DL-lactic Acid Research Articles

Bone tissue engineering by using a combination of polymer/Bioglass composites with human adipose-derived stem cells

Translational research in bone tissue engineering is essential for "bench to bedside" patient benefit. However, the ideal combination of stem cells and biomaterial scaffolds for bone repair/regeneration is still unclear. The aim of this study is to investigate the osteogenic capacity of a combination of poly(DL-lactic acid) (PDLLA) porous foams containing 5 wt% and 40 wt% of Bioglass particles with human adipose-derived stem cells (ADSCs) in vitro and in vivo. Live/dead fluorescent markers, confocal microscopy and scanning electron microscopy showed that PDLLA/Bioglass porous scaffolds supported ADSC attachment, growth and osteogenic differentiation, as confirmed by enhanced alkaline phosphatase (ALP) activity. Higher Bioglass content of the PDLLA foams increased ALP activity compared with the PDLLA only group. Extracellular matrix deposition after 8 weeks in the in vitro cultures was evident by Alcian blue/Sirius red staining. In vivo bone formation was assessed by using scaffold/ADSC constructs in diffusion chambers transplanted intraperitoneally into nude mice and recovered after 8 weeks. Histological and immunohistochemical assays indicated significant new bone formation in the 40 wt% and 5 wt% Bioglass constructs compared with the PDLLA only group. Thus, the combination of a well-developed biodegradable bioactive porous PDLLA/Bioglass composite scaffold with a high-potential stem cell source (human ADSCs) could be a promising approach for bone regeneration in a clinical setting.

Purification, characterization, and cloning of the gene for a biodegradable plastic-degrading enzyme from Paraphoma-related fungal strain B47-9

Paraphoma-related fungal strain B47-9 secreted a biodegradable plastic (BP)-degrading enzyme which amounted to 68 % (w/w) of the total secreted proteins in a culture medium containing emulsified poly(butylene succinate-co-adipate) (PBSA) as sole carbon source. The gene for this enzyme was found to be composed of an open reading frame consisting of 681 nucleotides encoding 227 amino acids and two introns. Southern blot analysis showed that this gene exists as a single copy. The deduced amino acid sequence suggested that this enzyme belongs to the cutinase (E.C.3.1.1.74) family; thus, it was named P araphoma-related fungus cutinase-like enzyme (PCLE). It degraded various types of BP films, such as poly(butylene succinate), PBSA, poly(butylene adipate-co-terephthalate), poly(ε-caprolactone), and poly(DL-lactic acid). It has a molecular mass of 19.7 kDa, and an optimum pH and temperature for degradation of emulsified PBSA of 7.2 and 45 °C, respectively. Ca(2+) ion at a concentration of about 1.0 mM markedly enhanced the degradation of emulsified PBSA.

Ibuprofen Nanoparticles for Oral Delivery: Proof of Concept

Background: Using nanoparticles to improve non-steroidal anti-inflammatory drugs therapeutic profile is an interesting approach, especially concerning their gastric toxicity. Objective: The aim of this work was to present a proof of concept for a nanoparticulate formulation composed of a biodegradable polymer poly (DL-lactic acid) (PLA) meant for oral delivery of ibuprofen (IBU) to systemic circulation with reduced gastric toxicity. Materials and methods: IBU-loaded nanoparticles composed of PLA and poloxamer 188 were prepared by an emulsion/solvent diffusion method. The particles obtained were characterized for size, zeta potential and morphology, as well as encapsulation efficiency. Nanoparticles were given to Wistar rats at an equivalent dose of 12 mg/kg (t.i.d.) of ibuprofen for a period of 10 days. Both concentration of IBU in the plasma and toxicity in different tissues were evaluated. Results: Nanoparticles displayed a size of 281.1 ± 66.7 nm with a zeta potential of -4.3 mV. Scanning electron microscopic images showed spherical shape particles with low polydispersity index. IBU concentration in blood samples indicated that nanoparticles were able to deliver IBU to systemic circulation. A significant reduction in toxicity was observed for nanoparticles in gastric mucosa compared to free ibuprofen. This may be due to controlled release of IBU from the nanoparticles, which decreases the mucosal contact to IBU. In summary, we designed a proof of concept for PLA nanoparticles as suitable carrier for IBU allowing reduced gastric toxicity of the drugs. This strategy can eventually be applied to other non-steroidal anti-inflammatory drugs.

