Multi-faceted Characterization of Wet-milled Griseofulvin Nanosuspensions for Elucidation of Aggregation State and Stabilization Mechanisms

Do Mixtures of Beads with Different Sizes Improve Wet Stirred Media Milling of Drug Suspensions?

The impacts of bead sizes and bead mixtures on breakage kinetics, the number of milling cycles applied to prevent overheating, and power consumption during the nanomilling of drug (griseofulvin) suspensions were investigated from both an experimental and theoretical perspective. Narrowly sized zirconia beads with nominal sizes of 100, 200, and 400 µm and their half-and-half binary mixtures were used at 3000 and 4000 rpm with two bead loadings of 0.35 and 0.50. Particle size evolution was measured during the 3 h milling experiments using laser diffraction. An nth-order breakage model was fitted to the experimental median particle size evolution, and various microhydrodynamic parameters were calculated. In general, the beads and their mixtures with smaller median sizes achieved faster breakage. While the microhydrodynamic model explained the impacts of process parameters, it was limited in describing bead mixtures. For additional test runs performed, the kinetics model augmented with a decision tree model using process parameters outperformed that augmented with an elastic-net regression model using the microhydrodynamic parameters. The evaluation of the process merit scores suggests that the use of bead mixtures did not lead to notable process improvement; 100 µm beads generally outperformed bead mixtures and coarser beads in terms of fast breakage, low power consumption and heat generation, and low intermittent milling cycles.

An Enthalpy-Balance Model for Timewise Evolution of Temperature during Wet Stirred Media Milling of Drug Suspensions

PURPOSE

Nanosuspensions have been used for enhancing the bioavailability of poorly soluble drugs. This study explores the temperature evolution during their preparation in a wet stirred media mill using a coupled experimental-enthalpy balance approach.

METHODS

Milling was performed at three levels of stirrer speed, bead loading, and bead sizes. Temperatures were recorded over time, then simulated using an enthalpy balance model by fitting the fraction of power converted to heat ξ. Moreover, initial and final power, ξ, and temperature profiles at 5 different test runs were predicted by power-law (PL) and machine learning (ML) approaches.

RESULTS

Heat generation was higher at the higher stirrer speed and bead loading/size, which was explained by the higher power consumption. Despite its simplicity with a single fitting parameter ξ, the enthalpy balance model fitted the temperature evolution well with root mean squared error (RMSE) of 0.40-2.34°C. PL and ML approaches provided decent predictions of the temperature profiles in the test runs, with RMSE of 0.93-4.17 and 1.00-2.17°C, respectively.

CONCLUSIONS

We established the impact of milling parameters on heat generation-power and demonstrated the simulation-prediction capability of an enthalpy balance model when coupled to the PL-ML approaches.

Microparticulated Mefenamic Acid with High Dispersion Stability for Pediatric Dosage Form

Mefenamic acid (MFA), a water-insoluble drug, is used as a suspension in the medical field, but it requires shaking before using to disperse MFA content in the suspension. In previous studies, trials to prepare MFA suspension with high dispersion stability by atomizing MFA by the wet-milling method. However, HPC is used for atomizing MFA. Therefore, the optimum concentration and molecular weight for atomizing MFA have not been investigated. In this study, we investigated the optimum molecular weight and concentration of HPC for the micronization of MFA. As a result, MFA particles became fine particles by adding SDS, and the particle size was also smaller than that of HPC alone. In addition, the suspension with the highest dispersion stability can be obtained when a mixed solution of 1.0% HPC-SL and 0.12% SDS aqueous solution is used. Therefore, this study considers that the addition of SDS and 1.0% HPC-SL aqueous solution are optimal for improving the dispersion stability of the MFA suspension.

siRNA Targeting Mcl-1 Potentiates the Anticancer Activity of Andrographolide Nanosuspensions via Apoptosis in Breast Cancer Cells

