PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7645
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Article Magnetic Levitation-Based Determination of Single-Nuclei Density(Elsevier, 2026) Anil-Inevi, Muge; Sarigil, Oyku; Unal, Yagmur Ceren; Tekin, H. Cumhur; Mese, Gulistan; Ozcivici, EnginThe biophysical properties of cells and intracellular compartments provide critical insights into their structural and functional states, holding significant potential for biological and medical applications. Single-cell density has recently emerged as a promising biomarker in various research areas, including disease detection, making its precise measurement in biological samples an important analytical objective. Magnetic levitation offers significant advantages over traditional density detection techniques by enabling single-cell analysis rather than bulk measurements, providing precise quantification while preserving natural sample properties and eliminating the need for complex and expensive equipment. While magnetic levitation has been successfully applied to singlecell and cell-aggregate analysis, its use for subcellular compartments remains unexplored. Here, we demonstrate the first application of magnetic levitation technology for the density-based analysis of cell nuclei, a critical organelle essential for genomic preservation and organization. To accommodate the unique size and density characteristics of nuclei compared to whole cells, we systematically investigated appropriate paramagnetic agents, sample loading concentrations, and nuclear equilibrium times required for optimal levitation. We mapped density distributions of nuclei from different cell lines and conducted parallel assessments of cellular and nuclear density changes following cell cycle perturbations and treatments inducing cell death through distinct mechanisms. Our findings establish magnetic levitation as a powerful tool for subcellular density analysis, with potential applications in cell biology research and clinical diagnostics through improved understanding of subcellular physical parameters.Article Citation - WoS: 1Citation - Scopus: 1Electrochemical Sensors for Rapid Cardiovascular Disease Diagnostics(Amer Chemical Soc, 2025) Sanko, Vildan; Tekin, H. CumhurCardiovascular diseases (CVDs) remain a leading cause of death, particularly in developing countries, where their incidence continues to rise. Traditional CVD diagnostic methods are often time-consuming and inconvenient, necessitating more efficient alternatives. Rapid and accurate measurement of cardiac biomarkers released into body fluids is critical for early detection, timely intervention, and improved patient outcomes. Electrochemical methods offer a robust solution by enabling rapid, sensitive, selective, and multiplex detection of CVD biomarkers, paving the way for early diagnosis and treatment advancements. This review highlights the performance and potential of electrochemical sensors for detecting specific CVD biomarkers and related organic molecules. It explores electrochemical sensing mechanisms, their evolution, the integration of nanotechnology, and diverse sensing platforms. It also examines emerging technologies such as microfluidic, smartphone-integrated sensors, and microneedle- and tattoo-based sensors. Challenges and opportunities in integrating electrochemical sensors into point-of-care (POC) and wearable devices are discussed. Finally, the review compares commercial CVD sensors with existing methods and outlines future directions to advance the field.Article Creatinine-On Colorimetric Elisa-Based Serum Creatinine Detection in a Microfluidic Device(Royal Soc Chemistry, 2025) Karakuzu, Betul; Tekin, H. CumhurChronic kidney diseases (CKDs), which often end in kidney failure for many people around the world, have an important place in public health given that they also trigger other diseases. Therefore, the development of fast and cost-effective diagnostic technologies enables effective monitoring of patients and early diagnosis. Here, using the Enzyme-Linked Immunosorbent Assay (ELISA) principle, serum creatinine concentrations were determined using the developed lab-on-a-chip (LOC) platform. In this system, which was termed "creatinine-on-a-chip", colorimetric ELISA protocol was applied to determine creatinine levels in a microfluidic chip functionalized with creatinine-specific antibodies. Creatinine detection was performed by quantifying the absorbance difference between the detection and reference channels, normalized to the reference signal within the microfluidic chip. The detection signal intensity varied depending on the region selected along the microfluidic channel. The adsorption of the capture antibody used for surface functionalization, which was particularly more pronounced near the inlet region, played a critical