微米尺度的规则拓扑结构对细胞和组织行为的影响

生物材料表面的物理性质,如拓扑结构,由于其易于加工和稳定的生物作用而受到广泛关注.虽然已有许多研究报道了材料表面拓扑结构与细胞的相互作用,但由于不同研究中使用的微结构和实验环境的多样性,生物材料表面不同微结构与细胞/组织行为之间的影响关系尚未得到很好的统一评价.在本研究中,我们设计了11种图案(三角形、矩形、圆形等),这些图案包含两种类型的形貌(微坑和微柱),这样一共得到22种表面拓扑结构.我们在体外和体内对这些微结构影响细胞和组织的生物作用进行了评估.我们的研究结果表明,由连续微坑形成的凹槽微结构促进细胞迁移效果相比其他微结构更强.其中,由三角形微坑组成的凹槽在体外对细胞迁移的促进作用最强.在大鼠皮下模型中,这种三角形微坑组成的凹槽结构减少了纤维组织的包封,促进了血管的形成.

Substrate stiffness differentially impacts autophagy of endothelial cells and smooth muscle cells

Stiffening of blood vessels is one of the most important characteristics in the process of many cardiovascular pathologies such as atherosclerosis,angiosteosis,and vascular aging.Increased stiffness of the vascular extracellular matrix drives artery pathology and alters phenotypes of vascular cell.Understanding how substrate stiffness impacts vascular cell behaviors is of great importance to the biomaterial design in tissue engineering,regenerative medicine,and medical devices.Here we report that changing substrate stiffness has a significant impact on the autophagy of vascular endothelial cells(VECs)and smooth muscle cells(VSMCs).Interestingly,our findings demonstrate that,with the increase of substrate stiffness,the autophagy level of VECs and VSMCs showed differential changes:endothelial autophagy levels reduced,leading to the reductions in a range of gene expression associated with endothelial function;while,autophagy levels of VSMCs increased,showing a transition from contractile to the synthetic phenotype.We further demonstrate that,by inhibiting cell autophagy,the expressions of endothelial functional gene were further reduced and the expression of VSMC calponin increased,suggesting an important role of autophagy in response of the cells to the challenge of microenvironment stiffness changing.Although the underlying mechanism requires further study,this work highlights the relationship of substrate stiffness,autophagy,and vascular cell behaviors,and enlightening the design principles of surface stiffness of biomaterials in cardiovascular practical applications.

UV-triggered Polymerization of Polyelectrolyte Composite Coating with Pore Formation and Lubricant Infusion

Porous coatings with the features of muti-interfaces and high specific surface area have emerged as an excellent material platform for the manipulation of porous structures.Layer-by-layer(Lb L)assembly technique has been widely used in preparing porous polyelectrolyte coatings.However,the efficient construction of stable film from the Lb L technique is still a question.Herein,we reported a new solution to construct a stabilized polyelectrolyte coating with porous structures.Inspired by the mechanical reinforcement of double-network hydrogel,we constructed the poly(ethylenimine)(PEI)/poly(acrylic acid)(PAA)coating by in situ photopolymerization of acrylic acid in the PEI network instead of assembling PEI and PAA.Compared with the Lb L films,the in situ polymerized coating kept higher stability after 30 iterations of friction.Porous structures could also be constructed after acid treatment,which was utilized to load lubricant to enhance the lubricating property of the coating.This work provides a new method for the construction of dynamic and stable polyelectrolyte coatings,expediting more development of practical applications.

聚合物材料表面微结构调控新策略

聚合物材料表面微结构对其功能化的实现具有至关重要的作用。在过去几十年的时间里,通过电纺、光刻、等离子处理等经典方法制备了各种各样的结构功能表面,实现在光、电、生物、化学等领域的广泛应用。然而为满足技术发展需求,实现表面微结构调控新策略的开发势不可挡。本文主要从分子扩散、材料内应力、外力的施加/释放,以及多种机制协同作用四个角度出发对聚合物表面结构调控的新策略进行介绍,并对今后聚合物表面结构调控的发展方向进行简要论述。

