Synthesis and physical characterization of Carbon Quantum Dots from watermelon seed towards a biological application

Carbon Quantum Dots (CQDs) have emerged as an innovative alternative for drug delivery when integrated into hydrogels intended for wound dressings. This approach leverages the exceptional properties of CQDs, such as their ability for controlled release, precise targeting, and real-time monitoring, based on their biocompatibility and fluorescence. The synthesis of CQDs is a process that explores various methodologies, from laser ablation to hydrothermal synthesis, with the latter being the simplest and most cost-effective. Green synthesis, especially using biomass like watermelon seeds, proves advantageous from economic, environmental, and technological perspectives, contributing to circular economy principles and enabling biomedical applications. The methodology used comprises four phases. In the first phase, CQDs are synthesized using the hydrothermal method. The second phase involves physical characterization of CQDs using several techniques, including Ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), dynamic light scattering (DLS), atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and fluorescence microscopy. In the third phase, hydrogels are prepared with Polyvinyl Alcohol Fully Hydrolyzed and Hydroxypropyl Methylcellulose. The final phase involves assays to evaluate CQDs' antimicrobial activity and cytotoxicity when used in pure form or when integrated into the hydrogels. The hydrothermal synthesis study revealed a 30 mg/ml concentration of CQDs. The CQDs exhibited a round, almost spherical morphology, confirmed by SEM. In SEM, their size was 142 nm; however, DLS indicated a size of approximately 500 to 1000 nm. To make sense of these results, zeta potential analysis was conducted, showing a value of 2.35 mV trending towards zero, suggesting that the sizes found in both SEM and DLS are aggregations. AFM analysis was performed to confirm the size of CQDs, revealing a size of 10 nm. In Raman results, two predominant peaks were observed around 1340 and 1590, commonly attributed to the disordered D-band and crystalline G-band, respectively. The FTIR spectrum analysis reveals the presence of various functional groups in CQDs, such as hydroxyl, amine, C-H (sp2) and C-H (sp3) bonds, carbonyl, alkene/alkyne, amide, ether, and C-O bonds. XPS confirmed the presence of Carbon, Nitrogen, and Oxygen in CQDs. Finally, fluorescence studies demonstrated high fluorescence over time in the blue range. Regarding biological application, it was found that CQDs alone do not exhibit antimicrobial activity. On the other hand, CQDs alone and when embedded with HPMC are non-toxic at concentrations of 0.03, 0.3, and 0.5 mg/ml. Conversely, when combined with PVA, they exhibit slight toxicity. CQDs' potent photoluminescence and low cytotoxicity make them excellent candidates for hydrogel drug delivery.

• Hoofdauteur: Puchaicela Lozano, Marlene Stefanya (author)
• Formaat: bachelorThesis
• Taal: eng
• Gepubliceerd in: 2024
• Onderwerpen: Síntesis hidrotermal; Hidrogeles; Actividad antimicrobiana; Hydrothermal synthesis; Hydrogels; Antimicrobial activity
• Online toegang: http://repositorio.yachaytech.edu.ec/handle/123456789/750