CASK and FARP localize two classes of post-synaptic ACh receptors thereby promoting cholinergic transmission.

Changes in neurotransmitter receptor abundance at post-synaptic elements play a pivotal role in regulating synaptic strength. For this reason, there is significant interest in identifying and characterizing the scaffolds required for receptor localization at different synapses. Here we analyze the role of two C. elegans post-synaptic scaffolding proteins (LIN-2/CASK and FRM-3/FARP) at cholinergic neuromuscular junctions. Constitutive knockouts or muscle specific inactivation of lin-2 and frm-3 dramatically reduced spontaneous and evoked post-synaptic currents. These synaptic defects resulted from the decreased abundance of two classes of post-synaptic ionotropic acetylcholine receptors (ACR-16/CHRNA7 and levamisole-activated AChRs). LIN-2's AChR scaffolding function is mediated by its SH3 and PDZ domains, which interact with AChRs and FRM-3/FARP, respectively. Thus, our findings show that post-synaptic LIN-2/FRM-3 complexes promote cholinergic synaptic transmission by recruiting AChRs to post-synaptic elements.

A WDR47 homolog facilitates ciliogenesis by modulating intraflagellar transport.

Cilia are conserved organelles found in many cell types in eukaryotes, and their dysfunction causes defects in environmental sensing and signaling transduction; such defects are termed ciliopathies. Distinct cilia have cell-specific morphologies and exert distinct functions. However, the underlying mechanisms of cell-specific ciliogenesis and regulation are unclear. Here, we identified a WD40-repeat (WDR) protein, NMTN-1 (the homolog of mammalian WDR47), and show that it is specifically required for ciliogenesis of AWB chemosensory neurons in C. elegans. NMTN-1 is expressed in the AWB chemosensory neuron pair, and is enriched at the basal body (BB) of the AWB cilia. Knockout of nmtn-1 causes abnormal AWB neuron cilia morphology, structural integrity, and induces aberrant AWB-mediated aversive behaviors. We further demonstrate that nmtn-1 deletion affects movement of intraflagellar transport (IFT) particles and their cargo delivery in AWB neurons. Our results indicate that NMTN-1 is essential for AWB neuron ciliary morphology and function, which reveal a novel mechanism for cell-specific ciliogenesis. Given that WDR47/NMTN-1 is conserved in mammals, our findings may help understanding of the process of cell-specific ciliogenesis and provide insights for treating ciliopathies.

Cytokines as drivers: Unraveling the mechanisms of epithelial-mesenchymal transition in COVID-19 lung fibrosis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), like other viruses, can induce proliferation of myofibroblasts and even lead to fibrosis in the lung. Epithelial-mesenchymal transition (EMT) is thought to play an essential role in the pathogenesis of Coronavirus disease 19 (COVID-19). EMT is originally a critical process that regulates the development of different tissues in the embryo, but in inflammatory situations, EMT tries to be activated again to control inflammation or even heal inflammatory damage. However, in pathological situations, such as chronic viral infections (e.g., COVID-19) or pulmonary fibrosis initiation, this benign healing transforms into sinister nature, pushing the lung into the fibrotic process. Notably, the cytokines released by inflammatory cells and the chronic inflammatory microenvironment shared by fibrotic cells promote each other as critical factors in the induction of pathological EMT. In the induction of SARS-CoV-2 virus, cytokines are an essential mediator of EMT transformation, and a summary of whether COVID-19 patients, during the infection phase, have many persistent inflammatory mediators (cytokines) that are a causative factor of EMT has not yet appeared. The following common signaling drivers, including Transforming growth factor beta (TGF-ß), cytokines, Notch signaling pathway, Wnt and hypoxia signaling pathways, drive the regulation of EMT. In this review, we will focus on 3 key EMT signaling pathways: TGF-ß, Leucine zipper transcription factor like 1 (LZTFL1) and the common interleukin family expressed in the lung. TGF-ß-induced SNAIL and LZTFL1 were identified as regulatory EMT in COVID-19. For cytokines, the interleukin family is a common inducer of EMT and plays an essential role in the formation of the microenvironment of fibrosis. We sought to demonstrate that cytokines act as "communicators" and build the "microenvironment" of fibrosis together with EMT as a "bridge" to induce EMT in fibrosis. The mechanisms utilized by these two pathways could serve as templates for other mesenchymal transformations and provide new potential therapeutic targets.

