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Title: [Effects of three-dimensional bioprinting antibacterial hydrogel on full-thickness skin defect wounds in rats].
Author: Jin RH, Zhang ZZ, Xu PQ, Xia SZ, Weng TT, Zhu ZK, Wang XG, You CG, Han CM.
Journal: Zhonghua Shao Shang Yu Chuang Mian Xiu Fu Za Zhi; 2023 Feb 20; 39(2):165-174. PubMed ID: 36878526.
Abstract:
Objective: To explore the effects of three-dimensional (3D) bioprinting gelatin methacrylamide (GelMA) hydrogel loaded with nano silver on full-thickness skin defect wounds in rats. Methods: The experimental research method was adopted. The morphology, particle diameter, and distribution of silver nanoparticles in nano silver solution with different mass concentrations and the pore structure of silver-containing GelMA hydrogel with different final mass fractions of GelMA were observed by scanning electron microscope and the pore size was calculated. On treatment day 1, 3, 7, and 14, the concentration of nano silver released from the hydrogel containing GelMA with final mass fraction of 15% and nano silver with final mass concentration of 10 mg/L was detected by mass spectrometer. At 24 h of culture, the diameters of inhibition zone of GelMA hydrogel containing final mass concentration of 0 (no nano silver), 25, 50, and 100 mg/L nano silver against Staphylococcus aureus and Escherichia coli were detected. Fibroblasts (Fbs) and adipose stem cells (ASCs) were isolated respectively by enzymatic digestion using the discarded prepuce after circumcision from a 5-year-old healthy boy who was treated in the Department of Urology of the Second Affiliated Hospital of Zhejiang University School of Medicine in July 2020, and the discarded fat tissue after liposuction from a 23-year-old healthy woman who was treated in the Department of Plastic Surgery of the Hospital in July 2020. The Fbs were divided into blank control group (culture medium only), 2 mg/L nano sliver group, 5 mg/L nano sliver group, 10 mg/L nano sliver group, 25 mg/L nano sliver group, and 50 mg/L nano sliver group, which were added with the corresponding final mass concentrations of nano sliver solution, respectively. At 48 h of culture, the Fb proliferation viability was detected by cell counting kit 8 method. The Fbs were divided into 0 mg/L silver-containing GelMA hydrogel group, 10 mg/L silver-containing GelMA hydrogel group, 50 mg/L silver-containing GelMA hydrogel group, and 100 mg/L silver-containing GelMA hydrogel group and then were correspondingly treated. On culture day 1, 3, and 7, the Fb proliferation viability was detected as before. The ASCs were mixed into GelMA hydrogel and divided into 3D bioprinting group and non-printing group. On culture day 1, 3, and 7, the ASC proliferation viability was detected as before and cell growth was observed by live/dead cell fluorescence staining. The sample numbers in the above experiments were all 3. Four full-thickness skin defect wounds were produced on the back of 18 male Sprague-Dawley rats aged 4 to 6 weeks. The wounds were divided into hydrogel alone group, hydrogel/nano sliver group, hydrogel scaffold/nano sliver group, and hydrogel scaffold/nano sliver/ASC group, and transplanted with the corresponding scaffolds, respectively. On post injury day (PID) 4, 7, 14, and 21, the wound healing was observed and the wound healing rate was calculated (n=6). On PID 7 and 14, histopathological changes of wounds were observed by hematoxylin eosin staining (n=6). On PID 21, collagen deposition of wounds was observed by Masson staining (n=3). Data were