Absolute protein quantification based on calibrated particle counting using electrospray-differential mobility analysis

The traceability of in vitro diagnostics or drug products is based on the accurate quantification of proteins. In this study, we developed an absolute quantification approach for proteins. This method is based on calibrated particle counting using electrospray-differential mobility analysis (ES-DMA) coupled with a condensation particle counter (CPC). The absolute concentration of proteins was quantified with the observed protein particle number measured with ES-DMA-CPC, and the detection efficiency was determined by calibrators. The measurement performance and quantitative level were verified using two certificated reference materials, BSA and NIMCmAb. The linear regression fit for the detection efficiency values of three reference materials and one highly purified protein (myoglobin, BSA, NIMCmAb and fibrinogen) indicated that the detection efficiency and the particle size distribution of these proteins exhibited a linear relationship. Moreover, to explore the suitability of the detection efficiency-particle size curve for protein quantification, the concentrations of three typical proteinaceous particles, including two high molecular weight proteins (NIST reference material 8671 and D-dimer) and one protein complex (glutathione S-transferase dimer), were determined. This work suggests that this calibrated particle counting method is an efficient approach for nondestructive, rapid and accurate quantification of proteins, especially for measuring proteinaceous particles with tremendous size and without reference standards.

Particle Size and Concentration Measurement Using the Spectradyne nCS1 Instrument

This protocol describes the use of the Spectradyne nCS1 instrument to measure the particles per mL concentration and size of nanoparticles. The Spectradyne nCS1 is a particle-analyzing instrument that uses microfluidic resistive pulse sensing, rather than optical measurements, to determine the size and concentration of samples. The size and concentration of a sample are determined by measuring the changes in voltage as particles travel through a nano-constriction in the microfluidic cartridge. This method also has the advantage over optical techniques in that measurements are not dependent on the type of material being measured (e.g., refractive index of the sample itself is not needed for accurate analysis), and only microliters (typically 5 μL) of a sample are needed for analysis.

Easy and accessible way to calibrate a fluorescence microscope and to create a microplastic identification key

We present here a technique for setting up detection limits on any fluorescent microscope in conjunction with the fluorophore Nile Red for microplastic identification. Our method also describes a rigorous morphology-specific identification key for microplastics to reduce subjectivity between researchers. The detection limits were established for nine common polymer types and five natural substrates which could result in false-positive signals when using Nile Red for microplastic identification. This method was then applied to real freshwater samples and identified particles were validated with micro-FTIR or Raman spectroscopy. This approach may reduce subjectivity in microplastic identification and counting and enhances transparency, repeatability and harmonization within microplastic research community.•Instructions for calibration of detection limits for microplastics on fluorescence microscope systems described•Microplastic identification key developed and tested to reduce false positive detection•Lower subjectivity for microplastic identification obtained using the detection limits & identification key.

Fate and transport of strontium in groundwater from a layered sedimentary aquifer system

In this article, strontium distribution in sedimentary coastal aquifers of Eastern India was studied and its association with groundwater particles has been ascertained using hydrochemical and morphological tools. Groundwater contains Sr²⁺ in the range of 0.08-4.0 mg/L with higher concentrations in Cretaceous formation. The particle number in groundwater varies from 4.5 × 10⁵ to 3.3 × 10⁶ per liter and follows the power law distribution with respect to the particle diameter. The calculated β values (2.54 and 4.03) signify the abundance of smaller particles over larger ones. The particle concentration of size range 0.45-8 μm is found to be 0.64-2.6 mg/L. Elemental data of groundwater particles clearly suggest their origin from the host rock minerals. Zeta potential data indicates diverse nature of colloids suggesting prevalence of both positive and negative charged species in the groundwater. The hydrochemical interpretation along with speciation studies infers that high Sr²⁺ in groundwater is a result of incongruent dissolution of carbonate minerals and the dissolved Sr²⁺ partitions into both dissociated and un-dissociated forms. Based on the Sr²⁺/Ca²⁺ ratio and mineral saturation indices, it can be inferred that the Sr²⁺ is preferentially associated with colloids over large particles and the migration takes place through sorption of Sr²⁺ onto clay-bound (extrinsic) colloids in groundwater. This study describes the mechanism of strontium release into groundwater and provides insights into the role of groundwater particles in controlling the strontium migration to deep aquifers.