Effect of Different Initial pH on the Storage Characteristics and Shelf Life of Liquid Diet for Suckling and Weanling Piglets

An experiment was conducted to investigate the effect of different initial pH on the storage characteristics and shelf life of liquid diet. 45 polypropylene bags were allotted to treatments 1, 2 and 3 on average, 100 g diet and 200 g water were placed into each polypropylene bag, food-grade DL-lactic acid was added to each bag at a rate of 0.0 mL in treatment 1, 1.2 mL in treatment 2 and 4.7 mL in treatment 3, air was artificially expelled from each bag prior to heat-sealing. All bags were placed into a cage, cooked with steam at 90°C for 30 min under normal pressure, then taken out and stored from day 0 to 60 at room temperature. Results indicated that liquid diet in treatment 3 achieved the highest total sensory scores, the pH value had a tendency to decrease and the bacteria count had a tendency to increase in the liquid diet with the advancing of storage time with the advancing of storage time, lowering the initial pH of liquid diet decreased the bacteria count, the AFB1 and ZEN concentrations and increased the starch gelatinization degree from day 30 to 60, liquid diet in treatment 3 had a lower (P<0.01) bacteria count and a higher (P<0.05) starch gelatinization degree at day 30 and 45 than liquid diet in treatment 1. In conclusion, lowering the initial pH of liquid diet with lactic acid to pH 4 could effectively improve the storage characteristics and shelf life of liquid diet.

Characterization of bovine ruminal and equine cecal microbial populations enriched for enhanced nitro-toxin metabolizing activity

The nitrotoxins 3-nitro-1-propionic acid (NPA) and 3-nitro-1-propanol (NPOH) are produced by a wide variety of leguminous plants, including over 150 different species and varieties of Astragalus potentially grazed by livestock. These toxins are known to be detoxified by at least one ruminal bacterium but detoxification by bacteria from other gut habitats is not known. In the present study, mixed populations of bovine ruminal and equine cecal microbes were enriched for NPA-metabolizing bacteria via consecutive 24–72 h culture in a basal minimal rumen fluid-based medium supplemented with 4.2 mM NPA and H2 as the energy source. Rates of NPA metabolism by the respective populations increased from 58.4 ± 4.8 and 8.6 ± 11.6 nmol NPA/mL per h during initial culture to 88.9 ± 30.6 and 50.2 ± 30.9 nmol NPA/mL per h following enrichment. Results from 3-tube most probable number tests indicated that numbers of NPA-degrading microbes increased 2.1 and 1.8 log10 units during enrichment from numbers measured pre-enrichment (3.9 × 103 and 4.3 × 101 cells/mL for ruminal and equine cecal populations, respectively). Hydrogen, formate, and to a lesser extent, dl-lactic acid, served as electron donors to the enriched populations and CO2 or formate were needed to maintain high rates of NPA-metabolism. The NPA-enriched populations were able to metabolize nitrate which, being a preferred electron acceptor, was antagonistic to NPA metabolism. Supplemental NPA was inhibitory to methanogenesis. Fermentation balance estimates indicated that only 47.6% of carbon available in potential substrates was recovered in headspace CO2, volatile fatty acids or unmetabolized NPA after 72 h incubation of NPA-enriched populations that had metabolized 98% of 8.4 mM added NPA. Overall, these results reveal low level carriage of NPA-metabolizing, CO2 or formate-requiring bacterial populations in the equine cecum yet support the concept that Denitrobacterium detoxificans-like organisms may well be the functional agents of NPA and NPOH detoxification in the populations studied here.

