201
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Tsarevsky NV, Matyjaszewski K. Environmentally benign atom transfer radical polymerization: Towards “green” processes and materials. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/pola.21617] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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202
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Goraltchouk A, Scanga V, Morshead CM, Shoichet MS. Incorporation of protein-eluting microspheres into biodegradable nerve guidance channels for controlled release. J Control Release 2006; 110:400-407. [PMID: 16325953 DOI: 10.1016/j.jconrel.2005.10.019] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Revised: 10/18/2005] [Accepted: 10/25/2005] [Indexed: 11/27/2022]
Abstract
Nerve guidance channels (NGCs) promote axonal regeneration after transection injury of the peripheral nerve or spinal cord, yet this regeneration is limited. To enhance regeneration further, we hypothesize that localized delivery of therapeutic molecules combined with the NGC is required. In an attempt to achieve such an NGC, we designed and synthesized a novel NGC in which protein-encapsulated microspheres were stably incorporated into the tube wall. Specifically, poly(lactide-co-glycolide) (PLGA 50/50) microspheres were physically entrapped in the annulus between two concentric tubes, consisting of a chitosan inner tube and a chitin outer tube. Taking advantage of the extensive shrinking that the outer chitin tube undergoes with drying, >15 mg of microspheres were loaded within the tube walls. Using BSA-encapsulated microspheres as the model drug delivery system, BSA was released from microsphere loaded tubes (MLTs) for 84 days, and from freely suspended PLGA microspheres for 70 days. An initial burst release was observed for both MLTs and free microspheres, followed by a degradation-controlled release profile that resulted in a higher release rate from MLTs initially, which was then attenuated likely due to the buffering effect of chitin and chitosan tubes. Epidermal growth factor (EGF), co-encapsulated with BSA in PLGA 50/50 microspheres in MLTs, was released for 56 days with a similar profile to that of BSA. Released EGF was found to be bioactive for at least 14 days as assessed by a neurosphere forming bioassay.
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Affiliation(s)
- Alex Goraltchouk
- Department of Chemical Engineering and Applied Chemistry, University of Toronto 200 College Street, Toronto, ON, Canada M5S 3E5; Institute of Biomaterials and Biomedical Engineering, University of Toronto 4 Taddle Creek Road, Room 407, Toronto, ON, Canada M5S 3G9
| | - Vanessa Scanga
- Department of Surgery, University of Toronto, 1 King's College Circle-1182, Toronto, ON, Canada M5S 1A8
| | - Cindi M Morshead
- Department of Surgery, University of Toronto, 1 King's College Circle-1182, Toronto, ON, Canada M5S 1A8
| | - Molly S Shoichet
- Department of Chemical Engineering and Applied Chemistry, University of Toronto 200 College Street, Toronto, ON, Canada M5S 3E5; Department of Chemistry, 80 St. George St., Toronto, ON, Canada M5S 1AH; Institute of Biomaterials and Biomedical Engineering, University of Toronto 4 Taddle Creek Road, Room 407, Toronto, ON, Canada M5S 3G9.
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203
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Smet M, Gottschalk C, Skaria S, Frey H. Aliphatic Hyperbranched Copolyesters by Combination of ROP and AB2-Polycondensation. MACROMOL CHEM PHYS 2005. [DOI: 10.1002/macp.200500397] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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204
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Källrot M, Edlund U, Albertsson AC. Surface functionalization of degradable polymers by covalent grafting. Biomaterials 2005; 27:1788-96. [PMID: 16257444 DOI: 10.1016/j.biomaterials.2005.10.010] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Accepted: 10/10/2005] [Indexed: 11/21/2022]
Abstract
With a new non-destructive and solvent-free photografting technique, N-vinylpyrrolidone was covalently grafted onto the surfaces of degradable polymers; poly(l-lactide), poly(epsilon-caprolactone), poly(lactide-co-glycolide), and poly(trimethylene carbonate). The modified surfaces were characterized by XPS, ATR-FTIR, SEM, and cell growth tests. The wettability was markedly improved, as static contact angles changed from about 80 degrees for the pristine substrates to around 30 degrees after 30min of grafting. Well-defined surface topographies, such as micro-patterns, are preserved in the process since the graft layers are thin. The biological response, measured as cytotoxicity, showed that the modified films provide good substrates, comparable with optimized cell culture plastics, for the adhesion and proliferation of normal human keratinocytes and skin fibroblasts.
