Nano- and micro-particulates firmly attach with the surface of various biological systems. In some chronic pulmonary
disease such as asbestosis and silicosis, causative particulates will induce chronic inflammatory disorder, followed by
poor prognosis diseases. However, nano- and micro-scale specific toxicity of silica particulates is not well examined
enough to recognize the risk of nano- and micro-particulates from the clinical aspect.
To clarify the effect of the size and structure of silica particulates on the cellular damage and the biological response,
we assessed the cytotoxicity of the various kinds of silica particles including amorphous and crystalline silica, in mouse
alveolar macrophage culture, focusing on the fibrotic and inflammatory response.
Our study showed that the cytotoxicity, which depends on the particle size and surface area, is correlated with their
inflammatory response. By contrast, production of TGF-β, which is one of the fibrotic agents in lung, by addition of
crystal silica was much higher than that of amorphous silica.
We conclude that fibrosis and inflammation are induced at different phases and that the size- and structure-differences
of silica particulates affect the both biological responses, caused by surface activity, radical species, and so on.
Nanoparticles, whose size is 1-100 nm, easily aggregate as their size becomes smaller. Therefore, it is difficult to
produce solution in which nanoparticles are dispersed. We have, as a way to disperse aggregated particles, for example, a
media-typed disperse machine. During the procedures, however, we have to deal with some complicating operations;
separation of the media from the solution, the defacement of the media into the solution, and so on. Furthermore, it is not
an effective method for particles whose size is less than 50 nm. We tried to find an easier and more effective method for
producing solution in which we re-disperse aggregated nanoparticles to still smaller particles. The aggregated particles
were put into a machine with a pinhole small needle valve, and they were re-dispersed by "sheering stress". The
estimation of re-dispersion was carried out by the measurement of their size distribution and surface z-average. With the
utility of the machine, the re-dispersions of aggregated particles were observed. Furthermore, the increase of the pressure
and of the velocity of the flow caused the decrease of particle size, which makes the surface area larger and therefore the
surface z-average larger. It become clear that it is possible to re-disperse aggregated nanoparticles by adding shearing
stress. We can regulate shearing stress by controlling the pressure and flow, and therefore we can control the
effectiveness and the yield.
Gene therapy is an attractive approach to supplement a deficient gene function. Although there has been some success
with specific gene delivery using various methods including viral vectors and liposomes, most of these methods have a
limited efficiency or also carry a risk for oncogenesis.
Fluorescent nanoparticles, such as nanocrystal quantum dots (QDs), have potential to be applied to molecular biology
and bioimaging, since some nanocrystals emit higher and longer lasting fluorescence than conventional organic probes
do. We herein report that quantum dots (QDs) conjugated with nuclear localizing signal peptides (NLSP) successfully
introduced the gene-fragments with promoter elements, which promoted the expression of the enhanced green
fluorescent protein (eGFP) gene in mammalian cells. The expression of eGFP protein was observed when the QD/geneconstruct
was added to the culture media. The gene-expression efficiency varied depending on multiple factors around
QDs, such as 1) the reading direction of gene fragments, 2) the quantity of gene fragments attached on the surface of
QD-constructs, 3) the surface electronic charges varied according to the structure of QD/gene-constructs, and 4) the
particle size of QD/gene complex varied according to the structure and amounts of gene fragments. Using this QD/geneconstruct
system, eGFP protein could be detected 28 days after the gene-introduction whereas the fluorescence of QDs
was disappeared. This system therefore provides another method for the intracellular delivery of gene-fragments without
using either viral vectors or specific liposomes.
These results suggest that inappropriate treatment and disposal of QDs may still have risks to the environmental
pollution including human health under certain conditions. Here we propose the further research for the immune and
physiological responses in not only immune cells but also other cells, in order to clear the effect of all other nanoscale
products as well as nanocrystal QDs.
Carbon group quantum dots (QDs) such as carbon, silicon and germanium, have potential for biomedical applications
such as bio-imaging markers and drug delivery systems and are expected to demonstrate several advantages over
conventional fluorescent QDs such as CdSe, especially in biocompatibility. We assessed biocompatibility of newly
manufactured silicon QDs (Si-QDs), by means of both MTT assay and LDH assay for HeLa cells in culture and thereby detected the cellular toxicity by administration of high concentration of Si-QD (>1000 μg/mL), while we detected the high toxicity by administration of over 100 μg/mL of CdSe-QDs. As a hypothesis for the cause of the cellular toxicity, we measured oxy-radical generation from the QDs by means of luminol reaction method. We detected generation of oxy-radicals from the Si-QDs and those were decreased by radical scavenger such as superoxide dismutase (SOD) and N-acetyl cysteine (NAC). We concluded that the Si-QD application to cultured cells in high concentration led cell membrane damage by oxy-radicals and combination usage with radical scavenger is one of the answers.