Electroanalytical and surface plasmon resonance sensors for detection of breast cancer and Alzheimer's disease biomarkers in cells and body fluids
Cancer and neurological disorders are two leading causes of human death. Their early diagnoses will either greatly improve the survival rate or facilitate effective treatments or modalities. Detection of biomarkers in body fluids and some tissues (e.g., blood, urine and cerebrospinal fluids) is relatively non-invasive and provides useful chemical and biological information that is complementary to tomographic imaging (e.g., magnetic resonance imaging, positron emission tomography and X-ray computed tomography). Recent years have witnessed the contributions from and potential applications of bioanalytical methods for early detection of major diseases. In this review, we survey some recent developments of electroanalytical (as a representative label-based technique) and surface plasmon resonance (SPR) (as a representative label-free technique) biosensors for detection of biomarkers relevant to etiologies of breast cancer and Alzheimer's disease (AD). While breast cancer is representative of cancers of complexity (multiple biomarkers, false positives from tomographic scans, and a need for more effective early diagnostic methods), AD is the most prevalent neurological disorder that is also linked to multiple biomarkers. Both electroanalytical and SPR-based sensors have attractive features of sensitivity, portability, obviation of large sample volumes, and capability of multiplexed detection. Various sensing protocols developed in the past five years are reviewed, demonstrating the feasibility of both techniques for diagnostic purposes. Problems inherent in these two techniques that must be overcome before being clinically viable are also discussed.