The distribution of heavy metals (Cu, Zn, Cd, Pb) in surface sediments was examined in waters off the coast of Marang, Terengganu. A total of 20 samples were collected using Ponar grab and analysed by inductively coupled plasma-mass spectrometer after closed digestion with acid. The sediments were filtered using a dry sieving method to determine their particle size. The spatial distribution maps on the concentration of selected metals were drawn using the ArcGIS software. Results showed that the average concentration of Cu, Zn, Cd, and Pb were 2.33±0.38 µg/g dry weight, 28.4±3.78 µg/g dry weight, 0.09±0.01 µg/g dry weight and 8.35±1.48 µg/g dry weight, respectively. The level of pollution was also evaluated using the Index of Geoaccumulation (Igeo) and Pollution Load Index (PLI). All Igeo and PLI values obtained were low, which indicated low or no pollution. Meanwhile, the sediment mean size ranged between -0.77Ø and 3.18Ø, which characterised a sandy type of sediment. Correlation analysis showed a positive correlation between the heavy metals and sediment size. The results indicated that there was a common source of heavy metal pollution in the study area, possibly from shipping activities. Overall, there was no significant heavy metal pollution in the waters off Marang. This finding is important as the data could be used to evaluate the risk of metal contamination and the impact of anthropogenic activities on the marine environment.
Two freshwater fish, Rasbora sumatrana (Cyprinidae) and Poecilia reticulata (guppy; Poeciliidae), were exposed to a range of eight heavy metals (copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), iron (Fe), aluminium (Al), and manganese (Mn)) at varied concentrations for 96 h in the laboratory. Mortality was assessed and median lethal concentrations (LC50) were calculated. It was observed that the LC50 values increased with a decrease in mean exposure times, for all metals and for both fish types. The 96-h LC50 values for Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn were 0.006, 0.10, 0.46, 0.63, 0.83, 1.71, 1.53, and 5.71 mg/L for R. sumatrana and 0.038, 0.17, 1.06, 1.99, 15.62, 1.46, 6.76, and 23.91 mg/L for P. reticulata, respectively. The metal toxicity trend for R. sumatrana and P. reticulata from most to least toxic was Cu > Cd > Zn > Pb > Ni > Al > Fe > Mn and Cu > Cd > Zn > Fe > Pb > Al > Ni > Mn, respectively. Results indicated that Cu was the most toxic metal on both fish, and R. sumatrana was more sensitive than P. reticulata to all the eight metals.
Efficient solar driven photoelectrochemical (PEC) response by enhancing charge separation has attracted great interest in the hydrogen generation application. The formation of one-dimensional ZnO nanorod structure without bundling is essential for high efficiency in PEC response. In this present research work, ZnO nanorod with an average 500 nm in length and average diameter of about 75 nm was successfully formed via electrodeposition method in 0.05 mM ZnCl₂ and 0.1 M KCl electrolyte at 1 V for 60 min under 70 °C condition. Continuous efforts have been exerted to further improve the solar driven PEC response by incorporating an optimum content of TiO₂ into ZnO nanorod using dip-coating technique. It was found that 0.25 at % of TiO₂ loaded on ZnO nanorod film demonstrated a maximum photocurrent density of 19.78 mA/cm² (with V vs. Ag/AgCl) under UV illumination and 14.75 mA/cm² (with V vs. Ag/AgCl) under solar illumination with photoconversion efficiency ~2.9% (UV illumination) and ~4.3% (solar illumination). This performance was approximately 3-4 times higher than ZnO film itself. An enhancement of photocurrent density and photoconversion efficiency occurred due to the sufficient Ti element within TiO₂-ZnO nanorod film, which acted as an effective mediator to trap the photo-induced electrons and minimize the recombination of charge carriers. Besides, phenomenon of charge-separation effect at type-II band alignment of Zn and Ti could further enhance the charge carrier transportation during illumination.
