Pre-enrichment-free detection of hepatocellular carcinoma-specific ctDNA via PDMS and MEMS-based microfluidic sensor.

The growing interest in microfluidic biosensors has led to improvements in the analytical performance of various sensing mechanisms. Although various sensors can be integrated with microfluidics, electrochemical ones have been most commonly employed due to their ease of miniaturization, integration ability, and low cost, making them an established point-of-care diagnostic method. This concept can be easily adapted to the detection of biomarkers specific to certain cancer types. Pathological profiling of hepatocellular carcinoma (HCC) is heterogeneous and rather complex, and biopsy samples contain limited information regarding the tumor and do not reflect its heterogeneity. Circulating tumor DNAs (ctDNAs), which can contain information regarding cancer characteristics, have been studied tremendously since liquid biopsy emerged as a new diagnostic method. Recent improvements in the accuracy and sensitivity of ctDNA determination also paved the way for genotyping of somatic genomic alterations. In this study, three-electrode (Au-Pt-Ag) glass chips were fabricated and combined with polydimethylsiloxane (PDMS) microchannels to establish an electrochemical microfluidic sensor for detecting c.747G > T hotspot mutations in the TP53 gene of ctDNAs from HCC. The preparation and analysis times of the constructed sensor were as short as 2 h in total, and a relatively high flow rate of 30 µl/min was used during immobilization and hybridization steps. To the best of our knowledge, this is the first time a PDMS-based microfluidic electrochemical sensor has been developed to target HCC ctDNAs. The system exhibited a limit of detection (LOD) of 24.1 fM within the tested range of 2-200 fM. The sensor demonstrated high specificity in tests conducted with fully noncomplementary and one-base mismatched target sequences. The developed platform is promising for detecting HCC-specific ctDNA at very low concentrations without requiring pre-enrichment steps.

Piezoelectric Multi-Channel Bilayer Transducer for Sensing and Filtering Ossicular Vibration.

This paper presents an acoustic transducer for fully implantable cochlear implants (FICIs), which can be implanted on the hearing chain to detect and filter the ambient sound in eight frequency bands between 250 and 6000 Hz. The transducer dimensions are conventional surgery compatible. The structure is formed with 3  × 3 × 0.36 mm active space for each layer and 5.2 mg total active mass excluding packaging. Characterization of the transducer is carried on an artificial membrane whose vibration characteristic is similar to the umbo vibration. On the artificial membrane, piezoelectric transducer generates up to 320.3 mVpp under 100 dB sound pressure level (SPL) excitation and covers the audible acoustic frequency. The measured signal-to-noise-ratio (SNR) of the channels is up to 84.2 dB. Sound quality of the transducer for fully implantable cochlear implant application is graded with an objective qualification method (PESQ) for the first time in the literature to the best of the knowledge, and scored 3.42/4.5.

Analytical Validation of a Spiral Microfluidic Chip with Hydrofoil-Shaped Pillars for the Enrichment of Circulating Tumor Cells.

The isolation of circulating tumor cells (CTCs) from peripheral blood with high efficiency remains a challenge hindering the utilization of CTC enrichment methods in clinical practice. Here, we propose a microfluidic channel design for the size-based hydrodynamic enrichment of CTCs from blood in an epitope-independent and high-throughput manner. The microfluidic channel comprises a spiral-shaped part followed by a widening part, incorporating successive streamlined pillars, that improves the enrichment efficiency. The design was tested against two benchmark designs, a spiral microfluidic channel and a spiral microfluidic channel followed by a widening channel without the hydrofoils, by processing 5 mL of healthy blood samples spiked with 100 MCF-7 cells. The results proved that the design with hydrofoil-shaped pillars perform significantly better in terms of recovery (recovery rate of 67.9% compared to 23.6% in spiral and 56.7% in spiral with widening section), at a cost of slightly lower white blood cell (WBC) depletion (depletion rate of 94.2% compared to 98.6% in spiral and 94.2% in spiral with widening section), at 1500 µL/min flow rate. For analytical validation, the design was further tested with A549, SKOV-3, and BT-474 cell lines, yielding recovery rates of 62.3 ± 8.4%, 71.0 ± 6.5%, and 82.9 ± 9.9%, respectively. The results are consistent with the size and deformability variation in the respective cell lines, where the increasing size and decreasing deformability affect the recovery rate in a positive manner. The analysis before and after the microfluidic chip process showed that the process does not affect cell viability.

