Synthesis and optimization of nano-sized bacterial-based violacein pigment using response surface methodology

Violacein from Chromobacterium violaceum has raised the enthusiasm of researchers in conducting comprehensive studies on these pigments due to their diverse biological activities including antibacterial and antioxidant properties. However, a limitation related with the solubility of the violacein pigment, by which it is commonly dissolved in toxic solvents such as dimethyl sulfoxide and methanol instead of being soluble in biological fluids and water. Hence, this study provides a method to synthesis the violacein pigment in nanoscale through an encapsulation technique using chitosan-tripolyphosphate (Cs-TPP) nanoparticles. The synthesis of nanoparticles in this study involved ionic gelation between chitosan and tripolyphosphate (TPP), in which several parameters were taken into consideration in order to control the size and dispersion stability of the violacein pigment in the suspension. Preparation parameters, including the concentration of chitosan, TPP and pigment as well as the mass ratio of chitosan to TPP, were optimized using Response Surface Methodology (RSM). Minimum particle size of 149.0 nm with zeta potential of +23.40 mV was obtained at the optimal formulations of 2.33 mg/mL of chitosan, 1.5 mg/mL of TPP, and 1 ppm of violacein pigment and at mass ratio of chitosan:TPP of 7:1. This nano-sized violacein pigment is expected to be applied as safe additive, colorant, and therapeutic agents. Meanwhile, RSM in the study could provide the optimal formulations for producing stable nano-sized violacein pigment

Fabrication of nylon-66 membranes coated with violacein pigment for wound dressing application

Wound dressing is used for effective wound healing and a suitable material must be used to cover wound. Nylon was chosen because it has high mechanical strength and has hydrophilic properties compared to other polymers. The incorporation of violacein pigment as natural antibacterial agent onto the nylon membranes will give added value to the wound dressing application. Two methods of fabrication were carried out which were electrospinning and casting technique. Based on the images obtained from Field Emission Scanning Electron Microscope (FESEM), the morphology of nylon membrane was made up of nanofibers which indicated the production of high surface area to volume ratio of electrospun membrane. Furthermore, the tensile strength of electrospun membrane, 8.0292 MPa is higher compared to casted membrane,3.284 MPa which shows better elasticity. By using Differential Scanning Analysis-Thermogravimetric Analysis (DSC-TGA), the decomposition temperature and the melting temperature of nylon membrane is high which are in the range of 477-485ᴏC and 250-254ᴏC respectively, showing it has high thermal resistance compared to other polymers. From Attenuated Total Reflection-Fourier Transform Infrared Spectrospcopy (ATR-FTIR) results, there is a presence of C=C aromatic absorption indicating the presence of violacein pigment in the nylon membrane. Furthermore, the release rate of electrospun nylon-violacein membrane is higher than casted nylon-violacein membrane. For antibacterial test, the nylon-violacein membrane showed effective inhibition against Gram-positive bacteria but negative result towards Escherichia coli (Gram-negative). By comparing these two methods, we can conclude that electospinning technique is more suitable compared to casting technique in order to fabricate desired wound dressing. Also, the use of nylon materials as fabric and violacein pigment as natural antibacterial agent in wound dressing application are beneficial for effective wound healing

Polyvinyl-alcohol/polyvinyl-pyrrolidone membranes coated with violacein pigments as antibacterial agent for wound dressing application

