Exploring the Shape Influence on Melting Temperature, Enthalpy, and Solubility of Organic Drug Nanocrystals by a Thermodynamic Model

Firocoxib nanocrystals: Preparation, characterization, and pharmacokinetics in beagle dogs

This study aimed to develop drug nanocrystals to enhance the aqueous solubility of firocoxib, an anti-inflammatory drug used in the treatment of pain in the veterinary field. Different non-ionic stabilizers were evaluated to obtain firocoxib nanocrystals with reduced particle size, increased saturation solubility, and adequate storage stability. Optimization using the Box-Behnken design resulted in nanocrystals with a particle size of < 200 nm. In vitro dissolution testing demonstrated a 1.5-fold increase in drug dissolution compared to the pure drug. Safety assessment in Galleria mellonella L. larvae revealed any acute toxicity below a dosage of 50 times. In the pharmacokinetic study in beagle dogs, the nanocrystals improved Cmax in 2x compared to commercial product. Physicochemical stability was maintained over 12 months, with reduced variability in particle size and a PdI < 0.3. Additionally, an exploratory scale-up study successfully produced 3000 g of firocoxib nanocrystals with particle size < 400 nm. These findings suggest that firocoxib nanocrystals have the potential to enhance drug absorption and enabling faster symptom relief from inflammation and pain in dogs.

Tea Saponins: a Novel Stabilizer for Enhancing the Oral Bioavailability of Albendazole Nanocrystals

Albendazole serves as a broad-spectrum anthelmintic medication for treating hydatid cysts and neurocysticercosis. However, its therapeutic effectiveness is limited by poor solubility. Nanocrystals offer a promising technology to address this limitation by enhancing drug solubility. The objective of this study is to evaluate an effective stabilizer for creating an albendazole nanocrystal formulation to improve oral absorption. Among different surfactants and polymers examined, tea saponins were used as the stabilizer to develop a nanosuspension with the particle size of 180 nm through a wet grinding approach. The physical characteristics of the nanocrystals were assessed using SEM, DSC, and XRPD. The nanocrystals significantly enhanced solubility by 2.9-2602 fold in different media and showed significant enhancement in dissolution rate compared to albendazole crystals in both pH 1.0 and pH 6.8 medium. Everted gut sacs experiments demonstrated that the nanocrystals increased Papp by 3.60-fold in duodenum, 3.76-fold in jejunum, 3.71-fold in ileum, and 5.26-fold in colon, respectively. Furthermore, pharmacokinetic studies revealed that the nanocrystals significantly enhanced oral bioavailability, resulting in a 4.65-fold increase in plasma AUC0-t value of albendazole sulfoxide (the primary active metabolite of albendazole) compared to the albendazole group. The present data indicates that tea saponins are potential natural stabilizers for preparing nanocrystals with enhanced oral bioavailability for insoluble drugs.

Preparation and characterization of andrographolide nano-cocrystals using hummer acoustic resonance technology

Andrographolide (AG) is a diterpene lactone with significant anti-inflammatory and antitumor activities. However, the poor water solubility limits its clinical application. An andrographolide-salicylic acid (AG-SLA) nano-cocrystal delivery system was rapidly developed using hummer acoustic resonance (HAR) technology in this research. The formulation of the AG-SLA nano-cocrystal suspension and the process parameters for HAR technology were optimized in a high-throughput manner, with SDS-Tween 80 as the optimal composite stabilizer. Nano-cocrystal suspension of AG-SLA with an average particle size of 190 nm were successfully prepared, and then the optimal formulation were tenfold scaled up. Freeze-drying was adopted to solidify the nano-cocrystal and improve its stability. Various analytical techniques were used to characterize the particle size and solid state of the nano-cocrystals. The high-energy input from the HAR instrument induced partial amorphization of the nano-cocrystals, as confirmed by PXRD and DSC analyses. Saturation solubility experiments demonstrated that the solubility in pH 1.2 hydrochloric acid buffer and pH 6.8 phosphate buffer increased by 5.74 times and 6.82 times, respectively, compared to raw AG. In vitro dissolution tests indicated that the cumulative release over 120 min in pH 1.2 hydrochloric acid buffer and pH 6.8 phosphate buffer increased by 1.60 times and 1.88 times, respectively, compared to raw AG.