A pumpless monolayer microfluidic device based on mesenchymal stem cell-conditioned medium promotes neonatal mouse in vitro spermatogenesis.

BACKGROUND: Childhood cancer treatment-induced gonadotoxicity causes permanent infertility/sub-infertility in nearly half of males. The current clinical and experimental approaches are limited to cryopreservation of prepubertal testicular strips and in vitro spermatogenesis which are inadequate to achieve the expanded spermatogonial stem/progenitor cells and spermatogenesis in vitro. Recently, we reported the supportive effect of bone marrow-derived mesenchymal cell co-culture which is inadequate after 14 days of culture in static conditions in prepubertal mouse testis due to lack of microvascular flow and diffusion. Therefore, we generated a novel, pumpless, single polydimethylsiloxane-layered testis-on-chip platform providing a continuous and stabilized microfluidic flow and real-time cellular paracrine contribution of allogeneic bone marrow-derived mesenchymal stem cells. METHODS: We aimed to evaluate the efficacy of this new setup in terms of self-renewal of stem/progenitor cells, spermatogenesis and structural and functional maturation of seminiferous tubules in vitro by measuring the number of undifferentiated and differentiating spermatogonia, spermatocytes, spermatids and tubular growth by histochemical, immunohistochemical, flow cytometric and chromatographic techniques. RESULTS: Bone marrow-derived mesenchymal stem cell-based testis-on-chip platform supported the maintenance of SALL4(+) and PLZF(+) spermatogonial stem/progenitor cells, for 42 days. The new setup improved in vitro spermatogenesis in terms of c-Kit(+) differentiating spermatogonia, VASA(+) total germ cells, the meiotic cells including spermatocytes and spermatids and testicular maturation by increasing testosterone concentration and improved tubular growth for 42 days in comparison with hanging drop and non-mesenchymal stem cell control. CONCLUSIONS: Future fertility preservation for male pediatric cancer survivors depends on the protection/expansion of spermatogonial stem/progenitor cell pool and induction of in vitro spermatogenesis. Our findings demonstrate that a novel bone marrow-derived mesenchymal stem cell-based microfluidic testis-on-chip device supporting the maintenance of stem cells and spermatogenesis in prepubertal mice in vitro. This new, cell therapy-based microfluidic platform may contribute to a safe, precision-based cell and tissue banking protocols for prepubertal fertility restoration in future.

Microfluidic-based blood immunoassays.

Microfluidics enables the integration of whole protocols performed in a laboratory, including sample loading, reaction, extraction, and measurement steps on a single system, which offers significant advantages thanks to small-scale operation combined with precise fluid control. These include providing efficient transportation mechanisms and immobilization, reduced sample and reagent volumes, fast analysis and response times, lower power requirements, lower cost and disposability, improved portability and sensitivity, and greater integration and automation capability. Immunoassay is a specific bioanalytical method based on the interaction of antigens and antibodies, which is utilized to detect bacteria, viruses, proteins, and small molecules in several areas such as biopharmaceutical analysis, environmental analysis, food safety, and clinical diagnostics. Because of the advantages of both techniques, the combination of immunoassays and microfluidic technology is considered one of the most potential biosensor systems for blood samples. This review presents the current progress and important developments in microfluidic-based blood immunoassays. After providing several basic information about blood analysis, immunoassays, and microfluidics, the review points out in-depth information about microfluidic platforms, detection techniques, and commercial microfluidic blood immunoassay platforms. In conclusion, some thoughts and future perspectives are provided.

Spheroid Engineering in Microfluidic Devices.

Two-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.

Label-free enrichment of MCF7 breast cancer cells from leukocytes using continuous flow dielectrophoresis.

Circulating tumor cells (CTCs) present in the bloodstream are strongly linked to the invasive behavior of cancer; therefore, their detection holds great significance for monitoring disease progression. Currently available CTC isolation tools are often based on tumor-specific antigen or cell size approaches. However, these techniques are limited due to the lack of a unique and universal marker for CTCs, and the overlapping size between CTCs and regular blood cells. Dielectrophoresis (DEP), governed by the intrinsic dielectric properties of the particles, is a promising marker-free, accurate, fast, and low-cost technique that enables the isolation of CTCs from blood cells. This study presents a continuous flow, antibody-free DEP-based microfluidic device to concentrate MCF7 breast cancer cells, a well-established CTC model, in the presence of leukocytes extracted from human blood samples. The enrichment strategy was determined according to the DEP responses of the corresponding cells, obtained in our previously reported DEP spectrum study. It was based on the positive-DEP integrated with hydrodynamic focusing under continuous flow. In the proposed device, the parylene microchannel with two inlets and outlets was built on top of rectangular and equally spaced isolated planar electrodes rotated certain degree relative to the main flow (13°). The recovery of MCF7 cells mixed with leukocytes was 74%-98% at a frequency of 1 MHz and a magnitude of 10-12 Vpp . Overall, the results revealed that the presented system successfully concentrates MCF7 cancer cells from leukocytes, ultimately verifying our DEP spectrum study, in which the enrichment frequency and separation strategy of the microfluidic system were determined.