statistically analyzed with one-way analysis of variance, analysis of variance for repeated measurement, Bonferroni correction, and independent sample t test. Results: The sliver nano particles in nano silver solution with different mass concentrations were all round, in scattered distribution and uniform in size. The silver-containing GelMA hydrogels with different final mass fractions of GelMA all showed pore structures of different sizes and interconnections. The pore size of silver-containing GelMA hydrogel with 10% final mass fraction was significantly larger than that of silver-containing GelMA hydrogels with 15% and 20% final mass fractions (with P values both below 0.05). On treatment day 1, 3, and 7, the concentration of nano silver released from silver-containing GelMA hydrogel in vitro showed a relatively flat trend. On treatment day 14, the concentration of released nano silver in vitro increased rapidly. At 24 h of culture, the diameters of inhibition zone of GelMA hydrogel containing 0, 25, 50, and 100 mg/L nano silver against Staphylococcus aureus and Escherichia coli were 0, 0, 0.7, and 2.1 mm and 0, 1.4, 3.2, and 3.3 mm, respectively. At 48 h of culture, the proliferation activity of Fbs in 2 mg/L nano silver group and 5 mg/L nano silver group was both significantly higher than that in blank control group (P<0.05), and the proliferation activity of Fbs in 10 mg/L nano silver group, 25 mg/L nano silver group, and 50 mg/L nano silver group was all significantly lower than that in blank control group (P<0.05). Compared with the that of Fbs in 0 mg/L silver-containing GelMA hydrogel group, the proliferation activity of Fbs in 50 mg/L silver-containing GelMA hydrogel group and 100 mg/L silver-containing GelMA hydrogel group was all significantly decreased on culture day 1 (P<0.05); the proliferation activity of Fbs in 50 mg/L silver-containing GelMA hydrogel group was significantly increased (P<0.05), while the proliferation activity of Fbs in 100 mg/L silver-containing GelMA hydrogel group was significantly decreased on culture day 3 (P<0.05); the proliferation activity of Fbs in 100 mg/L silver-containing GelMA hydrogel group was significantly decreased on culture day 7 (P<0.05). The proliferation activity of ASCs in 3D bioprinting group show no statistically significant differences to that in non-printing group on culture day 1 (P>0.05). The proliferation activity of ASCs in 3D bioprinting group was significantly higher than that in non-printing group on culture day 3 and 7 (with t values of 21.50 and 12.95, respectively, P<0.05). On culture day 1, the number of dead ASCs in 3D bioprinting group was slightly more than that in non-printing group. On culture day 3 and 5, the majority of ASCs in 3D bioprinting group and non-printing group were living cells. On PID 4, the wounds of rats in hydrogel alone group and hydrogel/nano sliver group had more exudation, and the wounds of rats in hydrogel scaffold/nano sliver group and hydrogel scaffold/nano sliver/ASC group were dry without obvious signs of infection. On PID 7, there was still a small amount of exudation on the wounds of rats in hydrogel alone group and hydrogel/nano sliver group, while the wounds of rats in hydrogel scaffold/nano sliver group and hydrogel scaffold/nano sliver/ASC group were dry and scabbed. On PID 14, the hydrogels on the wound surface of rats in the four groups all fell off. On PID 21, a small area of wounds remained unhealed in hydrogel alone group. On PID 4 and 7, the wound healing rates of rats in hydrogel scaffold/nano sliver/ASC group were