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    • Agglutination of RBCs hemagglutination is caused

    2018-10-30

    Agglutination of RBCs (hemagglutination) is caused by an immune reaction between the RBCs and ap4 against the corresponding blood type. In conventional blood typing methods, hemagglutination caused by antibodies is detected by human eyes or by imaging techniques. Alternate methods of blood typing using optical techniques have also been reported. Quinn et al. first reported the use of a surface plasmon resonance (SPR) sensor for blood typing [1]. The SPR sensor is a sensitive biosensing instrument based on electrical field enhancement by SPR excitation [2–4]. SPR-based blood typing has been previously performed using the Biacore system [1,5,6] or an SPR imaging technique [7]. Narayanan et al. have reported a technique for absorbance measurement-based blood typing [8]. This group reported the detection of a weak agglutination reaction of A2 subtype and weak-D. Robb et al. demonstrated fluorescence-based blood typing on a planar microarray platform [6]. In another approaches, blood typing have been performed using a microchannel [9–11] or paper [12,13].
    Materials and methods
    Results and discussion
    Conclusion
    Conflict of interest
    Acknowledgements This study was supported by SENTAN, Japan Science and Technology Agency (JST). Original wafers of the waveguide-mode sensor chips were supplied by Advanced Functional Materials Research Center of Shin-Etsu Chemical Co., Ltd.
    Introduction Proteases play a crucial role in the control of physiological processes including wound healing [1], tissue remodeling [2,3] cell migration [4], and immune response [5]. Disruption of their activity is implicated in many pathologies and diseases [6–9]. Therefore, quantification of proteolytic activity in biological samples and tissues is of utmost interest for medical diagnoses and drug development [10]. In this perspective, a large variety of detection schemes have been developed, principally based on fluorescence [11–13]. Despite their high sensitivity, these assays often require time-consuming sample preparation and long incubation times. This reduces efficiency and can affect enzyme activity. In addition, they necessitate sophisticated laboratory equipment. In a different approach, researchers have focused on the development of single-use sensors to be available as point-of-care devices. Promising systems have thus been reported based on the erosion of thin protease substrate films [14–19]. By depositing the film on an appropriate transducer (electrochemical, piezo-electric, optical), the degradation process can be converted into a quantifiable signal in real-time. For example, poly(ester amide) films were used for the detection of chymotrypsin using a combination of quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS) [14], by surface plasmon resonance (SPR) [17], or scanning photoinduced impedance microscopy (SPIM) [15]. However these systems require extraction of biological samples, and often involve complex fabrication processes or measurement setups which preclude their clinical use. In order to provide rapid assessment of protease activity directly in biological samples (i.e. in situ), we developed a portable system based on optical fibers as transducers to monitor the enzymatic degradation of thin polymer films. Detection relies on evanescent wave (EW) absorption to probe the degradation of a stained substrate film replacing a portion of the fiber cladding. This approach offers several advantages. The existence of the EW only close to the fiber surface allows detection even in highly absorbing media and in very small volumes. Detection is performed by measuring variation in transmitted light intensity, which can be achieved using simple optical and optoelectronic components. As opposed to EIS-based systems which are limited to materials with good insulating properties [20], this versatile approach is suitable to any kind of natural or synthetic substrates (provided a refractive index lower for the film than for the core). Due to their small size and flexibility, fiber-optic sensors are furthermore adapted for the realization of miniaturized systems capable of remote sensing. In addition, they are immune to external electromagnetic interferences and safer due to the absence of circulating current like in electrode-based systems, which encourages their use in clinical applications [21,22]. Fiber-optic sensors have been successfully implemented for the detection of analytes such as pH [23,24], oxygen [25,26], glucose [27,28], and bacteria [29]. However, this is to our knowledge the first report on their use to quantify protease activity.