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Purpose This review aims to focus on recent reported research work on the construction and function of different electrochemical DNA biosensors. It also describes different sensing materials, chemistries of immobilization probes, conditions of hybridization and principles of transducing and amplification strategies. Design/methodology/approach The human disease-related mutated genes or DNA sequence detection at low cost can be verified by the electrochemical-based biosensor. A range of different chemistries is used by the DNA-based electrochemical biosensors, out of which the interactions of nanoscale material with recognition layer and a solid electrode surface are most interesting. A diversity of advancements has been made in the field of electrochemical detection. Findings Some important aspects are also highlighted in this review, which can contribute in the creation of successful biosensing devices in the future. Originality/value This paper provides an updated review of construction and sensing technologies in the field of biosensing.

Influence of bath temperature and pH on the structure of electrodeposited cobalt nanowires To fully understand the mechanism of forming fcc Co in electrodeposition, the effect of bath temperature and pH on the structure of electrodeposited Co nanowires is studied by means of X-ray diffraction and scanning electron microscopy. At -3.0 V and pH 2.5, the fraction of fcc Co decreases with increasing temperature, ranging from 1 (25 8C, pure fcc Co) to 0 (45 8C, pure hcp Co). The formation of hcp Co can be attributed to larger critical clusters formed at higher temperatures. The pH value has no appreciable effect on the formation of fcc Co nanowires. This is because the H adatoms produced at the cathodic surface can penetrate quickly through the thin Au film and desorb into air.

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One of the big challenge of studying the core-shell iron nanostructures is to know the nature of oxide shell, i.e., whether it is γ-Fe2O3 (Maghemite), Fe3O4 (Magnetite), α-Fe2O3 (Hematite), or FeO (Wustite). By knowing the nature of iron oxide shell with zero valent iron core, one can determine the chemical or physical behavior of core-shell nanostructures. Fe core-shell nanochains (NCs) were prepared through the reduction of Fe3+ ions by sodium boro-hydride in aqueous solution at room atmosphere, and Fe NCs were further aged in water up to 240 min. XRD was used to study the structure of Fe NCs. Further analysis of core-shell nature of Fe NCs was done by TEM, results showed increase in thickness of oxide shell (from 2.5, 4, 6 to 10 nm) as water aging time increases (from 0 min, 120 min, 240 min to 360 min). The Raman spectroscopy was employed to study the oxide nature of Fe NCs. To further confirm the magnetite phase in Fe NCs, the Mössbauer spectroscopy was done on Fe NCs-0 and Fe NCs-6. Result shows the presence of magnetite in the sample before aging in water, and the sample after prolonged aging contains pure Hematite phase. It shows that prolonged water oxidation transforms the structure of shell of Fe NCs from mixture of Hematite and Magnetite in to pure hematite shell. The Magnetic properties of the Fe NCs were measured by VSM at 320 K. Because of high saturation magnetization (Ms) values, Fe NCs could be used as r2 contrasts agents for magnetic resonance imaging (MRI) in near future.

Several factors are involved in the emergence of antibiotic-resistant bacteria and pose a serious threat to public health safety. Among them, clustered regularly interspaced short palindromic repeat- (CRISPR-) Cas system, an adaptive immune system, is thought to be involved in the development of antibiotic resistance in bacteria. The current study was aimed at determining not only the presence of antibiotic resistance and CRISPR-Cas system but also their association with each other in Salmonella enteritidis isolated from the commercial poultry. A total of 139 samples were collected from poultry birds sold at the live bird markets of Lahore City, and both phenotypic and genotypic methods were used to determine antimicrobial resistance. The presence of the CRISPR-Cas system was determined by PCR, followed by sequencing. All isolates of S. enteritidis (100%) were resistant to nalidixic acid, whereas 95% of isolates were resistant to ampicillin. Five multidrug-resistant isolates (MDR) such as S. enteritidis isolate (S. E1, S. E2, S. E4, S. E5, and S. E8) were found in the present study. The CRISPR-Cas system was detected in all of these MDR isolates, and eight spacers were detected within the CRISPR array. In addition, an increased expression of CRISPR-related genes was observed in the standard strain and MDR S. enteritidis isolates. The association of the CRISPSR-Cas system with multiple drug resistance highlights the exogenous acquisition of genes by horizontal transfer. The information could be used further to combat antibiotic resistance in pathogens like Salmonella.

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