Polymer Macro- and Micro-Gel Beads: Fundamentals and Applications Amos Nussinovitch Polymer Macro- and Micro-Gel Beads: Fundamentals and Applications 123 AmosNussinovitch InstituteofBiochemistry, FoodScienceandHumanNutrition TheRobertH.SmithFacultyof Agriculture,FoodandEnvironment TheHebrewUniversityofJerusalem Rehovot Israel [email protected] ISBN978-1-4419-6617-9 e-ISBN978-1-4419-6618-6 DOI10.1007/978-1-4419-6618-6 SpringerNewYorkDordrechtHeidelbergLondon LibraryofCongressControlNumber:2010934122 ©SpringerScience+BusinessMedia,LLC2010 Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewritten permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY10013,USA),exceptforbriefexcerptsinconnectionwithreviewsorscholarlyanalysis.Usein connectionwithanyformofinformationstorageandretrieval,electronicadaptation,computersoftware, orbysimilarordissimilarmethodologynowknownorhereafterdevelopedisforbidden. Theuseinthispublicationoftradenames,trademarks,servicemarks,andsimilarterms,eveniftheyare notidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyaresubject toproprietaryrights. Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) Preface Beads made from Egyptian faience have been excavated from grave deposits (c.4000–3100BC),togetherwithbeadsofglazedsteatite(asoftrock)andofsemi- precious stones such as turquoise, carnelian, quartz, and lapis lazuli. Information on these and many more ancient beads used for ornaments and jewelry, ritual ceremonies, as art artifacts and gifts for amorous women throughout history, and descriptions of the raw materials (e.g., glass, bone, precious and other stones) and manufacturing technologies used for their production can be located in many references. Many books are devoted to the description of beads that are not of water-soluble polymer origin, techniques for their production, their art, value, and distribution,reflectingthewealthofinformationexistinginthisfieldofscienceand art.Ontheotherhand,therearenobooksfullydevotedtothefascinatingtopicof hydrocolloid (polymeric) beads and their unique applications. A few books con- tainscatteredchaptersanddetailsonsuchtopics,whileemphasizingthepossibility of locating fragments of information elsewhere; however, again, there is no book that is solely devoted to hydrocolloid beads and their versatile applications. In the meantime,theuseofwater-solublehydrocolloidbeadsisontheriseinmanyfields, makingabookthatcoversbothpastandnovelapplicationsofsuchbeads,aswell astheirpropertiesandwaysinwhichtomanipulatethem,crucial.Theaiminwrit- ingthisvolumewastopresent,inaneasy-to-followsequence,adescriptionofbead productionmethodsandoftechniqueswhichcanbeusedtoestimate,andmodify, theirphysicalandchemicalproperties.Thisbookoffersafulldescriptionofnotonly traditionalandrecentdevelopmentsandapplicationsofbeadsinthefieldsofagri- culture, biotechnology, environmental studies, medicine, and food, but also topics whichhaveneverbeencoveredintheliterature,makingitoftheutmostimportance toindustryandacademia. Chapter1:PhysicalPropertiesofBeadsandTheirEstimation InChapter1,thecriteriausedtodescribetheshapeandsizeofbeadsareexplained. In particular, sections on roundness, sphericity, measurement of axial dimensions, and resemblance to geometric bodies are included. A special section is devoted to v vi Preface the methods used to estimate average projected area, volume, and density, includ- ing specific gravity balance and pycnometric methods. Other sections are devoted to bead surface area and specific surface in porous media, e.g., dried beads. Also covered are image processing and its utilization for hydrocolloid beads. Finally, the chapter discusses the structure of hydrocolloid beads, their density, and their porosity. Chapter2:BeadFormation,Strengthening,andModification Thischapterbeginswithabriefoverviewofthetypicalpolymericmaterialsusedfor beadcreationandtheirlimitations.Afulldescriptionisthenprovidedofprocedures toconstructdifferentbeadforms,e.g.,fromcylindricaltoalmostperfectlyspheri- cal,bychangingboththemoldsandthemediaintowhichthemoltenordissolved hydrocolloidpreparationisdroppedortransferred.Also,someinformationondrop- ping methods, changing drop size and distribution, and liquid sprays is provided, affording a measure of control over bead size and distribution. The various water- soluble polymers that can be used for bead formation are discussed at length. The properties of gel beads prepared from agar/agarose κ-carrageenan, alginate, cellu- loses,chitosan,andtoalesserextentpolyacrylamideandothersyntheticpolymers, amongmanyothers,aredescribed.Theuseofcrosslinkingagentsforbothcreation andstrengtheningofseveralbeadtypesisthoroughlycovered.Specialmethodsto modifytheporosityoftheformedbeadsarealsodescribed,asaremethodsofslow