A microfluidic device enabling drug resistance analysis of leukemia cells via coupled dielectrophoretic detection and impedimetric counting.

We report the development of a lab-on-a-chip system, that facilitates coupled dielectrophoretic detection (DEP-D) and impedimetric counting (IM-C), for investigating drug resistance in K562 and CCRF-CEM leukemia cells without (immuno) labeling. Two IM-C units were placed upstream and downstream of the DEP-D unit for enumeration, respectively, before and after the cells were treated in DEP-D unit, where the difference in cell count gave the total number of trapped cells based on their DEP characteristics. Conductivity of the running buffer was matched the conductivity of cytoplasm of wild type K562 and CCRF-CEM cells. Results showed that DEP responses of drug resistant and wild type K562 cells were statistically discriminative (at p = 0.05 level) at 200 mS/m buffer conductivity and at 8.6 MHz working frequency of DEP-D unit. For CCRF-CEM cells, conductivity and frequency values were 160 mS/m and 6.2 MHz, respectively. Our approach enabled discrimination of resistant cells in a group by setting up a threshold provided by the conductivity of running buffer. Subsequent selection of drug resistant cells can be applied to investigate variations in gene expressions and occurrence of mutations related to drug resistance.

13.56 MHz Triple Mode Rectifier Circuit With Extended Coupling Range for Wirelessly Powered Implantable Medical Devices.

In this work, a wide input/output range triple mode rectifier circuit operating at 13.56 MHz is implemented to power up medical implants. The proposed novel multi-mode rectifier circuit charges the load for an extended coupling range and eliminates the requirement of alignment magnets. The charging process is achieved in three different modes based on the voltage level of the received signal affected by the distance and the alignment of the inductively coupled coils. Current mode (CM) circuit is activated for loosely coupled coils whereas voltage mode (VM) rectification is proposed for high coupling ratios. Extended coupling range is covered with the activation of half wave rectification mode (HWM) in between CM and VM. The rectifier circuit utilizes these three modes in a single circuit operating at 13.56 MHz according to the receiver signal voltage. The circuit is implemented in TSMC 180 nm BCD technology with 0.9 mm2 active area and tested with printed coils. According to the measurements, the circuit operates in the received power range of 4 to 57.7 mW, which corresponds to 0.10-0.42 coupling range. The maximum power conversion efficiency (PCE) of each operation mode is 51.78%, 82.49%, and 89.34% for CM, HWM, and VM, respectively, while charging a 3.3 V load.

A Novel Microfluidic Method Utilizing a Hydrofoil Structure to Improve Circulating Tumor Cell Enrichment: Design and Analytical Validation.

Being one of the major pillars of liquid biopsy, isolation and characterization of circulating tumor cells (CTCs) during cancer management provides critical information on the evolution of cancer and has great potential to increase the success of therapies. In this article, we define a novel strategy to effectively enrich CTCs from whole blood based on size, utilizing a spiral microfluidic channel embedded with a hydrofoil structure at the downstream of the spiral channel. The hydrofoil increases the distance between the streams of CTCs and peripheral blood cells, which are already distributed about two focal axes by the spiral channel, thereby improving the resolution of the separation. Analytical validation of the system has been carried out using Michigan Cancer Foundation-7 (MCF7) breast cancer cell lines spiked into blood samples from healthy donors, and the performance of the system in terms of white blood cell (WBC) depletion, CTC recovery rate and cell viability has been shown in single or two-step process: by passing the sample once or twice through the microfluidic chip. Single step process yielded high recovery (77.1%), viable (84.7%) CTCs. When the collected cell suspension is re-processed by the same chip, recovery decreases to 65.5%, while the WBC depletion increases to 88.3%, improving the purity. Cell viability of >80% was preserved after two-step process. The novel microfluidic chip is a good candidate for CTC isolation applications requiring high recovery rate and viability, including functional downstream analyses for variety of cancer types.

