Prof. Dr. Henning Menzel (Braunschweig, DE), Nils Meier (Braunschweig, DE), Leonie Berten-Schunk (Braunschweig, DE), Professor Heike Bunjes (Braunschweig, DE), Dr. Yvonne Roger (Hannover, DE), Professor Andrea Hoffmann (Hannover, DE)
Abstract text (incl. figure legends and references)
Introduction
Drug delivery systems on implants that allow the release of growth factors are an approach to in-situ tissue engineering.1 After modification with chitosan grafted with PCL (CS-g-PCL) implants can be functionalized with polyanions and dispersions of drug loaded nanoparticles Layer-by-Layer (LbL).2 Such coatings can indeed release biologically active amounts of growth factor3, however, a more sustained release is desired.
Objectives
The LbL method allows applying extra layers to the drug release system, which then probably serve as "barrier layer" to retard the release. Weak and strong polyanions as well as liposomes were tested as such barrier layers.
Materials & methods
Electrospun PCL fiber mats were modified with CS-g-PCL.1 Nanoparticular hydrogels prepared from solutions of chitosan (CS), TGF-b and tripolyphosphate (TPP)2 were used to apply the drug delivery system. Additional layers of polystyrenesulfonate (PSS), alginate (Alg), carboxymethylcellulose (CMC) as well as liposomes prepared from Lipoid E80 were applied as extra layers.
Results
The polyanions gave an increase in layer thickness. However, streaming potential and XPS measurements both indicate that CS and polyanion layers strongly interpenetrate while the liposomes form separated layers which are more promising in this respect. All samples released incorporated TGF-b3 with a burst release.
Conclusion
LbL allows the application of additional layers, but they strongly penetrate the active layers and therefore do not act as barriers to drug diffusion and do not retard release. Liposomes are not interpenetrating, however, the lipid used here was not stable enough as a coating.
References
1 de Cassan et al, Colloids Surf. B Biointerfaces, 163, 309-320 (2018)
2 Sydow et al. Biomater. Sci. 7, 233 - 246 (2019)
3 Sundermann et al. (2022). ACS Biomater. Sci. Eng. DOI: 10.1021/acsbiomaterials.1c01585
Acknowledgement
Funded by DFG in the Research Unit 2180 "Graded Implants for Tendon-Bone Junctions".