Transport and fate of Cu and Cd in contaminated paddy soil under acid mine drainage.

Long-term heavy metals accumulation caused by acid mine drainage (AMD) irrigation in paddy soils poses a severe threat to environmental health. However, the soil adsorption mechanisms under AMD flooding remain unclear. This study provides key insights into the fate of heavy metals in soil, particularly the retention and mobility mechanisms of Cu (copper) and Cd (cadmium) after AMD flooding. The migration and fate of Cu and Cd in uncontaminated paddy soils treated by AMD in Dabaoshan Mining area was investigated via column leaching experiments in the laboratory. The maximum adsorption capacities of Cu (658.04 mg kg-1) and Cd (335.20 mg kg-1) cations were predicted and the breakthrough curves were fitted using the Thomas and Yoon-Nelson models. Our findings demonstrated that Cd was more mobile than Cu. Furthermore, the soil had a greater adsorption capacity for Cu than Cd. Tessier's five-step extraction method was used to determine Cu and Cd fractions in leached soils at different depths and times. After AMD leaching, the relative and absolute concentrations of the easily mobile forms were all increased at different soil depths, thus increasing the potential risk to the groundwater system. Mineralogical characterization of the soil indicated that AMD flooding leads to the formation of mackinawite. This study provides insights into the distribution and transportation processes of soil Cu and Cd and their ecological effects under AMD flooding, as well as a theoretical basis for the establishment of corresponding geochemical evolution models and environmental governance in mining areas.

Prevalence of and Associated Factors for Overactive Bladder Subtypes in Middle-Aged Women: A Cross-Sectional Study.

Background and Objectives: The living environment can manifest physiological responses in humans, with cohabiting couples often having similar health statuses. The aim of this study was to (1) examine the prevalence of the overactive bladder (OAB) with or without incontinence and (2) identify associated factors for OAB with and without incontinence (including environmental factors, such as living with a partner who has OAB) in middle-aged women. Materials and Methods: In this cross-sectional study, the International Consultation on Incontinence Questionnaire Overactive Bladder (ICIQ-OBA) was administered to 970 couples. Data were analyzed using descriptive statistics, chi-square analyses, and multivariate logistic regression. Results: Responses to the ICIQ-OBA among middle-aged women generated a higher prevalence of OAB with incontinence (OABwet; 41%) than OAB without incontinence (OABdry; 26%; p < 0.001). The factors associated with OABwet were as follows: being age ≥ 55 years (odds ratio [OR], 1.41; 95% confidence interval [CI], 1.02−1.95), having a body mass index (BMI) ≥ 27 kg/m2 (OR, 1.50; 95% CI, 1.03−2.17), having vaginitis (OR, 1.89; 95% CI, 1.28−2.80), and having partners with OABwet (OR, 2.35; 95% CI, 1.74−3.19). Having partners with OABdry (OR, 1.81; 95% CI, 1.34−2.44) was an associated factor for OABdry. Conclusions: This study identified the associated factors for OAB subtypes (OABwet and OABdry) in middle-aged women. These findings can support treatment and preventive strategies for health providers who care for patients with OAB. As part of the treatment and preventative strategies, the risk that partners may introduce to the development of OAB in women should also be considered.

Overactive Bladder during Pregnancy: A Prospective Longitudinal Study.

Background and Objectives: Overactive bladder (OAB) is a serious urination-related symptom of unknown pathogenesis that affects one's everyday activities. The objective of this study was to examine how OAB prevalence, symptom severity, and degree of distress caused by OAB symptoms evolved throughout the course of pregnancy. Materials and Methods: A total of 659 pregnant women were recruited from 2015 to 2020, and were evaluated through the International Consultation on Incontinence Questionnaire-Overactive Bladder (ICIQ-OAB) on OAB symptoms, administered in the early, middle, and late stages of pregnancy. Results: Generalized estimating equation analysis revealed that the odds of OAB occurring in the middle and late stages of pregnancy were 1.90 and 2.33 times higher, respectively, than in early pregnancy. The corresponding odds for OAB-wet were 1.63 and 2.07 higher, respectively, and the odds of OAB-dry occurring during late pregnancy were 0.80 higher than during early pregnancy. Symptoms were more severe by 0.07 and 0.21 points (on a 4-point scale) in the middle and late stages of pregnancy, respectively, than in early pregnancy; distress was greater by 0.13 and 0.27 points (on a 10-point scale) in the middle and late stages of pregnancy, respectively, than in early pregnancy. The prevalence of OAB, OAB-dry, and OAB-wet was significantly higher in early pregnancy than pre-pregnancy. Conclusions: The prevalence of OAB and OAB-wet increased over the course of pregnancy, but the prevalence of OAB-dry decreased. Furthermore, symptom severity and degree of distress increased over time.

