The stem cell is defined in terms of pluripotency and self-renewability. However, the fact is that the cell population called “stem cells” is gathering of the cells with various differentiation stages of various lineages. The authentic stem cells are just small parts of the cells in the population. Since the stem cells differentiate into many kinds of cells, it is difficult to strict the lineage toward the necessary cells. We have developed a method for differentiation of embryonic stem cells into the retinal cells. However, a lot of cells differentiate into other cells. Therefore, it is necessary to select required cells and to purify them. Moreover, ES cell transplantation is allogenic transplantation and may cause immune rejection. It is the iPS cell that might solves the problem.
In the multileveled bio-engineering including amino-acids, proteins, organelle, cells, tissues, and organs, control of hetero-biointerfaces is a key technology. In particular, recent development of nanotechnology has made the nanoscaled control possible. In this article, we selected current topics in the hetero-biointerfaces. In the layer-by-layer stacking technique of cells, artificial tissues similar to a blood vessel has been realized. Phospholipid polymers similar to cell membrane were used to control the biomaterial surfaces. Properties of their interfaces with proteins are analyzed focusing on functions of the interface water layers. Selective adsorption of protein molecules on a solid surface is also demonstrated. In the biointerface engineering, nanoscale control play crucial roles.
A lipid bilayer, which is formed by a self-assembly process of lipid molecules, is a basic structural component of a cell membrane. A lipid bilayer can be adsorbed on a solid surface at a single bilayer level. An adsorbed lipid bilayer is called a supported lipid bilayer (SLB). An SLB maintains the fluidity of the cell membrane, which is known as lateral diffusion, and this will be of great interest to surface scientists. This review focuses on the progress of recent research on SLBs achieved by employing surface science techniques, and also describes the basic techniques for preparing and characterizing SLBs. Specifically, this work addresses the effect of a solid surface on the physical properties of an SLB, SLB pattern formation using the photo-induced polymerization of acetylene embedded within an SLB, the control of self-spreading behavior using structured surfaces, and the dynamics of single molecules moving within an SLB.
The soft-nanotechnology that treats softmatter in nanometer scale needs to develop proper and original techniques for analyzing and handling the softmatter. The surface analysis of solids under vacuum condition has made remarkable progress. However, softmatter samples in vacuum atmosphere change their original properties, and are easily damaged by high energy probe beams. Thus, it is not suitable to observe “raw state” of the softmatter samples by the conventional surface analysis techniques. Scanning probe microscopy (SPM) such as atomic force microscopy (AFM) can analyze softmatter samples in moderate condition in air and water. Optical probe technique such as infrared absorption spectroscopy (IRAS) is also nondestructive method to analyze the softmatter samples. Scanning near-filed optical microscopy (SNOM), combined SPM and optical spectroscopy, enables the simultaneous measurements of topography and optical information. Here, we briefly introduce outlines of AFM, MIR-IRAS (Multiple internal reflection IRAS), and SNOM and examples of their applications.
The progress of nano-technology enables us to manipulate bio-molecules directly on the substrate. In particular, recent development in chemical treatment of solid surfaces and nano-fabrication on them provides a variety of fine controlled substrates. Surface condition of the nano-controlled substrate is critically important for the handling of bio-molecules such as proteins, nucleotide acids, lipid, glycan etc. The compatibility between solid surfaces and bio-molecules, in other words bio-interface, is a key factor for the success in interdisciplinary study of nano-technology and biology. With increasing performance of computers, it has become a possible and practical research target to analyze the interfacial interaction between bio-molecules and solid surfaces. The findings from the computational study are helpful for interpreting experimental results and enhance the understanding of the interface phenomena. Further, theoretical approach will be indispensable for the design of bio-solid interface. In this paper, we demonstrate the advantage of collaborative approach between experiments and computation, exemplifying several studies to analyze the behavior of proteins on the surface.
As a cutting-edge of the “Bio-interface” which can recognize various bio-environments and induce the dynamic response, three researches have been achieved for the medical application based on the functions of the biomembrane. The first is the “bio-imaging” of the HIF-1 activation region at low oxygen state by using the molecular probe conjugating an oxygen-dependent degradation (ODD) domain, a part of HIF-1α protein, with a protein transduction domain (PTD). The second is the polymer carrier for “smart DDS” that can recognize the domestic function and environment in the biosystem and can induce its conformational change for the nucleic acid delivery with low toxicity and high efficiency. The third is “immobilized liposome membrane” for artificial kidney (ILM-AK) which can recognize/adsorb the structurally-abnormal proteins and release them by utilizing various potential functions of model biomembrane (liposome).