Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Electrodeposition of Copper and Zinc Ions in Fractals Using a Diffusion Limited Aggregation (DLA) Model

The diffusion limited aggregation (DLA) process has attracted much interest in recent years both because of its simplicity and because of the variety of patterns it can produce in fractals. In this study, an electrodeposition model of the DLA process was used to grow copper and zinc fractals from copper and zinc sulfate solutions respectively. The fractals that formed were analyzed for a fractal dimension (D) between 1 and 2. The fractals were grown by altering the concentration of the solution, time of growth, voltage of the circuit, and the viscosity of the solution. Results have shown that the fractal dimension does not change when varying any of these conditions, however, varying the volume of solution seems to affect the fractal dimension

Investigation of the Effectiveness of Aquatic Plants in Filtering Contaminated Water

Population increase and rapid urbanization are two major factors for scarcity of clean water in 21st century societies across the world. Modern sewage water treatment plants and filtration systems require a lot of economic and land resources which many “lesser developed countries” do not have, leading to large amounts of raw sewage water being released into the enviornment and a lack of clean water for millions. To fulfil such water demand, the use of aquatic plants, also known as macrophytes, have been used in a constructed wetland which allows for the filtration of contaminated water using natural processes involving wetland vegetation, soils, and their associated microbial assemblages. In the present study, Typha (cattail) and Pontederia crassipes (water hyacinth) have been tested in a simulated constructed wetland to study their effect on pollutants removal efficiency (nitrates, ammonium, pH, and Dissolved oxygen). Results show that both the Typha and Pontederia crassipes were effective in filtering out the aforementioned contaminants through the process of phytoaccumulation. However, there was no clear correlation between Dissolved oxygen levels and time in contact with the macrophyte roots possibly due to environmental factors. A better quantitative understanding of the phytoaccumulation process, such as the limits and plateau points of contaminant uptake is needed to optimize the usage and application of Typha and Pontederia crassipes in practical constructed wetlands

Conjugation of Carboxylated Graphene Quantum Dots with Cecropin P1 for Bacterial Biosensing Applications

&lt;p&gt;Quantum dots have proven to be strong candidates for biosensing applications in recent years, due to their strong light emission properties and their ability to be modified with a variety of functional groups for the detection of different analytes. Here, we investigate the use of conjugated carboxylated graphene quantum dots (CGQDs) for the detection of &lt;i&gt;E. coli&lt;/i&gt;, using a biosensing procedure that focuses on measuring changes in fluorescence quenching. We have also further developed this biosensing assay into a compact, field-deployable test kit focused on rapidly measuring changes in absorbance to determine bacterial concentration. Our CGQDs were conjugated with cecropin P1, a naturally-produced antibacterial peptide that facilitates the attachment of CGQDs to &lt;i&gt;E. coli&lt;/i&gt; cells. We also confirm the structural modification of these conjugated CGQDs in addition to analyzing their optical characteristics. Our findings have the potential to be used in situations where rapid, reliable detection of bacteria in liquids, such as drinking water, is required, especially given our biosensor’s relatively low observed limit of detection (LOD).&lt;/p&gt;&lt;br&gt;</jats:p

Investigation of the Effectiveness of Aquatic Plants in Filtering Contaminated Water

Population increase and rapid urbanization are two major factors for scarcity of clean water in 21st century societies across the world. Modern sewage water treatment plants and filtration systems require a lot of economic and land resources which many “lesser developed countries” do not have, leading to large amounts of raw sewage water being released into the enviornment and a lack of clean water for millions. To fulfil such water demand, the use of aquatic plants, also known as macrophytes, have been used in a constructed wetland which allows for the filtration of contaminated water using natural processes involving wetland vegetation, soils, and their associated microbial assemblages. In the present study, Typha (cattail) and Pontederia crassipes (water hyacinth) have been tested in a simulated constructed wetland to study their effect on pollutants removal efficiency (nitrates, ammonium, pH, and Dissolved oxygen). Results show that both the Typha and Pontederia crassipes were effective in filtering out the aforementioned contaminants through the process of phytoaccumulation. However, there was no clear correlation between Dissolved oxygen levels and time in contact with the macrophyte roots possibly due to environmental factors. A better quantitative understanding of the phytoaccumulation process, such as the limits and plateau points of contaminant uptake is needed to optimize the usage and application of Typha and Pontederia crassipes in practical constructed wetlands.</jats:p

Conjugation of Carboxylated Graphene Quantum Dots with Cecropin P1 for Bacterial Biosensing Applications

