Gali's Research
(Regularly Updated)
Investigation of on-road diesel vehicle fleet emissions to evaluate emission control policy effectiveness and their impact on hotspot air quality. Assisted Research (Research Associate in the Division of Environment & Sustainability, Hong Kong University of Science and Technology, Hong Kong, 2019-21)
This study applied advanced pollutant assessment techniques to answer the nature and magnitude of emissions from medium and heavy-duty diesel traffic and their impacts on roadway hotspots air quality in Hong Kong. (Still under progress)
Protocol development for real-time determination of Fuel Sulphur content from Ship Plume. Assisted Research (Post-doctoral Research Associate in the Division of Environment & Sustainability, Hong Kong University of Science and Technology, Hong Kong, 2018-19)
This study developed and evaluated an unmanned aerial vehicle (UAV)-borne lightweight (750 g) microsensor system (MSS), which is capable of measuring ship plume SO2, NO2, NO, CO2, CO, and particulate matter in real-time. Extensive experiments were conducted on the sensor system to evaluate its performance during laboratory and field operations. The effects of cross-sensitivity and meteorological conditions were studied and incorporated to account for the measurement conditions in dispersed ship plumes. The SO2 to CO2concentration ratio-based FSC expression was formulated as per the 2016 European Union Directive and Regulations. Furthermore, the impact of plume dilution on the accuracy of FSC measurement was investigated at different stages using the MSS, with and without the UAV in both simulated conditions and real-world scenarios, maintaining a safe distance from the OGV exhaust stacks. The study demonstrates the robustness of using UAV-borne sensor system for ship emission sniffing and FSC determination.
Diurnal trends of particulate matter (PM) induced oxidative potential in different urban environments. (Post-Doc in Energy & Environment, City University of Hong Kong, Hong Kong, 2016-18)
This study is aimed at comparing time-resolved diurnal trends of PM-induced oxidative potential of urban background and vehicle-influenced roadside sites, during winter 2016 in Hong Kong. A new profluorescent nitroxide probe (BPEAnit) was employed in the real-time measurement of ROS using Particle-into-Liquid-Sampler (PILS). The measurements were carried in 2 h intervals over a period of 24 h. On volumetric analysis, the ROS measurements resulted in multiple peaks at 8:00, 16:00, and 20:00 h time periods, at the background site, compared to roadside’s non-intermittent decrease/increase trends suggestive of regular traffic flow at the roadside site. However, on per mass basis, the ROS quantities remained uniform for almost 16 h in a day (during 8:00 to 0:00 h) at the roadside. Interestingly, though PM mass was less (by ~1 µg/m3) at the roadside site compared to the background, ROS generation was noted significantly higher (0.5-1 fold; n=6 p<0.05). While weekdays at the background site, generated more ROS (5-10%) during 6:00 to 18:00 h, weekends resulted in high from midnight to 4:00 AM. But at the roadside, the weekend prone ROS quantities dominated weekdays’ especially during 14:00 h to 6:00 h (Fig. 10). These are well in line with PM, BC & p-PAHs concentration which distinguished the peak hours of PM generation - at the background site (8:00-10:30; 11:00-12:30; 13:30-15:30; 18:30-22:00 h) compared to roadside (8:00-14:00; 15:00-22:00 h). A similar study using filters for PM resulted in the hypothesis of a new toxicity mechanism
Publication 1 - Publication 2 - Publication 3 - Publication 4
Comparative analysis of diesel and biodiesel particulate matter on cellular oxidative stress. (Post-Doc in Energy & Environment, City University of Hong Kong, Hong Kong, 2014-15)
This study investigated the chemical composition of solid particulate phase PM (solid-PM) and gaseous semi-volatile phase PM (SV-PM) from diesel and biodiesel blend fuel exhaust, and their effect on cellular oxidative potential. The total PM mass concentration has been low for biodiesel fuel over diesel exhaust. But, while diesel combustion generated more solid-PM, biodiesel produced higher concentration of SV-PM confirms the existence of greater amounts of organic compounds in the latter. The same trend was noted in OC-EC and PAHs analysis. However, the distribution of organic compounds, both quantitatively and qualitatively, were mostly limited to solid-PM compared to SV-PM. But, the macrophage cells, employed for cell viability and oxidative potential analysis, were highly susceptible to SV-PM on PM mass normalization. Hence, though the PM mass concentration has been low in SV-PM, particularly in biodiesel fuel, the greater potential of it being a toxic agent should not be overseen. and results are compared in accordance with the functional groups of these particles where the data was obtained from FTIR and UV-Visible spectrophotometer.
