Poly (lactic acid) (PLA) was synthesized by microwave-assisted ring-opening polymerization of D, L-lactide with stannous octanoate (SnOct(2)) as catalyst. Its weight-average molar mass (M-w) ranged from 39000 to 67000...Poly (lactic acid) (PLA) was synthesized by microwave-assisted ring-opening polymerization of D, L-lactide with stannous octanoate (SnOct(2)) as catalyst. Its weight-average molar mass (M-w) ranged from 39000 to 67000 and the polydispersity index from 1.3 to 1.7. The polymerization rate was much faster than that of the conventional thermal polymerization. A degradation of newly formed PLA in reaction mixture by microwave irradiation was observed.展开更多
Repeated-batch and continuous production of L-lactic acid by immobilized Rhizopusoryzae with calcium alginate entrapment method in a three-phase fluidized-bed bioreactor was stud-ied.The operation conditions were opti...Repeated-batch and continuous production of L-lactic acid by immobilized Rhizopusoryzae with calcium alginate entrapment method in a three-phase fluidized-bed bioreactor was stud-ied.The operation conditions were optimized.The productivity based on total reactor volume wasabout 3 times higher than that with free cells in a traditional stirred tank bioreactor.A mathemat-ical model was proposed and the model predictions were in good agreement with the experimentaldat.展开更多
A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the ...A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the acidity and auto-accelerating degradation of PDLLA during degradation and to improve its biospecificity and biocompatibility. The synthetic copolymer was characterized by FTIR, ^13C NMR and amino acid analyzer （AAA）.展开更多
The goal of this study is to design and synthesize a linear segmented shape memory poly（urethane-urea） （SMPUU） that possesses near-body-temperature shape memory temperature （Ttran） and enhanced mechanical proper...The goal of this study is to design and synthesize a linear segmented shape memory poly（urethane-urea） （SMPUU） that possesses near-body-temperature shape memory temperature （Ttran） and enhanced mechanical properties by incorporating flexible poly（ethylene glycol） 400 （PEG400） to form poly（D,L-lactic acid）-based macro- diols （PDLLA-PEG400-PDLLA） and then rigid piperazine （PPZ） as a chain extender to form the desired SMPUUs （PEG400-PUU-PPZ）. PEG400 increased Mn while maintaining a lower Tg of PDLLA-PEG400-PDLLA, which together with PPZ improved the mechanical properties of PEG400-PUU-PPZ. The obtained optimum SMPUU with enhanced mechanical properties （O＇y = 24.28 MPa; zf = 698%; Uf = 181.5 MJIm3） and a Tg of 40.62~C exhibited sound shape memory properties as well, suggesting a promising SMPUU for in vivo biomedical applications.展开更多
Biodegradable chitosan-g-poly (D, L-lactic acid) copolymers were prepared via two methods. (1) The lactide was grafted onto hydroxyl groups of chitosan by using macromolecular initiator sodium of trimethylsilyl-chit...Biodegradable chitosan-g-poly (D, L-lactic acid) copolymers were prepared via two methods. (1) The lactide was grafted onto hydroxyl groups of chitosan by using macromolecular initiator sodium of trimethylsilyl-chitosan, (2) poly (D,L-lactic acid)(PLA) with low molecular weight can be linked to the amino group by coupling activated PLA to trimethylsilyl-chitosan. Two graft copolymers had hydrophilic-hydrophobic character and can be applied as carriers for drug delivery.展开更多
To develop a novel degradable poly (L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) bioactive materials for bone tissueengineering, β-TCP powder was produced by a new wet process. Porous scaffolds were prepared ...To develop a novel degradable poly (L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) bioactive materials for bone tissueengineering, β-TCP powder was produced by a new wet process. Porous scaffolds were prepared by three steps, i.e. solventcasting, compression molding and leaching stage. Factors influencing the compressive strength and the degradation behaviorof the porous scaffold, e.g. weight fraction of pore forming agent-sodium chloride (NaCl), weight ratio of PLLA: β-TCP,the particle size of β-TCP and the porosity, were discussed in details. Rat marrow stromal cells (RMSC) were incorporatedinto the composite by tissue engineering approach. Biological and osteogenesis potential of the composite scaffold weredetermined with MTT assay, alkaline phosphatase (ALP) activity and bone osteocalcin (OCN) content evaluation. Resultsshow that PLLA/β-TCP bioactive porous scaffold has good mechanical and pore structure with adjustable compressive strengthneeded for surgery. RMSCs seeding on porous PLLA/β-TCP composite behaves good seeding efficacy, biocompatibility andosteoinductive potential. Osteoprogenitor cells could well penetrate into the material matrix and begin cell proliferation andosteogenic differentiation. Osseous matrix could be formed on the surface of the composite after culturing in vitro. It isexpected that the PLLA/β-TCP porous composites are promising scaffolds for bone tissue engineering in prosthesis surgery.展开更多
