RESUMEN

There is an urgent need for scalable Microphysiological Systems (MPS's)1 that can better predict drug efficacy and toxicity at the preclinical screening stage. Here we present Mera, an automated, modular and scalable system for culturing and assaying microtissues with interconnected fluidics, inbuilt environmental control and automated image capture. The system presented has multiple possible fluidics modes. Of these the primary mode is designed so that cells may be matured into a desired microtissue type and in the secondary mode the fluid flow can be re-orientated to create a recirculating circuit composed of inter-connected channels to allow drugging or staining. We present data demonstrating the prototype system Mera using an Acetaminophen/HepG2 liver microtissue toxicity assay with Calcein AM and Ethidium Homodimer (EtHD1) viability assays. We demonstrate the functionality of the automated image capture system. The prototype microtissue culture plate wells are laid out in a 3 × 3 or 4 × 10 grid format with viability and toxicity assays demonstrated in both formats. In this paper we set the groundwork for the Mera system as a viable option for scalable microtissue culture and assay development.

RESUMEN

Interactions between hydrophobic drugs and endogenous gastrointestinal substances have the potential to manipulate drug concentration in the human gastrointestinal system, and thus likely play an important role in determining the rate of absorption for hydrophobic drugs. The effects of phospholipids, bile salts and digestive proteins on the solution behaviour of clofazimine in biorelevant media was demonstrated here using dissolution experiments and solid state analytical techniques. Clofazimine is a hydrophobic, anti-mycobacterial agent with virtually no detectable water solubility in its free base form. Salt forms of the drug offer improved aqueous solubility but are unstable in solutions at low pH (pH 1.6) or high pH (pH 6.5). At low pH and high chloride ion concentrations, CFZ in solution experiences a high driving force to crystallize from solution as a hydrochloride salt, which is insoluble, while at high pH CFZ does not dissolve to any extent. In this study, it is demonstrated that amphipathic compounds present in the gastric and intestinal systems can overcome the instability experienced by CFZ at these pH values. This is done by encapsulation of the hydrophobic drug in mixed bile salt phospholipid micelles in both the gastric and intestinal fluid, and by the drug actively binding with the digestive enzyme pepsin in the gastric system. Pepsin binds and solubilises the drug at even relatively low concentration (0.1 mg/mL). When pepsin concentration is increased in the gastric media, a corresponding increase in the solution stability of CFZ is observed.

Asunto(s)

Antibacterianos/química , Clofazimina/química , Jugo Gástrico/química , Secreciones Intestinales/química , Ácidos y Sales Biliares/química , Cristalización , Tracto Gastrointestinal/química , Concentración de Iones de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Micelas , Pepsina A/química , Sales (Química) , Solubilidad

RESUMEN

Clofazimine is an antimycobacterial agent that is routinely used for the treatment of leprosy. Clofazimine has also been shown to have high clinical potential for the treatment of many Gram-positive pathogens, including those that exhibit high levels of antibiotic resistance in the medical community. The use of clofazimine against these pathogens has largely been limited by the inherently poor water solubility of the drug substance. In this work, the possibility of repurposing and reformulating clofazimine to maximize its clinical potential is investigated. To achieve this, the potential of novel salt forms of clofazimine as supersaturating drug-delivery vehicles to enhance the aqueous solubility and gastrointestinal solubility of the drug substance was explored. The solution properties of seven novel salt forms, identified during an initial screening process, were examined in water and in a gastrointestinal-like media and were compared and contrasted with those of the free base, clofazimine, and the commercial formulation of the drug, Lamprene. The stability of the most promising solid forms was tested, and their bioactivity against Staphylococcus aureus was also compared with that of the clofazimine free base and Lamprene. Salts forms which showed superior stability as well as solubility and activity to the commercial drug formulation were fully characterized using a combination of spectroscopic techniques, including X-ray diffraction, solid-state NMR, and Fourier transform infrared spectroscopy.