Biological reactions of nano/micro materials are discussed. Nanomaterials are biointeractive in the sense that their size and existence themselves possess the nature to induce the bioreaction to cells and tissue. They are also bioreactive, since they induce the intrinsic functions of biological organism in a generalized sense of both merit (bioactive) and demerit (toxic) for human beings. The bilateral nature of the potentiality for both high functional performance (nanotechnology) and unintentionally occurring biohazard (nanotoxicology) is the essential properties of nano/micro materials.
Human lung receives many inhaled particles in daily life. In dentistry, rotary cutting instruments (e.g. diamond points and carbide burs) driven by water-cooled high-speed air-turbine and micro-motor headpieces produced aerosols, splatter and cut debris, all of which have the potentials to be breathed by dental professions and patients. The small aerosols and particles less than 0.5µm might enter deep inside the terminal bronchioles and alveoli of the lungs, at which the macrophage plays a scavenging role. If the particles are difficult to digest (e.g. crystalline silica), oxidative stress is imposed, causing the diseases of the lung and near-by organs (e.g. silicosis and mesothelioma). Microorganisms-contaminated aerosols cause the infectious diseases such as Mycobacterium tuberculosis, influenza viruses, hepatitis C virus and HIV. To prevent lung damage and infectious disease caused by aerosols and fine particles in dentistry, several countermeasures are recommended such as personal protection barriers as masks, gloves and safety eye glasses; the use of high volume evacuators; and the use of the air-room-cleaning system with high-efficiency particulate filters.
In recent years carbon nanotubes (CNTs) have attracted much interest in the fields of biomedical materials. The aim of this study was to investigate the influence of CNTs on cells by culturing them in direct contact with CNTs. First, human osteoblast-like cells, Saos-2 cells, were cultured on a CNT-coated culture dish and the cell morphology, viability, adhesion, and alkaline phosphatase (ALP) activity of these cells were compared to those cultured on a culture dish. Next, Saos-2 cells cultured on each dish were subcultured onto culture dish, and the cell morphology and the ALP activity were examined. The Saos-2 cells cultured on the CNTs showed a high viability that was similar to that of the cells on culture dish. Cell adhesion test showed strong adhesiveness of the cells to multi-walled carbon nanotubes (MWCNTs) and morphological observation revealed many filopodia extending to MWCNTs. After the subculture, this morphological change disappeared. These results suggest that the Saos-2 cells a have high adhesiveness toward CNTs, especially towards MWCNTs. Moreover, the morphological change in the cells cultured on MWCNTs implies that CNTs did not induce denaturation of the cells.
Histological investigations of the nanohydroxyapatite-collagen composite(nHAC) foil in tissue were carried out to evaluate its possible suitability as a BMP-2 carrier for regeneration of periodontal tissue. The nanohydroxyapatite-collagen composite and its thin foil could be successfully fabricated with the crosslinking agent of either 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride(EDC) or ascorbic acid / copper chloride (AA/CC). They were implanted into the subcutaneous tissue and tight muscle with and without BMP-2 for 1 and 2 weeks after surgery. nHAC was degraded and the inflammation in the surrounding area was decreased with time. nHAC(AA/CC) was degraded earlier and showed a better biocompatibility than nHAC(EDC). In the case of BMP-2 application, the different crosslinking agent showed an inverse effect. New bone formation was observed only in muscle for EDC and only in subcutaneous tissue for AA/CC. The Present results suggested that the nHAC is suitable as the carrier of BMP-2 with either the crosslinking agent of EDC or ascorbic acid / copper chloride, and the suitable crosslinking agent should be selected depending on desired conditions.
Tresyl chloride activation technique was new method for immobilizing proteins onto titanium surface. In the present study, fibronecitn was immobilized onto titanium surface using tresyl chloride-activation technique. Titanium surface was mirror polished, or pretreated with H2O2/NaOH aqueous solution for 30 min or 90 min after mirror polishing. Each titanium surface was covered with 2,2,2-trifluoroethanesulfonyl chloride (tresyl chloride) and was stored at 37°C for 2 days. The basic terminal OH groups of titanium were reacted with tresyl chloride. The tresylated titanium disk was then immersed into a fibronectin/PBS solution. H2O2/NaOH pretreated titanium surfaces had less degree of tresylated OH groups compared with mirror polished titanium, but the intensity of N1s peas which was derived from immobilized fibronectin was almost the same between mirror polished and H2O2/NaOH pretreated titanium. Finally, fibronectin could be easily immobilized onto each titanium surface using tresyl chloride-activation technique.
