**4.3 Magnetic nanoparticles**

a.*Properties:* MNPs can be assimilated into transducer materials or scattered in the sample prior to being attracted to the active recognition surface of the sensor

*An Overview of the Synergy of Electrochemistry and Nanotechnology for Advancements… DOI: http://dx.doi.org/10.5772/intechopen.106151*

by an external magnetic field [57]. Because of the reduced number of magnetic domains in nanosized MNPs, these exhibit magnetic behaviours different than the bulk material, resulting in superparamagnetic behaviour. This means that in a very short time, magnetisation can rapidly and randomly flip directions, and when an external magnetic field is absent, the magnetisation denotes to be average zero. This is a temperature-dependent phenomenon which disappears when the magnetic moments are aligned by the application of an external magnetic field [58]. MNPs offer a highly sensitive technique of transduction in biosensors, optical sensors and electrochemical sensors [57, 58].

b.*Recent Research Trends:* In the recent times, the utility of MNPs has increased multifold. Some advanced sensing applications of MNPs are as follows: diagnosis of anticancer drug 6-mercaptopurine using cerium-based MNP as a fast-response and efficient fluorescence quenching sensor [59], Ihlamur leaves [60] and saffron flowers [61]-based biosynthesis of magnetic nanoparticles for antibacterial applications, use of silver MNPs to enhance the surface plasmon resonance signal for determination of leukocyte cell-derived chemotaxin-2 which is an important biomarker for the diagnosis of liver fibrosis [62], green synthesis of Fe3O4 nanoflakes and its utility as an electrocatalyst for the voltammetric determination of ascorbic acid [63], diversified biomedical applications of multifunctional MNPs [64], and many more.

### **4.4 Carbon nanotubes**


## **5. Role or functions of nanoparticles in (bio) sensing techniques**

The various roles of NPs in (bio) sensing techniques are as follows.


## iii.**Enhancement of electron transfer between electrode surfaces and proteins:**


*An Overview of the Synergy of Electrochemistry and Nanotechnology for Advancements… DOI: http://dx.doi.org/10.5772/intechopen.106151*

NPs (react directly with H2O2) in comparison with bulk MnO2 (catalyses decomposition of H2O2) has made these NPs an important component of some electrochemical systems [79].

### **6. Recent advances in nanotechnology-based biosensors**

Recently, techniques that are sensitive, selective, and cost-effective are being developed for detecting diseases and underlying medical issues. In this context, biosensors as nano-electroanalytical tools have taken the centre stage. Progress in the health sector enabled by nanotechnology has facilitated in the management of a number of diseases at an early stage [80]. When studying the electrosensing applications of NPs, transfer of electrons between substrate and active site of enzyme (biocatalyst) forms the basis for the functioning of enzymatic biosensors, and this transfer in turn is transduced to produce an electroanalytical signal [81]. Carbon nanostructures, nanotubes, nanorods, ceramic or polymeric matrices, derivatives of graphene, and other functionalised nanoparticles are some of the materials that have been explored and investigated widely by researchers for their electrosensing/ biosensing properties and applications [82–84]. The following recent researches further ascertain the efficiency and remarkable role of NPs in biosensors:

