Alginate hydrogels represent a significant area of research in controlled release systems, as their specific polymeric structure enables gradual release depending on external conditions such as pH, temperature, and ionic composition of the environment. Due to these properties, they are particularly suitable for applications in the pharmaceutical and food industries, where precise regulation of bioactive compound release is essential. In this master's thesis, I investigated alginate-calcium hydrogels as potential materials for controlled release of digestible carbohydrates, specifically glucose, and analyzed the release kinetics based on hydrogel composition. The objective of the research was to determine the influence of glucose, alginate, and cross-linking agent CaCl₂ concentrations on glucose release and to identify the dominant mass transport mechanisms in different formulations. The focus was on developing hydrogel systems that enable adjustable sugar release in the digestive tract, aiming to optimize formulations for improved energy delivery during endurance sports activities.
The experimental part included the preparation of alginate hydrogels with varying concentrations of glucose (15–60 %), alginate (1.5–3.5 %), and cross-linking agent CaCl₂ (0.10–0.75 %), while monitoring the impact of these parameters on glucose release kinetics in a simulated gastrointestinal environment. To quantify the release mechanisms, various mathematical models were employed, including the Higuchi, Korsmeyer-Peppas, Weibull, and first-order models. Based on the analysis of experimental data fitting, it was found that the Weibull model most accurately describes the kinetics of glucose release from hydrogels, confirming a complex mechanism involving a combination of diffusion and mechanical degradation of the hydrogel.
The results showed that a higher glucose concentration creates a larger concentration gradient between the hydrogel and the surrounding medium, leading to faster glucose release. Additionally, a higher glucose concentration hinders the interactions between alginate polymer chains, which consequently reduces the crosslinking density of the hydrogel at the same alginate and CaCl₂ concentrations. This results in a less connected structure and an increase in pore size within the polymer network, further accelerating the release. In contrast, higher concentrations of alginate and CaCl₂ promote the formation of a denser and more crosslinked polymer network, which slows down glucose release due to more difficult diffusion through smaller pores. Furthermore, the experimentally determined diffusion coefficients were compared with theoretically predicted values, revealing discrepancies that indicate the presence of additional release mechanisms, such as swelling and hydrogel erosion.
Based on these findings, targeted nutritional supplements could be developed for athletes and individuals with varying metabolic needs, ensuring optimal carbohydrate supply and reducing digestive strain during prolonged physical exertion. The development of hydrogel formulations that enable tailored sugar release based on physical activity levels could contribute to enhanced athletic performance and faster recovery.
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