(168p) Crosslinking Alginate-Based Nanofibers for pH-Controlled Delivery: A Study Examining Crosslinking Solution pH and Co-Solvent Systems

Alginate is an excellent candidate for biomaterials due to its water-solubility and biocompatibility. However, the fabrication of alginate into electrospun nanofibers for applications in drug delivery, wound dressing, and extracellular matrices has been difficult due to the high viscosity, surface tension, and conductivity of aqueous alginate solutions. Previously, we were able to electrospin continuous alginate-based nanofibers using generally regarded as safe (GRAS) additives and an aqueous solvent. While alginate is known to crosslink with biocompatible calcium ions under mild conditions, the published method for crosslinking alginate-based fibers involves using ethanol as a pretreatment and/or co-solvent to prevent the dissolution of the alginate fibers in the aqueous crosslinking solution. Unfortunately, using ethanol in biomedical applications is not optimal because it may damage various mammalian cells, bacterial cells, and proteins. In this work, we explored the use of aqueous crosslinking solutions that had an acidic, neutral, and basic pH value as well as glycerol as an alternative co-solvent to create chemically resilient alginate-based nanofibers. We analyzed changes in chemical compositions of fibers before and after crosslinking using Fourier Transform Infrared spectroscopy to analyze chemical groups and thermogravimetric analysis to determine mass composition. We found that our crosslinking systems could influence the diffusion of the carrier polymer and surfactant out of the fiber. We then used scanning electron microscopy to image and determine the stability of the fibers in acidic buffer, DI water, and phosphate buffer saline (PBS). Overall, our proposed crosslinking systems produced fibers that were stable in acid buffer and DI water. In PBS, the fibers tended to swell and merge into a film. Even more, we were able to demonstrate targeted delivery in a simulated gastrointestinal tract using fluorescent beads as a model for the release of encapsulated active ingredients.