High Ionic Strength Media Research Articles

Potential advantage of invasive estuarine worms over native species under exposure to relevant concentrations of graphene oxide: Behavioral and biochemical insights.

Technological development using graphene oxide (GO) has increased in the last years, leading to the release of this contaminant to final sinks, such as estuaries. Due to their potential to flocculate and deposit when interacting with high ionic strength media, GO poses a threat, especially to benthic organisms like polychaetes. In addition to chemical contamination, estuaries also face a severe threat from invasive species, which can cause irreversible damage to ecosystems. The combination of abiotic and biotic stressors may work together on native species, decreasing their resilience. Thus, this study aims to assess the effects of an abiotic stressor, GO nanosheets (0.001, 0.01, 0.1, 1, 10mg GO/Kg dw) on Hediste diversicolor (native species) and Arenicola marina (invasive species) through several behavioral assays and biochemical markers. The impact of invasive species A. marina (biotic factor) on H. diversicolor avoidance behavior was also evaluated. Obtained results demonstrated that H. diversicolor fled from lower GO contamination compartments to higher ones and that exposure to increased GO concentrations negatively impacted its burrowing activity. They were unable to escape from higher contamination compartments, but at the highest concentrations, the bioturbation activity was significantly higher, which may indicate that H. diversicolor tended to dwell deeper in the sediment. A. marina showed an escape behavior from compartments with higher GO concentrations. Additionally, this species' bioturbation activity significantly decreased when exposed to GO. Moreover, avoidance tests demonstrated that the presence of A. marina affected the behavior of H. diversicolor. Regarding oxidative stress, H. diversicolor seems to be more impacted than A. marina, since Lipid peroxidation levels were higher in all GO concentrations and Superoxide dismutase activity significantly increased in the lowest GO levels. Overall, H. diversicolor spatial distribution may be severely constrained under abiotic and biotic stress, while A. marina's higher foraging activity may promote its propagation in the estuary. Behavioral tests, combined with biochemical markers have shown to be relevant tools for the development of more environmental-realistic assessment and monitoring frameworks for estuaries.

Evaluation of extraction and storage conditions for quantification and characterization of silver nanoparticles in complex samples by single particle-ICP-MS

The extraction of nanoparticles (NPs) from complex matrices and subsequent storage can potentially alter the NPs physicochemical properties and hinder cross-study comparisons. Most NP extraction methods are designed and tested at high nanoparticle concentrations, although (eco)toxicological and regulatory monitoring programs require methods capable of analyzing NPs at environmentally relevant concentrations (lower ppb range). In this study, we investigated how extraction methods affect the characteristics of PVP coated and citrate-stabilized silver NPs (AgNPs) spiked into soil, sewage sludge, and biological samples at environmentally relevant concentrations using Single Particle Inductively Coupled Plasma Mass Spectrometry spICP-MS). Further we investigated the impact of storage temperature (-80°C to 21°C) and storage duration (1-28 days) on the particle characteristics such as particle size.We found that aqueous AgNPs samples with low ionic strength media retained their original characteristics (like particle size, particle concentration and particle-based Ag mass) when preserved at 4°C for up to 28 days. AgNPs dispersed in high ionic strength media were however better preserved at -80°C. Among the extraction agents, tetrasodium pyrophosphate was more efficient in extracting AgNPs from soil and sewage sludge matrices, while Proteinase K was more suitable for biological samples from organisms (earthworms or fish).Although our study focused only on AgNPs, it provides crucial information to aid interlaboratory comparisons and data interpretation for (eco)toxicological studies.

Zika Virus NS1 Protein Detection Using Gold Nanoparticle-Assisted Dynamic Light Scattering.

The Zika virus (ZIKV) is a global health threat due to its rapid spread and severe health implications, including congenital abnormalities and neurological complications. Differentiating ZIKV from other arboviruses such as dengue virus (DENV) is crucial for effective diagnosis and treatment. This study presents the development of a biosensor for detecting the ZIKV non-structural protein 1 (NS1) using gold nanoparticles (AuNPs) functionalized with monoclonal antibodies employing dynamic light scattering (DLS). The biosensor named ZINS1-mAb-AuNP exhibited specific binding to the ZIKV NS1 protein, demonstrating high colloidal stability indicated by a hydrodynamic diameter (DH) of 140 nm, detectable via DLS. In the absence of the protein, the high ionic strength medium caused particle aggregation. This detection method showed good sensitivity and specificity, with a limit of detection (LOD) of 0.96 µg mL-1, and avoided cross-reactivity with DENV2 NS1 and SARS-CoV-2 spike proteins. The ZINS1-mAb-AuNP biosensor represents a promising tool for the early and accurate detection of ZIKV, facilitating diagnostic and treatment capabilities for arboviral infections.

