VASN promotes colorectal cancer progression by activating the YAP/TAZ and AKT signaling pathways via YAP.

Colorectal cancer (CRC) is one of the most common gastrointestinal malignancies. Vasorin (VASN) has been reported to be critical in tumor development and angiogenesis. However, VASN has not been reported in CRC, and its role is unclear. In this study, VASN expression is upregulated in CRC compared with the normal tissues, and VASN expression positively correlates with N stage and poor overall survival by analysis of different datasets and 32 CRC clinicopathologic samples. Overexpression of VASN significantly promotes CRC cell progression, including proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT), while knockdown of VASN inhibits CRC progression. We found that VASN was associated with the YAP/TAZ and PI3K/AKT pathways by gene set enrichment analysis (GSEA) and gene ontology (GO) analysis. Notably, western blotting, immunofluorescence staining and co-immunofluorescence (co-IP) confirmed that VASN could interact with YAP and activate the YAP/TAZ and PTEN/PI3K/AKT pathways, and knockdown of YAP reversed this effect. Importantly, our findings indicate that VASN interacts with YAP to inhibit YAP phosphorylation and stimulates CRC proliferation, migration, and invasion through activation of the YAP/TAZ-TEAD target gene CTGF and PTEN/PI3K/AKT pathways. Our results also show that knockdown of YAP reverses the cellular phenotype induced by increased VASN. In conclusion, our study reveals that VASN acts as an oncogene to stimulate tumor progression in CRC, providing new insights into the molecular mechanisms of CRC development and representing a possible novel biomarker for CRC.

Predicting response to CCRT for esophageal squamous carcinoma by a radiomics-clinical SHAP model.

BACKGROUND: Radical concurrent chemoradiotherapy (CCRT) is frequently used as the first-line treatment for patients with locally advanced esophageal cancer. Unfortunately, some patients respond poorly. To predict response to radical concurrent chemoradiotherapy in pre-treatment patients with esophageal squamous carcinoma (ESCC), and compare the predicting efficacies of radiomics features of primary tumor with or without regional lymph nodes, we developed a radiomics-clinical model based on the positioning CT images. Finally, SHapley Additive exPlanation (SHAP) was used to explain the models. METHODS: This retrospective study enrolled 105 patients with medically inoperable and/or unresectable ESCC who underwent radical concurrent chemoradiotherapy (CCRT) between October 2018 and May 2023. Patients were classified into responder and non-responder groups with RECIST standards. The 11 recently admitted patients were chosen as the validation set, previously admitted patients were randomly split into the training set (n = 70) and the testing set (n = 24). Primary tumor site (GTV), the primary tumor and the uninvolved lymph nodes at risk of microscopic disease (CTV) were identified as Regions of Interests (ROIs). 1762 radiomics features from GTV and CTV were respectively extracted and then filtered by statistical differential analysis and Least Absolute Shrinkage and Selection Operator (LASSO). The filtered radiomics features combined with 13 clinical features were further filtered with Mutual Information (MI) algorithm. Based on the filtered features, we developed five models (Clinical Model, GTV Model, GTV-Clinical Model, CTV Model, and CTV-Clinical Model) using the random forest algorithm and evaluated for their accuracy, precision, recall, F1-Score and AUC. Finally, SHAP algorithm was adopted for model interpretation to achieve transparency and utilizability. RESULTS: The GTV-Clinical model achieves an AUC of 0.82 with a 95% confidence interval (CI) of 0.76-0.99 on testing set and an AUC of 0.97 with a 95% confidence interval (CI) of 0.84-1.0 on validation set, which are significantly higher than those of other models in predicting ESCC response to CCRT. The SHAP force map provides an integrated view of the impact of each feature on individual patients, while the SHAP summary plots indicate that radiomics features have a greater influence on model prediction than clinical factors in our model. CONCLUSION: GTV-Clinical model based on texture features and the maximum diameter of lesion (MDL) may assist clinicians in pre-treatment predicting ESCC response to CCRT.

