Impact of Formulation Properties and Process Parameters on the Dispensing and Depositioning of Drug Nanosuspensions Using Micro-Valve Technology

Effect of gravity on the spreading of a droplet deposited by liquid needle deposition technique

This study represents an experimental investigation, complemented with a mathematical model, to decipher the effect of gravity on the spreading dynamics of a water droplet. For the theoretical discussion, an overall energy balance approach is adopted to explain the droplet spreading under both microgravity (μg) and terrestrial gravity condition. Besides explaining the mechanism of the droplet spreading under microgravity condition achieved during the parabolic flight, a technique with a detailed experimental set-up has also been developed for the successful deposition of droplet. A rational understanding is formulated through experimental investigation and theoretical analysis, which allows us to distinguish the transient variation of the spreading of a droplet, between microgravity and terrestrial gravity condition. The spreading of the droplet is predicted by the non-linear overall energy balance equation, which accounts for the operating parameters in the form of non-dimensional groups like Reynolds number ([Formula: see text]), Weber number (We) and Bond number (Bo). To distinctly identify the difference in the drop spreading at terrestrial and microgravity conditions, the Bo with transient gravitational field obtained through the on-board accelerometer is considered. The obtained theoretical results are further corroborated by experimental results which are obtained from the parabolic flight.

Modified Release Kinetics in Dual Filament 3D Printed Individualized Oral Dosage Forms

On demand production of totally customizable combinative preparations is a central goal of a patient-centric pharmaceutical supply chain. Additive manufacturing techniques like fused deposition modeling (FDM) could be key technologies towards such individualized dosage forms. As so far only a limited number of studies on 3D printed combinative preparations applying FDM have been reported, a core-shell dosage form was the focus of the present study. Dosage forms with an initial and a sustained release part with theophylline as model API were successfully produced applying a dual nozzle FDM 3D printer. Investigations identified microstructural defects at the interface between the two formulations by means of µCT analysis. Dissolution testing proved the achievement of the intended release profile. In combination with additionally characterized release profile of single material prints of different shapes, the combinative release profiles could be predicted by developing model equations and taking into account the geometric composition. As these model approaches can accordingly facilitate the prediction of API release from 3D printed combinative preparations with only data from single material release. This is a first step towards a truly individualized and reliable patient-centric pharmaceutical supply via 3D printing.

The effect of dynamic wetting pressure on contact angle measurements

HYPOTHESIS

The drop deposition technique can impact contact angle measurements. We hypothesized that the drop pinch-off, during the traditionally used pendant drop technique, significantly alters the static contact angle. The capillary waves and dynamic wetting pressure generated during the pendant drop deposition are the source for forced spreading, which can be circumvented by alternative liquid-needle drop deposition techniques.

EXPERIMENTS

To compare the role of drop pinch-off and resultant dynamic wetting pressure, we meticulously observed and quantified the entire drop deposition process using high speed imaging until the drop attains the static contact angle in both cases, namely pendant drop and liquid needle deposition technique. Conventionally used standard substrates are compared using both techniques and further compared using literature data. The capillary waves and corresponding drop shape variations are analysed for quantifying the dynamic wetting pressure by measuring drop base diameter, contact angle and centre of mass.

FINDINGS

We compared three parameters - drop pinch-off, spreading behaviour and respective static contact angles along with the resultant dynamic wetting pressure for both the techniques, i.e., pendant drop and liquid-needle. For the pendant drop technique we observed a pronounced drop volume dependency of these parameters even though the corresponding Bond numbers are less than unity. In contrast, for the liquid needle there is no such dependency. With a theoretical argument corroborating experimental observations, this work highlights the importance of a well controlled drop deposition, with a minimum wetting pressure, in order to guarantee contact angle data that is independent of drop deposition effects, thereby only reflecting the substrate properties.

Drop-on-demand printing of personalised orodispersible films fabricated by precision micro-dispensing

Personalised orodispersible films (ODFs) manufactured at the point of care offer the possibility of adapting the dosing requirements for individual patients. Inkjet printing was extensively explored as a tool to produce personalised ODFs, but it is extensively limited to dispensing liquid with low viscosity and the interaction between ink and edible substrate complicates the fabrication process. In this study, we evaluated the feasibility of using a micro-dispensing (MD) jet system capable of accurately dispensing viscous liquid to fabricate substrate-free ODFs on-demand. The model inks containing hydroxypropyl methylcellulose (HPMC) and paracetamol were used to prepare personalised ODFs by expanding the film area. Cast films were used as the control sample to benchmark the mechanical properties, disintegration time, and dosing accuracy of MD printed ODFs. Both the cast and printed films showed smooth surface morphology without any bubbles. No significant difference was found in the disintegration time of the MD printed films compared to the cast films. High precision in dosing by MD printing was achieved. The dose of paracetamol had a linear correlation with the dimension of the printed films (R² = 0.995). The results provide clear evidence of the potential of MD printing to fabricate ODFs and the knowledge foundation of advancing MD printing to a point-of-care small-batch manufacturing technology of personalised ODFs.

A dynamical overview of droplets in the transmission of respiratory infectious diseases

The outbreak of the coronavirus disease has drawn public attention to the transmission of infectious pathogens, and as major carriers of those pathogens, respiratory droplets play an important role in the process of transmission. This Review describes respiratory droplets from a physical and mechanical perspective, especially their correlation with the transmission of infectious pathogens. It covers the important aspects of (i) the generation and expulsion of droplets during respiratory activities, (ii) the transport and evolution of respiratory droplets in the ambient environment, and (iii) the inhalation and deposition of droplets in the human respiratory tract. State-of-the-art experimental, computational, and theoretical models and results are presented, and the corresponding knowledge gaps are identified. This Review stresses the multidisciplinary nature of its subject and appeals for collaboration among different fields to fight the present pandemic.

Alternative Manufacturing Concepts for Solid Oral Dosage Forms From Drug Nanosuspensions Using Fluid Dispensing and Forced Drying Technology

Flexible manufacturing technologies for solid oral dosage forms with a continuous adjustability of the manufactured dose strength are of interest for applications in personalized medicine. This study explored the feasibility of using microvalve technology for the manufacturing of different solid oral dosage form concepts. Hard gelatin capsules filled with excipients, placebo tablets, and polymer films, placed in hard gelatin capsules after drying, were considered as substrates. For each concept, a basic understanding of relevant formulation parameters and their impact on dissolution behavior has been established. Suitable matrix formers, present either on the substrate or directly in the drug nanosuspension, proved to be essential to prevent nanoparticle agglomeration of the drug nanoparticles and to ensure a fast dissolution behavior. Furthermore, convection and radiation drying methods were investigated for the fast drying of drug nanosuspensions dispensed onto polymer films, which were then placed in hard gelatin capsules. Changes in morphology and in drug and matrix former distribution were observed for increasing drying intensity. However, even fast drying times below 1 min could be realized, while maintaining the nanoparticulate drug structure and a good dissolution behavior.