Polydopamine nanoparticle-mediated, click chemistry triggered, microparticle-counting immunosensor for the sensitive detection of ochratoxin A

A rapid and accurate detection method is needed for the quantitation of ochratoxin A in agricultural products due to its high toxicity. A microparticle-counting immunosensor based on polydopamine nanoparticle-mediated click chemistry was established for the highly-sensitive detection of ochratoxin A. Polydopamine nanoparticles with good biocompatibility and a strong metal-chelating ability were synthesized and conjugated with the antibody. The Coupled compounds were then used as an immune carrier to change the Cu²⁺ concentration via an immuno-reaction. Some of the remaining Cu²⁺ ions were reduced to Cu⁺ ions, which caused azide-polystyrene microspheres and alkyne-polystyrene microspheres to aggregate via a Cu⁺ ion-mediated click reaction. Particle counting was used to distinguish changes in the sizes of the polystyrene microspheres from dispersed to aggregated to detect ochratoxin A. It showed a wide linear detection range of 0.5-800 ng/mL, and a detection limit of 0.2 ng/mL. This assay provides an attractive analytical tool for the accurate detection of trace targets in complex samples.

Quantitative analysis of fine dust particles on moss surfaces under laboratory conditions using the example of Brachythecium rutabulum

The identification of a model organism for investigations of fine dust deposits on moss leaflets was presented. An optical method with SEM enabled the quantitative detection of fine dust particles in two orders of magnitude. Selection criteria were developed with which further moss species can be identified in order to quantify the number of fine dust particles on moss surfaces using the presented method. Among the five moss species examined, B. rutabulum had proven to be the most suitable model organism for the method presented here. The number of fine dust particles on the moss surface of B. rutabulum was documented during 4 weeks of cultivation in the laboratory using SEM images and a counting method. The fine dust particles were recorded in the order of 10 μm-0.3 μm, divided into two size classes and counted. Under laboratory conditions, the number of particles of the fine fraction 2.4 μm-0.3 μm decreased significantly.

The importance of nanoparticle physicochemical characterization for immunology research: What we learned and what we still need to understand

Physicochemical characterization of nanoparticles intended for immunology research is important as it helps explain the observed immunological effects. More importantly, it relates the physicochemical properties with the immunological properties to draw meaningful conclusions. There are many physicochemical parameters, with each having numerous analytical techniques and instrumentation to measure them. Thus, where to begin can be challenging even for the experienced scientist. This paper aims to provide guidance to the immunology scientist on how best to characterize their nanoparticles. A step-by-step guide for the physicochemical characterization of liposomal formulations, based on the FDA's guidance for industry for Liposome Drug Products, is provided. Eight critical quality attributes have been identified and for each, the methodology and the physicochemical questions one should consider are discussed. This chapter also addresses common physicochemical characterization mistakes and concludes with a perspective on the type of measurements needed to address current physicochemical characterization gaps and challenges.

Filtering efficiency measurement of respirators by laser-based particle counting method

Respirators are one of the most useful personal protective equipment which can effectively limit the spreading of coronavirus (COVID-19). There are a worldwide shortage of respirators, melt-blown non-woven fabrics, and respirator testing possibilities. An easy and fast filtering efficiency measurement method was developed for testing the filtering materials of respirators. It works with a laser-based particle counting method, and it can determine two types of filtering efficiencies: Particle Filtering Efficiency (PFE) at given particle sizes and Concentration Filtering Efficiency (CFE) in the case of different aerosols. The measurement method was validated with different aerosol concentrations and with etalon respirators. Considerable advantages of our measurement method are simplicity, availability, and the relatively low price compared to the flame-photometer based methods. The ability of the measurement method was tested on ten different types of Chinese KN95 respirators. The quality of these respirators differs much, only two from ten reached 95% filtering efficiency.

Verification of UriSed 3 PRO automated urine microscope in regional laboratory environment

BACKGROUND AND AIMS

Ten UriSed 3 PRO automated microscopes (77 Elektronika, Hungary) were verified for nine HUSLAB laboratories with 160 000 annual urine samples.

MATERIALS AND METHODS

Particle counting of the primary UriSed 3 PRO instrument (77 Elektronika, Hungary) was verified against reference visual microscopy with 463 urine specimens, and against urine culture on chromogenic agar plates with parallel 396 specimens. Nine secondary instruments were compared pairwise with the primary instrument.

