Hydrodynamic Size Distribution Research Articles

Rapid in-situ green synthesis and antibacterial properties of silver nanoparticles

In-situ green synthesis of silver nanoparticles (AgNPs) using hydroxypropyl-methylcellulose (HPMC) as a reducing and stabilizing agent is presented in this paper. A simple solution-casting method is used for preparing nanocomposite films. The reduction of silver ions to silver elementary particles was completed when the alkaline pH was maintained. The initial confirmation of AgNPs was visualized by the brown color of the prepared solution and later confirmed by the surface Plasmon resonance peak obtained from the UV–visible absorption study. X-ray diffraction measurement study revealed the crystalline nature of the AgNPs with FCC structure. The uniform distribution of AgNPs in the HPMC matrix is witnessed by Scanning electron microscope. The spherical shape of the prepared AgNPs is observed by transmission electron microscopic images with an average size of 11 nm. Dynamic light scattering experiment exposed the hydrodynamic size distribution and good stability of AgNPs. Thermogravimetric analysis showed high thermal stability of nanocomposites. Mechanical studies showed increased elongation at break and tensile strength of the prepared nanocomposites. Dielectric constant and dielectric loss were ascertained to decrease with an increase in frequency. Further, the antibacterial activity study showed an excellent activity of AgNPs in contrast to human bacterial pathogens viz.,Staphylococcus aureusandEscherichia coli.

Performance Assessment of Bismuth Ferrite Nanoparticles in Enhancing Oilwell Cement Properties: Implications for Sustainable Construction

Summary Oilwell cement ensures wellbore stability and isolates zones while bearing casing load and formation pressure. Its properties, crucial in extreme downhole conditions, include compressive strength, fluid loss resistance, and durability. In the present work, bismuth ferrite nanoparticles (BFO NPs) were synthesized using the sol-gel method and used as an additive in oilwell cement. The synthesized BFO NPs were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), and dynamic light scattering (DLS) techniques to analyze the functional groups, crystalline structure, morphological features, and hydrodynamic size distribution. Tests at 70°C and 2,000 psi revealed that 1% by weight of cement (BWOC) BFO NPs increased compressive strength by ~136% and reduced fluid loss to ~64% compared with base cement. It can be conjectured that the exposed facets of BFO NPs containing oxygen act as nucleating sites that promote the ordering of the silicate tetrahedra, thereby increasing the strength and crystallinity and reducing the water loss. The experimental results confirm that the BFO NPs can improve the properties of oilwell cement slurry at high-pressure, high-temperature (HPHT) conditions. This research underscores the potential of BFO NPs as sustainable additives for optimizing oilwell cement performance under challenging HPHT conditions, paving the way for advancements in sustainable construction practices.

Synthesis and Characterization of Silver Nanoparticles Using Bioreductant Andong Leaf Extract (Cordyline fruticosa (L) A. Chev.)

Silver nanoparticles are known to play a crucial role in various fields, prompting researchers to undertake synthesis and modification to obtain nanoscale particles. Silver nanoparticles were synthesized using a green synthesis-based chemical method with an extract from Cordyline fruticosa (L.) A. Chev. This study aims to determine the optimum conditions, including pH parameters, reaction time, and concentration, and assess the silver nanoparticles’ stability and characteristics. The research findings revealed that the optimal conditions for synthesizing silver nanoparticles were an extract pH of 11, a reaction time of 60 minutes, a AgNO3 concentration of 1.5 x 10-4 M, and an extract concentration of 0.008%. Characterization showed that silver nanoparticles were spherical, ranging from 5 to 20 nm and had an average hydrodynamic size distribution of 100.8 nm. In conclusion, leaf extract of Cordyline fruticosa (L.) A. Chev. can be utilized as a bioreductant and stabilizing agent, as indicated by stability test results, which showed considerable stability over a storage period of three months.

Facile Synthesis of PEGylated Gold Nanoparticles for Enhanced Colorimetric Detection of Histamine.

