Page 355 - IJB-9-6

International Journal of Bioprinting Surface modification of PCL scaffolds

total of 36 male Sprague-Dawley rats (6-week-old, weighed for our scaffold. Therefore, we selected a scaffold geometry
200 ± 10 g) were used in this study. To induce anesthesia, with a 90° fiber architecture and a pore size of 300 μm for
1% pentobarbital (30 mg/kg) was administered to the rats. our research. Besides, the geometry of the scaffolds used
A midline sagittal incision was made to expose the skull, for both in vitro and in vivo experiments was the same
followed by the creation of a defect with 5 mm diameter in this study. The scaffolds exhibited a highly organized
on both sides of the parietal bones using a circular drill. architecture composed of well-aligned fibers with an
Circular scaffolds measuring 1 mm in height and 5 mm average strand spacing of 300 ± 25 μm and an average
in diameter were then inserted into the prepared defects. fiber diameter of 30 ± 0.6 μm, with a porosity of 91.3%
Finally, the incisions were closed, and the rats were allowed (Figure 1A and B). In order to simplify the discussion,
to recover in their cages. The Calcein-Alizarin red staining the pure PCL scaffolds and the PCL scaffolds treated with
was performed to detect the newly formed bone. alkaline modification were respectively referred to as PCL
and M-PCL scaffolds. The impact of alkaline treatment
2.12.1. Micro-computed tomography (micro-CT) on the surface morphology of PCL was analyzed through
After 1 and 3 months of implantation, the rats were SEM. Results showed that the surface of M-PCL scaffolds
anesthetized and sacrificed. The samples were harvested exhibited nanopits and nanogrooves, in contrast to the
and fixed with 4% paraformaldehyde. After that, the smooth surface of the PCL scaffolds. The average size of
morphology analysis was detected using micro-CT. the nanopits was 200.87 ± 10.67 nm, while the lengths of
The bone volume to tissue volume (BV/TV), trabecular the nanogrooves varied from a few hundred nanometers to
thickness (Tb.Th), and trabecular separation (Tb.Sp) were microns (Figure 1C).
calculated to assess new bone formation.
The study evaluated surface roughness and wettability
2.12.2. Histological observation using AFM and automatic water contact angle. The results
The samples underwent decalcification with EDTA for a showed that alkaline treatment resulted in a significant
period of 6 weeks. Following this, they were dehydrated increase in the mean roughness average (Ra), which was
using 30% sucrose overnight. Ultimately, the samples confirmed through quantitative analysis (Figure 1D and
were embedded in optimal cutting temperature (OCT) E). Similarly, the surface wettability of PCL scaffolds was
compound and sliced into 5-μm frozen sections. significantly enhanced through alkaline treatment, as
Mineralized bone formation was evaluated by hematoxylin evidenced by a decrease in water contact angles from 124 ±
and eosin (H&E) staining, Masson’s trichrome staining, 0.5° for untreated PCL scaffolds to 43.45 ± 0.3° for M-PCL
and immunochemical staining. For undecalcified bone, the scaffolds (Figure 1F and G).
samples were embedded in methylmethacrylate and sliced
into 10-μm sections. After that, Alizarin Red S (red) and Crystalline structures and chemical information were
calcein (green) staining were photographed using confocal analyzed using XRD, FTIR, and EDS techniques. The XRD
microscopy. Finally, the undecalcified slices were stained results showed two characteristic peaks of PCL at 21.4°
van Gieson’s picrofuchsin. and 23.8°, respectively. The M-PCL exhibited a similar

2.13. Statistical analysis pattern (Figure 1H). The FTIR analysis of PCL showed
-1
All data were expressed as mean ± standard deviation. peaks at 2946, 2865, and 1720 cm , which correspond to
The comparison between the groups was performed by asymmetric CH , symmetric CH , and C=O stretching. The
2
2
one-way ANOVA or t-test. A P < 0.05 was considered presence of hydroxyl bonded to the end of PCL chain and
statistically significant. hydrolysis of PCL after alkaline treatment was indicated by
the observation of O-H stretching band at ≈ 1600 cm in
-1
3. Results M-PCL (Figure 1I). Next, EDS was conducted to evaluate
the elements on the scaffold. It was found that the surface
3.1. Physical properties of scaffolds of PCL and M-PCL was predominated by carbon (C) and
This study employed MEW to create 3D polymeric (PCL) oxygen (O) elements. However, the O/C ratio of PCL and
scaffolds for bone regeneration. Previous studies have found M-PCL was 32.5% and 36.4%, respectively (Figure 1J
that the alignment of fibers and pore size had significant and K). The rise in oxygen content following alkaline
impact on the differentiation of BMSCs. A scaffold with a treatment suggests that M-PCL scaffolds have oxygen-
90° fiber architecture and a pore size of at least 300 μm has containing functional groups, which is in line with the
been found to be more effective for osteointegration [43,44] . findings from the FTIR analysis.
However, it is important to note that increasing the pore
size can lead to a decrease in the mechanical strength Next, a uniaxial tensile test was conducted to assess the
of the scaffold. To balance both osteointegration and impact of NaOH treatment on the mechanical properties
mechanical strength, we chose a strand spacing of 300 μm of PCL scaffold. The results revealed that both scaffolds

Volume 9 Issue 6 (2023) 347 https://doi.org/10.36922/ijb.1071