A Prominent Cell Manipulation Technique in BioMEMS: Dielectrophoresis.

BioMEMS, the biological and biomedical applications of micro-electro-mechanical systems (MEMS), has attracted considerable attention in recent years and has found widespread applications in disease detection, advanced diagnosis, therapy, drug delivery, implantable devices, and tissue engineering. One of the most essential and leading goals of the BioMEMS and biosensor technologies is to develop point-of-care (POC) testing systems to perform rapid prognostic or diagnostic tests at a patient site with high accuracy. Manipulation of particles in the analyte of interest is a vital task for POC and biosensor platforms. Dielectrophoresis (DEP), the induced movement of particles in a non-uniform electrical field due to polarization effects, is an accurate, fast, low-cost, and marker-free manipulation technique. It has been indicated as a promising method to characterize, isolate, transport, and trap various particles. The aim of this review is to provide fundamental theory and principles of DEP technique, to explain its importance for the BioMEMS and biosensor fields with detailed references to readers, and to identify and exemplify the application areas in biosensors and POC devices. Finally, the challenges faced in DEP-based systems and the future prospects are discussed.

Enhancement of the Start-Up Time for Microliter-Scale Microbial Fuel Cells (µMFCs) via the Surface Modification of Gold Electrodes.

Microbial Fuel Cells (MFCs) are biological fuel cells based on the oxidation of fuels by electrogenic bacteria to generate an electric current in electrochemical cells. There are several methods that can be employed to improve their performance. In this study, the effects of gold surface modification with different thiol molecules were investigated for their implementation as anode electrodes in micro-scale MFCs (µMFCs). Several double-chamber µMFCs with 10.4 µL anode and cathode chambers were fabricated using silicon-microelectromechanical systems (MEMS) fabrication technology. µMFC systems assembled with modified gold anodes were operated under anaerobic conditions with the continuous feeding of anolyte and catholyte to compare the effect of different thiol molecules on the biofilm formation of Shewanella oneidensis MR-1. Performances were evaluated using polarization curves, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microcopy (SEM). The results showed that µMFCs modified with thiol self-assembled monolayers (SAMs) (cysteamine and 11-MUA) resulted in more than a 50% reduction in start-up times due to better bacterial attachment on the anode surface. Both 11-MUA and cysteamine modifications resulted in dense biofilms, as observed in SEM images. The power output was found to be similar in cysteamine-modified and bare gold µMFCs. The power and current densities obtained in this study were comparable to those reported in similar studies in the literature.

A comparative study on EpCAM antibody immobilization on gold surfaces and microfluidic channels for the detection of circulating tumor cells.

Detection of circulating tumor cells (CTCs) from the bloodstream holds great importance to diagnose cancer at early stages. However, CTCs being extremely rare in blood makes them difficult to reach. In this paper, we introduced different surface modification techniques for the enrichment and detection of MCF-7 in microfluidic biosensor applications using gold surface and EpCAM antibody. Mainly, two different mechanisms were employed to immobilize the antibodies; covalent bonding and bioaffinity interaction. Self-assembled monolayers (SAMs) formed on the gold surfaces were treated further for the immobilization of the antibody. The bioaffinity-based studies were performed with streptavidin and biotinylated EpCAM over the SAM coated surfaces. The cell attachment events were monitored using fluorescent microscope. Comparisons were made considering the length and functional end of alkanethiols and the positioning of the antibody. Then, these methods were integrated into a microfluidic channel system. Surface characterizations were performed with X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, and contact angle measurements. The selectivity studies were carried out with EpCAM negative K562 leukaemia cell lines and the experiments were repeated for different types of surfaces, such as glass and polymer. Studies showed that long (n>10) and aromatic ring containing alkanethiols lead to better cell capture events compared to shorter ones. Results obtained from the comparisons are of importance for the gold surface-based microfluidic biosensor designs aimed for CTC detection.

Examination of the dielectrophoretic spectra of MCF7 breast cancer cells and leukocytes.