The Key Role of Wettability and Boundary Layer in Dissolution Rate Test

BACKGROUND/OBJECTIVES

The present work proposes a mathematical model able to describe the dissolution of poly-disperse drug spherical particles in a solution (Dissolution Rate Test-DRT). DRT is a pivotal test performed in the pharmaceutical field to qualitatively assess drug bioavailability.

METHODS

The proposed mathematical model relies on the key hallmarks of DRT, such as particle size distribution, solubility, wettability, hydrodynamic conditions in the dissolving liquid of finite dimensions, and possible re-crystallization during the dissolution process. The spherical shape of the drug particles was the only cue simplification applied. Two model drugs were considered to check model robustness: theophylline (both soluble and wettable) and praziquantel (both poorly soluble and wettable).

RESULTS

The DRT data analysis within the proposed model allows us to understand that for theophylline, the main resistance to dissolution is due to the boundary layer surrounding drug particles, whereas wettability plays a negligible role. Conversely, the effect of low wettability cannot be neglected for praziquantel. These results are validated by the determination of drug wettability performed while measuring the solid-liquid contact angle on four liquids with decreasing polarities. Moreover, the percentage of drug polarity was determined.

CONCLUSIONS

The proposed mathematical model confirms the importance of the different physical phenomena leading the dissolution of poly-disperse solid drug particles in a solution. Although a comprehensive mathematical model was proposed and applied, the DRT data of theophylline and praziquantel was successfully fitted by means of just two fitting parameters.

Dissolution of irregularly-shaped drug particles: mathematical modelling

The prediction of drug dissolution profiles is crucial for elucidating the pharmacokinetic behaviour of drugs and the bioavailability of dosage forms. In this work, we develop a mathematical model to describe the dissolution process of irregularly shaped particles. We use a complete dissolution model that accounts for both surface kinetics and convective diffusion. The mechanistic relationship between the mass transfer coefficient and the local curvature is derived from the fundamental physical laws governing these processes. Our model theoretically shows that the dissolution rate depends nonlinearly on the surface curvature. The subsequent recrystallization process in the bulk fluid is also considered. The main result of this work is its simplicity, since only two coupled nonlinear ordinary differential equations are needed to describe the dissolution process. Another remarkable advantage is the possibility to determine the model parameters using common independent techniques, so that the importance of the wettability of solids on the dissolution process can be evaluated. Finally, the proposed model demonstrated the importance of particle shape in describing the experimental dissolution data of theophylline monohydrate.

Nanocrystal-based gel of apremilast ameliorates imiquimod-induced psoriasis by suppressing inflammatory responses

Apremilast is 'difficult-to-deliver' in stratum corneum and viable layers (viable epidermis, dermis) owing to its modest lipophilicity and poor aqueous solubility, respectively. The objective of the present research was to develop apremilast nanocrystal-based gel for enhanced anti-psoriatic efficacy for the treatment of psoriasis. Nanosuspension was generated by wet media milling with a mean particle size of 200 nm. In-vivoefficacy of nanocrystal-based gels was evaluated in the imiquimod-induced psoriatic plaque model. Nanocrystal-based gel (1% and 3% w/w) improved phenotypic, histopathological features of psoriatic skin and attenuated splenic hypertrophy, psoriasis area severity scoring. Enzyme-linked immunosorbent assay was performed to evaluate levels of psoriatic biochemical markers indicating a significant decrease in the concentration of cytokines such as IL-23, IL-17A, IL-6 and TNF-α by nanocrystal-based gels (1% and 3% w/w) over disease induced group. Skin irritation study revealed that nanocrystal-based gel was significantly less irritating than the positive control. These results suggest that nanocrystal-based gel of apremilast can be an effective strategy for the management of psoriasis.

Effects of biochar pyrolysis temperature on thermal properties of polyethylene glycol/biochar composites as shape-stable biocomposite phase change materials

The characteristics of biochar are of great significance to its application in the field of phase change energy storage. The objective of this research was to explore the effects of pyrolysis temperature on the characteristics of a biochar matrix and further on the heat energy storage properties of the promising green biochar-supported shape-stable biocomposite PCMs (ss-BCPCMs). Corn straw biochars (CSBCs) obtained under different pyrolysis conditions were loaded with polyethylene glycol (PEG) by an ultrasound-assisted vacuum impregnation method. The micro-morphology, specific surface area, pore structure and surface properties of biochar have been characterized and analyzed by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) method and Fourier transform infrared spectroscopy (FTIR). The thermal properties (chemical stability, latent heat storage, thermal conductivity, thermal stability, and thermal insulation) of PEG/CSBC composites have been characterized by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and laser flash analysis (LFA). The study revealed that both pore structure and surface activity of biochar are key factors affecting the energy storage performance of biochar-based ss-BCPCMs. The obtained PEG/CSBC composite showed a high latent heat storage up to 100.2 J g⁻¹, good shape stability and leakage resistance, suggesting its high thermal storage stability that is beneficial for thermal energy storage applications. In addition, its excellent photothermal conversion efficiency (68.95%) provides application potential in photothermal energy storage.

