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Xing Y, Xu Z, Liu T, Shi L, Kohane D, Guo S. Synthesis of Poly(acyclic orthoester)s: Acid‐Sensitive Biomaterials for Enhancing Immune Responses of Protein Vaccine. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202001169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Yumeng Xing
- Key Laboratory of Functional Polymer Materials of Ministry of Education State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry College of Chemistry Nankai University Tianjin 300071 China
| | - Zunkai Xu
- Key Laboratory of Functional Polymer Materials of Ministry of Education State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry College of Chemistry Nankai University Tianjin 300071 China
| | - Tao Liu
- Key Laboratory of Functional Polymer Materials of Ministry of Education State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry College of Chemistry Nankai University Tianjin 300071 China
| | - Linqi Shi
- Key Laboratory of Functional Polymer Materials of Ministry of Education State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry College of Chemistry Nankai University Tianjin 300071 China
| | - Daniel Kohane
- Laboratory for Biomaterials and Drug Delivery Division of Critical Care Medicine Children's Hospital Boston Harvard Medical School 300 Longwood Avenue Boston MA 02115 USA
| | - Shutao Guo
- Key Laboratory of Functional Polymer Materials of Ministry of Education State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry College of Chemistry Nankai University Tianjin 300071 China
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Xing Y, Xu Z, Liu T, Shi L, Kohane D, Guo S. Synthesis of Poly(acyclic orthoester)s: Acid-Sensitive Biomaterials for Enhancing Immune Responses of Protein Vaccine. Angew Chem Int Ed Engl 2020; 59:7235-7239. [PMID: 32061182 DOI: 10.1002/anie.202001169] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Indexed: 11/09/2022]
Abstract
While poly(acyclic orthoester)s (PAOEs) have many appealing features for drug delivery, their application is significantly hindered by a lack of facile synthetic methods. Reported here is a simple method for synthesizing acyclic diketene acetal monomers from diols and vinyl ether, and their polymerization with a diol to first synthesize PAOEs. The PAOEs rapidly hydrolyze at lysosomal pH. With the help of a cationic lipid, ovalbumin, a model vaccine antigen was efficiently loaded into PAOEs nanoparticles using a double emulsion method. These nanoparticles efficiently delivered ovalbumin into the cytosol of dendritic cells and demonstrated enhanced antigen presentation over poly(lactic-co-glycolic acid) (PLGA) nanoparticles. PAOEs are promising vehicles for intracellular delivery of biopharmaceuticals and could increase the utility of poly(orthoesters) in biomedical research.
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Affiliation(s)
- Yumeng Xing
- Key Laboratory of Functional Polymer Materials of Ministry of Education, State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Zunkai Xu
- Key Laboratory of Functional Polymer Materials of Ministry of Education, State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Tao Liu
- Key Laboratory of Functional Polymer Materials of Ministry of Education, State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Linqi Shi
- Key Laboratory of Functional Polymer Materials of Ministry of Education, State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
| | - Daniel Kohane
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Shutao Guo
- Key Laboratory of Functional Polymer Materials of Ministry of Education, State Key Laboratory of Medicinal Chemical Biology and Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China
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3
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Toward Understanding Drug Release From Biodegradable Polymer Microspheres of Different Erosion Kinetics Modes. J Pharm Sci 2016; 105:1934-1946. [DOI: 10.1016/j.xphs.2016.04.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 04/01/2016] [Accepted: 04/01/2016] [Indexed: 11/22/2022]
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Abstract
INTRODUCTION Proteins are effective biotherapeutics with applications in diverse ailments. Despite being specific and potent, their full clinical potential has not yet been realized. This can be attributed to short half-lives, complex structures, poor in vivo stability, low permeability, frequent parenteral administrations and poor adherence to treatment in chronic diseases. A sustained release system, providing controlled release of proteins, may overcome many of these limitations. AREAS COVERED This review focuses on recent development in approaches, especially polymer-based formulations, which can provide therapeutic levels of proteins over extended periods. Advances in particulate, gel-based formulations and novel approaches for extended protein delivery are discussed. Emphasis is placed on dosage form, method of preparation, mechanism of release and stability of biotherapeutics. EXPERT OPINION Substantial advancements have been made in the field of extended protein delivery via various polymer-based formulations over last decade despite the unique delivery-related challenges posed by protein biologics. A number of injectable sustained-release formulations have reached market. However, therapeutic application of proteins is still hampered by delivery-related issues. A large number of protein molecules are under clinical trials, and hence, there is an urgent need to develop new methods to deliver these highly potent biologics.
