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Singh N, Batra U, Kumar K, Ahuja N, Mahapatro A. Progress in bioactive surface coatings on biodegradable Mg alloys: A critical review towards clinical translation. Bioact Mater 2023; 19:717-757. [PMID: 35633903 PMCID: PMC9117289 DOI: 10.1016/j.bioactmat.2022.05.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/06/2022] [Accepted: 05/06/2022] [Indexed: 02/07/2023] Open
Abstract
Mg and its alloys evince strong candidature for biodegradable bone implants, cardiovascular stents, and wound closing devices. However, their rapid degradation rate causes premature implant failure, constraining clinical applications. Bio-functional surface coatings have emerged as the most competent strategy to fulfill the diverse clinical requirements, besides yielding effective corrosion resistance. This article reviews the progress of biodegradable and advanced surface coatings on Mg alloys investigated in recent years, aiming to build up a comprehensive knowledge framework of coating techniques, processing parameters, performance measures in terms of corrosion resistance, adhesion strength, and biocompatibility. Recently developed conversion and deposition type surface coatings are thoroughly discussed by reporting their essential therapeutic responses like osteogenesis, angiogenesis, cytocompatibility, hemocompatibility, anti-bacterial, and controlled drug release towards in-vitro and in-vivo study models. The challenges associated with metallic, ceramic and polymeric coatings along with merits and demerits of various coatings have been illustrated. The use of multilayered hybrid coating comprising a unique combination of organic and inorganic components has been emphasized with future perspectives to obtain diverse bio-functionalities in a facile single coating system for orthopedic implant applications. The challenges and current status of coatings are reviewed in light of clinical requirements. Multilayered hybrid coatings have been emphasized to obtain diverse bio-functionalities. The future developments and research directions on coatings for biodegradable implants are highlighted.
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Mahapatro A, Hlaing HM, Malladi L, Keshavanarayana S. Hybrid polymeric-metallic foams for bone tissue engineering scaffolds: mechanical properties and biofunctionality evaluations. INT J POLYM MATER PO 2021. [DOI: 10.1080/00914037.2021.1990058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Anil Mahapatro
- Department of Biomedical Engineering, Wichita State University, Wichita, KS, USA
| | - Hay Mar Hlaing
- Department of Industrial and Manufacturing Engineering, Wichita State University, KS, USA
| | - Lipi Malladi
- Department of Industrial and Manufacturing Engineering, Wichita State University, KS, USA
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Mahapatro A, Jensen K, Yang SY. Effect of polymer coating characteristics on the biodegradation and biocompatibility behavior of magnesium alloy. POLYM-PLAST TECH MAT 2019. [DOI: 10.1080/25740881.2019.1634728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Anil Mahapatro
- Department of Biomedical Engineering, Wichita State University, Wichita, KS, USA
| | - Kayla Jensen
- Department of Biomedical Engineering, Wichita State University, Wichita, KS, USA
| | - Shang-You Yang
- Department of Biological Sciences, Wichita State University, Wichita, KS, USA
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Gayle J, Mahapatro A, Lundin H. Preliminary Validation of a Dynamic Electrochemical Biodegradation Test Bench in Pseudo-Physiological Conditions. Mater Technol (N Y N Y) 2017; 33:135-144. [PMID: 30906177 PMCID: PMC6425958 DOI: 10.1080/10667857.2017.1416972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
There is a growing interest in the development of next generation stent materials. In vitro tests that accurately predict in vivo conditions, are needed for a full evaluation of a material's corrosion in vivo. In this manuscript a novel approach for the design of a dynamic electrochemical test bench is evaluated in hopes to later characterize and model biodegradable metallic stent materials. This dynamic test bench design allows for real-time corrosion testing with easy variation of temperature, shear stress, and simulated body fluids (SBF), with minimal complications of test sample fabrication. Preliminary tests have shown Tafel generation stable. Further testing of the stability of the test bench were conducted with the incorporation SBF, shear stress, and temperature. Shear stress was applied through variation in fluid velocities at 0 m/s, 0.127 m/s, 0.245 m/s, 0.372 m/s, 0.489 m/s at 37°C. Incorporation of the different SBFs showed no significant difference in corrosion readings; however, variances were observed higher in DMEM and PBS, than in Hanks, respectively. This dynamic test bench showed to be relatively stable under temperature and SBF modification; however, further optimization is needed to decrease variances seen throughout fluid velocity analysis.
