Aptamer-Based Sensors for Detection of Proteins

The need for rapid biosensing methodologies spans a number of fields ranging from medical diagnostics, drug discovery, and homeland security. For example, the benefits of rapid biological detection can allow for earlier diagnosis and treatment of disease, as well as for an increased response time to a chemical or biological threat attack. Of particular interest is the development of sensing methodologies which are not only rapid, but are capable of specific and sensitive biological identification, and can be integrated into a multiplexed system for analysis of multiple target types on a single detection platform.

A biosensor fundamentally consists of a bioreceptor that specifically recognizes and binds to a target of interest, in combination with some form of transduction mechanism to convert the binding event to a measurable signal (1-3). The transduction mechanism can vary widely, depending on the needs of the application. Many use an optical transduction due to the ability to optically label biological recognition elements and perform a sensitive spectroscopic analysis. The bioreceptor can also function in a variety of formats with the most common being nucleic acid (hybridization) and antibody (immunological). In the case of nucleic acid hybridization, specific identification of another nucleic acid target is achieved through complementary base- pair matching, often of the genetic components of an organism (1). In the case of antibody-based sensing, specific recognition of an antigen component of an organism or surface epitope of an organism is responsible for the identification (1).

Although not commonly employed, nucleic acid aptamers are an emerging chemical and biological recognition approach that offers a number of advantages over traditional bioreceptors. Nucleic acid aptamers are single strands of ribonucleic acid (RNA) or deoxyribonucleic acid (DNA), typically 20-100 bases in length that are capable of specific binding to a variety of target types (e.g., chemicals, viruses, toxin, cells, spores) through a combination of shape complementarity and noncovalent chemical interactions (figure 1) (4-7). Although the mechanisms for specific binding are similar to antibody:antigen interactions, aptamers are amenable to reproducible mass production and do not require the use of animals. Other distinct advantages over antibody-based sensing include a greater stability for field use, and an ability to be easily chemically modified to allow for a variety of signaling schemes.