dissolutionofcrystalsbyacidtofacilitatebettergrowthofembeddedcellsviapH regulation. A special section is devoted to beads prepared from proteins, ways to increase their stability (with, for example, glutaraldehyde), and their influence on the cells embedded within them. Since a combination of alternative methods may wellprovideagoodmeansofovercomingtheevidentshortcomingsofcurrentbead- formation techniques, at the end of this chapter, a few approaches are presented, such as adding epoxy-resin reagent and curing agent to alginate for matrix stabi- lization, and other less known approaches for bead stabilization, as well as less traditionalwaysofproducingandmodifyingbeads. Chapter3:MethodsandMathematicalModelsfortheDryingof PolymericBeads Water-solublepolymerbeadscanbedriedforavarietyofpurposes(describedinfull inChapter6).Ingeneral,afterdrying,thetextureisporous.Inmanycases,thebead iscapableofretainingitsintegrityevenafterimmersioninwaterforlongperiods. In addition, and in contrast to wet gel beads, porosity facilitates the liberation of gasesduringfermentationwithoutharmingthedriedbead’sintegrity.Thischapter coversmethodsfordryingpolymericbeads,includingair-drying,fluidized-bedand Preface vii microwave-assisted fluidized-bed drying, and freeze-drying, and freeze-dried bio- logical products are fully described. Sections also include drying of dosage forms made of drug dispersed in a polymer, mathematical and numerical models to ana- lyze the drying, and a discussion of special cases such as drying a polymer bead withshrinkage. Chapter4:FoodandBiotechnologicalApplications forPolymericBeadsandCarriers Theimmobilizationofmicroorganismsorcellsuspensionsinbeadsforavarietyof biotechnologicalandfoodpurposesisdescribed—informationwhichishardtofind in currently available books. Examples include amino acid (e.g., L-aspartic acid, L-alanine, and L-phenylalanine) production, organic acid (e.g., citric acid, malic acid,gluconicacid,lacticacid)fermentationandconversion,specialusesinethanol, wine,vinegar,andsakeproductionsuchasmalolacticfermentation,removalofurea from sake and wine by immobilized acid urease, beer brewing using an immobi- lizedyeastbioreactorsystem,andusesinsoysauceproduction.Otherusesrelated to miscellaneous flavor materials and aroma compounds are also discussed. These include,butarenotlimitedto,biotransformationfromgeranioltonerol,production of limonin, β-ionone, naringin, blue cheese flavor, vanillin, and Japanese season- ing.Specialbeadsthatserveforimmobilizationandareusedinthemilkindustry, e.g., for hydrolysis of lactose in milk, are also detailed. Miscellaneous applica- tions also include production of oligosaccharides, preservatives and bacteriocins, xylitol, carotenoids and leucrose, and cis,cis-muconic acid. Less known uses of enzymesimmobilizedwithinbeadsforfoodapplicationsarealsodescribed.Various industrial options such as fuel ethanol production, application of gels for sepa- ration matrices, bioartificial organs, and insect-cell immobilization are included. In general, the chapter attempts to touch upon all of the novel applications of bead-immobilizedcellsforthefoodandbiotechnologyindustries,suchasthepro- duction of aroma compounds, the microbial production of bioflavors and their biotransformation. Chapter5:MedicinalApplicationsofHydrocolloid Beads This chapter gathers together information culled from many sources. It describes theuseofcellsencapsulatedinhydrogels,stemcellsinbeadenvironments,charged hydrogel beads as new microcarriers for cell culture, as a potential support for endothelial cells, and for vaccine delivery. Other sections provide information on crosslinked chitosan beads for different medicinal purposes: mucoadhesive beads andtheirapplicationsforeyesandthealimentarysystemandpolyelectrolytecom- plexes. Additional sections describe novel approaches to cell encapsulation for improved biocompatibility and immunoisolation. Emphasis is placed on methods viii Preface using alginate–polylysine alginate for encapsulation, and a glimpse is provided of the art and science of artificial cells, encapsulated enzymes for the clinical laboratory,andencapsulationoflivingcellsandtissuesforbiomedicalpurposes. Chapter6:DryBeadFormation,Structure,Properties, andApplications The drying of hydrocolloid beads results in cellular moieties, and this chapter therefore deals with cellular solids. A few manufacturing methods for hydrocol- loid cellular solids are described. They include, but are not limited to, drying bicarbonate-containinggelsafteraciddiffusionandcellularsolidsproducedbyfer- mentation and enzymatically. A special section deals with the inclusion of oils in gelsandtheirinfluenceonthepropertiesoftheresultantdriedcellularsolid.Several