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Mahapatro A, Negron TMD, Arshanapalli SA, Gomes AS, Yao L. Fabrication, Biofunctionality and Biocompatibility Evaluations of Octadecyltrichlorosilane Nano Coatings on Magnesium Alloy. ACTA ACUST UNITED AC 2015. [DOI: 10.1166/jnan.2015.1255] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Mahapatro A. Bio-functional nano-coatings on metallic biomaterials. Materials Science and Engineering: C 2015; 55:227-51. [DOI: 10.1016/j.msec.2015.05.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 03/20/2015] [Accepted: 05/07/2015] [Indexed: 11/28/2022]
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Bontrager J, Mahapatro A, Gomes AS. Microscopic bio-corrosion evaluations of magnesium surfaces in static and dynamic conditions. J Microsc 2014; 255:104-15. [PMID: 24910359 DOI: 10.1111/jmi.12142] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 05/07/2014] [Indexed: 11/30/2022]
Abstract
Biodegradable materials including biodegradable metals are continuously being investigated for the development of next generation cardiovascular stents. Predictive in vitro tests are needed that could evaluate potential materials while simulating in vivo conditions. In this manuscript we report the microscopic bio-corrosion evaluations of magnesium surfaces in static and dynamic conditions. A corrosion test bench was designed and fabricated and static and dynamic corrosion tests were carried out with samples of magnesium alloy. The fluid wall shear stress equation and the Churchill's friction factor equation were used to calculate the fluid velocity required to generate the desired shear stress on samples in the test bench. Static and dynamic corrosion tests at 24 and 72 h were carried out at 0.88 Pa shear stress mimicking the in vivo shear stress. Microscopic evaluations of the corroded surfaces were carried out by optical, scanning electron microscopy and energy dispersive X-ray spectroscopy to evaluate the corrosion behaviour and surface properties of the test samples. The surface and interface analysis of magnesium samples post test indicated that dynamic conditions prevented the build-up of corrosion by-products on the sample surface and the corrosion mechanism was uniform as compared to static conditions. The use of a masking element to restrict the exposed area of the sample didn't result in increased corrosion at the boundary. Thus, we have demonstrated the feasibility of the designed test bench as a viable method for bio-corrosion surface analysis under dynamic corrosion conditions for potential biodegradable cardiovascular stent materials.
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Affiliation(s)
- J Bontrager
- Bioengineering Program, Wichita State University, Wichita, Kansas, U.S.A
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Mahapatro A, Matos Negrón TD, Bonner C, Abdel-Fattah TM. Nanolayers on Magnesium (Mg) Alloy for Metallic Bone Tissue Engineering Scaffolds. J BIOMATER TISS ENG 2013. [DOI: 10.1166/jbt.2013.1084] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abdel-Fattah TM, Loftis D, Mahapatro A. Nanosized Controlled Surface Pretreatment of Biometallic Alloy 316L Stainless Steel. J Biomed Nanotechnol 2011; 7:794-800. [DOI: 10.1166/jbn.2011.1346] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Bhure R, Abdel-Fattah TM, Bonner C, Hall F, Mahapatro A. Stability of Phosphonic Self Assembled Monolayers (SAMs) on Cobalt Chromium (Co-Cr) Alloy under Oxidative conditions. Appl Surf Sci 2011; 257:5605-5612. [PMID: 21603056 PMCID: PMC3097514 DOI: 10.1016/j.apsusc.2011.01.055] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Cobalt Chromium (Co-Cr) alloys has been widely used in the biomedical arena for cardiovascular, orthopedic and dental applications. Surface modification of the alloy allows us to tailor the interfacial properties to address critical challenges of Co-Cr alloy in medical applications. Self assembled monolayers (SAMs) of Octadecylphosphonic acid (ODPA) have been used to form thin films on the oxide layer of the Co-Cr alloy surface by solution deposition technique. The SAMs formed were investigated for their stability to oxidative conditions of ambient laboratory environment over periods of 1, 3, 7 and 14 days. The samples were then characterized for their stability using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Contact Angle Measurements. Detailed high energy XPS elemental scans confirmed the presence of the phosphonic monolayer after oxidative exposure which suggested that the SAMs were firmly attached to the oxide layer of Co-Cr alloy. AFM images gave topographical data of the surface and showed islands of SAMs on Co-Cr alloy surface, before and after SAM formation and also over the duration of the oxidative exposure. Contact angle measurements confirmed the hydrophobicity of the surface over 14 days. Thus the SAMs were found to be stable for the duration of the study. These SAMs could be subsequently tailored by modifying the terminal functional groups and could be used for various potential biomedical applications such as drug delivery, biocompatibility and tissue integration.