Switchable Coacervate Formation via Amino Acid Functionalization of Poly(dehydroalanine).

Our group recently developed a family of side-chain amino acid-functionalized poly(S-alkyl-l-homocysteines), Xaa-CH (Xaa = generic amino acid), which possess the ability to form environmentally responsive coacervates in water. In an effort to further study how the molecular structure affects polypeptide coacervate formation, we prepared side-chain amino acid-functionalized poly(S-alkyl-rac-cysteines), Xaa-rac-C, via post-polymerization modification of poly(dehydroalanine), ADH. The use of the ADH platform allowed straightforward synthesis of a diverse range of side-chain amino acid-functionalized polypeptides via direct reaction of unprotected l-amino acid 2-mercaptoethylamides with ADH. Despite their differences in the main-chain structure, we found that Xaa-rac-C can form coacervates with properties similar to those seen with Xaa-CH. These results suggest that the incorporation of side-chain amino acids onto polypeptides may be a way to generally favor coacervation. The incorporation of l-methionine in Met-rac-C allowed the preparation of coacervates with improved stability against high ionic strength media. Further, the presence of additional thioether groups in Met-rac-C resulted in an increased solubility change upon oxidation allowing facile reversible redox switching of coacervate formation in aqueous media.

Effect of Lipid Corona on Phenylalanine-Functionalized Gold Nanoparticles to Develop Stable and Corona-Free Systems.

Conventional gold nanoparticles (Au NPs) have many limitations, such as aggregation and subsequent precipitation in the medium of high ionic strength and protein molecules. Furthermore, when exposed to biological fluids, nanoparticles form a protein corona, which controls different biological processes such as the circulation lifetime, drug release profile, biodistribution, and in vivo cellular distribution. These limitations reduce the functionality of Au NPs in targeted delivery, bioimaging, gene delivery, drug delivery, and other biomedical applications. To circumvent these problems, there are numerous attempts to design corona-free and stable nanoparticles. Here, we report for the first time that lipid corona (coating of lipid) formation on phenylalanine-functionalized Au NPs (AuPhe NPs) imparts excellent stability against the high ionic strength of bivalent metal ions, amino acids, and proteins of different charges as compared to bare nanoparticles. Moreover, this work is focused on the ability of lipid corona formation on AuPhe NPs to prevent protein adsorption in the presence of cell culture medium (CCM), oppositely charged protein (e.g., histone 3), and human serum albumin (HSA). The results demonstrate that the lipid corona successfully protects the AuPhe NPs from protein adsorption, leading to the development of corona-free character. This unique achievement has profound implications for enhancing the biomedical utility and safety of these nanoparticles.

Characterization and Behaviour of Silica Engineered Nanocontainers in Low and High Ionic Strength Media.

Mesoporous silica engineered nanomaterials are of interest to the industry due to their drug-carrier ability. Advances in coating technology include using mesoporous silica nanocontainers (SiNC) loaded with organic molecules as additives in protective coatings. The SiNC loaded with the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), i.e., SiNC-DCOIT, is proposed as an additive for antifouling marine paints. As the instability of nanomaterials in ionic-rich media has been reported and related to shifting key properties and its environmental fate, this study aims at understanding the behaviour of SiNC and SiNC-DCOIT in aqueous media with distinct ionic strengths. Both nanomaterials were dispersed in (i) low- (ultrapure water-UP) and (ii) high- ionic strength media-artificial seawater (ASW) and f/2 medium enriched in ASW (f/2 medium). The morphology, size and zeta potential (ζP) of both engineering nanomaterials were evaluated at different timepoints and concentrations. Results showed that both nanomaterials were unstable in aqueous suspensions, with the initial ζP values in UP below -30 mV and the particle size varying from 148 to 235 nm and 153 to 173 nm for SiNC and SiNC-DCOIT, respectively. In UP, aggregation occurs over time, regardless of the concentration. Additionally, the formation of larger complexes was associated with modifications in the ζP values towards the threshold of stable nanoparticles. In ASW, SiNC and SiNC-DCOIT formed aggregates (<300 nm) independently of the time or concentration, while larger and heterogeneous nanostructures (>300 nm) were detected in the f/2 medium. The pattern of aggregation detected may increase engineering nanomaterial sedimentation rates and enhance the risks towards dwelling organisms.