The micropore and mesopore of biochar and the interaction between PEG and biochar surface effectively prevented the leakage of PEG and affected the crystallization and adsorption properties of PEG and the heat storage of composite PCMs.

Geometric Feature Extraction of Point Cloud of Chemical Reactor Based on Dynamic Graph Convolution Neural Network

Geometric features are an important factor for the classification of drugs and other transport objects in chemical reactors. The moving speed of drugs and other transport objects in chemical reactors is fast, and it is difficult to obtain their features by imaging and other methods. In order to avoid the mistaken and missed distribution of drugs and other objects, a method of extracting geometric features of the drug's point cloud in a chemical reactor based on a dynamic graph convolution neural network (DGCNN) is proposed. In this study, we first use MATLAB R2019a to add a random number of noise points in each point cloud file and label the point cloud. Second, k-nearest neighbor (KNN) is used to construct the adjacency relationship of all nodes, and the effect of DGCNN under different k values and the confusion matrix under the optimal k value are analyzed. Finally, we compare the effect of DGCNN with PointNet and PointNet++. The experimental results show that when k is 20, the accuracy, precision, recall, and F1 score of DGCNN are higher than those of other k values, while the training time is much shorter than that of k = 25, 30, and 35; in addition, the effect of DGCNN in extracting geometric features of the point cloud is better than that of PointNet and PointNet++. The results show that it is feasible to use DGCNN to analyze the geometric characteristics of drug point clouds in a chemical reactor. This study fills the gap of the end-to-end extraction method for a point cloud's corresponding geometric features without a data set. In addition, this study promotes the institutionalization, standardization, and intelligent design of safe production and management of drugs and other objects in the chemical reactor, and it has positive significance for the production cost and resource utilization of the whole pharmaceutical process. At the same time, it provides a new method for the intelligent processing of point cloud data.

Can the cavi-precipitation process be exploited to generate smaller size drug nanocrystal?

OBJECTIVE

Cavi-precipitation has the potential to generate drug nanocrystals very efficiently. Achieving smaller than 100 nm particle size for organic drug substances still remained a challenge. The objective of this study was to demonstrate if cavi-precipitation technology can be used to generate smaller than 100 nm drug nanocrystal particle.

SIGNIFICANCE

This study demonstrates that cavi-precipitation process can be used to generate drug nanocrystals of the model compound resveratrol (RVT) consists of crystallites of 30-50 nm size.

METHOD

RVT was dissolved in different organic solvents to prepare the solvent phase (S-phase). Several stabilizers were tested for the organic phase. A combination of SDS and PVP was used stabilizer system in the aqueous anti-solvent phase (AS-phase). The S-phase was added to the AS-phase inside the Emulsiflex C5 homogenizer. Nanosuspension was characterized by laser diffractometry (LD), photon correlation spectroscopy (PCS) and scanning electron microscopy (SEM). The solid state of the suspended particles was investigated by powder X-ray diffractometry (PXRD) and differential scanning calorimetry (DSC).

RESULTS

It was found that DMSO, alone or in combination with acetone in the S-Phase generated the smallest size RVT nanocrystals. The optimum solvent (S) antisolvent (AS) ratio (S:AS) was found to be 3.6:56.4 (v:v). Span 20 was identified as the best stabilizer for the organic phase at a ratio (w:w) of 1:3 (Span 20:RVT). The particles precipitated from different solvents were predominantly crystalline.

CONCLUSIONS

The best sample had a mean particle size (LD) of 167 nm [d(0.5)] which was composed of smaller crystallites having 30-50 nm size (SEM).