The detection of circulating tumor cells (CTCs) in blood is crucial to assess metastatic progression and to guide therapy. Dielectrophoresis (DEP) is a powerful cell surface marker-free method that allows intrinsic dielectric properties of suspended cells to be exploited for CTC enrichment/isolation from blood. Design of a successful DEP-based CTC enrichment/isolation system requires that the DEP response of the targeted particles should accurately be known. This paper presents a DEP spectrum method to investigate the DEP spectra of cells without directly analyzing their membrane and cytoplasmic properties in contrast to the methods in literature, which employ theoretical assumptions and complex modeling. Integrating electric field simulations based on DEP theory with the experimental data enables determination of the DEP spectra of leukocyte subpopulations, polymorphonuclear and mononuclear leukocytes, and MCF7 breast cancer cells as a model of CTC due to their metastatic origin over the frequency range 100 kHz-50 MHz at 10 Vpp . In agreement with earlier findings, differential DEP responses were detected for mononuclear and polymorphonuclear leukocytes due to the richness of the cell surface features and morphologies of the different leukocyte types. The data reveal that the strength of the DEP force exerted on MCF7 cells was particularly high between 850 kHz and 20 MHz. These results illustrate that the proposed technique has the potential to provide a generic platform to identify DEP responses of different biological particles.

Comparative study on antibody immobilization strategies for efficient circulating tumor cell capture.

Methods for isolation and quantification of circulating tumor cells (CTCs) are attracting more attention every day, as the data for their unprecedented clinical utility continue to grow. However, the challenge is that CTCs are extremely rare (as low as 1 in a billion of blood cells) and a highly sensitive and specific technology is required to isolate CTCs from blood cells. Methods utilizing microfluidic systems for immunoaffinity-based CTC capture are preferred, especially when purity is the prime requirement. However, antibody immobilization strategy significantly affects the efficiency of such systems. In this study, two covalent and two bioaffinity antibody immobilization methods were assessed with respect to their CTC capture efficiency and selectivity, using an anti-epithelial cell adhesion molecule (EpCAM) as the capture antibody. Surface functionalization was realized on plain SiO2 surfaces, as well as in microfluidic channels. Surfaces functionalized with different antibody immobilization methods are physically and chemically characterized at each step of functionalization. MCF-7 breast cancer and CCRF-CEM acute lymphoblastic leukemia cell lines were used as EpCAM positive and negative cell models, respectively, to assess CTC capture efficiency and selectivity. Comparisons reveal that bioaffinity based antibody immobilization involving streptavidin attachment with glutaraldehyde linker gave the highest cell capture efficiency. On the other hand, a covalent antibody immobilization method involving direct antibody binding by N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC)-N-hydroxysuccinimide (NHS) reaction was found to be more time and cost efficient with a similar cell capture efficiency. All methods provided very high selectivity for CTCs with EpCAM expression. It was also demonstrated that antibody immobilization via EDC-NHS reaction in a microfluidic channel leads to high capture efficiency and selectivity.

Characterization of the distribution of rotational torque on electrorotation chips with 3D electrodes.

This is a study of in-plane and out-of-plane distribution of rotational torque (ROT-T) and effective electric field (EEF) on electrorotation (ER) devices with 3D electrodes using finite element modeling (FEM) and experimental method. The objective of this study is to investigate electrical characteristics of the ER devices with five different electrode geometries and obtain an optimum structure for ER experiments. Further, it provides a comparison between characteristics of the 3D electrodes and traditionally used 2D electrodes. 3D distributions of EEF were studied by the time-variant FEM. FEM results were verified experimentally by studying the rotation of biological cells. The results show that the variations of ROT-T and EEF over the measurement area of the devices are considerably large. This can potentially lead to misinterpretation of recorded data. Therefore, it is essential to specify the boundaries of the measurement area with minimum deviation from the central EEF. For this purpose, FE analyses were utilized to specify the optimal region. Thereby, with confining the measurements to these regions, the dependency of ROT-T on the spatial position of the particles can be eliminated. Comparisons have been made on the sustainability of the EEF and ROT-T distributions for each device, to find an optimum design. Analyses of the devices prove that utilization of the 3D electrodes eliminate irregularities of EEF and ROT-T along the z-axis. The Results show that triangular electrodes provide the highest sustainability for the in-plane ROT-T and EEF distribution, while the oblate elliptical and circular electrodes have the lowest variances along the z-axis.

Label-free detection of multidrug resistance in K562 cells through isolated 3D-electrode dielectrophoresis.

