No abstract

One of the challenges in tissue engineering is the design of optimal biomedical scaffolds, which can be governed by both physical and chemical properties, such as structural properties (porosity, pore size, and tortuosity) and surface characteristics. Of these properties, we observed the effects of nano-to microsized hierarchical surface. To achieve the hierarchical surface structure on poly(3-caprolactone) (PCL) film, we employed an electric-field-aided nano/micro-casting technique (FA-NCT) to mimic a typical natural hierarchical structure, the lotus leaf. The sizes of the microsized structures in lotus leaf replicas were controlled by employing or not employing the electric field during casting. The hierarchical surfaces showed two different roughness ranges for the microsized structure and the nanosized structure: (1) 1.7 AE 0.2 mm and 627 AE 163 nm and (2) 3.2 AE 0.3 mm and 635 AE 127 nm, respectively. To reduce the hydrophobicity in the replicated surfaces, they were coated with phlorotannin (Ph), which is derived from brown algae and has been used as a tissue regenerating material due to its hydrophilicity and various growth factors. Osteoblast-like-cells (MG63) were cultured on various surfaces. The hierarchical structure induced high cell viability compared to that of the smooth surface. Moreover, calcium deposition was enhanced when the roughness of the microsized structures in the hierarchical structure was increased. From the results, we suggest that control of the formation of micro-structure in a hierarchical structure is an important design factor along with the optimal nanostructure.

Bioreactor systems in tissue engineering applications provide various types of stimulation to mimic the tissues in vitro and in vivo. Various bioreactors have been designed to induce high cellular activities, including initial cell attachment, cell growth, and differentiation. Although cell-stimulation processes exert mostly positive effects on cellular responses, in some cases such stimulation can also have a negative effect on cultured cells. In this review, we discuss various types of bioreactor and the positive and negative effects of stimulation (physical, chemical, and electrical) on various cultured cell types.

Here, we propose a new combinational method supplemented with melt-plotting and in situ plasma treatment to improve the coating ability of chitosan solution. Using the proposed method, the hydrophobic surface of poly(3-caprolactone) (PCL) was altered to a hydrophilic surface to facilitate homogeneous coating of the micro-structured PCL scaffold with chitosan of various molecular weights.The fabricated chitosan-coated PCL scaffolds were assessed in terms of not only physical properties, including tensile strength and water uptake ability, but also biological capabilities by culturing osteoblast-like cells (MG63) in the presence of coatings of chitosan of various molecular weights (1-5, 5-10, and >10 kDa). The chitosan-based scaffolds showed complete water absorption ability and significantly increased mechanical properties (13-36% increase in Young's modulus) compared to the untreated PCL scaffold. A number of assays (fluorescence analysis, alkaline phosphatase (ALP) activity, and calcium deposition) indicated that the scaffold coated with high-molecular-weight chitosan induced highly active cellular responses that would be of interest for bone-tissue regeneration.