Redox characteristics of size-segregated particulate matter (PM) from public transport microenvironments in Hong Kong. (Post-Doc in Energy & Environment, City University of Hong Kong, Hong Kong, 2014-15)
This investigation outlines on the cell toxicity due to size segregated particulate matter collected from different public transport microenvironments in the metropolitan city of Hong Kong. Heterogeneous distribution of PM-induced ROS was observed, demonstrating the differential capability of PM to produce oxidative stress, and the need to use additional metrics as surrogate of indicator of exposure instead of PM mass concentrations in epidemiologic studies. The solubility of transition metals was found to play an important role in inducing cell toxicity. These metals and OCEC were found to correlate with ROS by different degree depending on their sources illustrating the complexity of mechanisms that cause the health effects. We also found PM-induced endogenous ROS for the public transport microenvironments were over 50-fold lesser than the typical ambient sites, implying very limited oxidative potential of PM in daily commuter exposure in public transport routes.
Publication 1 - Publication 2 - Poster Presentation - Oral Presentation Proceedings - Best Paper Award
Toxicological effects of TiO2 nanoparticles on cellular metabolism and morphology. (Post-Doc in Energy & Environment, City University of Hong Kong, Hong Kong, 2013-14)
The study demonstrated particle size and duration of exposure played a major role in eliciting cytotoxicity for engineered TiO2nanoparticles. They exhibited greater aggregation in the aqueous solvent with increase in time, and act as the catalyst in generating exogenous-ROS in dark environment. Dissolved oxygen was found to be a driving force, as an additional augmenting factor of cell toxicity. At longer exposure, these nanoparticles, even at low concentrations, were found detrimental to cells in a series of cellular damage stages – apoptosis, membrane rearrangement, and necrosis leading to late cell death, and in the long run will lead to severe health implications. Endogenous-ROS mediated ATP-driven cytoskeletal actin rearrangement was hypothesized, through FACS and TEM analyses, to be the possible mechanism for cell toxicity leading to necrosis, which was earlier presumed to be non-mediated by ROS. However, further investigation is also necessary to establish the signaling pathways that bring about the cellular changes on farthest long-term exposure, which will help understand underlying molecular mechanisms associated with ROS.
Spatial and seasonal heterogeneity of atmospheric particulate matter in inducing oxidative stress. (Post-Doc in Energy & Environment, City University of Hong Kong, Hong Kong, 2013-14)
This study investigated the cytotoxicity, exo- and endogenous reactive oxygen species induced by water extracts of fine and coarse PM at four different sites in an urban city. Large seasonal and spatial variation of PM mass-based ROS was observed in the study demonstrating the highly heterogeneous redox activity of atmospheric PM across the urban area due to the differences in PM sources and their ambient processes. Such non-uniformity of PM intrinsic oxidative potential also suggests the non-linear response of adverse health effects to PM mass, which may lead to systematic bias in epidemiologic studies using only indicators of PM mass concentration. In addition, different size fraction of PM was found to have differential contribution to the total burden of PM-induced oxidative stress, with coarse PM appeared to be more redox active than fine PM on per PM mass basis, which was notable with increase in cell exposure time. Also, endo-ROS activity was observed significantly higher than exo-ROS, highlighting the complexity of mechanisms that may drive ROS generation in physiological system. Despite comparable differences in ROS, traffic and urban sites resulted in more redox activity. Lastly, we identified the redox potent water-soluble metals that are potentially promising to serve as surrogates of PM-induced oxidative potential with high correlations, however, there also exists an inconsistency of such association by PM from different sites, indicating possible synergistic and/or antagonistic effects of ROS generation and the need for multiple-component model of surrogate for PM oxidative potentials.
