Development of a Quick and Highly Sensitive Amplified Luminescent Proximity Homogeneous Assay for Detection of Saxitoxin in Shellfish.

Saxitoxin (STX), an exceptionally potent marine toxin for which no antidote is currently available, is produced by methanogens and cyanobacteria. This poses a significant threat to both shellfish aquaculture and human health. Consequently, the development of a rapid, highly sensitive STX detection method is of great significance. The objective of this research is to create a novel approach for identifying STX. Therefore, amplified luminescent proximity homogeneous assay (AlphaLISA) was established using a direct competition method based on the principles of fluorescence resonance energy transfer and antigen-antibody specific binding. This method is sensitive, rapid, performed without washing, easy to operate, and can detect 8-128 ng/mL of STX in only 10 min. The limit of detection achieved by this method is as low as 4.29 ng/mL with coefficients of variation for the intra-batch and inter-batch analyses ranging from 2.61% to 3.63% and from 7.67% to 8.30%, respectively. In conclusion, our study successfully establishes a simple yet sensitive, rapid, and accurate AlphaLISA method for the detection of STX which holds great potential in advancing research on marine biotoxins.

Ultrasensitive Electrochemiluminescence Biosensing Platform Based on Polymer Dots with Aggregation-Induced Emission for Dual-Biotoxin Assay.

Multitarget assay has always been a hot topic in electrochemiluminescence (ECL) methods. Herein, a "on-off-on" ECL aptasensor was developed for the ultrasensitive and sequential detection of possible biological warfare agents, deoxynivalenol (DON) and abrin (ABR). As a luminophore, polymer dots (Pdots) with aggregation-induced emission exhibit high ECL efficiency in the aptasensor, i.e., the signal "on" state. The DON assays mainly depend on ECL quenching due to the efficient quenching effect between ferrocene-H2-ferrocene (Fc-H2-Fc) and Pdots, i.e., the signal "off" state. When the aptasensor is incubated with the oligonucleotide sequence S2 to replace Fc-H2-Fc, obvious ECL recovery occurs, i.e., the signal "on" state, which can be used to sequentially detect ABR. The limit of detection (LOD) for DON is 0.73 fg·mL-1 in the range of 5.0 to 50 ng·mL-1; and the LOD for ABR is ∼0.38 pg·mL-1 in the range of 1.25 pg·mL-1 to 1.25 µg·mL-1. The as-designed ECL aptasensor exhibits good stability and reproducibility, high specificity, and favorable practicality. Therefore, this work provides a new approach for assays of DON and ABR in food safety and can be used as a model to design an ultrasensitive ECL biosensor for multitarget detection.

Estimating the risks of exposure to harmful algal toxins among Scottish harbour seals.

Harmful algal bloom (HAB) toxins consumed by marine predators through fish prey can be lethal but studies on the resulting population consequences are lacking. Over the past approximately 20 years there have been large regional declines in some harbour seal populations around Scotland. Analyses of excreta (faeces and urine from live and dead seals and faecal samples from seal haulout sites) suggest widespread exposure to toxins through the ingestion of contaminated prey. A risk assessment model, incorporating concentrations of the two major HAB toxins found in seal prey around Scotland (domoic acid (DA), and saxitoxins (STX)), the seasonal persistence of the toxins in the fish and the foraging patterns of harbour seals were used to estimate the proportion of adults and juveniles likely to have ingested doses above various estimated toxicity thresholds. The results were highly dependent on toxin type, persistence, and foraging regime as well as age class, all of which affected the proportion of exposed animals exceeding toxicity thresholds. In this preliminary model STX exposure was unlikely to result in mortalities. Modelled DA exposure resulted in doses above an estimated lethal threshold of 1900 µg/kg body mass affecting up to 3.8 % of exposed juveniles and 5.3 % of exposed adults. Given the uncertainty in the model parameters and the limitations of the data these conclusions should be treated with caution, but they indicate that DA remains a potential factor involved in the regional declines of harbour seals. Similar risks may be experienced by other top predators, including small cetaceans and seabirds that feed on similar prey in Scottish waters.

