Micronization and Agglomeration: Understanding the Impact of API Particle Properties on Dissolution and Permeability Using Solid State and Biopharmaceutical “Toolbox”

Bioavailability Improvement by Atomic Layer Coating: Fenofibrate A Case Study

Biopharmaceutical Classification Systems (BCS) class II drugs show poor solubility and high permeability in the body. Fenofibrate (FF) is a classic example of a BCS class II drug, used to treat high cholesterol and triglyceride (fat-like substances) levels in the blood. Atomic layer coating (ALC) is a surface engineering technology adapted from the semiconductor industry, where metal oxides are coated one atomic layer at a time over the active pharmaceutical ingredients (API) particles. ALC coating was proven to improve the processability, alter the hydrophilicity, improve the stability, and fine-tune the release of drugs. Herein, we report the intervention of ALC coating in enhancing the bioavailability of a poorly water-soluble drug (fenofibrate) in the animal model. The physical properties of uncoated fenofibrate were compared with those of zinc oxide-coated and silicon oxide-coated fenofibrate. Following the application of the coatings, the structural integrity (both chemical stability and solid-state stability) of the active pharmaceutical ingredient (API) remained uncompromised, as corroborated by 1H NMR and powder X-ray diffraction analyses. Notably, zinc oxide-coated fenofibrate exhibited favorable flow characteristics, whereas no discernible enhancement in flow behavior was observed for silicon oxide-coated fenofibrate. The results from contact angle measurements suggest that the silicon oxide-coated fenofibrate exhibits superior wetting behavior, as indicated by a contact angle nearing 0°. The application of ALC demonstrates an enhanced dissolution rate when compared to the uncoated active pharmaceutical ingredient (API) while leaving its equilibrium solubility unaffected. Coating the API with silicon oxide improves particle hydrophilicity and wetting properties, whereas zinc oxide coating aids in particle de-agglomeration, thereby enhancing their interaction with an aqueous medium. In vivo bioavailability studies conducted on rodents and larger animal (dog) models indicate a substantial increase in bioavailability (approximately 2 times) for the silicon oxide-coated API in comparison to the uncoated API, as determined by the area under the curve (AUC). Furthermore, the Cmax values for the silicon oxide-coated API also demonstrate a significant increase (approximately 3 times) over the uncoated API. Notably, an oral subacute toxicity study of ALC silicon-coated fenofibrate revealed no toxic effects attributable to the coating. This study underscores the potential of ALC in augmenting the bioavailability of BCS(II) drugs.

Application of shadowgraph imaging (SGI) particle characterisation data to interpret the impact of varying test conditions on powder dissolution and to develop an automated agglomeration identification method (AIM) in the USP flow-through apparatus

The aims of this work were 1) to explore the application of shadowgraph imaging (SGI) as a real time monitoring tool to characterize ibuprofen particle behaviour during dissolution testing under various conditions in the USP 4 flow-through apparatus and 2) to investigate the potential to develop an SGI-based automated agglomeration identification method (AIM) for real time agglomerate detection during dissolution testing. The effect of surfactant addition, changes in the drug mass and flow rate, the use of sieved and un-sieved powder fractions, and the use of different drug crystal habits were investigated. Videos at every sampling time point during dissolution were taken and analysed by SGI. The AIM was developed to characterize agglomerates based on two criteria - size and solidity. All detections were confirmed by manual video observation and a reference agglomerate data set. The method was validated under new dissolution conditions with un-sieved particles. Characterisation of particle dispersion behaviour by SGI enabled interpretation of the impact of dissolution test conditions. Higher numbers of early detections reflected greater dissolution rates with increased surfactant concentration, using sieved fraction or plate-shaped crystals, but was impacted by drug mass tested. An AIM was successfully developed and applied to detect agglomerates during dissolution, suggesting potential, with appropriate method development, for application in quality control.

