Browsing by Subject "Microparticles"

Now showing 1 - 6 of 6

Open Access
Classification of dielectric microparticles by microwave impedance cytometry
(Cold Spring Harbor Laboratory, 2022-09-28) Hanay, M. Selim; Sarı, Burak; Tefek, Uzay
AbstractCoulter counters and impedance cytometry are commonly used for counting microscopic objects, such as cells and microparticles flowing in a liquid, as well as to obtain their size distribution. However, the ability of these techniques to provide simultaneous material information — via dielectric permittivity measurements — has been limited so far. The challenge stems from the fact that the signals generated by microparticles of identical size, but different material composition, are close to each other. The similarity in impedance signals arises because the material-dependent factor is determined mainly by the volume of aqueous solution displaced by the microparticles, rather than the microparticles themselves. To differentiate between materially distinct particles with similar geometry and size, another measurement mode needs to be implemented. Here, we describe a new microfluidics-based sensor that provides material classification between microparticles with similar sizes by integrating impedance cytometry with microwave resonator sensors on the same chip. While low-frequency impedance cytometry provides the geometric size of particles, the microwave sensor operating at three orders-of-magnitude higher frequency provides their electrical size. By combining these two measurements, the Clausius-Mossotti factors of microparticles can be calculated to serve as a differentiation parameter. In addition to distinguishing dielectric materials from cells and metals, we classified two different dielectric microparticles with similar sizes and electrical characteristics: polystyrene and soda lime glass, with 94% identification accuracy. The proposed technique can serve as an automated monitoring system for quality control of manufactured microparticles and facilitate environmental microplastic screening.
Open Access
Contribution of plasma microparticles to the clinical manifestation of allergic diseases
(Turkish Society of Immunology, 2012-04) Kahraman, Tamer; Erkoçoğlu, M.; Azkur, D.; Kocabaş, C. N.; Gürsel, İhsan
Microparticles (MPs) are nanovesicles secreted from wide variety of cells. They have role in cellular communications in addition to their physiological roles in several diseases. In this study, we investigated roles of MPs in allergic diseases. Method Peripheral blood from 43 asthma, 15 atopic dermatitis and 13 healthy subjects were collected. MPs were isolated via differential centrifugation and subjected to Annexin-V staining together with different cell specific surface markers (CD9, CD14, CD42a, CD69 and CD105) and analyzed by FACS. Internalization of MPs by PBMCs were assessed by SP-DiOC staining. Results FACS analysis demonstrated that number of MPs in ml plasma was 8,3 ± 1,5 x105, 3,2 ± 1,8 x105, 1,9 ± 0,8 x105, and 3,2 ± 2,2 x105 in healthy, atopic dermatitis, asthma controlled and asthma attack subjects, respectively.
Open Access
Design of a droplet-based microfluidic system for hybrid polymer nanoparticle synthesis
(2021-12) Şahinoğlu, Osman Berkay
Droplet microfluidics is advantageous in synthesizing microparticles for both confining their size to the physical dimensions of the droplet and providing a monodisperse result due to rapid mixing inside the droplets. Thusly named microreactors became the focus of the microfluidics community in the recent decade due to their superior ability to control the reaction environment. In this study, for the application of microreactors, a hybrid organic-inorganic material that became prominent in last years named polyhedral oligomeric silsesquioxane (POSS) is chosen. POSS is a polymer that, beside its hybrid nature, shows heat resistance property which made its use in protective painting applications and high radical group affinity that can be utilized to further configure its material properties. This study proposes two microreaction systems for monomer POSS with ther-mal and photopolymerization methods that aim to increase monodispersity and solve the clogging problem encountered in previous studies by introducing the oil phase in the system. Feasibility of systems was investigated numerically using COMSOL Multiphysics and analyses showed adequate heating of and mixing in microreactors. A robust post-processing procedure is proposed to remove excess oil from the sample. Measurements showed microdroplet and sub-micron particle generation where the size distribution of these particles are quantified using MATLAB. Though the use of oil in the system proved to be another challange, hexane based substitute materials are proposed for future work.