Breast cancer is the second leading cause of cancer-related death in the US. However, recurrence is frequently found despite adjuvant therapy being available. Combination therapy with cytotoxic drugs and gene therapy is being developed to be a new promising cancer treatment strategy. Introducing substituted dithiocarbamate moieties at the C12 position of andrographolide (3nAG) could improve its anticancer selectivity in the MCF-7 breast cancer cell line. However, its hydrophobicity is one of its main drawbacks. This work successfully prepared 3nAG nanosuspension stabilized with the chitosan derivative NSC (3nAGN-NSC) to increase solubility and pharmacological effectiveness. siRNAs have emerged as a promising therapeutic alternative for interfering with particular mRNA. The 3nAGN-NSC had also induced Mcl-1 mRNA expression in MCF-7 human breast cancer cells at 8, 12, and 24 h. This indicates that, in addition to Mcl-1 silencing by siRNA (siMcl-1) in MCF-7 with substantial Mcl-1 reliance, rationally devised combination treatment may cause the death of cancer cells in breast cancer. The Fa-CI analysis showed that the combination of 3nAGN-NSC and siMcl-1 had a synergistic effect with a combination index (CI) value of 0.75 (CI < 1 indicating synergistic effects) at the fractional inhibition of Fa 0.7. The synergistic effect was validated by flow cytometry, with the induction of apoptosis as the mechanism of reduced cell viability. Our findings suggested the rational use of 3nAGN-NSC in combination with siMcl-1 to kill breast cancer cells.

In situ gelling nanosuspension as an advanced platform for fluticasone propionate nasal delivery

In this work we present the development of in situ gelling nanosuspension as advanced form for fluticasone propionate nasal delivery. Drug nanocrystals were prepared by wet milling technique. Incorporation of drug nanocrystals into polymeric in situ gelling system with pectin and sodium hyaluronate as constitutive polymers was fine-tuned attaining appropriate formulation surface tension, viscosity and gelling ability. Drug nanonisation improved the release profile and enhanced formulation mucoadhesive properties. QbD approach combining formulation and administration parameters resulted in optimised nasal deposition profile, with 51.8% of the dose deposited in the middle meatus, the critical region in the treatment of rhinosinusitis and nasal polyposis. Results obtained in biocompatibility and physico-chemical stability studies confirmed the leading formulation potential for safe and efficient nasal corticosteroid delivery.

Development of agomelatine nanocomposite formulations by wet media milling

Nanocrystal formulations of the BCS class II agomelatine, were developed by wet media milling. The most suitable stabilizer was identified and effects of process and formulation variables on the nanocrystal size and ζ-potential were evaluated employing a Box-Behnken experimental design. The optimized nanosuspensions were dried and subsequently evaluated for redispersibility and physicochemical properties. Computational simulation of solid state properties was applied to rationalize crystal fracture. It was found that low viscosity hydroxypropylcellulose with sodium dodecyl sulfate is the most suitable stabilizer. Stabilizer concentration exerts a statistically significant effect on particle size, which depends on the mill's rotation speed. The milling process induces a polymorphic transition to form II, which could affect size reduction kinetics. The solidified nanosuspensions' redispersibility is deteriorating progressively with storage time, with only minor differences between drying methods, retaining enhanced dissolution rate. Crystal lattice simulations suggest high mechanical anisotropy of form I crystals, which could be an additional reason for fast particle size reduction prior to the polymorphic transformation. Wet media milling, combined with a suitable drying method, can be an efficient technique for the production of stable nanocrystals of agomelatine. Particle informatics methods can enhance our understanding of the mechanisms responsible for agomelatine's nanocomminution.

Impact of Matrix Surface Area on Griseofulvin Release from Extrudates Prepared via Nanoextrusion

We aimed to examine the impact of milling of extrudates prepared via nanoextrusion and the resulting matrix surface area of the particles on griseofulvin (GF, a model poorly soluble drug) release during in vitro dissolution. Wet-milled GF nanosuspensions containing a polymer (Sol: Soluplus^®, Kol: Kolliphor^® P407, or HPC: Hydroxypropyl cellulose) and sodium dodecyl sulfate were mixed with additional polymer and dried in an extruder. The extrudates with 2% and 10% GF loading were milled–sieved into three size fractions. XRPD–SEM results show that nanoextrusion produced GF nanocomposites with Kol/HPC and an amorphous solid dispersion (ASD) with Sol. For 8.9 mg GF dose (non-supersaturating condition), the dissolution rate parameter was higher for extrudates with higher external specific surface area and those with 10% drug loading. It exhibited a monotonic increase with surface area of the ASD, whereas its increase tended to saturate above ~30 × 10⁻³ m²/cm³ for the nanocomposites. In general, the nanocomposites released GF faster than the ASD due to greater wettability and faster erosion imparted by Kol/HPC than by Sol. For 100 mg GF dose, the ASD outperformed the nanocomposites due to supersaturation and only 10% GF ASD with 190 × 10⁻³ m²/cm³ surface area achieved immediate release (80% release within 30 min). Hence, this study suggests that ASD extrudates entail fine milling yielding > ~200 × 10⁻³ m²/cm³ for rapid drug release, whereas only a coarse milling yielding ~30 × 10⁻³ m²/cm³ may enable nanocomposites to release low-dose drugs rapidly.

Use of Bead Mixtures as a Novel Process Optimization Approach to Nanomilling of Drug Suspensions

PURPOSE

We aimed to evaluate the feasibility of cross-linked polystyrene (CPS)-yttrium-stabilized zirconia (YSZ) bead mixtures as a novel optimization approach for fast, effective production of drug nanosuspensions during wet stirred media milling (WSMM).

METHODS

Aqueous suspensions of 10% fenofibrate (FNB, drug), 7.5% HPC-L, and 0.05% SDS were wet-milled at 3000-4000 rpm and 35%-50% volumetric loading of CPS:YSZ bead mixtures (CPS:YSZ 0:1-1:0 v:v). Laser diffraction, SEM, viscometry, DSC, and XRPD were used for characterization. An n^th-order model described the breakage kinetics, while a microhydrodynamic model allowed us to gain insights into the impact of bead materials.

RESULTS

CPS beads achieved the lowest specific power consumption, whereas YSZ beads led to the fastest breakage. Breakage followed second-order kinetics. Optimum conditions were identified as 3000 rpm and 50% loading of 0.5:0.5 v/v CPS:YSZ mixture from energy-cycle time-heat dissipation perspectives. The microhydrodynamic model suggests that YSZ beads experienced more energetic/forceful collisions with smaller contact area as compared with CPS beads owing to the higher density-elastic modulus of the former.

CONCLUSIONS

We demonstrated the feasibility of CPS-YSZ bead mixtures and rationalized its optimal use in WSMM through their modulation of breakage kinetics, energy utilization, and heat dissipation.

Testing a Benchtop Wet-Milling Method for Preparing Nanoparticles and Suspensions as Hospital Formulations

In clinical practice, for elderly or pediatric patients who have difficulty swallowing, solid dosage forms such as tablets or capsules are crushed or unsealed, prepared as powder forms, and often administered as suspensions. However, because their dispersibility is poor, aggregation or precipitation occurs readily. Once precipitation and deposition happen, redispersion is difficult, which can limit patient and caretaker drug adherence. In this study, we attempted to prepare nanoparticles as a hospital formulation by a benchtop wet-milling method to obtain a suspension with high dispersibility. This is the first study to apply the wet-milling method to prepare the hospital formulation. We chose cefditoren pivoxil (CDTR-PI) as an experimental active pharmaceutical ingredient. CDTR-PI crystals were physically mixed with various water-soluble polymers such as polyvinylpyrrolidone, polyethylene oxide, hydroxypropyl cellulose, or hypromellose and wet-milled with a surface-active agent (sodium lauryl sulfate) under different conditions. The mean particle diameter of most of the samples was less than 200 nm. In FTIR spectra of ground samples, peak shifts suggesting inter- or intramolecular interactions between CDTR-PI and the other additive agents were not observed. Besides, the nanoparticle suspension had favorable dispersibility, as determined using a dispersion stability analyzer. Providing a suspension with high dispersibility makes dispense with the resuspension, the patient’s medication adherence would improve. These results show that suspended liquid formulations of active pharmaceutical ingredients could be obtained by the simple wet-milling method as hospital formulations.

An efficient organosilane-modified polycarboxylate dispersant with excellent dispersing performance and superior wettability for tebuconazole suspension concentrate

The dispersion stability and wettability of suspension concentrates are beneficial for improvement of the utilization rate of pesticides.

