Metabolic obesity phenotypes and all-cause mortality among the Chinese oldest-old population: a prospective cohort study.

BACKGROUND: The obesity paradox has been reported among older adults. However, whether the favorable effect of obesity is dependent on metabolic status remains largely unknown. We aimed to explore the association of metabolic obesity phenotypes and their changes with all-cause mortality among the Chinese oldest-old population. METHODS: This prospective cohort study included 1207 Chinese oldest old (mean age: 91.8 years). Metabolic obesity phenotypes were determined by central obesity and metabolic status, and participants were classified into metabolically healthy obesity (MHO), metabolically unhealthy obesity (MUO), metabolically healthy non-obesity (MHN), and metabolically unhealthy non-obesity (MUN). The hazard ratios (HRs) and 95% confidence intervals (95% CIs) were estimated by Cox regression models. RESULTS: During 5.3 years of follow-up, 640 deaths were documented. Compared with non-obesity, obesity was associated with a decreased mortality risk among participants with metabolically healthy (HR, 0.75; 95% CI, 0.63-0.91) while this association was insignificant among metabolically unhealthy. Compared to MHO, MHN (HR, 1.27; 95% CI, 1.06-1.53) and MUN (HR, 1.49; 95% CI, 1.10-2.02) were significantly associated with an increased mortality risk. Compared to those with stable MHO, those transited from MHO to MUO demonstrated a higher mortality risk (HR, 1.81; 95% CI, 1.06-3.11). CONCLUSIONS: MHO predicts better survival among the Chinese oldest-old population. These findings suggest that ensuring optimal management of metabolic health is beneficial and taking caution in weight loss based on the individual body weight for the metabolically healthy oldest-old adults.

Network analysis of posttraumatic stress and posttraumatic growth symptoms among women in subsequent pregnancies following pregnancy loss.

BACKGROUND: Pregnant women who have undergone pregnancy loss often display both posttraumatic stress (PTS) and posttraumatic growth (PTG). However, the precise relationship and structure of symptomatic levels of PTS and PTG have not been well understood. This study aimed to assess the associations between PTS and PTG symptoms in women during subsequent pregnancies following a previous pregnancy loss. METHODS: A total of 406 pregnant women with a history of pregnancy loss were included in this study. The Impact of Events Scale-6 (IES-6) and the Posttraumatic Growth Inventory Short Form (PTGI-SF) were used to assess symptoms of PTS and PTG, respectively. The Graphical Gaussian Model was employed to estimate the network model. Central symptoms and bridge symptoms were identified based on "expected influence" and "bridge expected influence" indices, respectively. The stability and accuracy of the network were examined using the case-dropping procedure and nonparametric bootstrapped procedure. RESULTS: The network analysis identified PTG3 ("Ability to do better things") as the most central symptom, followed by PTS3 ("Avoidance of thoughts") and PTG6 ("New path for life") in the sample. Additionally, PTS3 ("Avoidance of thoughts") and PTG9 ("Perception of greater personal strength") were bridge symptoms linking PTS and PTG clusters. The network structure was robust in stability and accuracy tests. CONCLUSIONS: Interventions targeting the central symptoms identified, along with key bridge symptoms, have the potential to alleviate the severity of PTS experienced by women with a history of pregnancy loss and promote their personal growth.

Association between dietary diversity changes and frailty among Chinese older adults: findings from a nationwide cohort study.

