A synthetic and computational investigation of pentacycloundecane amino acid derivatives.

Thesis (M.Sc.)-University of KwaZulu-Natal, 2005.Computational studies have shown that cage skeletons (7) have the tendency to impose a 310-helix as well as an áL-helix on the polypepeptide chain. Residues such as 7 are the useful tools for study of the conformational preferences of peptide models, the design of peptide analogues with improved pharmacokinetics profiles and the development of pharmacophore models. Synthesis of pentacycloundecane amino acid analogue suitable for peptide synthesis would enable us to verify the computational predictions and to contribute to this very active field of research. The sterically hindered 8-amino-pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8-carboxylic acid (7) was synthesised by hydrolysis of the novel bis-Boc protected pentacycloundecane-hydantoin (30). Progress to incorporate 7 into a non-natural peptides is reported. A computational investigation on the regioselective acetylation of hydantoin derivatives which includes PCU hydantoin, 5.5-dimethylhydantoin and 5-methylhydantoin is also reported. The results of the computational investigation initiated the regioselective synthesis of the mono-Boc and bis-Boc derivatives of 5,5-dimethylhydantoin and 5-methylhydantoin. These compounds have not been reported before

Synthesis and growth dynamics study of silver nanoparticles

A thesis presented in fulfillment of the requirement for the award of the degree of Doctor of Philosophy in the Department of Chemistry at the University of Zululand, South Africa, 2009.The concept of shape-controlled synthesis of metal nanoparticles is investigated by considering the growth mechanism of metal nanoparticles. This thesis is divided into four chapters, chapter one presents a general introduction about various physiochemical aspects of nanornaterials. The different characteristic properties of nanomaterials, their chemically synthesized protocols, characterization techniques, and their applications are discussed in brief. Based on these reviews, the context scope and objective of the present work are outlined. Chapter two deals with the theory of kinetically growth of nanoparticles. The basic optical properties of metal nanoparticles as well as the structural evolution of nanoparticles are also mentioned in this chapter In Chapter three the synthesis of silver nanoparticles with varying morphologies using different synthetic routes are described in detail. Silver nanowires were synthesized by an aqueous route using dimethyl formamide (DMF) as the reducing agent in the presence of poly (iV-vinylpyrrolidone) (PVP) without the addition of seeds. The products were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM). This work was followed by a profound dig-out, to try and comprehend the mechanism for reduction and the kinetics of the reduction of silver nitrate to silver nanoparticles. It was established that in the alkaline medium the reduction of AgNC>3 is enhanced, which resulted to the formation of rod-like silver nanoparticles which were confirmed by TEM and UV-visible spectroscopy. Silver nanodendrites, with an elongated central backbone and distinguished branches were synthesized by die reduction of silver nitrate with formamide using polyvinyl pyrrolidone (PVP) as the surfactant. The drastic evolution of the dendritic nanostructures was due to the variation of the concentration of the reactants. At low PVP concentration isotropic silver nanoparticles are visible in the transmission electron microscopy (TEM) images. The morphological evolution is confirmed by the optical measurements. The growth mechanism for the nanodendrites is discussed in some detail. The use of single molecular precursors is a common route to synthesize nanostructured materials. There have been relatively few reports for the use of sophisticated precursors to synthesize metal nanoparticles at high temperatures. The N-(Diisoproppylthiophosphoryl) thiourea complexes of silver were synthesised using a previously reported literature method. The complexes were then used as single molecule precursors for the synthesis of hexadecylamine (HDA) and tri-octylphosphine oxide (TOPO) capped silver nanoparticles. The absorption spectra of the HDA and TOPO-capped silver nanoparticles exhibit surface plasmon resonance (SPR) absorption in 400-420 nm regions. In chapter four, the morphological evolution of silver nanoparticles prompted the development of a Density Function Theory (DFT) model to understand the adsorption of Pyrrolidinone on the surface of silver and gold nanoparticles. The interaction between PVP and the metal atoms on the surface of silver and gold nanoparticles, was studied using Surface Enhanced Raman Spectroscopy (SERS) and modeled using Density Function Theory (DFT). The SERS analysis was carried out on pyrrolidinone and N-methyl pyrrolidinone in silver and gold colloids, whereas the assignments of bands in the pyrrolidinone molecules were performed by density function theory (DFT) quantum chemical calculations.The University ofZululand and National Research Foundatio

Assessing the antibacterial properties of eggshell-titanium powder

The global distribution of oral diseases caused by bacterial and the severity of their consequences constitute a pandemic condition.The present paper reports on the antibacterial properties of a modified eggshell and titanium dioxide using the mechanochemical method. EB@TiO2 was modified and characterized using X-raydiffraction (XRD) while the degradation condition was studied using Thermogravimetric analysis (TGA).The inhibitory properties of EB@TiO2at differentconcentrations (2:1; 3:1 and 4: 1) against both Grampositive (E. coli) and negative bacterial (B. Cereus)strain were studied the using disk diffusion method.The XRD result confirmed the presence of a thermodynamically stable calcite structure, which is indicative of calcium carbonate. The diffraction peak of the XRD at 2θ = 29.5o suggests the deposition of TiO2 on the surface of CaCo3. TGA curves shows the decomposition of anatase form of titanium dioxide and calcium carbonate. The study evidently shows the antibacterial activities of EB@TiO2 against Escherichia coli and B. Cereus. The salient feature of the study finding is that modifying eggshells with titanium dioxide improves the antibacterial properties, and thus offers a promising role for the development of potent

