Fabrication and characterization of an highly selective fiber optic surface plasmon resonance based dopamine sensor using molecular imprinted graphene nanoaplatelets (GNP)/tin oxide (SnO2) nanocomposite have been reported. The synthesis of sensing layer has been carried out using a series of optimizations and morphological studies. The effectiveness of the sensing layer over other possible probe designs has been proved by performing control experiments for dopamine concentration range covering the suggested level of dopamine for human being. The limit of detection (LOD) of the sensor evaluated is 0.031 μM which is lower than the LOD values of various dopamine sensors fabricated using different methods. The specificity of the sensor for dopamine has been confirmed by performing experiments using various interferands while the stability and reusability of the sensor probe have been checked by performing experiments repeatedly for a long period of time. Apart from high sensitivity, low LOD and fast response, the sensor can be used for remote sensing and online monitoring of dopamine.

The fabrication and characterization of a surface plasmon resonance (SPR)-based urea biosensor, with thin silver (Ag), ITO (In₂O₃: SnO₂), and enzyme-trapped gel over an unclad portion of plastic-clad silica fiber as a sensing element, is represented. The working principle is to identify changes in the refractive index of the enzyme (urease) entrapped gel layer following the interaction with the incoming analyte. This interaction causes swelling and shrinkage of the gel layer, which alters the effective refractive index of the sensing layer. The wavelength interrogation method is used, and the optimized sensor probe is characterized by urea samples having different pH values. Scanning electron microscopy confirmed the uniformity of the silver layer over the unclad core of the fiber. The sensor operates from 0 to 160 mM of urea concentrations to cover the physiological concentration range of blood urea normally present in the human body. The sensitivity and limit of detection (LOD) offered by the sensor are marked 0.59387 nm/mM near zero concentration of the urea sample and 0.56 mM, respectively, along with the provisions of high stability, remote sensing, and online monitoring of urea. The proposed sensor has proven to be one of a kind due to its fast response time.

Throughout the central nervous system, the spinal cord plays a very important role, namely, transmitting sensory and motor information inwardly so that it can be processed by the brain. There are many different ways this structure can be damaged, such as through traumatic injury or surgery, such as scoliosis correction, for instance. Consequently, damage may be caused to the nervous system as a result of this. There is no doubt that optical devices such as microscopes and cameras can have a significant impact on research, diagnosis, and treatment planning for patients with spinal cord injuries (SCIs). Additionally, these technologies contribute a great deal to our understanding of these injuries, and they are also essential in enhancing the quality of life of individuals with spinal cord injuries. Through increasingly powerful, accurate, and minimally invasive technologies that have been developed over the last decade or so, several new optical devices have been introduced that are capable of improving the accuracy of SCI diagnosis and treatment and promoting a better quality of life after surgery. We aim in this paper to present a timely overview of the various research fields that have been conducted on optical devices that can be used to diagnose spinal cord injuries as well as to manage the associated health complications that affected individuals may experience.

A fiber optic SPR based cadmium sensor is proposed. The probe fabricated by coating layers of silver and SnO₂ nanoparticles over unclad core operates from 0 to 4 µM with detection limit of 14 nM.

Dopamine (DA) belongs to the catecholamine family of neurotransmitters and is very important for humans. It is produced in adrenal glands and several areas of the brain. Dopamine is formed by decarboxylation of DOPA and is a precursor of two other neurotransmitters adrenaline and noradrenalin. Dopamine is the most abundant of the catecholamine, hence affects many aspects of brain functionality such as movement, emotional response and ability to experience pain and pleasure. Dopamine also affects the cardiovascular and renal systems. Excessive secretion of DA (e.g., due to Huntington’s disease) is associated with failure in energy metabolism and causes untimely death. Differently low levels of dopamine in the central nervous system causes several neurological diseases, for example schizophrenia, Parkinson’s disease. Therefore, it is important to detect dopamine level efficiently in human body [1].