Overexpression of PD-L1 causes germ cells to slough from mouse seminiferous tubules via the PD-L1/PD-L1 interaction.

Spermatogenesis is a cyclical process in which different generations of spermatids undergo a series of developmental steps at a fixed time and finally produce spermatids. Here, we report that overexpression of PD-L1 (B7 homolog1) in the testis causes sperm developmental disorders and infertility in male mice, with severe malformation and sloughing during spermatid development, characterized by disorganized and collapsed seminiferous epithelium structure. PD-L1 needs to be simultaneously expressed on Sertoli cells and spermatogonia to cause spermatogenesis failure. After that, we excluded the influence of factors such as the PD-L1 receptor and humoral regulation, confirming that PD-L1 has an intrinsic function to interact with PD-L1. Studies have shown that PD-L1 not only serves as a ligand but also plays a receptor-like role in signal transduction. PD-L1 interacts with PD-L1 to affect the adhesive function of germ cells, causing malformation and spermatid sloughing. Taken together, these results indicate that PD-L1 can interact with PD-L1 to cause germ cell detachment and male infertility.

Secondary hypogonadism following hand, foot, and mouth disease in an adult: a case report and review of literature.

BACKGROUND: Previous reports have described hypogonadism associated with virus infection such as hantavirus, human immunodeficiency virus (HIV) or severe acute respiratory syndrome coronavirus 2 (SARS-COV-2). However, to our best knowledge there has been no case report of secondary hypogonadism following hand, foot, and mouth disease (HFMD). CASE PRESENTATION: A previously healthy 28-year-old man with no history of major physical and psychological trauma, presented with bilateral gynecomastia and erectile dysfunction 2 weeks after HFMD. Laboratory testament showed the level of gonadotropin hormones declined. Imaging examination demonstrated no major abnormal change in pituitary or reproductive system. The diagnosis of hypogonadism was established. Then the patient was ordered to maintain mental health outward of hospital without drug intervention. One month after presentation, his gonadotropin hormone level and sexual desire had recovered, while bilateral gynecomastia and erectile dysfunction symptoms disappeared. CONCLUSIONS: Physicians should notice the possibility for hypogonadism in adult patients with a recent history of HFMD.

PD-L1/PD-L1 signalling promotes colorectal cancer cell migration ability through RAS/MEK/ERK.

Programmed death ligand 1 (PD-L1) is widely known as an immune checkpoint, and immunotherapy through the inhibition of checkpoint molecules has become an important component in the successful treatment of tumours via programmed death 1 (PD-1)/PD-L1 signalling pathways. However, its biological functions and expression profile in colorectal cancer (CRC) are elusive. We previously found that PD-L1 can bind to PD-L1 and cause cell detachment. However, the detailed molecular mechanisms of how PD-L1 binds to PD-L1 and how it transmits signals to the cell remain unclear. In this study, we disclosed that PD-L1 expression was dramatically upregulated in CRC compared to normal tissues. Ectopic expression of PD-L1 inhibits cell adhesive capacity and promotes cell migration in CRC cell lines, while silencing PD-L1 had the opposite effects and suppressed invasion and proliferation. Mechanistically, PD-L1 was found to promote epithelial-mesenchymal transition (EMT) through the ERK signalling molecule pathway and interacted with the 1-86 aa fragment of KRAS to transduce signals. Collectively, our study demonstrated the role of PD-L1 after binding to PD-L1 in CRC, thereby providing a new theoretical basis for further improving immunotherapy with anti-PD-L1 antibodies.

The efficacy and safety of citrate mixture vs sodium bicarbonate on urine alkalization in Chinese primary gout patients with benzbromarone: a prospective, randomized controlled study.