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Affiliation(s)
- Rahul Bhure
- Center for Materials Research (CMR), Norfolk State University, Norfolk, Virginia 23504
| | - Tarek M. Abdel-Fattah
- Applied Research Center and Department of Biology, Chemistry, and Environmental Science, Christopher Newport University, Newport News, Virginia 23606
| | - Carl Bonner
- Center for Materials Research (CMR), Norfolk State University, Norfolk, Virginia 23504
- Department of Chemistry, Norfolk State University, Norfolk, Virginia 23504
| | - Felicia Hall
- Department of Chemistry, Norfolk State University, Norfolk, Virginia 23504
| | - Anil Mahapatro
- Center for Biotechnology and Biomedical Sciences (CBBS), Norfolk State University, Norfolk, Virginia 23504
- Department of Chemistry, Norfolk State University, Norfolk, Virginia 23504
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Affiliation(s)
- Rahul Bhure
- Center for Materials Research (CMR), Center for Biotechnology and Biomedical Sciences (CBBS), Department of Chemistry, Norfolk State University (NSU), Norfolk, VA 23504
| | - Anil Mahapatro
- Center for Materials Research (CMR), Center for Biotechnology and Biomedical Sciences (CBBS), Department of Chemistry, Norfolk State University (NSU), Norfolk, VA 23504
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Bhure R, Abdel-Fattah TM, Bonner C, Hall JC, Mahapatro A. Formation of Nanosized Phosphonic Acid Self Assembled Monolayers on Cobalt-Chromium Alloy for Potential Biomedical Applications. J Biomed Nanotechnol 2010; 6:117-28. [DOI: 10.1166/jbn.2010.1106] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Mahapatro A, Johnson DM, Patel DN, Feldman MD, Ayon AA, Agrawal CM. Drug delivery from therapeutic self-assembled monolayers (T-SAMs) on 316L stainless steel. Curr Top Med Chem 2008; 8:281-9. [PMID: 18393891 DOI: 10.2174/156802608783790929] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Delivery of therapeutic agents from self-assembled monolayers (SAMs) on 316L stainless steel (SS) has been demonstrated as a viable method to deliver drugs for localized coronary artery stent application. SAMs are highly-ordered, nano-sized molecular coatings, adding 1-10 nm thickness to a surface. Hydroxyl terminated alkanethiol SAMs of 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS with 48 hr immersion in ethanolic solutions. Attachment of ibuprofen (a model drug) to the functional SAMs was carried out in toluene for 5 hrs at 60 degrees C using Novozume-435 as a biocatalyst. SAM formation and subsequent attachment of ibuprofen was characterized collectively using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measure-ments. The quantitative in vitro release of ibuprofen into a "physiological" buffer solution was characterized using reverse phase HPLC. Drug release kinetics showed that 14.1 microg of ibuprofen eluted over a period of 35 days with 2.7microg being eluted in the first day and the remaining being eluted over a period of 35 days. The drug release kinetics showed an increase in ibuprofen elution that occurred during first 14 days (2.7microg in 1 day to 9.5 microg in 14 days), following which there was a decrease in the rate of elution. Thus, functional SAMs on 316L SS could be used as tethers for drug attachment and could serve as a drug delivery mechanism from stainless steel implants such as coronary artery stents.
