Catechol-modified biomolecules in layer-by-layer assembly: a fishing net- like model to enhance stability and long-term performance

摘要

Introduction: Layer-by-layer (LBL) assembly is effective for preparation of multifunctional materials of biomedical applications in various aspects. However, LBL films can deliver some of their payload in a burst or bolus mode in the presence of external stimuli (e.g. changes in pH or ionic strength). Mytilus edulis foot proteins (Mefps) in mussels have shown excellent adhesive properties to various substrates due to contributions of catechol moieties. Herein, inspired by Mefps, heparin and polyethyleneimine (PEI) were modified with catechols to mimic the component of Mefps and perform as the polyelectrolyte for constructing a fish-net like LBL films. Such model would possibly present as a barrier layer to affect the release of LBL components. The activity and stability of loaded heparin were also investigated in detail. Materials and Methods: Briefly, heparin (Hep) and PEI was conjugated with dopamine and 3,4-dihydroxyhydrocinnamic acid respectively, using EDC/NHS method. The catechol modified heparin (Hep) and PEI was defined as Hep-C and PEI-C. Modified and traditional biomolecules were then used to further prepare the modified LBL (M-LBL) and traditional LBL (T-LBL) films, as shown in Fig. 1. The initial five or six layer preparation process was monitored via QCM-D. Heparin stability, activity and platelet adhesion test were also examined. Surface force apparatus (SFA) was used to study the surface adhesion force of different LBL layers. Results and Discussion: The real-time monitoring of LBL film construction process was shown in Fig 2. The heparin adsorption amount and desorption ratio in each layer preparation was obtained from the frequency change (AF). In T-LBL, the adsorbed heparin was not stable and desorbed almost 50% (Fig. 2A and C), but in M-LBL film, Hep-C was more stable and showed only 15% desorption (Fig. 2B and D). Moreover, M-LBL presented dramaticly enhanced stability against external stimuli (against PBS rinsing in QCM-D results). Swelling and burst release of biomolecules were seen in T-LBL film (Fig. 2C). However, no obvious burst release of LBL components was seen in M-LBL film (Fig. 2D). Stable and lower desorption of polyelectrolyte was efficient to prepare LBL film, which induced the difference in film thickness and root mean square (RMS) roughness between T-LBL and M-LBL (Fig. 2E). Fig. 3A showed the surface adhesion force of different LBL films. The strength was increased with the number of bilayer. Catechol-modified LBL films presented higher adhesion force compared with T-LBL film and would also help to enhance the stability of heparin. Heparin in M-LBL film could maintain release even after 30 days immersion in PBS (Fig. 3B). We speculate that the increased surface catechol group density (Fig. 3C) might be a reasonable contribution in supporting LBL stability and the catechol moieties would also performe as a barrier for heparin release (like the knots in fishing net). Within the long-term release of heparin in M-LBL film, Hep-C-5 could present good anti-platelet adhesion effect even after 30 days immersion in PBS (Fig. 3D). Conclusion: With the conjugation of catechol to biomolecules, a mussel inspired method of LBL film was developed. Catechol moieties introduction could effectively enhance the stability of LBL films against PBS. Such catechol modified fishing net-like LBL model could present potential for long-term biomolecule applications.