BACKGROUND: Dietary diversity has been suggested as a potential preventive measure against frailty in older adults, but the effect of changes in dietary diversity on frailty is unclear. This study was conducted to examine the association between the dietary diversity score (DDS) and frailty among older Chinese adults. METHODS: A total of 12,457 adults aged 65 years or older were enrolled from three consecutive and nonoverlapping cohorts from the Chinese Longitudinal Healthy Longevity Survey (the 2002 cohort, the 2005 cohort, and the 2008 cohort). DDS was calculated based on nine predefined food groups, and DDS changes were assessed by comparing scores at baseline and the first follow-up survey. We used 39 self-reported health items to assess frailty. Cox proportional hazard models were performed to examine the association between DDS change patterns and frailty. RESULTS: Participants with low-to-low DDS had the highest frailty incidence (111.1/1000 person-years), while high-to-high DDS had the lowest (41.1/1000 person-years). Compared to the high-to-high group of overall DDS pattern, participants in other DDS change patterns had a higher risk of frailty (HRs ranged from 1.25 to 2.15). Similar associations were observed for plant-based and animal-based DDS. Compared to stable DDS changes, participants with an extreme decline in DDS had an increased risk of frailty, with HRs of 1.38 (1.24, 1.53), 1.31 (1.19, 1.44), and 1.29 (1.16, 1.43) for overall, plant-based, and animal-based DDS, respectively. CONCLUSIONS: Maintaining a lower DDS or having a large reduction in DDS was associated with a higher risk of frailty among Chinese older adults. These findings highlight the importance of improving a diverse diet across old age for preventing frailty in later life.

Leisure-time activities and disability among Chinese community-dwelling oldest old: evidence from the Chinese Longitudinal Healthy Longevity Study.

With the acceleration of population aging, disability in older adults is a growing public health problem; however, little is known about the role of specific leisure-time activities in affecting disability. This study prospectively examined the association of leisure-time activities with disability among the Chinese oldest old. A total of 14 039 adults aged 80 years or older (median age of 89.8 years) were enrolled from the Chinese Longitudinal Healthy Longevity Survey from 1998 to 2014. Disability was defined as the presence of concurrent impairment in activities of daily living and physical performance. Cox proportional hazards models were used to estimate the associations between leisure-time activities and disability. During a mean of 4.2 years (2.7 years) of follow-up, 4487 participants developed disability. Compared with participants who never engaged in leisure-time activities, participants who engaged in almost daily activities, including gardening, keeping domestic animals or pets, playing cards or mahjong, reading books or newspapers, and watching TV or listening to the radio had a lower risk of disability, with HRs of 0.78 (0.69-0.88), 0.64 (0.58-0.70), 0.74 (0.63-0.86), 0.74 (0.65-0.84), and 0.84 (0.77-0.90), respectively. Moreover, the risk of disability gradually decreased with participation in an increasing number of those leisure-time activities (P for trend <0.001). Frequent engagement in leisure-time activities was associated with a lower risk of disability among the Chinese oldest old. This study highlights the importance of incorporating a broad range of leisure-time activities into the daily lives of older adults.

Latent trajectories of anxiety and depression among women during subsequent pregnancy following pregnancy loss.

AIM: To determine the longitudinal trajectories of anxiety and depression among pregnant women who have experienced pregnancy loss, and to explore the association between post-traumatic stress symptoms (PTSS) related to pregnancy loss and these trajectories. DESIGN: A prospective longitudinal study. METHODS: Between October 2022 and August 2023, pregnant women with a history of pregnancy loss were recruited from four hospitals in Guangdong Province, China. Eligible participants were screened for PTSS related to pregnancy loss upon enrolment. Anxiety and depression symptoms were assessed in early, mid and late pregnancy using the Pregnancy-related Anxiety Questionnaire-Revised 2 and the Patient Health Questionnaire-9, respectively. Latent class growth analysis was employed to categorize anxiety and depression trajectories, and multinomial logistic regression analysis was conducted to examine the association between PTSS and these trajectories. RESULTS: Of the 388 participants included in the analysis, 158 individuals (40.7%) reported high PTSS scores. The best-fitting models identified three trajectories for both anxiety and depression: low (anxiety: 35.6%, depression: 48.7%), moderate (anxiety: 44.8%, depression: 40.5%) and high (anxiety: 19.6%, depression: 10.8%). Pregnant women with high PTSS levels were significantly more likely to experience moderate-to-high trajectories of anxiety and depression compared to those with low PTSS levels. CONCLUSION: Pregnant women who have experienced pregnancy loss exhibit higher incidences of elevated anxiety and depression trajectories. Screening for PTSS and targeted supportive care are recommended to alleviate anxiety and depressive symptoms in this population. IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE: This study underscores the importance of early psychological screening and tailored interventions for pregnant women with a history of pregnancy loss. Trauma-informed care should be prioritized to mitigate anxiety and depression trajectories in this vulnerable population. PATIENT OR PUBLIC CONTRIBUTION: There was no patient or public involvement.

