Design of a simple paper-based colorimetric biosensor using polydiacetylene liposomes for neomycin detection.

We developed a paper-based analytical device (µPAD) combined with self-signaling polydiacetylene (PDA) liposomes for convenient visual neomycin detection. The simple dot array type of µPAD was fabricated by the wax printing technique, and the PDA liposomes in the aqueous solution were facilely immobilized onto the hydrophilic dot region of the paper substrate. We found that, when the PDA liposomes were inserted to the paper matrix, the stability of the PDA liposomes can be significantly enhanced by adding a hydrophilic reagent such as polyvinyl alcohol and glycerol to the liposome solution. In particular, polyvinyl alcohol (PVA) provides the best stabilization among the various hydrophilic reagents tested in this contribution, and the enhanced stability sharply increased the sensitivity of the PDA liposomes in the paper matrix. Based on the above results, we successfully detected neomycin through both naked-eye observation and fluorescence measurement of PDA signals. The detection limit was 1 ppm and was selective to non-aminoglycoside antibiotics.

The suitability evaluation of dredged soil from reservoirs as embankment material.

We assessed the suitability of soil dredged from reservoirs as embankment material and investigated its physical and geochemical properties and strength parameters, as well as its environmental stability. The dredged soil samples were taken from the Ansung, Jechon, and Mulwang Reservoirs in Korea. To evaluate their environmental stability and geochemical properties, we examined their levels of heavy metal contamination, pH, and electrical conductivity. We also conducted X-ray fluorescence and X-ray diffraction analyses. Furthermore, we determined the geotechnical characteristics, such as the compaction characteristics, and permeability coefficient, and we performed consolidated undrained triaxial compression tests to evaluate the recycling potential of dredged soil as embankment material. The concentrations of heavy metals in the sediment samples were lower than those of the standard samples. The pH value of the soil samples ranged from 4.25 to 5.39, and the electrical conductivity ranged between 83.3 and 265.0 µS/cm, indicating suitability for use as construction material with steel and concrete. Based on the values of the mechanical properties of the dredged soil, analysis of slope stability was performed for various cases and water level conditions. Our results indicate that the dredged soil has sufficient stability for substitution of embankment material and also as new embankment material for expansion.

Recyclability of bottom ash mixed with dredged soils according to the transportation distance and mixing ratio through the estimation of CO2 emissions.

Bottom ash and dredged soils can be used as construction materials because they are similar in physical characteristics to natural aggregates. However, whenever such byproducts as bottom ash and dredged soils are used, the energy efficiency of recycling is offset to a certain degree by emissions from transportation. The objective of this study is to analyze the environmental efficiency of recycling bottom ash and dredged soils through the estimation of CO2 emissions, considering both transportation distance and the mixing ratio. Agricultural reservoirs were selected as the final destinations of these recycled materials. This analysis demonstrated that using 100% bottom ash emits less CO2 than using natural aggregates when the ash is transported less than 35.15 km. This breakeven distance increases exponentially with the mass fraction of admixed dredged soil. However, admixture with natural soils does not affect the breakeven distance. Using the breakeven distances, the effective area with which it is efficient to recycle bottom ash was delineated. When dredged soil is admixed to a mass fraction of 70%, the effective area covers most of South Korea. In addition, 100% bottom ash was efficient in 1622 reservoirs (9.45%) in terms of CO2 emissions, and the mixture with 30% bottom ash and 70% dredged soils is efficient in 98.83% of all of the reservoirs in Korea. Bottom ash is most useful for reducing CO2 emissions when it is mixed with dredged soils, which are a byproduct of construction found on-site. This result is meaningful because bottom ash and dredged soils are complementary in their physical characteristics, and they need to be mixed before use as construction materials. The recycling of bottom ash becomes even more attractive with anticipated improvements in fuel efficiency.

AOT/isooctane reverse micelles with a microaqueous core act as protective shells for enhancing the thermal stability of Chromobacterium viscosum lipase.

According to the different environmental systems for lipase reactions, changes in thermal stability were investigated by employing the Chromobacterium viscosum lipase and a two-step series-type deactivation model. The half-life (6.81 h) of the lipase entrapped in reverse micelles at 70 °C was 9.87- and 14.80-fold longer than that in glycerol pool or in aqueous buffer. The deactivation constants for the first and second step (k1 and k2) at all temperatures drastically decreased when the lipase was entrapped in reverse micelles. In particular, k1 (3.84 h(-1)) at 70 °C in reverse micelles was 1.57-fold lower than that in aqueous buffer (6.03 h(-1)). Based on the fluorescence spectrometry, the amount of excited forms of tryptophan and tyrosine increased markedly during the thermal-treatment in aqueous buffer, whereas no significant fluctuation was noted in the reversed micellar system. These results indicated that the encapsulation in reverse micelles could be favorable for preventing the enzyme from heat-induced denaturation.

Thermal deactivation kinetics of Pseudomonas fluorescens lipase entrapped in AOT/isooctane reverse micelles.

Thermostability of the lipase (EC 3.1.1.3) was found to be increased by the enzyme-entrapment in 50 mM AOT/isooctane reverse micelles. The half-life (15.75 h) of Pseudomonas fluorescens lipase entrapped in reverse micelles at 70 °C was 9.72- and 11.41-fold longer than those solubilized in a glycerol pool or in 10 mM phosphate buffer (pH 8.0), respectively. The enzyme deactivation model considering a two-step series-type was employed, and deactivation constants for the second step (k2) at all temperatures were drastically decreased after the lipase was entrapped in reverse micelles. In particular, k2 (0.0354 h⁻¹) at 70 °C in reverse micelles was 12.33- and 13.14-fold lower than in a glycerol pool or in the phosphate buffer, respectively. The deactivation energies (from k1, k2) for the lipase entrapped in the reverse micelles, solubilized in a glycerol pool, or in the aqueous buffer were 7.51, 26.35 kcal/mol, 5.93, 21.08 kcal/mol, and 5.53, 17.57 kcal/mol, respectively.

Assessment of concentration in contaminated soil by potentially toxic elements using electrical properties.

Soils contaminated by potentially toxic elements (PTEs) which affect human health, such as zinc, lead, mercury, cadmium, and arsenic, were applied. The aims of this study are to judge contamination of soil and also to evaluate concentration of contaminated soil using electrical properties such as electrical resistivity and permittivity. The frequency was applied in the experiment ranged from 100 Hz to 10 MHz. As a result, the values of electrical resistivity and permittivity of each soil contaminated by PTEs could be presented as a function related to frequency and could determine whether the soil was contaminated. Also, results indicated that electrical properties give a reliable estimation of concentrations of PTEs contamination in soil.