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Affiliation(s)
- Ravi Vaishya
- University of Missouri-Kansas City, Pharmaceutical Sciences , Kansas City, MO , USA
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Ahmed Abdelbary A, Elsayed I, Hassen Elshafeey A. Design and development of novel lipid based gastroretentive delivery system: response surface analysis,in-vivoimaging and pharmacokinetic study. Drug Deliv 2013; 22:37-49. [DOI: 10.3109/10717544.2013.868960] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Li L, Xu Y, Milligan I, Fu L, Franckowiak EA, Du W. Synthesis of Highly pH-Responsive Glucose Poly(orthoester). Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306391] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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7
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Li L, Xu Y, Milligan I, Fu L, Franckowiak EA, Du W. Synthesis of Highly pH-Responsive Glucose Poly(orthoester). Angew Chem Int Ed Engl 2013; 52:13699-702. [DOI: 10.1002/anie.201306391] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Indexed: 11/11/2022]
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8
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Xue P, Zhang K, Zhang Z, Li Y, Liu F, Sun Y, Zhang X, Song C, Fu A, Jin B, Yang K. Highly Sensitive Chemiluminescent Analysis of Residual Bovine Serum Albumin (BSA) Based on a Pair of Specific Monoclonal Antibodies and Peroxyoxalate–glyoxaline–PHPPA Dimer Chemiluminescent System in Vaccines. Appl Biochem Biotechnol 2012; 166:1604-14. [DOI: 10.1007/s12010-012-9567-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2011] [Accepted: 01/18/2012] [Indexed: 10/14/2022]
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Hamidi M, Zarei N. A reversed-phase high-performance liquid chromatography method for bovine serum albumin assay in pharmaceutical dosage forms and protein/antigen delivery systems. Drug Test Anal 2009; 1:214-8. [DOI: 10.1002/dta.33] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Hamidi M, Zarei N, Zarrin AH, Mohammadi-Samani S. Preparation and in vitro characterization of carrier erythrocytes for vaccine delivery. Int J Pharm 2007; 338:70-8. [PMID: 17317049 DOI: 10.1016/j.ijpharm.2007.01.025] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Revised: 01/11/2007] [Accepted: 01/16/2007] [Indexed: 10/23/2022]
Abstract
Erythrocytes as the most readily available and abundant cells within the body, have been studied extensively for their potential application as drug delivery carriers. In this study, human erythrocytes have been loaded by bovine serum albumin (BSA) as a model antigen/protein using hypotonic preswelling method for targeted delivery of this antigen to antigen-presenting cells (APCs). A series of in vitro tests have been carried out to characterize the carrier cells in vitro, including loading parameters, BSA and hemoglobin release kinetics, hematological indices, particle size distribution, SEM analysis, osmotic and turbulence fragility, and osmotic competency. BSA was loaded in erythrocytes with a loaded amount of 1.98+/-0.009mg with antigen release from carrier cells showing a zero-order kinetic consistent to that of the cell lysis. The apparent cell sizes, measured using laser scattering, were not significantly different from normal erythrocytes, but the real sizes, measured using SEM, and surface topologies were quite different between loaded and unloaded cells. The BSA-loaded cells were remarkably more fragile and less deformable compared to the normal cells. Totally, BSA-loaded erythrocytes seem to be a promising delivery system for reticuloendothelial system (RES) targeting of the antigens.