Histamine is among the biogenic amines that are formed during the microbial decarboxylation of amino acids in various food products, posing a significant threat to both food safety and human health. Herein, we present a one-step synthesis of PEGylated gold nanoparticles (PEG-AuNPs) for rapid, simple, and cost-effective colorimetric histamine detection. PEG-AuNPs' surface plasmon resonance (SPR) range at 520-530 nm with a hydrodynamic size distribution of 20-40 nm. Fourier transform infrared (FT-IR) spectra confirmed the reduction of AuNPs at 1645 cm-1 along with the other observed peaks at 2870, 1350, and 1100 cm-1 as a strong evidence for the presence of PEG. Upon the addition of histamine to the PEG-AuNP solution, transmission electron microscopy (TEM) highlighted the aggregation of nanoparticles. In addition, red shifting and a decrease in the absorbance of the SPR peak along with the appearance of an additional peak at ∼690 nm was observed in the PEG-AuNP absorption spectra in the presence of histamine. Increasing the PEG concentration in the gold colloids leads to the formation of a protective barrier around the surface of nanoparticles, which influences the colloidal stability by impeding the aggregation of PEG-AuNPs upon histamine addition. The minimum colorimetric response of PEG-AuNPs to histamine concentration is 30 ppm, as assessed by the naked eye. The absorption ratio (A690/A526) showed a linear dynamic range from 20 to 100 ppm with a limit of detection of 9.357 μM. Additionally, the assay demonstrates a commendable selectivity toward histamine analyte.

In silico molecular docking and ADMET prediction of biogenic zinc oxide nanoparticles: characterization, and in vitro antimicrobial and photocatalytic activity.

Biogenic synthesis of metal oxide nanoparticles is a rapidly growing research area in the field of nanotechnology owing to their immense potential in multifaceted biomedical and environmental applications. In this study, zinc oxide (ZnO) nanoparticles (NPs) were biosynthesized from the Citrullus lanatus rind extract to elucidate their potential antimicrobial and dye degradation activity. The structural, morphological, and optical properties of the NPs were examined using various analytical techniques. UV-vis spectra showed a λ max at 370 nm and the optical band gap was determined to be 3.2 eV for the ZnO nanocomposite. The FTIR spectrum denoted the functional groups responsible for the reduction of zinc acetate precursor to ZnO NPs. XRD demonstrated that the mean crystalline size of the nanocomposites was 20.36 nm while DLS, ζ-potential, FE-SEM, and EDX analysis of synthesized NPs confirmed their hydrodynamic size distribution, stability, morphological features, and elemental compositions, respectively. Biogenic ZnO NPs unveiled potent antimicrobial activity against S. aureus, L. monocytogenes, E. coli, P. aeruginosa, and C. albicans, showing 13 to 22 mm ZOI. This bactericidal activity of ZnO NPs was further elucidated using molecular docking analysis. The results showed a favorable lowest binding energy between ZnO NPs and microbial proteins (AusA for S. aureus, and CAT III for E. coli), which led to a possible mechanistic approach for ZnO NPs. Furthermore, the remarkable photocatalytic activity of ZnO NPs was revealed by the degradation of 99.02% of methylene blue (MB) dye within 120 min. Therefore, the above findings suggest that green synthesized ZnO NPs can be exploited as an eco-friendly alternative to synthetic substances and a unique promising candidate for therapeutic applications and environmental remediation.

PH-responsive niosome-based nanocarriers of antineoplastic agents.

Differences in pH between the tumour interstitium and healthy tissues can be used to induce conformational changes in the nanocarrier structure, thereby triggering drug release at the desired site. In the present study, novel pH-responsive nanocarriers were developed by modifying conventional niosomes with hexadecyl-poly(acrylic acid)n copolymers (HD-PAAn). Niosomal vesicles were prepared by the thin film hydration method using Span 60, Span 60/Tween 60 and cholesterol as main constituents, and HD-PAA modifiers of different concentrations (0.5, 1, 2.5, 5 mol%). Next, two model substances, a water-soluble fluorescent dye (calcein) and a hydrophobic agent with pronounced antineoplastic activity (curcumin), were loaded in the aqueous core and hydrophobic membrane of the elaborated niosomes, respectively. Physicochemical properties of blank and loaded nanocarriers such as hydrodynamic diameter (Dh), size distribution, zeta potential, morphology and pH-responsiveness were investigated in detail. The cytotoxicity of niosomal curcumin was evaluated against human malignant cell lines of different origins (MJ, T-24, HUT-78), and the mechanistic aspects of proapoptotic effects were elucidated. The formulation composed of Span 60/Tween 60/cholesterol/2.5% HD-PAA17 exhibited optimal physicochemical characteristics (Dh 302 nm; ζ potential -22.1 mV; high curcumin entrapment 83%), pH-dependent drug release and improved cytotoxic and apoptogenic activity compared to free curcumin.

