Abstract
Layer-by-Layer (LbL) self-assembly has been investigated for several decades. However, the conventional LbL method has performance problems on the chair-side caused by its cumbersome and time-consuming process. Thus, we investigate a new LbL self-assembly technique for the fast and high efficient preparation process based on the brush. The multilayer films fabricated by simple sequential brushing of polyelectrolyte solutions are compared to the classical dipping method. We characterize the multilayer films by characteristics such as their morphology and thickness, and compare them against those of the classic method by profilometry, atomic force microscopy. We prepare multilayer films with biocompatible polyelectrolytes, chitosan, and alginate incorporated with a hydrophobic drug carrier. For the drug carrier, a poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) block copolymer is introduced to construct micelles containing dexamethasone, which is a well-known osteogenesis-inducing drug. The hydrogen bonding behavior between adjacent layers and micelles is investigated by Fourier transform infrared spectroscopy. Additionally, we analyze the release profiles, degradation profiles and toxicity of the multilayer films for biomedical applications. From these results, we can identify the brushing LbL method as a reliable and more efficient multilayer film-construction process compared to conventional dipping LbL, especially for practical applications in dental and clinical situations.
Highlights
Amphiphilic block copolymers, which have hydrophobic and hydrophilic segments with different solubilities in their structure, have been widely studied for their ability to self-assemble into polymeric micellar structures in selective solutions
Based on this unique advantages, there have been many attempts to incorporate polymeric nano particles or micelles into multilayer films fabricated by LbL assembly for hydrophobic drug delivery systems
We have introduced a brush-based LbL self-assembly method, described in detail in the schematic illustration in Fig. 1a, where purple represents cations such as chitosan, green represents anions like alginate, and the yellow round particles represent block copolymer micelles containing dexamethasone
Summary
Amphiphilic block copolymers, which have hydrophobic and hydrophilic segments with different solubilities in their structure, have been widely studied for their ability to self-assemble into polymeric micellar structures in selective solutions. Counter materials by electrostatic interactions, hydrogen bonding, hydrophobic interactions, or covalent bonding[12,22], as the major driving forces of LbL self-assembly are founded on intermolecular interactions, it is a very powerful method for adjusting the characteristics of nano-sized structure of the thin films, such as porosity, thickness, roughness, and density, in the desired way by controlling the fabrication conditions including pH, salt concentration, or the number of bilayers[23] Based on this unique advantages, there have been many attempts to incorporate polymeric nano particles or micelles into multilayer films fabricated by LbL assembly for hydrophobic drug delivery systems. Preceding research has covered site-selective LbL assembly[25,26] but it is hardly applicable for dental, clinical, or biomedical purposes generally performed on the chair-side by doctors, not in a laboratory
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