Comparative Analysis of Abrasive Materials and Polishing System on the Surface Roughness of Heat-Polymerized Acrylic Resins

Abstract Objective The aim of this in vitro experiment was to see how the operator's manual skills, polishing equipment, and abrasive materials affected the surface roughness of denture base resins. Materials and Methods Forty polymethyl methacrylate (PMMA) specimens were created and polished by using two different polishing systems, namely hand and automatic polishing machines. Three operators hand-polished 30 of specimens with eggshell powder and pumice, while 10 were automatically polished (n = 5). A profilometer was used to determine the average surface roughness (Ra) after polishing. The Ra values for the specimens hand-polished were analyzed by using paired sample testing. The Ra values for all polished specimens were analyzed by using a one-way ANOVA. Differences between the two abrasive materials as well as the polishing system were determined by using the Bonferonni tests (p = 0.05). Results and Conclusion For the PMMA specimens hand-polished, there was a strong connection in the Ra values. There were also significant variations in the Ra values across the three operators (p &lt; 0.001). The automated technique created a substantially smoother surface than the traditional technique (p = 0.001). The greatest Ra values (0.20 µm) were found in specimens polished traditionally by using pumice, whereas the lowest Ra values (0.04 µm) were found in specimens polished mechanically with eggshell powder. The automated polishing system was the most effective polishing method when the Ra values were connected to the level of smoothness.</jats:p

Remineralization Potential of a Modified Eggshell–Titanium Composite-Scanning Electron Microscope Study

Abstract Objectives This article reports the remineralization potential of a modified eggshell–titanium dioxide (EB-TiO2) composite in the management of DH. Materials and Methods The prepared composite was further characterized using different techniques such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and field scanning electron microscopy (FSEM) to establish the modification. Forty freshly extracted bovine anterior teeth were used to evaluate the dentin tubule remineralization potential of EB-TiO2. Each tooth was sectioned mesiodistally to obtain dentin blocks. The dentin blocks were subsequently agitated in 4% wt. citric acid for 2 minutes to simulate sensitive tooth. Each dentin block was randomly assigned to five groups, namely Group 1: untreated, Group 2: EB alone, Group 3: EB-TiO2 treated, and Group 4: Colgate Sensitive, and Group 5: Sensodyne treated (n = 8) that were then subjected to remineralization protocol. Results Both the XRD and FTIR images confirm the surface medication of EB-TiO2. The TEM revealed a nonhomogeneous structure with an average particle size of 65 nm. FSEM further was used to observe the remineralization capabilities of the samples. The FSEM image of the dentin specimens treated with EB-TiO2 shows complete remineralization of the dentin tubules, which remain intact postacidic exposure. Conclusions This study confirmed that EB-TiO2 composite effectively remineralizes dentin tubules. More so, the composite could be a cheaper and more efficient therapy material in the management of DH.</jats:p

Fabrication of smartphone-based colorimetric device for detection of water leaks

South Africa is a water-scarce country due to the shortage of rainfall.&nbsp; This scarcity is further exacerbated by the loss of water through leakage from faulty pipes. This paper reports on the use of a simple microfluidic device in the early detection of water leakages. The microfluidic paper-based device (µPADs) were prepared by printing patterns of wax (100 μm width) on the paper surface and melting the wax into the paper to form hydrophobic barriers. Solutions of lower to higher pH were also prepared and were introduced to the chlorophenol red test strips and a range of colours from yellow (lower pH) to purple (higher pH) were obtained. The digital images obtained with the μPADs were analysed using the CIELab colour system. The optimized pH range was wider than the typical grayscale-based image analysis and was successful for a wide pH range of 2–12. The QR codes attached to the strips enable tracking to obtain the real-time location from which leakage was detected. The study conclusively shows that the combination of digital image analysis and a μPAD device is highly efficient for quantitative analysis, and thus useful for the detection of household water leaks

A novel application of nano eggshell/titanium dioxide composite on occluding dentine tubules: an in vitro study

Abstract To synthesize Nano eggshell-titanium-dioxide (EB@TiO2) biocomposite and to evaluate its effectiveness in occluding opened dentine tubules. EB@TiO2 was synthesized and characterized using X-ray diffraction (XRD), and Transmission Electron Microscope (TEM). Sixteen simulated bovine dentine discs were prepared and randomly assigned into four groups according to the following treatment (n = 4): Group 1: No treatment; Group 2: eggshell powder; Group 3: EB@TiO2; Group 4: Sensodyne. These were then agitated in a solution of 1g powder and 40mL water for 3hours. Thereafter, each dentine discs from the respective groups were post-treated for 5 min with 2wt% citric acid to test their acid resistant characteristics. Scanning Electron Microscope (SEM) was used to observe the effectiveness of occluded dentine pre-and post-treatment. The cytotoxicity of the synthesized EB@TiO2 was tested using NIH 3T3 assay. ANOVA was used to evaluate the mean values of the occluded area ratio and the data of MTS assay. This was followed by a multi-comparison test with Bonferroni correction (α = .05). The XRD confirmed that EB@TiO2 was successfully modified through ball-milling. The TEM revealed the presence of both spherical and irregular particle shape powders. The SEM result showed that EB@TiO2 could effectively occlude open dentine tubules. Equally, the result demonstrated that EB@TiO2 exhibited the highest acid resistant stability post-treatment. NIH 3T3 assay identified that EB@TiO2 had little effect on the NIH 3T3 cell line even at the highest concentration of 100µg/ml. This study suggests that the application of EB@TiO2 effectively occluded dentine tubules and the occlusion showed a high acid resistant stability