Degradation of Melt Electrowritten PCL Scaffolds Following Melt Processing and Plasma Surface Treatment

Abstract

Melt electrowriting (MEW) has been widely used to process polycaprolactone (PCL) into highly ordered microfiber scaffolds with controllable architecture and geometry. However, the integrity of PCL during specific processes involved in routine MEW scaffold development has not yet been thoroughly investigated. This study investigates the impact of MEW processing on PCL following exposure to high temperatures required for melt extrusion as well as atmospheric plasma, a widely used surface treatment for improving MEW scaffold hydrophilicity. The change in polymer molecular weight and melt temperature is characterized, in comparing unprocessed and processed samples, in addition to analysis of the mechanical and surface properties of the scaffolds. No significant difference in the molecular weight or mechanical properties of the PCL scaffolds is evident following 5 days of cyclic heating to 90 °C. Exposure to plasma for up to 5 min significantly increased hydrophilicity and surface adhesion force, characterized via contact angle and atomic force microscope, however, significant polymer degradation occurred evidenced by increased brittleness of the scaffolds. This study demonstrates the degradation of PCL following fabrication via MEW and surface treatment to guide the optimization of scaffold development for subsequent applications in tissue engineering and biofabrication.

Measuring contact angles on hydrophilic porous scaffolds by implementing a novel raised platform approach: A technical note

“…As CA remains one of the most popular and accessible method for characterizing hydrophilicity of biomaterials, accurate measurements are vital to providing insight into the interactions between scaffolds and other media, including for assessing suitability for successful cell seeding and cell attachment 19–21 . False‐positive CA measurements may lead to over‐application of surface treatments, such as NaOH etching time or concentration, 22 or plasma exposure time or energy, which are known to contribute to accelerated aging, degradation or other uncontrolled damage to the scaffolds and may limit their performance 13 …”

“…Several porous polymer scaffolds manufactured via various molding and 3D printing methods were used as representative samples of typical polymeric porous biomaterials. High porosity melt electrowritten scaffolds were fabricated using a custom‐built MEW device, described previously 12,13 . Polycaprolactone (PCL) PC12 (Purac, Corbion) was loaded into a 3 mL syringe (Nordson EFD) and fitted with a 21 G blunt‐tip needle (Nordson EFD).…”

“…High porosity melt electrowritten scaffolds were fabricated using a custom-built MEW device, described previously. 12,13 Polycaprolactone (PCL) PC12 (Purac, Corbion) was loaded into a 3 mL syringe (Nordson EFD) and fitted with a 21 G blunt-tip needle (Nordson EFD). The syringe was then loaded in a grounded custom heater jacket with a heating supply and regulated air pressure.…”

“…Distilled H 2 O was dispensed to create a droplet of 50 μL onto dry samples placed in various configurations on a motorized z-stage. CA measurements were performed on nontreated scaffolds on the measurement stage substrate (anodised aluminum), followed by measurement of plasma treated samples (with known hydrophilicity 7,13 ) on the measurement substrate and raised on the 3D printed platform. Next, the CA of various measurement substrates were measured, including the native measurement stage in the Drop Shape Analyzer (anodised aluminum), a coated glass microscope slide (ÜberFrost ® Printer Slides, InstrumeC), a metal plate (stainless steel) and a petri dish (polystyrene).…”

“…[19][20][21] False-positive CA measurements may lead to over-application of surface treatments, such as NaOH etching time or concentration, 22 or plasma exposure time or energy, which are known to contribute to accelerated aging, degradation or other uncontrolled damage to the scaffolds and may limit their performance. 13 This study does not address the challenge in measuring on rough or uneven surfaces, which are an intrinsic consequence of including porosity in a scaffold design. It was observed in this study that the alignment of the deposited droplet between or on top of scaffold microstructures, particularly repeating linear fibers prevalent in MEW scaffolds (Figure 4A), strongly influenced the likelihood of a droplet remaining on the top of the scaffold surface or being absorbed into the structure.…”