Biogenic amines have attracted interest among researchers because of their importance as biomarkers in determining the quality of food freshness in the food industry. A rapid and simple technique that is able to detect biogenic amines is needed. In this work, a new optical sensing material for one of the biogenic amines, histamine, based on a new zinc(II) salphen complex was developed. The binding of zinc(II) complexes without an electron-withdrawing group (complex 1) and with electron-withdrawing groups (F, complex 2; Cl, complex 3) to histamine resulted in enhancement of fluorescence. All complexes exhibited high affinity for histamine [binding constant of (7.14 ± 0.80) × 104, (3.33 ± 0.03) × 105, and (2.35 ± 0.14) × 105 M-1, respectively]. Complex 2 was chosen as the sensing material for further development of an optical sensor for biogenic amines in the following step since it displayed enhanced optical properties in comparison with complexes 1 and 3. The optical sensor for biogenic amines used silica microparticles as the immobilisation support and histamine as the analyte. The optical sensor had a limit of detection for histamine of 4.4 × 10-12 M, with a linear working range between 1.0 × 10-11 and 1.0 × 10-6 M (R2 = 0.9844). The sensor showed good reproducibility, with a low relative standard deviation (5.5 %). In addition, the sensor exhibited good selectivity towards histamine and cadaverine over other amines, such as 1,2-phenylenediamine, triethylamine, and trimethylamine. Recovery and real sample studies suggested that complex 2 could be a promising biogenic amine optical sensing material that can be applied in the food industry, especially in controlling the safety of food for it to remain fresh and healthy for consumption.
ZnO with two different morphologies were used to study the inhibition of Streptococcus sobrinus and Streptococcus mutans which are closely associated with tooth cavity. Rod-like shaped ZnO-A and plate-like shaped ZnO-B were produced using a zinc boiling furnace. The nanopowders were characterized using energy filtered transmission electron microscopy (EFTEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, Raman spectroscopy and dynamic light scattering (DLS) to confirm the properties of the ZnO polycrystalline wurtzite structures. XRD results show that the calculated crystallite sizes of ZnO-A and ZnO-B were 36.6 and 39.4nm, respectively, whereas DLS revealed particle size distributions of 21.82nm (ZnO-A) and 52.21nm (ZnO-B). PL spectra showed ion vacancy defects related to green and red luminescence for both ZnO particles. These defects evolved during the generation of reactive oxygen species which contributed to the antibacterial activity. Antibacterial activity was investigated using microdilution technique towards S. sobrinus and S. mutans at different nanopowder concentrations. Results showed that ZnO-A exhibited higher inhibition on both bacteria compared with ZnO-B. Moreover, S. mutans was more sensitive compared with S. sobrinus because of its higher inhibition rate.
A cationic Schiff base ligand, TSB (L) and its Zn (II) complex (1) were synthesized and characterized by using CHN, (1)H-NMR, FT-IR, UV, LC-MS, and X-ray methods. Their ability to inhibit topoisomerase I, DNA cleavage activities, and cytotoxicity were studied. X-ray diffraction study shows that the mononuclear complex 1 is four coordinated with distorted tetrahedral geometry. The singly deprotonated Schiff base ligand L acts as a bidentate ON-donor ligand. Complexation of L increases the inhibitory strength on topoisomerase I activity. Complex 1 could fully inhibit topoisomerase I activity at 250 μM, while L did not show any inhibitory effect on topoisomerase I activity. In addition, L and complex 1 could cleave pBR322 DNA in a concentration and time dependent profile. Surprisingly, L has better DNA cleavage activity than complex 1. The cleavage of DNA by complex 1 is altered in the presence of hydrogen peroxide. Furthermore, L and complex 1 are mildly cytotoxic towards human ovarian cancer A2780 and hepatocellular carcinoma HepG2.
The current study described the synthesis and the in vivo acute oral toxicity evaluations in Sprague Dawley rats. The compounds were characterized by elemental analyses, LC-MS, FTIR, (1)H NMR, (13)C NMR and UV-visible spectroscopy. In the acute toxicity study, a single administration of the compounds was performed orally to the rats at the single doses of 2000 mg/kg and they were then monitored for possible side effects, mortality or behavioral changes up to 14 days. The serum level of aspartate (AST), alanine aminotransferases (ALT), alkaline phosphate (ALP), triglyceride, high density lipoprotein (HDL), immunoglobulins (GAM) and the C-reactive proteins did not significantly change. The hematological indices white blood cells (WBC), haematocrit (HCT), red blood cells (RBC), mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), and mean corpuscular hemoglobin (MCH) were within the normal range. The renal function indices examined were also within the reference range. Generally, the compounds exhibited low toxic effects as required for further in vivo therapeutic studies.