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Affiliation(s)
- M Hamidi
- Department of Pharmaceutics, Faculty of Pharmacy, Shiraz University of Medical Sciences, P.O. Box 71345-1583 Shiraz, Iran.
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Zilberman M, Shraga I. Microsphere-based bioresorbable structures loaded with proteins for tissue regeneration applications. J Biomed Mater Res A 2006; 79:370-9. [PMID: 16883585 DOI: 10.1002/jbm.a.30775] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Novel bioresorbable fiber/microsphere composite structures loaded with proteins were developed and studied. These unique polymeric structures are designed to combine good mechanical properties with a desired controlled protein-release profile, in order to serve as scaffolds for tissue regeneration applications. The composite fiber structures were formed by "coating" poly(L-lactic acid) fibers with protein-containing poly(DL-lactic-co-glycolic acid) microspheres. The microspheres were prepared by a double emulsion technique and were loaded with the model enzyme horseradish peroxidase (HRP). The present study focused on the effect of the double emulsion's composition and processing conditions on the microsphere structure and on the resulting cumulative protein release for 90 days. The release profiles generally exhibited an initial burst effect, a lag period and an increased release rate after 2 months. HRP release from these structures was governed by diffusion, rather than by degradation. A decrease in the emulsion's mixing rate significantly improved the release profile through unique matrix-like structures. The initial burst effect can be reduced by decreasing the internal phase quantity and its protein content, or by adding a surfactant to the internal emulsion. Proper selection of the double emulsion formulation and processing conditions can yield fiber microsphere structures with the desired protein release behavior.
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Affiliation(s)
- Meital Zilberman
- Department of Biomedical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel.
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Sipos P, Csóka I, Srčič S, Pintye-Hódi K, Erős I. Influence of preparation conditions on the properties of Eudragit microspheres produced by a double emulsion method. Drug Dev Res 2005. [DOI: 10.1002/ddr.10425] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Wang L, Chaw CS, Yang YY, Moochhala SM, Zhao B, Ng S, Heller J. Preparation, characterization, and in vitro evaluation of physostigmine-loaded poly(ortho ester) and poly(ortho ester)/poly(D,L-lactide-co-glycolide) blend microspheres fabricated by spray drying. Biomaterials 2004; 25:3275-82. [PMID: 14980422 DOI: 10.1016/j.biomaterials.2003.09.099] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2003] [Accepted: 09/22/2003] [Indexed: 11/29/2022]
Abstract
The physostigmine-loaded poly(ortho ester) (POE), poly(dl-lactide-co-glycolide) (PLGA) and POE/PLGA blend microspheres were fabricated by a spray drying technique. The in vitro degradation of, and physostigmine release from, the microspheres were investigated. SEM analysis showed that the POE and POE/PLGA blend particles were spherical. They were better dispersed when compared to the pure PLGA microspheres. Two glass transition temperature ( Tg ) values of the POE/PLGA blend microspheres were observed due to the phase separation of POE and PLGA in the blend system. XPS analysis proved that POE dominated the surfaces of POE/PLGA blend microspheres, indicating that the blend microspheres were coated with POE. The encapsulation efficiencies of all the microspheres were more than 95%. The incorporation of physostigmine reduced the Tg value of microspheres. The Tg value of the degrading microspheres increased with the release of physostigmine. For instance, POE blank microspheres and physostigmine-loaded POE microspheres had a Tg value of 67 degrees C and 48 degrees C, respectively. After 19 days in vitro incubation, Tg of the degrading POE microspheres increased to 55 degrees C. Weight loss studies showed that the degradation of the blend microspheres was accelerated with the presence of PLGA because its degradation products catalyzed the degradation of both POE and PLGA. The release rate of physostigmine increased with increase of PLGA content in the blend microspheres. The initial burst release of physostigmine was effectively suppressed by introducing POE to the blend microspheres. However, there was an optimized weight ratio of POE to PLGA (85:15 in weight), below which a high initial burst was induced. The POE/PLGA blend microspheres may make a good drug delivery system.