Influence of Ethanol on the Acid-Induced Flocculation of Casein Micelles

The influence of ethanol (0–10%, v/v) on the acid-induced flocculation of casein micelles was examined using diffusing wave spectroscopy. For this purpose, samples containing 10% (w/w) reconstituted skim milk powder and 0–10% (v/v) ethanol were acidified with glucono-delta-lactone and acid-induced coagulation was monitored by diffusing wave spectroscopy. The pH at which acid-induced flocculation of the casein micelles commenced (pHf) increased near-linearly with increasing ethanol content, whereas the rate of flocculation was not affected by ethanol. The results are discussed in terms of the steric stabilisation of casein micelles by a polyelectrolyte brush in a medium of high ionic strength. Ethanol-induced increases in pHf are probably primarily due to an ethanol-induced reduction in solvent quality; an ethanol-induced reduction in dissociation of carboxylic acid groups in the brush is likely to contribute.

Preparation of Multifunctional N-Doped Carbon Quantum Dots from Citrus clementina Peel: Investigating Targeted Pharmacological Activities and the Potential Application for Fe3+ Sensing.

Carbon quantum dots (CQDs) have recently emerged as innovative theranostic nanomaterials, enabling fast and effective diagnosis and treatment. In this study, a facile hydrothermal approach for N-doped biomass-derived CQDs preparation from Citrus clementina peel and amino acids glycine (Gly) and arginine (Arg) has been presented. The gradual increase in the N-dopant (amino acids) nitrogen content increased the quantum yield of synthesized CQDs. The prepared CQDs exhibited good biocompatibility, stability in aqueous, and high ionic strength media, similar optical properties, while differences were observed regarding the structural and chemical diversity, and biological and antioxidant activity. The antiproliferative effect of CQD@Gly against pancreatic cancer cell lines (CFPAC-1) was observed. At the same time, CQD@Arg has demonstrated the highest quantum yield and antioxidant activity by DPPH scavenging radical method of 81.39 ± 0.39% and has been further used for the ion sensing and cellular imaging of cancer cells. The obtained results have demonstrated selective response toward Fe3+ detection, with linear response ranging from 7.0 µmol dm−3 to 50.0 µmol dm−3 with R2 = 0.9931 and limit of detection (LOD) of 4.57 ± 0.27 µmol dm−3. This research could be a good example of sustainable biomass waste utilization with potential for biomedical analysis and ion sensing applications.

Development of novel blue emissive carbon dots for sensitive detection of dual metal ions and their potential applications in bioimaging and chelation therapy

In recent years, there has been an increased interest in the use of fluorescent carbon dots (C-dots) as an alternative to toxic synthetic organic dyes in live cell imaging, medical diagnostics and other diverse biomedical applications. In the present work, highly fluorescent C-dots have been prepared from commercially available peptic digest of animal tissue, without using any additional chemical reagent for surface functionalization. The synthesized C-dots are monodispersed nanomaterials with hydroxyl, carboxyl and amino surface functionalities and remain stable in high ionic strength media and over a wide range of pH. They exhibit a strong blue fluorescence upon excitation at 350 nm with a high quantum yield of 61%. The potential use of these C-dots as fluorescent nanoprobe for specific metal ions (Cu2+ and Hg2+) detection through chelation, radical scavenging and cellular imaging has been investigated. These highly fluorescent labels show rapid cellular internalization without hampering cellular integrity. Cell proliferation assay demonstrates that these C-dots have minimal cell toxicity even at a high concentration of 3 mg/mL. They show significant quenching on incubation with cells pretreated with Cu2+ and Hg2+ ions. They also show rapid exocytosis from cells showcasing their high potential for chelation therapy. Thus, this study offers a scalable synthesis approach for highly fluorescent and bio-compatible C-dots from a cost-effective precursor, which can be used for specific metal ions detection and their removal from cells through chelation via exocytosis. They can also be used as an alternate to synthetic organic dyes for fluorescence-based cell-imaging.

Ethidium Binding to Salmonella enterica ser. Typhimurium Cells and Salmon Sperm DNA.