Estimation of biomolecule amount by analyzing magnetic nanoparticle cluster distributions from alternating current magnetization spectra for magnetic biosensing

The hydrodynamic size distribution of magnetic nanoparticle (MNP) clusters is crucial for determining the amounts of biomolecules by analyzing the distributions of the Brownian relaxation time in the corresponding alternating current (AC) magnetization spectra. This study proposes a method for estimating the distribution of MNP clusters from recorded AC magnetization spectra using an experimental-based model. The proposed model is used to form a matrix equation that comprises the distribution and AC magnetization spectra of MNP clusters, and the MNP–biomolecule cluster distribution is obtained by solving an inverse problem. The results show that the variations in the MNP clusters distribution estimated from the model correspond to those measured by dynamic light scattering. The MNP cluster distributions estimated using the experimental model were used to estimate streptavidin concentrations in the range of 0.19–3.38 μM. The estimated values agree accurately with the true values, demonstrating the feasibility of the proposed method for biosensing.

Assessing the In Vitro Digestion of Lactoferrin-Curcumin Nanoparticles Using the Realistic Gastric Model.

Nanosized delivery systems have been the subject of research and discussion in the scientific community due to their unique properties and functionality. However, studies reporting the behaviour of nanodelivery systems under dynamic in vitro digestion conditions are still very scarce. To address this gap, this study aims to assess the dynamic in vitro gastric digestion of lactoferrin/curcumin nanoparticles in the realistic gastric model (RGM). For this purpose, the INFOGEST standard semi-dynamic digestion protocol was used. The nanosystems were characterized in terms of hydrodynamic size, size distribution, polydispersity index (PdI), and zeta potential using dynamic light scattering (DLS), before and during the digestion process. Confocal laser scanning microscopy (CLSM) was also used to examine particle aggregation. In addition, the release of curcumin was evaluated spectroscopically and the intrinsic fluorescence of lactoferrin was measured throughout the digestion process. The protein hydrolysis was also determined by UV-VIS-SWNIR spectroscopy to estimate, in real-time, the presence of free NH2 groups during gastric digestion. It was possible to observe that lactoferrin/curcumin nanoparticles were destabilized during the dynamic digestion process. It was also possible to conclude that low sample volumes can pose a major challenge in the application of dynamic in vitro digestion models.

Plasma polymerized nanoparticles are a safe platform for direct delivery of growth factor therapy to the injured heart.

Introduction: Heart failure due to myocardial infarction is a progressive and debilitating condition, affecting millions worldwide. Novel treatment strategies are desperately needed to minimise cardiomyocyte damage after myocardial infarction and to promote repair and regeneration of the injured heart muscle. Plasma polymerized nanoparticles (PPN) are a new class of nanocarriers which allow for a facile, one-step functionalization with molecular cargo. Methods: Here, we conjugated platelet-derived growth factor AB (PDGF-AB) to PPN, engineering a stable nano-formulation, as demonstrated by optimal hydrodynamic parameters, including hydrodynamic size distribution, polydisperse index (PDI) and zeta potential, and further demonstrated safety and bioactivity in vitro and in vivo. We delivered PPN-PDGF-AB to human cardiac cells and directly to the injured rodent heart. Results: We found no evidence of cytotoxicity after delivery of PPN or PPN-PDGFAB to cardiomyocytes in vitro, as determined through viability and mitochondrial membrane potential assays. We then measured contractile amplitude of human stem cell derived cardiomyocytes and found no detrimental effect of PPN on cardiomyocyte contractility. We also confirmed that PDGF-AB remains functional when bound to PPN, with PDGF receptor alpha positive human coronary artery vascular smooth muscle cells and cardiac fibroblasts demonstrating migratory and phenotypic responses to PPN-PDGF-AB in the same manner as to unbound PDGF-AB. In our rodent model of PPN-PDGF-AB treatment after myocardial infarction, we found a modest improvement in cardiac function in PPN-PDGF-AB treated hearts compared to those treated with PPN, although this was not accompanied by changes in infarct scar size, scar composition, or border zone vessel density. Discussion: These results demonstrate safety and feasibility of the PPN platform for delivery of therapeutics directly to the myocardium. Future work will optimize PPN-PDGF-AB formulations for systemic delivery, including effective dosage and timing to enhance efficacy and bioavailability, and ultimately improve the therapeutic benefits of PDGF-AB in the treatment of heart failure cause by myocardial infarction.

