, most studies examining miRNAs related to cashmere have been performed on goat skin. It remains unclear which miRNAs are highly expressed in SHFs or how miRNAs affect cashmere growth. In the present study, we isolated the SHFs under a dissecting microscope and analyzed the miRNA signatures during annual cashmere growth. Small-RNA sequencing followed by genome-wide expression analysis revealed that early anagen is a crucial phase for miRNA regulation of the cashmere growth, as revealed by two predominant groups of miRNAs. Although they exhibited opposite expression patterns, both groups demonstrated sharp changes of expression when in transit from early anagen to mid-anagen. In addition, we identified 96 miRNA signatures that were differentially expressed between different phases among 376 miRNAs. Functional analysis of the predicted target genes of highly expressed or differentially expressed miRNAs indicated that these miRNAs were involved in signal pathways associated with SHF development, regeneration, and regression. Furthermore, miR-143-3p was preferentially expressed in SHFs and Itga6 was identified as one of targets. The dual-luciferase and in situ hybridization assay demonstrated that miR-143-3p directly repressed the expression of Itga6, suggesting a possible novel role for miR-143-3p in cashmere growth.

Structure design mechanisms and inflammatory disease applications of nanozymes.

Nanozymes are artificial enzymes with high catalytic activity, low cost, and good biocompatibility, and have received ever-increasing attention in recent years. Various inorganic and organic nanoparticles have been found to exhibit enzyme-like activities and are used as nanozymes for diverse biomedical applications ranging from tumor imaging and therapeutics to detection. However, their further clinical applications are hindered by the potential toxicity and long-term retention of nanomaterials in vivo. Clarifying the catalytic mechanism of nanozymes and identifying the key factors responsible for their behavior can guide the design of nanozyme structure, enlighten the ways to improve their enzyme-like activities, and minimize the dosage of nanozymes, leading to reduced toxicity to the human body for a real biomedical application prospect. In particular, inflammation occurring in numerous diseases is closely related to reactive oxygen species, and the active oxygen scavenging ability of nanozymes potentially exerts excellent therapeutic effects on inflammatory diseases. In this review, we systematically summarize the structure-activity relationship of nanozymes, including regulation strategies for size and morphology, surface structure, and composition. Based on the structure-activity mechanisms, a series of chemically designed nanozymes developed to target various inflammatory diseases are briefly summarized.

Ligand-assisted deposition of ultra-small Au nanodots on Fe2O3/reduced graphene oxide for flexible gas sensors.

The development of flexible room-temperature gas sensors is important in environmental monitoring and protection. In this contribution, by using 1-octadecanethiol (ODT) as a surface ligand, Au nanodots (NDs) with ultra-small size of ∼1.7 nm were deposited on the surface of α-Fe2O3/reduced graphene oxide (rGO). The Au ND-ODT/α-Fe2O3/rGO composite was fabricated into flexible gas sensors, which could detect NO2 gas down to 200 ppb at room temperature. Compared with α-Fe2O3/rGO, Au ND-ODT/α-Fe2O3/rGO showed enhanced sensing performance because of the beneficial effects of Au NDs, including facilitating the adsorption of NO2 molecules and forming ohmic-like contact with rGO and α-Fe2O3. In addition, the sensing performance of the composite was also influenced by the surface ligands of the Au NDs. Ligands with less polar terminal groups were found to be beneficial to charge transfer in the sensing film. Moreover, Au ND-ODT/α-Fe2O3/rGO-based flexible sensors showed negligible performance deterioration under moderately bent conditions, suggesting their potential to be used in portable and wearable devices.

Realization of Oriented and Nanoporous Bismuth Chalcogenide Layers via Topochemical Heteroepitaxy for Flexible Gas Sensors.

Most van der Waals two-dimensional (2D) materials without surface dangling bonds show limited surface activities except for their edge sites. Ultrathin Bi2Se3, a topological insulator that behaves metal-like under ambient conditions, has been overlooked on its surface activities. Herein, through a topochemical conversion process, ultrathin nanoporous Bi2Se3 layers were epitaxially deposited on BiOCl nanosheets with strong electronic coupling, leading to hybrid electronic states with further bandgap narrowing. Such oriented nanoporous Bi2Se3 layers possessed largely exposed active edge sites, along with improved surface roughness and film forming ability even on inkjet-printed flexible electrodes. Superior room-temperature NO2 sensing performance was achieved compared to other 2D materials under bent conditions. Our work demonstrates that creating nanoscale features in 2D materials through topochemical heteroepitaxy is promising to achieve both favorable electronic properties and surface activity toward practical applications.

Promoting optoelectronic properties of Cs2AgBiBr6 nanocrystals by formation of heterostructures with BiOCl nanosheets.

