In vitro hydrogel-cell model for pharmacokinetic analysis

Abstract Purpose: Understanding nanoparticle interactions and transport across hydrogel matrices and their associated interface with cellular layers is essential for designing effective drug delivery systems, tissue engineering scaffolds, and biomaterial platforms. Therefore, robust in vitro models that simulate complex extracellular matrices and that support quantitative transport analysis are crucial as preclinical screening tools. Methods: This study presents the development of a versatile, multicomponent in vitro hydrogel-cell model designed to evaluate nanoparticle transport dynamics and boundary layer interactions, demonstrated here using an optimised synthetic vitreous humour analogue and an adherent retinal cell (ARPE-19) layer as a representative model. This is achieved by exploiting the capabilities of an emerging label-free nanoparticle tracking platform, which can dynamically characterise the effects of matrix complexity, protein interactions, and cellular presence on gold nanoparticle transport in real time. Results: The model effectively characterised how increasing system complexity influenced nanoparticle diffusion. In serum-rich media, nanoparticles incubated for 24 h showed significantly higher diffusion rates when compared to serum-free media, suggesting the presence of nanoparticle-protein interactions that prevented particle-particle aggregation. The introduction of an ARPE-19 cell layer further increased biological complexity reflected by greater variability in nanoparticle diffusion. Finally, the addition of the hydrogel matrix resulted in a bimodal diffusion distribution, successfully resolving the distinct aqueous and gel phase microenvironments within the model. Conclusion: This experimental model provides a quantitative framework for evaluating how nanoentity properties govern carrier-protein interactions, matrix diffusion, and target cell delivery. Ultimately, these insights will inform nanocarrier design to control transport across complex biomaterials and biological interfaces.