Cellulose sensor devices

An efficient system for the production of recombinant antibodies is cellulose-assisted refolding technology, as described by Berdichevsky et al. [7]. The expressed scFvs were fused to a cellulose-binding domain (CBD) from the bacterium Clostridium thermocellum in the format scFv-CBD. The resulting fusion proteins were obtained in high yield from bacterially produced inclusion bodies that become solubilized and then refold while immobilized on cellulose. The refolded and purified scFv-CBD fusion proteins can be used to form cellulose-based affinity matrices or, as described herein, can be immobilized on a cellulose matrix that makes up part of the immunoelectrochemical sensor device. 

Figure 3.44a shows FPW sensor response to toluene vapor [68]. The sorptive coating was a l.S-/im-thick layer of poly(dimethylsiloxane), PDMS. The sorptive polymer was in its rubbery state at the measurement temperature of 24 C. Very linear response was observed (Figure 3.44b). A different FPW device tp-erating at 2.8S MHz and having a 0.5-/u.m-thick coating of ethyl cellulose, which was expected to be better suited to toluene detection [70], had a measured mass sensitivity of S = 1064 cm /g. Its estimated minimum detectible concentration was 70 ppb, based on an assumed 3 1 signal-to-noise ratio and die measured short-term frequency instability of 0.04Hz.

HPTS covalently inunobilized on cellulose granules and with a p, of 7.1 is now used as the pH indicator in the Gas Stat device (Cardiovascular Devices Inc.) for continuous measurements on the extra-corporeal circuit. The pH sensor is generally associated with pCOj and PO2 measurements in a single catheter [50], which consists of three 125-pm fibers with appropriate chemistries at their ends [51]. 

Following the initial feasibility studies of Lubbers and Opitz, Cardiovascular Devices (GDI, USA) developed a GasStat extracorporeal system suitable for continuous online monitoring of blood gases ex vivo during cardiopulmonary bypass operations. The system consists of a disposable plastic sensor connected inline with a blood loop through a fiber optic cable. Permeable membranes separate the flowing blood from the system chemistry. The C02-sensitive indicator consists of a fine emulsion of a bicarbonate buffer in a two-component silicone. The pH-sensitive indicator is a cellulose material to which hydroxypyrene trisulfonate (HPTS) is bonded covalently. The 02-sensitive chemistry is... 

There are a variety of paper materials available to the user, although the choice is based mainly on the fabrication steps required in developing a device and also on the specific application area. In the development of sensors and microfiuidic technologies, filter paper has seen widespread use in recent years for producing paper-based sensors due to its wicking ability (Li et al. 2010 Martinez et al. 2010). In particular, the Whatman cellulose range is popular with the important parameters of porosity, particle retention, and flow rate differentiating the filter paper types. 

Paper has been used as a substrate for writing or recording information for 2000 years. Continuation of its use to date is due to the fact that its primary component, cellulose, is a ubiquitous, biodegradable, flexible, renewable, and inexpensive biopolymer. Although paper has been used extensively for printing, writing, and packaging, alternative innovative uses have received much attention within the past 10 years. For instance, processes to fabricate transistors [1,2], batteries and supercapacitors [3,4], sensors [5,6], and microfluidic devices [7-10] on paper substrates have been reported. Unfortimately, the inherently hydrophilic and oleophilic properties of paper limit its ultimate usefulness in many potential applications. 

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