Hong Jung Ki, Cooke Shelley L, Whittington Abby R, Roman Maren
Macromolecules Innovation Institute, Virginia Tech, Blacksburg, VA, United States.
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, VA, United States.
Front Bioeng Biotechnol. 2021 Feb 25;9:605924. doi: 10.3389/fbioe.2021.605924. eCollection 2021.
3D-printed bone scaffolds hold great promise for the individualized treatment of critical-size bone defects. Among the resorbable polymers available for use as 3D-printable scaffold materials, poly(ε-caprolactone) (PCL) has many benefits. However, its relatively low stiffness and lack of bioactivity limit its use in load-bearing bone scaffolds. This study tests the hypothesis that surface-oxidized cellulose nanocrystals (SO-CNCs), decorated with carboxyl groups, can act as multi-functional scaffold additives that (1) improve the mechanical properties of PCL and (2) induce biomineral formation upon PCL resorption. To this end, an biomineralization study was performed to assess the ability of SO-CNCs to induce the formation of calcium phosphate minerals. In addition, PCL nanocomposites containing different amounts of SO-CNCs (1, 2, 3, 5, and 10 wt%) were prepared using melt compounding extrusion and characterized in terms of Young's modulus, ultimate tensile strength, crystallinity, thermal transitions, and water contact angle. Neither sulfuric acid-hydrolyzed CNCs (SH-CNCs) nor SO-CNCs were toxic to MC3T3 preosteoblasts during a 24 h exposure at concentrations ranging from 0.25 to 3.0 mg/mL. SO-CNCs were more effective at inducing mineral formation than SH-CNCs in simulated body fluid (1x). An SO-CNC content of 10 wt% in the PCL matrix caused a more than 2-fold increase in Young's modulus (stiffness) and a more than 60% increase in ultimate tensile strength. The matrix glass transition and melting temperatures were not affected by the SO-CNCs but the crystallization temperature increased by about 5.5°C upon addition of 10 wt% SO-CNCs, the matrix crystallinity decreased from about 43 to about 40%, and the water contact angle decreased from 87 to 82.6°. The abilities of SO-CNCs to induce calcium phosphate mineral formation and increase the Young's modulus of PCL render them attractive for applications as multi-functional nanoscale additives in PCL-based bone scaffolds.
3D打印骨支架在临界尺寸骨缺损的个体化治疗方面具有巨大潜力。在可用作3D可打印支架材料的可吸收聚合物中，聚（ε-己内酯）（PCL）有诸多优点。然而，其相对较低的刚度和缺乏生物活性限制了它在承重骨支架中的应用。本研究验证了以下假设：表面氧化的纤维素纳米晶体（SO-CNCs），带有羧基修饰，可作为多功能支架添加剂，（1）改善PCL的机械性能，（2）在PCL吸收时诱导生物矿化形成。为此，进行了一项生物矿化研究，以评估SO-CNCs诱导磷酸钙矿物质形成的能力。此外，使用熔融共混挤出法制备了含有不同量SO-CNCs（1、2、3、5和10 wt%）的PCL纳米复合材料，并对其杨氏模量、极限拉伸强度、结晶度、热转变和水接触角进行了表征。在浓度范围为0.25至3.0 mg/mL下暴露24小时期间，硫酸水解的CNCs（SH-CNCs）和SO-CNCs对MC3T3前成骨细胞均无毒性。在模拟体液（1x）中，SO-CNCs在诱导矿物质形成方面比SH-CNCs更有效。PCL基质中10 wt%的SO-CNC含量使杨氏模量（刚度）增加了2倍多，极限拉伸强度增加了60%以上。基质玻璃化转变温度和熔点不受SO-CNCs影响，但添加10 wt% SO-CNCs后结晶温度升高约5.5°C，基质结晶度从约43%降至约40%，水接触角从87°降至82.6°。SO-CNCs诱导磷酸钙矿物质形成和增加PCL杨氏模量的能力使其成为基于PCL的骨支架中多功能纳米级添加剂应用的有吸引力的选择。