Sulfate migration and transformation characteristics in paddy soil profile affected by acid mine drainage.

SO42-, a major component of acid mine drainage (AMD), plays an important role in study environment of AMD. We investigated the distribution and adsorption-desorption mechanisms of SO42- and the variation of stable isotope of sulfur (δ34S) values in the soil profile polluted by AMD. Results showed that the species and 34S values of SO42- differed significantly among different soil depths. In the surface soil (0-20 cm), native water-soluble SO42- (WSS) in the range ~85 % total SO42- was the dominant species. There was a peak of adsorption, which correlated significantly with amorphous oxide Fe, indicating that iron oxides and pH was fundamentally proportional to SO42- forms. The high concentrations of Cu2+ and Pb2+ also played important roles in form of SO42- in soil profile. Desorption kinetics of explained three SO42--bound forms. The trend mean δ34S values of WSS and AS in soil vertical profile was very similar with increasing from surface to subsurface, and have lower δ34S values than those of total sulfur, indicating that mineralization of organic sulfur should produce SO42- that was more depleted in δ34S. SO42- desorbed and trend δ34S values could provide reasonable explanation for the migration of SO42-. In the AMD irrigation scope, the higher SO42- concentration was reserved by immobilized as organic sulfur, and then main approach of SO42- migration was desorption and organic sulfur mineralize in now stage.

Acidity and metallic elements release from AMD-affected river sediments: Effect of AMD standstill and dilution.

In acid mine drainage (AMD) polluted rivers, considerable fraction of potential toxic elements are temporarily sequestered by sediments. There are two main potential environmental hazards associated with the sediments, acidity liberation and re-mobilization of metallic elements, during environmental conditions change. The effects of AMD standstill and water dilution on metallic elements migration were assessed in an AMD standstill test and a dialysis experiment. Maintaining AMD standstill, often occurring in AMD damming process, could induce the occurrence of iron secondary minerals precipitation along with attenuation of dissolved elements and a decrease in water pH value. Both field sediments and lab precipitates were confirmed as being dominant with schwertmannite which was the most important source and sink for acidity and metallic elements. The mechanism of cation heavy metals scavenging implied by FTIR results mostly depended on the exchanging of H+ from surface hydroxyl groups (-OH) in schwertmannite-rich sediments. For arsenic oxyanion, its adsorption included surface complexation with iron hydroxyl groups at the mineral surface, as well as anion exchange of SO42- present in the structure. The quantities of acidity release differed significantly from 20 to 3714 mol H+/t depending on the iron hydroxyl minerals type and their contents in the corresponding sediments in 35 d dialysis, with the release rate well fitted by the second order model. Slight degree of phase transformation in schwertmannite dominant sediment had resulted in a high risk of metallic element release during the 35 d dilution duration. The significant risk of metallic elements release was ranked in the order of Cd > Mn > Zn > Pb, and with more than 89% of Cd released from FS6 and 82% from LPS1. Relatively, Cu and As in sediments were much more stable. Overall, damming was an effective and low cost pretreatment strategy for AMD pollution control. Knowledge of the characteristics of iron secondary minerals in river sediments is essential premise for both comprehensive assessment of site contamination status and effective remediation strategy decision.

Migration and fate of metallic elements in a waste mud impoundment and affected river downstream: A case study in Dabaoshan Mine, South China.