Lead halide perovskite nanocrystals and their heterostructures have achieved substantial advances in optoelectronics; however, their inherent material instability and lead toxicity have driven research on alternative material systems. Herein, solution-processable heterostructures composed of lead-free double perovskite Cs2AgBiBr6 nanocrystals and BiOCl nanosheets were prepared through a colloidal synthesis method. Defect states were present in BiOCl and benefited carrier generation, recombination and transport in Cs2AgBiBr6. As a result, the light emission of the Cs2AgBiBr6 nanocrystals was greatly enhanced at low temperatures, and the photodetector based on the Cs2AgBiBr6/BiOCl heterostructure exhibited a much improved on-off ratio compared to the device based on Cs2AgBiBr6 alone. Our work highlights the complex nature and impact of two-dimensional heterostructure assembly on the optoelectronic properties of lead-free double perovskites and demonstrates their great potential toward environmentally friendly optoelectronic devices.

Two-Photon Nanoprobe for NIR-II Imaging of Tumour and Biosafety Evaluation.

How to develop near-infrared second window (NIR-II, 1000-1700 nm) fluorescent nanoprobes with a uniform size, strong fluorescence signal and good biosafety owns great clinical requirement. Herein we reported that a two photon fluorescent nanoprobe was developed via encapsulating NIR-II-fluorescent molecules into DSPE-PEG, which was effectively endocytosized by cancer cells, and achieved strong NIR-II fluorescence imaging in cancer cells and cancer cell-beard mice models. Prepared NIR-II-fluorescent nanoprobe exhibited rapid metabolism and excellent biocompatibility. In conclusion, the prepared two photon nanoprobe owns good biosafety, and clinical translational prospect in NIR-II fluorescent imaging of tumour in vivo in near future.

Phylogenomic approaches untangle early divergences and complex diversifications of the olive plant family.

BACKGROUND: Deep-branching phylogenetic relationships are often difficult to resolve because phylogenetic signals are obscured by the long history and complexity of evolutionary processes, such as ancient introgression/hybridization, polyploidization, and incomplete lineage sorting (ILS). Phylogenomics has been effective in providing information for resolving both deep- and shallow-scale relationships across all branches of the tree of life. The olive family (Oleaceae) is composed of 25 genera classified into five tribes with tribe Oleeae consisting of four subtribes. Previous phylogenetic analyses showed that ILS and/or hybridization led to phylogenetic incongruence in the family. It was essential to distinguish phylogenetic signal conflicts, and explore mechanisms for the uncertainties concerning relationships of the olive family, especially at the deep-branching nodes. RESULTS: We used the whole plastid genome and nuclear single nucleotide polymorphism (SNP) data to infer the phylogenetic relationships and to assess the variation and rates among the main clades of the olive family. We also used 2608 and 1865 orthologous nuclear genes to infer the deep-branching relationships among tribes of Oleaceae and subtribes of tribe Oleeae, respectively. Concatenated and coalescence trees based on the plastid genome, nuclear SNPs and multiple nuclear genes suggest events of ILS and/or ancient introgression during the diversification of Oleaceae. Additionally, there was extreme heterogeneity in the substitution rates across the tribes. Furthermore, our results supported that introgression/hybridization, rather than ILS, is the main factor for phylogenetic discordance among the five tribes of Oleaceae. The tribe Oleeae is supported to have originated via ancient hybridization and polyploidy, and its most likely parentages are the ancestral lineage of Jasmineae or its sister group, which is a "ghost lineage," and Forsythieae. However, ILS and ancient introgression are mainly responsible for the phylogenetic discordance among the four subtribes of tribe Oleeae. CONCLUSIONS: This study showcases that using multiple sequence datasets (plastid genomes, nuclear SNPs and thousands of nuclear genes) and diverse phylogenomic methods such as data partition, heterogeneous models, quantifying introgression via branch lengths (QuIBL) analysis, and species network analysis can facilitate untangling long and complex evolutionary processes of ancient introgression, paleopolyploidization, and ILS.

Deposition of Vertically Aligned Ag/Ag2 S Nanoflakes on EGaIn Particles for Humidity Sensing.

Liquid metals, which possess both good electrical conductivity and liquid-like processability, have drawn much attention recently. They are also capable of acting as synthesis templates to guide the deposition of other functional materials. Herein, through an in-situ galvanic replacement reaction assisted by ultrasonication, core-shell EGaIn/Ag particles composed of EGaIn cores and vertically aligned Ag nanoflakes as shells were prepared; they were further sulfurized to yield ternary EGaIn/Ag/Ag2 S core-shell composite particles. A humidity sensor based on EGaIn/Ag/Ag2 S particles showed much higher sensing response than EGaIn and EGaIn/Ag. Such superior performance could be attributed to the n-type semiconducting character of Ag2 S allowing it to receive electrons from water molecules at low humidity, and its highly hydrophilic surface allowing it to absorb more water molecules at higher humidity so as to enable the formation of ion-conductive paths.