Discovery of a series of portimine-A fatty acid esters in mussels.

Vulcanodinium rugosum is a benthic dinoflagellate known for producing pinnatoxins, pteriatoxins, portimines and kabirimine. In this study, we aimed to identify unknown analogs of these emerging toxins in mussels collected in the Ingril lagoon, France. First, untargeted data acquisitions were conducted by means of liquid chromatography coupled to hybrid quadrupole-orbitrap mass spectrometry. Data processing involved a molecular networking approach, and a workflow dedicated to the identification of biotransformed metabolites. Additionally, targeted analyses by liquid chromatography coupled to triple quadrupole mass spectrometry were also implemented to further investigate and confirm the identification of new compounds. For the first time, a series of 13-O-acyl esters of portimine-A (n = 13) were identified, with fatty acid chains ranging between C12:0 and C22:6. The profile was dominated by the palmitic acid conjugation. This discovery was supported by fractionation experiments combined with the implementation of a hydrolysis reaction, providing further evidence of the metabolite identities. Furthermore, several analogs were semi-synthesized, definitively confirming the discovery of these metabolization products. A new analog of pinnatoxin, with a molecular formula of C42H65NO9, was also identified across the year 2018, with the highest concentration observed in August (4.5 µg/kg). The MS/MS data collected for this compound exhibited strong structural similarities with PnTX-A and PnTX-G, likely indicating a substituent C2H5O2 in the side chain at C33. The discovery of these new analogs will contribute to deeper knowledge of the chemodiversity of toxins produced by V. rugosum or resulting from shellfish metabolism, thereby improving our ability to characterize the risks associated with these emerging toxins.

Exosomes as mediators of signal transmitters in biotoxins toxicity: a comprehensive review.

Small membranes known as exosomes surround them and are released by several cell types both in vitro and in vivo. These membranes are packed with a variety of biomolecules, including proteins, lipids, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and non-coding RNA (ncRNA). As a source of biological nanomaterials, exosomes play a role in information and substance transmission between cells and have been identified as a general method of facilitating communication during interactions between the body, target organs, and toxins.. In order to understand the changes and mechanism of the composition and level of exosomes after biotoxin infection, this review focuses on current findings on the exosomes and highlights their novel uses in the toxicity mechanism. Exosomes are mainly used as a delivery carrier or mediated by receptors, and play an immune role after the toxin enters the body. This review expounds on the importance of exosomes in the toxicological mechanism of biotoxins and provides new insights for further diagnosis of toxic biomarkers, detoxification, and treatment development.

Sudden peak in tetrodotoxin in French oysters during the summer of 2021: Source investigation using microscopy, metabarcoding and droplet digital PCR.

Tetrodotoxin (TTX) is a potent neurotoxin causing human intoxications from contaminated seafood worldwide and is of emerging concern in Europe. Shellfish have been shown to contain varying TTX concentrations globally, with concentrations typically higher in Pacific oysters Crassostrea gigas in Europe. Despite many decades of research, the source of TTX remains unknown, with bacterial or algal origins having been suggested. The aim of this study was to identify potential source organisms causing TTX contamination in Pacific oysters in French coastal waters, using three different techniques. Oysters were deployed in cages from April to September 2021 in an estuary where TTX was previously detected. Microscopic analyses of water samples were used to investigate potential microalgal blooms present prior or during the peak in TTX. Differences in the bacterial communities from oyster digestive glands (DG) and remaining flesh were explored using metabarcoding, and lastly, droplet digital PCR assays were developed to investigate the presence of Cephalothrix sp., one European TTX-bearing species in the DG of toxic C. gigas. Oysters analysed by liquid chromatography-tandem mass spectrometry contained quantifiable levels of TTX over a three-week period (24 June-15 July 2021), with concentrations decreasing in the DG from 424 µg/kg for the first detection to 101 µg/kg (equivalent to 74 to 17 µg/kg of total flesh), and trace levels being detected until August 13, 2021. These concentrations are the first report of the European TTX guidance levels being exceeded in French shellfish. Microscopy revealed that some microalgae bloomed during the TTX peak, (e.g., Chaetoceros spp., reaching 40,000 cells/L). Prokaryotic metabarcoding showed increases in abundance of Rubritaleaceae (genus Persicirhabdus) and Neolyngbya, before and during the TTX peak. Both phyla have previously been described as possible TTX-producers and should be investigated further. Droplet digital PCR analyses were negative for the targeted TTX-bearing genus Cephalothrix.