Fate of metallic elements and their migration mechanisms in a waste mud impoundment and affected downstream were assessed. Physicochemical and mineralogical methods combined with PHREEQC calculation, statistical analysis and review of relevant literatures were employed. Results showed that the waste in mud impoundment had been severely weathered and acidized. Metallic elements exhibited high mobility and activity, with a mobility ranking order of Cd > Zn > Mn > Cu ≈ Cr > As ≈ Pb. Hydraulic transportation originating from elevation variation was the most important driving force for metallic elements migration. Although damming standstill was considered as an effective strategy for controlling coarse suspended particulate pollutants, metallic elements were still transported to the Hengshi River in both dissolved phase and fine suspended particle phase accompanied by the overflow of acid mine drainage. The concentrations of dissolved metallic elements were attenuated significantly along the Hengshi River within 41 km stretch. Precipitation/ co-precipitation of iron oxyhydroxides, especially schwertmannite, ferrihydrite and goethite minerals, were established as the most critical processes for metallic elements attenuation in river water. Accompanied by metals migration in the river, two pollution sensitive sites with notably high content of metals in the stretch of S6-S8 and S10, were identified in gently sloping river stretch.

Hepatoprotective effects of Methyl ferulic acid on alcohol-induced liver oxidative injury in mice by inhibiting the NOX4/ROS-MAPK pathway.

AIMS: The present study aimed to investigate the hepatoprotective effects of Methyl ferulic acid (MFA) against oxidative stress and apoptosis as well as inflammation in mice with liver injury induced by alcohol and its underlying mechanisms. METHODS: C57BL/6 mice were divided into a control group,a model group, and Methyl ferulic acid with high dosage (20 mg/kg), moderate dosage (10 mg/kg) and low dosage (5 mg/kg) groups. The general condition and organ index of each group were investigated. Histopathological analysis was performed to determine the degree of hepatic injury. Biochemical analyses of functional liver enzymes, lipid peroxidation enzymes and lipid content in each group. The levels of inflammatory cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The mechanisms were investigated by detecting levels of NADPH Oxidase 4 (NOX4),p22phox, cytochrome P4502E1 (CYP2E1),Bax,B-cell lymphoma 2 (Bcl-2),cleaved-caspase 3 and 9 and phosphorylated extracellular regulated protein kinases(ERK),phosphorylated c-Jun N-terminal kinase (JNK), and phosphorylated p38 mitogen-activated protein kinase (MAPK) using real-time polymerase chain reaction (PCR) and Western blotting. RESULTS: MFA treatment significantly decreased serum enzymatic activities of alanine aminotransferase (ALT) and aspartate aminotransaminase (AST). MFA markedly increased levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GSH-Px) and total antioxidative capacity (T-AOC), and reduced the concentration of malondialdehyde (MDA) and reactive oxygen species (ROS). Histopathological examination of livers showed that MFA reduced cytoplasmic vacuolisation necrosis and inflammatory cell infiltration in alcohol-treated mice. MFA treatment remarkably reduced the levels of trigyceride (TG), total cholesterol (TC) and low-density lipoprotein (LDL), decreasing the levels of high-density lipoprotein (HDL), alcohol dehydrogenase(ADL) and aldehyde dehydrogenase (ALDH). MFA treatment remarkably inhibited the expression of inflammatory factors tumour necrosis factor (TNF)-α, monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-1ß and IL-6. MFA attenuated both mRNA and protein expression of NOX4,p22phox,CYP2E1,Bax/Bcl-2. In addition, MFA inhibited the activation of caspase 3 and 9 and downregulated the levels of p-JNK,p-p38 MAPK and p-ERK in liver. CONCLUSION: MFA has a protective effect on alcohol-induced liver injury, which may be related to its antioxidant,anti-inflammatory,lipid-eliminating properties and its ability to regulate the NOX4/ROS-MAPK signalling pathway.

Role of Dissolved Organic Matter in the Release of Chromium from Schwertmannite: Kinetics, Repartition, and Mechanisms.

