Saudi Cultural Missions Theses & Dissertations
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Item Restricted Understanding the Structural and the Mechanical Properties of Bone(Saudi Digital Library, 2023-12-12) Almoshawah, Yasser Ali H; Rehman, Ihtesham Ur; Dall’Ara, EnricoOsteoarthritis (OA) is one of the most common chronic diseases characterised by a disorder in the subchondral bone (SB), cartilage damage, and osteophyte formation. Due to an inadequate understanding of the mechanism of disease pathology, no treatment is currently available to effectively prevent the initiation or progression of OA, and severe treatment modalities, such as hip joint replacement, are currently available. A better understanding of the chemical and mechanical properties of bone will also help improve OA’s diagnosis. This study aims to investigate the chemical properties of SB from the femoral head (FH) of patients with OA through an invasive and label-free approach. Vibrational spectroscopy has shown the potential to provide diagnostic information. A combination of Raman, Fourier-Transform Infrared (FTIR) spectroscopic, and Photoacoustic Fourier Transform Infrared Spectroscopy (FTIR-PAS) methods were used for the chemical analysis of samples. Principal Component Analysis (PCA) was used to identify variations within different tissue of OA bone. Linear Discriminant Analysis (LDA) was used to predict pathogenic markers with high sensitivity (Sn) and specificity (Sp). The combination of Infrared and Raman spectroscopy with chemometrics were very helpful in identifying new spectral markers to differentiate OA bone samples. Initially, preliminary studies were conducted on bovine bones, which are almost comparable to human bones. They were applied on Raman and FTIR to study the chemical composition concerning the different cutting directions to prevent mistakes and enhance the primary study. For Raman, the PCA bovine result showed a perfect clustering, with PC-1 and PC-2 accounting for 92% of the variation, resulting in excellent Sn and Sp of 100%. The results for FTIR also exhibited perfect clustering, with PC-1 and PC-4 accounting for 80% of the variance, resulting in 100% Sn and Sp. Raman, FTIR and FTIR-PAS have identified structural and compositional changes in OA compared to tissue-specific (subregion). Significant statistical differences were detected among the bone types, including organic and inorganic composites. The results of the PCA in all vibrational spectroscopy showed that the PCA had good clustering, accounting for 74, 75, and 86% of the variation for Raman, FTIR and FTIR-PAS, respectively, leading to excellent Sn and Sp of 100%, representing the whole spectrum. Furthermore, as the aetiology and pathogenesis of OA are not fully understood, measuring the mechanical properties of bone by applying nanoindentation to FH to extract the mechanical properties is essential in order to understand the disease profile. The mechanical results show that the reduced modulus (𝐸𝑟) and the hardness (H) averaged out to be (16.07±3.05 GPa) and (0.56±0.107 GPa), respectively. The average elastic modulus (𝐸𝑏) of bone was measured to be (14.84±2.85 GPa), whereas the indentation modulus (E_ind) was (16.31±3.14 GPa). Compared to the other bone types, the osteophyte (Osteo) bone has the lowest value, while the cortical bone (Cort) has the highest value. The parameters in RS and FTIR confirm that increasing mineralisation ratios in bone types were correlated with a decreased 𝐸𝑏 and vice versa. In conclusion, vibrational spectroscopy is a highly effective method for identifying chemical changes associated with different subtypes of bone tissue disease. This study confirms its significance in evaluating both chemical and mechanical changes in cases of severe OA affecting the human FH helping to understand the reasons for the disease process and enable an improved treatment modality. Furthermore, these findings will assist the research community in identifying regions of the skeleton where the local physical and chemical properties of bone, in addition to the mechanical properties, should be characterised during the preclinical optimisation process of treatments for skeletal diseases.31 0Item Restricted Chemical and Mechanical Sensing of Graphene and MoS2 2D Materials(Saudi Digital Library, 2023-08-10) Alshammari, Majed Fahad; Dalton, AlanSensing technologies have garnered significant attention owing to their significance in both present-day and future contexts. Numerous industries, particularly the food and health- care sectors, are actively pursuing the development of high-performance sensors. These sensors are crucial in enhancing quality standards within these sectors. The miniaturiza- tion of sensor technologies utilizing conventional semiconductors is approaching its inher- ent limitations, wherein the ability to build them at increasingly smaller scales is becoming increasingly challenging while still ensuring optimal performance. Nanotechnologies have given rise to a novel discipline known as 2D material science, which involves the fabrication of nanoscale thin materials exhibiting distinctive structures and electrical properties. Graphene and MoS2, belonging to the TMDs group, are well recog- nized as prominent 2D materials. These materials exhibit distinctive mechanical, elec- trical, and thermal characteristics, rendering them highly suitable for the development of effective nanoscale sensors. This work employs graphene and MoS2 as sensors, with graphene balls serving as mech- anical sensors and MoS2 as chemical sensors. The paper elucidates the synthesis of these two-dimensional materials and outlines the procedure for evaluating the sensing capabil- ities of each material. I kindly request that you rewrite your text to adhere to academic standards. In this study, a two-dimensional (2D) MoS2 flake is employed as a chem- ical sensor to investigate its sensitivity towards ethanol and IPA compounds upon their introduction into the surface of MoS2. Ultimately, the objective is to evaluate the mech- anical sensing capabilities of the graphene ball by employing an Atomic Force Microscope (AFM) tip to induce strain in the graphene structure and measure the resulting electrical fluctuations.8 0Item Restricted USE OF PHOTO-ACTIVATED DISINFECTION (PAD) METHOD FOR THE MANAGEMENT OF DENTAL CARIES