Cancer Biosensors

Many of the above materials used to fight cancer have been incorporated into novel in situ sensors that can determine cancer cell presence. A biosensor able to detect cells would be an all-in-one dream device for such applications (de la Escosura-Muniz et al. 2009). Specifically, de la Escosura-Muniz et al. developed an electrocatalytic device for the specific identification of tumor cells that quantifies gold nanoparticles (AuNPs) coupled with an electrotransducing platform/sensor (Fig. 12). Proliferation and adherence of tumor cells were achieved on the electro-transducer/detector, which consists of a mass-produced screen-printed carbon

Fig. 12 SEM images of the electrotransducer (SPCE) (left) with its three surfaces and details of the (a) HMy2 and (b) PC-3 cell lines on the carbon working electrode (right). Inset images correspond to cell growth on the plastic area of the SPCEs

electrode (SPCE). In situ identification/quantification of tumor cells was achieved with a detection limit of 4,000 cells per 700 mL of suspension. This novel and selective cell-sensing device was based on the reaction of cell surface proteins with specific antibodies conjugated with AuNPs. Final detection required only a couple of minutes, taking advantage of the catalytic properties of AuNPs on hydrogen evolution. The proposed detection method did not require the chemical agents used in most existing assays for the detection of AuNPs. It allowed for the miniaturization of the system and has been reported to be much cheaper than other expensive and sophisticated methods used for tumor cell detection. De la Esocura-Muniz et al. envisaged that this device could operate in as simple of a way as an immunosensor or DNA sensor. Moreover, it could be used, even by inexperienced staff, for the detection of protein molecules or DNA strands.

In recent years, there have been some attempts at cancer cell analysis using optical-based biosensors. In addition to optical biosensors, sensitive electrochemical DNA sensors, immunosensors, and other bioassays have all recently been developed using nanoparticles (NPs) as labels and providing direct detection without prior chemical dissolution.

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Fig. 13 Fluorescence microscopy images of Hoechst 33342 and propidium iodide-stained MCF-7 cells cultured on the magnetoelastic sensor recorded under ultraviolet (top) and green light irradiation (bottom), respectively

Fig. 13 Fluorescence microscopy images of Hoechst 33342 and propidium iodide-stained MCF-7 cells cultured on the magnetoelastic sensor recorded under ultraviolet (top) and green light irradiation (bottom), respectively

Moreover, wireless cancer cell detection devices have been developed (Xiao et al. 2008). Specifically, a wireless sensing device was developed for the in situ monitoring of the growth of human breast cancer cells (MCF-7) and evaluation of the cytotoxicity of the anticancer drugs fluorouracil and cisplatin (Fig. 13). The sensor was fabricated by coating a magnetoelastic ribbon-like sensor with a layer of polyurethane that protects the iron-rich sensor from oxidation and provides a cell-compatible surface. In response to a time-varying magnetic field, the magne-toelastic sensor longitudinally vibrates, emitting a magnetic flux that can be remotely detected by a pick-up coil. No physical connections between the sensor and the detection system were required. This wireless capability facilitated aseptic biological operation, especially in cell culture as illustrated in this work. The adhesion of cells on the sensor surface resulted in a decrease in the resonance amplitude, which is proportional to the cell concentration. A linear response was obtained in cell concentrations of 5 x 104 to 1 x 106 cells ml-1, with a detection limit of 1.2 x 104 cells ml-1. The adhesion strength of cells on the sensor was qualitatively evaluated by increasing the amplitude of the magnetic excitation field and the cytotoxicity of the anticancer drugs fluorouracil and cisplatin was evaluated by the magnetoelastic biosensor. The cytostatic curve was related with the quantity of cytostatic drug. The lethal concentration (LC50) for cells incubated in the presence of drugs for 20 h was calculated to be 19.9 mM for fluorouracil and 13.1 mM for cisplatin.

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