Studies were undertaken on the precipitation of highly dispersed magnesium silicate. Solutions of sodium metasilicate and of magnesium salts [chloride, sulfate(VI) or nitrate(V)] were employed. The chemical reaction of silicate precipitation was corrected by supplementation of the system with diluted (5–15 wt%) solutions of sodium hydroxide. Optimum parameters of the precipitation process were established. The precipitated magnesium silicates were comprehensively examined. Their chemical composition and principal physicochemical properties were established, including bulk density, capacities to absorb water, dibutyl phthalate and paraffin oil as well as the sedimentation rate in linseed oil. Moreover, their morphology, microstructure and particle size distribution were studied, using scanning electron microscopy and dynamic light scattering technique. The obtained products manifested variable physicochemical properties. The presence of sodium hydroxide solution in the course of precipitation proved to significantly affect the quality of the obtained magnesium silicates.

We aimed to replicate a nano-scale mesh structure of a hydrogel by assembling silica nanoparticles densely in the nano-scale mesh structure. A pre-gel aqueous solution of N-isopropyl acrylamide (NIPAM) and sol-gel-derived silica sol prepared from tetraorthoethyl silicate (TEOS) were mixed to carry out the polymerization/cross-linking and silanol condensation. A homogeneous hybrid of poly-NIPAM gel and silica was successfully obtained. After removing the poly-NIPAM gel by calcination at 873 K in air, electron microscope observations revealed that the poly-NIPAM gel was replicated as network-or channel-like nanopores. The pore size distribution obtained by nitrogen adsorption/desorption at 77 K showed qualitative agreement with the above results of the direct observation. Therefore, the nano-scale mesh-like structure of the NIPAM hydrogel was replicated to the channel-like nanopores. As the weight ratio of NIPAM gel to silica moiety was increased, the average pore size increased to approximately 10 nm, indicating the partial nano-scale segregation of NIPAM chains when its fraction was enhanced. A retarded drying process was revealed to be advantageous for the formation of bulk assembly of the nanoparticles. By minimizing the drying rate at the saturated moist condition, an optically transparent assembly of the silica nanoparticles could be prepared at a porosity up to about 75%. The retarded drying process also affected the size of the resultant nanopores because of the presence of residual volatile species like solvent water.

A general approach for the quantitative and systematic characterization of fragmentation problems, which is based on the Weibull statistics, is presented. A model, initially developed for materials stressed under impact with respect to their breakage probability, has been successfully applied to the characterization of compressive comminution, fragmentation of nanoparticle agglomerates and destroying of adhesive bonds. The experimental results from the slow compression comminution and from the comminution by falling weight match for various materials and particle sizes exactly to the master curve deduced for impact comminution. However, the material parameters determined for compression comminution are not identical for one and the same material to that determined by impact comminution. This indicates that the two model parameters are not pure material characteristics as assumed from the impact experiments, but depend on the stress mechanism. The dependence of the fragmentation degree on the particle size and the energy input observed when impacting particles in the micrometer to millimeter range has been proven also for nanoparticle agglomerates. Furthermore, a model analogous to that for breakage has been deduced for the quantification of the failure of adhesive bonds.

Measuring the action of energy on matter is a complex problem, especially in the case of granular materials. For example, particle size reduction by grinding generally shows poor overall energetic yields and a significant challenge in this area is to accurately estimate the energy consumed, including that stored in the particles. Fine or ultra-fine grinding processes require a lot of energy, part of which becomes internal energy and can lead to mechanochemical reactions and useful products. We studied the appearance of free radicals during the grinding of α-lactose monohydrate by means of electron spin resonance (ESR). These radicals are the same as those induced by γ-radiation and comparison of ESR spectra intensities with those from ground products allows the determination of an ‘equivalent γ-irradiation dose’. This gives a novel concept for characterizing the action of mechanical energy on matter in fine grinding by using molecular probes. This is the first example of the investigation of mechanochemical energy during the fine grinding process.

Segregation indices were proposed to describe the intensity of segregation of multi-sized particle mixtures as a whole during filling a two-dimensional silo. They adequately represented the effects of the operational conditions on the segregation patterns obtained experimentally. As a result, the proposed segregation indices were found to increase with a lower feed rate and lower concentration of the smallest component, and exhibit a maximum with increasing numbers of components.

This paper reviews nanoparticles designed and prepared for cancer therapy and diagnosis, including inorganic nanoparticles, liposomes, lipid nanoparticles and polymeric nanoparticles. The nanoparticles are classified into (i) magnetite nanoparticles, (ii) other types of inorganic material-based nanoparticles that are generally used for imaging and hyperthermia treatment, and (iii) organic material-based nanoparticles for drug delivery, gene therapy and other applications. Their structures are analyzed, and the details of the components and the modes of bonding of the core, shell and surface are compared. In the final section, lipid nanoemulsion and chitosan nanoparticles developed by the authors for gadolinium neutron capture therapy of cancer are introduced; the design and preparation of these particles for the accumulation of active agents in tumors have been demonstrated. In all cases, nanoparticle targeting in the body is the most critical requirement for achieving excellent outcomes. This is common to chemotherapy, gene therapy, molecular imaging, etc. From a pharmaceutical viewpoint, it is emphasized that the macro biodistribution of active agents in the whole body has to be optimized and controlled; this is necessary in order to assure the clinical efficiency and safety of these agents before utilizing specific functions of biomolecules that have been discovered through molecular cell biology.

To examine the applicability of pressure swing granulation (PSG), a fluidized bed binderless granulation method, to the production of pharmaceutical granules, the effects of drug particle size and concentration on the properties of PSG granules were investigated. The hydrophobic model drug powder and the model excipient powder used in this work were jet-milled 2-ethoxybenzamide (ethenzamide) powder and jet-milled lactose powder, respectively. Spherical granules of 355-1410 μm diameter were obtained with a high yield. The strength of product granules increased with increasing ethenzamide concentration when fine ethenzamide particles (d_p,50 = 4.0 μm) were mixed with fine lactose (d_p,50 = 3.8 μm). However, when coarse ethenzamide particles (d_p,50 = 7.1 μm) were mixed with fine lactose powder (d_p,50 = 3.1 μm), the tensile strength remained relatively constant regardless of the drug concentration. The product granules were sufficiently strong to maintain their shape during storage and sufficiently weak to disintegrate under a small compaction force. The drug contents in the product PSG granules were in good agreement with the predetermined values showing the good content uniformity of PSG products.