BIOFILMS(2022) Almansour, Khulood; Banerjee, Avijit; Moyes, DavidBackground: Oral microbial diversity presents significant challenges to caries model and disinfection protocol development. The production of bacterial and fungal mixed biofilms is a particular concern. Notably, changing local environmental conditions is one of the primary activities of a biofilm. Therefore, for a better understanding of the interaction between fungi and bacteria in dental biofilms, it is important to design physiologically relevant multikingdom biofilms that mimic cariogenic activity and evaluate the impact of antimicrobial system on these cariogenic biofilm models. Objectives: The objectives in this study are divided into sections. Development of a cariogenic multispecies biofilm model in the presence and absence of the oral fungi Candida albicans using plaque and cariogenic species, and development of a cariogenic multispecies biofilm model in the presence and absence of plaque and cariogenic species. The influence of Candida albicans and sucrose on the biofilm models will next be evaluated, and the cariogenic potential of polymicrobial plaque biofilm models will be tested. Finally, the antimicrobial and post antimicrobial effect of PAD on the developed multispecies cariogenic model will be investigated. Materials and methods: Biofilms were developed using a combination of “commensal” (Streptococcus oralis, Actinomyces oris, Actinomyces viscosus) and caries-associated (Streptococcus mutans, Lactobacillus acidophilus) oral bacteria as well as the fungus Candida albicans. Bacteria and C. albicans were grown to stationary phase, then washed and resuspended in either RPMI or artificial saliva containing mucin. Bacteria were resuspended at 1X106 CFU/mL and C. albicans 1X105 CFU/mL. Single- and polymicrobial biofilms were then prepared in 24 well plates (1 microbe, 4 bacteria, 5 bacteria, 5 bacteria with L. acidophilus added 3rd day) with and without C. albicans and left for 5 or 10 days, with media changed daily for the first 5days. Then biomass and metabolic activity were measured using Crystal violet and XTT assays respectively to investigate the biofilms developed. For evaluating the impact of sucrose and C. albicans on the developed multispecies biofilm a selection of biofilm communities was prepared (4 bacteria (4), 5 bacteria (5L), 5 bacteria with L. acidophilus added third day (5L3)) with/without C. albicans and grown on hydroxyapatite discs for 10 days, with artificial saliva (AS) ± 0.2 % sucrose. AS was changed daily days 1-5, then left day 5-10. Biomass, metabolic activity, pH level and microbial abundance were measured using Crystal violet, XTT assays, pH meter and qPCR respectively. To determine cariogenic activity, 5L3 biofilms ± C. albicans were grown on polished human enamel and characterised by non-contact laser profilometry to measure surface roughness (Sa), Raman spectroscopy and Knoop microhardness (KHN). Further, to evaluate the Photoactive disinfection (PAD) impact, the multispecies biofilms were grown on hydroxyapatite discs in 24 opaque well plates. The media on the biofilms was changed daily for five days and then was not changed for five days as previously mentioned, resulting in biofilms that were 10 days old. Each experiment for biomass and metabolic activity, was conducted in triplicate, while microbial composition utilising qPCR was conducted twice. On day 10, all analyses were conducted. Biofilm biomass, metabolic activity and the species composition of biofilm was analysed utilising Crystal violet, XTT assays and quantitative polymerase chain reaction qPCR respectively. Results: Significantly higher biomass was observed in multikingdom biofilms aged 10 days grown on polystyrene substrate in artificial saliva compared to RPMI-culture media. While no difference in metabolic activity was observed in the same group. When multispecies biofilms grown on polished enamel substrate in AS media with and without 0.2 % sucrose, biofilms formed successfully. Sucrose affected the species composition, with S. mutans and C. albicans being more abundant in biofilms with sucrose versus non-sucrose media. However, in the absence of sucrose, S. mutans was reduced in Candida-containing versus Candida-free biofilms. A. oris and A. viscosus were reduced in Candida-containing biofilms in sucrose versus non-sucrose media. S. oralis abundance was higher in Candida-containing versus Candida-free biofilms and further increased in sucrose-containing media. In all biofilms and media, there was an increase surface roughness (Sa) of enamel. However, the 5L3 community with sucrose but without Candida resulted in significantly higher surface roughness (Sa). Raman spectroscopy indicated a significant loss of mineral content. The surface Knoop microhardness (KHN) was decreased in sucrose-containing biofilms. Furthermore, Candida-free biofilms with no sucrose had lower Knoop microhardness level (KHN) than Candida-containing biofilms. All biofilm media examined had a lower pH on day 10 than on day 1, with the sucrose groups more acidic medium (low pH value) than non-sucrose and the Candida-containing biofilms less acidic than Candida-free biofilms. PAD affected the biomass of all multikingdom biofilms while in Candida-free biofilms only biofilm 4 was affected significantly. Viability of all biofilm models were reduced significantly after PAD treatment and PAD showed an effect after 5 days of treatment. PAD showed an effect on the composition of all groups treated, resulting in biofilms composed mainly of Actinomyces seen in most biofilms 4, 5, 5, 5C and 5L3C. Conclusions: Artificial saliva containing mucin can provide a favourable environment for the growth of multikingdom biofilms in vitro. The presence of C. albicans with sucrose induces changes in the composition of biofilm species, which affects biofilm cariogenicity. The polymicrobial biofilms developed in this study formed cariogenic communities on the enamel surfaces within 10 days. Multikingdom biofilms and sucrose influence changes in biofilm species composition, which has an effect on biofilm cariogenicity. C. albicans decreases demineralisation while sucrose increases it. PAD therapy showed an effect on multispecies biofilm viability reduction. Tolonium chloride was worth mentioning since it had an effect on some biofilms when applied alone.25 0