Data for accelerated degradation of calcium phosphate surface-coated polycaprolactone and polycaprolactone/bioactive glass composite scaffolds

Polycaprolactone (PCL)-based composite scaffolds containing 50 wt% of 45S5 bioactive glass (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated into scaffolds using melt-extrusion based additive manufacturing technique. Additionally, the PCL scaffolds were surface coated with a layer of calcium phosphate (CaP). For a comparison of the scaffold degradation, the scaffolds were then subjected to in vitro accelerated degradation by immersion in 5 M sodium hydroxide (NaOH) solution for up to 7 days. The scaffold׳s morphology was observed by means of SEM imaging and scaffold mass loss was recorded over the experimental period.


a b s t r a c t
Polycaprolactone (PCL)-based composite scaffolds containing 50 wt% of 45S5 bioactive glass (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated into scaffolds using melt-extrusion based additive manufacturing technique. Additionally, the PCL scaffolds were surface coated with a layer of calcium phosphate (CaP). For a comparison of the scaffold degradation, the scaffolds were then subjected to in vitro accelerated degradation by immersion in 5 M sodium hydroxide (NaOH) solution for up to 7 days. The scaffold's morphology was observed by means of SEM imaging and scaffold mass loss was recorded over the experimental period. &

Data accessibility Data in article
Value of the data The data can be used as a benchmark to study and compare the degradation behaviors of new polymers and polymeric scaffolds.
By directly comparing the stability of both bioactive glass and calcium phosphate, our approach provides new insights into the stability of surface coating vs embedded particles.
The data shows a direct comparison of the degradation behavior of PCL, PCL-CaP coated, PCL/50-45S5 and PCL/50-SrBG scaffolds under an accelerated rate.

Data
The in vitro degradation of PCL, PCL/CaP, PCL/50-45S5 and PCL/50-SrBG composite were evaluated using an in vitro accelerated degradation test as previously reported by Lam et al. [1]. Over 7 days of immersion in 5 M NaOH, PCL and PCL/CaP scaffolds lost 24.671.6% and 24.272.4% of their original mass respectively (Fig. 1u). Through SEM observation of the surfaces of scaffolds' struts over time, it was revealed that both PCL and PCL/CaP scaffold surfaces were roughened and that an increasing numbers of pits were observed on the surfaces (Fig. 1). After 6 h immersion in 5 M NaOH, it was observed that the CaP coating on PCL/CaP scaffolds detached from the scaffold surfaces, and it was completely absent from the scaffold surfaces after 3 days (Fig. 1). On the other hand, with only 6 h immersion in 5 M NaOH, PCL/50-45S5 lost 15.571.9% of its original mass and PCL/50-SrBG lost 39.8473.56% of its original mass (Fig. 1u). After 24 h immersion, both PCL/50-45S5 and PCL/50-SrBG scaffolds had disintegrated into pieces and were not retrievable for further analysis. Although the struts of PCL/50-45S5 and PCL/50-SrBG scaffolds appeared intact after 6 hours immersion in 5 M NaOH (Fig. 1q and s), inspection by SEM of the scaffold surfaces showed numerous large pits, which was due to dislodging of the BG particles from the PCL microfilaments ( Fig. 1r and t). The surfaces were also much rougher compared to PCL and PCL/CaP scaffolds immersed in 5 M NaOH for the same period of time.  [2], respectively, were incorporated into the PCL (CAPA 6500, Perstorp, United Kingdom) bulk by fast precipitation into excess ethanol [3]. Detailed description of the composite synthesizing procedures can be found in Poh et al. [4].

Composite material synthesis and scaffold fabrication
Once the composite materials were air-dried with a constant weight over 3 consecutive days, scaffolds (PCL, PCL/50-45S5, and PCL/50-SrBG) were fabricated by mean of additive manufacturing technology at 90°C. All scaffolds with the dimension of 50 (L) Â 50 (W) Â 2.4 (H) mm 3 were fabricated using a 21 G nozzle, with a lay-down pattern of 0-90°, filament gap of 2 mm and layer thickness of 0.4 mm.

Calcium phosphate coating on PCL scaffolds
By adapting a method described by Vaquette et al. [5], PCL scaffolds were coated with CaP. Briefly, PCL scaffolds were immersed in 70% ethanol under vacuum for 10 min to remove entrapped air bubbles. Then, scaffolds were placed in pre-warmed 5 M NaOH solution (37°C) under vacuum for 10 minutes followed by incubation at 37°C for 60 min using a water bath. The scaffolds were rinsed with MilliQ water until the pH of the rinsing water was $ pH 7. Then, the scaffolds were immersed in filtered 10 Â simulated body fluid (SBF) adjusted to pH 6 with sodium bicarbonate (NaHCO 3 ) (initially described by Kokubo et al. [6]) at 37°C for 60 min with one change of fresh filtered 10 Â SBF solution after 30 min. Then, the scaffolds were rinsed twice with MilliQ water, and immersed in 0.5 M NaOH at 37°C for 30 min to homogenize the coated CaP phase. Finally, the scaffolds were rinsed with MilliQ water until the rinsing solution reached $ pH 7.

Accelerated degradation of scaffolds in 5 M NaOH
Scaffolds of 50 (L) Â 50 (W) Â 2.4 (H) mm 3 were cut into 4 Â 4 Â 2.4 mm 3 and immersed in 5 M NaOH (Sigma-Aldrich) and maintained at 37°C for 6 h, 1 day, 3, 4, 5, 6, and 7 days to recapitulate the initial degradation of PCL in vitro, but at an accelerated rate as described by Lam et al. [1]. The initial and final mass (dried under vacuum for 48 h) of each scaffold was measured using an electronic balance with 0.1 mg sensitivity and the percentage of mass loss was calculated. Scaffold morphology was examined using SEM operating at 10 kV after gold sputter-coating.