Dissolved organic matter (DOM) is an important factor influencing mineral biogeochemistry, although the role of labile DOM in the release of chromium (Cr) from schwertmannite, a mineral with high surface area, is unclear. In this study, the interaction of DOM with synthetic CrO-schwertmannite was investigated to better understand the potential fate of Cr in high-DOM environments. Minerals and their products were analyzed using Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Experiments were conducted at pH 3.2 or 6.5 for different lengths of time, with a shrinking core model developed to describe kinetic processes. The concentration of total Cr in solution reached a maximum when the pH was 6.5 and the concentration of L-tryptophan was 5 mM. The newly formed minerals were confirmed to be mixtures involving residual schwertmannite, goethite, ferrihydrite, and jarosite. A possible mechanism is proposed to be a ligand-controlled binary system, accompanied by possible reduction at acidic pH conditions (3.2), including mass transfer and charge transfer processes. This study gives a new perspective for understanding the reactivity and stability of schwertmannite in the environment; it also provides some predictions on the mobility and fate of Cr. These findings will help design remediation strategies for Cr contamination.

Sex life and role identity in Taiwanese women during menopause: a qualitative study.

AIM: Our goal was to examine Taiwanese women's perspectives on the way menopause affected their sexual behaviour to gain an in-depth understanding of their experiences during this transition. BACKGROUND: Physical symptoms associated with menopause may affect women's sexual experiences. Little is known about how menopause-related changes in sexual behaviour may affect role identity of women living in a modernizing urban culture that is still strongly rooted in traditional beliefs and attitudes. DESIGN: This was a qualitative study involving face-to-face interviews using open-ended questions. METHODS: During 2011-2012, eighteen peri or postmenopausal women visiting a medical clinic for gynaecological examinations or treatment were interviewed about their sexual experiences. Responses were analysed for common themes. FINDINGS: Four themes were identified about the effects of menopause on women's sex life: (1) changes in physical responses during sex; (2) the acceptance/non-acceptance of the current situation; (3) sexual pressure related to their marital role; (4) efforts to improve sexual interest or activity. Menopause-related physical changes often (but not always) made sexual interactions difficult. But women's responses to the changes varied. Some used sexual discomfort as a reason to avoid sexual intercourse. Others sought to improve their sexual encounters through behavioural modifications or hormone therapy. CONCLUSIONS: Given the variety of reactions to the impact of menopause on sexual behaviour/relationships seen here, it is clear that health professionals need to assess of each woman's specific situation and be prepared to recommend a variety of behavioural or hormonal treatment options.

Concealing emotions: nurses' experiences with induced abortion care.

AIMS AND OBJECTIVES: To explore the experiences of nurses involved with induced abortion care in the delivery room in Taiwan. BACKGROUND: Induced abortion has emotional, ethical and legal facets. In Taiwan, several studies have addressed the ethical issues, abortion methods and women's experiences with abortion care. Although abortion rates have increased, there has been insufficient attention on the views and experiences of nurses working in the delivery room who are involved with induced abortion care. DESIGN: Qualitative, semistructured interviews. METHODS: This study used a purposive sampling method. In total, 22 nurses involved with induced abortion care were selected. Semistructured interviews with guidelines were conducted, and the content analysis method was used to analyse the data. RESULTS: Our study identified one main theme and five associated subthemes: concealing emotions, which included the inability to refuse, contradictory emotions, mental unease, respect for life and self-protection. CONCLUSION: This is the first specific qualitative study performed in Taiwan to explore nurses' experiences, and this study also sought to address the concealing of emotions by nurses when they perform induced abortion care, which causes moral distress and creates ethical dilemmas. The findings of this study showed that social-cultural beliefs profoundly influence nurses' values and that the rights of nurses are neglected. RELEVANCE TO CLINICAL PRACTICE: The profession should promote small-group and case-study discussions, the clarification of values and reflective thinking among nurses. Continued professional education that provides stress relief will allow nurses to develop self-healing and self-care behaviours, which will enable them to overcome the fear of death while strengthening pregnancy termination counselling, leading to better quality professional care.

Primary ovarian leiomyoma with calcification: A case report.