A rotating disk contactor（RDC）was designed to perform L-lactic acid fermentation with afilamentous fungi,Rhizopus oryzae,which was immobilized on the surfaces of the rotating discs.Thebioreactor was operated using r...A rotating disk contactor（RDC）was designed to perform L-lactic acid fermentation with afilamentous fungi,Rhizopus oryzae,which was immobilized on the surfaces of the rotating discs.Thebioreactor was operated using repeated-batch method as well as continuous feeding method.Ananionic resin,D354,slightly basic in nature and of high selectivity and capacity was chosen for lacticacid separation.A coupled process of L-lactic acid fermentation and ion-exchange separation wasevaluated experimentally.The results indicated that the pH value of the fermentation broth could bemaintained at about 3-3.5 without any addition of alkali.The conversion ratio of glucose to L-lacticacid was about 0.7 g·g<sup>-1</sup> and the fermentation rate reached as high as 62.5 g·h<sup>-1</sup>·m<sup>-2</sup>.展开更多
Immobilized Rhizopus oryzae culturing may be a solution to the inhibited production of L（＋）-lactic acid in submerged fermentation, which is caused by aggregated mycelia floc. In the present study, a R. oryzae muta...Immobilized Rhizopus oryzae culturing may be a solution to the inhibited production of L（＋）-lactic acid in submerged fermentation, which is caused by aggregated mycelia floc. In the present study, a R. oryzae mutant （RL6041） with a 90% conversion rate of glucose into L-lactic acid was obtained by N＋ implantation under the optimized conditions of a beam energy of 15 keV and a dose of 2.6 ×10^15 ions/cm^2. Using polyurethane foam as the immobilization matrix, the optimal L-lactic acid production conditions were determined as 4 mm polyurethane foam, 150 r/min, 50 g/L ～ 80 g/L of initial glucose, 38℃ and pH 6.0. 15-cycle repeated productions of L-lactic acid by immobilized RL6041 were performed under the optimized culturing conditions and over 80% of the glucose was converted into L-lactic acid in 30 hours on average. The results show that immobilized RL6041 is a promising candidate for continuous L-lactic acid production.展开更多
PDLLA/CHI/β-TCP/NGF composite films were prepared by a solvent evaporation method. The degradation characteristics of the poly （d, l-lactide） composite films were studied in vitro and in vivo. The acidity produced ...PDLLA/CHI/β-TCP/NGF composite films were prepared by a solvent evaporation method. The degradation characteristics of the poly （d, l-lactide） composite films were studied in vitro and in vivo. The acidity produced by poly （d, l-lactide） materials was not obvious. Adding chitosan and β-TCP can relieve the acidity problem and improve strength performance of films. The NGF has influences on the degradation characteristics of films. It is verified that PDLLA/CHI/β-TCP/NGF composite films prepared by solvent evaporation method have excellent degradation characteristics. It can be used as a perfect biomaterial for repairing nerve injuries.展开更多
L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphen...L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphenol-A epoxy resin as chain extending agent. HVMTs were obtained by sulfuric acid-leaching of lamellar vermiculites (VMTs). The effects of sulfuric acid leaching on the VMTs structure were characterized by X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance(29Si NMR), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). FTIR, FE-SEM, and TGA were used to characterize the reaction activity of HVMTs. The results indicated that VMTs with increased hydroxyl groups had been successfully obtained and could react with -COOH of the reaction system. The amount of L-LA based copolymer grafted on the surface of HVMTs was more than 22%. The onset decomposition temperature of L-LA based copolymer grafted on the surface of HVMTs was 30℃ higher than that of free L-LA based copolymer.展开更多
Monomethoxy poly(ethylene glycol)-block-poly(D,L-lactic acid)(PEG-PLA)is a typical amphiphilic di-block copolymer widely used as a nanoparticle carrier(nanocarrier)in drug delivery.Understanding the in vivo fate of PE...Monomethoxy poly(ethylene glycol)-block-poly(D,L-lactic acid)(PEG-PLA)is a typical amphiphilic di-block copolymer widely used as a nanoparticle carrier(nanocarrier)in drug delivery.Understanding the in vivo fate of PEG-PLA is required to evaluate its overall safety and promote the development of PEG-PLA-based nanocarrier drug delivery systems.However,acquiring such understanding is limited by the lack of a suitable analytical method for the bioassay of PEG-PLA.In this study,the pharmacokinetics,biodistribution,metabolism and excretion of PEG-PLA were investigated in rat after intravenous administration.The results show that unchanged PEG-PLA is mainly distributed to spleen,liver,and kidney before being eliminated in urine over 48 h mainly(>80%)in the form of its PEG metabolite.Our study provides a clear and comprehensive picture of the in vivo fate of PEG-PLA which we anticipate will facilitate the scientifc design and safety evaluation of PEG-PLA-based nanocarrier drug delivery systems and thereby enhance their clinical development.展开更多