Cadmium induces placental glucocorticoid barrier damage by suppressing the cAMP/PKA/Sp1 pathway and the protective role of taurine.

Cadmium (Cd) exposure during pregnancy damages the placental glucocorticoid (GC) barrier, exposes the foetus to excess corticosterone (CORT) levels, and eventually inhibits foetal development. In addition, taurine (Tau) alleviates the toxicity of Cd on liver and kidney, but limited data are available on the role of Tau against the toxicity of heavy metals on female reproduction and fetal development. The present study was conducted to investigate the specific mechanism of Cd-induced placental GC barrier damage and the protective role of Tau. Pregnant rats were administered CdCl2 (1 mg/kg/day) and Tau (100, 200, or 300 mg/kg/day) by gavage from gestational day (GD) 0 to 19. The data showed that CdCl2 increased the foetal growth restriction (FGR) rate of the offspring, and the levels of CORT in the placental, maternal and foetal serum. Treatment with Tau significantly reversed the impact of Cd on both maternal and fetal parameters. Additionally, Tau can attenuate Cd-induced inhibition of 11ß-hydroxysteroid dehydrogenase 2 (11ß-HSD2) and specificity protein 1 (Sp1) in vivo and vitro. Furthermore, Sp1-siRNA alone reduced 11ß-HSD2 levels and had a further inhibitory effect when the cells were treated with Cd simultaneously. Moreover, Cd suppressed cAMP/PKA signalling. Forskolin (adenylate cyclase agonist) pretreatment activated cAMP/PKA signalling and restored the Cd-induced downregulation of Sp1 and 11ß-HSD2. Tau alleviated the Cd-induced decrease of Sp1 via activating cAMP/PKA signalling. Therefore, the results highlight that Tau protects against Cd-induced impairments in GC barrier damage by upregulating the cAMP/PKA/Sp1 pathway in placental trophoblasts.

Selenium attenuates the cadmium-induced placenta glucocorticoid barrier damage by up-regulating the expression of specificity protein 1.

Cadmium (Cd) is an environmental pollutant and pregnant women are especially susceptible to the effects of exposure to Cd. Our previous study found Cd can be accumulated in the placenta and causes fetal growth restriction (FGR) through damage the placental glucocorticoid barrier. Selenium (Se), as an essential micronutrient, can allivate Cd-induced toxicity. In this study, we aim to explore the protective mechanism of Se against Cd-induced the placental glucocorticoid barrier damage and FGR. Pregnant Sprague Dawley (SD) rats were exposed to CdCl2 (1 mg/kg/day) and Na2 SeO3 (0.1-0.2-0.3 mg/kg/day) by gavage from gestational day (GD) 0 to GD 19. The results showed that reduced fetal weight, increased corticosterone concentrations in the maternal and fetal serum, and impaired placental labyrinth layer blood vessel development, appeared in pregnant rats after Cd exposure and improved after treated with Se. In cell experiments, we confirmed that Se reduces Cd-induced apoptosis. Moreover, Se can abolish Cd-induced 11ß-HSD2 and specificity protein 1 (Sp1) decreasing in vivo and vitro. In human JEG-3 cells, the knockdown of Sp1 expression by small interfering RNA can suppressed the protective effect of Se on Cd-induced 11ß-HSD2 decreasing. In general, our results demonstrated that Se is resistant to Cd-induced FGR through upregulating the placenta barrier via activation of the transcription factor Sp1.

Porous Liquid-Crystalline Networks with Hydrogel-Like Actuation and Reconfigurable Function.

