Diffusion of Oligonucleotides from within Iron-Crosslinked Polyelectrolyte-Modified Alginate Beads: A Model System for Drug Release

TL;DR

This study presents an analytical model for oligonucleotide diffusion from iron-crosslinked alginate hydrogel beads, providing insights into immobilization effects and a new method to measure diffusion coefficients relevant for drug delivery systems.

Contribution

The paper introduces a validated analytical model for oligonucleotide diffusion in hydrogel beads and demonstrates a novel approach to measure diffusion coefficients within such systems.

Findings

Diffusion occurs without a surface-layer barrier due to volume immobilization.

A new simple method to measure diffusion coefficients inside hydrogels.

Citrate destabilization induces full oligonucleotide release with non-diffusional kinetics.

Abstract

We developed and experimentally verified an analytical model to describe diffusion of oligonucleotides from stable hydrogel beads. The synthesized alginate beads are Fe3+-cross-linked as well as polyelectrolyte-doped for uniformity and stability at physiological pH. Data on diffusion of oligonucleotides from inside the beads provide physical insights into the volume nature of the immobilization of a fraction of oligonucleotides due to polyelectrolyte cross-linking, i.e., the absence of the surface-layer barrier in this case. Furthermore, our results suggest a new simple approach to measuring the diffusion coefficient of the mobile oligonucleotide molecules inside hydrogel. The considered alginate beads provide a model for a well-defined component in drug release systems and for the oligonucleotide-release transduction steps in drug-delivering and biocomputing applications. This is illustrated by destabilizing the beads with citrate that induces full oligonucleotide release with non-diffusional kinetics.