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Affiliation(s)
- Anil Mahapatro
- Department of Biomedical Engineering and Department of Chemistry, The University of Texas at San Antonio, 6900 N Loop 1604 W, San Antonio, TX, USA
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Affiliation(s)
- Ankur S. Kulshrestha
- BD Medical-Medical Surgical Systems, BD, 1 Becton Drive, MC 212, Franklin Lakes, NJ 07417
| | - Anil Mahapatro
- Center for Biotechnology and Biomedical Sciences, Department of Chemistry, Norfolk State University, Norfolk, VA 23504
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Mahapatro A, Johnson DM, Patel DN, Feldman MD, Ayon AA, Agrawal CM. The use of alkanethiol self-assembled monolayers on 316L stainless steel for coronary artery stent nanomedicine applications: an oxidative and in vitro stability study. Nanomedicine: Nanotechnology, Biology and Medicine 2006; 2:182-90. [PMID: 17292141 DOI: 10.1016/j.nano.2006.07.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Accepted: 07/19/2006] [Indexed: 11/19/2022]
Abstract
The use of self-assembled monolayers (SAMs) on medical devices offers a methodology for the incorporation of nanotechnology into medicine. SAMs are highly ordered nanosized molecular coatings, adding 1 to 10 nm thickness to a surface. This work is part of an overall goal to deliver therapeutic drugs from the surface of metal coronary stents using SAMs. In this study the oxidative and in vitro stability of functional alkylthiol SAMs on 316L stainless steel (SS) has been demonstrated. SAMs of 11-mercaptoundecanoic acid (-COOH SAM) and 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measurements collectively confirmed the formation of functional alkylthiol SAMs on 316L SS. Well-formed SAMs (CA: 82 deg +/- 9 deg) were achieved within 48 hours of immersion in ethanolic solutions, after which no significant improvement in CA was observed. The ratio of the thiolate peak (163.5 eV) to the oxidized sulfur (sulfonates) peak (166.5 eV) gives us an indication of the percentage SAMs that would bind to the metal and serve as a drug reservoir in vivo; which in turn represents the stability and viability of these SAMs, keeping in mind the cardiovascular application under consideration. Oxidative and in vitro stability studies showed that alkanethiol SAMs oxidized completely within 14 days. The SAMs tend to desorb and leave the metal surface after longer time periods (21 days) in phosphate-buffered saline (PBS) immersion, whereas for oxidative exposure the SAMs continue to remain on the metal surface in the form of sulfonates. Although the chemistry of bonding of alkylthiol with the 316L SS is not well understood, the nanosized alkylthiol SAMs demonstrate sufficient stability to justify further study on these systems for potential in vivo drug delivery in the chosen coronary artery stent applications.
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Affiliation(s)
- Anil Mahapatro
- Department of Biomedical Engineering, The University of Texas at San Antonio, San Antonio, Texas, USA
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Mahapatro A, Johnson DM, Patel DN, Feldman MD, Ayon AA, Agrawal CM. Surface modification of functional self-assembled monolayers on 316L stainless steel via lipase catalysis. Langmuir 2006; 22:901-5. [PMID: 16430246 DOI: 10.1021/la052817h] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Lipase catalyzed esterification of therapeutic drugs to functional self-assembled monolayers (SAMs) on 316L stainless steel (SS) after assembly has been demonstrated. SAMs of 16-mercaptohexadecanoic acid (-COOH SAM) and 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS, and lipase catalysis was used to attach therapeutic drugs, perphenazine and ibuprofen, respectively, on these SAMs. The reaction was carried out in toluene at 60 degrees C for 5 h using Novozyme-435 as the biocatalyst. The FTIR spectra after surface modification of -OH SAMs showed the presence of the C=O stretching bands at 1745 cm(-1), which was absent in the FTIR spectra of -OH SAMs. Similarly, the FTIR spectra after the reaction of the -COOH SAM with perphenazine showed two peaks in the carbonyl region, a peak at 1764 cm(-1), which is the representative peak for the C=O stretching for esters. The second peak at 1681 cm(-1) is assigned to the C=O stretching of the remaining unreacted terminal COOH. XPS spectra after lipase catalysis with ibuprofen showed a photoelectron peak evolving at 288.5 eV which arises from the carbon (C=O) of the carboxylic acid of the drug (ibuprofen). Similarly for -COOH SAMs, after esterifiation we see a small, photoelectron peak evolving at 286.5 eV which corresponds to the C in the methylene groups adjacent to the oxygen (C-O), which should evolve only after the esterification of perphenazine with the -COOH SAM. Thus, lipase catalysis provides an alternate synthetic methodology for surface modification of functional SAMs after assembly.