Aim:This animal study aims to examine the efficacy and safety of poly-D,L-lactic acid(PDLLA)microspheres as subdermal fillers.Methods:Thirty 2-week-old male Sprague Dawley rats were used as test animals,and 0.5 mL fil...Aim:This animal study aims to examine the efficacy and safety of poly-D,L-lactic acid(PDLLA)microspheres as subdermal fillers.Methods:Thirty 2-week-old male Sprague Dawley rats were used as test animals,and 0.5 mL filler solutions were injected into the subdermal tissues on their backs.Groups of five rats were randomly selected and sacrificed for examination on the 2nd,4th,8th,12th,16th,and 20th weeks after injection.Clinical and histological examinations were performed via the hematoxyline-eosin and immunohistochemical(IHC)staining of injected sites after collecting the injected masses.The body weights of the rats were measured,and the presence of filler substance in other organs was determined.Results:Injected volumes were stable from the 2nd to the 20th week after injection,and no abnormalities were observed around the injection sites.The injected substance did not migrate to the surrounding tissues.In IHC staining experiments,myofibroblasts were observed from the 2nd week,and collagen was detected from the 4th week.Myofibroblast was observed in the spaces between and inside the microspheres in the 8th week after injection,whereas type I collagen was found between and inside the microspheres at 8th and 12th weeks,respectively.Conclusion:The animal experiments confirm the efficacy and safety of injectable PDLLA as a subdermal filler.展开更多
Objective：To observe the changing of biomechanical features during the degradation course of poly-D,L-lactic acid （PDLLA） rods in vivo and in vitro and to evaluate its value as an internal fixation material. Metho...Objective：To observe the changing of biomechanical features during the degradation course of poly-D,L-lactic acid （PDLLA） rods in vivo and in vitro and to evaluate its value as an internal fixation material. Methods ：PDLLA rods were emerged into PBS simultaneous body fluid with constant temperature of 37℃ and the rods were embedded into muscle tissue of 20 rabbits for degradation in vitro and in vivo . The rods were taken out in 2, 4, 6, 8 and 12 weeks. Biomechanical features of bending, shearing and axial compression strength, rigidity and elastic modulus were observed during the degradation course. Statistical method was used to test the changes of biomechanical parameters. Results： （1）There was similar changes of bending, compressive, shearing strength and bending, compressive and shearing rigidity of the PDLLA rods between in vivo and in vitro. （2）Bending, compressive, shearing strength decreased 33%, 18 % and 43 % respectively within the first stage of the degradation, and after 6 weeks of degradation, they decreased slowly. （3）Elastic modulus, bending, compressive and shearing rigidity.decreased sharply during the 6 weeks of degradation, with a drop of 22%, 39% and 30% respectively, and after 8 weeks, they decreased slowly. Even after 12 weeks of degradation, the strength of the rods was still higher than that of sponge bone. Conclusion： During the degradation of the material, the strength and rigidity of PDLLA rods can meet the need of fracture fixation of cancellous bones.展开更多
Dry yeast cells （DYC） were used as a cheap nitrogen source to replace expensive yeast extract （YE） for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch （200 g. L1） was converted to L-l...Dry yeast cells （DYC） were used as a cheap nitrogen source to replace expensive yeast extract （YE） for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch （200 g. L1） was converted to L-lactic acid by simultaneous saccharification and fermentation using Bacillus coagulans WCP10-4 at 50℃ in the presence of 20g·L-1 of DYC, giving 148.1 g·L-1 of L- lactic acid at 27 h with a productivity of 5.5 g·L-1·h-1 and a yield of 92%. In contrast, 154.4 g·L-1 of lactic acid was produced at 24 h with a productivity of 6.4 g·L-1. hl and a yield of 96% when equal amount of YE was used under the same conditions. Use of pre-autolyzed DYC at 50℃ for overnight slightly improved the lactic acid titer （154.5g·L-1） and productivity （7.7g·L-1·h-1） but gave the same yield （96%）.展开更多
文摘Poly (lactic acid) (PLA) was synthesized by microwave-assisted ring-opening polymerization of D, L-lactide with stannous octanoate (SnOct(2)) as catalyst. Its weight-average molar mass (M-w) ranged from 39000 to 67000 and the polydispersity index from 1.3 to 1.7. The polymerization rate was much faster than that of the conventional thermal polymerization. A degradation of newly formed PLA in reaction mixture by microwave irradiation was observed.