Zinc complexes were reported to have anti-ulcer activity and used as drug for the treatment of gastrointestinal disorders. A novel compound dichlorido-zinc(II)-4-(2-(5-methoxybenzylidene amino)ethyl)piperazin-1-iumphenolate (ZnHMS) was synthesized, characterized and evaluated for its gastroprotective activity against ethanol-induced ulcer in rats. Gross and microscopic lesions, histochemical staining of glycogen storage, biochemical and immunological parameters were taken into consideration. Oral administration of ZnHMS (30 and 60 mg/kg; 14 days) dose-dependently inhibited gastric lesions. It significantly increased the mucus content and total acidity compared to the control group (P<0.01). Serum levels of aspartate (AST), alanine (ALT) transaminases, pro-inflammatory interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α) and anti-inflammatory interleukin-10 (IL-10) in the rats exposed to ethanol induced ulceration have been altered. ZnHMS considerably enhances (P<0.05) the protection of gastric epithelia by modulating the acute alterations of AST, ALT, IL-6, IL-10, TNF-α and stomach glycogen. Interestingly, ZnHMS did interfere with the natural release of nitric oxide. In addition, acute toxicity study revealed no abnormal sign to the rats treated with ZnHMS (2000 mg/kg). These findings suggest that the gastroprotective activity of ZnHMS might contribute in adjusting the inflammatory cytokine-mediated oxidative damage to the gastric mucosa.
Recently, porous magnesium and its alloys are receiving great consideration as biocompatible and biodegradable scaffolds for bone tissue engineering application. However, they presented poor antibacterial performance and corrosion resistance which limited their clinical applications. In this study, Mg-Zn (MZ) scaffold containing different concentrations of tetracycline (MZ-xTC, x = 1, 5 and 10%) were fabricated by space holder technique to meet the desirable antibacterial activity and corrosion resistance properties. The MZ-TC contains total porosity of 63-65% with pore sizes in the range of 600-800 μm in order to accommodate bone cells. The MZ scaffold presented higher compressive strength and corrosion resistance compared to pure Mg scaffold. However, tetracycline incorporation has less significant effect on the mechanical and corrosion properties of the scaffolds. Moreover, MZ-xTC scaffolds drug release profiles show an initial immediate release which is followed by more stable release patterns. The bioactivity test reveals that the MZ-xTC scaffolds are capable of developing the formation of HA layers in simulated body fluid (SBF). Next, Staphylococcus aureus and Escherichia coli bacteria were utilized to assess the antimicrobial activity of the MZ-xTC scaffolds. The findings indicate that those scaffolds that incorporate a high level concentration of tetracycline are tougher against bacterial organization than MZ scaffolds. However, the MTT assay demonstrates that the MZ scaffolds containing 1 to 5% tetracycline are more effective to sustain cell viability, whereas MZ-10TC shows some toxicity. The alkaline phosphatase (ALP) activity of the MZ-(1-5)TC was considerably higher than that of MZ-10TC on the 3 and 7 days, implying higher osteoblastic differentiation. All the findings suggest that the MZ-xTC scaffolds containing 1 to 5% tetracycline is a promising candidate for bone tissue healing due to excellent antibacterial activity and biocompatibility.
In this study, zinc oxide (ZnO) nanorod arrays were synthesized using a simple hydrothermal reaction on ZnO seeds/n-silicon substrate. Several parameters were studied, including the heat-treatment temperature to produce ZnO seeds, zinc nitrate concentration, pH of hydrothermal reaction solution, and hydrothermal reaction time. The optimum heat-treatment temperature to produce uniform nanosized ZnO seeds was 400°C. The nanorod dimensions depended on the hydrothermal reaction parameters. The optimum hydrothermal reaction parameters to produce blunt tip-like nanorods (770 nm long and 80 nm in top diameter) were 0.1 M zinc nitrate, pH 7, and 4 h of growth duration. Phase analysis studies showed that all ZnO nanorods exhibited a strong (002) peak. Thus, the ZnO nanorods grew in a c-axis preferred orientation. A strong ultraviolet (UV) emission peak was observed for ZnO nanorods grown under optimized parameters with a low, deep-level emission peak, which indicated high optical property and crystallinity of the nanorods. The produced ZnO nanorods were also tested for their UV-sensing properties. All samples responded to UV light but with different sensing characteristics. Such different responses could be attributed to the high surface-to-volume ratio of the nanorods that correlated with the final ZnO nanorods morphology formed at different synthesis parameters. The sample grown using optimum synthesis parameters showed the highest responsivity of 0.024 A/W for UV light at 375 nm under a 3 V bias.
