Microfl uidic Biosensors for Thyroglobulin Detection and

Abstract

Thyroid cancers are the most common malignant tumor associated with the endocrine system. During the past several decades, thyroid cancer has been diagnosed with increasing frequency in clinical practice (Haugen 2005). Up to 90% of all these cases are classifi ed as differentiated thyroid cancer DTC (Rodrigo et al. 2006). DTC includes papillary and follicular cancers, both of which are derived from the follicular epithelium. Papillary thyroid cancers PTCs are more common, and constitute up to 85% of all cases. PTCs are often multifocal and usually metastasize to cervical lymph nodes. Follicular thyroid cancers FTCs are typically solitary and are largely encapsulated. FTCs are single, and more likely to metastasize to distant sites such as the lungs and skeleton. Both PTCs and FTCs are more common in women than men; the ratio is roughly 3:1. Early DTCs often do not generate vivid symptoms. As tumor cells grow, some symptoms are developed, yet they still do not directly signal thyroid cancer. Such diffi culties led to combining several diagnostic methodologies, such as ultrasonography, scintigraphy, and fi ne-needle aspiration biopsy FNA for accurate diagnosis. These diagnostic methods are, however, bulky and costly. They require expertize and time-consuming processes, and include a number of procedures patients fi nd painful. In the past several years, signifi cant progress has been accomplished uncovering thyroidspecifi c biomarkers in human blood, such as thyroglobulin Tg. These biomarkers can be used as supplementary data to assist disease diagnosis. Recent advancements in biomarker identifi cation support possibilities for clinical diagnosis at the point of care POC; the developments suggest potentially fast, simple and inexpensive tests for many diseases are now commercially available (Wu et al. 2007). The advent of microfl uidic systems has revolutionized the methodology for the POC test. Microfl uidic systems allow miniaturization of fl uidic domains to create unprecedented access to monitor/detect biomolecules of interest. Such features have led integrated advanced biosensors into lab-on-a-chip systems. The combined application using biosensors and microfl uidic technology could create a new generation of portable, fully automated POC test kits (Choi et al. 2011). The stringent requirements of POC testing, however, offer new challenges for biosensor technologies. Detecting target analytes with high sensitivity and selectivity,for instance, is a key challenge in microfl uidics-based POC devices because of their signifi cantly reduced sample volume.