significantly higher than those of the other three groups (P<0.05). On PID 14, the wound healing rate of rats in hydrogel scaffold/nano sliver/ASC group was significantly higher than the wound healing rates in hydrogel alone group and hydrogel/nano sliver group (all P<0.05). On PID 21, the wound healing rate of rats in hydrogel alone group was significantly lower than that in hydrogel scaffold/nano sliver/ASC group (P<0.05). On PID 7, the hydrogels on the wound surface of rats in the four groups remained in place; on PID 14, the hydrogel in hydrogel alone group was separated from the wounds of rats, while some hydrogels still existed in the new tissue of the wounds of rats in the other three groups. On PID 21, the collagen arrangement in the wounds of rats in hydrogel alone group was out of order, while the collagen arrangement in the wounds of rats in hydrogel/nano sliver group, and hydrogel scaffold/nano sliver/ASC group was relatively orderly. Conclusions: Silver-containing GelMA hydrogel has good biocompatibility and antibacterial properties. Its three-dimensional bioprinted double-layer structure can better integrate with new formed tissue in the full-thickness skin defect wounds in rats and promote wound healing. 目的： 探讨三维生物打印负载纳米银的甲基丙烯酸酐化明胶（GelMA）水凝胶对大鼠全层皮肤缺损创面的作用。方法： 采用实验研究方法。采用扫描电子显微镜观察不同质量浓度的纳米银溶液中的纳米银颗粒的形态、粒径、分布和含不同终质量分数GelMA的含银GelMA水凝胶的孔隙结构，并计算孔径大小。处理1、3、7、14 d，采用质谱仪检测含终质量分数15% GelMA和终质量浓度10 mg/L纳米银的水凝胶的纳米银释放浓度。培养24 h，检测含终质量浓度0（无纳米银）、25、50、100 mg/L纳米银的GelMA水凝胶对金黄色葡萄球菌和大肠埃希菌的抑菌圈直径。取浙江大学医学院附属第二医院泌尿外科2020年7月收治的1名健康5岁男童包皮环切术后废弃包皮和该院整形外科2020年7月收治的1名健康23岁女性抽脂手术后废弃脂肪，采用酶解法分别提取成纤维细胞（Fb）和脂肪干细胞（ASC）。将Fb分为仅有培养基的空白对照组和另加入含相应终质量浓度纳米银溶液的2 mg/L纳米银组、5 mg/L纳米银组、10 mg/L纳米银组、25 mg/L纳米银组、50 mg/L纳米银组，培养48 h，采用细胞计数试剂盒8检测Fb增殖活性。将Fb分为进行相应处理的0 mg/L含银GelMA水凝胶组、10 mg/L含银GelMA水凝胶组、50 mg/L含银GelMA水凝胶组、100 mg/L含银GelMA水凝胶组，于培养1、3、7 d，同前检测Fb增殖活性。将ASC与GelMA水凝胶混合种植，分为三维生物打印组和非打印组，于培养1、3、7 d，同前检测ASC增殖活性并行活/死细胞荧光染色观察ASC生长情况。以上实验中样本数均为3。于18只雄性4~6周龄SD大鼠背部各制作4个全层皮肤缺损创面，分别设为单纯水凝胶组、水凝胶/纳米银组、水凝胶支架/纳米银组、水凝胶支架/纳米银/ASC组并移植相应支架。分别于伤后4、7、14、21 d，行大体观察并计算创面愈合率（样本数为6）；于伤后7、14 d，对创面行苏木精-伊红染色观察组织病理学改变（样本数为6）；于伤后21 d，对创面行Masson染色观察胶原排列情况（样本数为3）。对数据行单因素方差分析、重复测量方差分析、Bonferroni校正、独立样本t检验。结果： 不同质量浓度的纳米银溶液中的纳米银颗粒均呈圆形，散在分布，粒径均匀。含不同终质量分数GelMA的含银GelMA水凝胶都呈现大小不一且相互连通的孔隙结构。含终质量分数10% GelMA的含银GelMA水凝胶的孔径明显大于含终质量分数15%和20% GelMA的含银GelMA水凝胶（P值均<0.05）。处理1、3、7 d，含银GelMA水凝胶的体外纳米银释放浓度的变化趋势相对平缓；处理14 d，其体外纳米银释放浓度迅速增加。培养24 h，含0、25、50、100 mg/L纳米银的GelMA水凝胶对金黄色葡萄球菌和大肠埃希菌的抑菌圈直径分别为0、0、0.7、2.1 mm和0、1.4、3.2、3.3 mm。培养48 h，2 mg/L纳米银组、5 mg/L纳米银组Fb的增殖活性均明显高于空白对照组（P<0.05），10 mg/L纳米银组、25 mg/L纳米银组、50 mg/L纳米银组Fb的增殖活性均明显低于空白对照组（P<0.05）。与0 mg/L含银GelMA水凝胶组相比，培养1 d，50 mg/L含银GelMA水凝胶组、100 mg/L含银GelMA水凝胶组Fb的增殖活性均明显降低（P<0.05）；培养3 d，50 mg/L含银GelMA水凝胶组Fb的增殖活性明显升高（P<0.05），100 mg/L含银GelMA水凝胶组Fb的增殖活性明显降低（P<0.05）；培养7 d，100 mg/L含银GelMA水凝胶组Fb的增殖活性明显降低（P<0.05）。培养1 d，三维生物打印组的ASC增殖活性与非打印组比较，差异无统计学意义（P>0.05）；培养3、7 d，三维生物打印组的ASC增殖活性均明显高于非打印组（t值分别为21.50、12.95，P<0.05）。培养1 d，三维生物打印组死亡ASC数略多于非打印组。培养3、5 d，三维生物打印组和非打印组中的绝大多数ASC为活细胞。伤后4 d，单纯水凝胶组和水凝胶/纳米银组大鼠创面渗液较多，水凝胶支架/纳米银组和水凝胶支架/纳米银/ASC组大鼠创面干燥且未见明显感染迹象。伤后7 d，单纯水凝胶组和水凝胶/纳米银组大鼠创面仍有少量渗液，水凝胶支架/纳米银组和水凝胶支架/纳米银/ASC组大鼠创面干燥结痂。伤后14 d，4组大鼠创面上的水凝胶均脱落。伤后21 d，仅单纯水凝胶组仍有少量创面未愈合。伤后4、7 d，水凝胶支架/纳米银/ASC组大鼠创面愈合率均明显高于其他3组（P<0.05）。伤后14 d，水凝胶支架/纳米银/ASC组大鼠创面愈合率明显高于水凝胶/纳米银组和单纯水凝胶组（P值均<0.05）。伤后21 d，单纯水凝胶组大鼠创面愈合率明显低于水凝胶支架/纳米银/ASC组（P<0.05）。伤后7 d，4组大鼠创面上的水凝胶均保持在位；伤后14 d，单纯水凝胶组大鼠的水凝胶已与创面脱离，而其余3组仍有部分水凝胶存在于创面新生组织中。伤后21 d，单纯水凝胶组大鼠创面胶原排列无序，而水凝胶/纳米银组、水凝胶支架/纳米银组、水凝胶支架/纳米银/ASC组大鼠创面胶原排列相对有序。结论： 含银GelMA水凝胶具有良好的生物相容性及抗菌性能，其三维生物打印的双层结构能更好地与大鼠全层皮肤缺损创面新生组织相融合并促进创面愈合。.

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