Polypropylene (PP) powder bed fusion (PBF) with subsequent mechanical postprocessing can enable the development of more efficient and effective surfaces for bioprocessing equipment. However, there is still a lack of knowledge regarding the most relevant surface differences when compared to standardized surfaces. Herein, we present a new systematic methodology, including the evaluation of relevant roughness parameters and surface wettability, which has been implemented to assess the potential of AM to produce biopharmaceutical components. Surfaces of PP components produced by PBF and mechanically postprocessed by tumble surface finishing at 5, 10 and 15 h were compared to reference surfaces produced by computer numerical control (CNC) milling manufacturing. Thirteen roughness parameters were found to be relevant, of which the arithmetic mean peak curvature (Spc) and the density of peaks (Spd) were the most significant. The results demonstrate that the reference surfaces had Spc and Spd values of 1029 ± 36 mm−1 and 67739 ± 5440 mm−2, respectively, and moderate wettability with advancing (ACA) and receding (RCA) contact angles of 89 ± 3° and 68 ± 2°, respectively. The as-printed PBF surfaces were hydrophobic, with ACA of 119 ± 2° and RCA of 107 ± 4°, and with Spc and Spd values of 1089 ± 110 mm−1 and 30078 ± 4325 mm−2, respectively. PBF surfaces switched to a hydrophilic surface of 67 ± 3° and 44 ± 4° when the tumble surface finishing time was increased to 15 h. By taking advantage of this knowledge, we could produce surfaces using PBF and 5 h of mechanical postprocessing, which mimicked surface wetting and had Spc of 1100 ± 68 mm−1 and Spd of 55702 ± 9477 mm−2, similar to that of the CNC milling manufacturing. The developed comparative method and the results are important to better understand AM surfaces and can be used to transfer manufacturing from subtractive to additive technologies.

Fused filament fabrication (FFF) is a commonly used method for producing three-dimensional scaffolds using synthetic, degradable polymers. However, there are several variables that must be considered when fabricating devices for clinical use, one of which is storage conditions after printing. While the academic community has examined the impact of FFF on mechanical and thermal properties, there has been less focus on how storage conditions would affect the surface texture of scaffolds. Our hypothesis was that the surface, thermal and physical properties of FFF scaffolds are significantly influenced by the storage conditions. We evaluated the surfaces of FFF poly (ε-caprolactone) (PCL) and poly (ε-caprolactone-co-p-dioxanone) (PCLDX) strands that were stored at 4 °C, 20 °C, and 37 °C for 28 days. We monitored surface texture, physical and thermal changes to understand the effect of storage on the strands. The implementation of scale-sensitive fractal analysis and feature parameters revealed that storage conditions at 37 °C increased the number of hills and dales, as well as the density of peaks and pits compared to 20 °C and 4 °C, for both materials. The feature roughness parameters for PCL had up to 90% higher values than those of PCLDX, which correlated with the physical and thermal properties of the materials. These differences may impact further surface-cell interaction, highlighting the need for further evaluation for faster clinical translation. Our findings emphasize the importance of considering storage conditions in the design and manufacture of FFF scaffolds and suggest that the use of feature roughness parameters could facilitate the optimization and tailoring the surface properties for specific applications.

The fast-progressing landscape of the bioprocessing industry emphasizes innovation and efficiency enhancement, propelled by the integration of advanced solutions. Additive manufacturing technologies, particularly laserbased powder bed fusion with polypropylene, are pivotal in this industrial metamorphosis. However, despite the substantial scientific effort in the field, a significant gap exists in comprehending the surface characteristics of new surfaces and their implications for bacterial attachment and biofilm formation. This arises, in part, due to the absence of comprehensive and universally applicable topographical characterization analysis specifically designed for additively manufactured-fabricated surfaces. Typically, researchers tend to rely on the commonly used roughness parameter, Sa, that primarily quantifies the average height variation across a surface. Addressing this limitation is crucial for understanding the connection between surface characteristics and bacterial attachment dynamics. Here, we propose an innovative approach using surface analysis including confocal microscopy, advanced roughness measurements, and multivariate statistical analysis to uncover the connections between bacterial attachment for Gram negative Escherichia coli and Gram positive Staphylococcus aureus in early biofilm formation with surfaces produced by standardized and additively manufactured techniques. Finally, we advocate for the adoption of a set of roughness parameters that specifically describe the dale region of the surfaces. By doing so, we intend to establish direct links between surface texture and bacterial adhesion, thus contributing significantly to the advancement of both bioprocessing and additive manufacturing research domains.