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São José dos Campos, Brazil

Chung Y.-C.,National Taiwan University | Hsieh W.-Y.,Industrial Technology Research Institute of Taiwan | Young T.-H.,National Taiwan University | Young T.-H.,Institute of Biomedical Engineering

Ternary nanoparticles with negatively charged surface were prepared by coating single-stranded oligonucleotides (5′-C10A20-3′) on histidine-conjugated polyallylamine (PAA-HIS)/DNA complexes for gene delivery. Characterization of PAA-HIS/DNA/oligonucleotide complexes demonstrated that nanoparticles possessed the negative surface charge -27 mV and size of around 100 nm when the molar ratio of oligonucleotide/PAA-HIS exceeded 1.5. The negatively charged oligonucleotide-coated PAA-HIS/DNA complexes could be entirely internalized by the living HeLa cells to exhibit high gene expression with low cytotoxicity and the resistance against erythrocyte agglutination and serum inhibition. Since the gene expression of PAA-HIS/DNA complexes was significantly inhibited by coating other polyanions and oligonucleotides, the ternary PAA-HIS/DNA/deoxyadenosine-rich oligonucleotide complexes were uptaken by specific receptor-mediated process. Additionally, the deposition of a layer of oligonucleotides onto the binary PAA-HIS/DNA complexes could effectively transfect various types of cells including HEK-293, HepG2 and Hs68 cells, indicating the technology of coating specific oligonucleotides on PAA-HIS/DNA complexes or other cationic binary DNA complexes might facilitate the use of nanoparticles for safe and efficient gene delivery and eventual therapy. © 2010 Elsevier Ltd. All rights reserved. Source

Although navigation control has been applied in a multitude of environments, relatively little is known about the challenges and issues of navigation control in the vascular network. In an adult human, the vascular network consists of nearly 100,000 km of blood vessels, with diameters ranging from a few millimeters in the artery to just a few micrometers in the capillaries, and blood flow rates ranging from a few tens of centimeters per second to a few millimeters per second. Although vascular networks present great challenges, due to various environmental conditions, they are of special interest in medical microrobotics since they allow navigable agents to be delivered anywhere within the body. Controlled endovascular navigation would allow targeted surgical, diagnostic, and therapeutic interventions. In cancer therapy, for instance, although many of the most deadly cancers are initially located in a single region, modern therapies such as chemotherapy continue to inject excessive amounts of toxic agents thecirculate systematically throughout the vascular network. In general, only a tiny fraction of the drug reaches the treatment region [1]. Even the level of targeting achieved by agents with special coatings to enhance tumor cell specificity is far from optimal when they are injected systematically in the vascular network. Since the therapeutics do not discriminate between cancerous and healthy cells, systemic circulation of these agents must be avoided to eliminate, or at least minimize, secondary toxicity that affects healthy organs. © 2013 IEEE. Source

Yang D.,Industrial Materials Institute of Canada | Lu H.-H.,Institute of Biomedical Engineering | Chen B.,Industrial Materials Institute of Canada | Lin C.-W.,Institute of Biomedical Engineering
Sensors and Actuators, B: Chemical

Surface Plasmon resonance (SPR) sensor technology has great potential for detection and analysis of chemical and biochemical substances in many important areas including medicine, environmental monitoring, biotechnology, drug and food monitoring. Chemical sensing using SPR responses of semiconducting metal oxide films deposited on top of noble metal thin films could offer a simple, sensitive and reliable method for the detection of low concentration of gases. In this article, ultra-thin SnO2/Au bi-layer films of various thicknesses were deposited by pulsed laser deposition technique on BK7 glass substrates and their SPR responses were measured in the Kretschmann geometry of attenuated total reflection using a polarized light beam at 633 nm wavelength. The widths of the SPR dip and SPR angles were investigated as the function of the SnO2 and Au layer thickness and the wavelength of excited laser light in order to find the optimized structural parameters for SPR gas sensors based on SnO2/Au bi-layer films. The SPR responses of bi-layer films were also simulated with Macleod's general characteristic matrices method in order to compare with experimental data. The simulated results show the similar trend as the experimental date in term of the dependence of SPR angle and width with Au and SnO2 layer thickness, however, discrepancy between the simulated results and experimental data does existed, particularly, the shape of SPR response predicted by the theory is much broader than the experimental results. The SPR responses of the SnO2/Au bi-layer films upon 50 or 100 ppm NO gas exposure were measured and the primary results indicated that gas sensing using the SPR responses of the SnO2/Au bi-layer films is feasible. Crown Copyright © 2010. Source

Hu Y.,Institute of Biomedical Engineering | Georgiou P.,Institute of Biomedical Engineering
IEEE Transactions on Biomedical Circuits and Systems

This paper presents a robust, low-power and compact ion-sensitive field-effect transistor (ISFET) sensing front-end for pH reaction monitoring using unmodified CMOS. Robustness is achieved by overcoming problems of DC offset due to trapped charge and transcoductance reduction due to capacitive division, which commonly exist with implementation of ISFETs in CMOS. Through direct feedback to the floating gate and a low-leakage switching scheme, all the unwanted factors are eliminated while the output is capable of tracking a pH reaction which occurs at the sensing surface. This is confirmed through measured results of multiple devices of different sensing areas, achieving a mean amplification of 1.28 over all fabricated devices and pH sensitivity of 42.1 mV/pH. The front-end is also capable of compensating for accumulated drift using the designed switching scheme by resetting the floating gate voltage. The circuit has been implemented in a commercially-available 0.35 μ m CMOS technology achieving a combined chemical and electrical output RMS noise of 3.1 mV at a power consumption of 848.1 nW which is capable of detecting pH changes as small as 0.06 pH. © 2014 IEEE. Source

Woods S.P.,Institute of Biomedical Engineering | Woods S.P.,Duckworth and Kent Ltd. | Constandinou T.G.,Institute of Biomedical Engineering
IEEE Transactions on Biomedical Engineering

This paper describes a platform to achieve targeted drug delivery in the next-generation wireless capsule endoscopy. The platform consists of two highly novel subsystems: one is a micropositioning mechanism which can deliver 1 ml of targeted medication and the other is a holding mechanism, which gives the functionality of resisting peristalsis. The micropositioning mechanism allows a needle to be positioned within a 22.5 ° segment of a cylindrical capsule and be extendible by up to 1.5 mm outside the capsule body. The mechanism achieves both these functions using only a single micromotor and occupying a total volume of just 200 mm3. The holding mechanism can be deployed diametrically opposite the needle in 1.8 s and occupies a volume of just 270 mm 3. An in-depth analysis of the mechanics is presented and an overview of the requirements necessary to realize a total system integration is discussed. It is envisaged that the targeted drug delivery platform will empower a new breed of capsule microrobots for therapy in addition to diagnostics for pathologies such as ulcerative colitis and small intestinal Crohn's disease. © 1964-2012 IEEE. Source

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