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International Journal of Bioprinting Sr-doped printed scaffolds for bone repair

Ltd. (China). Sprague-Dawley (SD) rats were provided by At room temperature, the 3D-printed SrBG/PCL scaffolds
Chongqing Teng Xin Hua Fu Laboratory Animal Sales Co, were soaked in the weakly basic dopamine solution and
Ltd. (China) (animal qualification certificate no. SYXK shaken at 30°C on a shaking bed for 6 h. The SrBG/PCL
[Qian] 2021-0003). scaffolds were then washed with deionized water to remove
unattached polydopamine and dried to obtain the PDA/
2.2. Preparation of PCL, SrBG/PCL, and SrBG/PCL scaffolds (referred to as the PSBP group).
PDA/SrBG/PCL scaffolds
2.2.1. Preparation of SrBG 2.3. Scaffold characterization
The molar ratio of the components of SrBG was designed 2.3.1. Morphology of SrBG
as 60 SiO :30 CaO:6 SrO:4 P O . The specific experimental The micromorphology of SrBG was characterized using
2
2
5
method for the preparation of micro- and nano-SrBG a field emission scanning electron microscope (SEM)
microspheres using the sol–gel method is described below. (Merlin, Germany); the particle size distribution of
The experimental temperature was maintained at 40°C SrBG was analyzed using dynamic light scattering (DLS)
using a water bath, and 5 g of DDA was fully dissolved in (Malvern Panalytical, England).
a mixture of deionized water and anhydrous ethanol. After
that, 16.5 mL of TEOS and TEP was sequentially added to 2.3.2. Surface morphology of the scaffolds
the solution using a syringe pump at a speed of 0.5 mL/min. The surface morphology and structure of the P, SBP,
CN and strontium nitrate were then added slowly, and the and PSBP scaffolds were observed using SEM (Merlin,
solution was stirred continuously for 3 h. Thereafter, the Germany) at an accelerating voltage of 10 kV after gold-
solution was kept at room temperature for 24 h to obtain a spraying the surface of the scaffolds. The average pore area
glass sol, which was subsequently washed and centrifuged of the scaffold fiber surface was statistically analyzed using
to obtain a white precipitate. The precipitate was pre-frozen ImageJ software.
in the refrigerator at –20°C for 2 h and then freeze-dried.
Finally, the freeze-dried precipitate was heated in a muffle 2.3.3. Hydrophilicity of the scaffolds
furnace at 650°C for 3 h to obtain the SrBG, which was The scaffolds were placed on a contact angle tester
dried and stored after ball milling and sieving. (c, KRUSS, Germany), and a 2-μL droplet was placed on
the surface of the scaffolds. The position of the sample in
2.2.2. Preparation of SrBG/PCL scaffolds contact with the droplet was adjusted to align with the
Approximately 100 mg of SrBG powder was dispersed in baseline of the measurement; photographs were taken to
10 mL of dichloromethane solution containing 1 g PCL. obtain a still image of the droplet, and the magnitude of
After stirring, the solution was poured into glass dishes, the contact angle (θ ) was calculated using contact angle
and the dichloromethane was fully evaporated to obtain measurement software DSA25 for each scaffold group.
the scaffold raw material SrBG/PCL. The SrBG/PCL was
transferred to the 3D printer (EFL-BP-6603, Suzhou 2.3.4. Porosity of the scaffolds
Institute of Intelligent Manufacturing, China), and the The mass of the dried scaffold sample (M0), the total
printing parameters were set as: diameter: 5 mm, number mass of the specific gravity bottle containing anhydrous
of layers: 5 layers, layer thickness: 0.2 mm, infill density: ethanol at room temperature (M1), the total mass of the
75%, barrel temperature: 65°C, and nozzle temperature: bottle and sample after sonication for 10 min to remove air
70°C. The SrBG/PCL was heated, melted, and subsequently bubbles (M2), and the remaining mass after the sample was
printed into cylindrical 3D scaffolds (diameter: 5 mm; removed (M3) were measured accordingly. The porosity of
height: 1 mm), referred to as the SBP group. For
comparison, PCL was directly loaded into the 3D printer the obtained scaffolds was calculated using Equation (I):
to fabricate a cylindrical 3D scaffold, designated as group P.
M2 − M3 − M0
2.2.3. Preparation of PDA/SrBG/PCL scaffolds Porosity = M1− M3 (I)
The SrBG/PCL scaffolds were then modified using PDA.
A Tris–HCl buffer (pH 8.5) was first prepared using 1.21
g Tris-base and 100 mL deionized water, and it was then 2.3.5. Ion release profile of the scaffolds
stored at room temperature until further use. Thereafter, Each scaffold (approximately 20 mg) was immersed in
approximately 0.25 g dopamine hydrochloride (2.5 g/L) 5 mL phosphate-buffered saline (PBS) and shaken at
was added to the Tris–HCl buffer and stirred. The ready- 37°C and 60 rpm. Samples were collected on days 1 and
+
to-use solution was stored in the dark until further use. 3, and the concentration of Sr² was measured using the

Volume 11 Issue 4 (2025) 353 doi: 10.36922/IJB025210211