role in the detection signal. These findings suggest that random selection of the detection area can lead to significant signal variability, and that careful selection of a well-characterized region is essential for improving detection performance. With this developed system, creatinine was detected with high sensitivity in the linear range of 1-20 mu g mL-1, both spiked in phosphate buffered saline (PBS) and fetal bovine serum (FBS). Using the creatinine-on-a-chip, serum creatinine analysis can be performed rapidly (similar to 15 min) in a cost-effective manner ($1.05 per test).Article Citation - WoS: 3Citation - Scopus: 4Magsity Platform: a Hybrid Magnetic Levitation-Based Lensless Holographic Microscope Platform for Liquid Density and Viscosity Measurements(Royal Soc Chemistry, 2025) Ince, Oyku Doyran; Tekin, H. CumhurThe viscosity and density of liquids are the most extensively studied material properties, as their accurate measurement is critical in various industries. Although developments in micro-viscometers have overcome the limitations of traditional bulky methods, more accessible technologies are required. Here, we introduce a novel magnetic levitation-based method to measure the viscosity and density of solutions in a microcapillary channel. This principle exploits microparticles as microsensors to correlate levitation time and height with solutions' viscosity and density, using buoyancy and drag forces. The platform has an integrated lensless holographic microscope, providing a hybrid system for in situ and precise measurements. By utilizing this hybrid technology, portable, rapid and cost-effective measurements can be conducted. This platform enables viscosity and density measurements within 7 minutes, achieving high accuracies of at least 97.7% and 99.9%, respectively, across an operation range of 0.84-5.09 cP and 1.00-1.09 g cm-3. The platform is utilized to clearly distinguish differences in the spent cell culture medium across various cell lines. This method, as presented, can be readily applied to measure a diverse array of liquids in multiple domains, encompassing biotechnology, medicine, and engineering.Article Citation - WoS: 2Citation - Scopus: 3Dynamic Fluidic Manipulation in Microfluidic Chips With Dead-End Channels Through Spinning: the Spinochip Technology for Hematocrit Measurement, White Blood Cell Counting and Plasma Separation(Royal Soc Chemistry, 2025) Oksuz, Cemre; Tekin, Hüseyin Cumhur; Bicmen, Can; Tekin, H. CumhurCentrifugation is crucial for size and density-based sample separation, but low-volume or delicate samples suffer from loss and impurity issues during repeated spins. We introduce the "Spinochip", a novel microfluidic system utilizing centrifugal forces for efficient filling of dead-end microfluidic channels. The Spinochip enables versatile fluid manipulation with a single reservoir for both inlet and outlet functions. It expels compressed air, facilitating fluid flow, and offers programmable filling mechanisms based on the hydraulic resistance of microfluidic channels. Compatible with a basic centrifuge, it allows sequential filling, internal mixing, and collection in straight microfluidic channels by simply adjusting the spinning speed, eliminating the need for complex valving. We demonstrated the Spinochip's efficacy in blood testing, where it successfully separated blood components, such as plasma, buffy coat, and red blood cells, from a single drop using centrifugation alone. This system enabled simultaneous hematocrit (R2 >0.99) and total white blood cell (R2 >0.93) quantification within a single microfluidic channel without the need for staining or special reagents. Remarkably, the Spinochip can perform hematocrit measurements on as little as 100 nL of blood, potentially paving the way for less invasive blood analysis. This innovative approach unlocks new possibilities in microfluidics, providing precise fluidic control and centrifugation for sample volumes as small as a few nanoliters.Article Citation - WoS: 7Citation - Scopus: 7Colorimetric Detection of Serum Creatinine on a Miniaturized Platform Using Hue-Saturation Space Analysis(Nature Portfolio, 2024) Tarim, E. Alperay; Tekin, H. CumhurChronic kidney disease (CKD) is a widespread condition with considerable health and economic impacts globally. However, existing methodologies for serum creatinine assessment often involve prolonged wait times and sophisticated equipment, such as spectrometers, hindering real-time diagnosis and care. Innovative solutions like point-of-care (POC) devices are emerging to address these challenges. In this context, there is a recognized need for remote, regular, automated, and low-cost analysis of serum creatinine levels, given its role as a critical parameter for CKD diagnosis and management. This study introduces a miniaturized system