The organic solvent in the sample may also interfere with the icELISA. Sample dilution is a frequently used method to reduce the interference effects on ELISA analysis. Although the high sensitivity of the mAb can afford for up to 200,000-, 400,000-, and 10,000-fold dilutions for the DHA, ATS, and ATM drug samples, respectively, matrix effects on the assay accuracy were evaluated using the spike studies before analysis of drug samples. An amount of 2 mg/mL extracted ART-based drug samples, of which the active ingredient contents were quantified by icELISA, was spiked with corresponding standard substance at 2 and 4 mg, respectively. The extracted ART-based drug samples with no corresponding standard substance added were used as the blank control. The drug samples were added and disposed according to the icELISA procedure as described in the previous section. Three separate samples were taken for each drug sample, and each sample was analyzed in triplicate.Poor quality medicines, both substandard and counterfeit, constitute a major burden on the public health in resource poor countries. The use of such drugs not only severely jeopardizes the health of patients but also thwarts control efforts. Extensive investigations documented such epidemics of counterfeit ART drugs in Southeast Asia,and there is clear evidence showing that such threats have also emerged in other continents.In resource-poor countries, other neglected tropical diseases suffer similar fate,hydroponic fodder system and a recent report of poor-quality generic drug for the treatment of visceral leishmaniasis in the national elimination program of Bangladesh is another vivid example.

Although these examples stress the requirement for strict quality assurance by the government regulatory authorities, the development of simple and rapid methods to assess drug quality convenient methods for quality control at the field sites are desperately needed. Based on our success of generating specific antibodies for ART and its derivatives, we developed an icELISA for accurate measuring of ART drug contents. Here, we further validated the icELISA method using both standard and 22 commercial ART drugs sampled from various hospitals and pharmacies. The contents of ARTs in these drugs determined by icELISA and the gold standard HPLC method showed a borderline significant difference . In particular, the variation of the icELISA results was significantly higher than that of the HPLC method , suggesting that performance of the icELISA needs to be improved. In addition, we want to acknowledge that the convenience samples represented a disparate collection of pills, and some were from known sources of good-quality drugs. Therefore, testing of the method using samples of counterfeit and substandard drugs may be needed for further validation purpose.Commercial drugs contain matrix materials that might interfere with the assay. We showed that the icELISA method was highly sensitive for ARTs, which allows the samples to be highly diluted. This could eliminate the potential interference from the matrices of the commercial drugs. With all drug formulations tested, we did not detect significant interference of the matrices with either method. Furthermore, the use of chromatographically pure acetonitrile for the sample extraction may enhance assay tolerance against matrix interference. In addition, sample extraction may be repeated to increase ART recovery rates. A potential use of the icELISA method is for quantification of ARTs in commercial ACT drug formulations, which contain other partner antimalarial drugs. In our tested samples, the partner drugs did not interfere with the assay, suggesting the icELISA method is specific to detect ARTs in the antimalarial drugs. Although the cross-reactivity of mAb 3H2 with ATS, DHA, and ATM prevents differential detection ofART and its derivatives in the same samples, it does not constitute a major problem for our purpose of using the icELISA for quality assurance of ART drugs because all ART drugs contain a single target analyte of ART or its derivatives.

Further applications of the icELISA under a variety of field settings are needed to validate its value for quality control of ART drugs. At this point, there is no intent for commercialization of the icELISA, and collaborations with colleagues on further testing of the icELISA are encouraged.In order to compare the stability of PSII under Mn deficiency with the response observed when plants were exposed to other relevant nutritional disorders, a multi-elemental deficiency study was conducted, using the Mn-inefficient genotype Antonia. The induction of the different nutrient deficiencies was followed by visual inspection of leaf symptom development and by measuring Chl a fluorescence on the youngest fully expanded leaves, two to three times per week. Plants were sampled for analysis when the first leaf symptoms appeared or if no distinct symptoms developed, when Fv/Fm was reduced to 0.55 . Very distinct leaf symptoms were noticed on Mg, S, Cu and Fe deficient plants before any significant decline in Fv/Fm was observed, whereas no symptoms developed for Mn even at a Fv/Fm value at 0.55. Cu and S deficiency resulted in a marked reduction in shoot growth and Cu deficiency resulted in the development of necrotic tips commonly referred to as “yellow tip” whereas S deficiency resulted in anthocyanosis of lower stems . The chlorophyll content was reduced significantly in plants exposed to Mg-, S- and Fe-deficiency, but only marginally in Cu deficient plants despite a very low Cu concentration . Mn deficiency was the only nutritional disorder, which did not result in a decreased content of Chl nor any visible leaf symptoms and yet the Fv/Fm was reduced to 0.55 when plants were exposed to Mn deficiency . The successful induction of the individual nutrient deficiencies were confirmed by an ICP-MS based multi-elemental leaf tissue analysis. The Mg, S, Mn, Cu and Fe treatments were found to be well below the reported critical threshold limits for the development of deficiencies, being 1300, 1500, 17, 5 and 35 µg g-1 dry weight , respectively . The impact of Mg, S, Fe, Cu and Mn deficiency on selected key-proteins in PSII and PSI was examined and compared with the control treatment . The amount of the central core protein of PSII, PsbA, was significantly reduced for Mn and Fe deficient plants compared to the control treatment, resulting in a 63% and 37% reduction, respectively. However, Mg, S and Cu deficiency did not affect the content of PsbA significantly. To further confirm damage to the central core of PSII, an antibody directed against PsbP, which is a subunit of the OEC, was used.