OBJECTIVES: To compare the efficacy and safety of citrate mixture and sodium bicarbonate on urine alkalization in gout patients under benzbromarone treatment. METHODS: A prospective, randomized, parallel controlled trial was conducted among 200 gout patients in the dedicated gout clinic of the Affiliated Hospital of Qingdao University. The participants were randomly divided into two groups (1:1), sodium bicarbonate group (3 g/day) and citrate mixture group (7 g/day). All patients were prescribed with 25 mg/day benzbromarone at initiation and maintained at a dose of 50 mg/day. Clinical and biochemical data were collected at each follow-up time point (baseline, weeks 2, 4, 8 and 12). RESULTS: A total of 182 patients completed the 12-week urine alkalization study. The urine pH value of both groups increased significantly from the baseline to the final follow-up time point (sodium bicarbonate group, 5.50-6.00, P < 0.05; citrate mixture group, 5.53-5.93, P < 0.05). While the comparisons regarding urine pH between treatment groups showed no significant differences for each time point. The estimated glomerular filtration rate (eGFR) dropped significantly after 12 weeks' trial in the sodium bicarbonate group (P < 0.01), while it was comparable between baseline and the last follow-up (P > 0.05) in the citrate mixture group. Results of urine analysis showed that the incident rate of occult blood in the sodium bicarbonate group was higher than that in the citrate mixture group (38 vs 24%, P < 0.05), accompanied by a similar occurrence of kidney stones. After 12-week follow-up, the frequency of twice gout flare in the citrate mixture group was significantly lower than that in sodium bicarbonate group (4 vs 12%, P = 0.037). No treatment-emergent adverse events occurred. CONCLUSION: The efficacy of citrate mixture on urine alkalization is comparable to sodium bicarbonate under benzbromarone treatment without significant adverse events. Citrate mixture is superior to sodium bicarbonate in lowering the incidence of urine occult blood and the frequency of gout attacks. TRIAL REGISTRATION: Registered with ChiCTR (http://www.chictr.org.cn), No. ChiCTR1800018518.

S1P transporter SPNS2 regulates proper postnatal retinal morphogenesis.

Spinster homolog 2 (SPNS2) is the membrane transporter of sphingosine-1-phosphate (S1P), and it participates in several physiologic processes by activating different S1P receptors (S1PRs). However, its functions in the nervous system remain largely unclear. We explored the important role of SPNS2 in the process of retinal morphogenesis using a spns2-deficient rat model. In the absence of the functional SPNS2 transporter, we observed progressively aggravating laminar disorganization of the epithelium at the postnatal stage of retinal development. Disrupted cell polarity, delayed cell-cycle exit of retinal progenitor cells, and insufficient migration of newborn neurons were proposed in this study as potential mechanisms accounting for this structural disorder. In addition, we analyzed the expression profiles of spns2 and s1prs, and proposed that SPNS2 regulated retinal morphogenesis by establishing the S1P level in the eye and activating S1PR3 signaling. These data indicate that SPNS2 is indispensable for normal retinal morphogenesis and provide new insights on the role of S1P in the developing retina using an established in vivo model.-Fang, C., Bian, G., Ren, P., Xiang, J., Song, J., Yu, C., Zhang, Q., Liu, L., Chen, K., Liu, F., Zhang, K., Wu, C., Sun, R., Hu, D., Ju, G., Wang, J. S1P transporter SPNS2 regulates proper postnatal retinal morphogenesis.

Knockout of the urate oxidase gene provides a stable mouse model of hyperuricemia associated with metabolic disorders.

