Detection of magnetic microbeads and ferrofluid with giant magnetoresistance sensors

A novel HBV genotypes detecting system combined with microfluidic chip, loop-mediated isothermal amplification and GMR sensors

Genotyping of hepatitis B virus (HBV) can be used for clinical effective therapeutic drug-selection. A novel microfluidic biochip for HBV genotyping has been fabricated, for the first time, integrating loop-mediated isothermal amplification (LAMP), line probes assay (LiPA) and giant magnetoresistive (GMR) sensors. Coupling LAMP with LiPA in microfluidic chip shortened reaction time substantially, and combining LAMP with GMR sensor enabled limit of detection to attain 10 copies mL(-1) target HBV DNA molecules in 1 h. Furthermore, the independent designed GMR sensors and microfluidic chip can decrease manufacturing cost and patient's test-cost, and facilitate GMR detector repeating use for signal detection. In addition, the detection system has a lower background signal owing to application of superparamagnetic nanoclusters. And it can be expected to use for multiple target molecules synchronous detection in microfluidic chip based on a characteristic of stationary reaction temperature of LAMP. In conclusion, the neoteric detecting system is well suitable for quick genotyping diagnosis of clinical HBV and other homothetic biomolecule detection in biological and medical fields.

Microfluidic biosensing systems using magnetic nanoparticles

In recent years, there has been rapidly growing interest in developing hand held, sensitive and cost-effective on-chip biosensing systems that directly translate the presence of certain bioanalytes (e.g., biomolecules, cells and viruses) into an electronic signal. The impressive and rapid progress in micro- and nanotechnology as well as in biotechnology enables the integration of a variety of analytical functions in a single chip. All necessary sample handling and analysis steps are then performed within the chip. Microfluidic systems for biomedical analysis usually consist of a set of units, which guarantees the manipulation, detection and recognition of bioanalytes in a reliable and flexible manner. Additionally, the use of magnetic fields for performing the aforementioned tasks has been steadily gaining interest. This is because magnetic fields can be well tuned and applied either externally or from a directly integrated solution in the biosensing system. In combination with these applied magnetic fields, magnetic nanoparticles are utilized. Some of the merits of magnetic nanoparticles are the possibility of manipulating them inside microfluidic channels by utilizing high gradient magnetic fields, their detection by integrated magnetic microsensors, and their flexibility due to functionalization by means of surface modification and specific binding. Their multi-functionality is what makes them ideal candidates as the active component in miniaturized on-chip biosensing systems. In this review, focus will be given to the type of biosening systems that use microfluidics in combination with magnetoresistive sensors and detect the presence of bioanalyte tagged with magnetic nanoparticles.

Quick genotyping detection of HBV by giant magnetoresistive biochip combined with PCR and line probe assay

Genotyping of human hepatitis B virus (HBV) can be used to direct clinically effective therapeutic drug-selection. Herein we report that a quick genotyping method for human HBV was established by a specially designed giant magnetoresistive (GMR) biochip combined with magnetic nanoclusters (MNCs), PCR and line probe assay. Magnetic nanoclusters of around 180 nm in diameter were prepared and modified with streptavidin, and resultant streptavidin-modified magnetic nanoclusters were used for capturing biotin-labeled hybrid products on the detection interface of the sensor. The gene fragments of HBV's B and C gene types were obtained by PCR based on a template of B- and C-type plasmids. After gene fragments were hybridized with captured probes, streptavidin-modified magnetic nanoclusters could bind with biotin-conjugated gene fragments, and the resultant hydride products could be quickly detected and distinguished by the GMR sensor, with a detection sensitivity of 200 IU mL(-1) target HBV DNA molecules. The novel method has great potential application in clinical HBV genotyping diagnosis, and can be easily extended to other biomedical applications based on molecular recognition.