Analysis of Silicon Quantum Dots and Serum Proteins Interactions Using Asymmetrical Flow Field-Flow Fractionation.

Semiconductor nanocrystals or quantum dots (QDs) have gained significant attention in biomedical research as versatile probes for imaging, sensing, and therapies. However, the interactions between proteins and QDs, which are crucial for their use in biological applications, are not yet fully understood. Asymmetric flow field-flow fractionation (AF4) is a promising method for analyzing the interactions of proteins with QDs. This technique uses a combination of hydrodynamic and centrifugal forces to separate and fractionate particles based on their size and shape. By coupling AF4 with other techniques, such as fluorescence spectroscopy and multi-angle light scattering, it is possible to determine the binding affinity and stoichiometry of protein-QD interactions. Herein, this approach has been utilized to determine the interaction between fetal bovine serum (FBS) and silicon quantum dots (SiQDs). Unlike metal-containing conventional QDs, SiQDs are highly biocompatible and photostable in nature, making them attractive for a wide range of biomedical applications. In this study, AF4 has provided crucial information on the size and shape of the FBS/SiQD complexes, their elution profile, and their interaction with serum components in real time. The differential scanning microcalorimetric technique has also been employed to monitor the thermodynamic behavior of proteins in the presence of SiQDs. We have investigated their binding mechanisms by incubating them at temperatures below and above the protein denaturation. This study yields various significant characteristics such as their hydrodynamic radius, size distribution, and conformational behavior. The compositions of SiQD and FBS influence the size distribution of their bioconjugates; the size increases by intensifying the concentration of FBS, with their hydrodynamic radii ranging between 150 and 300 nm. The results signify that in the alliance of SiQDs to the system, there is an augmentation of the denaturation point of the proteins and hence their thermal stability, providing a more comprehensive understanding of the interactions between FBS and QDs.

Green synthesis of silver nanoparticles using paper wasp‘s hydrolysate with antibacterial activity

The last two decades revealed tremendous interest in nanoparticles synthesized via green synthesis and its wide spectra application first of all as effective antimicrobial agents. This research aims to conduct a green synthesis of silver nanoparticles (AgNPs) stabilized by amino acids and oligoproteins. Various conditions (conventional heat treatment, microwave irradiation, and UV-light irradiation pH and concentration of reagents) on yield and size of AgNPs during the synthesis were tested. Alkaline hydrolysate of paper wasp‘s nest was characterized using amino acid analysis, zeta potential, and SDS gel electrophoresis. The protein hydrolysate molecular weight distribution for AgNPs synthesis was predominantly in the range of 0.5 to 10 kDa. The kinetics of the particle synthesis was monitored via intensity change of the AgNPs’ Surface Plasmon resonance UV–V is spectroscopy. The increase of the ionic strength of the AgNP suspension by the addition of salts NaCl and KBr led to aggregation of AgNPs. Zeta potential and hydrodynamic particle size distribution of AgNPs were −46 ± 25 mV and 137 ± 73 nm, respectively. Surface Plasmon resonance peak indicates the dominance of particle size in the range 50–70 nm due to the pH, which influenced on antimicrobial activity. MIC of 7.5 μM AgNPs in combination with 50 μM of benzalkonium chloride against the E. coli strain was (6.9xE8 particles/L) and 25 μM of benzalkonium chloride, while MIC of 73 μM of AgNPs (3.45xE8 particles/L) against Staphylococcus aureus was detected. The antimicrobial effect of the AgNPs suspension irradiated by light spectra at 425 and 630 nm were studied. AgNPs obtained using microwave radiation at a neutral medium were stable for at least 3 months at 4 °C.