Accumulated Polymer Degradation Products as Effector Molecules in Cytotoxicity of Polymeric Nanoparticles

Polymeric nanoparticles (PNPs) are a promising platform for drug, gene, and vaccine delivery. Although generally regarded as safe, the toxicity of PNPs is not well documented. The present study investigated in vitro toxicity of poly-ε-caprolactone, poly(DL-lactic acid), poly(lactide-cocaprolactone), and poly(lactide-co-glycide) NPs and possible mechanism of toxicity. The concentration-dependent effect of PNPs on cell viability was determined in a macrophage (RAW 264.7), hepatocyte (Hep G2), lung epithelial (A549), kidney epithelial (A498), and neuronal (Neuro 2A) cell lines. PNPs show toxicity at high concentrations in all cell lines. PNPs were efficiently internalized by RAW 264.7 cells and stimulated reactive oxygen species and tumor necrosis factor-alpha production. However, reactive nitrogen species and interleukin-6 production as well as lysosomal and mitochondrial stability remained unaffected. The intracellular degradation of PNPs was determined by monitoring changes in osmolality of culture medium and a novel fluorescence recovery after quenching assay. Cell death showed a good correlation with osmolality of culture medium suggesting the role of increased osmolality in cell death.

Effect of fermented moist feed on performance, gut bacteria and gut histo-morphology in broilers

1. Fermented feed has been shown to be beneficial in pig nutrition as a tool to reduce gut microbial disorders. Experiments with fermented feed in poultry are scarce, probably because of the belief that wet feed is less suitable for this species and causes wet litter.2. A total of 280 one-d-old Ross 308 chickens were used in a completely randomised design with two dietary treatments (7 replicates of 20 birds/treatment); air-dry feed versus the same feed in moist form (water:feed ratio of 1.3:1, on a weight basis), inoculated with Lactobacillus plantarum NCIMB 40087 (9 log10 CFU/kg feed) and batch-fermented for 48 h at 26°C. The birds were given starter (d 0–13), grower (d 4–26) and finisher (d 27–39) diets ad libitum. At the end of the grower and finisher period, two birds per pen were removed to sample intestinal contents for cultivating bacteria and intestinal tissue to determine villus height and crypt depth.3. Fermented moist feed (FMF) batches showed good characteristics, with a pH between 3.9 and 4.4 and DL-lactic acid between 137 and 286 mmol/l. Daily feed intake and gain were reduced considerably in the FMF group in the starter (–40 and –44%, respectively) and grower (–23 and –16%) period, though in the finisher period these birds performed better, with an improved feed utilisation. Concomitant with the latter, villus height at the mid-jejunum and mid-ileum on d 39 was higher (+22.6% and +16.0%). Significantly more Lactobacilli and less coliforms were found in the foregut and less Streptococci in ileum and caeca of birds given FMF.4. This trial showed that FMF was detrimental for early bird growth but affected beneficially feed efficiency, the composition of the gut bacteria and villus height in the small intestine in the finisher period in broilers.

Intestinimonas butyriciproducens gen. nov., sp. nov., a butyrate-producing bacterium from the mouse intestine

A Gram-positive, spore-forming, non-motile, strictly anaerobic rod-shaped bacterium was isolated from the caecal content of a TNF(deltaARE) mouse. The isolate, referred to as strain SRB-521-5-I(T), was originally cultured on a reduced agar medium containing yeast extract, rumen fluid and lactic acid as main energy and carbon sources. Phylogenetic analysis of partial 16S rRNA genes revealed that the species most closely related to strain SRB-521-5-I(T) were Flavonifractor plautii and Pseudoflavonifractor capillosus (<95 % sequence similarity; 1436 bp). In contrast to F. plautii and P. capillosus, strain SRB-521-5-I(T) contained a substantial amount of C18 : 0 dimethylacetal. Additional major fatty acids were C14 : 0 methyl ester, C16 : 0 dimethylacetal and C18 : 0 aldehyde. Strain SRB-521-5-I(T) differed in its enzyme profile from F. plautii and P. capillosus by being positive for dextrin, maltotriose, turanose, dl-lactic acid and d-lactic acid methyl ester but negative for d-fructose. In reduced Wilkins-Chalgren-Anaerobe broth, strain SRB-521-5-I(T) produced approximately 8 mM butyrate and 4 mM acetate. In contrast to F. plautii, the strain did not metabolize flavonoids. It showed intermediate resistance towards the antibiotics ciprofloxacin, colistin and tetracycline. Based on genotypic and phenotypic characteristics, we propose the name Intestinimonas butyriciproducens gen. nov., sp. nov. to accommodate strain SRB-521-5-I(T) ( = DSM 26588(T) = CCUG 63529(T)) as the type strain.

