Alzheimer's disease (AD) is one of the most common neurodegenerative illnesses displaying the highest death rate in the elderly. However, the existing AD diagnostic system remains elusive due to lack of a technology that may ensure enough sensitivity and reproducibility, detection accuracy, and specificity. Herein, a straightforward approach is reported to realize lab‐on‐fiber (LoF) technology for AD biomarker detection based on a D‐shaped single‐mode fiber combined with nanometer‐scale metal‐oxide film. The proposed sensing system, which permits the generation of lossy‐mode resonance (LMR), remarkably increases the evanescent field of light guided through the fiber, and hence the fiber‐surrounding medium interaction. Moreover, such optical sensors are highly repeatable in results and can safely be embedded into a compact and stable microfluidic system. Herein, the specific detection of Tau protein (as one of the classical AD biomarkers that is highly correlated with AD progression) in a complex biofluid with a detection limit of 10−12 m and over a wide concentration range (10−3–10 μg mL−1) is successfully demonstrated. The proposed LoF biosensor is an appealing solution for rapid, sub‐microliter dose and highly sensitive detection of analytes at low concentrations, hereby having the potential toward early screening and personalized medicine in AD.

DNA is becoming increasingly important in the domain of optical fiber sensors, either as a tool for biosensing, or as a target to detect. In this review the main contributions of the last years are presented both in the domain of wavelength and intensity based configurations. This review comprises the use of natural single strand DNA (ssDNA) sequences as receptors for the detection of ssDNA sequences through hybridization, synthetic nucleic acids receptors for detection of complementary ssDNA sequences, and sensors based on natural and synthetic ssDNA receptors used for the detection of non-DNA targets. Parameters such as sensitivity, detection range and limit of detection are analyzed and discussed in detail to the purpose of comparing the different technologies and knowing the future lines to follow in the domain of fiber optic DNA-based sensors.