Mesoporous Matrices as a Promising New Generation of Carriers for Multipolymorphic Active Pharmaceutical Ingredient Aripiprazole

The enhancement of the properties (i.e., poor solubility and low bioavailability) of currently available active pharmaceutical ingredients (APIs) is one of the major goals of modern pharmaceutical sciences. Among different strategies, a novel and innovative route to reach this milestone seems to be the application of nanotechnology, especially the incorporation of APIs into porous membranes composed of pores of nanometric size and made of nontoxic materials. Therefore, in this work, taking the antipsychotic API aripiprazole (APZ) infiltrated into various types of mesoporous matrices (anodic aluminum oxide, native, and silanized silica) characterized by similar pore diameters (d = 8-10 nm) as an example, we showed the advantage of incorporated systems in comparison to the bulk substance considering the crystallization kinetics, molecular dynamics, and physical stability. Calorimetric investigations supported by the temperature-dependent X-ray diffraction measurements revealed that in the bulk system the recrystallization of polymorph III, which next is converted to the mixture of forms IV and I, is visible, while in the case of confined samples polymorphic forms I and III of APZ are produced upon heating of the molten API with different rates. Importantly, the two-step crystallization observed in thermograms obtained for the API infiltrated into native silica templates may suggest crystal formation by the interfacial and core molecules. Furthermore, dielectric studies enabled us to conclude that there is no trace of crystallization of spatially restricted API during one month of storage at T = 298 K. Finally, we found that in contrast to the crystalline and amorphous bulk samples, all examined confined systems show a logarithmic increase in API dissolution over time (very close to a prolonged release effect) without any sign of precipitation. Our data demonstrated that mesoporous matrices appear to be interesting candidates as carriers for unstable amorphous APIs, like APZ. In addition to protecting them against crystallization, they can provide the desired prolonged release effect, which may increase the drug concentration in the blood (resulting in higher bioavailability). We believe that the "nanostructirization" in terms of the application of porous membranes as a novel generation of drug carriers might open unique perspectives in the further development of drugs characterized by prolonged release.

Surface engineering of chitosan nanosystems and the impact of functionalized groups on the permeability of model drug across intestinal tissue

Surface attributes of nanocarriers are crucial to determine their fate in the gastrointestinal (GI) tract. Herein, we have functionalized chitosan with biochemical moieties including rhamnolipid (RL), curcumin (Cur) and mannose (M). FTIR spectra of functionalized chitosan nanocarriers (FCNCs) demonstrated successful conjugation of M, Cur and RL. The functional moieties influenced the entrapment of model drug i.e., coumarin-6 (C6) in FCNCs with payload-hosting and non-leaching behavior i.e., >91 ± 2.5 % with negligible cumulative release of <2 % for 5 h in KREB, which was further verified in the simulated gastric and intestinal fluids. Consequently, substantial difference in the size and zeta potential was observed for FCNCs with different biochemical moieties. Scanning electron microscopy and atomic force microscopy of FCNCs displayed well-dispersed and spherical morphology. In addition, in vitro cytotoxicity results of FCNCs confirmed their hemocompatibility. In the ex-vivo rat intestinal models, FCNCs displayed a time-dependent-phenomenon in cellular-uptake and adherence. However, apparent-permeability-coefficient and flux values were in the order of C6-RL-FCNCs > C6-M-FCNCs > C6-Cur-FCNCs = C6-CNCs > Free-C6. Furthermore, the transepithelial electrical resistance revealed the FCNCs mediated recovery of membrane-integrity with reversible tight junctions opening. Thus, FCNCs have the potential to overcome the poor solubility and/or permeability issues of active pharmaceutical ingredients and transform the impact of functionalized-nanomedicines in the biomedical industry.

