Browsing by Author "Alharbi, Ali"

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An Evaluation of The Properties of a Non-Phthalate-Based Commercial Dental Tissue Conditioner Incorporated with Antifungal Agents
(Queen Mary University of London, 2024) Alharbi, Ali; Patel, Mangala; Karpukhina, Natalia; Agha, Amani
Denture stomatitis is one of the highest prevalence among denture wearers. It is characterised by an inflammation and redness of the oral mucosa under the denture. It is a multifactorial disease that is caused by denture trauma and accompanied by candida infection. The management of this condition would involve eliminating the cause of denture trauma and treating the fungal infection. Tissue conditioners are soft denture liners that are used to treat denture stomatitis by relieving the denture bearing area from denture trauma. They consist of acrylic powder, a plasticiser and ethanol. One main disadvantage of these materials is that the leaching of plasticiser, resulting in an increase in hardness of the material. The plasticiser that was commonly used in earlier formulations was phthalate-based; however, due to their questionable biocompatibility, the use of phthalate plasticisers has been banned from Europe. The plasticiser that is used nowadays is a citrate-based or benzoate plasticiser. However, the properties of citrate or benzoate-based tissue conditioners have not been evaluated. Furthermore, the addition of antifungal agents, such as Nystatin or chlorhexidine digluconate, can enhance the treatment of denture stomatitis. Therefore, the aim of this project was to evaluate the properties of commercial citrate based (Viscogel) and benzoate based (Coe Comfort) tissue conditioners with (and without) the incorporation of drugs (Nystatin via Nystan or chlorhexidine digluconate via Corsodyl, both at 33% v/v). The commercial tissue conditioners were evaluated with respect to some physico-mechanical properties and drug release behaviour. The physico-mechanical properties included hardness (using Shore A), water absorption behavior (gravimetrically), gelation time (using an oscillating rheometer) and surface roughness (using a non-contact 3D white light profilometer). The drug and plasticiser release were evaluated using UV-Vis spectrophotometry. The samples were divided into 3 groups (i.e. Control Groups, Nystatin Incorporated Groups, and Chlorhexidine Digluconate Incorporated Groups). Each group had 2 sub-groups of Citrate-Based Tissue Conditioner (Viscogel) and Benzoate-Based Tissue Conditioner (Coe Comfort). The results showed that the hardness of Viscogel was high at baseline compared to Coe Comfort. The increase in hardness following immersion in deionised water over time was rapid in Viscogel. The incorporation of drugs resulted in softer tissue conditioners. Moreover, Viscogel had a longer gelation time compared to Coe Comfort; however, both tissue conditioners gelation time had increased after the addition of either drug. Furthermore, due to the change in opacity of both tissue conditioners during water immersions in water, it was not possible to accurately record surface roughness using a non-contact profilometer. The UV data showed that both commercial tissue conditioners have the potential to act as drug delivery systems; however, drug release from Viscogel was significantly higher than from Coe Comfort. Plasticiser (triethyl citrate) almost completely (>99%) leached out of Viscogel after 12 weeks of immersion in deionised water; whereas, only 15% of benzyl benzoate leached from Coe Comfort at 12 weeks, presumably due to the fact that triethyl citrate has a higher water solubility compared to benzyl benzoate, and benzyl benzoate having a bulkier chemical structure.
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Developing New Colorimetric Methods for Trace Metal Analysis: Evaluating Bicinchoninic Acid and Alizarin Red S for Copper and Lead Detection
(Saudi Digital Library, 2023-09-26) Alharbi, Ali; Hippler Michael
The contemporary environmental threat stemming from heavy metal contamination in Earth's ecosystems underscores the importance of early detection. Given the significant potential health risks associated with excessive copper and lead concentrations, the quest for efficient, reliable, and cost-effective detection techniques is vital. This dissertation aims to probe into alternative detection methods, namely colorimetric techniques, to overcome the economic and operational challenges of traditional methods like AAS and ICP-MS/OES. Central to this research is the evaluation of the Bicinchoninic Acid (BCA) method for detecting copper and Alizarin Red S for tracing lead. The BCA method demonstrated a substantial sensitivity, revealing a Limit of Detection (LoD) of 0.0636 mg/L for copper within mere minutes, positioning it favorably against global health standards. However, while Alizarin Red S offers a consistent colorimetric detection method for lead, its sensitivity (LoD of 0.998 mg/l) fails to align with the stringent standards set by the USEPA for drinking water. Moreover, in testing the reliability of these methods, the study incorporated absorbance measurements at optimal wavelengths and utilised a computerised analytical model. This computational approach not only eliminated human biases but also elevated the sensitivity and precision of detection. As an example, for copper, the model fitting brought about a remarkable improvement in both LoD and LoQ values. A significant portion of the research extended to practical applications, where water samples from various Sheffield locations were tested using the BCA method and compared with ICP-OES and ICP-MS. Additionally, the efficacy of the BCA technique was trialed on soil samples, outlining a detailed procedure from sample preparation to copper extraction. In conclusion, while the BCA method offers a promising alternative for copper detection in both water and soil samples, the Alizarin Red S method requires further refinement for broader applications, especially concerning drinking water. This research underscores the potential and challenges of colorimetric detection techniques in the fight against environmental contamination.
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