RATIONALE: Primary ovarian leiomyoma is a rare benign tumor. The exact histological origin and pathogenesis of primary ovarian leiomyoma are still unclear, while its preoperative imaging diagnosis is often challenging and prone to misdiagnosis. The study aims to elucidate the diagnosis of primary ovarian leiomyoma and to distinguish it from fibroma. PATIENT CONCERNS: A 34-year-old female was admitted to the hospital with complaints of pelvic mass found for one year. One years ago, the patient went to a local hospital for examination due to irregular menstruation. DIAGNOSES: The ultrasound report of the patient showed ovarian teratoma. The postoperative pathological results showed ovarian leiomyoma and calcification. INTERVENTIONS: The patient underwent laparoscopic right ovarian leiomyoma resection. OUTCOMES: The patient was discharged home three days after surgery. At the most recent follow-up (five months after operation) of the patients, ultrasound was performed and no abnormal echoes were suggested in the adnexal region. LESSONS: In the diagnosis of primary ovarian leiomyoma, our case emphasizes the importance of microscopic features as an effective approach to distinguish it from ovarian fibroma, leiomyosarcoma, and stromal tumors. Additionally, personalized treatment should be considered based on the patient age and fertility needs.

Exploring clinical judgment ability in second-degree baccalaureate of science nursing students: A mixed methods study.

BACKGROUND: As they have not yet embarked on clinical practice, most students who already have a bachelor's degree but require a bachelor's degree in nursing occasionally perceive the educator's instruction on clinical situations as abstract and challenging for making accurate clinical judgments. OBJECTIVES: This study aims to implement a clinical judgment model and case scenarios in classroom teaching to evaluate improvements in students' clinical judgment and critical thinking abilities. DESIGN: A mixed-method design. SETTING: A second-degree Bachelor of Science in Nursing at a university in Taiwan. PARTICIPANTS: First-year undergraduate nursing students. METHODS: This mixed-methods study featured a survey at the beginning and end of a course, followed by one-on-one online interviews. A purposive sample of sophomore nursing students was recruited from a university in northern Taiwan between March 2020 and May 2021. Semi-structured interviews were conducted after a preliminary analysis of the collected quantitative data. RESULTS: In total, 48 participants completed the study questionnaire, and 20 were interviewed. The results show that the students' ability to make clinical judgment and identify individual health problems from case scenarios significantly improved after completing the course. However, critical thinking did not differ significantly after the course. Qualitative data analysis revealed three key themes relevant to the participants' learning experiences: (1) establishing the context of clinical judgment, (2) building a bridge between basic medical science and clinical nursing, and (3) having a broader perspective. CONCLUSIONS: Incorporating clinical judgment measurement model and case scenarios in the curriculum may benefit second-degree Bachelor of Science in Nursing students who have not yet begun their clinical practice. Additionally, the result provides educators with valuable learning goals and evaluation strategies in the classroom and clinical practice.

Application of apatite particles for remediation of contaminated soil and groundwater: A review and perspectives.

With rapid industrial development and population growth, the pollution of soil and groundwater has become a critical concern all over the world. Yet, remediation of contaminated soil and water remains a major challenge. In recent years, apatite has gained a surging interest in environmental remediation because of its high treatment efficiency, low cost, and environmental benignity. This review summarizes recent advances in: (1) natural apatite of phosphate ores and biological source; (2) synthesis of engineered apatite particles (including stabilized or surface-modified apatite nanoparticles); (3) treatment effectiveness of apatite towards various environmental pollutants in soil and groundwater, including heavy metals (e.g., Pb, Zn, Cu, Cd, and Ni), inorganic anions (e.g., As oxyanions and F-), radionuclides (e.g., thorium (Th), strontium (Sr), and uranium (U)), and organic pollutants (e.g., antibiotics, dyes, and pesticides); and (4) the removal and/or interaction mechanisms of apatite towards the different contaminants. Lastly, the knowledge or technology gaps are identified and future research needs are proposed.

Experiences of Family Caregivers Providing Home Care to Older Patients With Cancer: A Qualitative Study.

BACKGROUND: Older patients with cancer receive anticancer therapy in outpatient settings, and care-related issues may occur after discharge, which often requires family caregivers (FCs) to play a significant role in providing cancer care at home. However, relatively few studies have been focused on exploring the care experiences of these FCs. PURPOSE: The aim of this study was to explore the care experiences of FCs caring for older family members with cancer at home. METHODS: A qualitative study design and in-depth individual interviews were used to explore the at-home care experiences of FCs of older patients with cancer. The research was conducted in chemotherapy outpatient settings of a medical center in northern Taiwan. Content analysis was used to analyze data. The analyses focused on first extracting meaningful units from the text and then inducting categories from these units and determining the major themes. RESULTS: Twenty FCs were interviewed. The three themes identified included (a) increased information needs and challenges in diet preparation and treatment decision making, (b) personal and patient-induced emotional stress, and (c) life rebalancing through the care experience. CONCLUSIONS/IMPLICATIONS FOR PRACTICE: The findings highlight the educational requirements, especially related to meeting personal dietary needs and obtaining psychological support, for FCs caring for older patients with cancer to help them rebalance their life.