Development and validation of the Sources of Meaning in Life Scale for the Elderly in China.

OBJECTIVES: People who find meaning in life can endure 'any' pain. However, there were no tools to investigate elderly individuals' sources of meaning in life in China. This study aimed to develop the Sources of Meaning in Life Scale for the Elderly (SMSE), and examine the validation and reliability in Chinese elderly. METHODS: A 43-item pool of SMSE was formed by combining the preliminary interview and literature review. A cross-sectional survey of 627 elderly people was then conducted in two community health service centers, two hospitals, and two nursing homes in Guangzhou by the convenience sampling method. Test-retest reliability was assessed with 24 elderly persons. RESULTS: Six dimensions, containing family (four items), social support (four items), value (seven items), life security (four items), personal development (four items), and leisure activity (five items) explained 62.16% of the variance in total. Confirmatory factor analysis model fitting indices were χ2 = 694.652, df = 330, χ2/df = 2.105, SRMR = 0.0695, GFI = 0.853, IFI = 0.905, TLI = 0.889, CFI = 0.903, and RMSEA = 0.062. The Cronbach's alpha value of the scale was 0.924, while that of each dimension was between 0.727 and 0.870. The inter-class correlation (ICC) of the scale was 0.856. CONCLUSION: The SMSE has good reliability and validity that can be used to evaluate the sources of meaning and meaning in life for the elderly.

Different effects of bisphenol-A on memory behavior and synaptic modification in intact and estrogen-deprived female mice.

Bisphenol-A (BPA) has the capability of interfering with the effects of estrogens on modulating brain function. The purpose of this study was to investigate the effects of BPA on memory and synaptic modification in the hippocampus of female mice under different levels of cycling estrogen. BPA exposure (40, 400 µg/kg/day) for 8 weeks did not affect spatial memory and passive avoidance task of gonadally intact mice but improved ovariectomy (Ovx)-induced memory impairment, whereas co-exposure of BPA with estradiol benzoate (EB) diminished the rescue effect of EB on memory behavior of Ovx mice. The results of morphometric measurement showed that BPA positively modified the synaptic interface structure and increased the synaptic density of CA1 pyramidal cell in the hippocampus of Ovx females, but inhibited the enhancement of EB on synaptic modification and synaptogenesis of Ovx mice. Furthermore, BPA up-regulated synaptic proteins synapsin I and PSD-95 and NMDA receptor NR2B but inhibited EB-induced increase in PSD-95 and NR2B in the hippocampus of Ovx mice. These results suggest that BPA interfered with normal hormonal regulation in synaptic plasticity and memory of female mice as a potent estrogen mimetic and as a disruptor of estrogen under various concentrations of cycling estrogen.

Associations between pregnancy loss and common mental disorders in women: a large prospective cohort study.

Background: Increasing evidence suggests that pregnancy loss can lead to negative emotional outcomes, such as anxiety and depression, for women. However, limited knowledge exists regarding the long-term risk of mental disorders among individuals who have experienced pregnancy loss. Objective: To investigate the associations between pregnancy loss and the risk of common mental disorders. Methods: In the UK Biobank, a total of 218,990 women without any mental disorder at baseline were enrolled between 2006 and 2010 and followed until October 2022. Information on the history of pregnancy loss was obtained through self-reported questionnaires at baseline. Cox proportional hazard regression models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between pregnancy loss and common mental disorders. Results: During a median follow-up time of 13.36 years, there were 26,930 incident cases of common mental disorders. Incidence rates of common mental disorders were elevated among women with a history of stillbirth (HR 1.15, 95% CI: 1.07-1.23), miscarriage (HR 1.06, 95% CI: 1.02-1.10), or pregnancy termination (HR 1.21, 95% CI: 1.17-1.25) compared to those without such experiences. Furthermore, the risk of common mental disorders significantly increased in women with two or more miscarriages (HR 1.14, 95% CI: 1.08-1.19) or two or more pregnancy terminations (HR 1.39, 95% CI: 1.30-1.48). Conclusions: Pregnancy loss is associated with an increased risk of common mental disorders in women later in life. These findings may contribute to the enhancement of long-term monitoring and prevention of common mental disorders for women with such a history.

