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Optimizing an Abundance-Based Model for Satellite Remote Sensing of Phytoplankton Size Classes in the Bohai and Yellow Seas of China
No full textPhytoplankton size structure is crucial for the functionality of the ocean food web and biogeochemical cycling, serving as a key indicator for assessing the state of marine ecosystems quantitatively. Despite the development of various algorithms to quantify phytoplankton size classes (PSCs) using satellite ocean color data, their reliability in optically complex coastal regions remains uncertain and requires regional optimization. In this study, we optimized and compared typical abundance-based three-component PSC models for the Bohai and Yellow Seas (BYS) of China using an extensive in situ PSC dataset derived from pigment samples analyzed via high-performance liquid chromatography (HPLC). The optimized sea surface temperature (SST)-dependent abundance-based PSC model of the BYS (SA-PSC-BYS) generated the most accurate remotely sensed PSC datasets for the BYS and effectively reproduced the PSC patterns observed in previous in situ studies. These patterns highlight the prevalence of micro- and pico-phytoplankton at higher and lower total biomass levels, respectively, and the dominance of nanophytoplankton at the mid-range of total biomass. This reliable PSC model will be invaluable for future remote sensing studies aiming to understand the detailed spatiotemporal variability of PSCs in the BYS. Additionally, it has the potential to enhance our understanding of the trophic connections between phytoplankton size structure and fisheries, thereby facilitating the development of effective marine management strategies
Improvement of the selectivity of a molecularly imprinted polymer-based potentiometric sensor by using a specific functional monomer
No full textPotentiometric sensors based on the molecularly imprinted polymers (MIPs) as the receptors have been successfully developed for determination of various organic and biological species. However, these MIP receptors may suffer from problems of low selectivity. Especially, it would be difficult to distinguish the target analyte from its structurally similar interferents. In this work, we propose a novel strategy that using specific functional monomer to fabricate MIP with high selectivity towards the target molecule. The density functional theory calculations are used to investigate the interactions between the template and the functional monomer. The binding energy between the template and functional monomer can be used as the criterion for identifying the optimal monomer. As a proof-of-concept experiment, bisphenol A (BPA) is chosen as the template and the MIP is synthesized by the precipitation polymerization method using the specific allyl-beta-cyclodextrin (allyl-beta-CD) with high affinity towards BPA as the functional monomer. The high-affinity MIP is employed as the receptor for the construction of the potentiometric sensor. The proposed potentiometric sensor based on the MIP using allyl-beta-CD as the functional monomer shows an improved response performance in terms of selectivity and sensitivity compared to the conventional potentiometric sensor based on the MIP with the common monomer (i.e., methacrylic acid). This allyl-beta-CD MIP-based potentiometric sensor shows a detection limit of 0.29 mu M for BPA, which is about one order of magnitude lower than that obtained by the conventional MIP-based potentiometric sensor. We believe that utilizing a functional monomer with specific recognition ability towards target in the fabrication of MIP could provide an appealing way to construct highly selective MIP-based electrochemical and optical sensors
Colorimetric and fluorescent independent dual "signal on" biosensor for accurate detection of ochratoxin A based on aptamer-triggered biocatalytic reactions
No full textOchratoxin A (OTA) is a hazardous food contaminant with significant health risks. Dual -channel OTA detection is noted for its cross-reference capability and high accuracy. Still, challenges in addressing in -system corrections and "signal off" related false positives and limited signal gains remain. Herein, we developed a dual -channel "signal on" aptasensor with one recognition process and two independent signal outputs for OTA analysis. The OTA aptamer binds to magnetic beads (MBs) and partially hybridizes with a complementary -trigger (cDNATrigger) sequence. Adding OTA disrupts the duplex sequence, leading to G-quadruplex (G4) formation and enrichment on the MBs, which then interacts with hemin to catalyze a color signal. Concurrently, the freed cDNA-Trigger catalyzes an enzyme -free DNA circuit, producing a fluorescence signal. The magnetic enrichment and signal amplification strategies make the proposed assay demonstrate excellent sensitivity toward OTA, with limits of detection (LOD) of 0.017 pM in the fluorescence channel and 48.1 pM in the colorimetric channel. Both channels have effectively detected OTA in grape juice and baijiu, demonstrating their applicability and reliability. Moreover, given the widespread use of smartphones globally, a mini -program with a self -correction function was designed to facilitate on -site colorimetric channel monitoring, making OTA detection more accessible and user-friendly