with integrated heater elements designed for precise serum creatinine measurement. The system operates based on the Jaffe method and accurate serum creatinine measurement within a microreservoir chip. Smartphone-based image processing using the hue-saturation-value (HSV) color space was applied to captured images of microreservoirs. The creatinine analyses were conducted in serum with a limit of detection of similar to 0.4 mg/dL and limit of quantification of similar to 1.3 mg/dL. Smartphone-based image processing employing the HSV color space outperformed spectrometric analysis for creatinine measurement conducted in serum. This pioneering technology and smartphone-based processing offer the potential for decentralized renal function testing, which could significantly contribute to improved patient care. The miniaturized system offers a low-cost alternative ($87 per device), potentially reducing healthcare expenditures (similar to $0.5 per test) associated with CKD diagnosis and management. This innovation could greatly improve access to diagnosis and monitoring of CKD, especially in regions where access to sophisticated laboratory equipment is limited.Article Citation - WoS: 2Citation - Scopus: 2Investigating Influences of Intravenous Fluids on Huvec and U937 Monocyte Cell Lines Using the Magnetic Levitation Method(ROYAL SOC CHEMISTRY, 2023) Keçili, Seren; Kaymaz, Sumeyra Vural; Özoğul, Beyzanur; Tekin, H. Cumhur; Elitaş, MeltemIntravenous fluids are being widely used in patients of all ages for preventing or treating dehydration in the intensive care units, surgeries in the operation rooms, or administering chemotherapeutic drugs at hospitals. Dextrose, Ringer, and NaCl solutions are widely received as intravenous fluids by hospitalized patients. Despite their widespread administration for over 100 years, studies on their influences on different cell types have been very limited. Increasing evidence suggests that treatment outcomes might be altered by the choice of the administered intravenous fluids. In this study, we investigated the influences of intravenous fluids on human endothelial (HUVEC) and monocyte (U937) cell lines using the magnetic levitation technique. Our magnetic levitation platform provides label-free manipulation of single cells without altering their phenotypic or genetic properties. It allows for monitoring and quantifying behavior of single cells by measuring their levitation heights, deformation indices, and areas. Our results indicate that HUVEC and U937 cell lines respond differently to different intravenous fluids. Dextrose solution decreased the viability of both cell lines while increasing the heterogeneity of areas, deformation, and levitation heights of HUVEC cells. We strongly believe that improved outcomes can be achieved when the influences of intravenous fluids on different cell types are revealed using robust, label-free, and efficient methods. Label-free analysis of cells exposed to intravenous fluids can be achieved through magnetic levitation technology coupled with cell-morphology characterization.Review Citation - WoS: 52Citation - Scopus: 56Spheroid engineering in microfluidic devices(American Chemical Society, 2023) Tevlek, Atakan; Keçili, Seren; Özçelik, Özge Solmaz; Kulah, Haluk; Tekin, H. CumhurTwo-dimensional (2D) cell culture techniques are commonly employed to investigate biophysical and biochemical cellular responses. However, these culture methods, having monolayer cells, lack cell-cell and cell-extracellular matrix interactions, mimicking the cell microenvironment and multicellular organization. Three-dimensional (3D) cell culture methods enable equal transportation of nutrients, gas, and growth factors among cells and their microenvironment. Therefore, 3D cultures show similar cell proliferation, apoptosis, and differentiation properties to in vivo. A spheroid is defined as self-assembled 3D cell aggregates, and it closely mimics a cell microenvironment in vitro thanks to cell-cell/matrix interactions, which enables its use in several important applications in medical and clinical research. To fabricate a spheroid, conventional methods such as liquid overlay, hanging drop, and so forth are available. However, these labor-intensive methods result in low-throughput fabrication and uncontrollable spheroid sizes. On the other hand, microfluidic methods enable inexpensive and rapid fabrication of spheroids with high precision. Furthermore, fabricated spheroids can also be cultured in microfluidic devices for controllable cell perfusion, simulation of fluid shear effects, and mimicking of the microenvironment-like in vivo conditions. This review focuses on recent microfluidic spheroid fabrication techniques and also organ-on-a-chip applications of spheroids, which are used in different disease modeling and drug development studies.