RESULTS

Relative imprecisions compared to Poisson distribution, R(CV), were estimated to be 1.0 for white blood cell (WBC) and 1.5 for red blood cell (RBC) counts, respectively. Spearman's correlations against visual microscopy were r_S = 0.94 for WBC, r_S = 0.87 for RBC, and r_S = 0.82 for squamous epithelial cell (SEC) counts. Agreement with visual microscopy (Cohen's weighted kappa) was 0.94 for WBC, 0.89 for RBC, 0.88 for SEC, 0.59 for combined casts, and 0.49 for non-squamous epithelial cells (NEC). Bacteria were detected with a sensitivity of 90% and specificity of 39 against culture at 10⁷ CFB/L (10⁴ CFU/mL). Created flagging limits allowed automated reporting for 70-75% of patient results.

CONCLUSIONS

UriSed 3 PRO instruments were adopted into routine use after acceptance of the verification.

Characterization of Positively Charged Lipid Shell Microbubbles with Tunable Resistive Pulse Sensing (TRPS) Method: A Technical Note

Microbubbles are polydisperse microparticles. Their size distribution cannot be accurately measured from the current methods used, such as optical microscopy, electrical sensing or light scattering. Indeed, these techniques present some limitations when applied to microbubbles, which prompted us to investigate the use of an alternative technique: tunable resistive pulse sensing (TRPS). This technique is based on the principle of the Coulter counter with the advantage of being more flexible compared to other methods using this principle, since the flow rate, the potential difference and the pore size can be modulated. The main limitation of TRPS is that more than one size of nanopore membrane is required to obtain the full size distribution of polydisperse microparticles. To evaluate this technique, the concentration and the size distribution of positively charged microbubbles were studied using TRPS and compared to data obtained using optical microscopy. We describe herein the parameters required for the accurate measurement of microbubble concentration and size distribution by TRPS and present a statistical comparison of the data obtained by TRPS and optical microscopy.

A multidisciplinary approach to the study of cultural heritage environments: Experience at the Palatina Library in Parma

The aim of this paper is to describe a multidisciplinary approach including biological and particle monitoring, and microclimate analysis associated with the application of the Computational Fluid Dynamic (CFD). This approach was applied at the Palatina historical library in Parma. Monitoring was performed both in July and in December, in the absence of visitors and operators. Air microbial monitoring was performed with active and passive methods. Airborne particles with a diameter of ≥0.3, ≥0.5, ≥1 and ≥5 μm/m3, were counted by a laser particle counter. The surface contamination of shelves and manuscripts was assessed with nitrocellulose membranes. A spore trap sampler was used to identify both viable and non-viable fungal spores by optical microscope. Microbiological contaminants were analyzed through cultural and molecular biology techniques. Microclimatic parameters were also recorded. An infrared thermal camera provided information on the surface temperature of the different building materials, objects and components. Transient simulation models, for coupled heat and mass-moisture transfer, taking into account archivist and general public movements, combined with the related sensible and latent heat released into the environment, were carried out applying the CFD-FE (Finite Elements) method. Simulations of particle tracing were carried out. A wide variability in environmental microbial contamination, both for air and surfaces, was observed. Cladosporium spp., Alternaria spp., Aspergillus spp., and Penicillium spp. were the most frequently found microfungi. Bacteria such as Streptomyces spp., Bacillus spp., Sphingomonas spp., and Pseudoclavibacter as well as unculturable colonies were characterized by molecular investigation. CFD simulation results obtained were consistent with the experimental data on microclimatic conditions. The tracing and distribution of particles showed the different slice planes of diffusion mostly influenced by the convective airflow. This interdisciplinary research represents a contribution towards the definition of standardized methods for assessing the biological and microclimatic quality of indoor cultural heritage environments.

Methods for counting particles in microfluidic applications

Microfluidic particle counters are important tools in biomedical diagnostic applications such as flow cytometry analysis. Major methods of counting particles in microfluidic devices are reviewed in this paper. The microfluidic resistive pulse sensor advances in sensitivity over the traditional Coulter counter by improving signal amplification and noise reduction techniques. Nanopore-based methods are used for single DNA molecule analysis and the capacitance counter is useful in liquids of low electrical conductivity and in sensing the changes of cell contents. Light-scattering and light-blocking counters are better for detecting larger particles or concentrated particles. Methods of using fluorescence detection have the capability for differentiating particles of similar sizes but different types that are labeled with different fluorescent dyes. The micro particle image velocimetry method has also been used for detecting and analyzing particles in a flow field. The general limitation of microfluidic particle counters is the low throughput which needs to be improved in the future. The integration of two or more existing microfluidic particle counting techniques is required for many practical on-chip applications.