A porous liquid-crystalline network (LCN), prepared by using a template method, was found to exhibit peculiar actuation functions. The creation of porosity makes the initially hydrophobic LCN behave like a hydrogel, capable of absorbing a large volume of water (up to ten times the sample size of LCN). When the amount of absorbed water is relatively small (about 100 % swelling ratio), the porous LCN displays anisotropic swelling in water and, in the same time, the retained uniaxial alignment of mesogens ensures a thermally induced shape change associated with a LC-isotropic phase transition. Combining the characteristic actuation mechanisms of LCN (order-disorder transition of mesogens) and hydrogel (water absorption), such porous LCNs can be explored for versatile stimuli-triggered shape transformations. Moreover, the porosity enables loading/removal/reloading of functional fillers such as ionic liquids, photothermal dyes and fluorophores, which imparts the porous LCN actuator with reconfigurable functions such as ionic conductivity, light-driven locomotion, and emissive color.

Association between HLA alleles and Epstein-Barr virus Zta-IgA serological status in healthy males from southern China.

BACKGROUND: Nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV) associated cancer, exhibits an extremely high incidence in southern Chinese. Given that human leukocyte antigen (HLA) plays critical roles in antigen presentation and relates to NPC susceptibility, it is speculated that certain HLA variants may affect EBV reactivation, which is a key pathogenic factor of NPC. Therefore, we attempted to identify HLA alleles associated with the indicator of EBV reactivation, Zta-IgA, in healthy males from NPC endemic area. METHODS: HLA alleles of 1078 healthy males in southern China from the 21-RCCP study were imputed using genome-wide single nucleotide polymorphism data. EBV Zta-IgA in blood samples were measured using an enzyme-linked immunosorbent assay. Multiple logistic regression analysis was used to evaluate the effect of HLA allele on Zta-IgA serological status and its potential joint association with smoking. The binding affinity for Zta-peptide was predicted using NetMHCIIpan 4.0. RESULTS: HLA-DRB1*09:01 was found to be associated with a higher risk of Zta-IgA seropositivity (odds ratio = 1.80, 95% confidence interval = 1.32-2.45; p = 1.82 × 10-4 ). Compared with non-smokers without HLA-DRB1*09:01, the effect size increased to 2.19- and 3.70-fold for the light and heavy smokers carrying HLA-DRB1*09:01, respectively. Furthermore, HLA-DRB1*09:01 showed a stronger binding affinity to Zta peptide than other HLA-DRB1 alleles. CONCLUSIONS: Our study highlighted the pivotal role of genetic HLA variants in EBV reactivation and the etiology of NPC. Smokers with HLA-DRB1*09:01 have a significantly higher risk of being Zta-IgA seropositive, which indicates the necessity of smoking cessation in certain high-risk populations and also provide clues for further research on the etiology of NPC.

A fecal-based test for the detection of advanced adenoma and colorectal cancer: a case-control and screening cohort study.

BACKGROUND: Colorectal cancer (CRC) is the leading cause of cancer death worldwide. Screening is a confirmed way to reduce the incidence and mortality rates of CRC. This study aimed to identify a fecal-based, noninvasive, and accurate method for detection of colorectal cancer (CRC) and advanced adenoma (AA). METHODS: Through detection in tissue (n = 96) and fecal samples (n = 88) and tested in an independent group of fecal samples (n = 294), the methylated DNA marker ITGA4 and bacterial markers Fusobacterium nucleatum (Fn) and Pepetostreptococcusanaerobius (Pa) were identified from the candidate biomarkers for CRC and AA detection. A prediction score (pd-score) was constructed using the selected markers and fecal immunochemical test (FIT) for distinguishing AA and CRC from healthy subjects by logistic regression method. The diagnostic performance of the pd-score was compared with FIT and validated in the external validation cohort (n = 117) and in a large CRC screening cohort. RESULTS: The pd-score accurately identified AA and CRC from healthy subjects with an area under the curve (AUC) of 0.958, at a specificity of 91.37%; the pd-score showed sensitivities of 95.38% for CRC and 70.83% for AA, respectively. In the external validation cohort, the sensitivities of the pd-score for CRC and AA detection were 94.03% and 80.00%, respectively. When applied in screening, the pd-score identified 100% (11/11) of CRC and 70.83% (17/24) of AA in participants with both colonoscopy results and qualified fecal samples, showing an improvement by 41.19% compared to FIT. CONCLUSIONS: The current study developed a noninvasive and well-validated approach for AA and CRC detection, which could be applied widely as a diagnostic and screening test.

