Surface Energy in Dry Powders for Inhalation – a myth or reality?

This poster was presented by MEGGLE with the Kiel University for Pharmaceutics and Biopharmaceutics:

Introduction

• Interactive blends require adhesion between carrier and API to be modulated.
• Several studies concluded causal relationship between decreased surface energy (SE) of either component of interactive blends and increases in aerodynamic performance i.e increase in fine particle fraction (FPF)
• Published literature often contains confounding factors in the attempt to establish this causal relationship [1,2]
• Hypothesis in question: Surface energy of carrier↓ → Aerodynamic performance of interactive blend ↑
  

Experimental setup

Investigate relationship between surface energy and FPF:

A) Create silanised lactose carrier with reduced SE
B) Verify absence of confounding variables with SEM
C) Verfiy different surface energies with inverse gas chromatography measurements
D) Create interactive blends with respective carriers
E) Investigate aerodynamic performance with FSI

Methods

A) Surface modification of lactose monohydrate

Silanisation protocol

• Suspension of α-lactose monohydrate (InhaLac 230, Meggle GmbH & Co.KG) in trichlorethylene
• 5%(v/v) chlorotrimethylsilane
• Heating the suspension to 80° C
• Reaction time: 5 h
• Vacuum filtration + vacuum drying
• Sieving fraction 63-90 μm

D) Preparation of interactive blends

InhaLac 230 as received Budesonic 2% -> Interactiv blend or silanised lactose

→ use of low shear mixing to keep the silanised lactose surface undamaged; homogeneity of the blends was verified via HPLC

E) Aerodynamic performance testing

Experimental design

• 25 mg of interactive blend per capsule, each run using the RS01 inhaler, contained a single capsule
• Flow rate was set to 80 L/min and cut-off plate for 5 μm at this given flow rate was used in the FSI
• Drug quantification via HPLC

Results

B) SEM results (magnification 500x)

→ no apparent differences between the as received quality and the silanised lactose

C) Results of surface energy determination

→ silanised lactose has lower surface energy across all nominal surface coverages

E) Aerodynamic performance results

→ no statistically significant difference between blends

See the full brochure on Surface Energy DPI here

(click the picture to download the brochure)

Source: MEGGLE, Zeredescht Majid, Ricarda Leister, Regina Scherließ, Kiel University, technical brochure “Surface Energy DPI”

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