Emerging Insights into Brevetoxicosis in Sea Turtles.

This review summarizes the current understanding of how brevetoxins, produced by Karenia brevis during harmful algal blooms, impact sea turtle health. Sea turtles may be exposed to brevetoxins through ingestion, inhalation, maternal transfer, and potentially absorption through the skin. Brevetoxins bind to voltage-gated sodium channels in the central nervous system, disrupting cellular function and inducing neurological symptoms in affected sea turtles. Moreover, the current evidence suggests a broader and longer-term impact on sea turtle health beyond what is seen during stranding events. Diagnosis relies on the detection of brevetoxins in tissues and plasma from stranded turtles. The current treatment of choice, intravenous lipid emulsion therapy, may rapidly reduce symptoms and brevetoxin concentrations, improving survival rates. Monitoring, prevention, and control strategies for harmful algal blooms are discussed. However, as the frequency and severity of blooms are expected to increase due to climate change and increased environmental pollution, continued research is needed to better understand the sublethal effects of brevetoxins on sea turtles and the impact on hatchlings, as well as the pharmacokinetic mechanisms underlying brevetoxicosis. Moreover, research into the optimization of treatments may help to protect endangered sea turtle populations in the face of this growing threat.

Gut pathobiome mediates behavioral and developmental disorders in biotoxin-exposed amphibians.

Emerging evidence suggests a link between alterations in the gut microbiome and adverse health outcomes in the hosts exposed to environmental pollutants. Yet, the causal relationships and underlying mechanisms remain largely undefined. Here we show that exposure to biotoxins can affect gut pathobiome assembly in amphibians, which in turn triggers the toxicity of exogenous pollutants. We used Xenopus laevis as a model in this study. Tadpoles exposed to tropolone demonstrated notable developmental impairments and increased locomotor activity, with a reduction in total length by 4.37%-22.48% and an increase in swimming speed by 49.96%-84.83%. Fusobacterium and Cetobacterium are predominant taxa in the gut pathobiome of tropolone-exposed tadpoles. The tropolone-induced developmental and behavioral disorders in the host were mediated by assembly of the gut pathobiome, leading to transcriptome reprogramming. This study not only advances our understanding of the intricate interactions between environmental pollutants, the gut pathobiome, and host health but also emphasizes the potential of the gut pathobiome in mediating the toxicological effects of environmental contaminants.

Click Reaction-Mediated Fluorescent Immunosensor Based on Cu-MOF Nanoparticles for Ultrasensitive and High-Throughput Detection of Aflatoxin B1 in Food Samples.

Due to the high toxicity of aflatoxin B1 and its risks to human health, we developed a click reaction-mediated automated fluorescent immunosensor (CAFI) for sensitive detection of aflatoxin B1 based on the Cu(I)-catalyzed click reaction. With its large specific surface area, a copper-based metal-organic framework (Cu-MOF) was synthesized to adsorb and enrich the copper ion (Cu(II)) and then load the complete antigen (BSA-AFB1). After the immunoreaction, Cu(II) inside the Cu-MOF-Antigen conjugate would be reduced to Cu(I) in the presence of sodium ascorbate, which triggered the click reaction between the fluorescent donor-modified DNA and the receptor-modified complementary DNA to lead to a fluorescence signal readout. The whole reaction steps were finished by the self-developed automated immunoreaction device. This CAFI method showed a limit of detection (LOD) of 0.48 pg/mL as well as a 670-fold enhancement in sensitivity compared to conventional ELISA, revealing its great potential in practical applications and automated detection.

A review of poisoning with various types of biotoxins and its common clinical symptoms.

