A simple approach for the fabrication of 3D microelectrodes for impedimetric sensing

WOS: 000365167700026In this paper, we present a very simple method to fabricate three-dimensional (3D) microelectrodes integrated with microfluidic devices. We form the electrodes by etching a microwire placed across a microchannel. For precise control of the electrode spacing, we employ a hydrodynamic focusing microfluidic device and control the width of the etching solution stream. The focused widths of the etchant solution and the etching time determine the gap formed between the electrodes. Using the same microfluidic device, we can fabricate integrated 3D electrodes with different electrode gaps. We have demonstrated the functionality of these electrodes using an impedimetric particle counting setup. Using 3D microelectrodes with a diameter of 25 mu m, we have detected 6 mu m-diameter polystyrene beads in a buffer solution as well as erythrocytes in a PBS solution. We study the effect of electrode spacing on the signal-to-noise ratio of the impedance signal and we demonstrate that the smaller the electrode spacing the higher the signal obtained from a single microparticle. The sample stream is introduced to the system using the same hydrodynamic focusing device, which ensures the alignment of the sample in between the electrodes. Utilising a 3D hydrodynamic focusing approach, we force all the particles to go through the sensing region of the electrodes. This fabrication scheme not only provides a very low-cost and easy method for rapid prototyping, but which can also be used for applications requiring 3D electric field focused through a narrow section of the microchannel.Scientific and Technological Research Council of Turkey (TUBITAK) [112M944]; European Union [322019]This project was supported by The Scientific and Technological Research Council of Turkey (TUBITAK project no. 112M944) and European Union FP7 Marie Curie Career Integration Grant (no. 322019). The authors also thank Dr Aykutlu Dana, Dr Gokhan Bakan and Amir Ghobadi for their help in the measurement setup and their comments on the manuscript

Focusing-free impedimetric differentiation of red blood cells and leukemia cells: A system optimization

Bilican, İsmail ( Aksaray, Yazar )A focusing-free microfluidic impedimetric cell detection system is developed. The effect of the channel dimensions, solution conductivity, excitation voltage, and particle size on impedimetric signal outputs were optimized to increase the sensitivity of the system. Conventional microfabrication techniques were adapted to obtain low height, resealable microchannels. The geometry optimization was performed by a combination of analytical, numerical and experimental approaches. The results demonstrate that reliable impedimetric particle differentiation can be achieved without any labeling or particle focusing. The system parameters were studied and rule-of-thumb design criteria were provided. Finally, using the developed system, red blood cells and leukemia cells were experimentally detected and differentiated. Thanks to its simplicity, the focusing-free cell differentiation system may find applications in several cellular diagnostic uses

An in-situ fabrication technique to form integrated microelectrodes

ACS Publications, Analytical Chemistry;American Elements;Aquatech Co., Ltd and Takasago Fluidic Systems;ASK;CapitalBio Technology;et al.19th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2015 -- 25 October 2015 through 29 October 2015 -- -- 122797In this study we have developed a new fabrication method to form microelectrodes for microfluidic applications. We present a microfabrication route to achieve embedded microelectrodes within a microchannel without needing for a microfabrication facility or lithography and metallization processes. This method includes attaching a gold microwires on a glass slide and bonding PDMS micro channels perpendicular to the microwire. Then aqua regia solution is passed through the channel etching the wire inside of the channel and forming two electrodes on the two sides. We applied these electrodes to the impedance flow cytometry for high sensitive detection of polystyrene beads and red blood cells. We also compared the performance of our electrodes with the coplanar electrodes which is the most commonly used geometry of the impedance flow cytometry. The etched electrodes give up to 20 times better SNR compared to coplanar electrodes. © 15CBMS-0001

A smartphone based surface plasmon resonance imaging (SPRi) platform for on-site biodetection

We demonstrate a surface plasmon resonance imaging platform integrated with a smartphone to be used in the field with high-throughput biodetection. Inexpensive and disposable SPR substrates are produced by metal coating of commercial Blu-ray discs. A compact imaging apparatus is fabricated using a 3D printer which allows taking SPR measurements from more than 20.000 individual pixels. Real-time bulk refractive index change measurements yield noise equivalent refractive index changes as low as 4.12 x 10(-5) RIU which is comparable with the detection performance of commercial instruments. As a demonstration of a biological assay, we have shown capture of mouse IgG antibodies by immobilized layer of rabbit anti-mouse (RAM) IgG antibody with nanomolar level limit of detection. Our approach in miniaturization of SPR biosensing in a cost-effective manner could enable realization of portable SPR measurement systems and kits for point-of-care applications. (C) 2016 Published by Elsevier B.V

Sponge-derived natural bioactive glass microspheres with self-assembled surface channel arrays opening into a hollow core for bone tissue and controlled drug release applications

Porous, bioactive microspheres have always been a dream material to biomedical scientists for bone regeneration and drug delivery applications due to their interconnectivity, unique pore geometry, encapsulation ability and porosity spanning macroscopic, microscopic and nanoscopic length scales. Extensive efforts have been made to produce such materials synthetically at a great cost of money, time and labor. Herein, naturally-assembled multifunctional, open-channeled and hollow bioactive micro silica spheres (diameter 209.4 +/- 38.5 mu m) were discovered in a marine sponge (Geodia macandrewii), by peeling the outer surface of the sterrasters using hydrogen fluoride. The obtained micro silica spheres exhibited valuable characteristics such as homogeneously distributed pores, a cavity in the center of the sphere, and channels (approx. 3000) opening from each pore into the central cavity. Simulated body fluid analysis demonstrated the bioactivity of the micro silica spheres; whereas, no bioactivity was recorded for the original untreated sterrasters. The non-cytotoxicity and osteogenic ability of the isolated microspheres were confirmed through osteoblast cell culture. Finally, these silica based porous microspheres were tested for controlled drug release capacity. The spheres showed excellent loading and release abilities for an anti-cancer drug, carboplatin, in simulated solutions and in human cancer cell culture, HeLa, through a real time cell analyzer system. The drug loading capacity of the porous beads was determined as 10.59%. Considering the unique biological and physicochemical properties, these novel bioactive silica spheres, which we name as giant macroporous silica (GMS), are promising materials for a range of applications including bone tissue engineering and drug delivery