Quantitative assessment of protein adsorption on microparticles with particle mass spectrometry

Accurate and High-Resolution Particle Mass Measurement Using a Peak Filtering Algorithm

Charge detection quadrupole ion trap mass spectrometry (CD-QIT MS) is an effective way of achieving the mass analysis of microparticles with ultrahigh mass. However, its mass accuracy and resolution are still poor. To enhance the performance of CD-QIT MS, the resolution Rpeak of each peak in the mass spectra resulting from an individual particle was assessed, and a peak filtering algorithm that can filter out particle adducts and clusters with a lower Rpeak was proposed. By using this strategy, more accurate mass information about the analyzed particles could be obtained, and the mass resolution of CD-QIT MS was improved by nearly 2-fold, which was demonstrated by using the polystyrene (PS) particle size standards and red blood cells (RBCs). Benefiting from these advantages of the peak filtering algorithm, the baseline separation and relative quantification of 3 and 4 μm PS particles were achieved. To prove the application value of this algorithm in a biological system, the mass of yeast cells harvested at different times was measured, and it was found that the mixed unbudded and budded yeast cells, which otherwise would not be differentiable, were distinguished and quantified with the algorithm.

CO2-Responsive Spherical Polyelectrolyte Brush with Multi-Stimulation for Reversible Protein Immobilization and Release

Multi-responsive materials have received extensive interest in many areas due to their smart characteristics. This paper presents rationally designed multi-responsive spherical polyelectolyte brushes composed of a solid polystyrene (PS) core and a poly (2-(dimethylamino) ethyl methacrylate) (PDMAEMA) shell synthesized by photoemulsion polymerization. Based on dynamic light scattering, Zeta potential, turbidity measurements, isothermal titration calorimetry, and UV-vis spectroscopy, PS-PDMAEMA works as a good potential adsorbent for bovine serum albumin (BSA) for which the maximum adsorption capability could reach up to 5190mg g−1. Moreover, the immobilization and release of protein on the polymer brush could be adjusted with different triggers, including the pH, ionic strength, and temperature. Furthermore, the green gas triggers, CO2 and N2, could be employed in the BSA@ PS-PDMAEMA system by easily bubbling over many cycles without any salt accumulation. The main reason for the observed actions is the brushes could be switched alternately between extended and collapsed states with different stimulations. Upon comparing the circular dichroism spectra of original and released BSA after many cycles of adsorption and release, it’s clear that the protein can retain its initial biological activity after release from the PS-PDMAEMA. This work provides an effective and green way to immobilize and release proteins in biotechnology.

A sensitive in vitro performance assay reveals the in vivo drug release mechanisms of long-acting medroxyprogesterone acetate microparticles

Today, a growing number of subcutaneously administered depot formulations enable continuous delivery of poorly soluble compounds over a longer time period. The modified liberation is considered to be a rate-limiting step in drug absorption and thus impacts therapeutic efficacy and product safety. In the present approach, a mechanism-based pharmacokinetic model of the commercial microparticle formulation depo-subQ provera 104™ (Sauter mean diameter of 5.08 ± 1.63 µm) was established. The model was verified using human pharmacokinetic data from three different clinical trials. Further, the effects of drug release, injection site and patient population on the pharmacokinetic profile were investigated. For this purpose, the drug release was assessed using the novel dispersion releaser technology, whereby a biorelevant medium reflecting major characteristics of the subcutaneous tissue (including ion background, buffer capacity and protein concentration) was used. The established model provided an effective prediction of the key pharmacokinetic parameters, including C_max, T_max and AUC_all. Only in presence of 55% of fetal bovine serum (using a novel simulated subcutaneous interstitial fluid), the release assay was capable to discriminate between microparticles before and after storage.

Mass, Size, and Density Measurements of Microparticles in a Quadrupole Ion Trap

The physical properties of microparticles, such as mass, size, and density, are critical for their functions. The comprehensive characterization of these physical parameters, however, remains a fundamental challenge. Here, we developed a particle mass spectrometry (PMS) methodology for determining the mass, size, and density of microparticles simultaneously. The collisional cross-section (CCS) and mass spectrometry (MS) measurements were performed in a single quadrupole ion trap (QIT), and the two modes can be switched easily by tuning the electric and gas hydrodynamic fields of the QIT. The feasibility of the method was demonstrated through a series of monodispersed polystyrene (PS) and silica (SiO₂) particle standards. The SiO₂/polypyrrole core-shell particles were also successfully characterized, and the measured results were verified by using conventional methods.

Quantitation of nonspecific protein adsorption at solid–liquid interfaces for single-cell proteomics

Protein nonspecific adsorption that occurred at the solid–liquid interface has been subjected to intense physical and chemical characterizations due to its crucial role in a wide range of applications, including food and pharmaceutical industries, medical implants, biosensing, and so on. Protein-adsorption caused sample loss has largely hindered the studies of single-cell proteomics; the prevention of such loss requires the understanding of protein–surface adsorption at the proteome level, in which the competitive adsorption of thousands and millions of proteins with vast dynamic range occurs. To this end, we feel the necessity to review current methodologies on their potentials to characterize — more specifically to quantify — the proteome-wide adsorption. We hope this effort can help advancing single-cell proteomics and trace proteomics.

Single-molecule mass spectrometry

In single-molecule mass spectrometry, the mass of each ion is measured individually; making it suitable for the analysis of very large, heterogeneous objects that cannot be analyzed by conventional means. A range of single-molecule mass spectrometry techniques has been developed, including time-of-flight with cryogenic detectors, a quadrupole ion trap with optical detection, single-molecule Fourier transform ion cyclotron resonance, charge detection mass spectrometry, quadrupole ion traps coupled to charge detector plates, and nanomechanical oscillators. In addition to providing information on mass and heterogeneity, these techniques have been used to study impact craters from cosmic dust, monitor the assembly of viruses, elucidate the fluorescence dynamics of quantum dots, and much more. This review focuses on the merits of each of these technologies, their limitations, and their applications. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 36:715-733, 2017.

Protein adsorption onto nanomaterials for the development of biosensors and analytical devices: a review

An important consideration for the development of biosensors is the adsorption of the biorecognition element to the surface of a substrate. As the first step in the immobilization process, adsorption affects most immobilization routes and much attention is given into the research of this process to maximize the overall activity of the biosensor. The use of nanomaterials, specifically nanoparticles and nanostructured films, offers advantageous properties that can be fine-tuned to maximize interactions with specific proteins to maximize activity, minimize structural changes, and enhance the catalytic step. In the biosensor field, protein-nanomaterial interactions are an emerging trend that span across many disciplines. This review addresses recent publications about the proteins most frequently used, their most relevant characteristics, and the conditions required to adsorb them to nanomaterials. When relevant and available, subsequent analytical figures of merits are discussed for selected biosensors. The general trend amongst the research papers allows concluding that the use of nanomaterials has already provided significant improvements in the analytical performance of many biosensors and that this research field will continue to grow.

Measuring masses of large biomolecules and bioparticles using mass spectrometric techniques

Mass spectrometric techniques can measure the masses and fragments of large biomolecules and bioparticles.