INTRODUCTION: Biotoxins are toxic substances that originate from living organisms and are harmful to humans. Therefore, we need to know the symptoms of biotoxins poisoning to manage the damage. The purpose of this study is to establish a practical diagnostic protocol for dealing with poisoned patients exposed to biotoxins. MATERIALS AND METHODS: The present study is a review study. Our studied community is articles and books matching the title of the project and relevant keywords. First, by searching the key words sign, symptom, biotoxins, relevant articles were extracted and studied from valid databases. By reviewing the studies based on the search strategy, four groups of biotoxins that were studied the most were identified. These four groups are marine biotoxins, bacterial biotoxins, fungal biotoxins and plant biotoxins. In each of these biotoxin groups, important toxins were selected and studied. RESULTS: A total of 1864 articles were initially identified from the databases searched in present study. After screening titles and abstracts, 26 articles were included in the systematic review. Specifically, 7 articles were included for bacterial toxins, 9 articles for marine toxins, 5 articles for plant toxins and 5 articles for fungal toxins. CONCLUSION: The symptoms of plant biotoxins poisoning may include cardiovascular, hematologic, neurologic, respiratory, renal, and gastrointestinal symptoms, while the symptoms of fungal biotoxins poisoning may include hepatic, renal, gastrointestinal, musculoskeletal, metabolic, respiratory, neurological, and cardiovascular symptoms. marine biotoxins poisoning presents with gastrointestinal and neurological symptoms, with varying incubation periods and recovery times. bacterial biotoxins exposure can lead to a wide range of clinical symptoms, with diarrhea, vomiting, and abdominal pain being the most common, and hemoglobinuria or hematuria being a sensitive and specific clinical manifestation for diagnosing ongoing HUS in children.

Development of magnetic fluorescence aptasensor for sensitive detection of saxitoxin based on Fe3O4@Au-Pt nanozymes.

In this work, on the basis of Fe3O4@Au-Pt nanozymes (MAP NZs) and aptamer recognition, a magnetic fluorescent aptasensor (MFA) was developed for sensitive and accurate detection of saxitoxin (STX). With the bridge of STX aptamer (AptSTX) and complementary DNA (cDNA), AptSTX decorated MAP NZs (MAP/Apt) and cDNA modified green quantum dots (cDNA@g-QDs) were connected to form MAP/Apt-cDNA@g-QDs complex. As STX behaves a strong binding ability towards AptSTX, it will compete with cDNA and hybridize with Apt to release cDNA@g-QDs. With the addition of TMB, MAP will catalyze TMB to the oxidized TMB (ox-TMB), thereby quenching the fluorescence of g-QDs due to the inner filter effect. Based on this finding, the quantitative relationship between the change in fluorescence of gQDs and STX concentration was explored with a limit of detection (LOD, S/N = 3) of 0.6 nM. An internal standard signal of oxTMB was adopted and reduced the fluctuation of fluorescence signal output. Besides, the fluorescence probe can selectively recognize and detect STX among five marine toxins. Eventually, the MFA method behaved good performance in detecting seafood samples with recoveries of 82.0 % âˆ¼ 102.6 % as well as coefficient of variations (CV) of 7.2 % âˆ¼ 10.3 %. Therefore, the method with internal signal is hopeful to be a potential candidate for sensitive and accurate detection of STX in seafood.

Assessment of the health risks associated with the consumption of bivalve mollusks potentially contaminated with phycotoxins from the coastal ecosystem of the Ebrié lagoon, Côte d'Ivoire.

