Toxicological Assessment of Inhaled Nanoparticles: Role of in Vivo, ex Vivo, in Vitro, and in Silico Studies

The alveolar epithelium of the lung is by far the most permeable epithelial barrier of the human body. The risk for adverse effects by inhaled nanoparticles (NPs) depends on their hazard (negative action on cells and organism) and on exposure (concentration in the inhaled air and pattern of deposition in the lung). With the development of advanced in vitro models, not only in vivo, but also cellular studies can be used for toxicological testing. Advanced in vitro studies use combinations of cells cultured in the air-liquid interface. These cultures are useful for particle uptake and mechanistic studies. Whole-body, nose-only, and lung-only exposures of animals could help to determine retention of NPs in the body. Both approaches also have their limitations; cellular studies cannot mimic the entire organism and data obtained by inhalation exposure of rodents have limitations due to differences in the respiratory system from that of humans. Simulation programs for lung deposition in humans could help to determine the relevance of the biological findings. Combination of biological data generated in different biological models and in silico modeling appears suitable for a realistic estimation of potential risks by inhalation exposure to NPs

Impact of Surface Properties of Core Material on the Stability of Hot Melt-Coated Multiparticulate Systems

Hot melt coating (HMC) of an active pharmaceutical ingredient (API) powder with lipid-based excipients is an innovative method for manufacturing patient-convenient dosage forms. However, drug release instability is still its main industrial challenge. The correlation between the unstable pharmaceutical product performance with the solid-state alteration of lipids is currently well-investigated. The remaining problem is the inconsistent release alteration of different APIs coated with the same lipid after storage, such as faster release in some cases and slower release in others. The interaction between API surface and lipid-based coating and its alteration during storage were investigated in this work. The surface properties of five different APIs and the coating composition of tripalmitin and polysorbate 65 were screened via Washburn and pendant drop methods, respectively. Metformin hydrochloride and hydrochlorothiazide particles were each coated with the coating composition. The water sorption alteration of coated particles and the crystal growth of tripalmitin in the coating after storage were measured via tensiometry and X-ray diffraction. The cleavage work necessary to overcome the adhesion of coating composition on the core surface was calculated for each API. The accelerated release of the polar core (metformin) after storage was correlated with a low cleavage work and a distinctive phase separation. In contrast, a decelerated release of the hydrophobic core (hydrochlorothiazide) was favored by the crystal growth of the lipid-based coating. The gained knowledge can be used to design the product stability during the formulation development

Permeation of Therapeutic Drugs in Different Formulations across the Airway Epithelium In Vitro.

Pulmonary drug delivery is characterized by short onset times of the effects and an increased therapeutic ratio compared to oral drug delivery. This delivery route can be used for local as well as for systemic absorption applying drugs as single substance or as a fixed dose combination. Drugs can be delivered as nebulized aerosols or as dry powders. A screening system able to mimic delivery by the different devices might help to assess the drug effect in the different formulations and to identify potential interference between drugs in fixed dose combinations. The present study evaluates manual devices used in animal studies for their suitability for cellular studies.Calu-3 cells were cultured submersed and in air-liquid interface culture and characterized regarding mucus production and transepithelial electrical resistance. The influence of pore size and material of the transwell membranes and of the duration of air-liquid interface culture was assessed. Compounds were applied in solution and as aerosols generated by MicroSprayer IA-1C Aerosolizer or by DP-4 Dry Powder Insufflator using fluorescein and rhodamine 123 as model compounds. Budesonide and formoterol, singly and in combination, served as examples for drugs relevant in pulmonary delivery.Membrane material and duration of air-liquid interface culture had no marked effect on mucus production and tightness of the cell monolayer. Co-application of budesonide and formoterol, applied in solution or as aerosol, increased permeation of formoterol across cells in air-liquid interface culture. Problems with the DP-4 Dry Powder Insufflator included compound-specific delivery rates and influence on the tightness of the cell monolayer. These problems were not encountered with the MicroSprayer IA-1C Aerosolizer. The combination of Calu-3 cells and manual aerosol generation devices appears suitable to identify interactions of drugs in fixed drug combination products on permeation

Differences in TEER values between start and end of the transport studies when fluorescein, rhodamine 123, budesonide and formoterol were applied as solution to cells grown in submersed culture (SLE) and at the air-liquid interface (ALE) or applied by MicroSprayer IA-1C Aerosolizer (AID_M) and by DP-4 Dry Powder Insufflator (AID_D) to cells grown at the air-liquid interface culture (n = 12).

<p>Significant decrease is marked by asterisk.</p

Transport of marker dyes across the Calu-3 monolayer (green, fluorescein; red, rhodamine 123) when applied as solution to cells grown in submersed culture (SLE) or applied with MicroSprayer IA-1C Aerosolizer (AID_M) and DP-4 Dry Powder Insufflator (AID_D) to cells cultured at the air-liquid interface (n = 6).

<p>The total amount of drug applied to the cells was set as 100% and the transport rate was normalized to a membrane area of 1 cm².</p

Transport of budesonide and formoterol fumarate as single substance and as combination product Symbicort in AID_D exposure.

<p>Abbreviations: Form mix: formoterol when applied as Symbicort powder; Bud mix: budesonide when applied as Symbicort (n = 3). The total amount of drug applied to the cells was set as 100% and the transport rate normalized to a membrane area of 1 cm². Asterisks indicate differences between application as single substance and as combination.</p

Limitations and advantages of the manual devices for permeability testing.

<p>Limitations and advantages of the manual devices for permeability testing.</p

Transport rate of budesonide when applied in solution on cells in submersed culture (SLE) and on cells at an air-liquid interface (ALE).

<p>Abbreviations: SLE mix, ALE mix: mixture containing 50 μM budesonide and 0.5 mM formoterol fumarate was applied (n = 3). The total amount of drug applied to the cells was set as 100% and the transport rate was normalized to a membrane area of 1 cm².</p