Bacterial resistance to antibiotics due to increased efficiency of the efflux is a serious problem in clinics of infectious diseases. Knowledge of the factors affecting the activity of efflux pumps would help to find the solution. For this, fast and trustful methods for efflux analysis are needed. Here, we analyzed how the assay conditions affect the accumulation of efflux indicators ethidium (Et+) and tetraphenylphosphonium in Salmonella enterica ser. Typhimurium cells. An inhibitor phenylalanyl-arginyl-β-naphtylamide was applied to evaluate the input of RND family pumps into the total efflux. In parallel to spectrofluorimetric analysis, we used an electrochemical assessment of Et+ concentration. The results of our experiments indicated that Et+ fluorescence increases immediately after the penetration of this indicator into the cells. However, when cells bind a high amount of Et+, the intensity of the fluorescence reaches the saturation level and stops reacting to the accumulated amount of this indicator. For this reason, electrochemical measurements provide more trustful information about the efficiency of efflux when cells accumulate high amounts of Et+. Measurements of Et+ interaction with the purified DNA demonstrated that the affinity of this lipophilic cation to DNA depends on the medium composition. The capacity of DNA to bind Et+ considerably decreases in the presence of Mg2+, Polymyxin B or when DNA is incubated in high ionic strength media.

Facile modification of montmorillonite by intercalation and grafting: The study of the binding mechanisms of a quaternary alkylammonium surfactant

Modified clays are among the most investigated organic-inorganic hybrid materials. Traditionally, they are prepared via reaction of the clay mineral with an organic substrate that can be bonded by cation exchange or by covalent grafting. However, the possibility of bonding one organic substrate to the clay mineral via these two mechanisms simultaneously has not been deeply investigated. In this study, a simple modification of a clay mineral was investigated via the reaction of a quaternary alkylammonium surfactant that possesses an alkoxysilane group [(3-trimethoxysilylpropyl)octadecyldimethylammonium chloride] (TPODAC) with raw bentonite that contains montmorillonite (Mt) as the main phase (~ 90%) and acid-activated bentonite (H5-Mt). The structures, morphologies, and compositions of natural and modified montmorillonites were investigated via various methods, which evidenced successful organic modification. The surface area of Mt. (50 m2g−1) was as expected for sodium bentonite. After acid activation, an increase of the BET area (120 m2g−1), a decrease of the cation-exchange capacity (CEC), and a loss of crystalline order were observed. The presence of TPODAC in the hybrid materials was evidenced by three IR absorption bands at approximately 2930 cm−1, 2860 cm−1, and 1475 cm−1. Negligible leaching of TPODAC from the hybrid materials in aqueous media at pH 3, 7, and 10, in hydrophobic media, and in high–ionic strength media were observed, thereby demonstrating the excellent chemical stability of these materials. A quantitative evaluation of the contribution of each binding mechanism of TPODAC in the hybrid materials was conducted by applying a surfactant-mineral interaction model in which grafting, cross-linking, and cation exchange mechanisms were proposed. The amounts of surfactant in the hybrid materials that were predicted by the model were in agreement with the results that were obtained via TGA.

Advanced strategy to exploit wine-making waste by manufacturing antioxidant and prebiotic fibre-enriched vesicles for intestinal health

Grape extract-loaded fibre-enriched vesicles, nutriosomes, were prepared by combining antioxidant extracts obtained from grape pomaces and a prebiotic, soluble fibre (Nutriose®FM06). The nutriosomes were small in size (from ∼140 to 260 nm), homogeneous (polydispersity index < 0.2) and highly negative (∼ −79 mV). The vesicles were highly stable during 12 months of storage at 25 °C. When diluted with warmed (37 °C) acidic medium (pH 1.2) of high ionic strength, the vesicles only displayed an increase of the mean diameter and a low release of the extract, which were dependent on Nutriose concentration. The formulations were highly biocompatible and able to protect intestinal cells (Caco-2) from oxidative stress damage. In vivo results underlined that the composition of mouse microbiota was not affected by the vesicular formulations. Overall results support the potential application of grape nutriosomes as an alternative strategy for the protection of the intestinal tract.