The urate oxidase (Uox) gene encodes uricase that in the rodent liver degrades uric acid into allantoin, forming an obstacle for establishing stable mouse models of hyperuricemia. The loss of uricase in humans during primate evolution causes their vulnerability to hyperuricemia. Thus, we generated a Uox-knockout mouse model on a pure C57BL/6J background using the transcription activator-like effector nuclease (TALEN) technique. These Uox-knockout mice spontaneously developed hyperuricemia (over 420 µmol/l) with about 40% survival up to 62 weeks. Renal dysfunction (elevated serum creatinine and blood urea nitrogen) and glomerular/tubular lesions were observed in these Uox-knockout mice. Male Uox-knockout mice developed glycol-metabolic disorders associated with compromised insulin secretion and elevated vulnerability to streptozotocin-induced diabetes, whereas female mice developed hypertension accompanied by aberrant lipo-metabolism. Urate-lowering drugs reduced serum uric acid and improved hyperuricemia-induced disorders. Thus, uricase knockout provides a suitable mouse model to investigate hyperuricemia and associated disorders mimicking the human condition, suggesting that hyperuricemia has a causal role in the development of metabolic disorders and hypertension.

Effects of autologous adipose-derived stem cell infusion on type 2 diabetic rats.

The effects and possible mechanisms of adipose-derived stem cells (ASC) infusion on type 2 diabetic rats were investigated in this study. Twenty normal male Sprague-Dawley rats were included in normal control group, and 40 male diabetic rats were randomly divided into diabetic control group and ASC group (which received ASC infusion). After therapy, levels of fasting plasma glucose (FPG), HbA1c, serum insulin and C-peptide, recovery of islet cells, inflammatory cytokines, and insulin sensitivity were analyzed. After ASC infusion, compared with diabetic control group, hyperglycemia in ASC group was ameliorated in 2 weeks and maintained for about 6 weeks, and plasma concentrations of insulin and C-peptide were significantly improved (P<0.01). Number of islet ß cells and concentration of vWF in islets in ASC group increased, while activity of caspase-3 in islets was reduced. Moreover, concentrations of TNF-α, IL-6 and IL-1ß in ASC group obviously decreased (P<0.05). The expression of GLUT4, INSR, and phosphorylation of insulin signaling molecules in insulin target tissues were effectively improved. ASC infusion could aid in T2DM through recovery of islet ß cells and improvement of insulin sensitivity. Autologous ASC infusion might be an effective method for T2DM.

The CC chemokine ligand 2 (CCL2) polymorphism -2518A/G is associated with gout in the Chinese Han male population.

Gout is usually characterized by uric acid-induced recurrent attacks of acute inflammatory arthritis. CC chemokine ligand 2 (CCL2), a chemokine involved in the recruitment and migration of monocytes/macrophages, has previously been shown to be increased in the plasma of gout patients. In this study, we examined whether the CCL2 -2518A/G (rs1024611) single nucleotide polymorphism (SNP) affects susceptibility to gout in a Chinese Han male population. Genomic DNA from gout patients (n = 1,109) and ethnically matched gout-free controls (n = 1,034) was genotyped for the CCL2 -2518A/G SNP using polymerase chain reaction-restriction fragment length polymorphism. The Chi-square test was performed to investigate the association of genotypic and allelic frequencies between cases and controls, and the -2518G allele was shown to be associated with a significantly increased risk of gout development [P = 0.007, odds ratio 1.182, 95% confidence interval 1.047-1.335]. The GG genotypic distribution was also significantly different between cases and controls (adjusted P = 0.021). However, genotypic distributions and allelic frequencies did not indicate significant associations (P = 0.150 and P = 0.050, respectively) between tophi and non-tophi patients. Our findings support a key role for the CCL2 SNP -2518A/G in association with gout susceptibility in the Chinese Han male population. However, additional studies in other populations should be carried out to confirm this finding.

Polymorphisms in the vitamin D receptor and risk of gout in Chinese Han male population.

