Performance Evaluation of a High-Precision Low-Dose Powder Feeder

Vibrational manipulation of dry granular materials in lab-on-a-chip devices

We present vibrational techniques to pump, mix, and separate dry granular materials using multifrequency vibrations applied to a solid substrate with a standard audio system. The direction and velocity of the granular flow are tuned by modulating the sign and amplitude, respectively, of the vibratory waveform, with typical pumping velocities of centimeters per second. Different granular materials are mixed by combining them at Y-shaped junctions, and mixtures of granules with different friction coefficients are separated along straight channels by judicious choice of the vibratory waveform. We demonstrate that the observed velocities accord with a theory valid for sufficiently large or fast vibrations, and we discuss the implications for using vibrational manipulation in conjunction with established microfluidic technologies to combine liquid and dry solid handling operations at sub-millimeter length scales.

Development and implementation of a pneumatic micro-feeder for poorly-flowing solid pharmaceutical materials

Consistent powder micro-feeding (<100 g/h) is a significant challenge in manufacturing solid oral dosage forms. The low dose feeding can well control the content consistency of the dosage forms, which improves drug efficiency and reduces manufacturing waste. Current commercial micro-feeders are limited in their ability to feed < 20 g/h of cohesive (i.e. powders of poor flowability) active pharmaceutical ingredients (API) and excipients (e.g. lubricants) with low fluctuation. To breach this gap, this study presents an advanced micro-feeder design capable of feeding a range of pharmaceutical-grade powders consistently at flow rates as low as 0.7 g/h with <20 % flow rate variation. This was possible due to a novel powder conveying concept utilising particle re-entrainment to minimise flow rate variations. This work details the design of this pneumatic micro-feeder and its excellent micro-feeding performance even for cohesive powders. The experimental studies investigated the influence of the process parameters (air pressure and air flow rate) and equipment configurations (insert size and plug position) on the feeding performance of different pharmaceutical-relevant powders, i.e., microcrystalline cellulose (MCC), croscarmellose sodium (CCS), crospovidone (XPVP) and paracetamol (APAP). It was shown that the system is capable of delivering consistent powder flow rates with good repeatability and stability.

Lipid-based solubilization technology via hot melt extrusion: promises and challenges

INTRODUCTION

Self-emulsifying drug delivery systems (SEDDS) are a promising strategy to improve the oral bioavailability of poorly water-soluble drugs (PWSD). The excipients of SEDDS enable permeation through the mucus and gastro-intestinal barrier, inhibiting efflux transporters (e.g. P-glycoprotein) of drugs. Poor drug loading capacity and formulation instability are the main setbacks of traditional SEDDS. The use of polymeric precipitation inhibitors was shown to create supersaturable SEDDS with increased drug payload, and their solidification can help to overcome the instability challenge. As an alternative to several existing SEDDS solidification technologies, hot melt extrusion (HME) holds the potential for lean and continuous manufacturing of supersaturable solid-SEDDS. Despite being ubiquitously applied in solid lipid and polymeric processing, HME has not yet been widely considered for the preparation of SEDDS.

AREAS COVERED

The review begins with the rationale why SEDDS as the preferred lipid-based delivery systems (LBDS) is suitable for the oral delivery of PWSD and discusses the common barriers to oral administration. The potential of LBDS to surmount them is discussed. SEDDS as the flagship of LBDS for PWSD is proposed with a special emphasis on solid-SEDDS. Finally, the opportunities and challenges of HME from the lipid-based excipient (LBE) processing and product performance standpoint are highlighted.

EXPERT OPINION

HME can be a continuous, solvent-free, cost-effective, and scalable technology for manufacturing solid supersaturable SEDDS. Several critical formulations and process parameters in successfully preparing SEDDS via HME are identified.

Development of a Controlled Continuous Low-Dose Feeding Process

This paper proposes a feed rate control strategy for a novel volumetric micro-feeder, which can accomplish low-dose feeding of pharmaceutical raw materials with significantly different powder properties. The developed feed-forward control strategy enables a constant feed rate with a minimum deviation from the set-point, even for materials that are typically difficult to accurately feed (e.g., due to high cohesion or low density) using conventional continuous feeders. Density variations observed during the feeding process were characterized via a displacement feed factor profile for each powder. The characterized effective displacement density profile was applied in the micro-feeder system to proactively control the feed rate by manipulating the powder displacement rate (i.e., computing the feed rate from the powder displacement rate). Based on the displacement feed factor profile, the feed rate can be predicted during the feeding process and at any feed rate set-point. Three pharmaceutically relevant materials were used for the micro-feeder evaluation: di-calcium phosphate (large-particle system, high density), croscarmellose sodium (small-particle system, medium density), and barium sulfate (very small-particle <10 μm, high density). A significant improvement in the feeding performance was achieved for all investigated materials. The feed rate deviation from the set-point and its relative standard deviation were minimal compared to operations without the control strategy.

A solution for low-dose feeding in continuous pharmaceutical processes

Continuous feeding of small quantities of powder is increasingly applied in pharmaceutical manufacturing. With that regard, what is crucial is not only the feasibility, but also the accuracy and stability. To enable stable processing, low amounts of various agents, e.g., lubricants, can be used. Even more important is the exact dosage of highly potent active pharmaceutical ingredients (APIs), which require feed rates within the range of grams per hour. Conventional feeders cannot supply powder at such rates, especially when the material properties are challenging. In this work, a novel micro-feeder was integrated into a continuous manufacturing line and its capability to supply API at feed rates down to one gram per hour was tested. The micro-feeder system is based on the principle of active volumetric displacement: a piston pushes the powder out of the cartridge upwards to the end of a plate, where a scraper places it into the process inlet. In this study, a hot melt extrusion process was used, during which the API was dissolved in a polymer matrix. Samples of the strand were analysed with regard to their content by means of HPLC. The results showed that the novel micro-feeder system can feed powder with good accuracy and reproducibility, indicating its high potential for continuous process implementation.