Red pitaya peels-based carbon dots for real-time fluorometric and colorimetric assay of Au3+, cellular imaging, and antioxidant activity.

The synthesis of fascinating multifunctional carbon dots (CDs) attracted immense attention. Here, a facile solvothermal treatment of red pitaya peels in acetic acid produced CDs (designated as ACDs, excitation/emission wavelengths at 357/432 nm). ACDs with high sp2-hybridized carbon and carboxylic group contents can rapidly and selectively reduce Au3+ to Au0, and stabilize produced Au nanoparticles (AuNPs). The synergetic effect of electron transfer from ACDs to Au3+ and inner filter effect (IFE) from ACDs to AuNPs quenches the fluorescence within 30 s. Simultaneously, the resulting AuNPs have a purple color with a maximum absorption at 545 nm for visual detection. Therefore, for the first time, we reported a fluorometric and colorimetric dual-mode sensing system for real-time, highly sensitive and selective detection of Au3+. The fluorescence quenching ratio and absorbance change linearly with the increase of Au3+ concentration in the range of 0.3-8.0 µM and 3.3-60.0 µM with limits of detection (LODs) at 0.072 µM and 2.2 µM, respectively. The assay was applied for Au3+ determination in spiked real water samples with recoveries from 95.5 to 105.0%, and relative standard deviation (RSD) of less than 6.5%. Furthermore, ACDs with good photostability, low cytotoxicity, and excellent biocompatibility were successfully applied for intracellular Au3+ sensing and imaging. In addition, ACDs exhibited an extraordinarily high antioxidant activity, with an IC50 value for DPPH radical scavenging (0.70 µg mL-1) much lower than that of ascorbic acid (4.34 µg mL-1). The proposed strategy demonstrates the outstanding properties of ACDs in chemical and biomedical analysis. Graphical abstract.

Liquid Crystalline Hydrogel with Thermally Induced Reversible Shape Change and Water-Triggered Shape Memory.

Liquid crystalline hydrogel (LCH) is synthesized through simultaneous polymerization of hydrophobic and hydrophilic monomers in an oil-in-water emulsion, resulting in phase-separated liquid crystalline network (LCN) embedded in a hydrogel matrix. This material features some properties and functions of both LCN and hydrogel, displaying stable LC phase over repeated hydration and dehydration cycles of the hydrogel matrix. Using mechanically stretched and photocrosslinked LCH, the thermally induced LC-isotropic phase transition in LCN domains can be translated into reversible macroscopic deformation of the LCH. Moreover, the LCH exhibits water absorption-controlled shape memory effect.

Nasopharyngeal Epstein-Barr virus DNA loads in high-risk nasopharyngeal carcinoma families: Familial aggregation and host heritability.

Nasopharyngeal carcinoma (NPC), the most common head and neck cancer, is characterized by distinct geographic distribution and familial aggregation. Multiple risk factors, including host genetics, environmental factor, and EBV infection, have been linked to the development of NPC, particularly in the familial clustering cases. However, the cause of NPC endemicity remains enigmatic due possibly to the complicated interplay between these risk factors. Recently, positive Epstein-Barr virus (EBV) DNA loads at nasopharyngeal (NP) cavity has been found to reflect NPC development and applied in NPC screening. To examine whether the increased NP EBV loads could aggregate in the families and be affected by host genetics and environmental factor, EBV loads were obtained by 510 NP brushing samples from eligible unaffected individuals, who have two or more relatives affected with NPC, in 116 high-risk NPC families. The correlation of relative pairs was estimated using S.A.G.E. (version 6.4, 2016), and host heritability of NP EBV loads was calculated with variance component models using SOLAR (version 8.4.2, 2019). In result, significant correlations of EBV loads were observed between parent-offspring pairs and sibling-sibling pairs (P < .001), but not in distant kin relationship pairs. Interestingly, after excluding the shared environmental factor within families, host genetics contributes significantly to NP EBV loads with a heritability of 56.41% (P = 1.00 × 10-7 ), and its effect was slightly elevated (68.86%, P = 3.40 × 10-6 ) in families with more NPC cases (≥3). These findings indicate that additional host-genetic variants involved in the EBV local NP mucosal behavior may be especially important for the development of NPC.