Polyvinyl-alcohol (PVA) and polyvinyl-pyrrolidone (PVP) are among common polymers used in producing wound dressing due to their non-toxicity, biodegradable, and hydrophilicity properties. Two methods were used to produce the PVA/PVP membranes which are casting and electrospinning. The membranes were dip-coated into violacein pigment as an antibacterial agent. The results from attenuated total reflectance Fourier transform infrared (ATR-FTIR) show that, using electrospinning, the PVA/PVP membrane was chemically bonded and crosslinked while by casting the polymers form physical bonding. Meanwhile, the tensile strength analysis gave a modulus elasticity value of electrospun membrane (4.2662 N), casted membrane (2.8029 Nm-2), electrospun-violacein membrane (2.0959 N), and casted-violacein membrane (0.7287 N). Field emission sanning electron microscopy (FESEM) shows where electrospun membranes have fibres with beads and swollen after dipped into violacein pigment. Casted membranes have no fibre and have no difference after dipped into violacein pigment. In thermal analysis, an exothermic process and multistage decomposition occurred where all the membranes showed two degradation points. The release rate of the membranes increased with time where the constant concentrations of electrospun and casted membranes were 35.176 μg and 25.176 μg respectively. The antibacterial activity gave positive results in positive control of the electrospun PVA/PVP-violacein membrane where the inhibition region yield was 30.8%. In conclusion, this study shows that electrospun membranes give better results over casted membranes and the addition of antibacterial agents gives added values for the membranes to be applied as wound dressing

Superconfinement tailors fluid flow at microscales

Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinement. We find that the strong coupling between contact-line friction and geometric confinement gives rise to a new stability regime where the maximum speed for a stable moving front exhibits a distinctive response to changes in the bounding geometry. Unstable fronts develop into drop-emitting jets controlled by thermal fluctuations. Numerical simulations reveal that the dynamics in superconfined systems is dominated by interfacial forces. Henceforth, we present a theory that quantifies our experiments in terms of the relevant interfacial length scale, which in our system is the intrinsic contact-line slip length. Our findings show that length-scale overlap can be used as a new fluid-control mechanism in strongly confined systems

Elucidating the alkene hydrogenation reaction based on cotton textile reduced graphene oxide under the influence of external electric field: Illustration of new noble method

The hydrogenation reaction of alkene is one of the most used industrial chemical process for various materials of daily life and energy consumption. This is a heterogeneous reaction and traditionally carried out by metallic catalysis. However, these conventional catalytic hydrogenations of alkene suffer from various setbacks such as catalyst poisoning, less recyclability and are environmentally unfriendly. Therefore, in recent years, researchers have been trying to develop the alternatives to metal catalysis hydrogenation of alkene. Heterogeneous catalysis under the external electric field is considered the future of green catalysis. In this paper, we report a comprehensive investigation dealing with the theoretical basis for simulating the phenomenon of heterogeneous catalysis, on a molecular level, under an external electric field. The illustration of the prospect as well as the effects of the mostly used catalytic systems, reduced graphene oxide, under the influence of external electric fields is provided. Moreover, a noble method of alkene hydrogenation reaction based on cotton textile reduced graphene oxide (CT-RGO) under the influence of an external electric field is introduced. The corresponding theoretical investigation was carried out within the framework of the density functional theory (DFT) method using first-principles calculations. The study has been carried out by elucidating DFT calculations for three different proposed catalytic systems, namely without electricity, with electricity and with an external electric field of 2 milli-Atomic unit. The obtained results indicate that adsorption energy of H2 on the CT-RGO surface is significantly higher when the electric field is applied along the bond axis, suggesting thereby that hydrogenation of alkene can be induced with CT-RGO catalyst support under external electric fields. The obtained results shed light on the effect of the external electricity field on the graphene-hydrogen complex, the activation energy of graphene radicals to achieve the transition states as well as the adsorption of the hydrogen atoms over the graphene surface. Altogether, the theoretical results presented herein suggested that the proposed catalytic system holds promise for facilitating the alkene hydrogenation under external electric fields

Gambaran dan halatuju pendidikan STEM prasekolah di Malaysia

The philosophy of national education emphasizes on the continuing education efforts that need to be made to develop the potential of each individual. In this context, the education chain needs to be integrated seamlessly from an early age to a higher level. However, initiatives involving early childhood education have received little attention, especially in science, technology, engineering and math (STEM). While STEM education is important for developing national scientific talent and forging a culture of science among the community. This is possible through the synergy of education from an early age. This paper focuses on the development of pre-school education in Malaysia and how STEM integration can occur. In addition, methods for implementing STEM content in preschool curricula and suggestions for strengthening preschool educator training in the field of STEM are also discussed