Development of a novel ultra cryo-milling technique for a poorly water-soluble drug using dry ice beads and liquid nitrogen

Recent developments in the use of nanocrystals to improve bioavailability of APIs

Nanocrystals refer to materials with at least one dimension smaller than 100 nm, composing of atoms arranged in single crystals or polycrystals. Nanocrystals have significant research value as they offer unique advantages over conventional pharmaceutical formulations, such as high bioavailability, enhanced targeting selectivity and controlled release ability and are therefore suitable for the delivery of a wide range of drugs such as insoluble drugs, antitumor drugs and genetic drugs with broad application prospects. In recent years, research on nanocrystals has been progressively refined and new products have been launched or entered the clinical phase of studies. However, issues such as safety and stability still stand that need to be addressed for further development of nanocrystal formulations, and significant gaps do exist in research in various fields in this pharmaceutical arena. This paper presents a systematic overview of the advanced development of nanocrystals, ranging from the preparation approaches of nanocrystals with which the bioavailability of poorly water-soluble drugs is improved, critical properties of nanocrystals and associated characterization techniques, the recent development of nanocrystals with different administration routes, the advantages and associated limitations of nanocrystal formulations, the mechanisms of physical instability, and the enhanced dissolution performance, to the future perspectives, with a final view to shed more light on the future development of nanocrystals as a means of optimizing the bioavailability of drug candidates. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Hydrogen Bonding Principle-Based Molecular Design of a Polymer Excipient and Impacts on Hydrophobic Drug Properties: Molecular Simulation and Experiment

Although some commercial excipients for improving the solubility of highly crystalline drugs are widely used, they still cannot cover all types of hydrophobic drugs. In this regard, with phenytoin as the target drug, related molecular structures of polymer excipients were designed. The optimal repeating units of NiPAm and HEAm were screened out through quantum mechanical simulation and Monte Carlo simulation methods, and the copolymerization ratio was also determined. Using molecular dynamics simulation technology, it was confirmed that the dispersibility and intermolecular hydrogen bonds of phenytoin in the designed copolymer were better than those in the commercial PVP materials. At the same time, the designed copolymers and solid dispersions were also prepared during the experiment, and the improvement of their solubility was confirmed, which is in accordance with the simulation predictions. The new ideas and simulation technology may be used for drug modification and development.

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 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.

Changes in the Solid State of Nicergoline, a Poorly Soluble Drug, Under Different Grinding and Environmental Conditions: Effect on Polymorphism and Dissolution

Nicergoline native crystals (Form I) were subjected to different grinding methods for 15, 30, 45, and 60 min: Method A, grinding at 20°C under air atmosphere; Method B, grinding in presence of liquid nitrogen under air atmosphere; Method C, grinding at 20°C under nitrogen atmosphere; and Method D, grinding in presence of liquid nitrogen under nitrogen atmosphere. Scanning electron microscopy, differential scanning calorimetry, X-ray powder diffractometry, thermogravimetry, and infrared spectroscopy were used to follow changes in the particle size and in crystalline structures. Batches from Methods A and C underwent partial amorphization immediately after grinding; Form II was obtained by heating these partially amorphous forms or after spontaneous crystallization after 1 and 5 months storage. Method B promoted the hydration of nicergoline to a monohydrate form. Batch D was stable under grinding and neither amorphization nor hydration were observed. The best intrinsic dissolution rate was that of metastable Form II, followed by Form I, while the worst was that of the Method B monohydrate form. The slowest particle dissolution was observed for hydrated particles, because of the lowest IDR, while the most rapid was exhibited by batch D, because of the very small particle size.

Improved stability of solid dispersions of manidipine with polyethylene glycol 4000/copovidone blends: application of ternary phase diagram

CONTEXT

Manidipine (MDP) is generally used clinically as an antihypertensive agent; however, the bioavailability of orally administered MDP is limited due to their very low water solubility.

OBJECTIVE

The objectives of this research were, therefore, to increase the solubility of MDP by the formation of ternary solid dispersions (tSD) with polyethylene glycol 4000 (PEG4000) and copovidone and to improve their stability.

METHODS

Solid ternary phase diagram was constructed to find homogeneous solid dispersion region after melting and solidifying at low temperature with different quenching substances. The pulverized powder of solid dispersions was then determined, for their physicochemical properties, by differential scanning calorimetry, powder X-ray diffractometry, Fourier transform infrared (FTIR) spectroscopy and hot stage microscopy. The solubility and dissolution of MDP from the tSD were investigated. The physical stability of tSD was also determined under accelerated condition at 40 °C/75% relative humidity (RH) for 6 months.

RESULTS AND DISCUSSION

The results showed that MDP was molecularly dispersed in PEG4000 and copovidone when the tSD was created from homogeneous region of solid ternary phase diagram. FTIR results confirmed that strong hydrogen bonding was presented between MDP and copovidone, leading to a significant increase in the solubility and dissolution of MDP. After storage at accelerated condition (40 °C/75%RH) for 6 months, the tSD still showed a good appearance and high solubility.

CONCLUSION

The results of this study suggest that tSD prepared by melting has promising potential for oral administration and may be an efficacious approach for improving the therapeutic potential of MDP.

Cryo-crystallization under a partial anti-solvent environment as a facile technology for dry powder inhalation development

In this work, Isoniazid (INH) (an anti-TB drug) was converted to inhalable particles using cryo-crystallization under a partial anti-solvent environment.

Recent advancements in mechanical reduction methods: particulate systems

The screening of new active pharmaceutical ingredients (APIs) has become more streamlined and as a result the number of new drugs in the pipeline is steadily increasing. However, a major limiting factor of new API approval and market introduction is the low solubility associated with a large percentage of these new drugs. While many modification strategies have been studied to improve solubility such as salt formation and addition of cosolvents, most provide only marginal success and have severe disadvantages. One of the most successful methods to date is the mechanical reduction of drug particle size, inherently increasing the surface area of the particles and, as described by the Noyes-Whitney equation, the dissolution rate. Drug micronization has been the gold standard to achieve these improvements; however, the extremely low solubility of some new chemical entities is not significantly affected by size reduction in this range. A reduction in size to the nanometric scale is necessary. Bottom-up and top-down techniques are utilized to produce drug crystals in this size range; however, as discussed in this review, top-down approaches have provided greater enhancements in drug usability on the industrial scale. The six FDA approved products that all exploit top-down approaches confirm this. In this review, the advantages and disadvantages of both approaches will be discussed in addition to specific top-down techniques and the improvements they contribute to the pharmaceutical field.

A novel combined pretreatment of ball milling and microwave irradiation for enhancing enzymatic hydrolysis of microcrystalline cellulose

Microcrystalline cellulose (MCC) was performed as a mode substrate to investigate its potential ability of bioconversion in a novel combined pretreatment of ball milling (BM) and/or microwave irradiation (MWI). The variation of structure characteristics of MCC before/after pretreatment were investigated, including crystallinity index (CrI), size of crystal (S(C)), specific surface area (SSA) and degree of polymerization (DP). Their correlation with the rate of enzymatic hydrolysis was differentiated by an optimized equation which indicated the rate of hydrolysis was much more sensitive to CrI than SSA and DP. To achieve the same or higher glucose yield of BM for 3h and 6h, BM for 1h with MWI for 20min could save 54.8% and 77.40% energy consumption, respectively. Moreover, chemicals were not required in this process. It is concluded that the combination of BM and short time MWI is an environment-friendly, economical and effective approach to treat biomass.