Photocrosslinkable methacrylated gelatin hydrogel as a cell-friendly injectable delivery system for chlorhexidine in regenerative endodontics

ObjectivesThis work sought to formulate photocrosslinkable chlorhexidine (CHX)-laden methacrylated gelatin (CHX/GelMA) hydrogels with broad spectrum of action against endodontic pathogens as a clinically viable cell-friendly disinfection therapy prior to regenerative endodontics procedures.MethodsCHX/GelMA hydrogel formulations were successfully synthesized using CHX concentrations between 0.12 % and 5 % w/v. Hydrogel microstructure was evaluated by scanning electron microscopy (SEM). Swelling and enzymatic degradation were assessed to determine microenvironmental effects. Compression test was performed to investigate the influence of CHX incorporation on the hydrogels’ biomechanics. The antimicrobial and anti-biofilm potential of the formulated hydrogels were assessed using agar diffusion assays and a microcosms biofilm model, respectively. The cytocompatibility was evaluated by exposing stem cells from human exfoliated deciduous teeth (SHEDs) to hydrogel extracts (i.e., leachable byproducts obtained from overtime hydrogel incubation in phosphate buffer saline). The data were analyzed using One- and Two-way ANOVA and Tukey’s test (α = 0.05).ResultsCHX/GelMA hydrogels were effectively prepared. NMR spectroscopy confirmed the incorporation of CHX into GelMA. The addition of CHX did not change the micromorphology (pore size) nor the swelling profile (p > 0.05). CHX incorporation reduced the degradation rate of the hydrogels (p < 0.001); whereas, it contributed to increased compressive modulus (p < 0.05). Regarding the antimicrobial properties, the incorporation of CHX showed a statistically significant decrease in the number of bacteria colonies at 0.12 % and 0.5 % concentration (p < 0.001) and completely inhibited the growth of biofilm at concentration levels 1 %, 2 %, and 5 %. Meanwhile, the addition of CHX, regardless of the concentration, did not lead to cell toxicity, as cell viability values were above 70 %.SignificanceThe addition of CHX into GelMA showed significant antimicrobial action against the pathogens tested, even at low concentrations, with the potential to be used as a cell-friendly injectable drug delivery system for root canal disinfection prior to regenerative endodontics.     

Organ bioengineering for the newborn

Regenerative medicine has recently been established as an emerging interdisciplinary field focused on the repair; replacement or regeneration of cells, tissues and organs. It involves various disciplines, which are focused on different aspects of the regeneration process such as cell biology, gene therapy, bioengineering, material science and pharmacology. In this article, we will outline progress on tissue engineering of specific tissues and organs relevant to paediatric surgery.     

松质骨基质复合生物蛋白胶构建组织工程软骨的研究

目的尝试采用松质骨基质与生物蛋白胶复合材料构建组织工程软骨。方法体外培养大鼠软骨细胞,接种于松质骨基质／生物蛋白胶材料上行体外培养。采用HE、甲苯胺蓝染色免疫学检测、扫描电镜观察等方法观察所构建的组织工程软骨的特性。结果松质骨基质／生物蛋白胶组的组织学结构更接近于软骨样组织．其Ⅱ型胶原、蛋白多糖基因表达量及蛋白多糖含量明显高于松质骨基质组。结论松质骨基质／生物蛋白胶复合材料可用于构建组织工程软骨,是一种较理想的支架材料。     

Controlled 3D culture in Matrigel microbeads to analyze clonal acinar development

3D culture systems are a valuable tool for modeling morphogenesis and carcinogenesis of epithelial tissue in a structurally appropriate context. We present a novel approach for 3D cell culture based on a flow-focusing microfluidic system that encapsulates epithelial cells in Matrigel beads. As a model we use prostatic and breast cells and assay for development of acini, polarized cellular spheres enclosing lumen. Each individual bead on average acts as a single 3D cell culture compartment generating one acinus per bead. Compared to standard protocols microfluidics provides increased control over the environment leading to more a uniform acini population. The increased facility of bead manipulation allowed us to isolate single cells which are self-sufficient to fully develop into acini in presence of Matrigel. Furthermore, combination of our microfluidic approach with large particle FACS opens new avenues in high throughput screening on single acini or spheroids.     