Previous studies have showed that patients with gout showed lower serum 25(OH)D levels. As the specific receptor of vitamin D, VDR plays an important role in regulating immune system by combining with vitamin D. In this study, we investigated whether the functional VDR polymorphisms were associated with susceptibility to gout in Chinese Han male population. A total of 504 patients with gout and 523 gout-free controls were recruited from the Affiliated Hospital of the Medical College, Qingdao University. Genotyping of VDR rs11568820, rs2228570 and rs1544410 was performed by TaqMan allele discrimination assays. An association analysis was carried out using the χ(2) test. A genotype-phenotype analysis was also conducted. Our results showed that polymorphisms of rs11568820 and rs1544410 in VDR were associated with gout in Chinese Han male population. The A allele of both rs11568820 and rs1544410 was associated with the risk of gout [P = 0.012 OR 1.251, 95% CI (1.051-1.490); P = 0.006, OR 1.574, 95% CI (1.139-2.175)]. However, there was no statistic significance between rs2228570 and gout (P = 0.186). Our study suggested that the polymorphisms of VDR may be relevant host susceptibility factors for the development of gout in Chinese Han male population. However, further study should be done in a larger size sample and other ethic to test and verify our result.

Exhaustive Hydrodefluorination or Deuterodefluorination of Trifluoromethylarenes via Metal-Free Photoredox Catalysis.

Perfluoroalkyl compounds are persistent environmental pollutants due to their chemical and thermal stability. Hydrodefluorination is one of the most promising strategies for the disposal of fluorine-containing compounds, which has attracted much attention from a broad spectrum of scientific communities. Herein, we disclose a metal-free, visible-light-promoted protocol for the exhaustive hydrodefluorination of a wide variety of trifluoromethylarenes with up to 95% yields. Moreover, methyl-d3 groups can be obtained via deuterium water with a D ratio of up to 94%.

Response to febuxostat according to clinical subtypes of hyperuricemia: a prospective cohort study in primary gout.

BACKGROUND: While xanthine oxidase inhibitors target uric acid production, renal urate underexcretion is the predominant subtypes in gout. This study was to compare treatment response to the XOI febuxostat in a gout cohort according to clinical subtypes of hyperuricemia. METHODS: A prospective cohort study was conducted to compare the efficacy and safety of febuxostat (initially 20 mg daily, escalating to 40 mg daily if not at target) in 644 gout patients with the three major clinical subtypes for 12 weeks. Hyperuricemia was defined as the renal overload subtype, the renal underexcretion subtype, or the combined subtype based on UUE > or ≤ 600 mg/d/1.73 m2 and FEUA < or ≥ 5.5%. The primary endpoint was the rate of achieving serum urate (SU) < 6 mg/dL at week 12. RESULTS: Fewer participants with combined subtype achieved the SU target, 45.5% compared with 64.8% with overload subtype (P = 0.007), and 56.6% with underexcretion subtype (P = 0.022). More participants with combined subtype (82%) had febuxostat escalated to 40 mg than those with overload (62%, P = 0.001) or underexcretion subtype (68%, P = 0.001). In all participants, combined subtype hyperuricemia (OR = 0.64, 95%CI 0.41-0.99, P = 0.048) and baseline SU (OR = 0.74, 95%CI 0.62-0.89, P = 0.001) were independently associated with lower rates of achieving SU target. CONCLUSIONS: People with combined subtype have a lower response to febuxostat, compared to those with either overload or underexcretion subtype. Assessment of hyperuricemia subtype may provide useful clinical data in predicting febuxostat response.

Advances in measuring DNA methylation.

DNA methylation is one of the most important components of epigenetics, which plays essential roles in maintaining genome stability and regulating gene expression. In recent years, DNA methylation measuring methods have been continuously optimized. Combined with next generation sequencing technologies, these approaches have enabled the detection of genome-wide cytosine methylation at single-base resolution. In this paper, we review the development of 5-methylcytosine and its oxidized derivatives measuring methods, and recent advancement of single-cell epigenome sequencing technologies, offering more referable information for the selection and optimization of DNA methylation sequencing technologies and related research.

Single-cell analysis of transcription factor regulatory networks reveals molecular basis for subtype-specific dysregulation in acute myeloid leukemia.

