Immunosensor reusable

J.S. Li, Z.S. Wu, H. Wang, G.L. Shen, and R.Q. Yu, A reusable capacitive immunosensor with a novel immobilization procedure based on 1,6-hexanedithiol and nano-Au self-assembled layers. Sens. Actuators B 110, 327-334 (2005). 

Konig, B., and Gratzel, M. Long-term stability and improved reusability of a piezoelectric immunosensor for human erythrocytes. Anal. Chim. Acta 1993, 280, 37—41. 

The determination of antigens and antibodies can be improved by immobilization of the appropriate immunochemical partner of the analyte. When the immunological reaction can be rendered reversible the immobilized ligand becomes reusable. Whereas in immunoreactors the immunosorbent is separated from the sensor, in immunosensors both elements are in intimate physical contact. We shall show below that these devices can be used to perform the classical functions of immunoassays. 

The detection of complement proteins has also received much attention. Pei and coworkers described a Pz immunosensor for the detection of complement C4 [134,135]. The authors first used adsorption to immobilise the specific antibody, showing better results than for the use of polyethyle-nieimine [134]. They measured the protein linearly from 0.1 to 10 p.gmL The sensor showed no response to any materials present in serum and the gold surface could be regenerated 15 times for repeated use. Later they self-assembled the antibodies onto a layer of protein A, a method which gave superior results to the previously tested immobilisation procedures [135]. This setup gave a better linear range of 5 x 10 -1 x 10 p.gmL but the crystal was only reusable about ten times. 

SPR is a representative physical phenomenon that is widely utilized for label-free characterization of molecules on thin metal films. The basic principle and operation of SPR has been described in more detail in several review articles [77, 78]. The reports on SPR-based immune sensors have steeply increased for detection of analytes with low molecular weights in recent years. SPR detection in microfluidic systems can provide various advantages. Immunoreactions are completed within a short time due to small sample volumes down to the nanolitre scale. Kim et al. developed a simple and versatile miniaturized SPR immunosensor enabling parallel analyses of multiple analytes [79]. Their SPR sensor was claimed to exhibit good stability and reusability for 40 cycles and more than 35 days. Feltis et al. demonstrated a low-cost handheld SPR-based immunosensor for the toxin Ricin [80]. Springer et al. reported a dispersion-free microfluidic system with a four-channel SPR sensor platform, which considerably improved the response time and sensitivity [81]. The sensor was able to detect short sequences of nucleic acids down to a femtomole level for 4 min. Waswa et al. demonstrated the immunological detection of E. coli 0157 H7 in milk, apple juice, and meat juice extracted from... 

Yang, G.-J., Huang, J.-L., Meng, W.-J., Shen, M., and Jiao, X.-A. (2009) A reusable capacitive immunosensor for detection of Salmonella spp. based on grafted ethylene diamine and self-assembled gold nanoparticle monolayers. Anal Chim. Acta, 647, 159-166. 

Ideally, an immunosensor would be a reusable device, since the reversibiHty of the antigen—antibody interaction may allow regenerating the immobilized component. A high-affinity constant and a labile immobilized antibody, sensitive to the harsh conditions often required, make regeneration of the surface difficult to realize, limiting practical application of immunosensors to single-use devices (Reymond et al., 2007). In this chapter, we will present the basics of different types of immunosensors and their applications to in situ or point-of-care diagnosis. 

One major challenge for the use of immunosensors in airport security is that they use antibodies that, once bound to their constituent antigen, are generally not reusable (Holford et al., 2012). 

---