仿生矿化后的丝素电纺复合支架体内成骨性能的实验研究

目的探讨仿生矿化后的丝素电纺复合支架体内修复颅骨缺损的能力。方法利用静电纺丝技术制备丝素电纺支架(非矿化组),通过模拟体液(SBF)浸泡法对支架仿生矿化(矿化组),扫描电镜观察其微观形貌。18只8周龄的雄性SD大鼠购自南京医科大学动物实验中心,采用随机数字表示法分为3组,分别为矿化组、非矿化组和对照组,每组6只。构建SD大鼠颅骨缺损模型,在直径为5 mm的骨缺损区分别植入矿化组及非矿化组支架,对照组不作处理,分别于术后4、8周取材,通过微计算机断层扫描技术(micro-CT)、苏木精-伊红(HE)及马松染色(Masson染色)比较评估不同支架的体内骨再生情况。应用GraphPad Prism 8统计软件分析,采用单因素方差分析。结果扫描电镜结果显示仿生矿化后的丝素电纺支架表面形成明显的羟基磷灰石矿化层。动物实验结果显示,术后4周和8周,通过对CT三维重建、HE及Masson染色的观察以及对骨体积分数(BV/TV),骨小梁数(Tb.N),骨小梁厚度(TB.Th)和骨小梁间隙(TB.Sp)定量指标的分析结果显示,在矿化组和非矿化组均能观察到新骨的形成,且矿化组的修复效果均优于非矿化组,差异有统计学意义[矿化组、非矿化组及对照组BV/TV在4周时分别为(22.880±2.324)、(12.600±1.965)、(4.967±1.580)%,F=61.838,P<0.05,8周时分别为(45.770±4.433)、(29.400±4.086)、(19.310±2.272)%,F=38.686,P<0.05;Tb.N在4周时分别为(0.029±0.001)、(0.019±0.003)、(0.008±0.003)mm-1,F=52.890,P<0.05,8周时分别为(0.053±0.002)、(0.037±0.003)、(0.023±0.001)mm-1,F=171.433,P<0.05;TB.Sp在4周时分别为(10.810±0.179)、(11.350±0.098)、(11.730±0.163)μm,F=27.655,P<0.05,8周时分别为(8.792±0.175)、(10.060±0.339)、(11.150±0.275)μm,F=56.807,P<0.05]。结论仿生矿化后的丝素电纺复合支架能有效促进骨再生,有望用于骨组织工程。     

基于三维打印的钙化层重建生物活性支架制备及其性能研究

目的初步构建基于软骨钙化层损伤重建的有机—无机复合组织工程支架,探究掺镁硅灰石含量与支架抗压性能之间的关系。方法利用质量分数分别为1%、3%、5%的高生物活性钙镁硅酸盐超细颗粒复合Ⅰ型胶原—透明质酸钠进行三维打印,经海藻酸钠—氯化钙气雾交联成型,电镜下观察表面孔隙、孔径、无机相分布,万能材料试验机测试抗压性能,并计算支架孔隙率。结果支架表面平均孔径(212.3±34.2)μm,平均孔隙率(48.3±5.9)%,不同质量分数的高生物活性钙镁硅酸盐超细颗粒复合Ⅰ型胶原—透明质酸钠支架压缩模量差异无统计学意义( P>0.05),平均压缩模量(7.2±1.2)MPa,介于软骨和软骨下骨之间。 结论利用三维打印技术成功构建出多孔钙化层仿生重建支架,可为今后研制多层次复合支架治疗骨—软骨损伤奠定基础。     

Research on Fall Prevention and Protection from Heights in Japan

The high frequency of fall accidents is a serious problem in Japan. Thus, more stringent countermeasures for preventing falls from scaffolds were developed and incorporated into institutional guidelines. These countermeasures aim to decrease deaths caused by falls from scaffolds. Despite the improvements in such measures, however, the rate of accidental fall deaths remains high in Japan’s construction industries. To improve the rigor of the countermeasures, a committee was established in our institute by the Japan Ministry of Health, Labour, and Welfare. This committee investigated the regulations applied in other countries and evaluated construction industry compliance with existing fall prevention guidelines. After considerable research and discussion, the Occupational Safety and Health Regulations and Guidelines were amended in 2009. The effects of the amended regulations have recently been investigated on the basis of accident reports. This paper describes the investigation and its results. The paper also discusses other research and workplace safety countermeasures for preventing falls and ensuring fall protection from heights.