调控非共价相互作用实现聚电解质膜内多孔形成的研究

静电层状组装聚电解质膜主要由静电作用为驱动力,带有相反电荷的聚电解质在基底表面进行交替沉积制得,其结构可以通过膜内分子运动性的改变来调控.本研究在静电作用基础上,通过在聚丙烯酸(PAA)上接枝偶氮苯基团(Azo),得到含有2种非共价相互作用的聚乙烯亚胺/偶氮苯修饰的聚丙烯酸(PEI/PAA-Azo)膜.利用光照和弱酸溶液对2种相互作用进行顺序调控,实现在PEI/PAA-Azo膜内区域、可逆地构建微孔结构.进一步地,利用该体系展开了区域负载功能分子以及局部调控生物膜的形成的研究.本研究为探究聚电解质膜内分子运动性对膜结构和动态性的影响提供了一种可行的策略,并且拓展了聚电解质膜的应用前景.

miR-22 eluting cardiovascular stent based on a self-healable spongy coating inhibits in-stent restenosis

The in-stent restenosis(IRS)after the percutaneous coronary intervention contributes to the major treatment failure of stent implantation.MicroRNAs have been revealed as powerful gene medicine to regulate endothelial cells(EC)and smooth muscle cells(SMC)in response to vascular injury,providing a promising therapeutic candidate to inhibit IRS.However,the controllable loading and eluting of hydrophilic bioactive microRNAs pose a challenge to current lipophilic stent coatings.Here,we developed a microRNA eluting cardiovascular stent via the self-healing encapsulation process based on an amphipathic poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone)(PCL-PEG-PCL,PCEC)triblock copolymer spongy network.The miR-22 was used as a model microRNA to regulate SMC.The dynamic porous coating realized the uniform and controllable loading of miR-22,reaching the highest dosage of 133 pmol cm^(-2).We demonstrated that the sustained release of miR-22 dramatically enhanced the contractile phenotype of SMC without interfering with the proliferation of EC,thus leading to the EC dominating growth at an EC/SMC ratio of 5.4.More importantly,the PCEC@miR-22 coated stents showed reduced inflammation,low switching of SMC phenotype,and low secretion of extracellular matrix,which significantly inhibited IRS.This work provides a simple and robust coating platform for the delivery of microRNAs on cardiovascular stent,which may extend to other combination medical devices,and facilitate practical application of bioactive agents in clinics.

Dynamically softened substrate regulates malignancy of breast tumor cells

It has long been hypothesized that an increase in the extracellular matrix(ECM)stiffness mechanoactivates malignant phenotypes of breast tumor cells by regulating an array of processes underlying cancer biology.Although the contribution of substrate stiffening to drive malignant phenotype traits and other biological functions of a tumor is increasingly understood,the functional role of substrate softening on breast cancer cellular responses has rarely been investigated.Herein,we employed matrix metalloproteinase(MMP)-sensitive film to perform assays to explore the consequences of lowering stiffness on the biological behaviors of breast cancer cell MDA-MB-231.We demonstrated that cells underwent dramatic changes in migration,cellular conjunction,and expression of malignance-associated proteins and genes when the substrate stiffness decreased.Based on RNA sequencing and analysis,we found that hub genes including TP53,CCND1,MYC,CTNNB1,and YAP were validated to play central parts in regulating stiffness-dependent cellular manner change.Moreover,through visualization of differentially expressed genes(DEGs),cells on dynamically softened substrate appeared less influenced by transfer to tissue culture polystyrene(TCPS).These results suggest substrates with decreasing stiffness could normalize breast tumor malignant phenotype and help cells store the mechanical memory of the consequential weaker malignance.

Tough Polyion Complex Hydrogel Films of Natural Polysaccharides

The developments of tough hydrogels in recent years have greatly expanded the applications of hydrogels as structural materials. However, most of the tough hydrogels are made of synthetic polymers. To develop biopolymer-based tough hydrogels has both fundamental and practical significances. Here we report a series of polysaccharides-based tough hydrogel films prepared by polyion complexation and solvent evaporation of chondroitin sulfate（CS） and protonated chitosan（CHT） solutions with different weight ratios. The obtained CS/CHT gel films with thickness of 40-80 μm and water content of 66 wt%-81 wt% possess excellent mechanical properties, with tensile breaking stress and breaking strain being 0.4-3 MPa and 160%-320%, respectively. We found that in the mixture solutions there are large amounts of excess CHT in terms of charges; after swelling the films in water, the acetic acid, which is used to protonate the amino groups of CHT, diffuses out of the gel matrix, enhancing the intermolecular interactions between CHT molecules and thus improving the mechanical properties of gel films, besides the ionic bonds between CS and CHT. Antimicrobial tests also showed that the gel films with low weight ratio of CS to CHT, corresponding to the case with excess CHT, have evident antimicrobial effect. These CS/CHT gel films with good mechanical properties and antimicrobial effect should extend the applications of hydrogels in biomedical fields.