Psychological distress in subsequent pregnancy among women with a history of pregnancy loss: A latent profile analysis.

BACKGROUND: Women who have undergone pregnancy loss can experience a range of psychological distress during subsequent pregnancies; however, the outcomes may vary based on individual circumstances. OBJECTIVE: To explore the potential patterns of psychological distress for pregnant women with a history of pregnancy loss, and to investigate the impact of factors related to pregnancy loss on these patterns. METHODS: From October 2022 to August 2023, the participants were recruited from four medical centers in Guangdong Province, China. They completed a questionnaire survey comprising sociodemographic and obstetric characteristics, the Perceived Stress Scale-4 (PSS-4), the Impact of Event Scale-Revised (IES-R), the Pregnancy-related Anxiety Questionnaire-Revised 2 (PRAQ-R2), and the Patient Health Questionnaire-9 (PHQ-9). Latent profile analysis was used to determine optimal patterns of psychological distress. The logistic regression was conducted to assess the associations between the number of pregnancy loss, types of pregnancy loss, inter-pregnancy interval, and distinct psychological distress patterns. RESULTS: A total of 446 pregnant women with a history of pregnancy loss were included for formal analysis. Three distinct profiles were identified, namely the "mild psychological distress" (34.1 %), "moderate psychological distress" (57.8 %), and "severe psychological distress" (8.1 %). Recurrent pregnancy loss was associated with increased risks of both moderate (adjusted odds ratio [aOR] 2.45, 95 % confidence interval [CI]: 1.42-4.24; P = 0.001) and severe psychological distress (aOR 2.93, 95 %CI: 1.25-6.83; P = 0.013). Furthermore, compared to women who conceived after 6 months of pregnancy loss, those who conceived within 6 months of pregnancy loss were more likely to be categorized into the group of moderate psychological distress (aOR 2.00, 95 % CI: 1.21-3.30; P = 0.007). CONCLUSIONS: Approximately two-thirds of pregnant women with a history of pregnancy loss exhibit moderate to severe psychological distress. Such individuals could benefit from early screening and targeted psychological interventions, particularly those who have encountered recurrent pregnancy loss and those who conceive shortly after a pregnancy loss.

Study on measurement and drivers of low-carbon tourism eco-efficiency: evidence from Jiangsu Province.

In order to explore practical ways to test the eco-efficiency of low-carbon tourism and its drivers in Jiangsu Province, this paper empirically tests the effects of selected driving variables on the eco-efficiency of low-carbon tourism using a spatial lag model. It measures the eco-efficiency of low-carbon tourism in 13 prefecture-level cities in Jiangsu Province based on a modified two-stage network SBM model. According to the direct effect test results, per capita tourism income (PTI) had the most significant effect on the eco-efficiency of low-carbon tourism, with an impact coefficient of 0.5437, environmental pollution governance (EPG) had the second most significant effect, energy consumption intensity (ECI) and carbon emission intensity (CEI) had adverse effects with effect coefficients of - 0.3815 and - 0.4415, respectively, and R&D input intensity (RDII) had the slightest effect on the eco-efficiency of low-carbon tourism, with an impact coefficient of - 0.0836. According to indirect effect test results, RDII has the most significant positive effect with a coefficient of 0.3848, PTI has the second most significant adverse effect on the eco-efficiency of low-carbon tourism with a coefficient of - 0.3245, ECI has the third most significant adverse effect with a coefficient of - 0.2567, EPG has the fourth largest positive effect with a coefficient of 0.2162, and CEI has the slightest adverse effect with an impact coefficient of - 0.2147.

Dietary Diversity Changes and Cognitive Frailty in Chinese Older Adults: A Prospective Community-Based Cohort Study.

