Lotus-leaf-like topography predominates over adsorbed ECM proteins in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) surface/cell interactions

Replication of natural surface topographies to generate advanced cell culture substrates

Surface topographies of cell culture substrates can be used to generate in vitro cell culture environments similar to the in vivo cell niches. In vivo, the physical properties of the extracellular matrix (ECM), such as its topography, provide physical cues that play an important role in modulating cell function. Mimicking these properties remains a challenge to provide in vitro realistic environments for cells. Artificially generated substrates' topographies were used extensively to explore this important surface cue. More recently, the replication of natural surface topographies has been enabling to exploration of characteristics such as hierarchy and size scales relevant for cells as advanced biomimetic substrates. These substrates offer more realistic and mimetic environments regarding the topographies found in vivo. This review will highlight the use of natural surface topographies as a template to generate substrates for in-vitro cell culture. This review starts with an analysis of the main cell functions that can be regulated by the substrate's surface topography through cell-substrate interactions. Then, we will discuss research works wherein substrates for cell biology decorated with natural surface topographies were used and investigated regarding their influence on cellular performance. At the end of this review, we will highlight the advantages and challenges of the use of natural surface topographies as a template for the generation of advanced substrates for cell culture.

Delivering Mechanical Stimulation to Cells: State of the Art in Materials and Devices Design

Biochemical signals, such as growth factors, cytokines, and transcription factors are known to play a crucial role in regulating a variety of cellular activities as well as maintaining the normal function of different tissues and organs. If the biochemical signals are assumed to be one side of the coin, the other side comprises biophysical cues. There is growing evidence showing that biophysical signals, and in particular mechanical cues, also play an important role in different stages of human life ranging from morphogenesis during embryonic development to maturation and maintenance of tissue and organ function throughout life. In order to investigate how mechanical signals influence cell and tissue function, tremendous efforts have been devoted to fabricating various materials and devices for delivering mechanical stimuli to cells and tissues. Here, an overview of the current state of the art in the design and development of such materials and devices is provided, with a focus on their design principles, and challenges and perspectives for future research directions are highlighted.

Conductive photothermal non-swelling nanocomposite hydrogel patch accelerating bone defect repair

Bone defect repair is one of the most common issue in clinic. Developmental multifunctional scaffolds have become a promising strategy to effectively promote bone defect repair. Here, a series of...

Vascular cell behavior on heparin-like polymers modified silicone surfaces: The prominent role of the lotus leaf-like topography

Vascular cell behavior on material surfaces, such as heparin-like polymers, can be affected by the surface chemical composition and surface topological structure. In this study, the effects of heparin-like polymers and lotus leaf-like topography on surface vascular cell behavior are considered. By combining multicomponent thermo-curing and replica molding, a polydimethylsiloxane surface containing bromine (PDMS-Br) with lotus leaf-like topography is obtained. Heparin-like polymers with different chemical compositions are grafted onto PDMS-Br surfaces using visible-light-induced graft polymerization. Compared with unmodified PDMS-Br, surfaces modified by sulfonate-containing polymers are more friendly to vascular cells, while those modified by a glyco-polymer are much more resistant to vascular cells. The introduction of lotus leaf-like topography results in different degrees of decrease in cell density on different heparin-like polymer-modified surfaces. In addition, the combination of heparin-like polymers and lotus leaf-like topography results in the change in protein adsorption, indicating that the two factors may affect the surface vascular cell behavior by affecting the adsorption of relative proteins. The combination of bionic surface topography and different chemical components of heparin-like polymers on material surfaces suggests a new way of engineering cell-material interactions.

Rational Design of PMPC/PDMC/PEGDA Hydrogel Micropatterns onto Polylactic Acid with Enhanced Biological Activity

Polylactic acid (PLA) is one of the biodegradable materials that has been used in the areas of surgical healing lines, cancer treatment, and wound healing. However, the application of PLA is still rather limited due to its high hydrophobicity and poor antibacterial activity. In order to enhance the antifouling and antibacterial performances of PLA, here we modified the surface of PLA with various sizes of hydrogel micropatterns in negative or positive mode using plasma treatment, the photomask technique, and UV-graft polymerization. The hydrogel micropatterns consist of poly(ethylene glycol) diacrylate (PEGDA), poly(2-methacryloyloxyethylphosphorylcholine) (PMPC), and poly(methacryloyloxyethyltrimethylammonium chloride) (PDMC). Compared to PLA, the patterned PLA (PLA-PMPC/PDMC/PEGDA) shows obviously enhanced antifouling and antibacterial activities. For PLA-PMPC/PDMC/PEGDA with either positive or negative micropatterns, the antifouling and antibacterial properties are gradually increasing with decreasing the size of micropatterns. Compared with PLA-PMPC/PDMC/PEGDA bearing positive and negative micropatterns in the same size, the PLA-PMPC/PDMC/PEGDA with negative micropatterns exhibits slightly better biological activity and the PLA-PMPC/PDMC/PEGDA with 3 μm negative hydrogel micropatterns shows the best hydrophilicity, antifouling, and antibacterial properties. Combining the in vitro hemolysis assay, cytotoxicity, water absorption test, and degradation test results, it is suggested that the fabrication of hydrogel micropatterns onto the PLA surface could significantly improve biological activities of PLA. We expect that this work would provide a new strategy to potentially develop PLA as a promising wound dressing.

Hydrogels with Lotus Leaf Topography: Investigating Surface Properties and Cell Adhesion

The interactions of cells with the surface of materials is known to be influenced by a range of factors that include chemistry and roughness; however, it is often difficult to probe these factors individually without also changing the others. Here we investigate the role of roughness on cell adhesion while maintaining the same underlying chemistry. This was achieved by using a polymerization in mold technique to prepare poly(hydroxymethyl methacrylate) hydrogels with either a flat topography or a topography that replicated the microscale features of lotus leaves. These materials were then assessed for cell adhesion, and atomic force microscopy and contact angle analysis were then used to probe the physical reasons for the differing behavior in relation to cell adhesion.