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Affiliation(s)
- Martina Källrot
- School of Chemical Science and Engineering, Royal Institute of Technology, Fibre and Polymer Technology, SE-100 44 Stockholm, Sweden
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205
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Dinarvand R, Alimorad MM, Amanlou M, Akbari H. In vitro release of clomipramine HCl and buprenorphine HCl from poly adipic anhydride (PAA) and poly trimethylene carbonate (PTMC) blends. J Biomed Mater Res A 2005; 75:185-91. [PMID: 16044413 DOI: 10.1002/jbm.a.30398] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Controlled drug-delivery technology is concerned with the systematic release of a pharmaceutical agent to maintain a therapeutic level of the drug in the body for modulated and/or prolonged periods of time. This may be achieved by incorporating the therapeutic agent into a degradable polymer vehicle, which releases the agent continuously as the matrix erodes. In this study, poly trimethylene carbonate (PTMC), an aliphatic polycarbonate, and poly adipic anhydride (PAA), an aliphatic polyanhydride, were synthesized via melt condensation and ring-opening polymerization of trimethylene carbonate and adipic acid, respectively. The release of clomipramine HCl and buprenorphine HCl from discs prepared with the use of PTMC-PAA blends in phosphate buffer (pH 7.4) are also described. Clomipramine HCl and buprenorphine HCl were both used as hydrophilic drug models. Theoretical treatment of the data with the Peppas model revealed that release of clomipramine HCl (5%) in devices containing 70% PTMC or more followed a Fickian diffusion model. However, the releases of buprenorphine HCl (5%) in the same devices were anomalous. For devices containing 50% and more PAA, surface erosion may play a significant role in the release of both molecules.
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Affiliation(s)
- Rassoul Dinarvand
- Department of Pharmaceutics, Faculty of Pharmacy, Tehran University of Medical Sciences, P. O. Box 14155-6451, Tehran, Iran.
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206
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Miao ZM, Cheng SX, Zhang XZ, Zhuo RX. Synthesis, Characterization, and Degradation Behavior of Amphiphilic Poly-α,β-[N-(2-hydroxyethyl)-l-aspartamide]-g-poly(ε-caprolactone). Biomacromolecules 2005; 6:3449-57. [PMID: 16283778 DOI: 10.1021/bm050551n] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of biodegradable amphiphilic graft polymers were successfully synthesized by grafting poly(epsilon-caprolactone) (PCL) sequences onto a water-soluble poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. The graft copolymers were prepared through the ring-opening polymerization of epsilon-caprolactone (CL) initiated by the macroinitiator PHEA with pendant hydroxyl groups without adding any catalyst. By controlling the feed ratio of the macroinitiator to the monomer, the copolymers with different branch lengths and properties can be obtained. The successful grafting of PCL sequences onto the PHEA backbone was verified by FTIR, 1H NMR, and combined size-exclusion chromatography and multiangle laser light scattering (SEC-MALLS) analysis. The hydrolytic degradation and enzymatic degradation of these graft copolymers were investigated. The results show the hydrolytic degradation rate increases with increasing content of hydrophilic PHEA backbone. While the enzymatic degradation rate is affected by two competitive factors, the catalytic effect of Pseudomonas cepacia lipase on the degradation of PCL branches and the hydrophilicity which depends on the copolymer composition. In situ observation of the degradation under polarizing light microscope (PLM) demonstrates the different degradation rates of different regions in the polymer samples.
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Affiliation(s)
- Zhi-Mei Miao
- Key Laboratory of Biomedical Polymers of Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, People's Republic of China
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207
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Tsarevsky NV, Matyjaszewski K. Combining Atom Transfer Radical Polymerization and Disulfide/Thiol Redox Chemistry: A Route to Well-Defined (Bio)degradable Polymeric Materials. Macromolecules 2005. [DOI: 10.1021/ma050020r] [Citation(s) in RCA: 213] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Nicolay V. Tsarevsky
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213
| | - Krzysztof Matyjaszewski
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213
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208
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209
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Benny O, Duvshani-Eshet M, Cargioli T, Bello L, Bikfalvi A, Carroll RS, Machluf M. Continuous Delivery of Endogenous Inhibitors from Poly(Lactic-Co-Glycolic Acid) Polymeric Microspheres Inhibits Glioma Tumor Growth. Clin Cancer Res 2005. [DOI: 10.1158/1078-0432.768.11.2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Purpose: There is an urgent need for modalities that can localize and prolong the administration of the antitumor agents, particularly antiangiogenic, to achieve long-term tumor inhibition. However, one of the major obstacles is designing a device in which the biological activity of sensitive endogenous inhibitors is retained. We have designed a biodegradable polymeric device, which provides a unique and practical means of localizing and continuously delivering hemopexin (PEX) or platelet factor 4 fragment (PF-4/CTF) at the tumor site while maintaining their biological activity. The potential and efficacy of this system is shown in vitro and in vivo in a human glioma mouse model.
