Biomedical subjects

Akira Mochizuki

Publications and source records attributed to Akira Mochizuki.

4 recordsLinked to original sources

PubMed2007

Relationship between blood compatibility and water structure--comparative study between 2-methoxyethylacrylate- and 2-methoxyethylmethacrylate-based random copolymers.

We have proposed that the excellent blood compatibility of poly(2-methoxyethylacrylate (MEA)) is caused by freezing bound water contained in it on the basis of results on platelet activation (Tanaka and Mochizuki, J Biomed Mater Res A 2004; 68:684-695). To clarify the applicability of this mechanism to other indexes for blood compatibility, the relationship between complement activation and water structure was investigated by using two copolymers, poly(MEA-2-hydroxyethylmethacrylate (HEMA)) and poly(2-methoxyethylmethacrylate (MEMA)-HEMA), where HEMA content was varied from 25 to 90 mol %. ESCA analysis revealed that the surface compositions of these copolymers (dry state) agreed with the compositions determined by (1)H NMR. However, analysis by water contact angle (wet state) showed that their surfaces were quite different. The contact angle of poly(MEMA-HEMA) depended on the monomer composition, whereas the angle of poly(MEA-HEMA) was close to that of polyHEMA regardless of the monomer composition. The effect of HEMA content in the copolymers on complement activation (production of C3a) was investigated in an in vitro test. The activation by poly(MEMA-HEMA) was enhanced according to the HEMA content, while the activation by poly(MEA-HEMA) with 0-40 mol % of HEMA was weak and did not depend on the HEMA content. These properties are discussed from the viewpoints of the water structure observed by DSC and the surface structure.

Calorimetry, Differential Scanning↗

PubMed2006

Study on blood compatibility with poly(2-methoxyethylacrylate)--relationship between surface structure, water structure, and platelet compatibility in 2-methoxyethylacrylate/2-hydroxyethylmethacrylate diblock copolymer.

Diblock copolymers composed of 2-methoxyethylacrylate (MEA) and 2-hydroxyethylmethacrylate (HEMA) were firstly prepared (the composition ratio = 90/10, 79/21, 66/34, and 48/52 mol/mol) by anion living polymerization. ESCA analysis of their surface structures (dry state) revealed that PMEA segment was segregated to the top surface in all of the polymers, whereas the results of contact angle of water (wet state) showed that the surfaces were covered with PHEMA segment. In vitro platelet adhesion test showed that these polymers had the excellent compatibility with platelet compared to PHEMA homopolymer. Water structure in the hydrated copolymers was investigated by DSC and freezing bound water was observed for all the polymers like PMEA homopolymer, whereas it was not found in PHEMA homopolymer. Further investigation of water structure based on the results of DSC and EWCMS (equilibrium water content by moisture sorption) suggested that freezing bound water existed in PHEMA segment in addition to PMEA segment. We have proposed that the water plays a key role in the appearance of good blood compatibility of the copolymer, according to our previous works (Tanaka et al. Biomacromolecules 2002;3:36-41, Tanaka et al. J Biomed Mater Res A 2004;68:684-695).

Biocompatible Materials↗

PubMed2004

Effect of water structure on blood compatibility--thermal analysis of water in poly(meth)acrylate.

The purpose of this study is to clarify the main factor causing excellent blood compatibility of poly(2-methoxyethyl acrylate)(PMEA) by the comparison between PMEA and seven PMEA analogous polymers. The polymers have a typical functional group as ester side chains such as methoxyethyl, hydroxyethyl, phenoxyethyl, and alkyl groups. The properties of the polymers relating to water were investigated in terms of contact angle, equilibrium water content (EWC), and thermal analysis by differential scanning calorimetry. The water in PMEA could be classified into three types: nonfreezing water, freezing bound water, and free water while the water in the analogous polymers was classified into just two types: free and nonfreezing waters, regardless of the chemical structure of the side chain. The surface property represented by the contact angle of water corresponded to the content of the bound water (nonfreezing water + freezing bound water). The platelet compatibility in vitro did not depend on the contents of these waters, or on the contact angle. On the basis of the results of this work and the previous work on the platelet compatibility of poly(MEA-co-HEMA) (Tanaka et al. Biomacromolecules 2002;3;36-41), the main factor causing the excellent compatibility of PMEA is discussed.

Biocompatible Materials↗

PubMedDate not supplied

Study of blood compatibility with poly(2-methoxyethyl acrylate). Relationship between water structure and platelet compatibility in poly(2-methoxyethylacrylate-co-2-hydroxyethylmethacrylate).

Previously, we reported that poly(2-methoxyethylacrylate) (PMEA) showed excellent blood compatibility and implied that the water structure in PMEA contributed to the blood compatibility. In this study, the relationship between the water structure and the blood compatibility is clarified by studying the influence of the monomer composition of poly(MEA-co-HEMA) on the water structure and the blood compatibility of the copolymers. The water in the polymer was classified into three types: free water, freezing bound water, and nonfreezing water. The polymers with 0-30 mol % of HEMA content had a significant amount of freezing bound water, and the amount decreases greatly when the composition of HEMA exceeded 30 mol %. On the other hand, the amount of other water increased simply with an increase of HEMA content. The evaluation of the platelet compatibility of poly(MEA-co-HEMA) revealed that the adhesion number and the morphological change of platelet on the copolymer surface were least when the HEMA content was 0-20 mol %. These two results strongly suggest that the freezing bound water relates to the platelet compatibility of the polymers.

Acrylates↗