The hemipteran (Insecta) diversity in the upper part of the Kerian River Basin was low with only 8 families and 16 genera recorded at 4 study sites from 3 rivers. Water bug composition varied among sampling sites (Kruskal-Wallis χ (2) = 0.00, p<0.05) but was not affected by wet-dry seasons (Z = 0.00, p>0.05). All recorded water parameters were weakly associated with generic abundance but the biochemical oxygen demand (BOD), chemical oxygen demand (COD), Water Quality Index (WQI) and heavy metals (zinc and manganese) showed relatively strong positive or negative relations with hemipteran diversity and richness (H' and R2). Within the ranges of measured water parameters, the WQI was negatively associated with hemipteran diversity and richness, implying the tolerance of the water bugs to the level of pollution encountered in the river basin. Based on its highest abundance and occurrence (ISI), Rhagovelia was the most important genus and along with Rheumatogonus and Paraplea, these genera were common at all study sites. In conclusion, habitat availability and suitability together with some environmental parameters influenced the abundance and composition of hemipterans in this river basin.
Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO.
The aim of this study was to determine the genotoxicity of a locally produced nanocomposite by Universiti Sains Malaysia, Malaysia using Comet assay. Stem cells from human exfoliated deciduous teeth (SHED) were treated with the nanocomposite at five different concentrations (0.006, 0.0125, 0.025, 0.05, and 0.1 mg/ml) along with concurrent negative (medium alone) and positive control (zinc sulfate heptahydrate) and incubated at 37°C for 24 hours in an incubator at 5% CO2. The tail moment was used to assess the extent of DNA damage. The tail moment for the group of SHED treated with nanocomposite (for all the five different concentrations) was not statistically significant as compared to the negative control, suggesting that the locally produced dental nanocomposite did not induce any DNA damage. Hence, it can be concluded that the locally produced nanocomposite is non-genotoxic on stem cells from human exfoliated deciduous teeth.
Land development, especially construction works, increase storm water volumes and pollution loads into rivers and lakes. The temporary drainage system at construction sites, particularly during the construction stage discharges a large amount of pollutants that can damage the aquatic system of the receiving water bodies. The potential of vegetative swale to alleviate this problem was evaluated. The size of the constructed vegetative swale was 7cm deep, 400cm long and 15cm wide at the bottom, and 17cm wide at the top. The experiment was conducted batch wise by filling the storage tank with the run-off water from the construction site. The water was allowed to flow through a pipe into the retention basin to maintain uniform flow before it entered the swale. The study showed that the run-off infiltrated through the soil at a rate of 489.6 mm/hr. Samples of surface run-off and infiltration water were collected at the end and the bottom of the swale. The results indicate that chemical oxygen demand (COD), total suspended solid (TSS), turbidity, iron and zinc were reduced by 85.4%, 80.8%, 36.4%, 52.8% and 96.0%, respectively, by surface flow and 91.1%, 98.8%, 58.2% 55.5% and 98.1%, respectively, by infiltration. Removal of nitrate and phosphorus by the planted vegetation was 69.4% and 21.1%, respectively, by infiltration. However, nutrient removal by surface flow was negligible. In conclusion, the vegetative swale was able to improve the water quality of the storm water run-off from the construction site from Class V to Class III, according to the Interim National Water Quality Standards for Malaysia.
Effects of food irradiation on allergen and nutritional composition of giant freshwater prawn are not well documented. Thus, this study aimed to investigate the effects of gamma irradiation on tropomyosin allergen, proximate composition, and mineral elements in Macrobrachium rosenbergii. In this study, prawn was peeled, cut into small pieces, vacuum packaged and gamma irradiated at 0, 5, 7, 10 and 15 kGy with a dose rate of 0.5 kGy/h using cobalt-60 as the source, subsequently determined the level of tropomyosin, proximate composition and mineral elements respectively. The results showed that band density of tropomyosin irradiated at 10 and 15 kGy is markedly decreased. Proximate analysis revealed that moisture, protein, and carbohydrate content were significantly different as compared with non-irradiated prawn. Meanwhile, gamma irradiated M. rosenbergii at 15 kGy was observed to be significantly higher in nickel and zinc than the non-irradiated prawn. The findings provide a new information that food irradiation may affect the tropomyosin allergen, proximate composition and mineral elements of the prawn.
In this work, the structural properties of radio frequency sputtering-grown zinc oxide (ZnO) thin films on sapphire (Al203), gallium arsenide (GaAs) and n-type silicon (Si) substrates were characterized. Scanning electron microscopy was employed to study the surface morphology of the samples. X-ray diffraction (xRD) measurements were also performed to obtain the structural information of the samples. The xRD results showed that the ZnO layers grown on different substrates have similar lattice constant (c) values, which were used to calculate the strain percentages of the ZnO thin films. The surface morphologies of the ZnO thin films indicated the formation of a granular surface when ZnO is deposited on n-type Si(100) and Si( 111 ) substrates. Meanwhile, a leaf-like surface is obtained when ZnO is deposited on GaAs and Al203 substrates. The results showed that the ZnO thin film grown on n-type Si(100) has the best quality among all the samples.
