Biosensors for protein detection: A review

There is considerable demand for the rapid low-cost determination of proteins, particularly in the food and beverage industry. The most widely used tests are based on colorimetric procedures in which proteins react to produce colored complexes. These methods (Lowry et al. 1951; Bradford 1976; Gornall et al. 1949; Smith et al. 1985) are dependent upon a number of factors other than absolute protein quantity, including amino acid composition, protein purity, and association state. The successful application of these methods relies on using representative calibration standards. Time-consuming and complex methodologies such as the Kjeldahl technique and quantitative amino acid analysis procedures have been also reported. Apart from these methods, biosensors are interesting tools offering certain operational advantages over standard photometric methods, notably with respect to rapidity, ease-of-use, cost, simplicity, portability, and ease of mass manufacture. By appropriate recognition element selection, it is possible to detect either a particular target protein or a broad range of proteins. This review presents an overview of the different biological recognition elements and the various transduction systems that have been reported in the literature to design biosensors for protein detection. Examples are given to illustrate the different possibilities. It must be noticed that this review reports detection of proteins in solution and not proteins immobilized on membranes. Briefly, immobilized proteins can be detected by antibodies (Western blotting) or oligonucleotides such as aptamers (Eastern blotting) bearing reporter molecules, fluorescently labeled or radiolabeled.