This work focused on assessing of the risk associated with the consumption of bivalve mollusks, potentially contaminated with phycotoxins. The studied phycotoxins are saxitoxin (STX), okadaic acid (OA), dinophysistoxins (DTXs), yessotoxins (YTXs), pectenotoxins (PTX), azaspiracids (AZAs), and domoic acid (DA). These toxins were investigated in three species of bivalve mollusks (Anadara senilis, Crassostrea gasar, and Perna perna), originating from the Ebrié lagoon. Chemical analyses were carried out by LC-MS/MS, HPLC-FLD, and HPLC-UV. The level of OA and DTXs, STX, and DA was 10.92 µg OA eq./kg, 9.6 µg STX eq./kg, and 0.17 mg DA eq./kg, respectively. The level of PTXs and AZAs was 3.3 µg PTX-2 eq./kg and 13.86 µg AZA-1 eq./kg; that of YTXs was 0.01 mg YTX eq./kg. The daily exposure dose (DED) was 0.019 µg OA eq./kg bw for OA and DTXs; 0.285 µg DA eq./kg bw for DA; 0.006 µg PTX-2 eq./kg bw for PTXs; 0.016 µg STX eq./kg bw for STX; 0.01 µg YTX eq./kg bw for YTXs; and 0.024 µg AZA-1 eq./kg bw for AZAs for the oyster Crassostrea gasar. These estimated values are lower than the acute reference dose (ARfD) of each phycotoxin recommended by the European Food Safety Agency (EFSA). The risk of harmful effects is acceptable. The absence of risk is valid only for the study period (11 months) and concerns coastal populations living near the sampling points.

Development of a highly sensitive aptamer-based electrochemical sensor for detecting saxitoxin based on K3Fe(CN)6 regulated silver nanoparticles.

BACKGROUND: Saxitoxin (STX) is the most toxic marine toxin, which can pose several adverse effects on human health. High sensitivity, fast response, and low-cost detection of STX contamination are of significance to reducing the fishery and seafood industries' loss. Among the various types of biosensors, the electrochemical biosensors have been extensively studied in the detection of STX, but the electrode surface modification material is easy to fall off, resulting in unstable electrochemical signals and poor reproducibility. It is imperative to have a ratiometric electrochemical biosensor for STX. RESULTS: In this study, we developed a novel aptamer-based electrochemical sensor (AECs) for the sensitive detection of STX based on a K3Fe(CN)6 regulated silver nanoparticles (Ag NPs) modified with aptamer. The AECs was constructed by immobilizing aptamer on Ag NPs surfaces. Under optimized conditions, the AECs showed a linear response towards STX in the range from 0.04 to 0.15 µM with the regression equation of Y = -8.0 + 233.7 X (R2 = 0.9956). The limit of detection (LOD) was calculated to be 1 nM (based on 3 N/S), which is significantly lower than the regulatory limits for STX in seafood. Moreover, the AECs showed excellent sensitivity, reproducibility and stability, as well as the detection in samples with acceptable recovery ranged from 71.2 % to 93.8 %, demonstrating its broad application prospects in detection of STX in seafood samples. SIGNIFICANCE: This work proposed an AECs to achieve sensitive detection of STX. A reaction system of K3Fe(CN)6 etched Ag NPs was introduced and used as the signal source to avoid the instability of the electrochemical signal, which can produce a ratiometric electrochemical signal output mode, improving the stability and sensitivity of electrochemical detection of STX.

Emerging challenges in maintaining marine food-fish availability and food safety.

The marine finfish and crustaceans contribute immensely to human nutrition. Harvesting marine food-fish to meet the global demand has become a challenge due to reduction of the fishery areas and food safety hazards associated with increased pre-harvest and post-harvest contaminations. The causes of low fish availability and contaminations were reviewed following the published literature from 2000 to 2023. The marine fish yields are stressed due to spread of contaminants triggered by rising sea temperatures, transport of microorganisms by marine vessels across the oceans, anthropogenic activities leading to increase in the toxic microorganisms, and the entry of toxic chemicals and antibiotic residues into the seawater through rivers or directly. Processing adds pyrogenic chemicals to foods. The hazardous materials may accumulate in the food-fish, beyond tolerance limits permitted for human foods. While the research and control measures focus on minimizing the hazards due to pathogenic microorganisms and chemicals in market fish, there is less discussion on the unhealthy changes occurring in the oceans affecting the quantity and quality of food-fish, and the origins of microbial and chemical contaminations. This review examines the factors affecting availability of wild food-fish and increased contaminations. It aims to bridge the knowledge gaps between the spread of hazardous agents in the marine environment, and their effects on the food-fish. Meeting the future human food security and safety through marine fish and fish products may need marine cage farming, introduction of genetically modified high yielding food-fish, and cultured contaminant free finless fish muscles as options.