Obtaining of new magnetic nanocomposites based on modified polysaccharide

The study presents the preparation of some composite materials with magnetic properties by two different encapsulation methods of magnetite (Fe3O4) in a polymer matrix based on carboxymethyl starch-g-polylactic acid (CMS-g-PLA). The copolymer matrix used to obtain the magnetic nanocomposites was synthesized by grafting reaction of carboxymethyl starch (CMS) with d,l-lactic acid (DLLA), in the presence of Sn octanoate [Sn(Oct)2] as catalyst. Magnetite was obtained by co-precipitation from aqueous salt solutions FeCl2/FeCl3 (molar ratio 1/2). The magnetic composites were prepared by precipitation method in acetone (non-solvent) of the DMSO solutions of magnetite and copolymer, and synthesis in situ of the nanocomposites. In the first case, the particle size measured by DLS-technique was 168nm, and the magnetization was 46.82emu/g, while after in situ synthesis, the composite materials showed smaller size (141nm), but the magnetization was reduced (3.04emu/g). The higher magnetization in the first case is due to the great degree of encapsulation of the magnetite, which was about 43.4wt.%, compared to 4.37wt.% for the in situ synthesis (determined by thermogravimetry). The CMS-g-PLA copolymer, magnetite, and the nanocomposites were characterized by infrared spectroscopy (FTIR), near infrared chemical imagistic (NIR-CI), dynamic light scattering (DLS) technique, X-ray diffraction (WAXD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and thermal analyses. Since the polymer matrix and magnetite are biodegradable and biocompatible, the magnetic nanocomposites can be used for conjugation of some drugs. The polymer matrix CMS-g-PLA acts as a shell, and vehicle for the active component, whereas magnetite is the component which makes targeting possible by external magnetic field manipulation.

Determination of the Interfacial Rheological Properties of a Poly(DL-lactic acid)-Encapsulated Contrast Agent Using In Vitro Attenuation and Scattering

The stabilizing encapsulation of a microbubble-based ultrasound contrast agent (UCA) critically affects its acoustic properties. Polymers, which behave differently from materials commonly used (i.e., lipids or proteins) for monolayer encapsulation, have the potential for better stability and improved control of encapsulation properties. Air-filled microbubbles coated with poly(DL-lactic acid) (PLA) are characterized here using in vitro acoustic experiments and several models of encapsulation. The interfacial rheological properties of the encapsulation are determined according to each model using attenuation of ultrasound through a suspension of microbubbles. Then the model predictions are compared with scattered non-linear (sub- and second harmonic) responses. For this microbubble population (average diameter, 1.9 μm), the peak in attenuation measurement indicates a weighted-average resonance frequency of 2.5–3 MHz, which, in contrast to other encapsulated microbubbles, is lower than the resonance frequency of a free bubble of similar size (diameter, 1.9 μm). This apparently contradictory result stems from the extremely low surface dilational elasticity (around 0.01–0.07 N/m) and the reduced surface tension of the poly(DL-lactic acid) encapsulation, as well as the polydispersity of the bubble population. All models considered here are shown to behave similarly even in the non-linear regime because of the low surface dilational elasticity value. Pressure-dependent scattering measurements at two different excitation frequencies (2.25 and 3 MHz) revealed strongly non-linear behavior with 25–30 dB and 5–20 dB enhancements in fundamental and second-harmonic responses, respectively, for a contrast agent concentration of 1.33 μg/mL in the suspension. Sub-harmonic responses are registered above a relatively low generation threshold of 100–150 kPa, with up to 20 dB enhancement beyond that pressure. Numerical predictions from all models show good agreement with the experimentally measured fundamental response, but not with the experimental second-harmonic response. The characteristic features of sub-harmonic responses and the steady response beyond the threshold are matched well by model predictions. However, prediction of the threshold value depends on estimated properties and size distribution. The variation in size distribution from sample to sample leads to variation in estimates of encapsulation properties: the lowest estimated value for surface dilational viscosity better predicts the sub-harmonic threshold.