Embargo
Microwave resonant sensor integration with impedance cytometry in microfluidic platform for probing micro-scale dielectric permittivity
(2023-09) Tefek, Uzay
This thesis presents a novel multiphysical sensor that integrates low-frequency impedance cytometry with high-frequency microwave capacitance sensing. The characterization of microscale objects, including microparticles and cells, is essential in various scientific disciplines, such as biology, materials science, and environmental science. Accurate identification and classification of these microscale entities are critical for applications ranging from drug delivery optimization to environmental impact assessment, however, the current techniques fall short in terms of the rapidity and cost-effectiveness necessary for analyzing extensive populations. To address this challenge, our hybrid sensor combines low-frequency impedance cytometry and high-frequency microwave capacitance sensing for material characterization based on dielectric permittivity. This integration offers a rapid, cost-effective, and highly accurate method for identifying and characterizing microscale particles and cells. Experimental studies demonstrate the sensor’s efficacy, achieving remarkable signal-to-noise ratios. The sensor’s versatility ex-tends monitoring permittivity changes in single cells exposed to fixing agents offering valuable insights into cellular properties. In summary, this thesis introduces an innovative multiphysical sensor that advances microscale entity analysis, enabling rapid and precise identification and characterization.
Open Access
Permittivity-based microparticle classification by the integration of impedance cytometry and microwave resonators
(John Wiley and Sons Inc, 2023-11-16) Tefek, Uzay; Sari, B.; Alhmoud, Hashim Ziad; Hanay, Mehmet Selim
Permittivity of microscopic particles can be used as a classification parameter for applications in materials and environmental sciences. However, directly measuring the permittivity of individual microparticles has proven to be challenging due to the convoluting effect of particle size on capacitive signals. To overcome this challenge, a sensing platform is built to independently obtain both the geometric and electric size of a particle, by combining impedance cytometry and microwave resonant sensing in a microfluidic chip. This way the microwave signal, which contains both permittivity and size effects, can be normalized by the size information provided by impedance cytometry to yield an intensive parameter that depends only on permittivity. The technique allows to differentiate between polystyrene and soda lime glass microparticles—below 22 µm in diameter—with more than 94% accuracy, despite their similar sizes and electrical characteristics. Furthermore, it is shown that the same technique can be used to differentiate between normal healthy cells and fixed cells of the same geometric size. The technique offers a potential route for targeted applications such as environmental monitoring of microplastic pollution or quality control in pharmaceutical industry.
Open Access
Platelet-derived microparticles differentially regulate macrophage polarization
(2016-09) Köksal, Elif Senem
Platelet-derived microparticles (PMPs) shed from platelets upon activation and constitute almost 90% of the circulating microparticles. Due to their versatile cargo, PMPs were associated with the generation of immunosuppressive microenvironment and and thought to promote tumor growth. They are also potential candidates for prevention and treatment of autoimmune diseases. Macrophages are one of the enigmatic cells of the immune system. They are either categorized as ‘M1-type’, mediating an inflammatory environment or ‘M2-type’, mediating an immune suppressive environment. Cardinal signals resulting M1-tropic or M2-tropic macrophage differentiation is not fully understood. However, it is crucial to understand the inducers of macrophage polarization for therapeutic approaches. We aimed to understand the interaction between PMPs with macrophages and wished to understand mechanistic alterations upon macrophages engage with PMPs. In this thesis, we showed that activated human platelets released microparticles and they were internalized by macrophages differentiated from THP1 monocytic cell line. Internalized PMPs co-localized with late endosomes. The phagocytic capacity of M2- polarized THP1 macrophages were greater than M1-polarized macrophages. Strikingly, when THP1 derived macrophages were treated with standalone PMPs our results revealed that these macrophage were unable to mount any detectable cytokine secretion related to M1 or M2 type identity. This prompted us to encapsulate TLR agonists within PMPs and harness them as a carrier system. Different TLR ligands including TLR7 (sensing ssRNA) and TLR9 (sensing ss/ds DNA expressing CpG motifs) ligands were incorporated within PMPs via dehydration-rehydration method that was developed in our laboratory. Upon screening of several TLR agonist candidates on healthy donor PBMCs as well as on purified monocytes, we found that M1-like macrophage differentiation was TLR9 agonist D-type CpG oligodeoxynucleotide loaded PMP dependent whereas M2-like macrophage differentiation was dependent on TLR7 agonist R848 loaded PMPs. In conclusion, this work implicated that PMP treatment of macrophages loaded with suitable ligand combinations might regulate M1/M2 type macrophage differentiation and could be used efficiently either to control tumor development (M1) or to alleviate symptoms of auto-immune/auto-inflammatory diseases (M2).