基金Supported by the National Natural Science Foundation of China.
文摘Repeated-batch and continuous production of L-lactic acid by immobilized Rhizopusoryzae with calcium alginate entrapment method in a three-phase fluidized-bed bioreactor was stud-ied.The operation conditions were optimized.The productivity based on total reactor volume wasabout 3 times higher than that with free cells in a traditional stirred tank bioreactor.A mathemat-ical model was proposed and the model predictions were in good agreement with the experimentaldat.
基金This study was supported by the National Natural Science Foundation of China(No.30270395 and 30300084)the National"863"Project(No.2003AA32X210).
文摘A novel poly（d, /-lactic acid） （PDLLA） based biomimetic polymer was synthesized by grafting maleic anhydride, butanediamine and arg-gly-asp-ser （RGDS） peptides onto the backbone of PDLLA, aiming to overcome the acidity and auto-accelerating degradation of PDLLA during degradation and to improve its biospecificity and biocompatibility. The synthetic copolymer was characterized by FTIR, ^13C NMR and amino acid analyzer （AAA）.
文摘The goal of this study is to design and synthesize a linear segmented shape memory poly（urethane-urea） （SMPUU） that possesses near-body-temperature shape memory temperature （Ttran） and enhanced mechanical properties by incorporating flexible poly（ethylene glycol） 400 （PEG400） to form poly（D,L-lactic acid）-based macro- diols （PDLLA-PEG400-PDLLA） and then rigid piperazine （PPZ） as a chain extender to form the desired SMPUUs （PEG400-PUU-PPZ）. PEG400 increased Mn while maintaining a lower Tg of PDLLA-PEG400-PDLLA, which together with PPZ improved the mechanical properties of PEG400-PUU-PPZ. The obtained optimum SMPUU with enhanced mechanical properties （O＇y = 24.28 MPa; zf = 698%; Uf = 181.5 MJIm3） and a Tg of 40.62~C exhibited sound shape memory properties as well, suggesting a promising SMPUU for in vivo biomedical applications.
文摘Biodegradable chitosan-g-poly (D, L-lactic acid) copolymers were prepared via two methods. (1) The lactide was grafted onto hydroxyl groups of chitosan by using macromolecular initiator sodium of trimethylsilyl-chitosan, (2) poly (D,L-lactic acid)(PLA) with low molecular weight can be linked to the amino group by coupling activated PLA to trimethylsilyl-chitosan. Two graft copolymers had hydrophilic-hydrophobic character and can be applied as carriers for drug delivery.
基金This study was financially supported by 863 Hj-Tech ResearchDevelopment Program of China(2002AA326080)The Fund for Youth Teacher of Education Mlinistry of China(2002123).
文摘To develop a novel degradable poly (L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) bioactive materials for bone tissueengineering, β-TCP powder was produced by a new wet process. Porous scaffolds were prepared by three steps, i.e. solventcasting, compression molding and leaching stage. Factors influencing the compressive strength and the degradation behaviorof the porous scaffold, e.g. weight fraction of pore forming agent-sodium chloride (NaCl), weight ratio of PLLA: β-TCP,the particle size of β-TCP and the porosity, were discussed in details. Rat marrow stromal cells (RMSC) were incorporatedinto the composite by tissue engineering approach. Biological and osteogenesis potential of the composite scaffold weredetermined with MTT assay, alkaline phosphatase (ALP) activity and bone osteocalcin (OCN) content evaluation. Resultsshow that PLLA/β-TCP bioactive porous scaffold has good mechanical and pore structure with adjustable compressive strengthneeded for surgery. RMSCs seeding on porous PLLA/β-TCP composite behaves good seeding efficacy, biocompatibility andosteoinductive potential. Osteoprogenitor cells could well penetrate into the material matrix and begin cell proliferation andosteogenic differentiation. Osseous matrix could be formed on the surface of the composite after culturing in vitro. It isexpected that the PLLA/β-TCP porous composites are promising scaffolds for bone tissue engineering in prosthesis surgery.
