Nanocrystal Preparation of Poorly Water-Soluble Drugs with Low Metal Contamination Using Optimized Bead-Milling Technology

Nanocrystal preparation using bead milling is an important technology to enhance the solubility of poorly water-soluble drugs. However, there are safety concerns regarding the metal contaminants generated during bead milling. We have previously reported optimized bead-milling parameters that could minimize metal contamination and demonstrated comparable performance to NanoCrystal®, a world-leading contamination-free technology. This study aimed to investigate the applicability of optimized milling parameters for preparing nanocrystals of several poorly water-soluble drugs exhibiting various physicochemical properties. Using our optimized bead-milling parameters, we found that all the tested drugs could be ground into nanosized particles within 360 min. Notably, fenofibrate, which has a low melting point, could be ground into nanosized particles owing to the low level of heat generated during bead milling. Additionally, the concentration of metal contaminants in all the drugs prepared using the optimized milling parameters were approximately ten to twentyfold lower than those prepared without the optimized parameters and were comparable to those prepared using polycarbonate beads, known to minimize metal contamination during bead milling. Our results provide insights into the development of drug nanocrystals with low metal contamination using bead milling.

Preparation of Fine-Drugs Layered Spherical Particles with Good Micromeritic and Dissolution Properties through Ultra Cryo-Milling and Mechanical Powder Processing

The particles of phenytoin (Phe), a poorly water-soluble model drug, were bead-milled alone or co-milled with a hydrophilic waxy additive using an ultra cryo-milling technique in liquid nitrogen (LN₂) to improve its dissolution properties. However, the micronized drug particles adhered and aggregated, resulting in poor handling in manufacturing processes such as blending or tableting. To improve the dissolution profile and powder properties of the drug simultaneously, the milled products were secondarily processed together with larger spherical particles by mechanical powder processing. These secondary products were composite particles with a core-shell structure, with fine drug particles adhered and deposited on the core, based on order mixing theory. As a core, three types/sizes of spherical pharmaceutical excipient particles were applied. The resultant composite particles produced much faster release profiles than just milled or co-milled mixtures. In addition, the composite particles showed good micromeritic properties depending on the size of the core particles. These results indicate that the ultra cryo-milling and subsequent dry composite mixing is a potential approach for developing drug particles with improved dissolution.

Cryo-milling with spherical crystalline cellulose beads: A contamination-free and safety conscious technology

Crystalline cellulose is a common inactive pharmaceutical additive. If this material can also be used to construct beads for the wet milling of pharmaceutical compounds, it could possibly address issues related to wear and contamination associated with zirconia and polyethylene beads. In this study, the model drug phenytoin was milled with spherical crystalline cellulose (SCC) in liquid nitrogen. The particle size of the milled product was found to be comparable to that obtained using zirconia beads, verifying the feasibility of using SCC beads for this purpose. Using a design of experiment approach, the bead amount, agitation speed, and milling time were all determined to have a significant effect on the milled particle size, giving a D50 value as low as 0.3 μm. No breakage of the SCC beads was observed during the milling process in durability tests under conditions that will degrade spherical D-mannitol beads, showing that this material exhibits sufficient durability. In addition, the variation in elastic modulus between beads was minimal. Because SCC is commercially available and easy to handle, the present wet milling technique is considered to have potential applications to the manufacture of pharmaceuticals on an industrial scale, as it shows sufficient milling capability and durability.

Cryo-milling using a spherical sugar: Contamination-free media milling technology

Milling beads experience wear upon repeated use. And milling beads made of material that is safe when ingested have not yet been developed. The present report describes the development and characteristics of spherical d-mannitol (SDM) beads, which would be safe when ingested. The model drug phenytoin was dispersed in liquid nitrogen along with SDM and the materials were agitated at high speed. The effects of the amount of beads, agitation speed, and milling time on phenytoin particle size, yield, and bead fractures were investigated using a central composite experimental design. The diameter of milled phenytoin particles decreased significantly as the amount of SDM beads and agitation speed increased. In contrast, no difference was found in the diameter with milling time. Although the fractured SDM ratio increased slightly at higher agitation speeds, the SDM was not broken and was durable enough for milling. This milling technique was applicable not only to phenytoin but also to other drug substances. Bead durability and applicability indicated that SDM can be used as wet milling beads that are considered safe for use if ingested.

Novel contamination-free wet milling technique using ice beads for poorly water-soluble compounds

The aim of this study is to establish a contamination-free milling method using ice beads instead of conventional hard beads such as metal or ceramics. Ice beads, which melt after the milling process to form water, would solve the contamination issue attributed to bead breakage or abrasion. The technique/method for preparing spherical ice beads of mono-dispersed size ranging from 150 to 3000 μm was newly developed. An oscillation beads milling apparatus was used for pulverization. In the initial stages of ice beads milling, the process is dry, but as time passes, the surface of the ice beads begins to melt, resulting in a transition to wet beads milling. It was found that ice beads are an effective milling media for beads milling, and that milling efficiency is strongly affected by the temperature of the coolant, with the peak efficiency occurring when the temperature was set to -2 °C and ice beads around 1500 μm in diameter were used. The spray-dried powder obtained from suspension after ice beads milling had dissolution improvement equivalent to that obtained after zirconia beads milling, resulting from its spontaneous rapid dispersion into nanosuspension.