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Ultrasonic atomisation into reduced pressure atmosphere--envisaging aseptic spray-drying for microencapsulation
Sergio Freitas1, Hans Peter Merkle, Bruno Gander
1Institute of Pharmaceutical Sciences, ETH Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
Summary
A new vacuum spray-drying method efficiently produces microspheres for drug delivery. This technique offers high yields and controllable particle size, suitable for aseptic preparation of protein-loaded microparticles.
Area of Science:
- Biomaterials Science
- Pharmaceutical Technology
- Chemical Engineering
Background:
- Conventional spray-drying methods often use high temperatures, limiting their use for sensitive biomolecules.
- Aseptic preparation of microparticles requires specialized techniques to maintain sterility and product integrity.
- Developing efficient and scalable methods for microencapsulation is crucial for drug delivery applications.
Purpose of the Study:
- To evaluate a novel spray-drying technique using ultrasonic atomization, reduced pressure, and liquid bath collection for microsphere preparation.
- To assess the suitability of this method for aseptic encapsulation of proteins, using bovine serum albumin (BSA) as a model.
- To characterize the particle yield, encapsulation efficiency, particle size, and drug release profile of the produced microspheres.
Main Methods:
- A novel spray-drying system was developed, employing an ultrasonic atomizer, vacuum drying, and a liquid collection bath.
- Poly(lactic-co-glycolic acid) (PLGA) microspheres encapsulating bovine serum albumin (BSA) were prepared using this technique.
- Particle yield, BSA encapsulation efficiency, mean particle size, particle size distribution, and in vitro release profiles were analyzed.
Main Results:
- The novel spray-drying method achieved particle yields exceeding 80%, significantly higher than conventional methods.
- BSA encapsulation efficiency was approximately 60%, with losses attributed to partitioning into the collection bath.
- Microspheres exhibited mean particle sizes ranging from 13 to 24 microm with excellent reproducibility.
- A high initial burst release (above 50%) was observed, which was reduced to 16% by using more concentrated polymer solutions (8% w/w).
Conclusions:
- The novel vacuum spray-drying technique is effective for aseptic preparation of protein-loaded microspheres with high yields and reproducible particle characteristics.
- The method's ability to use mild vacuum and liquid collection makes it suitable for sensitive biomolecules.
- Optimizing polymer concentration can effectively control the burst release of encapsulated drugs from the porous microspheres.