Hierarchical viscosity of aqueous solution of tilapia scale collagen investigated via dielectric spectroscopy between 500 MHz and 2.5 THz

LL37 and collagen-binding domain-mediated LL37 binding with type I collagen: Quantification via QCM-D

Antimicrobial peptide (AMP)-loaded biomaterials may represent a viable alternative for stimulating wound healing while protecting against infections. Previously, to develop an efficient delivery system for the cathelicidin antimicrobial peptide, LL37, our lab modified LL37 with a collagen-binding domain derived from collagenase (cCBD) as an anchoring unit to collagen-based wound dressings. However, a direct quantification of unmodified LL37 and cCBD-LL37 binding with collagen has not been performed. In this study, we used quartz crystal microbalance with dissipation monitoring (QCM-D), immunohistochemistry (IHC), and atomic force microscopy (AFM) to establish and characterize an adsorbed layer of type I collagen on the QCM-D sensor and quantify peptide-collagen binding. A collagen deposition protocol was successfully established by measuring concentration-dependent deposition of collagen in QCM-D, and collagen self-assembly was observed by IHC and AFM. Hydrophobicity is known to affect the behavior of collagen adsorption. Therefore, we compared the deposition of collagen on hydrophilic SiO₂-coated sensors vs. hydrophobic polystyrene (PS)-coated sensors via QCM-D, and found that the hydrophobic surface yielded more collagen adsorption, which suggested that hydrophobic surfaces are preferable for collagen layer establishment. There was no significant difference between LL37 and cCBD-LL37 binding with collagen, but the cCBD-LL37 showed better retention on the collagen after washing with PBS, indicating that there is an advantage to using cCBD as an anchoring unit to collagen. Collectively, these results provide important information on cCBD-mediated AMP-binding mechanisms and establish an effective method for quantifying peptide-collagen binding.

Diffusions in Aqueous Solutions with Multivalent Cations and Especially in Cationic First Hydration Shell

Compared with univalent cationic diffusion, little is known about the diffusion behavior of multivalent cations let alone the diffusion of water in their first hydration shell. Here, we show that all published translational diffusion coefficients of multivalent cations and water measured at room temperature exhibit the same concentration dependence when plotted as a function of the mass fraction of free water or of hydrated solute. This behavior is held until only hydration and confined water remain in solutions, wherein their concentration dependences become cationic charge number-dependent. We also found that the iceberg model can well describe the diffusions of multivalent cations with decreasing water content until only hydration water is present. However, ¹H-pulsed-field-gradient nuclear magnetic resonance measurements confirmed that ¹H in the first hydration shell diffuses faster than Al³⁺ at room temperature and they have the same diffusion coefficient only with decreasing the temperature down to about 243 K. Therefore, iceberg model only equivalently describes the effect of strong ion-water interaction on multivalent cationic diffusion. These results will also help us reconceive our current understanding of the pathway for hydration water affecting the diffusion behavior of solutes with relatively weak solute-water interactions.

Collagen Scaffolds in Cartilage Tissue Engineering and Relevant Approaches for Future Development

BACKGROUND

Cartilage tissue engineering (CTE) aims to obtain a structure mimicking native cartilage tissue through the combination of relevant cells, three-dimensional scaffolds, and extraneous signals. Implantation of 'matured' constructs is thus expected to provide solution for treating large injury of articular cartilage. Type I collagen is widely used as scaffolds for CTE products undergoing clinical trial, owing to its ubiquitous biocompatibility and vast clinical approval. However, the long-term performance of pure type I collagen scaffolds would suffer from its limited chondrogenic capacity and inferior mechanical properties. This paper aims to provide insights necessary for advancing type I collagen scaffolds in the CTE applications.

METHODS

Initially, the interactions of type I/II collagen with CTE-relevant cells [i.e., articular chondrocytes (ACs) and mesenchymal stem cells (MSCs)] are discussed. Next, the physical features and chemical composition of the scaffolds crucial to support chondrogenic activities of AC and MSC are highlighted. Attempts to optimize the collagen scaffolds by blending with natural/synthetic polymers are described. Hybrid strategy in which collagen and structural polymers are combined in non-blending manner is detailed.

RESULTS

Type I collagen is sufficient to support cellular activities of ACs and MSCs; however it shows limited chondrogenic performance than type II collagen. Nonetheless, type I collagen is the clinically feasible option since type II collagen shows arthritogenic potency. Physical features of scaffolds such as internal structure, pore size, stiffness, etc. are shown to be crucial in influencing the differentiation fate and secreting extracellular matrixes from ACs and MSCs. Collagen can be blended with native or synthetic polymer to improve the mechanical and bioactivities of final composites. However, the versatility of blending strategy is limited due to denaturation of type I collagen at harsh processing condition. Hybrid strategy is successful in maximizing bioactivity of collagen scaffolds and mechanical robustness of structural polymer.

CONCLUSION

Considering the previous improvements of physical and compositional properties of collagen scaffolds and recent manufacturing developments of structural polymer, it is concluded that hybrid strategy is a promising approach to advance further collagen-based scaffolds in CTE.