Biochemical, Biophysical and Molecular Biology studies on thermostable Laccase from Cereus pterogonus Lem. And Opuntia vulgaris Mill. (Ph.D. in Biochemistry & Molecular Biology, Pondicherry University, India, 2007-2013)
The aim of this research is to identify an enzyme protein that is of social use. The laccase enzyme protein, because of its wide availability and capability of detoxifying phenolic compounds, was selected to understand its thermostability in a couple of xerophytic plants namely - Cereus pterogonus Lem. and Opuntia vulgaris Mill. The laccase enzyme showed promising results at high temperatures (70 to 90oC) which is of industrial importance. The enzyme was active at basic pH 10. Existence of trimeric, dimeric and monomeric forms of the enzyme was revealed with SDS-PAGE and Zymogram analysis. The stability of enzyme protein and its enzyme activity at high temperatures in presence of divalent copper and manganese were revealed through Circular Dichroism (60% random coils), DSC (Tm of 121oC for native protein and 199oC for metal associated protein), TGA (10% loss in weight at 100oC), EPR, Fluorescence (presence of two domains) and Time course studies (thermostability). Polyclonal antibodies were developed against native protein forms, supported by western blot. The laccase gene sequence of the two selected plant species were submitted to Genbank with accession numbers JN793990 and JN793991. This laccase was also found to decolorize dyes such as Malachite green and Indigo blue by 97 and 98% respectively within 12 hours.
Ph.D. Dissertation - Publication 1 - Publication 2 - Publication 3 - Publication 4 - Publication 5
Effect of Homobrassinolide on Alkaline Phosphatase and Phosphocreatine Kinase enzyme activities in Brain, Heart and Testes of male rat. (M.Phil. in Biochemistry & Molecular Biology, Pondicherry University, India, 2005-2007)
The 28-Homobrassinolide is a plant hormone implicated in plant growth and development. Its effect on animal metabolism was less known to date. We have investigated its effect on the marker enzymes such as alkaline phosphatase and creatine kinase in selected rat tissues-brain, heart, liver, kidney, skeletal muscle and testis. 28-HB was administered (66 and 330 ng/ Kg body weight) intradermally in male albino wistar strain rats and changes in alkaline phosphatase and creatine kinase activities were measured. An overall reduction in both the enzyme activities occurred within 2hr of administration with few exceptions. Time course studies indicated a decrease in enzyme activities as a function of time. Blood glucose level decreased by a percentage of 15.7 and 21.7 compared to control with the administration of 10µg and 50µg 28-HB respectively. We conclude that 28-HBinhibited both the enzymes in the tissuesand produced erythrocytosis, leukocytosis and hypoglycemia,while cellular phosphorylation status remained principally affected by this oxysterol in rat.
Genetic Manipulation of Tobacco plant with Annexin gene through Agrobacterium mediated Transformation. (M.Sc. in Biochemistry, Sri Krishnadevaraya University, India, 2004)
The research project was a part of Master's programme, carried out in 2004. It was aimed at introducing annexin gene into tobacco plant to create a transgenic tobacco plant. Annexins are a family of structurally related proteins that exhibit calcium dependent binding to phospholipids. They carry out Trans-membrane channel activity, inhibition of phospholipase A2, inhibition of coagulation and settlement of cell-matrix interactions. At first, annexin gene and pGPTV vector was prepared with restriction enzyme digestion with EcoR I and Xba I. The gene was ligated with the vector to form a recombinant plasmid. This plasmid is introduced into DH5α competent cells and taken for Triparental mating with Agrobacterium tumefaciens to generate Ti plasmid/annexin gene recombinants. This recombinant plasmid was introduced into tobacco plant by creating a wound to the plant leaf and followed by its infection with recombinant plasmid containing A.tumefaciens. This was followed with standard plant tissue culture procedures and finally the genomic DNA isolated from developed callus was subjected to gene specific amplification and found to be successful existence of annexin gene in tobacco plant.