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Affiliation(s)
- Ling Wang
- Institute of Materials Research and Engineering, National University of Singapore, No. 3 Research Link, Singapore 117602, Singapore
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Zhang XZ, Chu CC. A responsive poly(N-isopropylacrylamide)/poly(ethylene glycol) diacrylate hydrogel microsphere. Colloid Polym Sci 2004. [DOI: 10.1007/s00396-004-1160-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Liu SQ, Yang YY, Liu XM, Tong YW. Preparation and Characterization of Temperature-Sensitive Poly(N-isopropylacrylamide)-b-poly(d,l-lactide) Microspheres for Protein Delivery. Biomacromolecules 2003; 4:1784-93. [PMID: 14606909 DOI: 10.1021/bm034189t] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Temperature-sensitive diblock copolymers, poly(N-isopropylacrylamide)-b-poly(D,L-lactide) (PNIPAAm-b-PLA) with different PNIPAAm contents were synthesized and utilized to fabricate microspheres containing bovine serum albumin (BSA, as a model protein) by a water-in-oil-in-water double emulsion solvent evaporation process. XPS analysis showed that PNIPAAm was a dominant component of the microspheres surface. BSA was well entrapped within the microspheres, and more than 90% encapsulation efficiency was achieved. The in vitro degradation behavior of microspheres was investigated using SEM, NMR, FTIR, and GPC. It was found that the microspheres were erodible, and polymer degradation occurred in the PLA block. Degradation of PLA was completed after 5 months incubation in PBS (pH 7.4) at 37 degrees C. A PVA concentration of 0.2% (w/v) in the internal aqueous phase yielded the microspheres with an interconnected porous structure, resulting in fast matrix erosion and sustained BSA release. However, 0.05% PVA produced the microspheres with a multivesicular internal structure wrapped with a dense skin layer, resulting in lower erosion rate and a biphasic release pattern of BSA that was characterized with an initial burst followed by a nonrelease phase. The microspheres made from PNIPAAm-b-PLA with a higher portion of PNIPAAm provided faster BSA release. In addition, BSA release from the microspheres responded to the external temperature changes. BSA release was slower at 37 degrees C (above the LCST) than at a temperature below the LCST. The microspheres fabricated with PNIPAAm-b-PLA having a 1:5 molar ratio of PNIPAAm to PLA and 0.2% (w/v) PVA in the internal aqueous phase provided a sustained release of BSA over 3 weeks in PBS (pH 7.4) at 37 degrees C.
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Affiliation(s)
- Shao-Qiong Liu
- Institute of Bioengineering and Nanotechnology, 1 Science Park Road, #01-01/10, The Aries, Singapore Science Park II, Singapore 117586
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Zhang M, Yang Z, Chow LL, Wang CH. Simulation of Drug Release from Biodegradable Polymeric Microspheres with Bulk and Surface Erosions. J Pharm Sci 2003; 92:2040-56. [PMID: 14502543 DOI: 10.1002/jps.10463] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
New models are developed to account for the kinetics of drug release from porous, biodegradable polymeric microspheres under the schemes of bulk erosion and surface erosion of the polymer matrix, respectively. Three mechanisms of drug release, namely, drug diffusion, drug dissolution, and polymer erosion jointly govern the overall release process. For bulk erosion, the model incorporates an erosion term into the dissolution and diffusion equation and is solved numerically for various boundary conditions. Dissolution and erosion are defined in the model by introducing three equations which take into account the drug concentration in the liquid phase, virtual solid phase, and effective solid phase. For surface erosion, drug concentrations in liquid and solid phases are defined and a substitution is introduced to convert the moving-boundary problem to a fixed-boundary problem. The resulting differential equations are solved simultaneously to obtain the concentration profile in the liquid and solid phases, respectively. Numerical solutions are provided to illustrate the effects of drug dissolution constant, drug diffusion coefficient, and erosion rate constant. In general, increasing erosion rate, diffusivity, dissolution, and decreasing particle radius enhance the drug release rate. Predictions from the models are also compared with experimental data to verify their validity and possible improvements are proposed.