Correction to: One-pot fabrication of dual-emission and single-emission biomass carbon dots for Cu2+ and tetracycline sensing and multicolor cellular imaging.

The authors would like to call the reader's attention to the fact that unfortunately the wrong file was published as Fig. 2.

One-pot fabrication of dual-emission and single-emission biomass carbon dots for Cu2+ and tetracycline sensing and multicolor cellular imaging.

Dual-emission and single-emission carbon dots (DCDs and SCDs) have been simultaneously synthesized by one-pot solvothermal treatment of leek. Different graphitization and surface functionalization were responsible for their distinction in fluorescence characteristics. DCDs with an average size of 5.6 nm exhibited two emissions at 489 and 676 nm under 420-nm excitation. Complexation between DCDs' surface porphyrins and Cu2+ led to quenching of the 676-nm emission, which resulted in the ratiometric determination of Cu2+ with a limit of detection (LOD) of 0.085 µM. SCDs, containing additional sulfur element (0.50%) with an average size of 7.7 nm, presented a single emission at 440 nm under 365-nm excitation. The static quenching and inner filter effects between SCDs and tetracyclines (TCs) made SCDs a fluorescence nanoprobe for TCs' determination with LODs of 0.26-0.48 µM. Applications of DCDs and SCDs for respective determination of Cu2+ and TCs in milk and pig liver samples were successfully demonstrated. Moreover, good photostability, low toxicity, and outstanding biocompatibility made DCDs and SCDs suitable for multicolor cellular imaging. Results indicate that natural products are excellent raw materials to controllably synthesize CDs with prominent physicochemical and fluorescence properties.Graphical abstract.

The Long Noncoding RNA ANRIL Promotes Cell Apoptosis in Lipopolysaccharide-Induced Acute Kidney Injury Mediated by the TLR4/Nuclear Factor-Kappa B Pathway.

BACKGROUND/AIMS: The purpose of this study is to analyze the expression and biological function of lncRNA ANRIL, microRNA-199a, TLR4, and nuclear factor-kappa B (NF-κB) in acute renal injury (AKI) induced by lipopolysaccharide (LPS). METHODS: The levels of ANRIL and microRNA-199a in mouse cells and kidneys were detected by quantitative-polymerase chain reaction. Western blot analysis was used for the NF-κB pathway protein. MTT assay was used for cell viability. Enzyme-linked immunosorbent assay was used for the secretion of inflammatory factors in mouse kidney tissue. Apoptosis was measured by flow cytometry and Western blotting. The potential binding region between ANRIL and miR-199a was verified by luciferase reporter assay. RESULTS: The upregulation of ANRIL can reduce the expression of microRNA-199a and increases the number of apoptotic cells. The expression levels of ANRIL in LPS-induced AKI mice and LPS-treated HK2 cells were upregulated compared with the control group. Overexpression of ANRIL increased apoptosis and promoted TLR4 (Toll-like receptor 4), NF-κB phosphorylation, and downstream transcription factor production. CONCLUSION: ANRIL/NF-κB pathway in LPS-induced apoptosis provided theoretical guidance for ANRIL in the treatment of AKI.

Determination of the activity of γ-glutamyl transpeptidase and of its inhibitors by using the inner filter effect on the fluorescence of nitrogen-doped carbon dots.