Recent advances and challenges in monitoring chromium ions using fluorescent probes
No full textChromium is among the most strategic and critical transition metal elements and has extensive applications in both industrial and biological contexts. The most stable oxidation states of chromium are trivalent chromium (Cr (III)) and hexavalent chromium (Cr(VI)). Cr(III) is recognized as an effective trace nutrient, whereas Cr(VI) in its highest oxidation state poses a toxic threat to human health due to its potent oxidizing capacities. To mitigate the risk of poisoning, efficient detection methods have been developed to meet testing requirements. Comparing with traditional methods, colorimetric and fluorescent techniques have emerged as simple, time-efficient, highly selective and sensitive, cost-effective and particularly well-suited for biological applications. Furthermore, these methods excel in distinguishing between trivalent and hexavalent chromium, even in low-level concentrations and complex matrices. Since the scarcity of fluorescent probes for chromium, most existing reviews merely touch upon this topic without providing comprehensive coverage. Therefore, this review aims to consolidate information on small molecular fluorescent probes and fluorescent materials serve as fluorescent probes for monitoring Cr2+, Cr3+, Cr2O72- and CrO42- in environmental settings and living cells. We anticipate that this review will promote the development of novel fluorescent probes for chromium detection, facilitating their applications in chemical, biological and medical domains
An inversion model of microplastics abundance based on satellite remote sensing: a case study in the Bohai Sea
No full textNowadays, microplastics (MPs) as emerging contaminants have posed great risks to marine ecosystems and human health. However, non-continuous field sampling data makes it difficult to meet the needs of scientific research and pollution control of marine MPs. Consequently, the development of rapid monitoring techniques for marine MPs to achieve efficient acquisition of data is increasingly essential. Remote sensing technology provides a convenient and effective tool for monitoring and mapping marine MPs pollution. Therefore, we established an inversion model based on multiple regression by combining the remote sensing data and the measured data to predict the MPs pollution status in the Bohai Sea. The feature variables of a model are crucial to the prediction, and we proposed three methods of variable selection, namely successive projections algorithm (SPA), band combination method, and remote sensing index method. By comparing accuracy evaluation metrics, an approach based on SPA was selected to analyze the abundance and spatio-temporal distribution of MPs in the Bohai Sea in 2022. The determination coefficient of the SPA model is 0.75, and the root mean square error is 0.38 items/m3. The error of the model is within an acceptable range. It was found that the MPs abundance on the sea surface of the Bohai Sea varied significantly in different seasons and regions. This study indicates that satellite remote sensing technology has great potential in monitoring marine MPs
Nitrate transformation and source tracking of rivers draining into the Bohai Sea using a multi-tracer approach combined with an optimized Bayesian stable isotope mixing model
No full textExcessive levels of NO3 -can result in multiple eco-environmental issues due to potential toxicity, especially in coastal areas. Accurate source tracing is crucial for effective pollutant control and policy development. Bayesian models have been widely employed to trace NO3 -sources, while limited studies have utilized optimized Bayesian models for NO3 - tracing in the coastal rivers. The Bohai Rim is highly susceptible to ecological disturbances, particularly N pollution, and has emerged as a critical area. Therefore, identification the N fate and understanding their sources contribution is urgent for pollution mitigation efforts. In addition, understanding the influenced key driven factors to source dynamic in the past ten years is also implication to environmental management. In this study, water samples were collected from 36 major river estuaries that drain into the Bohai Sea of North China. The main transformation processes were analyzed and quantified the sources of NO3 -using a Bayesian stable isotope mixing model (MixSIAR) with isotopic approach (815N-NO3- and 818O-NO3-). The overall isotopic composition of 815N-NO3- and 818O-NO3- in estuary waters ranged from -0.8-19.3%o (9.3 +/- 4.6%o) and from -7.1-10.5%o (5.0 +/- 4.3%o), respectively. The main sources of nitrate in most river estuaries were manure & sewage, and chemical fertilizer, while weak denitrification and mixed processes were observed in Bohai Ri