Evidence for the effects of dietary diversity changes and cognitive frailty (CF) in the older adults is not clear. This study aimed to investigate the relationship between dietary diversity changes and CF in older adults Chinese. A total of 14,382 participants (mean age: 82.3 years) were enrolled. Dietary diversity scores (DDSs) were collected and calculated using a food frequency questionnaire. DDS changes between baseline and first follow-up were categorized into nine patterns. The associations between DDS changes and the incidence of CF were estimated using Cox proportional hazards models. During an 80,860 person-year follow-up, 3023 CF cases were identified. Groups with a decrease in DDS had increased CF risk compared with the high-to-high DDS group, with adjusted hazard ratios (HRs; 95% confidence intervals (Cis)) of 1.30 (1.06, 1.59), 2.04 (1.51, 2.74), and 1.81 (1.47, 2.22) for high-to-medium, high-to-low, and medium-to-low groups, respectively. Lower overall DDS groups were associated with greater CF risks, with HRs (95% CIs) of 1.49 (1.19, 1.86) for the low-to-medium group and 1.96 (1.53, 2.52) for the low-to-low group. Compared with the high-to-high group, significant associations with CF were found in other DDS change groups; HRs ranged from 1.38 to 3.12 for the plant-based DDS group and from 1.24 to 1.32 for the animal-based DDS group. Additionally, extreme and moderate declines in overall DDS increased CF risk compared with stable DDS, with HRs (95% CIs) of 1.67 (1.50, 1.86) and 1.13 (1.03, 1.24), respectively. In conclusion, among older adults, a declining or persistently low DDS and a moderately or extremely declining DDS were linked to higher incident CF. Plant-based DDS changes correlated more strongly with CF than animal-based DDS changes.

Dietary diversity and frailty among older Chinese people: evidence from the Chinese Longitudinal Healthy Longevity Study.

BACKGROUND: Dietary diversity is widely advocated as a means to promote health, but little is known regarding whether the beneficial effects still apply in older adults. OBJECTIVE: To examine the association between the dietary diversity score (DDS) and frailty among older Chinese adults. METHODS: A total of 13,721 adults aged ≥65 y without frailty at baseline were enrolled. The DDS at baseline was constructed based on 9 items of a food frequency questionnaire. We used 39 self-reported health items to construct a frailty index (FI), with FI ≥ 0.25 indicating frailty. Cox models with restricted cubic splines were used to evaluate the dose-response relationships of DDS (continuous) with frailty. In addition, Cox proportional hazard models were used to examine the association between DDS (categorized as scores ≤4, 5-6, 7, and ≥8) and frailty. RESULTS: During the mean follow-up of 5.94 y, 5250 participants met the criteria for frailty. Each 1-unit increase in DDS corresponded to a 5% lower risk of frailty (hazard ratio [HR]; 0.95; 95% CI: 0.94, 0.97]. Compared with participants with DDS ≤4 points, those with a DDS of 5-6, 7, and ≥8 points exhibited a lower frailty risk, with HRs of 0.79 (95% CI: 0.71, 0.87), 0.75 (95% CI: 0.68, 0.83), and 0.74 (95% CI: 0.67, 0.81), respectively (P-trend < 0.001). Protein-rich food items, such as meat; eggs; and beans, were associated with protective effects against frailty. In addition, a significant association was observed between higher consumption of 2 high-frequency foods, tea and fruits, and lower risk of frailty. CONCLUSIONS: A higher DDS was associated with a lower risk of frailty among older Chinese adults. This study highlights the importance of a diverse diet as a potential modifiable behavioral factor for preventing frailty in older Chinese adults.

Development and Psychometric Validation of the Perinatal Bereavement Care Competence Scale for Midwives.

PURPOSE: The aim of this paper is to develop a scale for measuring the perinatal bereavement care competence of midwives and assess its psychometric properties. METHODS: The Perinatal Bereavement Care Competence Scale was developed in four phases. (1) Item generation: 75 items were formulated based on a literature review and interviews with midwives. (2) Delphi expert consultation: 15 experts evaluated whether the items were clear/appropriate/relevant to the questionnaire dimensions, and the items were optimized. (3) Pilot test: The comprehensibility, acceptability, and time required to complete the questionnaire by midwives were assessed. (4) Evaluation of reliability and validity: The scale was validated by initial item analysis, exploratory and confirmatory factor analyses, and internal consistency reliability and test-retest reliability. RESULTS: The final scale consisted of six dimensions and 25 items: maintaining belief (three items), knowing (four items), being with (six items), preserving dignity (four items), enabling (five items), and self-adjustment (three items). Exploratory factor analysis yielded a six-factor structure that was consistent with the theoretical framework and explained 70.8% of the total variance. Confirmatory factor analysis indicated a good fit for the six-factor model. Cronbach's α for the scale was 0.931, and the test-retest reliability coefficient was 0.968. CONCLUSION: The Perinatal Bereavement Care Competence Scale is a valid and reliable instrument for measuring the competence of midwives in caring for bereaved parents who have experienced perinatal loss.