Mechanistic Modeling of Wet Stirred Media Milling for Production of Drug Nanosuspensions

Drug nanocrystals have been used for a wide range of drug delivery platforms in the pharmaceutical industry, especially for bioavailability enhancement of poorly water-soluble drugs. Wet stirred media milling (WSMM) is the most widely used process for producing dense, stable suspensions of drug nanoparticles, also referred to as nanosuspensions. Despite a plethora of review papers on the production and applications of drug nanosuspensions, modeling of WSMM has not been thoroughly covered in any review paper before. The aim of this review paper is to briefly expose the pharmaceutical scientists and engineers to various modeling approaches, mostly mechanistic, including computational fluid dynamics (CFD), discrete element method (DEM), population balance modeling (PBM), coupled methods, the stress intensity-number model (SI-SN model), and the microhydrodynamic (MHD) model with a main focus on the MHD model for studying the WSMM process. A total of 71 studies, 30 on drugs and 41 on other materials, were reviewed. Analysis of the pharmaceutics literature reveals that WSMM modeling is largely based on empirical, statistically based modeling approaches, and mechanistic modeling could help pharmaceutical engineers develop a fundamental process understanding. After a review of the salient features and various pros-cons of each modeling approach, recent advances in microhydrodynamic modeling and process insights gained therefrom were highlighted. The SI-SN and MHD models were analyzed and critiqued objectively. Finally, the review points out potential research directions such as more mechanistic and accurate CFD-DEM-PBM simulations and the coupling of the MHD-PBM models with the CFD.

Nanosuspensions of a poorly soluble investigational molecule ODM-106: Impact of milling bead diameter and stabilizer concentration

Aqueous solubility of a drug substance is an important attribute affecting oral bioavailability. Nanonization, particle size reduction to submicron level, is an elegant approach to improve drug solubility and dissolution by increasing the surface energy, which in turn necessitates the use of stabilizers. The purpose of this study was to develop a nanosuspension of a practically water-insoluble investigational molecule by nanomilling approach using wet media milling. A variety of polymeric and surface active excipients were tested for their wettability. A combination of hydroxypropyl methylcellulose and sodium lauryl sulfate (SLS) were selected as stabilizers on the bases of compatibility studies and efficient wettability behaviour in contact angle measurements (≈80˚). A factorial design set-up was used to study the effect of milling bead diameter and stabilizer concentration on the efficiency of particle size reduction. Nanonization outcome was different when milling beads of 0.5 mm and 1 mm diameter were used at different concentrations of the stabilizers, which demonstrated the complex nature of the whole system. Storage of the nanosuspensions under different temperature conditions resulted only in minor changes of the particle size fractions.

Formulation aspects of intravenous nanosuspensions

Intravenous (IV) route is preferred for rapid onset of action, avoiding first pass metabolism and achieving site specific delivery. Development of IV formulations for poorly water soluble drugs poses significant challenges. Formulation approaches like salt formation, co-solvents, surfactants and inclusion complexation using cyclodextrins are used for solubilisation. However, these approaches are not applicable universally and have limitations in extent of solubilisation, hypersensitivity, toxicity and application to only specific type of molecules. IV nanosuspension have been attracting attention as a viable strategy for development of IV formulations of poorly water-soluble drugs. Nanosuspension consists of nanocrystals of poorly water soluble drug suspended in aqueous media and stabilized using minimal concentration of stabilizers. Recent years have witnessed their potential in formulations for toxicological studies and clinical trials. However various challenges are associated with the translational development of IV nanosuspensions. Therefore, the objective of the current review is to provide a holistic view of formulation development and desired properties of IV nanosuspensions. It will also focus on advancements in characterization tools, manufacturing techniques and post-production processing. Challenges associated with translational development and regulatory aspects of IV nanosuspension will be addressed. Additionally, their role in preclinical evaluation and special applications like targeting will also be discussed with the help of case studies. The applications of IV nanosuspensions shall expand as their applications move from preclinical phase to commercialization.