Experimental Design: Polymeric microspheres made of poly(lactic-co-glycolic acid) (PLGA) were loaded with very low amounts of PEX and PF-4/CTF. The release profiles of these factors from PLGA and their biological activity were confirmed in vitro using proliferation assays done on endothelial and tumor cells. Tumor inhibition using this system was studied in nude mice bearing a human s.c. glioma.
Results: PEX and PF-4/CTF released in vitro from PLGA microspheres were biologically active and significantly inhibited the proliferation of human umbilical vein endothelial cells, bovine capillary endothelial cells, and U87-MG cells. A single local s.c. injection of PLGA microspheres loaded with low amounts of PEX or PF-4/CTF resulted in an 88% and 95% reduction in glioma tumor volume 30 days post-treatment. Immunohistochemical analysis of the treated tumors showed a marked decrease in tumor vessel density compared with untreated tumors.
Conclusion: Our findings show that polymeric microspheres are a very promising approach to locally and efficiently deliver endogenous inhibitors to the tumor site leading to a significant inhibition of the tumor.
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Affiliation(s)
- Ofra Benny
- 1Laboratory of Cancer Drug Therapeutics and Mammalian Cell Technology, Faculty of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Maayan Duvshani-Eshet
- 1Laboratory of Cancer Drug Therapeutics and Mammalian Cell Technology, Faculty of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Theresa Cargioli
- 4Laboratory of Neurosurgical Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Lorenzo Bello
- 2Molecular Mechanisms of Angiogenesis, Universite de Bordeaux I, Talence, France
| | - Andreas Bikfalvi
- 3Department of Neurological Sciences, University of Milan, Milan, Italy; and
| | - Rona S. Carroll
- 4Laboratory of Neurosurgical Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Marcelle Machluf
- 1Laboratory of Cancer Drug Therapeutics and Mammalian Cell Technology, Faculty of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
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210
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Bratton D, Brown M, Howdle SM. Novel fluorinated stabilizers for ring-opening polymerization in supercritical carbon dioxide. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/pola.21117] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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211
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Wu TM, Chiang MF. Fabrication and characterization of biodegradable poly(lactic acid)/layered silicate nanocomposites. POLYM ENG SCI 2005. [DOI: 10.1002/pen.20370] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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212
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Freiberg S, Zhu XX. Polymer microspheres for controlled drug release. Int J Pharm 2004; 282:1-18. [PMID: 15336378 DOI: 10.1016/j.ijpharm.2004.04.013] [Citation(s) in RCA: 814] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Revised: 04/21/2004] [Accepted: 04/22/2004] [Indexed: 11/25/2022]
Abstract
Polymer microspheres can be employed to deliver medication in a rate-controlled and sometimes targeted manner. Medication is released from a microsphere by drug leaching from the polymer or by degradation of the polymer matrix. Since the rate of drug release is controlled by these two factors, it is important to understand the physical and chemical properties of the releasing medium. This review presents the methods used in the preparation of microspheres from monomers or from linear polymers and discusses the physio-chemical properties that affect the formation, structure, and morphology of the spheres. Topics including the effects of molecular weight, blended spheres, crystallinity, drug distribution, porosity, and sphere size are discussed in relation to the characteristics of the release process. Added control over release profiles can be obtained by the employment of core-shell systems and pH-sensitive spheres; the enhancements presented by such systems are discussed through literature examples.
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Affiliation(s)
- S Freiberg
- Département de chimie, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, Que., H3C 3J7, Canada
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213
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Stolt M, Viljanmaa M, Södergård A, Törmälä P. Blends of poly(ε-caprolactone-b-lactic acid) and poly(lactic acid) for hot-melt applications. J Appl Polym Sci 2003. [DOI: 10.1002/app.13216] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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214
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Albertsson AC, Varma IK. Recent Developments in Ring Opening Polymerization of Lactones for Biomedical Applications. Biomacromolecules 2003; 4:1466-86. [PMID: 14606869 DOI: 10.1021/bm034247a] [Citation(s) in RCA: 1181] [Impact Index Per Article: 56.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbable devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field. The effect of structure on properties and degradation has been discussed. The applications of these polymers in the biomedical field are described in detail.