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Affiliation(s)
- Mingping Zhang
- Department of Chemical and Environmental Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576
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Deng JS, Li L, Tian Y, Ginsburg E, Widman M, Myers A. In vitro characterization of polyorthoester microparticles containing bupivacaine. Pharm Dev Technol 2003; 8:31-8. [PMID: 12665195 DOI: 10.1081/pdt-120017521] [Citation(s) in RCA: 20] [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
Laboratory-scale spray-congealing equipment was utilized to fabricate injectable microparticles consisting of polyorthoester and bupivacaine. Operating conditions for the spray-congealing process were optimized to produce microparticles with the desired shape and particle size to yield acceptable syringeability and injectability. Characterizations were performed to determine the chemico-physical properties of polyorthoester before and after microparticle fabrication. Microparticles with different drug loadings and comparable particle sizes were produced, and their in vitro drug-release profiles were determined. The in vitro drug release of microparticles with a high drug loading was markedly faster than those with a low drug loading. This is partially attributed to a more significant initial burst-drug release of the microparticles with a high drug loading. The microparticles have demonstrated the potential to be used for long-acting postsurgery pain management by local injection.
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Affiliation(s)
- Jone-Shin Deng
- Advanced Drug Delivery, Hospital Products Division, Abbott Laboratories, Abbott Park, Illinois 60064, USA.
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Shi M, Yang YY, Chaw CS, Goh SH, Moochhala SM, Ng S, Heller J. Double walled POE/PLGA microspheres: encapsulation of water-soluble and water-insoluble proteins and their release properties. J Control Release 2003; 89:167-77. [PMID: 12711441 DOI: 10.1016/s0168-3659(02)00493-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The poly(orthoester) (POE)-poly(D,L-lactide-co-glycolide) (50:50) (PLGA) double-walled microspheres with 50% POE in weight were loaded with hydrophilic bovine serum albumin (BSA) and hydrophobic cyclosporin A (CyA). Most of the BSA and CyA was entrapped within the shell and core, respectively, because of the difference in their hydrophilicity. The morphologies and release mechanisms of proteins-loaded double-walled POE/PLGA microspheres were investigated. Scanning electron microscope studies revealed that the CyA-BSA-loaded double-walled POE/PLGA microspheres yielded a more porous surface and PLGA shell than those without BSA. The neat POE and PLGA yielded slow and incomplete CyA and BSA release. In contrast, nearly complete BSA and more than 95% CyA were released in a sustained manner from the double-walled POE/PLGA microspheres. Both the BSA- and CyA-BSA-loaded POE/PLGA microspheres yielded a sustained BSA release over 5 days. The CyA release pattern of the CyA-loaded double-walled POE/PLGA microspheres was biphasic, characterized by a slow release over 15 days followed by a sustained release over 27 days. However, the CyA-BSA-loaded double-walled POE/PLGA microspheres provided a more constant and faster CyA release due to their more porous shell. In the CyA-BSA-loaded double-walled POE/PLGA microspheres system, the PLGA layer acted as a carrier for BSA and mild reservoir for CyA. During the first 5 days, most BSA was released from the shell but only 14% CyA was left from the microspheres. Subsequently, more than 80% CyA were released in the next 25 days. The distinct structure of double-walled POE/PLGA microspheres would make an interesting device for controlled delivery of therapeutic agents.