Comparison between gold nanoparticles synthesized by radiolysis and by EGCG-driven gold reduction

Radiolytic synthesis and phytochemical-driven gold reduction for the generation of nanoparticles are successful examples of Green Chemistry applied for nanomaterials. The present work compares these two green approaches focusing on hydrodynamic size, stability over time, optical properties and toxicity in NIH 3T3 (ATCC® CRL-1658™) cells and Danio rerio (Zebra Fish). The radiolytic synthesis was performed by mixing 1 mM NaAuCl4; polyvinyl pyrrolidone 0.5%, AgNO3 6 × 10−5 M, propan-2-ol 0.2 M and acetone 0.06 M, followed by irradiation at 15 kGy (5 kGy h−1, 60Co source). The EGCG-functionalized nanoparticles were synthesized by mixing 1.6 mM of Au with 0.8 mM of EGCG in phosphate buffer (10 mM) for 2 h. Both methods yield the formation of gold nanoparticles featuring plasmon resonance bands at 520–530 nm, polydispersity above 0.3 was relevant only for the radiolytic protocol. Regarding stability over time, after 30 days, the nanoparticles synthesized radiolytically presented no relevant size changes, while some aggregation was observed for the EGCG-particles. The same nanoparticles demonstrated a lack of stability in high ionic strength medium. Slight toxicity was observed for the EGCG-nanoparticles in Danio rerio, with an IC50 calculated as 40.49%, while no IC50 was established within the concentration range of radiolysis-AuNPs used in this study. In conclusion, both green methods generated nanoparticles with good control of size and optical properties, especially via reduction by EGCG. However, the stability and toxicity results were found to be more promising for the radiolytically synthesized gold nanoparticles.

Adjacent cationic\u2013aromatic sequences yield strong electrostatic adhesion of hydrogels in seawater

Electrostatic interaction is strong but usually diminishes in high ionic-strength environments. Biosystems can use this interaction through adjacent cationic–aromatic amino acids sequence of proteins even in a saline medium. Application of such specific sequence to the development of cationic polymer materials adhesive to negatively charged surfaces in saline environments is challenging due to the difficulty in controlling the copolymer sequences. Here, we discover that copolymers with adjacent cation–aromatic sequences can be synthesized through cation–π complex-aided free-radical polymerization. Sequence controlled hydrogels from diverse cation/aromatic monomers exhibit fast, strong but reversible adhesion to negatively charged surfaces in seawater. Aromatics on copolymers are found to enhance the electrostatic interactions of their adjacent cationic residues to the counter surfaces, even in a high ionic-strength medium that screens the electrostatic interaction for common polyelectrolytes. This work opens a pathway to develop adhesives using saline water.

Electrical Double Layer Gated Field Effect Transistor Biosensors for the Quantitative Detection of Beta-Human Chorionic Gonadotropin

In this research, we have developed biosensors to detect beta human chorionic gonadotropin (beta-HCG) which is a hormone widely used to test for pregnancy and also serves as a biomarker for risk assessment of certain types of cancers. The biosensor methodology is based on extended gate design of electrical double layer (EDL) gated field effect transistor (FET). In this study, we fabricated a sensor array chip and functionalized the gold electrode surface with antibodies to capture the antigen, beta-HCG. Each sensor in the sensor array chip consists of two gold electrodes, one connected to the gate voltage supply and the other connected to the gate terminal of the FET, which is located on isolated PCB such that the test solution does not directly contact the transistor active region. A hand-held sensor measurement unit is fabricated which can apply the biasing voltages, measurement the resulting drain current signal and display the output results in LCD monitor. Fluorescence measurement technique is used to confirm and analyze the surface functionalization with antibodies to beta-HCG. The relation between beta-HCG antigen concentration and electrical signal is established by testing the sensor array chips using the hand-held device. The test samples are prepared by diluting purified stock proteins in 1X PBS, as it simulates the physiological conditions of human urine. Using our FET biosensor, we can directly detect beta-HCG in high ionic strength media like 1X PBS, without performing additional sample processing. Most pregnancy tests have a sensitivity of 25–50 IU/l (1.5-3 ng/ml), based on immunochromatography which is the most widely technique for detection of beta-HCG. Using our sensor methodology, we can obtain a sensor response curve with a dynamic range of antigen concentration between 0.03 to 30 ng/ml. As the antigen concentration approximately approaches 10 ng/ml, the current gain value is nearly saturated. The result shows that when beta-HCG antigen concentration increases, current gain value decreases. This sensing methodology can facilitate quantitative detection of beta-HCG in physiological conditions, whereas the current commercially available assays provide only qualitative test results. The sensor demonstrates a very wide dynamic range of detection, with a very low detection limit, which shows the potential of our sensor to detect pregnancies in very early stages. Furthermore, this sensor platform can enable the use of beta-HCG for risk stratification of cancers as well. The sensor can be batch produced and does not use additional labels/reagents or sample pre-processing techniques, which can greatly enhance the cost-effectiveness, comparable to the current commercialized beta-HCG assays.