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Affiliation(s)
- Ann-Christine Albertsson
- Department of Fibre and Polymer Technology, The Royal Institute of Technology, S-10044 Stockholm, Sweden
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215
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Shenoy DB, D'Souza RJ, Tiwari SB, Udupa N. Potential applications of polymeric microsphere suspension as subcutaneous depot for insulin. Drug Dev Ind Pharm 2003; 29:555-63. [PMID: 12779285 DOI: 10.1081/ddc-120018644] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The objective of this investigation was to develop an injectable, depot-forming drug delivery system for insulin based on microparticle technology to maintain constant plasma drug concentrations over prolonged period of time for the effective control blood sugar levels. Formulations were optimized with two well-characterized biodegradable polymers namely, poly(DL-lactide-co-glycolide) and poly-epsilon-caprolactone and evaluated in vitro for physicochemical characteristics, drug release in phosphate buffered saline (pH 7.4), and evaluated in vivo in streptozotocin-induced hypoglycemic rats. With a large volume of internal aqueous phase during w/o/w double emulsion solvent evaporation process and high molecular weight of the polymers used, we could not achieve high drug capture and precise control over subsequent release within the study period of 60 days. However, this investigation revealed that upon subcutaneous injection, the biodegradable depot-forming polymeric microspheres controlled the drug release and plasma sugar levels more efficiently than plain insulin injection. Preliminary pharmacokinetic evaluation exhibited steady plasma insulin concentration during the study period. These formulations, with their reduced frequency of administration and better control over drug disposition, may provide an economic benefit to the user compared with products currently available for diabetes control.
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Affiliation(s)
- Dinesh B Shenoy
- Dr. T. M. A. Pai Pharmaceutical Research Centre, College of Pharmaceutical Sciences, Manipal, Karnataka, India.
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216
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Abstract
Polymers with ester linkages in their main chain comprise a family of polymers with immense diversity and versatility. This review deals with the preparation of such polymers from dicarboxylic acid monomers, and the result in terms of properties and applicability. Polyesters alone, and their copolymers with amides, anhydrides, urethanes, imides, ethers or other functional groups, offer countless opportunities to tune the properties of the resulting material within a broad range. Of particular interest is the inherent biodegradability of the ester linkage. Biodegradability is sought after in a wide range of applications, above all in the preparation of environmentally friendly polymers and biomedical materials for temporary surgical use and in drug delivery.
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Affiliation(s)
- U Edlund
- Department of Polymer Technology, Royal Institute of Technology, SE-100 44, Stockholm, Sweden
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217
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Shenoy DB, Antipov AA, Sukhorukov GB, Möhwald H. Layer-by-layer engineering of biocompatible, decomposable core-shell structures. Biomacromolecules 2003; 4:265-72. [PMID: 12625721 DOI: 10.1021/bm025661y] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The objective of the present investigation was to fabricate composite colloidal particles consisting of a sacrificial, decomposable template of biodegradable nature covered with biocompatible polyelectrolyte multilayers using the layer-by-layer sequential adsorption technique. Poly-dl-lactic acid and poly(dl-lactic-co-glycolic acid) were chosen to design the microparticulate template, and a preliminary feasibility study was carried out with poly(styrene sulfonate sodium)-poly(allylamine hydrochloride) as shell components. The properties of both core-shell and hollow structures obtained by core dissolution were characterized by confocal laser scanning microscopy, microelectrophoresis, scanning force microscopy, and scanning electron microscopy. The concept was then extended to biocompatible polyelectrolytes as shell wall building blocks to deduce stable hollow capsules with tailored properties. Uniform, complete coating with oppositely charged polyelectrolyte pairs was achieved for all the combinations investigated. The results demonstrate that polyester microparticles could serve as viable alternative components to conventionally employed templates to derive hollow capsules with defined size, shape, and shell thickness. With all the components used for fabrication being biocompatible, these polyelectrolyte capsules may find interesting applications in the fields of biology, biochemistry, biotechnology, and drug delivery.
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Affiliation(s)
- Dinesh B Shenoy
- Max Planck Institute of Colloids and Interfaces, D-14424, Potsdam/Golm, Germany
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