A New Bioassay for the Detection of Paralytic and Amnesic Biotoxins Based on Motor Behavior Impairments of Zebrafish Larvae.

The global concern about the increase of harmful algal bloom events and the possible impacts on food safety and aquatic ecosystems presents the necessity for the development of more accessible techniques for biotoxin detection for screening purposes. Considering the numerous advantages that zebrafish present as a biological model and particularly as a toxicants sentinel, we designed a sensitive and accessible test to determine the activity of paralytic and amnesic biotoxins using zebrafish larvae immersion. The ZebraBioTox bioassay is based on the automated recording of larval locomotor activity using an IR microbeam locomotion detector, and manual assessment of four complementary responses under a simple stereoscope: survival, periocular edema, body balance, and touch response. This 24 h acute static bioassay was set up in 96-well microplates using 5 dpf zebrafish larvae. For paralytic toxins, a significant decrease in locomotor activity and touch response of the larvae was detected, allowing a detection threshold of 0.1-0.2 µg/mL STXeq. In the case of the amnesic toxin the effect was reversed, detecting hyperactivity with a detection threshold of 10 µg/mL domoic acid. We propose that this assay might be used as a complementary tool for environmental safety monitoring.

Gambierone and Sodium Channel Specific Bioactivity Are Associated with the Extracellular Metabolite Pool of the Marine Dinoflagellate Coolia palmyrensis.

Tropical epibenthic dinoflagellate communities produce a plethora of bioactive secondary metabolites, including the toxins ciguatoxins (CTXs) and potentially gambierones, that can contaminate fishes, leading to ciguatera poisoning (CP) when consumed by humans. Many studies have assessed the cellular toxicity of causative dinoflagellate species to better understand the dynamics of CP outbreaks. However, few studies have explored extracellular toxin pools which may also enter the food web, including through alternative and unanticipated routes of exposure. Additionally, the extracellular exhibition of toxins would suggest an ecological function and may prove important to the ecology of the CP-associated dinoflagellate species. In this study, semi-purified extracts obtained from the media of a Coolia palmyrensis strain (DISL57) isolated from the U.S. Virgin Islands were assessed for bioactivity via a sodium channel specific mouse neuroblastoma cell viability assay and associated metabolites evaluated by targeted and non-targeted liquid chromatography tandem and high-resolution mass spectrometry. We found that extracts of C. palmyrensis media exhibit both veratrine enhancing bioactivity and non-specific bioactivity. LC-HR-MS analysis of the same extract fractions identified gambierone and multiple undescribed peaks with mass spectral characteristics suggestive of structural similarities to polyether compounds. These findings implicate C. palmyrensis as a potential contributor to CP and highlight extracellular toxin pools as a potentially significant source of toxins that may enter the food web through multiple exposure pathways.

Intrinsic Factors Associated with Dietary Toxin Quantity and Concentration in the Nuchal Glands of a Natricine Snake Rhabdophis Tigrinus.

The snake Rhabdophis tigrinus sequesters cardiotonic steroids, bufadienolides (BDs), from ingested toads and stores them in the nuchal glands as defensive toxins. It has previously been shown that there are individual differences in the total quantity of BDs stored in the nuchal glands of adult R. tigrinus and that BD quantities and profiles of R. tigrinus exhibit geographic variation. However, no previous study has examined the total quantity of BDs as a percentage of body mass (relative BD quantity) and the concentration of BDs in the nuchal gland fluid (BD gland concentration). In addition, intrinsic factors that are associated with relative BD quantity and BD concentration have not been examined within a single population. We collected 158 adult snakes from an area of central Japan from May to October and analyzed their BD quantities by UV analysis. We assessed individual differences in BD quantity, relative BD quantity and BD gland concentration. We found that 1) in approximately 60% of the 158 individuals, the BD gland concentration was greater than 50%; 2) body length and body condition are positively correlated with relative BD quantity and BD gland concentration; 3) even in a single population, individual differences of BD quantity are large, and are greater in females than in males; and 4) relative BD quantity and BD gland concentration of females during the gestation season are lower than those during the non-gestation season.

