Quantification and characterization of water within drug-eluting beads

This work describes the analysis and characterisation of polyvinylalcohol (PVA)-based hydrogel polymer beads, specifically focussing on the quantitative and qualitative aspects of water within such beads in the absence and presence of three drugs; doxorubicin and irinotecan (already utilised as medicines) and finally, imipramine (for comparison). Using optical microscopy the size of the beads in the presence of increasing amounts of imipramine decreased (121–79 μm) as water was displaced, demonstrating the presence of drug-bead interactions.

Highlights

This work is on the quantitative and qualitative analysis of water in polymer beads.

Three drugs were also added to the beads to consider drug-bead interactions.

TGA confirmed the total water content to range from 96.8% to only 91.7% with drug.

DSC separated the water into bound (non-freezing), loosely bound and unbound forms.

This study discusses the changes in water content in the presence of model drugs.

Thermogravimetric analysis (TGA) permitted determination of the total water content within the beads, ranging from beads alone that contained 96.8% water, through to beads formulated with irinotecan that contained only 91.7% water. Differential scanning calorimetry (DSC) was utilised to investigate water present within their hydrogel structures, separated into bound (non-freezing), loosely bound and unbound forms. For imipramine and irinotecan (25 mg/mL) beads there was little impact on the relative ratio of bound, loosely bound and free water within the structure. For doxorubicin and the higher drug loaded irinotecan a distinct decrease in overall water content was seen.

This study confirms the ability of TGA and DSC to characterise the differing types of water within the beads and indicates the relative changes in water content in the presence of these three drugs. It is clearly beneficial to characterise states of water in such hydrogel systems to better understand drug loading and release in the context of cancer treatment.

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Article information: Shamsuddeen A. Ahmad, A.L. Lewis, G. Parkes, Y. Tang, L.J. Waters, Quantification and characterization of water within drug-eluting beads, Polymer, Volume 235, 2021. https://doi.org/10.1016/j.polymer.2021.124287.