A comprehensive study of acid and base treatment of 3D printed poly(ε-caprolactone) scaffolds to tailor surface characteristics

Poly(ε-caprolactone) (PCL) chain cleavage results in the formation of polar terminal species, comprising hydroxy and carboxyl groups that enhance surface hydrophilicity and enable subsequent biofunctionalization. However, the direct effects of various acidic and basic treatments on 3D printed PCL scaffolds have not been studied from a functional perspective. In this study, we comprehensively assessed the influence of acid (hydrochloric, HCl) and base (sodium hydroxide, NaOH) catalyzed hydrolysis across different conditions on various properties of 3D printed PCL scaffolds. Analyses included testing of physiochemical and mechanical properties, and assessment of rate and stability of surface-nucleating bioactive apatite-like minerals. HCl exposure resulted in pronounced bulk degradation, as observed through limited increase in surface charge, pronounced mechanical weakening, and clear decrease in molecular weight. Conversely, NaOH treatment resulted in a more superficial degradation, with a dramatic increase in surface charge, much lower mechanical degradation, and little change in molecular weight. Indeed, the characteristics observed under acidic catalysis appeared more representative of physiological degradation. The apatite-like coating on the base-treated surface was found to be superior. Our results demonstrate the range of surface and bulk properties achievable through these accessible treatments, and support such techniques for the functionalization of PCL scaffolds for biomedical applications.