Highly heterogeneous acute myeloid leukemia (AML) exhibits dysregulated transcriptional programs. Transcription factor (TF) regulatory networks underlying AML subtypes have not been elucidated at single-cell resolution. Here, we comprehensively mapped malignancy-related TFs activated in different AML subtypes by analyzing single-cell RNA sequencing data from AMLs and healthy donors. We first identified six modules of regulatory networks which were prevalently dysregulated in all AML patients. AML subtypes featured with different malignant cellular composition possessed subtype-specific regulatory TFs associated with differentiation suppression or immune modulation. At last, we validated that ERF was crucial for the development of hematopoietic stem/progenitor cells by performing loss- and gain-of-function experiments in zebrafish embryos. Collectively, our work thoroughly documents an abnormal spectrum of transcriptional regulatory networks in AML and reveals subtype-specific dysregulation basis, which provides a prospective view to AML pathogenesis and potential targets for both diagnosis and therapy.

Association of obesity, triglyceride-glucose and its derivatives index with risk of hyperuricemia among college students in Qingdao, China.

Objective: To analyze and compare the associations of hyperuricemia (HUA) with obesity, triglyceride-glucose (TyG), and its derivatives in college students. To provide early guidance on risk predictors of HUA in college students. Methods: This study was a cross-sectional survey including 23,411 participants (age: 17-20 years). Investigators conducted face-to-face interview surveys and physical examinations. Automated biochemical methods were used to detect biochemical indicators such as serum uric acid (UA). Calculation of obesity, TyG, and their derivatives indices were performed. Logistic regression was used to analyze the relationship between different indexes and hyperuricemia. OR value and 95% CI were also calculated. ROC curve was used for assessing the predictive ability of different indices of hyperuricemia. Results: After adjusting for age, SBP, DBP, ALT, AST, TC, BUN, and CREA, multivariate logistic regression showed that the OR value of LAP in the obesity index was higher, especially in women (male OR: 4.347, 95%CI: 3.807, 4.964; female OR: 4.672, 95%CI: 3.800, 5.744). The other three quartiles of TyG derivatives were highly associated with hyperuricemia in men and women compared with the top quartile (all P< 0.05). The risk of hyperuricemia increased with an increase in quartiles. For college students, all indicators could distinguish the presence of hyperuricemia. For men, the area under the curve (AUC) of TyG-WC was the largest (AUC: 0.694; 95%CI: 0.684-0.704; P<0.05), according to the Maximum Youden index 0.290 with cut point value 477.853. In women, TyG-BMI showed a maximum AUC value of 0.702 (95%CI: 0.685-0.719; P<0.05), according to the maximum Youden index of 0.317 with cut point value 132.446. The TyG-WC, TyG-WHtR, TyG-LAP, and LAP indices also had relatively high AUC. Conclusion: In clinical practice, LAP, TYG, and their related derivatives may be used as sensitive indicators for HUA prediction in college students.

Increased expression of CYP17 and CYP11B1 in subclinical Cushing's syndrome due to adrenal adenomas.

OBJECTIVES: To determine whether steroidogenic enzyme expression is associated with the steroid secretory pattern of subclinical Cushing's syndrome (SCS) by investigating the mRNA and protein expression of CYP17 and CYP11B1 in SCS adenomas, normal adrenal cortices (NA), non-functional adrenal adenomas (NFA) and cortisol-producing adenomas (CPA). METHODS: Total RNA and protein were extracted from 20 CPA, six SCS, 15 NFA, and eight NA. Real-time quantitative polymerase chain reaction (PCR) and western blotting analysis were performed to determine the mRNA and protein expression of CYP17 and CYP11B1 in different tissues. The expression of CYP17 and CYP11B1 in the adrenocortical tumors was compared expression in NA. RESULTS: Expression of both CYP11B1 and CYP17 mRNA and protein was detected in all samples tested. The expression of CYP11B1 mRNA and protein was significantly higher in the CPA group than in the other groups and was slightly higher in SCS samples compared with NA and NFA samples (all P < 0.05). There was no significant difference in CYP11B1 mRNA and protein expression between NA and NFA samples (P > 0.05). The expression of CYP17 mRNA and protein in different tissues was similar to that of CYP11B1. Neither CYP11B1 nor CYP17 mRNA and protein expression was correlated with plasma cortisol or adrenocorticotrophin levels (all P > 0.05). CONCLUSIONS: In conclusion, CYP11B1 and CYP17 are overexpressed in subclinical CPA and their overexpression accounts for the increased production of cortisol that is characteristic of CPA.