Quantum dots have proven to be strong candidates for biosensing applications in recent years, due to their strong light emission properties and their ability to be modified with a variety of functional groups for the detection of different analytes. Here, we investigate the use of conjugated carboxylated graphene quantum dots (CGQDs) for the detection of E. coli, using a biosensing procedure that focuses on measuring changes in fluorescence quenching. We have also further developed this biosensing assay into a compact, field-deployable test kit focused on rapidly measuring changes in absorbance to determine bacterial concentration. Our CGQDs were conjugated with cecropin P1, a naturally-produced antibacterial peptide that facilitates the attachment of CGQDs to E. coli cells. We also confirm the structural modification of these conjugated CGQDs in addition to analyzing their optical characteristics. Our findings have the potential to be used in situations where rapid, reliable detection of bacteria in liquids, such as drinking water, is required, especially given our biosensor’s relatively low observed limit of detection (LOD).<br /

Facile Synthesis of Formate-Functionalized Graphene Quantum Dots

Graphene quantum dots have proven useful for a variety of applications due to their impressive bandgap tunability, which can be achieved through structural modification methods including edge functionalization and doping. Here, we investigate the functionalization of graphene quantum dots with formate esters using a method of noncatalyzed electrophilic substitution. We also examine the optical and structural properties of these formate-functionalized graphene quantum dots using UV-Vis Spectrophotometry, IR Spectroscopy, and NMR Spectroscopy, with the functionalization causing a redshift in absorption consistent with a reduction in bandgap. The findings in this paper have the potential to be used in applications ranging from single photon emission in quantum computing to tunable fluorescence in bioimaging

Encapsulating Natural Dyes into Chitosan-TPP Crosslinked Nanoparticles: A Potential Dye Alternative

The manufacturing sector of the growing fast fashion industry has created damage to the environment. Specifically, synthetic dyes used in the industry are often toxic chemical compounds, and due to poor government regulation, have polluted waterways. While natural dyes may seem to be the better alternative, natural dyes require the use of mordants, which are heavy metal salts, for the dye to bind onto various textiles and increase color intensity. There remains a lack of an environmentally friendly dye that can be used in the industry. Chitosan-Tripolyphosphate (TPP) crosslinked nanoparticles are capable of encapsulating various compounds and have recently been found to be excellent systems for drug delivery due to their small size, shape, and biodegradable properties. In this study, we explore the creation of an environmentally friendly dye by encapsulating Indigo dye, a natural dye, into chitosan-TPP crosslinked nanoparticles. The physical properties of the created nanoparticles, encapsulation efficiency, and textile dyeing efficiency are all investigated. The findings show that a potentially better dye alternative can be created by being encapsulated in chitosan-TPP crosslinked nanoparticles

Facile Synthesis of Formate-Functionalized Graphene Quantum Dots

Graphene quantum dots have proven useful for a variety of applications due to their impressive bandgap tunability, which can be achieved through structural modification methods including edge functionalization and doping. Here, we investigate the functionalization of graphene quantum dots with formate esters using a method of noncatalyzed electrophilic substitution. We also examine the optical and structural properties of these formate-functionalized graphene quantum dots using UV-Vis Spectrophotometry, IR Spectroscopy, and NMR Spectroscopy, with the functionalization causing a redshift in absorption consistent with a reduction in bandgap. The findings in this paper have the potential to be used in applications ranging from single photon emission in quantum computing to tunable fluorescence in bioimaging.</jats:p

Encapsulating Natural Dyes into Chitosan-TPP Crosslinked Nanoparticles: A Potential Dye Alternative

The manufacturing sector of the growing fast fashion industry has created damage to the environment. Specifically, synthetic dyes used in the industry are often toxic chemical compounds, and due to poor government regulation, have polluted waterways. While natural dyes may seem to be the better alternative, natural dyes require the use of mordants, which are heavy metal salts, for the dye to bind onto various textiles and increase color intensity. There remains a lack of an environmentally friendly dye that can be used in the industry. Chitosan-Tripolyphosphate (TPP) crosslinked nanoparticles are capable of encapsulating various compounds and have recently been found to be excellent systems for drug delivery due to their small size, shape, and biodegradable properties. In this study, we explore the creation of an environmentally friendly dye by encapsulating Indigo dye, a natural dye, into chitosan-TPP crosslinked nanoparticles. The physical properties of the created nanoparticles, encapsulation efficiency, and textile dyeing efficiency are all investigated. The findings show that a potentially better dye alternative can be created by being encapsulated in chitosan-TPP crosslinked nanoparticles.</jats:p