Dielectrophoresis (DEP), a technique used to separate particles based on different sizes and/or dielectric properties under nonuniform electric field, is a promising method to be applied in label-free, rapid, and effective cell manipulation and separation. In this study, a microelectromechanical systems-based, isolated 3D-electrode DEP device has been designed and implemented for the label-free detection of multidrug resistance in K562 leukemia cells, based on the differences in their cytoplasmic conductivities. Cells were hydrodynamically focused to the 3D-electrode arrays, placed on the side walls of the microchannel, through V-shaped parylene-C obstacles. 3D-electrodes extruded along the z-direction provide uniformly distributed DEP force through channel depth. Cell suspension containing resistant and sensitive cancer cells with 1:100 ratio was continuously flown through the channel at a rate of 10 µL/min. Detection was realized at 48.64 MHz, the cross-over frequency of sensitive K562 cells, at which sensitive cells flow with the fluid, while the resistant ones are trapped by positive DEP force. Device can be operated at considerably low voltages (<9 Vpp ). This is achieved by means of a very thin (0.5 µm) parylene coating on electrodes, providing the advantages offered by the isolation of electrodes from the sample, while the working voltage can still be kept low. Results prove that the presented DEP device can provide an efficient platform for the detection of multidrug resistance in leukemia, in a label-free manner.

Breath sensors for lung cancer diagnosis.

The scope of the applications of breath sensors is abundant in disease diagnosis. Lung cancer diagnosis is a well-fitting health-related application of this technology, which is of utmost importance in the health sector, because lung cancer has the highest death rate among all cancer types, and it brings a high yearly global burden. The aim of this review is first to provide a rational basis for the development of breath sensors for lung cancer diagnostics from a historical perspective, which will facilitate the transfer of the idea into the rapidly evolving sensors field. Following examples with diagnostic applications include colorimetric, composite, carbon nanotube, gold nanoparticle-based, and surface acoustic wave sensor arrays. These select sensor applications are widened by the state-of-the-art developments in the sensors field. Coping with sampling sourced artifacts and cancer staging are among the debated topics, along with the other concerns like proteomics approaches and biomimetic media utilization, feature selection for data classification, and commercialization.

Studies on visual detection and surface modification testing of glass microfiber filter paper based biosensor.

Glass microfibers are commonly used as biomolecule adsorption media, as structural or disposable components of the optical biosensors. While any improvement in these components are appreciated, utilizing basic tools of traditional approaches may lead to original sensor opportunities as simple, functional designs that can be easily disseminated. Following this pursuit, surface modification of glass microfiber paper surface was performed by 3-aminopropyltriethoxysilane (APTES) and resulting improvement in the cell entrapment capacity could be observed visually, only after Gram staining. Gram staining offered rapid validation of enhanced binding on the glass surface. The same APTES-modified samples were also tested for binding of complementary DNA sequences and the results were less straightforward due to the necessity of DNA visualization by using a fluorescent stain, YOYO-1. Accordingly, when there were no surface modification, DNA and YOYO-1 adsorbed readily on the glass microfiber filter paper, and prolonged the interaction between DNA and YOYO-1. YOYO-1 adsorption on glass could be recognized from the color profile of YOYO-1 emission. This phenomenon can be used to examine suitability of APTES coverage on glass surfaces since YOYO-1 emission can be distinguished by its glass adsorbed versus DNA-bound forms. Aptness of surface coverage is vital to biosensor studies in the sense that it is preceding the forthcoming surface modifications and its precision is imperative for attaining the anticipated interaction kinetics of the surface-immobilized species. The proposed testing scheme offered in this study secures the work, which is aimed to be carried out utilizing such sensing systems and device components.

Dielectrophoresis: applications and future outlook in point of care.

Dielectrophoresis (DEP) is a label free, noninvasive, stand alone, rapid, and sensitive particle manipulation and characterization technique. Improvements in micro-electro-mechanical systems technology have enabled the biomedical applications of DEP over the past decades. By this way, integration of DEP into lab-on-a-chip systems has become achievable, creating a potential tool for point-of-care (POC) systems. DEP can be utilized in many different POC applications including early detection and prognosis of various cancer types, diagnosis of infectious diseases, blood cell analysis, and stem cell therapy. However, there are still some challenges to be resolved to have DEP-based devices available in POC market. Today, researchers have focused on these challenges to have this powerful theory as a solution for many POC applications. Here, DEP theory, cell modeling, and most common device structures are introduced briefly. Next, POC applications of DEP theory, such as cell (blood, cancer, stem, and fetal) and microorganism separation, manipulation, and enrichment for diagnosis and prognosis, are explained. Integration of DEP with other detection techniques to have more sensitive systems is summarized. Finally, future outlook for DEP-based systems are discussed with some challenges, which are currently preventing these systems to be a common tool for POC applications, and possible solutions.