The wear behavior of a femoral head made of zirconia (ZrO2) against an acetabular cup made of ultrahigh-molecular-weight polyethylene (UHMWPE) was investigated using a hip joint simulator for five types of lubricants. Five types of lubricants were used: balanced salt solution (BSS), a BSS solution containing bovine serum albumin (A) and γ-globulin (G) (BSS+A+G), and a BSS solution containing 1.5 times the concentrations of A and G (BSS+1.5(A+G)), as well as two types of bovine sera (CS1 and CS2). The effect of the total protein concentration in the lubricant on the wear rate was assessed. The weight loss of the UHMWPE cup was measured. Weight loss increased with the test duration for all lubricants except for BSS. The lubricant that produced the highest wear rate (mg/106 cycles) calculated from the weight loss during the test, was BSS+1.5(A+G), followed by BSS+A+G. Little weight change of the UHMWPE cup was observed for BSS. The wear rate increased with the concentration of protein, irrespective of the protein species. During the experimental observation period, the wear rate decreased in the order CS1 > BSS+1.5(A+G) > CS2 > BSS+A+G > BSS ≅ 0. The comparison of quantitative measurements of individual particles in the lubricants showed that the morphology of each type of particle was dependent on the type of lubricant. Fibers and/or granules appeared in CS1 and CS2. In contrast, elongated fibers were mainly generated in BSS+A+G and BSS+1.5(A+G). These elongated particles formed by wear suggest that an adhesive mechanism, rather than the abrasive mechanism associated with asperities, was active. Our results suggest that the adhesive mechanism was active in lubricants containing proteins such as A and G.
Biomimetic macromolecules containing carboxyl and imidazole groups were synthesized. The complex of a zinc ion, a water molecule, and three imidazoles in a polymer is expected to act as an active center analogue of carbonic anhydrase, a hydration enzyme. The obtained polymer complex was applied to calcium carbonate formation. In this study, we investigated the role of both functional groups on the calcification reaction. The presence of a carboxyl group drastically enhanced the biomineralization, because it recognized and condensed the calcium ion at the first step of the calcification reaction. The obtained zinc-imidazole complex selectively induced the formation of vaterite, which is well-known to be a thermodynamically metastable polymorph of calcium carbonate. Interestingly, the results suggest that the active center analogue (zinc-imidazole complex) also stimulates introduction of the HCO3- ion to the calcium ion-recognition site.
The purpose of this study was to analyze the effects of lipopolysaccharide (LPS)-stimulation and IC50 nickel (Ni) (2+) ions on gene expressions of mouse macrophage-like cell line RAW264 cultured in 10% serum-supplemented α-MEM employing 32k DNA microarray. The results revealed that two stimulants (LPS and IC50 Ni (2+) ions) up-regulated genes of inflammatory mediators quite differently. LPS stimulation (4 h) caused RAW264 to highly up-regulate 29 inflammation-related genes more than 20-fold, many of which were expressed by NF-kappaB cascade (e.g. Marker symbols =Il1a, Il1b, TNF, Csf3, Cxcl2, Ccl4 and Ptgs2). On the other hand, IC50 Ni (2+) ions (24 h) rendered RAW264 to moderately up-regulate 28 genes more than 8-fold, which included genes for chemokines (e.g. Cxcl2 and Ccl4), vascular endothelial growth factor (Vegfa), prostaglandin synthase (Ptgs2), anti-oxidant (Hmox1) and genome-damage-repair-factor (e.g. Hist1h2bc). Dual stimulation of LPS and IC50 Ni (2+) ions (4 h and 24 h) caused RAW264 to express mixed-mode gene expressions caused by two stimulants. RT-PCR experiments confirmed that relative expressions of four inflammation-related (TNFα, IL-1β, i-NOS and IL-6) genes of RAW 264 caused by two stimulants were in relatively good accordance with those clarified by DNA microarray analyses.
We have observed biodistribution of tin-doped indium oxide nanoparticles with the size of ca. 10 nm. After the particles administered into mice through the tail vein, the organs were excited at several post-injection time then the specimens were subjected with X-ray scanning analytical microscope. The obtained fluorescent X-ray images of indium element clearly indicated that the injected nanoparticles reached and condensed temporally in the lung, liver, and spleen (especially, lung). The distributions among the organs were changed by the post-injection time. The amount of nanoparticles in organs rapidly decreases within 4 weeks.
To determine whether novel calcium particles could be used as scaffolding and vector delivery material, we examined the biological reaction to them in the body, in particular their antigenicity and bioabsorbable properties. Materials and methods: Three different kinds of porous calcium particles (10µm Ca3(PO4)2, 30µn;m Ca3(PO4)2 and CaCO3, 60µn;m CaCO3) and autogenous rat crushed thigh bone or heterogenous mouse crushed thigh bone were implanted under the dorsal skin of the rats. Following transplantation, tissues were resected at 2, 4, 6 and 8 weeks, and sections stained with HE were observed histopathologically. Results: The bioabsorption of and biological reactions to these novel porous calcium particles, including infiltration of lymphocytes, macrophages, and foreign body giant cells, were similar to those of autologous bone but different from those of heterologenous bone. The speed of bioabsorption of these 3 kinds of calcium particles was faster in order of particle size from the smaller to larger particles. Since porous calcium particles remained at least one month in the tissue, they might be useful as materials with scaffold and delivery functions.