Experience of undergraduate midwifery students faced with perinatal death in clinical practice: A qualitative study.

BACKGROUND: Student midwives often encounter perinatal loss including stillbirth and neonatal death as part of their clinical training. There has been limited research on how student midwives cope with perinatal death. OBJECTIVE: To explore the experiences of undergraduate midwifery students facing perinatal death during their internships. DESIGN: Qualitative research design based on interpretive phenomenological approach and COREQ-guided reporting. SETTING: Tertiary maternal and child care center or general hospital. PARTICIPANTS: Undergraduate midwifery students from a medical university in Guangzhou, China. METHODS: Study participants were recruited through purposive sampling. Semi-structured in-depth interviews were conducted between October 2020 and March 2021 with 12 midwifery students. Transcripts of the interviews were analyzed using Diekelmann's interpretive method. RESULTS: Four themes were identified from the data: unavoidable anxiety and avoidance response; overwhelming fear and taboos related to death; self-blame and emotional inhibition; and ethical conflict and reflection on practice. CONCLUSIONS: Undergraduate midwifery students believed they were ill-prepared to care for women who experienced perinatal loss, consciously endured their own negative emotions such as anxiety and fear, and hoped for improved bereavement and stillbirth care in future clinical practice. Students valued support from the bereavement midwife and identified effective strategies that would help them cope with their feelings. It is recommended that adequate education and emotional support be provided to midwifery students, who should be encouraged to provide appropriate care to grieving families.

Tough Underwater Super-tape Composed of Semi-interpenetrating Polymer Networks with a Water-Repelling Liquid Surface.

Despite recent advances in bioinspired underwater adhesives, achieving tough, fast, and stable adhesion in aqueous environments is still challenging. Here, an underwater super-tape with semi-interpenetrating polymer networks (SIPNs) and a water-repelling liquid surface is synthesized. In the SIPN, the linear chains easily diffuse to adapt to the adherends, and the cross-linked chains provide the super-tape with high dimensional stability. Meanwhile, both the linear and cross-linked chains bear many catechol groups, which can not only vigorously interact with the adherends but also form numerous hydrogen bonds serving as sacrificial bonds in the SIPN. Thus, the super-tape shows both high interfacial adhesion and cohesive energy. Moreover, the super-tape is covered with a water-repelling liquid surface by spraying it with traces of a hydrophobic solvent. It is demonstrated that the hydrophobic solvent absorbed on the surface of the super-tape can remove water between the tape and adherends, enabling their intimate contact to form a strong interaction. As such, the super-tape shows excellent instant adhesion property under water, and the adhesive strength and toughness increase with time and reach their maximum values at around 5 h. The maximum debonding energy of the super-tape reaches 3933 J m-2, which is much higher than those of existing double-sided tapes.

Rapid effect of bisphenol A on glutamate-induced Ca2+ influx in hippocampal neurons of rats.