A fluorescence (FL) probe for determination of γ-glutamyl transpeptidase (GGT) activity and evaluation of inhibitors was developed based on the inner filter effect (IFE) of nitrogen-doped carbon dots (N-CDs). Bright green emissive N-CDs were synthesized by one-step hydrothermal technique with catechol and ethylenediamine. The excitation and emission wavelengths for N-CDs were 408 and 510 nm, respectively. γ-L-Glutamyl-4-nitroanilide (γ-G4NA) was employed as the substrate of GGT. The absorption spectrum of GGT catalytic product (4-nitroaniline, 4-NA) overlapped greatly with the excitation spectrum of N-CDs. 4-NA acted as the absorber in IFE to quench the FL of N-CDs. Thus, the FL quenching of N-CDs was closely related to GGT activity. The established FL method offered good linear relationship within 2.0-10.0 U L-1 (R2, 0.982) and 10.0-110.0 U L-1 (R2, 0.998) with a low detection limit of 0.6 U L-1. The method was successfully applied to investigate GGT activity in human serum samples with acceptable recoveries (99.1-105.0%). The approach was also employed for screening GGT inhibitors from different polar extracts of Schisandra chinensis. Results indicated that this strategy presents superior characteristics for GGT sensing. This method has great potential as a candidate for diagnosis of GGT-related diseases and high-throughput drug discovery. Graphical abstract.

Dual-emissive carbon dots for dual-channel ratiometric fluorometric determination of pH and mercury ion and intracellular imaging.

Dual-emissive carbon dots (CDs) were fabricated for dual-channel ratiometric fluorometric determination of pH and mercury ion (Hg2+) and intracellular imaging. Dual-emissive CDs were synthesized by one-pot solvothermal treatment of cabbage. The CDs exhibited two distinctive fluorescence emissions at 500 and 678 nm under single excitation at 410 nm. The green emission (500 nm) had reversible linear response to pH (7.0-12.0) due to deprotonation and protonation of surface functional groups and their non-covalent interactions. On the other hand, the red emission (678 nm) had efficient and selective fluorescence response to Hg2+ by formation of non-emission complex between CDs and Hg2+. The limit of detection (LOD) and limit of quantification (LOQ) for Hg2+ were 6.25 and 20.63 nM, respectively. The CDs have been successfully applied for label-free ratiometric fluorometric determination of pH and Hg2+ in fish and human serum samples with good recoveries (92.0-108.3%). In addition, the CDs had excellent photostability, low cytotoxicity, and good biocompatibility for intracellular imaging. All in all, the system was multi-functional in determination, high in sensitivity, and excellent in selectivity, which demonstrated wide and promising applicability for biosensing and bioimaging in the future. Graphical abstract Schematic presentation of dual-emission carbon dots (CDs) synthesized by solvothermal treatment of cabbage for dual-channel determination of pH and Hg2+.

A Novel Side-Chain Liquid Crystal Elastomer Exhibiting Anomalous Reversible Shape Change.

Liquid crystalline elastomers (LCEs) have been actively investigated as stimuli-controlled actuators and soft robots. The basis of these applications is the ability of LCEs to undergo a reversible shape change upon a liquid crystalline (LC)-isotropic phase transition. Herein, we report the synthesis of a novel LCE based on a side-chain liquid crystalline polymer (SCLCP). In contrast to known LCEs, this LCE exhibits a striking anomalous shape change. Subjecting a mechanically stretched monodomain strip to LC-disorder phase transition, both the length and width of the strip contract in isotropic phase, and both elongate in LC phase. This thermally induced behaviour is the result of a subtle interplay between the relaxation of polymer main chain oriented along the stretching direction and the disordering of side-group mesogens oriented perpendicularly to the stretching direction. This finding points out potential design of LCEs of this peculiar type and possible applications to exploit.

Online extraction and cleanup-quadrupole time-of-flight tandem mass spectrometry for rapid analysis of bioactive components in natural products.