Domoic Acid Oxidative Effects on the Microalgae Phaeodactylum tricornutum.

Domoic acid (DA) is a natural occurring marine biotoxin. Oxidative stress generation due to DA exposure was reported in animals, but little is known on the phytoplankton community. The aim of this work was to verify whether exposure to DA in the marine diatom Phaeodactylum tricornutum favors reactive oxygen species (ROS) generation in the intracellular environment modifying its antioxidant capacity. Active species production, non-enzymatic antioxidant content, and antioxidant enzyme activities over the three growth phases of P. tricornutum exposed to 64 µM DA were evaluated. Results obtained in exponential growing cells showed a time-depending seven-fold increase in the 2',7' dichlorofluorescein diacetate dye oxidation rate. Superoxide dismutase and catalase activities showed a two-fold increase, and glutathione related enzymes activities were also significantly increased in treated diatoms as compared to controls. However, glutathione and ascorbate contents significantly decreased after incubation of the cells with DA. Similar effects were observed in latent and stationary phases of cell development. These results showed that DA could cause a severe oxidant-dependent impact on a non-toxic algae.

EGCG inactivates a pore-forming toxin by promoting its oligomerization and decreasing its solvent-exposed hydrophobicity.

Natural proteinaceous pore-forming agents can bind and permeabilize cell membranes, leading to ion dyshomeostasis and cell death. In the search for antidotes that can protect cells from peptide toxins, we discovered that the polyphenol epigallocatechin gallate (EGCG) interacts directly with melittin from honeybee venom, resulting in the elimination of its binding to the cell membrane and toxicity by markedly lowering the extent of its solvent-exposed hydrophobicity and promoting its oligomerization into larger species. These physicochemical parameters have also been shown to play a key role in the binding to cells of misfolded protein oligomers in a host of neurodegenerative diseases, where oligomer-membrane binding and associated toxicity have been shown to correlate negatively with oligomer size and positively with solvent-exposed hydrophobicity. For melittin, which is not an amyloid-forming protein and has a very distinct mechanism of toxicity compared to misfolded oligomers, we find that the size-hydrophobicity-toxicity relationship also rationalizes the pharmacological attenuation of melittin toxicity by EGCG. These results highlight the importance of the physicochemical properties of pore forming agents in mediating their interactions with cell membranes and suggest a possible therapeutic approach based on compounds with a similar mechanism of action as EGCG.

Quantitative Sensing of Domoic Acid from Shellfish Using Biological Photonic Crystal Enhanced SERS Substrates.

Frequent monitoring of sea food, especially shellfish samples, for the presence of biotoxins serves not only as a valuable strategy to mitigate adulteration associated health risks, but could also be used to develop predictive models to understand algal explosion and toxin trends. Periodic toxin assessment is often restricted due to poor sensitivity, multifarious cleaning/extraction protocols and high operational costs of conventional detection methods. Through this work, a simplistic approach to quantitatively assess the presence of a representative marine neurotoxin, Domoic acid (DA), from spiked water and crab meat samples is presented. DA sensing was performed based on surface-enhanced Raman scattering (SERS) using silver nanoparticle enriched diatomaceous earth­a biological photonic crystal material in nature. Distinctive optical features of the quasi-ordered pore patterns in diatom skeleton with sporadic yet uniform functionalization of silver nanoparticles act as excellent SERS substrates with improved DA signals. Different concentrations of DA were tested on the substrates with the lowest detectable concentration being 1 ppm that falls well below the regulatory DA levels in seafood (>20 ppm). All the measurements were rapid and were performed within a measurement time of 1 min. Utilizing the measurement results, a standard calibration curve between SERS signal intensity and DA concentration was developed. The calibration curve was later utilized to predict the DA concentration from spiked Dungeness crab meat samples. SERS based quantitative assessment was further complemented with principal component analysis and partial least square regression studies. The tested methodology aims to bring forth a sensitive yet simple, economical and an extraction free routine to assess biotoxin presence in sea food samples onsite.