Collagen-based matrices with axially oriented pores activated via plasma and decorated with polyelectrolyte microcapsules for drug delivery

Introduction Collagen matrices with properly designed porous structure have the potential to improve the regeneration of tissues like peripheral nerves, by physically supporting and guiding the growth of tissue structures across the site of injury [1]. Due to the formation of amide bonds during cross-linking of the scaffold, an abatement of groups naturally present on the collagen chains (e.g. NH2, COOH) occurs. Such groups are generally used as anchor moieties for biomolecules or drug delivery systems like microcapsules (MCPs) [2]. In this work, cylindrical collagen-based scaffolds with axially oriented pores, useful for peripheral nerve regeneration, were prepared and then subjected to plasma processing [3], with the aim of grafting polar groups on them. Materials and methods Synthesis of scaffolds- Collagen-based scaffolds with axially oriented pores were synthesized from an aqueous suspension of Type I collagen (3 wt%, Semed S, Kensey Nash Corp.) and dehydrothermally crosslinked, as described in the literature [1]. Synthesis of MCPs- Anionic and cationic capsules, carrying FITC- and RITC-labeled dextrans into the cavities, respectively, were obtained using the LbL method [2]. Plasma processes- performed at 13.56 MHz radio frequency (rf) were fed with N2 and H2O vapors by changing the gas feed composition. The total gas flow was maintained at 15 sccm, at 150 mTorr and 30 W with variable treatment time. Results and discussion Plasma treatments imparted immediate hydrophilicity and ability to absorb water to the scaffolds. For comparison, it should be noted that untreated crosslinked collagen scaffolds did not absorb water. Plasma treatments were able to effectively change the chemical characteristics of both the external and internal surface of the scaffolds. After MCPs immobilization, fluorescence microscopy clearly demonstrated that: surfaces functionalized by means of NH2 groups are able to support the immobilization of negatively charged MCPs; COOH plasma functionalized materials are able to support positively charged ones. Conclusions This paper demonstrates that plasma processing of cross-linked collagen is a powerful tool to enhance MCPs immobilization. Acknowledgments The Italian Regional project PON 02 00563 3448479 RINOVATIS for funding