The relative decrease in PsbP followed that of PsbA under Mn deficiency, however, it should be noted that the reduction in PsbP was insignificant under Fe-deficiency . The amount of Lhcb1, a subunit of the major light harvesting complex LHCII was insignificantly changed in Mg, S, Mn and Cu deficient plants. However, Fe-deficient plants appeared to have considerably less Lhcb1 compared to the control treatment and there was a tendency towards an increase in the amount of Lhcb1 for the S and Cu deficient plants. Likewise,fodder system the amount of the PSI core subunit PsaF was significantly increased in the S and Cu deficient plants by 69% and 87% respectively. We describe a theoretical framework for predicting bulk nanobubble size of any given combination of a gas and water, based upon the force balance at the gas/liquid interface. We show how this balance can develop between the internal pressure, external pressure and surface tension, and the electrostatic repulsion of hydroxide ions adhered to the surface of the nanobubble that gives rise to their relatively high negative zeta potential. We also analyse the adsorption of hydroxide ions at the surface of the nanobubble and the dependence of nanobubble formation on pH and the required initial size of a bubble that leads to the formation of a stable nanobubble. Further analysis is carried out on the velocity of the bulk nanobubble due to Brownian motion, and its effects on the rates of diffusion of the gas into the water, as well analysis on the interaction between hydroxide ions and oxygen molecules to infer the inhibition of their diffusion. Future applications and methodologies for applications, based on the equations proposed are also discussed. The dictionary definition of the prefix ‘nano’ indicates that the object or dimension it describes is in the range of 10-9 of the dimensions it is described by, and it is as such that nanobubbles have become popular, under a misnomer. Many prefer the name ultrafine bubbles, since the size range of nanobubbles begins at one micron, and usually goes down much further to only as few as 10 nanometers in diameter. Since their discovery as the remains of collapsing microbubbles and of their persistence after formation, attempts have been consistently to understand the mechanics of their dissolution and stability, to enable the design of systems that use them to our advantage. The first field to experience benefits due to micro- and nanobubbles was agriculture, and the use of nanobubble water was well-documented by several studies since the year 2000, showing increased growth and quality of root vegetables grown in hydroponic systems, as well as the cultivation of tomatoes in soil. Further benefits were also demonstrated with pisciculture, showing increased sizes of the fish cultured in nanobubble water, due to an increase in the dissolved oxygen content. Similar benefits were also demonstrated in the case of shrimp breeding, due to the same phenomenon.

However, all of these systems were simply a case of using the equipment for generating microbubbles without much control, and to permit them to dissolve into the water without regard for optimization. Indeed, without any parameters to measure the rate of dissolution and the generation and stability of the generated bubbles, it is not possible to optimize such a system. Thus, ongoing research has focused on the generation, stability and control of these bubbles for diverse application in the fields of drug delivery, water treatment, energy storage, and various others. 1 The second technological application of microbubbles was for the treatment of water based on the release of hydroxide ions from collapsing microbubbles, which shed light on one particular area, which was a promising candidate for explaining the stability of the nanobubble. The focus of stability was discovered by measurement of the zeta-potential of the first microbubbles of about 2 microns in diameter, which was found to be about -35 mV, and is still thought to be the cloud of ions that exists around a nanobubble. This suggested a role of the surrounding cloud of ions in their stability, in particular their ability to inhibit diffusion of the gas into the fluid, which has given rise to several theories regarding the mechanism of the ions’ stabilizing influence. Several approaches have also been made for specific cases such as surface nanobubbles and electrochemically generated bubbles, which involve several scenarios of diffusion and shrinkage. The work that is outlined here will summarize and look for theoretical evidence and alternatives to the presented theories, as well as present a new argument for the mechanism of stability of bulk nanobubbles, which seeks to incorporate and explain as many of the observed behaviors of nanobubble systems as possible. A further analysis of possible future applications is also presented. Where pint is the internal pressure, pext is the external pressure, γ is the surface tension, and r is the radius of the nanobubble. The scientific consensus is that the internal pressure of the bubble is not high enough to balance both the external pressure, which is a combination of the pressure exerted by the water column above the bubble as well as atmospheric pressure, and the pressure exerted by the surface tension, which seeks to reduce the surface area of the nanobubble. Both of these contribute to the pressure differential across the nanobubble surface that essentially forces the bubble to collapse, with the gas leaving the bubble by diffusing into the bulk solvent. Given the small amounts of gas within the bubbles, this should, in theory, take a very small amount of time to diffuse and disperse, causing the nanobubble to shrink to nothing almost instantly. However, the lifetime of nanobubbles has bene measured in the hours, if not days, which shows that the process of diffusion should be inhibited in some way, and that the pressure is, in effect, balanced or very nearly so.