Combined Chemical Groups and Topographical Nanopattern on the Poly(ε-Caprolactone) Surface for Regulating Human Foreskin Fibroblasts Behavior

Surface chemistry and substrate topography could contribute significantly to providing a biochemical and topographical cues for governing the fate of cells on the cell-material interface. However, the synergies between these two properties have not been exploited extensively for biomaterial design. Herein, we achieved spatial-controlled patterning of chemical groups on the poly(ε-caprolactone) (PCL) surface by elegant UV-nanoimprint lithography (UN-NIL). The introduction of chemical groups on the PCL surface was developed by our newly 6-benzyloxycarbonylmethyl-ε-caprolactone (BCL) monomer, which not only solved the lack of functional groups along the PCL chain but also retained the original favorable properties of PCL materials. The synergetic effect of the chemical groups and nanopatterns on the human foreskin fibroblasts (HFFs) behaviors was evaluated in detail. The results revealed that the patterned functional PCL surfaces could induce enhanced cell adhesion and proliferation, further trigger changes in HFFs morphology, orientation and collagen secretion. Taken together, this study provided a method for straightforward fabrication of reactive PCL surfaces with topographic patterns by one-step process, and they would facilitate PCL as potential candidate for cell cultivation and tissue engineering.

Electroactive degradable copolymers enhancing osteogenic differentiation from bone marrow derived mesenchymal stem cells

Osteogenic differentiation from bone marrow derived mesenchymal stem cells was significantly enhanced by electroactive degradable copolymers.

Fabrication of MPEG-b-PMAA capped YVO4:Eu nanoparticles with biocompatibility for cell imaging

A novel nanoparticle with multilayer core-shell architecture for cell imaging is designed and synthesized by coating a fluorescent YVO4:Eu core with a diblock copolymer, MPEG-b-PMAA. The synthesis of YVO4:Eu core, which further makes MPEG-b-PMAA-YVO4:Eu NPs adapt for cell imaging, is guided by the model determined upon the evaluation of pH and CEu%. The PMAA block attached tightly on the YVO4:Eu core forms the inner shell and the MPEG block forms the biocompatible outermost shell. Factors including reaction time, reaction temperature, CEu% and pH are optimized for the preparation of the YVO4:Eu NPs. A precise defined model is established according to analyzing the coefficients of pH and CEu% during the synthesis. The MPEG-b-PMAA-YVO4:Eu NPs, with an average diameter of 24 nm, have a tetragonal structure and demonstrate luminescence in the red region, which lies in a biological window (optical imaging). Significant enhancement in luminescence intensity by MPEG-b-PMAA-YVO4:Eu NPs formation is observed. The capping copolymer MPEG-b-PMAA improves the dispersibility of hydrophobic YVO4:Eu NPs in water, making the NPs stable under different conditions. In addition, the biocompatibility MPEG layer reduces the cytotoxicity of the nanoparticles effectively. 95% cell viability can be achieved at the NPs concentration of 800 mgL(-1) after 24h of culture. Cellular uptake of the MPEG-b-PMAA-YVO4:Eu NPs is evaluated by cell imaging assay, indicating that the NPs can be taken up rapidly and largely by cancerous or non-cancerous cells through an endocytosis mechanism.

Theoretical Explanation of the Lotus Effect: Superhydrophobic Property Changes by Removal of Nanostructures from the Surface of a Lotus Leaf

Theoretical study is presented on the wetting behaviors of water droplets over a lotus leaf. Experimental results are interpreted to clarify the trade-offs among the potential energy change, the local pinning energy, and the adhesion energy. The theoretical parameters, calculated from the experimental results, are used to qualitatively explain the relations among surface fractal dimension, surface morphology, and dynamic wetting behaviors. The surface of a lotus leaf, which shows the superhydrophobic lotus effect, was dipped in ethanol to remove the plant waxes. As a result, the lotus effect is lost. The contact angle of a water drop decreased dramatically from 161° of the original surface to 122°. The water droplet was pinned on the surface. From the fractal analysis, the fractal region of the original surface was divided into two regions: a smaller-sized roughness region of 0.3-1.7 μm with D of 1.48 and a region of 1.7-19 μm with D of 1.36. By dipping the leaf in ethanol, the former fractal region, characterized by wax tubes, was lost, and only the latter large fractal region remained. The lotus effect is attributed to a surface structure that is covered with needle-shaped wax tubes, and the remaining surface allows invasion of the water droplet and enlarges the interaction with water.

Guiding the behaviors of human umbilical vein endothelial cells with patterned silk fibroin films

Silk fibroin is an ideal blood vessel substitute due to its advantageous qualities including variable size, good suture retention, low thrombogenicity, non-toxicity, non-immunogenicity, biocompatibility, and controllable biodegradation. In this study, silk fibroin films with a variety of surface patterns (e.g. square wells, round wells plus square pillars, square pillars, and gratings) were prepared for in vitro characterization of human umbilical vein endothelial cell's (HUVEC) response. The affects of biomimetic length-scale topographic cues on the cell orientation/elongation, proliferation, and cell-substrate interactions have been investigated. The density of cells is significantly decreased in response to the grating patterns (70±3nm depth, 600±8nm pitch) and the square pillars (333±42nm gap). Most notably, we observed the contact guidance response of filopodia of cells cultured on the surface of round wells plus square pillars. Overall, our data demonstrates that the patterned silk fibroin films have an impact on the behaviors of human umbilical vein endothelial cells.