ABSTRACT
Breast cancer (BC) is the leading cause of cancer death in women worldwide, with a higher mortality reported in undeveloped countries. Ideal adjuvant therapeutic strategies require the continuous monitoring of patients by regular blood tests to detect circulating cancer cells, in order to determine whether additional treatment is necessary to prevent cancer dissemination. This circumstance requires a non-complex design of tumor cell biosensor in whole blood with feasibility for use in poor regions. In this work we have evaluated an inexpensive and simple technique of relative bioimpedance measurement, assisted by magnetic nanoparticles, as a potential biosensor of BC cells in suspension. Measurements represent the relative impedance changes caused by the magnetic holding of an interphase of tumor cells versus a homogenous condition in the frequency range of 10-100 kHz. The results indicate that use of a magnet to separate tumor cells in suspension, coupled to magnetic nanoparticles, is a feasible technique to fix an interphase of tumor cells in close proximity to gold electrodes. Relative impedance changes were shown to have potential value as a biosensor method for BC cells in whole blood, at frequencies around 20 kHz. Additional studies are warranted with respect to electrode design and sensitivity at micro-scale levels, according to the proposed technique.
Subject(s)
Biosensing Techniques , Breast Neoplasms/diagnosis , Dielectric Spectroscopy , Magnetite Nanoparticles , Breast Neoplasms/pathology , Cell Line, Tumor , Electricity , Female , Humans , Microscopy, ConfocalABSTRACT
Dielectrophoresis (DEP) is the motion of polarizable particles in the presence of nonuniform electric fields. This novel electrokinetic technique has successfully been employed in many miniaturized systems for the manipulation and detection of microbes. This review article depicts the application of dielectrophoresis for the monitoring of microorganisms in microfluidic devices for environmental applications. The research studies described here are mainly conceived for water- and air-monitoring assessments, and are classified considering the target aimed to detect, concentrate, and/or separate, including chemical and toxicant agents, and microorganisms ranging from virus to protozoa. Dielectrophoresis has also played an important role in biofilm formation studies. This review article comprises mainly studies published from 2000 to present. Even in this relatively short time frame, there have been many significant contributions of this powerful and nascent technique related to environmental monitoring; thus, unveiling its great potential for future research directions.
Subject(s)
Electrophoresis/methods , Environmental Microbiology , Environmental Monitoring/methods , Microfluidic Analytical Techniques/methods , Cryptosporidium parvum/chemistry , Giardia lamblia/chemistry , Spores, Bacterial/chemistry , Viruses/chemistry , Water Pollutants/analysisABSTRACT
Low frequency alternating current insulator-based dielectrophoresis is a novel technique that allows for highly controlled manipulation of particles. By varying the shape of an AC voltage applied across a microchannel containing an array of insulating cylindrical structures it was possible to concentrate and immobilize microparticles in bands; and then, move the bands of particles to a different location. Mathematical modeling was performed to analyze the distribution of the electric field and electric field gradient as function of the shape of the AC applied potential, employing frequencies in the 0.2-1.25 Hz range. Three different signals were tested: sinusoidal, half sinusoidal and sawtooth. Experimental results demonstrated that this novel dielectrophoretic mode allows highly controlled particle manipulation.