5-Fluorouracil-loaded PLA/PLGA PEG–PPG–PEG polymeric nanoparticles: formulation, in vitro characterization and cell culture studies

In this study, 5-FU, a potent anticancer drug, is planned to be delivered via a new and promising drug delivery system, nanoparticles formed with hydrophobic core polymer and triblock copolymers; Poly(DL-lactic acid), Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PLA/PEG-PPG-PEG) and Poly(D,L-lactide–co-glycolide)/Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PLGA/PEG-PPG-PEG) nanoparticles. Particle size range of nanoparticles was found to be between 145 and 198 nm, which would promote the passive targeting of the nanoparticles to tumor cells based on the enhanced permeability and retention (EPR) effect. SEM images revealed all nanoparticles formulations to be spherical and without pores. Zeta potential, yield value and encapsulation efficiencies of 5-FU-loaded nanoparticles were within the range of −11.1 and −13.7 mV, 72.7–87.7% and 83.6–93.9%, respectively. Cumulative release of 5-FU was observed between 90% and 94.4% in all nanoparticle formulations by the end of 72 h, and fitness of release profiles to Higuchi model indicated matrix-controlled diffusion of the 5-FU from polymeric nanoparticles. Cell viability values of the cells treated with 5-FU-loaded nanoparticles were obtained as low as 47% and 52% with tetrazolium dye assay, suggesting that delivery of 5-FU via amphiphilic triblock copolymer nanoparticles would be a promising delivery system because of the EPR effect.

Adsorption of proteins at physiological concentrations on pegylated surfaces and the compatibilizing role of adsorbed albumin with respect to other proteins according to optical waveguide lightmode spectroscopy (OWLS)

In literature, contacts between pegylated compounds and blood proteins are generally discussed in terms of excluded volume-related repulsions although adsorption and compatibility have been reported for some of these proteins occasionally. The major problem to investigate the behavior of blood in contact with pegylated surfaces is the complexity of the medium and especially the presence of albumin in large excess. In a model approach, optical waveguide lightmode spectroscopy (OWLS) was used to monitor the fate of albumin, fibrinogen, and γ-globulins at physiological concentrations in pH = 7.4 isotonic HEPES buffer after contact with SiTiO2 chips coated with diblock poly(DL-lactic acid)-block-poly(ethylene oxide)s and triblock poly(DL-lactic acid)-block-poly(ethylene oxide)-block-poly(DL-lactic acid) copolymers. Corresponding homopolymers were used as controls. The three protein systems were investigated separately, as a mixture and when added successively according to different orders of addition. OWLS gave access to the mass and the thickness of adhering protein layers that resist washing with HEPES buffer. Protein depositions were detected regardless of the presence of poly(ethylene glycol) segments on surfaces. Adsorption depended on the protein, on the surface and also on the presence of the other proteins. Unexpectedly any surface coated with a layer of adsorbed albumin prevented deposition of other proteins, including albumin itself. This outstanding finding suggests that it was the presence of albumin adsorbed on a surface, pegylated or not, that made that surface compatible with other proteins. As a consequence, dipping a device to be in contact with the blood of a patient in a solution of albumin could be a very simple means to avoid further protein deposition and maybe platelets adhesion after in vivo implantation.