Sustainable fabrication of hybrid silver-copper nanocomposites (Ag‐CuO NCs) using Ocimum americanum L. as an effective regime against antibacterial, anticancer, photocatalytic dye degradation and microalgae toxicity

In this study, a sustainable fabrication of hybrid silver-copper oxide nanocomposites (Ag–CuO NCs) was accomplished utilizing Ocimum americanum L. by one pot green chemistry method. The multifarious biological and environmental applications of the green fabricated Ag–CuO NCs were evaluated through their antibacterial, anticancer, dye degradation, and microalgae growth inhibition activities. The morphological features of the surface functionalized hybrid Ag–CuO NCs were confirmed by FE-SEM and HR-TEM techniques. The surface plasmon resonance λmax peak appeared at 441.56 nm. The average hydrodynamic size distribution of synthesized nanocomposite was 69.80 nm. Zeta potential analysis of Ag–CuO NCs confirmed its remarkable stability at −21.5 mV. XRD and XPS techniques validated the crystalline structure and electron binding affinity of NCs, respectively. The Ag–CuO NCs demonstrated excellent inhibitory activity against Vibrio cholerae (19.93 ± 0.29 mm) at 100 μg/mL. Anticancer efficacy of Ag–CuO NCs was investigated against the A549 lung cancer cell line, and Ag–CuO NCs exhibited outstanding antiproliferative activity with a low IC50 of 2.8 ± 0.05 μg/mL. Furthermore, staining and comet assays substantiated that the Ag–CuO NCs hindered the progression of the A549 cells and induced apoptosis as a result of cell cycle arrest at the G0/G1 phase. Concerning the environmental applications, the Ag–CuO NCs displayed efficient photocatalytic activity against eosin yellow degradation up to 80.94% under sunlight irradiation. Microalgae can be used as an early bio-indicator/prediction of environmental contaminants and toxic substances. The treatment of the Ag–CuO NCs on the growth of marine microalgae Tetraselmis suecica demonstrated the dose and time-dependent growth reduction and variations in the chlorophyll content. Therefore, the efficient multifunctional properties of hybrid Ag–CuO NCs could be exploited as a regime against infective diseases and cancer. Further, the findings of our investigation witness the remarkable scope and potency of Ag–CuO NCs for environmental applications.

Properties and biocompatibility of colloid cadmium sulfide nanoparticles

The properties and cytotoxicity of aqueous colloidal solutions of cadmium sulfide CdS nanoparticles obtained by chemical condensation were explored. Dynamic light scattering and optical spectroscopy were used to study the hydrodynamic diameter, size distribution, zeta-potential and optical properties of the CdS nanoparticles in solution. The cytotoxicity of colloidal CdS nanoparticles at different concentrations was assessed on cultures of human dermal fibroblasts and the cancer HeLa line.

Enhanced Targeted Delivery of Minocycline via Transferrin Conjugated Albumin Nanoparticle Improves Neuroprotection in a Blast Traumatic Brain Injury Model.