基金Supported by the National Natural Science Foundation of China.
文摘A rotating disk contactor（RDC）was designed to perform L-lactic acid fermentation with afilamentous fungi,Rhizopus oryzae,which was immobilized on the surfaces of the rotating discs.Thebioreactor was operated using repeated-batch method as well as continuous feeding method.Ananionic resin,D354,slightly basic in nature and of high selectivity and capacity was chosen for lacticacid separation.A coupled process of L-lactic acid fermentation and ion-exchange separation wasevaluated experimentally.The results indicated that the pH value of the fermentation broth could bemaintained at about 3-3.5 without any addition of alkali.The conversion ratio of glucose to L-lacticacid was about 0.7 g·g<sup>-1</sup> and the fermentation rate reached as high as 62.5 g·h<sup>-1</sup>·m<sup>-2</sup>.
基金Key 863 fund of China(No.2006AA020102)the Key Technologies Research and Development Programme of Anhui Province(07010202076)
文摘Immobilized Rhizopus oryzae culturing may be a solution to the inhibited production of L（＋）-lactic acid in submerged fermentation, which is caused by aggregated mycelia floc. In the present study, a R. oryzae mutant （RL6041） with a 90% conversion rate of glucose into L-lactic acid was obtained by N＋ implantation under the optimized conditions of a beam energy of 15 keV and a dose of 2.6 ×10^15 ions/cm^2. Using polyurethane foam as the immobilization matrix, the optimal L-lactic acid production conditions were determined as 4 mm polyurethane foam, 150 r/min, 50 g/L ～ 80 g/L of initial glucose, 38℃ and pH 6.0. 15-cycle repeated productions of L-lactic acid by immobilized RL6041 were performed under the optimized culturing conditions and over 80% of the glucose was converted into L-lactic acid in 30 hours on average. The results show that immobilized RL6041 is a promising candidate for continuous L-lactic acid production.
文摘PDLLA/CHI/β-TCP/NGF composite films were prepared by a solvent evaporation method. The degradation characteristics of the poly （d, l-lactide） composite films were studied in vitro and in vivo. The acidity produced by poly （d, l-lactide） materials was not obvious. Adding chitosan and β-TCP can relieve the acidity problem and improve strength performance of films. The NGF has influences on the degradation characteristics of films. It is verified that PDLLA/CHI/β-TCP/NGF composite films prepared by solvent evaporation method have excellent degradation characteristics. It can be used as a perfect biomaterial for repairing nerve injuries.
基金National High-Tech Research and Development Program of China ( 863 Program ) ( No. 2007AA03Z336) Program for New Century Excellent Talents in University,China ( No. NCET-07-0174) +1 种基金National Natural Science Foundations of China ( No. 21074021,No.50673018) The Fundamental Research Funds for the Central Universities ( No. 2011D10543)
文摘L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphenol-A epoxy resin as chain extending agent. HVMTs were obtained by sulfuric acid-leaching of lamellar vermiculites (VMTs). The effects of sulfuric acid leaching on the VMTs structure were characterized by X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance(29Si NMR), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). FTIR, FE-SEM, and TGA were used to characterize the reaction activity of HVMTs. The results indicated that VMTs with increased hydroxyl groups had been successfully obtained and could react with -COOH of the reaction system. The amount of L-LA based copolymer grafted on the surface of HVMTs was more than 22%. The onset decomposition temperature of L-LA based copolymer grafted on the surface of HVMTs was 30℃ higher than that of free L-LA based copolymer.
