Lithium Chloride-Releasing 3D Printed Scaffold for Enhanced Cartilage Regeneration

Abstract

BACKGROUND We synthetized a 3D printed poly-ε-caprolactone (PCL) scaffold with polydopamine (PDA) coating and lithium chloride (LiCl) deposition for cartilage tissue engineering and analyzed its effect on promoting rabbit bone marrow mesenchymal stem cells (rBMSC) chondrogenesis in vitro. MATERIAL AND METHODS PCL scaffolds were prepared by 3D printing with a well-designed CAD digital model, then modified by PDA coating to produce PCL-PDA scaffolds. Finally, LiCl was deposited on the PDA coating to produce PCL-PDA-Li scaffolds. The physicochemical properties, bioactivity, and biocompatibility of PCL-PDA-Li scaffolds were accessed by comparing them with PCL scaffolds and PCL-PDA scaffolds. RESULTS 3D PCL scaffolds exhibited excellent mechanical integrity as designed. PDA coating and LiCl deposition improved surface hydrophilicity without sacrificing mechanical strength. Li⁺ release was durable and ion concentration did not reach the cytotoxicity level. This in vitro study showed that, compared to PCL scaffolds, PCL-PDA and PCL-PDA-Li scaffolds significantly increased glycosaminoglycan (GAG) formation and chondrogenic marker gene expression, while PCL-PDA-Li scaffolds showed far higher rBMSC viability and chondrogenesis. CONCLUSIONS 3D printed PCL-PDA-Li scaffolds promoted chondrogenesis in vitro and may provide a good method for lithium administration and be a potential candidate for cartilage tissue engineering.

Figure 1

The morphology and surface microstructure of 3D-printed scaffolds. The lower and higher magnification of digital photographs of PCL (A, B), PCL-PDA (C, D), and PCL-PDA-Li scaffolds (E, F). The corresponding SEM images of PCL (G, H), PCL-PDA (I, J), and PCL-PDA-Li (K, L) scaffolds.

Figure 2

Characterizations of scaffolds. (A) Static water-contacting angles. (B) Compressive strength. (C) The degradation behavior of PCL, PCL-PDA, and PCL-PDA-Li scaffolds. (D) The average rates of Li⁺ release at each time point from the PCL-PDA-Li scaffolds (* p<0.05).

Figure 3

SEM micrograph of rBMSCs cultured on the PCL (A), PCL-PDA (B), and PCL-PDA-Li (C) scaffolds for 7 days. Live and dead staining of rBMSCs cultured on the PCL (D–F), PCL-PDA (G–I), and PCL-PDA-Li (J–L) scaffolds for 14 days. (M) Total cell number attached on the scaffolds. (N) Quantification of live and dead cells on the scaffolds. (* p<0.05, ** p<0.01)

Figure 4

(A) Biocompatibility analysis of the scaffolds by MTT. DNA (B) and GAG (C) production and GAG/DNA (D) by rBMSCs cultured on scaffolds (* p<0.05). (E–I) The gene expression of rBMSCs cultured on the PCL, PCL-PDA, and PCL-PDA-Li scaffolds at 7 and 14 days. All data were normalized to the corresponding GAPDH value (* p<0.05).