Coal combustion by-products (CCPs) (i.e. fly (FA) and bottom (BA) ashes) generated by power plants contain heavy metals. This research presents leaching properties of coal ashes (FA and BA) collected from Jimah coal-fired power station, Port Dickson, Negeri Sembilan using USEPA standard methods namely toxicity characteristic leaching procedure (TCLP), and synthetic precipitation leaching procedure (SPLP). Heavy metals like lead (Pb), zinc (Zn), copper (Cu) and arsenic (As) were quantified using atomic absorption spectrometer (AAS). The leached of heavy metals fluxes were Cu < Zn < Pb < As. As leached the most whilst indicating of possible contamination from As. Overall, the ranges of leached concentration were adhered to permissible limits of hazardous waste criteria for metal (Pb and As) and industrial effluent (Zn and Cu). The presented data has potential reuse as reference for the coal ash concrete mixed design application in construction industries.
Bacterial based remediation of environmental toxicants is a promising innovative technology
for molybdenum pollution. To date, the enzyme responsible for molybdate reduction to Moblue
from bacteria show that the Michaelis-Menten constants varies by one order of magnitude.
It is important that the constants from newer enzyme sources be characterized so that a
comparison can be made. The aim of this study is to characterize kinetically the enzyme from a
previously isolated Mo-reducing bacterium; Bacillus pumilus strain Lbna. The maximum
activity of this enzyme occurred at pH 5.5 and in between 25 and 35 oC. The Km and Vmax of
NADH were 6.646 mM and 0.057 unit/mg enzyme, while the Km and Vmax of LPPM were 3.399
mM and 0.106 unit/mg enzyme. The results showed that the enzyme activity for Bacillus
pumilus strain Lbna were inhibited by all heavy metals used. Zinc, copper, silver, chromium,
cadmium and mercury all caused more than 50% inhibition to the Mo-reducing enzyme activity
with copper being the most potent with an almost complete inhibition of enzyme activity
observed.
In this study, tannin-based natural coagulant was used to treat stabilized landfill leachate. Tannin modified with amino group was utilized for the treatment process. Central composite design (CCD) was used to investigate and optimize the effect of tannin dosage and pH on four responses. The treatment efficiency was evaluated based on the removal of four selected (responses) parameters; namely, chemical oxygen demand (COD), color, NH3-N and total suspended solids (TSS). The optimum removal efficiency for COD, TSS, NH3-N and color was obtained using a tannin dosage of 0.73 g at a pH of 6. Moreover, the removal efficiency for selected heavy metals from leachate; namely, iron (Fe2+), zinc (Zn2+), copper (Cu2+), chromium (Cr2+), cadmium (Cd2+), lead (Pb2+), arsenic (As3+), and cobalt (Co2+) was also investigated. The results for removal efficiency for COD, TSS, NH3-N, and color were 53.50%, 60.26%, and 91.39%, respectively. The removal of selected heavy metals from leachate for Fe2+, Zn2+, Cu2+, Cr2+, Cd2+, Pb2+, As3+ and cobalt Co2+ were 89.76%, 94.61%, 94.15%, 89.94%, 17.26%, 93.78%, 86.43% and 84.19%, respectively. The results demonstrate that tannin-based natural coagulant could effectively remove organic compounds and heavy metals from stabilized landfill leachate.
The aim of this study is to investigate the performance of combined solar photo-catalyst of titanium oxide/zinc oxide (TiO2/ZnO) with aeration processes to treat petroleum wastewater. Central composite design with response surface methodology was used to evaluate the relationships between operating variables for TiO2 dosage, ZnO dosage, air flow, pH, and reaction time to identify the optimum operating conditions. Quadratic models for chemical oxygen demand (COD) and total organic carbon (TOC) removals prove to be significant with low probabilities (<0.0001). The obtained optimum conditions included a reaction time of 170 min, TiO2 dosage (0.5 g/L), ZnO dosage (0.54 g/L), air flow (4.3 L/min), and pH 6.8 COD and TOC removal rates of 99% and 74%, respectively. The TOC and COD removal rates correspond well with the predicted models. The maximum removal rate for TOC and COD was 99.3% and 76%, respectively at optimum operational conditions of TiO2 dosage (0.5 g/L), ZnO dosage (0.54 g/L), air flow (4.3 L/min), reaction time (170 min) and pH (6.8). The new treatment process achieved higher degradation efficiencies for TOC and COD and reduced the treatment time comparing with other related processes.