A novel chitosan antioxidant bearing sulfhydryl group: Synthesis, characterization and activity assessment
No full textTo improve the antioxidant activity, sulfhydryl groups (-SH) were introduced into chitosan. Acylated chitosan derivatives, chitosan cationic salt derivatives, hydroxypropyl trimethylammonium chloride chitosan quaternary ammonium salt (HACC) derivatives and N,N,N-trimethyl chitosan iodine (TMC) derivatives were obtained. The chitosan derivatives were characterized by FTIR and 1H NMR to confirm the successful synthesis. Ellman's reagent was used to determine that the compound contained free sulfhydryl groups. The water solubility and thermal stability of chitosan and derivatives were evaluated. The antioxidant activities of the derivatives were verified, including DPPH radical scavenging activity, superoxide anion radical scavenging activity and reducing power activity. The novel chitosan derivatives showed excellent antioxidant activities. Toxicity assay used L929 cells proved that the derivatives had no significant toxic. The results showed that the chitosan derivatives bearing sulfhydryl groups described in this paper has a certain antioxidant effect, which provides a practical approach for further study of chitosan
Marine oil spill detection using improved polarimetric feature based on polarization SAR image
No full textMonitoring marine oil pollution holds both practical and scientific significance. Synthetic Aperture Radar (SAR) is an active microwave remote sensing technique capable of all-weather and all-day with fine spatial resolution. However, under low wind conditions, rain cells and young ice are examples of look-alikes affect the accuracy of oil spill detection. Polarimetric SAR assumes a crucial role in this context, as it can extract abundant polarimetric features by polarimetric target decomposition. Drawing inspiration from this advancement, an improved polarimetric feature named relative feature based on Cloude-Pottier target decomposition was proposed. The Jeffries-Matusita distance indicates the substantial potential of the relative feature in detecting oil spills. The improved polarimetric feature within U-Net, FCN-8s, and DeepLabv3+ResNet-18 for oil spill detection using polarization SAR images. Experiment results demonstrated that the relative feature has superior performance compared to other polarimetric features and obtained the highest accuracy and dice within U-Net compared to the other two models. These findings introduce promising concepts for achieving rapid and precise detection of oil spills in future applications
Effect of Hydrophobic Chain Length in Amphiphilic Chitosan Conjugates on Intracellular Drug Delivery and Smart Drug Release of Redox-Responsive Micelle
No full textThree redox-sensitive nanocarriers were rationally designed based on amphiphilic low molecular weight chitosan-cystamine-octylamine/dodecylamin/cetylamine (LC-Cys-OA, LC-Cys-DA, LC-Cys-CA) conjugates containing disulfide linkage for maximizing therapeutic effect by regulating hydrophobic interaction. The resultant spherical micelles had the characteristics of low CMC, suitable size, excellent biosafety and desired stability. The drug-loaded micelles were fabricated by embedding doxorubicin (Dox) into the hydrophobic cores. The effect of hydrophobic chain lengths of amphiphilic conjugates on encapsulation capacity, redox sensitivity, trigger-release behavior, cellular uptake efficacy, antitumor effect and antimigratory activity of Dox-loaded micelles was systematically investigated. Studies found that Dox-loaded LC-Cys-CA micelle had superior loading capacity and enhanced redox sensitivity compared with the other two micelles. Release assay indicated that the three Dox-loaded micelles maintained sufficiently stability in normal blood circulation but rapidly disintegrated in tumor cells. More importantly, the LC-Cys-CA micelle with a longer hydrophobic chain length exhibited a higher accumulative Dox release percentage than the other two micelles. Additionally, an increase in hydrophobic chain lengths of amphiphilic conjugates improved cellular uptake efficiency, antitumor effect and antimigration activity of Dox-loaded micelles, which could be explained by enhanced loading ability and redox sensitivity. Our research was expected to provide a viable platform for achieving a desired therapeutic efficacy via the alteration of hydrophobic interaction