Surface and Interfacial Interactions in Dodecane/Brine Pickering Emulsions Stabilized by the Combination of Cellulose Nanocrystals and Emulsifiers.

Interfacial properties of cellulose nanocrystals (CNC) and surfactants were studied in high ionic strength (I) brines and correlated to the stability of dodecane/brine Pickering emulsions. Bis-(2-hydroxyethyl) cocoalkylamine (CAA), dodecyltrimethylammonium bromide (DTAB), and octyl-β-d-glucopyranoside (OGP) were adsorbed onto CNC in American Petroleum Institute (API) brine (I = 1.9 M) and synthetic seawater (SSW), with I = 0.65 M. Raman spectroscopy indicated that hydroxyl groups on the CNC surface interact with all three surfactants in high ionic strength media. Ionic interactions still play a role at the very large ionic strengths studied herein. Despite all surfactants adsorbing onto CNC, only the surface tension of CAA solutions in both brines was increased by the addition of 0.5 wt % CNC. The effect was much more prominent in API than in SSW. Contact angle measurements indicated that CAA increased the wettability of CNC by both brines in dodecane; DTAB, on the other hand, decreased wettability. Emulsion stability studies revealed that ionic strength, wettability, adsorption energy, and oil content strongly affect emulsion stability, more so than surfactant adsorption. In API, CNC aggregates alone stabilized the emulsions better compared to samples with additional emulsifiers; the same was true in SSW for oil contents below 50% v/v. For oil contents above 50% v/v in SSW, CAA was either detrimental or failed to improve emulsion stability. On the other hand, DTAB increased the stability of dodecane in SSW emulsions. Emulsions stable for over 21 months were prepared with oil contents of 75% v/v. The adsorption of CAA onto CNC limits the migration of both CNC and CAA to the dodecane/brine interface, while DTAB adsorption has the opposite effect.

On the formation of protein corona on colloidal nanoparticles stabilized by depletant polymers

To counter the undesired colloidal destabilization of nanoparticles in biologically-compatible media of high ionic strength (i.e. NaCl, phosphate buffer), polymers can be added to nanoparticle suspensions that will be used in biomedical applications. In these suspensions, polymers can promote high colloidal stability by manifestation of steric and/or depletion forces. However, little is known about the influence of these polymers on the interactions between nanoparticles and the biological components of the organism, such as proteins and cells. In this work, it was shown that the addition of the polymers (i) Pluronic-F127 (PF127), (ii) polyethylene glycol (PEG) of different molecular weights - 1.5, 12 and 35 kDa - and (iii) the protein bovine serum albumin (BSA) on colloidal silica nanoparticles (CSNPs; 135 nm) dispersed in phosphate-buffered saline (PBS) largely alter their colloidal stability through different mechanisms. Although all polymers were adsorbed on the CSNP surface, BSA maintained the CSNP dispersion in the medium by electrosteric stabilization mechanisms, while PEG and PF127 led to the occurrence of depletion forces between the particles. In addition, it was found that the interactions between polymers and CSNPs did not prevent proteins to access the nanoparticles' surface and have minimal effect on the formation of the protein corona when they were incubated in human blood plasma. On the other hand, BSA had a greater effect on the CSNP protein corona profile compared to other polymers (PEG and PF127). Together, these results confirm that biocompatible polymers PEG and PF127 can be used as colloidal stabilizing agents for nanoparticles since they preserve the accessibility of biomolecules to the nanoparticle surface, and they have little effect on the protein corona composition.

Multiplexed CVD Biomarker Detection in Human Serum Using Aptamer Immobilized High Electron Mobility Transistor