Intracellular Ca2+ signaling plays an essential role in synaptic plasticity. This study examined the effect of BPA on concentration of intracellular Ca2+ ([Ca2+]i) by measuring fluorescence intensity of Ca2+ in hippocampal neurons in vitro. The results showed that BPA for 30 min exerted dose-dependently dual effects on glutamate-elevated [Ca2+]i: BPA at 1-10 µM suppressed but at 1-100 nM enhanced glutamate-raised [Ca2+]i. BPA-potentiated [Ca2+]i was blocked by the antagonist of NMDA receptor and was eliminated by an estrogen-related receptor gamma (ERRγ) antagonist rather than an AR antagonist. Both inhibitors of MAPK/ERKs and MAPK/p38 blocked BPA-enhanced [Ca2+]i. Co-treatment of BPA with 17ß-E2 or DHT eliminated the enhancement of 17ß-E2, DHT, and BPA in glutamate-elevated [Ca2+]i. These results suggest that BPA at nanomole level rapidly enhances Ca2+ influx through NMDA receptor by ERRγ-mediated MAPK/ERKs and MAPK/p38 signaling pathways. However, BPA antagonizes both estrogen and androgen enhancing NMDA receptor-mediated Ca2+ influx in hippocampal neurons.

[Study on the preparation and physicochemical properties of fish swim bladder membrane].

OBJECTIVE: To manufacture fish swim bladder membrane material by crosslinking techniques, and to explore its physical and chemical properties and cytotoxicity. METHODS: After decellularization, the swim bladders were randomly divided into two groups. The swim bladders were treated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) crosslinking method, surface hole making, and freeze-drying in crosslinking group, and only surface hole making and freeze-drying in non-crosslinking group. The physical and chemical properties of the materials were observed, including microstructure by scanning electron microscopy (SEM), mechanical properties (tensile strength and breaking elongation) by universal tensile machine, hydrophilicity by contact angle measuring instrument, porosity by ethanol infiltration method, degradation performance in vitro and thermal stability test, and the components of materials by infrared spectrum analysis. Mouse fibroblasts (L929) were cultured with the extracts of two groups of materials in order to determine the cytotoxicity of materials by using cell counting kit 8 (CCK-8) method. RESULTS: The porous structure and rough surface of materials were observed by SEM. Compared with the non-crosslinking group, the tensile stress of the crosslinking group was higher, the breaking elongation was lower, and the porosity increased, showing significant differences ( P<0.05). There was no significant difference in contact angle between the two groups ( P>0.05). The degradation was faster within the first 7 days and then tended to be smooth in the two groups. But the degradation rates of crosslinking group were significantly lower than those of non-crosslinking group ( P<0.05). Differential scanning calorimeter showed that the denaturation temperature of the crosslinking group was (75.2±1.3)℃, which was significantly higher than that of the non-crosslinking group [(68.5±0.4)℃] ( t=4.586, P=0.002). Compared with the non-crosslinking group, the crosslinking group produced new C=O bond and N-H bond, and no other new groups were introduced into the cross-linking group. CCK-8 method showed that the absorbance values of the crosslinking group and the non-crosslinking group were not significant when compared with the positive control group ( P>0.05). CONCLUSION: The fish swim bladder membrane obtained by crosslinking treatment with EDC/NHS method has good physical and chemical properties, no cytotoxicity, and is expected to be used as a dura mater repair material.

Ultra-Tough, Strong, and Defect-Tolerant Elastomers with Self-Healing and Intelligent-Responsive Abilities.

Mechanical strength, toughness, and defect tolerance are usually exclusive in most artificial materials. Herein, inspired by many biomaterials that overcome this tradeoff by integrating soft and hard ingredients through elaborate structural designs, we report a facile latex-assembly method to fabricate ultra-tough, strong, and defect-tolerant elastomers. The elastomers are featured by a microscopic inverse opal-mimetic rigid skeleton of dynamically cross-linked chitosan and a continuous soft matrix of vulcanized natural rubber. Such structural design enables the load-bearing capability, sacrificial property, and self-healing ability of the skeleton, the stress redistribution and extensibility of the matrix, and the stiffness variation between hard and soft ingredients, thereby imparting the elastomers with outstanding mechanical strength and defect tolerance, as well as extremely high toughness of 122 KJ m-2, which is even higher than that of the current state-of-the-art titanium alloys. Moreover, the elastomers show prominent humidity sensitivity due to the hydrophilic nature of the chitosan skeleton. Harnessing these advantages, we fabricate a walking robot triggered by humidity variation and shoes that are able to regulate temperature and humidity. The concept of designing a rigid sacrificial skeleton within a soft continuous matrix on the microscale is quite general, enabling the development of high-performance and intelligent materials for emerging applications.