®Southwest Research Institute

of Pharmaceutical Products

San Antonio, Texas

Spray Encapsulation

Particle DevelopmentTo improve particle development, the Institute usesinnovative and state-of-the art techniques, includingspray drying and disk atomization. Using theseprocesses, SwRI scientists design, develop, and pro-totype a variety of drug-delivery systems.

Spray DryingSpray drying is suitable for producing heat-sensitiveproducts, with particle size ranging from 1 to 250micrometers. Spray drying enables small averageparticle size with a narrow range of particle size dis-tribution. Characteristics of spray drying include:

n Aqueous feed, and solvent processing available

n Atomization resulting from a rotating wheel,pressure nozzles, two-fluid nozzles, or by sonicenergy

n High-speed rotary atomization (5,000 to 30,000revolutions/minute)

n Outlet temperatures approximately equal toproduct temperature

Disk AtomizationDisk atomization uses a rotary atomizer. Disk runstypically use a lower volume of drying air than spraydrying, requiring less heat input. Disc atomizationcan be achieved using the following processes:

n Hot melt and prilling. Drugs are dispersed intomolten polymer and atomized from a disk.

n Solvent evaporation. A product is dissolved intoa solvent with a dissolved polymer and atomized.

n Water evaporation. A drug is dissolved intowater with a shell material and atomized.

Disk atomization possesses the following characteristics:

n Produces particles from 30 to 3,000 micrometers

n Achieves larger particle size in comparison to spray drying

n Uses solvent-based or molten polymer feedstock

n Obtains more spherical particles and better film coating compared to spray drying

ased on more than half a century of experience in encapsulation technology, Southwest Research Institute (SwRI) offers comprehensive

services in developing and characterizing pharmaceutical products for drugdelivery. Using their extensive expertise, SwRI scientists obtain desired release-rate characteristics by selecting and developing the optimum formulationby considering shell materials, coatings, particle size, and drug payload.

The SwRI production minor spray dryer can dryup to 25 kilograms per hour of water withrotary atomization or two-fluid atomization ofthe feed. Here a two-point collection (chamberand cyclone) system is installed.

B

Using visible or scanningelectron microscope, SwRI scientists image glyceride

hot-melt particles.

AAbboouutt tthhee ccoovveerr:: An SwRI-developed spinning disk providesextremely spherical particles with uniform coating.

Analytical CapabilitiesThe Institute applies numerous physical andchemical analytical techniques to analyzecapsule payload, release kinetics, and parti-cle sizes. Using state-of-the-art supportequipment, SwRI scientists analyze andmodify particle size and morphology andestablish release and stability factors in aformulation matrix.

Particle Analysis andCharacterizationParticle size and morphology may be charac-terized by a variety of methods, including:

n Optical particle sizer. Determines dis-tribution between 1 to 500 micrometersand provides number, area, or volumeaverage of wet or dry particles

n Submicron particle sizer. Characterizesnanoparticles in solution

n Optical or electron microscopy. Deter-mines surface characteristics, morphology,and particle size for particles of 25nanometers or less

n Vibratory screener. Used to sieve kilogramquantities of particles for classification anddetermining particle size ranges.

Particle Size Reduction (Millingand Micronization)The Institute is capable of reducing particle sizesto the nanometer size range. The apparatusincludes a ball mill, a centrifugal grinding mill,and a jet mill for gram- or kilogram-scale reduc-tion. Institute specialists perform milling at lowand extremely low temperatures (cryogenic) forprocessing heat-sensitive polymers andtemperature-sensitive drugs.

Stability and Release TestingUsing thermogravimetric analysis or differentialscanning calorimetry, SwRI pharmaceutical spe-cialists measure the thermal stability of drugs inpolymer matrices.

Institute chemists are experienced in deter-mining stability and rate of release of drugsfrom formulation matrices. They use a seriesof sophisticated techniques and equipment tosample and analyze performance of drugmatrices. These techniques include:

n Ultraviolet spectroscopy

n Fourier transform infrared spectroscopy

n Nuclear magnetic resonance

n High-performance liquid chromatography

n Franz cell studies

Using the environmental scanningelectron microscope, SwRIscientists are able to imagenonconductive samples withoutextensive sample preparation.

The Institute’s optical particle sizer is used to determine size distribution forparticles manufactured in the SwRI production minor spray dryer. This spraydryer can achieve average particle sizes up to 100 micrometers.

Thermogravimetric analysis is used to determine the temperatures atwhich drugs degrade. This process evaluates destabilizing interactionsof drugs and polymer matrices.

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Southwest Research Institute is an independent, nonprofit, applied engineering and physical sciences research anddevelopment organization using multidisciplinary approaches to problem solving. The Institute occupies more than1,200 acres and provides nearly two million square feet of laboratories, test facilities, workshops, and offices formore than 3,000 employees who perform contract work for industry and government clients.

Joseph McDonough, Ph.D., ManagerSynthesis and Drug Delivery SectionChemistry and Chemical Engineering DivisionSouthwest Research Institute6220 Culebra Road · P.O. Drawer 28510San Antonio, Texas 78228-0510(210) 522-3670 · Fax: (210) 522-4632E-mail: joseph.mcdonough@swri.orgWeb Site: www.swri.org

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Quality Certification — Chemistry & Chemical Engineering DivisionThe Chemistry and Chemical Engineering Division of Southwest ResearchInstitute has achieved certification to ISO 9001:2000, an internationallyrecognized quality standard.

We welcome your inquiries.For additional information, please contact:

SwRI Business Development • San Antonio, Texas • (210) 522-2122 • Fax: (210) 522-3496 • E-mail: bd@swri.org

Quality System Registered to

ISO 9001:2000

Consumer products improved by theuse of encapsulation include paints,cosmetics, deodorants, detergents,toothpastes, and shampoos.

©2006. Southwest Research Institute. All rights reserved. Southwest Research Institute and SwRI are registered marks in the U.S. Patent and Trademark Office.An Equal Opportunity Employer M/F/D/VCommitted to Diversity in the Workplace