Cardiovascular diseases (CVDs) are the major causes of death in the world today. Identifying and managing CVD risk is of primary importance in efficient patient care. Proper risk assessment strategies can provide information to healthy as well as high risk individuals on how to better manage their health. This can greatly reduce the mortality rate of cardiovascular disease. Using protein based cardiac biomarkers for risk assessment can improve early diagnosis and aid in prognosis of CVDs. Semiconductor based electronic sensors are very attractive for rapid and sensitive protein detection. Highly Electron Mobility Transistor (HEMT) based sensors have been used in a variety of applications such as ion, gas and biomolecule sensing and possess desirable features such as high sensitivity and resistance to harsh chemical environment. In this research, A unique sensing methodology using AlGaN/GaN HEMT has been developed to directly detect target protein in high salt concentration environment. The target protein was captured on the surface of the gate electrode, which is separated from the transistor channel by a small gap, and functionalized with target specific aptamer. By forming an electrical double layer (EDL) structure, the solution capacitance modulates the FET drain current. In this way, highly sensitive determination of cardiac biomarkers in high ionic strength media such as 1X PBS and human serum can be realized. HEMT is fabricated using 4 mask processes: mesa isolation and defining active device area, ohmic contact deposition and annealing, metal interconnect deposition and device passivation. For electrical measurement, a pulsed gate electrode voltage is supplied to the gate electrode which creates a solution capacitance in the gap between the gate electrode and transistor dielectric. This solution capacitance modulates the potential drop across the transistor dielectric and hence the drain current. The solution capacitance changes when the device is functionalized with the target specific aptamer and when the target protein binds to the receptor. The aptamer based AlGaN/GaN HEMT biosensor can detect target proteins with high sensitivity, selectivity and a wide dynamic range of detection in 1X PBS (with 4% BSA) and clinical human serum samples.

A novel “modularized” optical sensor for pH monitoring in biological matrixes

A novel core-shell structure optical pH sensor is developed with upconversion nanoparticles (UCNPs) serving as the core and silica as the shell, followed by grafting bovineserumalbumin (BSA) as another shell via glutaraldehyde cross-linking. The obtained core-shell-shell structure is shortly termed as UCNPs@SiO2@BSA, and its surface provides a platform for loading various pH sensitive dyes, which are alike “modules” to make it feasible for measuring pHs within different pH ranges by simply regulating the type of dyes. Generally, a single pH sensitive dye is adopted to respond within a certain pH range. This study employs bromothymol blue (BTB) and rhodamine B (RhB) to facilitate their responses to pH variations within two ranges, i.e., pH 5.99–8.09 and pH 4.98–6.40, respectively, with detection by ratio-fluorescence protocol. The core-shell-shell structure offers superior sensitivity, which is tens of times more sensitive than those achieved by ratio-fluorescence approaches based on various nanostructures, and favorable stability is achieved in high ionic strength medium. In addition, this sensor exhibits superior photostability under continuous excitation at 980 nm. Thanks to the near infrared excitation in the core-shell-shell structure, it effectively avoids the self-fluorescence from biological samples and thus facilitates accurate sensing of pH in various biological sample matrixes.

Comparative ecotoxicity of polystyrene nanoparticles in natural seawater and reconstituted seawater using the rotifer Brachionus plicatilis

The impact of nanoplastics using model polystyrene nanoparticles (PS NPs), anionic (PS-COOH) and cationic (PS-NH2), has been investigated on the marine rotifer Brachionus plicatilis, a major component of marine zooplanktonic species. The role of different surface charges in affecting PS NP behaviour and toxicity has been considered in high ionic strength media. To this aim, the selected media were standardized reconstituted seawater (RSW) and natural sea water (NSW), the latter resembling more natural exposure scenarios. Hatched rotifer larvae were exposed for 24h and 48h to both PS NPs in the range of 0.5–50μg/ml using PS NP suspensions made in RSW and NSW. No effects on lethality upon exposure to anionic NPs were observed despite a clear gut retention was evident in all exposed rotifers. On the contrary, cationic NPs caused lethality to rotifer larvae but LC50 values resulted lower in rotifers exposed in RSW (LC50=2.75±0.67µg/ml) compared to those exposed in NSW (LC50=6.62±0.87µg/ml). PS NPs showed similar pattern of aggregation in both high ionic strength media (RSW and NSW) but while anionic NPs resulted in large microscale aggregates (Z-average 1109 ± 128nm and 998±67nm respectively), cationic NP aggregates were still in nano-size forms (93.99 ± 11.22nm and 108.3 ± 12.79nm). Both PDI and Z-potential of PS NPs slightly differed in the two media suggesting a role of their different surface charges in affecting their behaviour and stability. Our findings confirm the role of surface charges in nanoplastic behaviour in salt water media and provide a first evidence of a different toxicity in rotifers using artificial media (RSW) compared to natural one (NSW). Such evidence poses the question on how to select the best medium in standardized ecotoxicity assays in order to properly assess their hazard to marine life in natural environmental scenarios.