Traumatic brain injury (TBI) is a major source of death and disability worldwide as a result of motor vehicle accidents, falls, attacks and bomb explosions. Currently, there are no FDA-approved drugs to treat TBI patients predominantly because of a lack of appropriate methods to deliver drugs to the brain for therapeutic effect. Existing clinical and pre-clinical studies have shown that minocycline's neuroprotective effects either through high plasma protein binding or an increased dosage requirement have resulted in neurotoxicity. In this study, we focus on the formulation, characterization, in vivo biodistribution, behavioral improvements, neuroprotective effect and toxicity of transferrin receptor-targeted (tf) conjugated minocycline loaded albumin nanoparticles in a blast-induced TBI model. A novel tf conjugated minocycline encapsulated albumin nanoparticle was developed, characterized and quantified using a validated HPLC method as well as other various analytical methods. The results of the nanoformulation showed small, narrow hydrodynamic size distributions, with high entrapment, loading efficiencies and sustained release profiles. Furthermore, the nanoparticle administered at minimal doses in a rat model of blast TBI was able to cross the blood-brain barrier, enhanced nanoparticle accumulation in the brain, improved behavioral outcomes, neuroprotection, and reduced toxicity compared to free minocycline. Hence, tf conjugated minocycline loaded nanoparticle elicits a neuroprotective effect and can thus offer a potential therapeutic effect.

Asphaltenes: Aggregates in Terms of A1 and A2 or Island and Archipielago Structures.

In this work several issues related to asphaltenes and asphaltene aggregates such as isolation of real asphaltene molecules and comparison of these with average structures obtained using regular analytics laboratory techniques are presented. Several molecular organic models were used to simulate asphaltene in solution and aggregates formation in the two solvents toluene and THF employed. The results, obtained from simulation calculations using molecular dynamics were compared with experimental chromatography results obtained using the micro gel permeation chromatography (μGPC), inductively coupled plasma (ICP) mass spectra (MS) combined technique (GPC ICP MS for short). In this case reasonable hydrodynamic ratios and size distribution were obtained for asphaltenes and their corresponding subfractions A1 and subfraction A2. Comparison between experimental sample profiles, transmission of electron microscopy (TEM) data, and molecular dynamics allows for estimation of hydrodynamic ratios of around 8 nm. Highly aromatic and island type molecular model A30 and continental type molecular model A40 were employed in the molecular dynamics to built colloids. In this case open-like colloids (A40) and compact-like colloids A30 were obtained. Subjects such as trapped compounds (TC), metallic porphyrins, and colloidal dipole moments were also studied. Studies of the adsorption behavior of asphaltenes on several macroscopic and nanoscopic surfaces are presented and show the tendency of the asphaltene to adsorb in aggregate form.

Determining the resolution of a tracer for magnetic particle imaging by means of magnetic particle spectroscopy.

Magnetic particle imaging (MPI) is an imaging modality to quantitatively determine the three-dimensional distribution of magnetic nanoparticles (MNPs) administered as a tracer into a biological system. Magnetic particle spectroscopy (MPS) is the zero-dimensional MPI counterpart without spatial coding but with much higher sensitivity. Generally, MPS is employed to qualitatively evaluate the MPI capability of tracer systems from the measured specific harmonic spectra. Here, we investigated the correlation of three characteristic MPS parameters with the achievable MPI resolution from a recently introduced procedure based on a two-voxel-analysis of data taken from the system function acquisition that is mandatory in Lissajous scanning MPI. We evaluated nine different tracer systems and determined their MPI capability and resolution from MPS measurements and compared the results with MPI phantom measurements.

Pre-emergent bioherbicide potential of Schinus terebinthifolia Raddi essential oil nanoemulsion for Urochloabrizantha

Essential oils are natural products capable of being used as novel agrochemical products. In order to fill knowledge gaps, this work evaluates the bioherbicidal potential of Schinus terebinthifolia fruit essential oil (EOsST) emulsions on germination parameters of Lactuca sativa and Urochloa brizantha seeds. The hydrodynamic size distribution of the emulsions was evaluated by dynamic light scattering (DLS), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). Also, the chemical composition of EOsST was performed by gas chromatography coupled to mass spectrometry (GC-MS). DLS results suggest nanoemulsion (NE) particle sizes smaller than 735 nm and SEM images showed spherical and cuboid shapes. FTIR spectra indicate peaks at 1640 cm−1 and 1440 cm−1, referring to the benzene ring, and the C–H stretching band from 2970 cm−1–2870 cm−1 indicates the interaction between EOsST and TX-100. GC-MS reveals that the major compounds present on EOsST were α-pinene, germacrene-D, and β-pinene. U. brizantha seed germination was reduced at doses >2 mg mL−1 and completely inhibited at 32 mg mL−1. For L. sativa there was a reduction in germination which was dose-dependent and no dose caused total inhibition. Moreover, a decrease in photosynthetic pigments, flavonoids, phenolics, and total tannins was observed. Enzyme activity was altered, with reduction to catalase and peroxidase.

