Bien 290: Bioengineering Measurements Lab
Fall 2025
Optimization of Alginate-Based Hydrogel Beads for Controlled Dye Releasing Using The Design of Experiments (DoE)
Module 2: Thursday, September 18th and 25th, October 2nd and 9th 2025
Felix Gamper, Rachel Jiang, McGill IDs (261200955, 261134922), Bien 290 Group 13
Abstract:
This study applied a Design of Experiments (DoE) framework to optimize alginate bead formulation parameters for controlled drug release. Three key factors—alginate concentration (1% vs 3%), syringe type (3 mL vs 18G), and surfactant presence (Tween® 80 yes/no)—were varied to evaluate effects on bead morphology, loading capacity, and release kinetics. Optimized beads were then used to investigate the release behavior. of two model compounds, tartrazine and erythrosine, representing different molecular weights and solubilities.
Results (finish this after the rest of the report)
Introduction:
Hydrogels are three-dimensional network materials with a high-water content (typically greater than 10%). Because of their excellent biocompatibility, flexibility, and tunable physical and chemical properties, they have been widely applied in biomedical engineering for drug encapsulation, tissue scaffolding, and cell delivery systems. Hydrogels can be either synthetically produced or naturally derived.
Among natural hydrogels, alginate is one of the most representative examples. Alginate is a polysaccharide obtained from brown algae that can form. a stable three-dimensional gel network through ionic crosslinking with divalent calcium ions (Ca²⁺) under physiologically relevant and non-denaturing conditions. This crosslinking process enables the efficient encapsulation of active compounds without compromising their biological function, while allowing researchers to precisely control bead morphology, mechanical strength, and drug release rate by adjusting parameters such as alginate concentration, calcium ion strength, and the presence of surfactants.
Due to these characteristics, alginate-based hydrogels are commonly used as in vitro models for controlled drug release, providing an effective platform. to simulate slow-release mechanisms that occur in biological systems and to support the design and optimization of advanced drug delivery formulations.
In bioengineering experiments, experimental outcomes are often influenced by multiple factors acting simultaneously, and the interactions among these factors are frequently nonlinear and complex. The traditional One-Factor-at-a-Time (OFAT) approach, while straightforward, is inefficient and limited in its ability to capture such coupled effects.
The Design of Experiments (DoE) methodology provides a more systematic and statistically grounded framework that allows researchers to extract the maximum amount of information with the minimum number of experiments. In this study, a full factorial design was employed to simultaneously evaluate the effects of three key parameters—alginate concentration, syringe type, and the presence or absence of the surfactant Tween®80—on bead morphology and drug release performance. Through this approach, it is possible not only to identify the main effects of each factor but also to quantify their interactions, thereby offering a robust basis for optimizing formulation conditions and improving the controllability of drug release.
In this study, the Design of Experiments (DoE) approach was applied to investigate three key variables: alginate concentration (1% and 3%), syringe type (3 mL vs 18G), and the presence or absence of the surfactant Tween®80. Alginate solutions prepared under these different conditions were dropped into a 1% calcium chloride (CaCl₂) solution to form. crosslinked alginate beads. The spectrophotometer was used to measure the absorbance of the resulting solutions, allowing the determination of dye loading capacity (tartrazine/erythrosine encapsulation efficiency). Meanwhile, images of the beads were captured using the Chemidoc imaging system, and their circularity and uniformity were analyzed with ImageJ software, enabling quantitative evaluation of how each variable affected the bead morphology and overall performance.
Tartrazine and erythrosine were used as model compounds to evaluate the release kinetics of alginate-based hydrogel beads. These two dyes exhibit distinct physical and chemical properties, making them ideal for investigating how molecular structure influences diffusion and release behavior. Tartrazine, a smaller, highly polar, and water-soluble molecule, represents a fast-diffusing compound, whereas erythrosine, with its larger molecular size and greater hydrophobicity, represents a slow-releasing compound. By comparing their release profiles under identical bead formulations, this study provides deeper insight into the diffusion-controlled mechanisms that govern the drug release process within alginate hydrogel systems.
The primary objectives of this study were to characterize the morphology of alginate beads under different experimental conditions (including circularity and uniformity), to determine the loading capacity, and to investigate the release kinetics of tartrazine and erythrosine from the optimized bead formulations.
The working hypothesis is…
Materials and Methods:
Results:
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