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Evaluating 3D-Printed Pre-separator Inserts in a Fast Screening Impactor for Physicochemical Characterization of Fine
Nathan A Reed1, Roee Dar2, Nicholas Holtgrewe2
1Office of Pharmaceutical Quality, Office of Pharmaceutical Quality Research, Division of Pharmaceutical Quality Research II, Food and Drug Administration, Saint Louis, Missouri, USA. Nathan.Reed@fda.hhs.gov.
AAPS Pharmscitech
|July 31, 2025
Summary
Modified 3D-printed inserts for the Fast Screening Impactor (FSI) improve fine particle dose (FPD) collection accuracy for orally inhaled drug products (OIDPs). Decreasing the S/D ratio enhanced cutoff efficiency, matching results from full-resolution cascade impactors.
Area of Science:
- Pharmaceutical Sciences
- Drug Delivery Systems
- Aerodynamics
Background:
- Accurate collection of fine particle dose (FPD, particles < 5 µm) from orally inhaled drug products (OIDPs) is crucial for physicochemical characterization.
- The Fast Screening Impactor (FSI) is used for simplified FPD collection, but concerns exist regarding its cutoff efficiency, particularly for dry powder inhalers (DPIs).
- Overrepresentation of larger particles can impact quality control and bioequivalence studies.
Purpose of the Study:
- To evaluate design modifications of FSI pre-separator inserts for improved FPD collection efficiency.
- To develop 3D-printed FSI inserts that yield FPD results comparable to full-resolution cascade impactors (ACI, NGI).
- To assess the impact of varying nozzle length (T) and baseplate-to-nozzle distance (S) on impactor cutoff performance.
Main Methods:
- 3-dimensional (3D) printing was used to create modified FSI pre-separator inserts with varied T/D and S/D ratios.
- Commercial DPIs were tested using the modified FSI inserts.
- FPD results were compared against those obtained from Anderson Cascade Impactor (ACI) and Next Generation Impactor (NGI).
Main Results:
- Increasing the T/D ratio showed minimal improvement in cutoff efficiency for the standard insert.
- Decreasing the S/D ratio to 1.0 significantly improved the cutoff characteristics of the FPD insert.
- The improved 3D-printed FPD insert demonstrated FPD collection closely matching ACI and NGI results.
Conclusions:
- Optimized 3D-printed FSI inserts can accurately collect FPD, comparable to established cascade impactors.
- The S/D ratio is a critical design parameter for enhancing the cutoff efficiency of FSI pre-separator inserts.
- This approach offers a more reliable method for FPD characterization in OIDP development and quality control.
