Chemical nose sensors: an alternative strategy for cancer diagnosis

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Date: Mar. 2013
From: Expert Review of Molecular Diagnostics(Vol. 13, Issue 2)
Publisher: Expert Reviews Ltd.
Document Type: Report
Length: 1,765 words
Lexile Measure: 1320L

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Author(s): Ngoc DB Le 1 , Subinoy Rana 2 , Vincent M Rotello 3 *

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array-based sensing; cancer cell; nanoparticle; tissue; unbiased

Cancer diagnoses come in two forms: Does the patient have cancer? and What kind of cancer (i.e., phenotype) is present? Both questions are important; however, the answer to the second question is what dictates the course of therapy to be used. Conventional cancer detection methods rely on 'lock and key' recognition of specific biomarkers to provide diagnostic information. This biomarker-based approach is complicated by the highly variable and plastic nature of tumors. For example, prostate-specific antigen is an important marker for prostate cancer; unfortunately, its concentration level is similar in both benign and malignant tumors [1] . Very often, one or two biomarkers are not adequate to detect different cancer types [2,3] , making the choice of therapy a hit-or-miss affair.

Profiling the overall physicochemical changes in tumor cells provides an alternative strategy to cancer diagnostics. One approach is to use 'chemical nose' array sensors, where selective interactions between the sensors and analytes generate distinct patterns [4] , analogous to our own sense of smell. Just like with our own noses, chemical nose sensors do not require a previous knowledge of the analytes and are instead 'trained' to recognize analytes [5,6] . Array-based sensors have been used widely in detecting different chemicals ranging from volatile organic compounds, amino acids, proteins and carbohydrates [7-10] . More recently, this approach has been extended to more complex systems, including bacterial [11] and mammalian cell surfaces [12-15] . The author recently developed an unbiased gold nanoparticle-based array sensor to detect cancer cells as well as complex tumor tissues [16] . Until recently, however, this approach has not been applied to actual tumor diagnosis, a much more complicated system.

Array-based sensor designs & principles

Biosensors have two functional components: recognition elements and transducers. Recognition elements are used to recognize and bind to the target analytes. Nanomaterials, specifically, gold nanoparticles (AuNPs), provide a versatile scaffold for recognition elements, owing to their large surface area that facilitates multivalent interactions of the AuNPs with the analytes. AuNPs also possess the tunable surface functionalities required for selective binding, a prerequisite to 'nose'-based strategies. Direct transduction of the binding of AuNPs is challenging; however, they feature strong quenching ability due to the gold core [17] . This photophysical property enables the use of fluorescent displacement assays, where displacement of a fluorophore from the recognition element signals the binding event [18] . We found excellent candidates as a transducer such as poly(p-phenylene-ethynylene) (PPE) and green fluorescent protein (GFP) [12,13] . More recently, sensing systems have been designed using one species with a dual role of recognition element and transducer, such as magnetic glyconanoparticle...

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Gale Document Number: GALE|A321864201