基金supported by the National Natural Science Foundation of China(Grant Nos.81872831 and 82030107)the National Science and Technology Major Projects for signifcant new drugs creation of the 13th fve-year plan(2017ZX09101001 and 2018ZX09721002007,China)。
文摘Monomethoxy poly(ethylene glycol)-block-poly(D,L-lactic acid)(PEG-PLA)is a typical amphiphilic di-block copolymer widely used as a nanoparticle carrier(nanocarrier)in drug delivery.Understanding the in vivo fate of PEG-PLA is required to evaluate its overall safety and promote the development of PEG-PLA-based nanocarrier drug delivery systems.However,acquiring such understanding is limited by the lack of a suitable analytical method for the bioassay of PEG-PLA.In this study,the pharmacokinetics,biodistribution,metabolism and excretion of PEG-PLA were investigated in rat after intravenous administration.The results show that unchanged PEG-PLA is mainly distributed to spleen,liver,and kidney before being eliminated in urine over 48 h mainly(>80%)in the form of its PEG metabolite.Our study provides a clear and comprehensive picture of the in vivo fate of PEG-PLA which we anticipate will facilitate the scientifc design and safety evaluation of PEG-PLA-based nanocarrier drug delivery systems and thereby enhance their clinical development.
基金This work was supported by Regen Biotech,Inc.,Seoul,South Korea.
文摘Aim:This animal study aims to examine the efficacy and safety of poly-D,L-lactic acid(PDLLA)microspheres as subdermal fillers.Methods:Thirty 2-week-old male Sprague Dawley rats were used as test animals,and 0.5 mL filler solutions were injected into the subdermal tissues on their backs.Groups of five rats were randomly selected and sacrificed for examination on the 2nd,4th,8th,12th,16th,and 20th weeks after injection.Clinical and histological examinations were performed via the hematoxyline-eosin and immunohistochemical(IHC)staining of injected sites after collecting the injected masses.The body weights of the rats were measured,and the presence of filler substance in other organs was determined.Results:Injected volumes were stable from the 2nd to the 20th week after injection,and no abnormalities were observed around the injection sites.The injected substance did not migrate to the surrounding tissues.In IHC staining experiments,myofibroblasts were observed from the 2nd week,and collagen was detected from the 4th week.Myofibroblast was observed in the spaces between and inside the microspheres in the 8th week after injection,whereas type I collagen was found between and inside the microspheres at 8th and 12th weeks,respectively.Conclusion:The animal experiments confirm the efficacy and safety of injectable PDLLA as a subdermal filler.
文摘Objective：To observe the changing of biomechanical features during the degradation course of poly-D,L-lactic acid （PDLLA） rods in vivo and in vitro and to evaluate its value as an internal fixation material. Methods ：PDLLA rods were emerged into PBS simultaneous body fluid with constant temperature of 37℃ and the rods were embedded into muscle tissue of 20 rabbits for degradation in vitro and in vivo . The rods were taken out in 2, 4, 6, 8 and 12 weeks. Biomechanical features of bending, shearing and axial compression strength, rigidity and elastic modulus were observed during the degradation course. Statistical method was used to test the changes of biomechanical parameters. Results： （1）There was similar changes of bending, compressive, shearing strength and bending, compressive and shearing rigidity of the PDLLA rods between in vivo and in vitro. （2）Bending, compressive, shearing strength decreased 33%, 18 % and 43 % respectively within the first stage of the degradation, and after 6 weeks of degradation, they decreased slowly. （3）Elastic modulus, bending, compressive and shearing rigidity.decreased sharply during the 6 weeks of degradation, with a drop of 22%, 39% and 30% respectively, and after 8 weeks, they decreased slowly. Even after 12 weeks of degradation, the strength of the rods was still higher than that of sponge bone. Conclusion： During the degradation of the material, the strength and rigidity of PDLLA rods can meet the need of fracture fixation of cancellous bones.
文摘Dry yeast cells （DYC） were used as a cheap nitrogen source to replace expensive yeast extract （YE） for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch （200 g. L1） was converted to L-lactic acid by simultaneous saccharification and fermentation using Bacillus coagulans WCP10-4 at 50℃ in the presence of 20g·L-1 of DYC, giving 148.1 g·L-1 of L- lactic acid at 27 h with a productivity of 5.5 g·L-1·h-1 and a yield of 92%. In contrast, 154.4 g·L-1 of lactic acid was produced at 24 h with a productivity of 6.4 g·L-1. hl and a yield of 96% when equal amount of YE was used under the same conditions. Use of pre-autolyzed DYC at 50℃ for overnight slightly improved the lactic acid titer （154.5g·L-1） and productivity （7.7g·L-1·h-1） but gave the same yield （96%）.