The challenges in direct analysis of a complex system (e.g., natural product, food, biological samples) by mass spectrometry (MS) are the sophisticated sample preparation methods and ionization suppression by matrix interferences. Consequently, a novel online extraction and cleanup-quadrupole time-of-flight tandem mass spectrometry (OLEC-QTOF-MS/MS) system was developed for rapid, efficient, and sensitive analysis of flavonoids in Citri Reticulatae Pericarpium (CRP). For the OLEC strategy, a guard column packed with solid CRP (0.5 mg) and C18 gel was positioned on a manual injection valve, in which interferences with large polarities were online removed by methanol-0.1% formic acid (25:75, v/v) for 3 min, while target flavonoids were online extracted by methanol-0.1% formic acid (70:30, v/v) for 10 min for the subsequent QTOF-MS/MS analysis. The method was validated using official marker, hesperidin, by external standard method. Excellent linear ranges from 0.02 to 52.0 µg L-1 (R2, 0.9935) with a limit of detection (LOD) of 0.006 µg were obtained. Acceptable reproducibility (RSD 8.1 and 9.6% for intra- and inter-day variations) and recoveries (from 99.5 to 112.0%) were also attained. In addition, 20 flavonoids in CRP were identified according to their exact mass and fragmentation ions in MS/MS spectra, and five of them were reported for the first time. Obviously, OLEC-QTOF-MS/MS presented several advantages, such as simple operation and high sensitivity, which provided new perspectives for rapid analysis of bioactive components in complex natural products. Graphical Abstract ᅟ.

Cetyltrimethyl ammonium mediated enhancement of the red emission of carbon dots and an advanced method for fluorometric determination of iron(III).

Red-emissive carbon dots (CDs) were synthesized by one-step hydrothermal technique using citric acid (CA), and urea in N,N-dimethylformamide (DMF) solution. The CDs has an average diameter of 2.3 nm, excitation/emission maxima at 553/606 nm, and a low photoluminescence quantum yield (4%). Fluorescence is weakly quenched by the ions Fe3+, Hg2+, Cu2+, Co2+, Zn2+, Ca2+, Ni2+, and Pb2+. After addition of cetyltrimethyl ammonium ion (CTAB), electrostatic interaction between negatively charged CDs and CTAB causes the CDs to self-aggregate. The formation of CD/CTAB increases the average particle diameter to around 13 nm and enhances the quantum yield to 24%. The hydrophobic segments of CTAB twined into a network structure can selectively trap Fe3+ and then interact with surface groups of the CDs to cause quenching. The CD/CTAB nanoprobe enables fluorometric determination of Fe3+ with a linear response in the 0.10-10 µM concentration range and a 0.03 µM limit of detection. The probe was utilized for determination of Fe3+ in human serum samples, and satisfactory results were obtained. Graphical abstractSchematic representation of fluorometric analysis of Fe(III) ion by cetyltrimethyl ammonium ion (CTAB) mediated red emission carbon dots (CDs). The hydrophobic segments of CTAB twined into a network structure can selectively trap Fe(III) and then interact with surface groups of the CDs to cause quenching.

Selective Decrosslinking in Liquid Crystal Polymer Actuators for Optical Reconfiguration of Origami and Light-Fueled Locomotion.

The ability to optically reconfigure an existing actuator of a liquid crystal polymer network (LCN) so that it can display a new actuation behavior or function is highly desired in developing materials for soft robotics applications. Demonstrated here is a powerful approach relying on selective polymer chain decrosslinking in a LCN actuator with uniaxial LC alignment. Using an anthracene-containing LCN, spatially controlled optical decrosslinking can be realized through photocleavage of anthracene dimers under 254 nm UV light, which alters the distribution of actuation (crosslinked) and non-actuation (decrosslinked) domains and thus determines the actuation behavior upon order-disorder phase transitions. Based on this mechanism, a single actuator having a flat shape can be reconfigured in an on-demand manner to exhibit reversible shape transformation such as self-folding into origami three-dimensional structures. Moreover, using a dye-doped LCN actuator, a light-fueled microwalker can be optically reconfigured to adopt different locomotion behaviors, changing from moving in the laser scanning direction to moving in the opposite direction.