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Affiliation(s)
- Anil Mahapatro
- College of Engineering, University of Texas at San Antonio, 6900 N Loop 1604 W, San Antonio, Texas 78249, USA
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Abstract
Immobilized Candida antarctica Lipase B (Novozyme-435) was studied for bulk polyesterifications of linear aliphatic hydroxyacids of variable chain length. The products formed were not fractionated by precipitation. The relative reactivity of the hydroxyacids was l6-hydroxyhexadecanoic acid approximately 12-hydroxydodecanoic acid approximately 10-hydroxydecanoic acid (DPavg congruent with 120, Mw/Mn <or = 1.5, 48 h, 90 degrees C) > 6-hydroxyhexanoic acid (DPavg congruent with 80, Mw/Mn < or = 1.5, 48 h, 90 degrees C). Remarkable improvements in molecular-weight buildup resulted from leaving water in the reaction. By 4 h, without application of vacuum, the DPavg for 12- and 16-carbon hydroxyacids was about 90. In contrast, with identical substrates and water removal, the DPavg at 4 h was about 23. Large differences in the molecular-weight build up of 12-hydroxydodecanoic acid were observed for catalyst concentrations (%-by-wt relative to monomer) of 0.1, 0.5, 1, and 10. Nevertheless, by 24 h, with 1% catalyst containing 0.1% lipase, poly(12-hydroxydodecanoic acid) with Mn 17 600 was formed. For 12-hydroxydodecanoic acid polymerization at 90 degrees C, the catalyst activity decreased by 7, 18, and 25% at reaction times of 4, 24, and 48 h, respectively. Furthermore, the retention of catalyst activity was invariable as a function of the substrates used.
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Affiliation(s)
- Anil Mahapatro
- NSF I/UCR Center for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Brooklyn, New York 11201, USA
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Mahapatro A, Kumar A, Kalra B, Gross RA. Solvent-Free Adipic Acid/1,8-Octanediol Condensation Polymerizations Catalyzed by Candida antartica Lipase B. Macromolecules 2003. [DOI: 10.1021/ma025796w] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anil Mahapatro
- NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Six Metro Tech Center, Brooklyn, New York 11201
| | - Ajay Kumar
- NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Six Metro Tech Center, Brooklyn, New York 11201
| | - Bhanu Kalra
- NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Six Metro Tech Center, Brooklyn, New York 11201
| | - Richard A. Gross
- NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Six Metro Tech Center, Brooklyn, New York 11201
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Mahapatro A, Kalra B, Kumar A, Gross RA. Lipase-catalyzed polycondensations: effect of substrates and solvent on chain formation, dispersity, and end-group structure. Biomacromolecules 2003; 4:544-51. [PMID: 12741768 DOI: 10.1021/bm0257208] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effects of substrates and solvent on polymer formation, number-average molecular weight (M(n)), polydispersity, and end-group structure for lipase-catalyzed polycondensations were investigated. Diphenyl ether was found to be the preferred solvent for the polyesterification of adipic acid and 1,8-octanediol giving a M(n) of 28 500 (48 h, 70 degrees C). The effect of varying the alkylene chain length of diols and diacids on the molecular weight distribution and the polymer end-group structure was assessed. A series of diacids (succinic, glutaric, adipic, and sebacic acid) and diols (1,4-butanediol, 1,6-hexanediol, and 1,8-octanediol) were polymerized in solution and in bulk. It was found that reactions involving monomers having longer alkylene chain lengths of diacids (sebacic and adipic acid) and diols (1,8-octanediol and 1,6-hexanediol) give a higher reactivity than reactions of shorter chain-length diacids (succinic and glutaric acid) and 1,4-butanediol. The bulk lipase-catalyzed condensation reactions were feasible, but the use of diphenyl ether gave higher M(n) values (42,400 g/mol in 3 days at 70 degrees C). The polydispersity varied little over the conditions studied giving values </=2. No specific trend with respect to end-group structure as a function of time was observed. At 70 degrees C, the retention of catalyst activity in the bulk was independent of substrate structure but was higher when reactions were conducted in diphenyl ether than in bulk.
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Affiliation(s)
- Anil Mahapatro
- NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Six Metro Tech Center, Brooklyn, New York 11201, USA
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