On the Effectiveness of Oxygen Plasma and Alkali Surface Treatments to Modify the Properties of Polylactic Acid Scaffolds

Abstract

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.

The Effect of Argon Plasma Surface Treatment on Poly(lactic-co-glycolic acid)/Collagen-Based Biomaterials for Bone Tissue Engineering

“…Our study demonstrated that the water and diiodomethane contact angles on PLGA films were significantly reduced after the plasma treatment. These results are consistent with previously reported studies on an oxygen plasma treatment of poly(lactic acid) (PLA) scaffolds [ 42 , 55 ] and PLGA films [ 56 ]. The wettability of PLGA-based biomaterials has been reported to be a function of the lactide/glycolide ratio, and the wettability can be enhanced after plasma treatments [ 56 ].…”

“…It has been generally accepted that plasma surface modifications can improve the surface wettability [ 42 , 43 , 44 , 45 ] and cellular attachment [ 15 , 16 , 46 , 47 , 48 , 49 , 50 ] of polymeric scaffolds. A plasma surface treatment can be advantageous in supporting cell adhesion due to the added functionality on the cell–biomaterial interface in their early regeneration phase [ 46 ].…”

Strategies To Modify the Surface and Bulk Properties of 3D-Printed Solid Scaffolds for Tissue Engineering Applications

“…Subsequent treatment with citric acid improved surface hydrophilicity and introduced porosity . In another comparison between oxygen plasma-treated and wet chemical-treated 3D scaffolds of PLA, it was found that chemical etching generates a higher number of surface functional groups (carboxylic acid) and higher porosity than the plasma-treated scaffolds . The etching parameters can be easily varied by changing the temperature, type, and concentration of the alkali/acid, etc.…”

“…Because these methods only affect the surface’s physical state and do not alter the bulk scaffold’s chemical composition, they are highly translatable across various types of scaffolds . The topographical modifications of several hard polymeric scaffolds such as PLA, PLGA, PCL, and polystyrene have been reported . These modifications are largely restricted to a few microns or nanometers from the scaffold surface.…”

“…These modifications are largely restricted to a few microns or nanometers from the scaffold surface. For instance, treatment of PLA scaffold with oxygen plasma has been reported to introduce surface roughness at a nanometric scale . In addition, plasma treatment also generates surface hydroxyl and carboxylic acid functional groups, which increases the hydrophilicity of PLA, indicated by a reduction in the water contact angle post-treatment.…”