Development of sandwich-form biosensor to detect Mycobacterium tuberculosis complex in clinical sputum specimens

AbstractMycobacterium tuberculosis, the causing agent of tuberculosis, comes second only after HIV on the list of infectious agents slaughtering many worldwide. Due to the limitations behind the conventional detection methods, it is therefore critical to develop new sensitive sensing systems capable of quick detection of the infectious agent. In the present study, the surface modified cadmium-telluride quantum dots and gold nanoparticles conjunct with two specific oligonucleotides against early secretory antigenic target 6 were used to develop a sandwich-form fluorescence resonance energy transfer-based biosensor to detect M. tuberculosis complex and differentiate M. tuberculosis and M. bovis Bacille Calmette–Guerin simultaneously. The sensitivity and specificity of the newly developed biosensor were 94.2% and 86.6%, respectively, while the sensitivity and specificity of polymerase chain reaction and nested polymerase chain reaction were considerably lower, 74.2%, 73.3% and 82.8%, 80%, respectively. The detection limits of the sandwich-form fluorescence resonance energy transfer-based biosensor were far lower (10fg) than those of the polymerase chain reaction and nested polymerase chain reaction (100fg). Although the cost of the developed nanobiosensor was slightly higher than those of the polymerase chain reaction-based techniques, its unique advantages in terms of turnaround time, higher sensitivity and specificity, as well as a 10-fold lower detection limit would clearly recommend this test as a more appropriate and cost-effective tool for large scale operations

Preparation of zinc oxide nanoparticles by laser ablation in various liquid media

A big challenge in the synthesis of nanoparticles (NPs) is particle agglomeration. This tendency can be inhibited by stabilization of NPs and therefore much effort by researchers has been undertaken to use different liquid media as stabilizers. In the present study we have investigated the fabrication of zinc oxide nanoparticles (ZnO-NPs) using Laser Ablation (LA) technique. The first objective is studying the effect of laser parameters on fabrication of ZnO-NPs and secondly investigating the medium effect on optical properties and size of ZnO-NPs. The LA to ZnO plate was carried out in various media such as distilled water, polyvinyl acetate aqueous solution, ethylene glycol, and rice bran oil, and then characterized by UV-vis, photoluminescence (PL), FT-IR spectroscopy, and TEM microscopy. It was revealed the generation of NPs by LA in various liquid media was higher in comparison with in distilled water. The increased NPs generation is attributable to solvent plasma confinement toward the plate. In addition, at longer ablation duration the size decrease of NPs was remarkable. The UV-vis absorption spectra of the ZnO-NPs are monitored to characterize the particle growth because the onset of absorption is associated with the particle size. It is observed that average NPs size decreases with the increase of ablation time. The decrement can be explained by the way that at longer ablation time, there is an increment of produced NPs from the plate since more interactions occurred between target and laser light. NPs with different sizes demonstrate different optical properties; when the particle diameter decreased there is a blue-shifted in absorption spectra. It can be observed that increasing repetition rate lead to larger particle diameter. This size increment is confirmed by the red-shifted absorption spectra. We analyzed PL spectra to see the emission spectra of fabricated NPs. Both the absorption and emission band positions are dependent on the polarity of the medium; in the medium the PL spectrum is much more sensitive than the absorption spectrum. PL spectra of all fabricated ZnO-NPs show two emission peaks; the first one is sharp and narrow UV emission corresponds to excitonic emission and the second one is broad blue-green emission commonly referred to a deep-level or a trap-state emission attributed to the singly ionized oxygen vacancy of ZnO. TEM images also show the morphology of the ZnO-NPs as they were all spherical. The produced ZnO-NPs in rice bran oil were well dispersed; those fabricated in polyvinyl acetate were more stable than other liquid media. Ethylene glycol has ability to prevent agglomeration of NPs. The average diameter of the obtained ZnO-NPs in distilled water was large; 27.12 nm, on the other hand rice bran oil leads to fabricate fine ones; 14.17 nm

Treatment of mature landfill leachate by chemical precipitation and Fenton advanced oxidation process

Background: Mature landfill leachate is a complicated mixture which is resistant to biological treatment processes. The treatment of mature landfill leachate by struvite precipitation and Fenton oxidation was the main objective of the current research. Methods: Struvite with the phosphate/ammonia/magnesium molar ratio of 1/1/1.05 was considered during all experiments. Five initial pHs of 3, 4, 5, 6, and 7, four different H2O2/Fe mass ratios of 50, 100, 200, and 400, and reaction times of 20, 40, 80, 120, and 160 minutes were examined for the Fenton oxidation process. Results: A leachate sample with average chemical oxygen demand (COD), BOD5, and NH4 concentrations of 7350, 2220, and 2280 mg L-1, respectively, and a BOD5/COD ratio of 0.3 was introduced to the chemical precipitation unit. An NH4 removal efficiency of 87% was obtained at pH 8.5 for struvite precipitation. Under optimum conditions of Fenton oxidation, including pH 3, an H2O2/Fe2+ mass ratio of 200, and a reaction time of 160 min, more than 95% COD and BOD5 removal was observed. Conclusion: Struvite precipitation and Fenton oxidation are reliable and efficient alternatives for mature landfill treatment

Upconversion Properties of the Er-Doped Y2O3, Bi2O3 and Sb2O3 Nanoparticles Fabricated by Pulsed Laser Ablation in Liquid Media

Er-doped Y2O3, Bi2O3 and Sb2O3 nanoparticles are synthesized using pulsed laser ablation in a liquid. Ceramic targets of Y2O3:Er3+, Bi2O3:Er3+ and Sb2O3:Er3+ for ablation process are prepared by standard solid-state reaction technique and ablation is carried out in 5-ml distilled water using nanosecond Q-switched Nd:YAG laser. The morphology and size of the fabricated nanoparticles are evaluated by transmission electron microscopy and the luminescence emission properties of the prepared samples are investigated under different excitation wavelengths