Novel nanocrystal-based formulations of apremilast for improved topical delivery

Nanocrystals can enhance skin penetration of drug by increased saturation solubility, dissolution rate and adhesion on the skin. Apremilast is 'difficult-to-deliver' in viable layers (epidermis, dermis) and stratum corneum (SC) owing to its poor aqueous solubility and modest lipophilicity, respectively. Apremilast is currently available as oral tablet formulation for the indication of psoriasis but its effectiveness is limited by systemic side effects. Therefore, the present study aimed to develop novel nanocrystal-based formulations of apremilast for improved topical delivery. Nanosuspension was prepared using wet media milling and exhibited a mean particle size of 200 nm. The saturation solubility of nanocrystals was improved by 2-fold than micronized apremilast and showed significant advantage during dissolution study. Nanosuspension and micronized apremilast was incorporated into gel and cream and characterized for rheological properties. Skin permeation and ex vivo dermatokinetic study of topical formulations were performed on pig ear skin at a dose of 1% w/w using Franz diffusion cells. Skin permeation studies indicated that non-detectable amount of apremilast permeated through pig ear skin during exposure of formulations. Nanosuspension showed 2.6- and 3.2-fold drug penetration in SC and viable layers, respectively, over microsuspension. Nanogel showed 2.7- and 2.4-fold drug penetration in SC and viable layers, respectively, over microgel. Nanocream showed 1.2- and 2.8-fold drug penetration in SC and viable layers, respectively, over microcream. Thus, nanocrystal-based formulations of apremilast aid in selective delivery into viable layers by crossing the SC barrier. This is of paramount importance in enhancing therapeutic effectiveness utilizing localized delivery and provides an alternative delivery approach for the treatment of psoriasis. Graphical abstract.

Amorphisation of Free Acid Ibuprofen and Other Profens in Mixtures with Nanocellulose: Dry Powder Formulation Strategy for Enhanced Solubility

The formulation of arylpropionic acid derivatives (profens), which are poorly soluble Biopharmaceutical Classification System (BCS) Type II drugs, has a strong impact on their therapeutic action. This article shows that heat-treated powder mixtures of free acid profens with high surface area Cladophora cellulose induces drug amorphization and results in enhanced solubility and bioavailability. Similar mixtures produced using conventional low surface area cellulose, i.e., microcrystalline cellulose, does not produce the same effect. The concept is thoroughly described and links the solid-state characterization data, such as differential scanning calorimetry, X-ray powder diffraction, and Fourier-transform infra-red spectroscopy, with in vitro dissolution in biorelevant media and in vivo pharmacokinetic analysis in rats. The concept is demonstrated for several substances from the profens group, including ibuprofen (main model drug), ketoprofen, flurbiprofen, and naproxen. The presented approach opens new ways to produce solid dosage forms of profen drugs in their free acidic form as alternatives to existing analogues, e.g., drug-salt conjugates or soft gel liquid capsules.

Understanding the Influence of Surface Solvation and Structure on Polymorph Stability: A Combined Mechanochemical and Theoretical Approach

We explore the effect of solvent concentration on the thermodynamic stability of two polymorphs of a 1:1 cocrystal of theophylline and benzamide subjected to ball-mill liquid assisted grinding (LAG) and we investigate how this can be related to surface solvent solvation phenomena. In this system, most stable bulk polymorph form II converts to metastable bulk polymorph form I upon neat grinding (NG), while form I can fully or partially transform into form II under LAG conditions, depending on the amount of solvent used. Careful and strict experimental procedures were designed to achieve polymorph equilibrium under ball-mill LAG conditions for 16 different solvents. This allowed us to determine 16 equilibrium polymorph concentration curves as a function of solvent concentration. Ex-situ powder X-ray diffraction (PXRD) was used to monitor the polymorph concentration and crystallite size. The surface site interactions point (SSIP) description of noncovalent interactions was used in conjunction with the SSIMPLE method for calculating solvation energies to determine which functional groups are more or less exposed on the polymorph crystal surfaces. Our results demonstrate that (i) ball-mill LAG equilibrium curves can be successfully achieved experimentally for a cocrystal system; (ii) the equilibrium curves vary from solvent to solvent in onset values and slopes, thus confirming the generality of the interconversion phenomenon that we interpret here in terms of cooperativity; (iii) the concentration required for a switch in polymorphic outcome is dependent on the nature of the solvent; (iv) the SSIP results indicate that the theophylline π-system face is more exposed on the surface of form I while the theophylline N-methyl groups are more exposed in form II; and (v) for some solvents, form II has a significantly smaller crystal size at equilibrium than form I in the investigated solvent concentration range. Therefore, the free energy of the 1:1 cocrystal of theophylline and benzamide polymorphs studied here must be affected by surface solvation under ball-mill LAG conditions.