A biosensor is an analytical device that consists of an immobilized biocomponent in conjunction with a transducer, and represents a synergistic combination of biotechnology and microelectronics. This review summarizes the use of biosensors for detecting and quantifying heavy metal ions. Heavy metal contamination is of serious concern to human health since these substances are non-biodegradable and retained by the ecological system. Conventional analytical techniques for heavy metals (such as cold vapour atomic absorption spectrometry, and inductively coupled plasma mass spectrometry) are precise but suffer from the disadvantages of high cost, the need for trained personnel and the fact that they are mostly laboratory bound. Biosensors have the advantages of specificity, low cost, ease of use, portability and the ability to furnish continuous real time signals. The analysis of heavy metal ions can be carried out with biosensors by using both protein (enzyme, metal-binding protein and antibody)-based and whole-cell (natural and genetically engineered microorganism)-based approaches.

a b s t r a c tA biosensor is an analytical tool that comprises two essential components-an immobilized biocomponent, in intimate contact with a transducer that converts a biological signal into a measurable electrical signal. This review summarizes the studies carried on the development of biosensors for the analysis of urea in different fields of application, the various techniques of immobilization of urease enzyme, the stability and response time characteristics and the transducers used for biosensor development such as pH electrodes, ammonia gas sensing electrodes, ammonium ion-selective electrodes, optical, conductometric and amperometric transducers. Underlying the importance of this study is the fact that urea is toxic above certain concentrations and its continuous real time monitoring in clinical, environmental and food related environments is of utmost interest. The conventional analytical techniques used, although precise, are time consuming and mostly laboratory bound whereas biosensors have the advantages of ease of use, portability and the ability to furnish real time signals.

Babesia parasites cause a malaria-like febrile illness by infection of red blood cells (RBCs). Despite the growing importance of this tick-borne infection, its basic biology has been neglected. Using novel synchronization tools, the sequence of intra-erythrocytic events was followed from invasion through development and differentiation to egress. The dynamics of the parasite population were studied in culture, revealing for the first time, the complete array of morphological forms in a precursor-product relationship. Important chronological constants including Babesia's highly unusual variable intra-erythrocytic life cycle, the life span of each population of infected cells and the time required for the genesis of the different parasite stages were elucidated. Importantly, the maintenance of specific ratios of the infected RBC populations was shown to be responsible for the parasites' choice of developmental pathways, enabling swift responses to changing environmental conditions like availability of RBCs and nutrition. These results could impact the control of parasite proliferation and therefore disease.

Two unique materials were developed, like graphene oxide (GO) sheets covalently grafted on to barium titanate (BT) nanoparticles and cobalt nanowires (Co-NWs), to attenuate the electromagnetic (EM) radiations in poly(vinylidene fluoride) (PVDF)-based composites. The rationale behind using either a ferroelectric or a ferromagnetic material in combination with intrinsically conducting nanoparticles (multiwall carbon nanotubes, CNTs), is to induce both electrical and magnetic dipoles in the system. Two key properties, namely, enhanced dielectric constant and magnetic permeability, were determined. PVDF/BT-GO composites exhibited higher dielectric constant compared to PVDF/BT and PVDF/GO composites. Co-NWs, which were synthesized by electrodeposition, exhibited saturation magnetization (Ms) of 40 emu/g and coercivity (Hc) of 300 G. Three phase hybrid composites were prepared by mixing CNTs with either BT-GO or Co-NWs in PVDF by solution blending. These nanoparticles showed high electrical conductivity and significant attenuation of EM radiations both in the X-band and in the Ku-band frequency. In addition, BT-GO/CNT and Co-NWs/CNT particles also enhanced the thermal conductivity of PVDF by ca. 8.7- and 9.3-fold in striking contrast to neat PVDF. This study open new avenues to design flexible and lightweight electromagnetic interference shielding materials by careful selection of functional nanoparticles.

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