An experimental method to characterize polymer film with various thicknesses, from μm down to nm, in liquid was proposed on the basis of optical reflectivity. Here, poly (methyl methacrylate) (PMMA) and methanol are used as a polymer and liquid, respectively. When a PMMA film is contacted with methanol, the film became thicker with increasing time. Assuming that the swelling behavior of the film can be expressed by Case II mechanism, diffusion coefficients of methanol into the PMMA film were successfully extracted. We observed two diffusion coefficients, fast and slow, assignable to the outermost layer and the remaining internal region including the substrate interface, respectively. Once the film thickness fell short of a threshold value, the diffusion coefficients decreased with decreasing thickness due to the contribution of the depressed segmental mobility at the substrate interface.
Properties of polymer materials originate from the large degree of freedom of a single polymer chain. The direct observation of the conformation of single polymer chains would provide much information for the fundamental understanding of the properties of polymers. Fluorescence imaging techniques are suitable for the selective observation of individual molecules embedded in a bulk medium; however, the spatial resolution of conventional optical microscopy is limited to ∼200 nm by the diffraction limit. This paper reviews the state-of-the-art optical imaging techniques that enable to obtain a fluorescence image with a nanometoric spatial resolution and describes its application for the direct imaging of the conformation of individual polymer chains. The conformation of poly(alkyl methacrylate) chains in thin films and micro-phase separation structures of a block copolymer is discussed.
Crystallization behavior of water sorbed into various non-water soluble polymers was examined by temperature-variable Fourier transform infrared spectroscopy (TV-FTIR) and differential scanning calorimetry (DSC). In general understanding of the sorbed water at low water content on the basis of DSC, all of the sorbed water has been considered to be non-freezing water. However, their TV-FTIR spectra clearly demonstrated the existence of the change in state including recrystallization of water by revapor deposition, which was vapor deposition (sublimation) during heating. Recrystallization of the sorbed water has been proposed to be devitrification and be a characteristic of biocompatible polymers. Recrystallization, however, was also observed in non-biocompatible polymers and recrystallization observed in the biocompatible polymer was not devitrification but revapor deposition.
We demonstrated the selection and characterization of polymer-binding peptides, and their application as surface modifiers. Peptides that bind specifically to polyetherimide (PEI) films were successfully identified from a phage-displayed peptide library. A chemically-synthesized peptide with the sequence of Thr-Gly-Ala-Asp-Leu-Asn-Thr (p1) showed high affinity toward PEI films (5.6×108 M-1). The peptide was biotinylated and immobilized onto the PEI films to function as a linker for the subsequent immobilization of streptavidin (SAv). We found that several factors could significantly affect the amount of SAv bound. Furthermore, we demonstrated that the SAv immobilized onto the PEI films via the biotinylated peptides was uniformly distributed, and thus was able to further immobilize probe DNA and to observe hybridization with complementary DNA. The present study offered new and significant insights into the modification of polymer film surfaces with specific binding peptides.
Asymmetric photochemistry provides us with new versatile routes to novel/strained chiral compounds. Recently, much effort has been devoted to the supramolecular photochirogenesis, exploiting the chiral environment of natural and synthetic hosts, such as cyclodextrin, modified zeolite, ds-DNA and protein. Photochirogenesis with biomolecule is particularly attractive and advantageous in view of the inherently chiral, finely-defined 3D structures. Serum albumins are the most abundant and well characterized water-soluble plasma proteins, which transport hydrophobic compounds. However, little is known about the supramolecular photochirogenesis with the protein used as chiral environment for reaction. We employed Bovine and Human Serum Albumin (BSA and HSA) as a chiral supramolecular host and 2-anthracenecarboxylate (AC) as a substrate. The photocyclodimerization of AC was performed in aqueous buffer solutions in the presence of BSA and HSA to give the [4+4] cyclodimers with high enantioselectivities of up to 90% ee.
Substrate-supported phospholipid bilayers (SPBs) are being studied as models of cellular membranes. One of the important features of SPBs is the possibility of generating micropatterned membranes on the substrate, which enables the creation of designed arrays of biological materials for various applications. Building an assay platform that is capable of producing an array of model lipid bilayers that maintain many of the characteristics found in cellular membranes such as fluidity and biocompatibility and that allow for the investigation of protein/ligand and protein/membrane interactions in a multiplexed fashion is the target of our studies. It is reported that a new process for creating phospholipid bilayer microarrays (PLBMAs) with a prepatterned substrate by the use of poly [2-methacryloyloxyethyl phosphorylcholine (MPC)] (PMPC) brushes. The PLBMAs were shown to resist nonspecific protein adsorption and have a minimal amount of cross-reactivity. PLBMAs should have potential applications in many fields such as biosensing, drug discovery, proteomics, and clinical diagnostics.
Alzheimer's disease (AD) is induced by the formation of fibrils of amyloidβprotein (Aβ). It is likely that the kinetics of fibril formation of Aβ and their morphology affected the cytotoxicity, because the senile plaque formed by Aβ fibrils is a hallmark of AD. Recently, it has been reported that the interface, such as a solid surface and a lipid membrane interface gave an impact on the fibril formation behavior of Aβ fibrils and their morphology. In this article, a dynamic property of interface to model the biomembrane in the previous reports was introduced. How the artificial biomembranes could affect the fibril formation of Aβ and its morphology was thereafter introduced. These findings would give the better understanding of both the formation mechanism of amyloid fibrils on biomembranes and the pathological mechanism of AD.
It is obvious that the biocompatible surface of materials is important for their cell biological and medical applications. Recently, a wide variety of external-stimuli responsive nanomaterials has been developed. Many of them can be next-generation therapeutic tools, while their metabolism and excretion remain to be addressed. To allow such nanomaterials exert their effects at low dose, therefore, augmentation and/or spatial control of them will also be needed. Here we show two types of coating materials based on synthetic and natural polymers to give biocompatible and functional surfaces by physisorption.