Surface modification of 3D-printed PLA structures is a major issue in terms of increasing the biofunctionality and expanding the tissue engineering applications of these parts. In this paper, different exposure times were used for low-pressure oxygen plasma applied to PLA 3D-printed scaffolds. Alkali surface treatments were also evaluated, aiming to compare the modifications introduced on the surface properties by each strategy. Surface-treated samples were characterized through the quantification of carboxyl groups, energy-dispersive X-ray spectroscopy, water contact angle measurements, and differential scanning calorimetry analysis. The change in the surface properties was studied over a two-week period. In addition, an enzymatic degradation analysis was carried out to evaluate the effect of the surface treatments on the degradation profile of the 3D structures. The physicochemical characterization results suggest different mechanism pathways for each type of treatment. Alkali-treated scaffolds showed a higher concentration of carboxyl groups on their surface, which enhanced the enzymatic degradation rate, but were also proven to be more aggressive towards 3D-printed structures. In contrast, the application of the plasma treatments led to an increased hydrophilicity of the PLA surface without affecting the bulk properties. However, the changes on the properties were less steady over time.

Polycaprolactone–carboxymethyl cellulose composites have been obtained and used to print porous structures by material extrusion. The materials used contained 0, 2 and 5% w/w of the carboxymethyl cellulose additive. These structures have been analyzed in terms of their morphology (including the evaluation of their porosity), mechanical properties under compression load and cell affinity. Cell affinity has been evaluated by culturing sheep mesenchymal stem cells and analyzing their viability by the Alamar Blue^® assay at days 1, 3, 6 and 8. The results show that composites samples have similar values of porosity and apparent density than pure polycaprolactone ones. However, samples containing 5% w/w of carboxymethyl cellulose have micropores on the filaments due to a hindered deposition process. This characteristic affects the mechanical properties of the structures, so these ones have a mean compression modulus significantly lower than pure polycaprolactone scaffolds. However, the samples containing 2% w/w of carboxymethyl cellulose show no significant difference with the pure polycaprolactone ones in terms of their mechanical properties. Moreover, the presence of 2% w/w of additive improves cell proliferation on the surface of the porous structures. As complementary information, the flow properties of the composite materials were studied and the power law equations at 210 °C obtained, as this temperature was the 3D printing temperature. These equations can be useful for simulation and designing purposes of other manufacturing processes.