Photo-transformation of microplastics and its toxicity to Caco-2 cells.

In recent years, microplastics (MPs) pollution, as a global environmental problem, has been widely concerned by countries all over the world. However, the research on the impact of MPs on human health is still limited. In this study, we studied the photo-transformation behavior of polystyrene microplastics (PS-MPs) under ultraviolet light and its toxicity to Caco-2 cells. Our results showed that the surface of PS-MPs was roughened by light, and cracks and pits appeared. UV-vis spectra showed that the opening of phenyl ring and the formation of carbonyl group might exist in this process. Based on FTIR and 2D-COS analysis, we observed the formation of carbonyl group and hydroxyl group, and preliminarily determined that the order of photo-transformation of PS-MPs was 698 (CH) > 752 (CH) > 1030 (CO) > 3645 (OH/OOH) > 1740 (CO). XPS showed that the photo-transformation of PS-MPs was a process in which carbon-containing functional groups were gradually partially transformed into oxygen-containing functional groups. Finally, the toxicity results showed that with the increase of PS-MPs concentration and the extension of light irradiation time, the survival rate of Caco-2 cells gradually decreased and the integrity of cell membrane was destroyed. The increased cytotoxicity can be explained at least in part by the fact that the toxicity of oxygen-containing functional groups is greater than that of carbon-containing functional groups, but how these functional groups affect the cytotoxicity of cells still needs sustained research in the future. This study can provide new insights for understanding the environmental behavior and ecological effects of PS-MPs in the environment.

Abundance and characteristics of microplastics in the surface water and sediment of parks in Xi'an city, Northwest China.

Microplastics (MPs), as a new type of pollutants, have attracted wide attention especially in recent years, but there was insufficient research on the distribution and characteristics of MPs in urban park water body. In this study, the pollution of MPs in water and sediment of Xi'an, the largest city in northwest China, was investigated. The MPs concentration in the surface water and sediment was 2900-6970 items/m3 and 940-3560 items/kg, respectively. According to the urban functions, the parks were divided into residential areas, commercial areas, tourism areas and industrial areas, and the highest abundance of MPs was observed in the tourism and residential areas, suggesting the impacts of human activities. MPs in these parks were mainly in four kinds of shapes, namely fiber, pellet, fragment and film, and dominated by fibers and fragments. Most of the extracted MPs were small in size, and 63-92% of them were smaller than 0.5 mm. Polypropylene and polyethylene terephthalate were the main polymer types in surface water and sediments, respectively. This study showed that the park water and sediment can be used as an important "sink" in MPs, which is of great significance for monitoring and alleviating the pollution of urban MPs. This study provided important reference for better understanding MPs levels in inland freshwaters.

Selection, Characterization, and Optimization of DNA Aptamers against Challenging Marine Biotoxin Gymnodimine-A for Biosensing Application.

Gymnodimines (GYMs), belonging to cyclic imines (CIs), are characterized as fast-acting toxins, and may pose potential risks to human health and the aquaculture industry through the contamination of sea food. The existing detection methods of GYMs have certain defects in practice, such as ethical problems or the requirement of complicated equipment. As novel molecular recognition elements, aptamers have been applied in many areas, including the detection of marine biotoxins. However, GYMs are liposoluble molecules with low molecular weight and limited numbers of chemical groups, which are considered as "challenging" targets for aptamers selection. In this study, Capture-SELEX was used as the main strategy in screening aptamers targeting gymnodimine-A (GYM-A), and an aptamer named G48nop, with the highest KD value of 95.30 nM, was successfully obtained by screening and optimization. G48nop showed high specificity towards GYM-A. Based on this, a novel aptasensor based on biolayer interferometry (BLI) technology was established in detecting GYM-A. This aptasensor showed a detection range from 55 to 1400 nM (linear range from 55 to 875 nM) and a limit of detection (LOD) of 6.21 nM. Spiking experiments in real samples indicated the recovery rate of this aptasensor, ranging from 96.65% to 109.67%. This is the first study to report an aptamer with high affinity and specificity for the challenging marine biotoxin GYM-A, and the new established aptasensor may be used as a reliable and efficient tool for the detection and monitoring of GYMs in the future.

