Advances in Science and Technology Vol. 57

Abstract: We have developed polymer and gels with an autonomous self-oscillating function by utilizing the Belousov-Zhabotinsky (BZ) reaction. Under the coexistence of the substrates, the polymer undergoes spontaneous cyclic soluble-insoluble changes or swelling-deswelling changes (in the case of gel) without any on-off switching of external stimuli. By using microfabrication technique, ciliary motion actuator or self-walking gel have been demonstrated. Further, in order to realize nano-actuator, the linear polymer chain and the submicrometer-sized gel beads were prepared. By grafting the polymers or arraying the gel beads on the surface of substrates, we have attempted to design self-oscillating surface as nano-conveyer. For application to biomaterials, it is necessary to cause the self-oscillation under biological condition without using non-biorelated BZ substrates. So we attempted to introduce pH-control site and oxidant-supplying site into the polymer. By using the polymer, self-oscillation only in the existence of biorelated organic acid was actually achieved.

Abstract: The phospholipid molecule is one of the typical components of the cell membrane. In particular, the phosphorylcholine polar group is an electrically neutral head group. Arrangement of phospholipid polar groups and construct the surface, we applied 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers bearing a phosphorylcholine group in side chain, which was designed with the cell membrane as an inspiration. Versatile polymers comprising MPC could be synthesized, and their specific biofunctions were evaluated. Establishing an ultimate interface between biological circumstances and artificial materials, so-called biointerfaces, with multiple functions is important from the viewpoint of biomaterials science. Nonspecific protein adsorption is essential for achieving versatile biomedical applications. Simultaneously, bioconjugation and retention of its biofunction are crucial for a high-performance interface. In this article, we would like to introduce effectiveness of interface with highly biological functions composed of the MPC polymers for constructing nanobiodevices and nanomedicine.

Abstract: We have prepared a variety of biomolecule-responsive hydrogels by using biomolecular complexes as reversible crosslinking points. This paper describes two types of biomolecule-responsive hydrogels that undergo volume changes in response to target biomolecules, which were prepared using biomolecular complexes such as antigen-antibody complexes and saccharide-lectin complexes. One is a biomolecule-crosslinked hydrogel that can swell in response to a target biomolecule and the other is a biomolecule-imprinted hydrogel that can shrink. The antigen-responsive hydrogels as biomolecule-crosslinked hydrogels swelled in the presence of a target antigen due to the dissociation of antigen-antibody complexes that played a role as reversible crosslinking points. On the other hand, the tumor marker glycoprotein-responsive hydrogels as biomolecule-imprinted hydrogels shrank in response to a target glycoprotein due to the complex formation between ligands (lectin and antibody) and the target molecule (saccharide and peptide chains of glycoprotein). This paper focuses on synthetic strategy of the biomolecule-responsive hydrogels and their responsive behavior for target biomolecules.

Abstract: The success or failure of a bioactive ceramic implant material in the body depends on a complex interaction between a synthetic foreign body and the host. These interactions occur at many levels from the nano-structural level, where subtle changes in surface physio-chemistry substantially alters the nature of the biomaterial-host tissue interface, to the meso- or macrostructural level where dependence on porosity mediates bioactivity through its effect on nutrient transfer and scaffold mechanics. Thus the factors that control the biological response to implant materials are a complex combination of mechanical, physical and chemical attributes which when combined favorably lead to ‘bioactivity’ in a material, or more correctly a ‘bioactive’ response to the material. This is illustrated in the successful use of porous bioactive ceramic scaffolds as synthetic bone graft substitute materials, where micro and meso-porosity, bulk and surface chemistry are manipulated to provide a framework that is highly conducive to the process of bone regeneration, balancing bone apposition and remodeling. Moreover, we now have the opportunity to developing an understanding of the complex balance of forces at play during bone grafting through investigation of these biological responses.

Abstract: Hydroxyapatite (HAp) is a major inorganic component of human hard tissues, such as bones and teeth, and its content determines their microstructures and physical properties. Artificial HAp shows strong biocompatibility and bioactivity and thus it has found broad applications in tissue engineering for replacing damaged hard tissues. The artificial HAp, however, suffers from its intrinsic low mechanical properties, so to meet mechanical requirements, HAp can be incorporated with stiff mineral phases (mullite, zirconia, alumina). The performance and long-term survival of these biomedical devices are also dependent on the presence of bacteria surrounding the implants. In order to reduce the incidence of implant-associated infections, several treatments have been proposed, e.g. introduction of silver or fluoride in the HAp. The objective of this research is the sintering of composites based on calcium phosphate, mainly HAp supported on zirconia, for bone replacement with better microstructural features. In fact the use of zirconia can enhance the mechanical properties of bioceramics. Moreover the introduction of small amounts of silver, which should improve the antibacterial properties, will be taken into consideration since it is expected also to further toughen the whole structure.

Abstract: The chalcogenide CdSe quantum dots (QDs) were obtained by wet chemical synthesis route, using cadmium oxide and pure selenium as precursors, hexadecylamine (HDA), tetradecylphosphine oxide (TDPO) and tri-n-octylphosphine oxide (TOPO) as complexing agents in tri-n-butylphosphine (TBP) solvent in the reactor with an argon protection atmosphere. This study aims at manipulating the size of QDs for the potential in vivo medical applications. The CdSe nanoparticles were analyzed by particle size analyzer, photoluminescence (PL) spectroscopy, FE-SEM, TEM, and XPS. The desired particle size and photoluminescence response of CdSe QDs can be achieved by adjusting proper molar ratios of HDA/TOPO and CdO/Se, along with the synthesis temperature and reaction time. Our results show that the obtained CdSe quantum dots have the average particle size of 1~10 nm within a size variation of 1.5 nm. The resultant CdSe QDs provide stable PL responses as excited by light sources of 388~550 nm wavelengths.

Abstract: Potential application of Carbon Nanotubes as a drug delivery system is limited by their hydrophobity and their natural tendency to aggregate in the bundles. Dispersion and solubility of Singlewall Carbon Nanotubes (SWCNT) in Phosphate Buffered Saline (PBS) solution via non covalent and covalent interactions was investigated. Galactosyl-β1-Sphyngosine (glycolipid precursor of cerebrosides, structured with a hydrophobic chain, a hydrophilic head and an amine group between them) was used. Pristine SWCNTs were wrapped with Galactosyl-β1-Sphyngosine (Gal-Sphy), whereas the carboxylic groups of the functionalized CNTs were activated in order to interact with amine groups of Galactosylsphyngosine and render the coating stronger. Samples dispersion was characterized by optical absorption spectroscopy (OAS). The comparison and efficiency of the dispersion stability of the functionalized material in respect to the pristine SWCNTs will be presented. We exploited Raman Spectroscopy to evaluate relative purity of the samples, and the Infrared analysis to characterize the presence of the functional groups on the tubes surface. The morphology of the samples was studied using high resolution transmission electron microscopy (HR-TEM).

Abstract: Micro-Nano-Technologies main application field will be in life sciences for drug development, diagnostics and drug delivery. Typical examples are described for products already existing together with an outlook for new emerging products and applications. Existing market prognosis is discussed critically.