methods, e.g., compression studies, are described for evaluating the mechanical propertiesofthedriedbeads.Thechapteralsodetailsthemodelsusedfordescrib- ingthesebeads’stress–strainbehavior.Thestructureandacousticpropertiesofsuch cellular solids as a result of production method are also addressed. The applica- tionsofdriedbeadshaveneverbeenthoroughlyreviewed.Thischapterattemptsto redressthisbydescribingtheiruseascarriersforvitamins,asstudymodels,andfor separationandincludesspecialdrybeadsforwatertreatmentandmatricesentrap- pinghydrocolloidcellularbeads.Hydrocolloidcellularcarriersforagriculturaluses are also presented, e.g., the preservation of biocontrol agents in a viable form by dry cellular bead carriers and the carriers’ capacity to protect these agents against UV radiation. The chapter ends with a discussion on the textural features of dried hydrocolloidbeads. Chapter7:Liquid-CoreBeadsandTheirApplicationsinFood, Biotechnology,andOtherFields In1971,Maddox’spatentonsoftgelatincapsuleswasapproved.In1980,Limand Sunpublishedtheirhallmarkstudyinwhichmicroencapsulatedisletswereusedas abioartificialpancreas.Inthatmanuscript,alginate–polylysineliquid-corecapsules wereproducedanddescribed.Inthefoodarea,Sneath’spatent(1975)andlaterour group contributed to the manufacture and study of liquid-core hydrocolloid cap- sules.Thischapterdescribestheseliquid-corecapsules,bothnaturalandsynthetic, and the procedures used to produce them. Methods for including oil within these capsules are also provided, along with an overview of their biotechnological and special food applications. Additional biotechnological applications of liquid-core capsules include growth of microorganisms and activity of enzymes within them, and food applications include the manufacture of unique specialty foods and fruit productsandtheencapsulationofaromaandhealthcompounds,amongothers.The chapter also describes agricultural and environmental uses of liquid-core capsules Preface ix and illustrates some special applications: aids to quitting smoking, in the beauty industryforremovalofbodyhair,andinthepaperindustry. Chapter8:BeadsasDrugCarriers Beads are often used as drug carriers in passive, as well as active drug targeting, makingthisahighlyrelevanttopicintoday’sresearch.Majorgeneraltopicscovered inthefirstpartofthischapterincludecontrolleddrugrelease,gelsindrug-delivery systems, dual drug-loaded beads, and drug release from the beads. Throughout, issuessuchasmethodsofdrugincorporation,beadproperties,extentandnatureof crosslinking and the physicochemical properties of the drug, interactions between the drug and the matrix material, concentration of the matrix material and release environment(e.g.,thepresenceofenzymes)arediscussed.Describedbeadsinclude albumin beads, alginate beads, alginate beads reinforced with chitosan, calcium alginate/PNIPAAMbeads,differentchitosanbeads(e.g.,chitosan–tripolyphosphate beads, chitosan microspheres in treating rheumatoid arthritis, carboxymethyl chi- tosan beads), gelatin beads and those crosslinked with dextran, modified starch microspheres, dextran beads, gellan beads, guar beads, pectin beads for colon- specific drug delivery, pectin–chitosan beads, and modified poly(vinyl alcohol) microspheres. The chapter also summarizes information on achieving controlled production of the beads, such as preparation of biodegradable hydrogels based on polyesters, hydrogels with degradable crosslinking agents and those crosslinked with small molecules, azo reagents or albumin, and hydrogels with biodegradable pendant chains. The chapter finishes with a description of the more unique beads, suchasthosewithfloatingabilityandthosemadefromxyloglucan. Chapter9:BeadsandSpecialApplicationsofPolymers forAgriculturalUses Theconceptofbeadencapsulationhasbecomehighlyrelevanttoagriculture.Beads canencapsulatemicroorganismsforuseinthefieldofbacterialinoculationtechnol- ogy.Immobilizedplantcellsuspensionsandsingleseedproductshaveproventobe easytoproduce,store,andhandleduringindustrialoperation.Thischapterdescribes the goals of encapsulation in agriculture, e.g., to temporarily protect the encapsu- lated microorganisms from the soil environment and microbial competition and to releasethemgraduallyforthecolonizationofplantroots.Specialcasesforenlarg- ingpopulationsinwhichtheentrappedbacterialbiomassislowaredescribed;other casesinwhich,forexample,immobilizedfungiareusedasbiocontrolagentsagainst soil-borne pathogens are thoroughly detailed; survival of bead-entrapped popula- tions is compared with that of populations encapsulated in peat, and the influence ofspecialadditivesonbacterialsurvivalisdescribed.Inaddition,timingandmeth- ods for the application of bacterial inoculants are delineated. In particular, topics