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Affiliation(s)
- Meng Shi
- Institute of Materials Research and Engineering, No. 3 Research Link, 117602, Singapore, Singapore
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Yang YY, Shi M, Goh SH, Moochhala SM, Ng S, Heller J. POE/PLGA composite microspheres: formation and in vitro behavior of double walled microspheres. J Control Release 2003; 88:201-13. [PMID: 12628328 DOI: 10.1016/s0168-3659(02)00491-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The poly(ortho ester) (POE) and poly(D,L-lactide-co-glycolide) 50:50 (PLGA) composite microspheres were fabricated by a water-in-oil-in-water (w/o/w) double emulsion process. The morphology of the composite microspheres varied depending on POE content. When the POE content was 50, 60 or 70% in weight, the double walled microspheres with a dense core of POE and a porous shell of PLGA were formed. The formation of the double walled POE/PLGA microspheres was analysed. Their in vitro degradation behavior was characterized by scanning electron microscopy, gel permeation chromatography, Fourier-transform infrared microscopy and nuclear magnetic resonance spectroscopy (NMR). It was found that compared to the neat POE or PLGA microspheres, distinct degradation mechanism was achieved in the double walled POE/PLGA microspheres system. The degradation of the POE core was accelerated due to the acidic microenvironment produced by the hydrolysis of the outer PLGA layer. The formation of hollow microspheres became pronounced after the first week in vitro. 1H NMR spectra showed that the POE core was completely degraded after 4 weeks. On the other hand, the outer PLGA layer experienced slightly retarded degradation after the POE core disappeared. PLGA in the double walled microspheres kept more than 32% of its initial molecular weight over a period of 7 weeks.
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Affiliation(s)
- Yi-Yan Yang
- Institute of Materials Research and Engineering, No. 3 Research Link, Singapore 117602, Singapore.
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Wan JP, Yang YY, Chung TS, Tan D, Ng S, Heller J. POE-PEG-POE triblock copolymeric microspheres containing protein. II. Polymer erosion and protein release mechanism. J Control Release 2001; 75:129-41. [PMID: 11451503 DOI: 10.1016/s0168-3659(01)00374-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The first paper of this series presented the fabrication and characterization of POE-PEG-POE triblock copolymeric microspheres containing protein. In this paper, we focus on the polymer erosion and the mechanism of protein release. Fourteen-week in vitro behaviors of POE-PEG-POE microspheres loaded with bovine serum albumin (BSA) have been monitored. SEM micrographs reveal that after 14-week incubation in PBS buffer, pH 7.4, 37 degrees C, the polymeric particles remain spherical despite mass loss of almost 90%. On the other hand, molecular weight undergoes a high initial loss of 38% and 44% during the first 2-week incubation for POE-PEG(5%)-POE and POE-PEG(10%)-POE, respectively. Then, it keeps relatively unchanged over 12 weeks. However, POE-PEG(20%)-POE copolymer provides a better compatibility between the POE and PEG blocks. Hydrolysis is homogeneous through the polymer backbone. Thus, its molecular weight remains relatively constant and mass loss shows quite sustained over the 14-week in vitro release. The similar phenomena are observed in the polydispersity index of the degrading copolymers. SDS-PAGE of the encapsulated BSA within the POE-PEG(5%)-POE microspheres displays that the structural integrity of BSA is intact for at least 8 weeks due to a mild environment provided by the copolymer. In addition, XPS and FTIR are utilized to investigate protein behaviors in the degrading microspheres. Protein release from the POE-PEG-POE microspheres shows a biphasic pattern, characterized by an initial stage followed by a non-detectable release. The non-release phase is dominated by either slow polymer degradation or dense microsphere matrix structures. The microsphere formulation is optimized and a sustained protein release over 2 weeks is achieved by using POE-PEG(20%)-POE at a high protein loading.
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Affiliation(s)
- J P Wan
- Institute of Materials Research and Engineering, No.3 Research Link, Singapore 117602
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