A Novel SELEX Based on Immobilizing Libraries Enables Screening of Saxitoxin Aptamers for BLI Aptasensor Applications.

Saxitoxin (STX) is one of the potent marine biotoxins that has high rate of lethality. However, there are no effective treatments at present, and the existing detection methods need to be further explored because of ethical problems or technical limitations. In this work, oligonucleotide aptamers toward STX were screened based on immobilizing libraries on Immobilized Metal-Chelate (IMC), such as Ni-NTA Sepharose, and the IMC-SELEX was conducted by the G-quadruplex library and the random library, respectively. Aptamer 45e (from the G-quadruplex library) and aptamer 75a were obtained after optimization, and aptamer 45e turned out to have a higher affinity toward STX. Furthermore, it was found that the hydrogen bonding and the van der Waals forces (VDW) played major roles in the high efficiency and specificity between STX and 45e by means of molecular docking and dynamics simulation. Based on this, aptamer 45e-1 with the Kd value of 19 nM was obtained by further optimization, which was then used to construct a simple, label-free and real-time optical BLI aptasensor for the detection of STX. This aptasensor showed good reproducibility and stability. In summary, with the advantages of screening aptamers of high efficiency and specificity toward the targets, the proposed IMC-SELEX provides a promising screening strategy for discovering aptamers, which could be used as the potential molecular recognition elements in the fields of biomedicine, food safety and environmental monitoring.

A Rapid and Sensitive Aptamer-Based Biosensor for Amnesic Shellfish Toxin Domoic Acid.

With the incidence of harmful algal blooms (HABs) increasing in recent years, the urgent demand for the detection of domoic acid (DA), an amnesic shellfish toxin mainly produced by red tide algae Pseudonitzschia, has aroused increasing attention. Aptamers, a new molecular recognition element, provide clarity in the monitoring of DA. In this study, aptamers of DA were successfully screened by Capture-SELEX. Through identification and truncation optimization, aptamer C1-d with a high affinity (KD value, 109 nM) and high specificity for DA was obtained. The binding mechanism between DA and the aptamer was explored by molecular docking and molecular dynamics (MD) simulation, revealing the critical sites for DA-aptamer interaction. Meanwhile, a BLI-based aptasensor was constructed by C1-d, which displayed a linear range from 0.625 to 10 µM and a LOD of 13.7 nM. This aptasensor exhibited high specificity, good precision and repeatability, and high recovery rates for real samples; the process of detection could be completed in 7 min. This study is the first to identify and investigate the binding mechanism of DA-aptamer interaction and constructed a BLI-based aptasensor for DA, which lays a theoretical foundation for the detection and prevention of DA.

Programmed Aptamer Screening, Characterization, and Rapid Detection for α-Conotoxin MI.

Conotoxins (CTXs) are a variety of mixed polypeptide toxins, among which α-conotoxin MI (CTX-MI) is the most toxic. Serious toxic symptoms, a lack of counteracting drugs, and cumbersome detection processes have made CTX-MI a hidden danger for humans. One of the obstacles to resolving this problem is the absence of specific recognition elements. Aptamers have shown great advantages in the fields of molecule detection, drug development, etc. In this study, we screened and characterized aptamers for CTX-MI through a programmed process. MBMI-01c, the isolated aptamer, showed great affinity, with an affinity constant (KD) of 0.524 µM, and it formed an antiparallel G-quadruplet (GQ) structure for the specific recognition of CTX-MI. Additionally, an aptasensor based on the biolayer interferometry (BLI) platform was developed and displayed high precision, specificity, and repeatability with a limit of detection (LOD) of 0.26 µM. This aptasensor provides a potential tool for the rapid detection of CTX-MI in 10 min. The aptamer can be further developed for the enrichment, detoxification, and biological studies of CTX-MI. Additionally, the programmed process is applicable to screening and characterizing aptamers for other CTXs.