Simultaneous estimation of magnetic moment and Brownian relaxation time distributions of magnetic nanoparticles based on magnetic particle spectroscopy for biosensing application.

Magnetic nanoparticles (MNPs) exhibit unique physicochemical characteristics owing to their comparable dimensions with important biological substances, high surface-to-volume ratios, size-dependent magnetic properties, and temperature sensitivity. In this study, we present a novel method for simultaneously estimating the magnetic moment and Brownian relaxation time distribution of MNPs based on AC magnetization harmonics. We provide a detailed description of the theoretical framework and experimental procedures. The dynamics of MNP magnetization are described using the Fokker-Planck equation, and a matrix equation is established to connect the magnetic moment, Brownian relaxation time, and magnetization harmonics. By employing a non-negative linear least squares algorithm with constraints, the magnetic moment and Brownian relaxation time distributions are inversed, which are then converted into the distributions of core sizes and hydrodynamic sizes. Finally, the estimated core size distribution reconstructed from M-H curves is consistent with the hydrodynamic size distribution measured by dynamic light scattering. This method is particularly useful for facilitating quantitative magnetic immunoassays.

Amine-assisted catechol-based nanocoating on ultrasmall iron oxide nanoparticles for high-resolution T1 angiography.

Surface engineered iron oxide nanoparticles (IONPs) with catecholic ligands have been investigated as alternative T1 contrast agents. However, complex oxidative chemistry of catechol during IONP ligand exchange causes surface etching, heterogeneous hydrodynamic size distribution, and low colloidal stability because of Fe3+ mediated ligand oxidation. Herein, we report highly stable and compact (∼10 nm) Fe3+ rich ultrasmall IONPs functionalized with a multidentate catechol-based polyethylene glycol polymer ligand through amine-assisted catecholic nanocoating. The IONPs exhibit excellent stability over a broad range of pHs and low nonspecific binding in vitro. We also demonstrate that the resultant NPs have a long circulation time (∼80 min), enabling high resolution T1 magnetic resonance angiography in vivo. These results suggest that the amine assisted catechol-based nanocoating opens a new potential of metal oxide NPs to take a step forward in exquisite bio-application fields.

Targeting the Structural Integrity of Extracellular Vesicles via Nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analysis (nES GEMMA).

Extracellular vesicles (EVs) are in the scientific spotlight due to their potential application in the medical field, ranging from medical diagnosis to therapy. These applications rely on EV stability during isolation and purification—ideally, these steps should not impact vesicle integrity. In this context, we investigated EV stability and particle numbers via nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA) and nanoparticle tracking analysis (NTA). In nES GEMMA, native, surface-dry analytes are separated in the gas-phase according to the particle size. Besides information on size and particle heterogeneity, particle number concentrations are obtained in accordance with recommendations of the European Commission for nanoparticle characterization (2011/696/EU, 18 October 2011). Likewise, and in contrast to NTA, nES GEMMA enables detection of co-purified proteins. On the other hand, NTA, yielding data on hydrodynamic size distributions, is able to relate particle concentrations, omitting electrolyte exchange (and resulting EV loss), which is prerequisite for nES GEMMA. Focusing on EVs of different origin, we compared vesicles concentrations and stability, especially after electrolyte exchange and size exclusion chromatography (SEC). Co-isolated proteins were detected in most samples, and the vesicle amount varied in dependence on the EV source. We found that depletion of co-purified proteins was achievable via SEC, but was associated with a loss of EVs and—most importantly—with decreased vesicle stability, as detected via a reduced nES GEMMA measurement repeatability. Ultimately, we propose the repeatability of nES GEMMA to yield information on EV stability, and, as a result, we propose that nES GEMMA can yield additional valuable information in EV research.