Study on the stabilization mechanisms of wet-milled cepharanthine nanosuspensions using systematical characterization

Objectives: Stability issues are inevitable problems that are encountered in nanosuspension (NS) technology developments and in the industrial application of pharmaceuticals. This study aims to assess the stability of wet-milled cepharanthine NSs and elucidate the stabilization mechanisms of different stabilizers.Methods: The aggregation state was examined via scanning electron microscopy, laser diffraction, and rheometry. The zeta potential, stabilizer adsorption, surface tension, and drug-stabilizer interactions were employed to elucidate the stabilization mechanisms.Results: The results suggest that croscarmellose sodium (CCS), D-α-tocopherol polyethylene glycol 1000 succinate (TPGS), or polyvinyl pyrrolidone VA64 (PVP VA64) alone was able to prevent nanoparticle aggregation for at least 30 days. Attempts to evaluate the stability mechanisms of different stabilization systems revealed that CCS improved the steric-kinetic stabilization of the NSs, attributed to its high viscosity, swelling capacity, and physical barrier effects. In contrast, the excellent physical stability of TPGS systems was mainly due to the reduced surface tension and higher crystallinity. PVP VA64 can adsorb onto the surfaces of nanoparticles and stabilize the NS via steric forces.Conclusion: This study demonstrated the complex effects of CCS, TPGS, and PVP VA64 on cepharanthine NS stability and presented an approach for the rational design of stable NSs.

Preparation and in vitro-in vivo evaluation of intestinal retention pellets of Berberine chloride to enhance hypoglycemic and lipid-lowing efficacy

Berberine chloride (BBR) is a pharmacokinetic profile of drug with poor bioavailability but good therapeutic efficacy, which is closely related to the discovery of BBR intestinal target. The major aim of this paper is to develop BBR intestinal retention type sustained-release pellets and evaluate their in vivo and in vitro behaviors base on the aspect of local action on intestinal tract. Here, wet milling technology is used to improve dissolution and dissolution rate of BBR by decreasing the particle size and increasing the wettability. The pellets are prepared by liquid layer deposition technology, and then the core pellets are coated with Eudragit^® L30D-55 and Eudragit^® NE30D aqueous dispersion. The prepared pellets show high drug loading capacity, and the drug loading up to 93%. Meanwhile, it possesses significant sustained drug release effect in purified water which is expected to improve the pharmacokinetic behavior of BBR. The pharmacokinetics results demonstrate that the half-life of BBR was increased significantly from 24 h to 36 h and the inter- and intra-subject variability are decreased compared to commercial BBR tablets. The retention test results indicate that the pellet size and Eudragit^® NE30D plays an important role in retention time of the pellet, and it is found that the pellets with small particle size and high Eudragit^® NE30D coating content can stay longer in the intestine than the pellets with large particle size. All in all, BBR intestinal retention type pellets are prepared successfully in this study, and the pellets show satisfactory in vivo and in vitro behaviors.

Bioavailability Enhancement of Poorly Water-Soluble Drugs via Nanocomposites: Formulation⁻Processing Aspects and Challenges

Drug nanoparticles embedded in a dispersant matrix as a secondary phase, i.e., drug-laden nanocomposites, offer a versatile delivery platform for enhancing the dissolution rate and bioavailability of poorly water-soluble drugs. Drug nanoparticles are prepared by top-down, bottom-up, or combinative approaches in the form of nanosuspensions, which are subsequently dried to prepare drug-laden nanocomposites. In this comprehensive review paper, the term &ldquo;nanocomposites&rdquo; is used in a broad context to cover drug nanoparticle-laden intermediate products in the form of powders, cakes, and extrudates, which can be incorporated into final oral solid dosages via standard pharmaceutical unit operations, as well as drug nanoparticle-laden strip films. The objective of this paper is to review studies from 2012⁻2017 in the field of drug-laden nanocomposites. After a brief overview of the various approaches used for preparing drug nanoparticles, the review covers drying processes and dispersant formulations used for the production of drug-laden nanocomposites, as well as various characterization methods including quiescent and agitated redispersion tests. Traditional dispersants such as soluble polymers, surfactants, other water-soluble dispersants, and water-insoluble dispersants, as well as novel dispersants such as wet-milled superdisintegrants, are covered. They exhibit various functionalities such as drug nanoparticle stabilization, mitigation of aggregation, formation of nanocomposite matrix⁻film, wettability enhancement, and matrix erosion/disintegration. Major challenges such as nanoparticle aggregation and poor redispersibility that cause inferior dissolution performance of the drug-laden nanocomposites are highlighted. Literature data are analyzed in terms of usage frequency of various drying processes and dispersant classes. We provide some engineering considerations in comparing drying processes, which could account for some of the diverging trends in academia vs. industrial practice. Overall, this review provides rationale and guidance for drying process selection and robust nanocomposite formulation development, with insights into the roles of various classes of dispersants.