Studying the Intermolecular Interactions, Structural Dynamics, and Non-Equilibrium Kinetics of Cilnidipine Infiltrated into Alumina and Silica Pores

In the present study, the behavior of the calcium channel blocker cilnidipine (CLN) infiltrated into silica (SiO₂) and anodic aluminum oxide (AAO) porous membranes characterized by a similar pore size (d = 8 nm and d = 10 nm, respectively) as well as the bulk sample has been investigated using differential scanning calorimetry, broadband dielectric spectroscopy (BDS), and Fourier-transform infrared spectroscopy (FTIR) techniques. The obtained data suggested the existence of two sets of CLN molecules in both confined systems (core and interfacial). They also revealed the lack of substantial differences in inter- and intramolecular dynamics of nanospatially restricted samples independently of the applied porous membranes. Moreover, the annealing experiments (isothermal time-dependent measurements) performed on the confined CLN clearly indicated that the whole equilibration process under confinement is governed by structural relaxation. It was also found that the β_anneal parameters obtained from BDS and FTIR data upon equilibration of both confined samples are comparable (within 10%) to each other, while the equilibration constants are significantly different. This finding strongly emphasizes that there is a close connection between the inter- and intramolecular dynamics under nanospatial restriction.

Prediction of the Mechanical Deformation Properties of Organic Crystals Based upon their Crystallographic Structures: Case Studies of Pentaerythritol and Pentaerythritol Tetranitrate

PURPOSE

Development of a quantitative model and associated workflow for predicting the mechanical deformation properties (plastic deformation or cleavage fracture) of organic single crystals from their crystallographic structures using molecular and crystallographic modelling.

METHODS

Intermolecular synthons, hydrogen bonding, crystal morphology and surface chemistry are modelled using empirical force fields with the data integrated into the analysis of lattice deformation as computed using a statistical approach.

RESULTS

The approach developed comprises three main components. Firstly, the identification of the likely direction of deformation based on lattice unit cell geometry; secondly, the identification of likely lattice planes for deformation through the calculation of the strength and stereochemistry of interplanar intermolecular interactions, surface plane rugosity and surface energy; thirdly, identification of potential crystal planes for cleavage fracture by assessing intermolecular bonding anisotropy. Pentaerythritol is predicted to fracture by brittle cleavage on the {001} lattice planes by strong in-plane hydrogen-bond interactions in the <110>, whereas pentaerythritol tetranitrate is predicted to deform by plastic deformation through the slip system {110} < 001>, with both predictions being in excellent agreement with known experimental data.

CONCLUSION

A crystallographic framework and associated workflow for predicting the mechanical deformation of molecular crystals is developed through quantitative assessment of lattice energetics, crystal surface chemistry and crystal defects. The potential for the de novo prediction of the mechanical deformation of pharmaceutical materials using this approach is highlighted for its potential importance in the design of formulated drug products process as needed for manufacture by direct compression.

Comparison study of physicochemical and biopharmaceutics properties of hydrophobic drugs ground by two dry milling processes

1. AbstractThis study focuses on the dry milling of BCS (Biopharmaceutical Classification System) class II molecules. These molecules have a limited bioavailability because of their low aqueous solubility, poor water wettability and low dissolution rate. In order to improve these properties, indomethacin (IND) and niflumic acid (NIF) were milled using two different types of equipment: Pulverisette 0® and CryoMill®. Milled samples were characterized and compared to commercial molecules. IND shows a modified solid state, like surface crystallinity reduction and an increase in water vapor adsorption from to 2 up to 5-fold due to milling processes. The obtained solubility data resulted in an improvement in solubility up to 1.2-fold and an increase in initial dissolution kinetics: 2% of dissolved drug for original crystals against 25% for milled samples. For NIF no crystallinity reduction, no change of surface properties and no solubility improvement after milling were noticed. In addition, milled particles seemed more agglomerated resulting in no changes in dissolution rate compared to the original drug. IND solubility and dissolution enhancement can be attributed to the modification of surface area, drug crystallinity reduction and water sorption increase due to specific behaviour related to the drug crystal disorder induced by milling process.