Regioselective Radical Borylation of α,ß-Unsaturated Esters and Related Compounds by Visible Light Irradiation with an Organic Photocatalyst.

Radical hydroboration reactions have only recently been reported and are still rare. Here we describe a photoredox radical hydroboration of α,ß-unsaturated esters, amides, ketones, and nitriles with NHC-boranes that uses only an organocatalyst and visible light. The conditions are mild, the substrate scope is broad, and the α/ß regioselectivity is high. The reaction requires only the organocatalyst; there is no costly metal, and there are no other additives (base, cocatalyst, initiator).

Prognostic Value of CD9 in Solid Tumor: A Systematic Review and Meta-Analysis.

Numerous clinical studies investigated how low expression of CD9 predicts poor prognosis of solid tumor. However, the results were inconclusive. This present meta-analysis was therefore performed to determine the prognostic value of CD9 expression in solid tumors. In this meta-analysis, 25 studies involving 5,555 participants were included; the result showed strong significant associations between declined expression of CD9 and all endpoints: overall survival (OS) (hazard ratio (HR) = 1.88, 95% CI = 1.45-2.43, p < 0.000) and time to progression (TTP) (HR = 2.0, 95% CI = 1.38-2.88, p < 0.000). The subgroup analysis was also performed, which revealed that the associations between CD9 downregulated expression related to poor OS in lung cancer and head and neck cancer. Also, low expression of CD9 was significantly connected with poor TTP in patients with head and neck cancer. The adverse prognostic impact of decreased expression of CD9 was observed in patients of different ethnicities. In conclusion, these results showed that declined expression of CD9 was associated with poor survival in human solid tumors. CD9 may be a valuable prognostic predictive biomarker and a potential therapeutic target in human solid tumors.

Geometry transformation of ionic surfactants and adsorption behavior on water/n-decane-interface: calculation by molecular dynamics simulation and DFT study.

Understanding the effect of surfactant structure on their ability to modify interfacial properties is of great scientific and industrial interest. In this work, we have synthesized four amide based ionic surfactants under acidic or basic conditions, including CTHA·HCl, CTEA·HCl, CTHA-Na+ and CTEA-Na+. Experiments have proved that the anionic surfactant with polyethylene oxide groups (CTEA-Na+) had the lowest surface tension on the water/n-decane interface. Molecular dynamics simulations have been applied to investigate the structural effect on the adsorption behavior of four different surfactants. The surface tension, interface thickness, interface formation energy, density profiles, order parameters, radial distribution function on the water/n-decane interfaces were calculated and compared. During the equilibrium states, we found that the interface configuration of two cationic surfactants are almost linear while the two anionic surfactants are changed to bending shapes due to the different positions of the hydrophilic head groups. Further DFT study and wavefunction analysis of surfactants have shown that CTEA-Na+ can form stronger vdW interactions with n-decane molecules due to a more neutral electrostatic potential distribution. Meanwhile, the introduction of polyethylene oxide groups has offered more H-bonding sites and resulted in more concentrated H-bonding interactions with water molecules. The difference of weak interactions may contribute to the conformational change and finally affect the interface properties of these ionic surfactants.