High glycolic poly (DL lactic co glycolic acid) nanoparticles for controlled release of meropenem

Nanospheres of low molecular weight poly lactic co glycolic acid (PLGA) with high glycolic acid content (10:90) and polylactic acid (PLA) are synthesized and loaded with meropenem, a broad spectrum antibiotic. The loading efficiency of the drug is 82 and 70% in PLGA 10:90 and PLA respectively. The rate of drug release is higher with PLGA 10:90 (3.2μg/s) than with PLA (2.4μg/s). Eighty and 60% of the encapsulated drug is released from the two polymers in 30 days respectively. Initial burst followed by sustained drug release is observed which is mathematically explained using a biphasic model. The drug release from the former polymer leads to two times lower E. coli growth than the release from the latter. The nanoparticles are biocompatible with no significant effect on the viability of 3T3 cells. This study indicates that PLGA 10:90 can be used for the delivery of antibiotics for interim period, especially for post orthopaedic surgeries.

Aequorivita viscosa sp. nov., isolated from an intertidal zone, and emended descriptions of Aequorivita antarctica and Aequorivita capsosiphonis

An aerobic, Gram-stain-negative, short rod-shaped, non-motile and non-sporulating bacterium, designed strain 8-1b(T), was isolated from seaweed collected from the intertidal zone of Zhoushan sea area, East China Sea. Strain 8-1b(T) grew at 4-39 °C (optimum, 28-32 °C) and at pH 6.0-9.5 (optimum, 7.0-8.5), and with 0.5-8% (w/v) NaCl (optimum, 1-3%) and 0.5-10% (w/v) sea salts (optimum, 2-3%). Analysis of 16S rRNA gene sequences revealed that strain 8-1b(T) was related closely to Aequorivita capsosiphonis JCM 15070(T) (96.7% similarity). The DNA G+C content of strain 8-1b(T) was 36.6 mol%. Compared with reference strains, cells of strain 8-1b(T) showed positive activities for H₂S production and utilization of D-mannose, DL-lactic acid, L-asparagine and glycyl L-aspartic acid. The major fatty acids of strain 8-1b(T) were iso-C(15:0), iso-C(17:0) 3-OH, iso-C(15:1) G and iso-C(17:1)ω9c. The main respiratory quinone was menaquinone 6. The polar lipids of strain 8-1b(T) consisted of phosphatidylethanolamine (PE), three uncharacterized aminolipids (AL1-3), four uncharacterized glycolipids (GL1-4) and five uncharacterized lipids (L1-5). Based on the phenotypic and genotypic characterization, strain 8-1b(T) represents a novel species of the genus Aequorivita, for which the name Aequorivita viscosa sp. nov. is proposed. The type strain is strain 8-1b(T) ( =CGMCC 1.11023(T) = JCM 18497(T)). Emended descriptions of Aequorivita antarctica and Aequorivita capsosiphonis are also presented.

Experimentally induced hyperchloremic and dl-lactic acidosis in calves: An attempt to study the effects of oral rehydration on acid-base status

Many diarrheic calves suffer from metabolic acidosis, which is commonly treated by oral rehydration therapy. Oral rehydration solutions can be prepared in water, milk, or milk replacer. Therefore, the aim of the study was to verify dietary effects of water- or milk replacer-based oral rehydration solutions on parameters of acid-base balance in calves with experimentally induced hyperchloremic and dl-lactate acidosis. In 12 calves, hyperchloremic or dl-lactate acidosis was induced by HCl or dl-lactic acid infusions according to protocols outlined in previous literature. Immediately after induction, the calves were fed with milk replacer or water- or milk replacer-based oral rehydration solutions, or remained fasting, respectively. Blood samples were taken to monitor acid-base status over an experimental period of 4h. Using the protocols, all calves revealed a manifest hyperchloremic or dl-lactate acidosis. Because of high infusion volumes, plasma volume was expanded and effects of feeding regimens on blood parameters were rare. Unexpected clinical aberrations occurred after repeated induction of dl-lactate acidosis: all calves developed a thrombophlebitis of the jugular vein, whereas HCl infusion had no effect on endothelium. Induction of acidosis via infusion is not suitable to study dietary effects. A protocol to induce acidosis and dehydration simultaneously is required to duplicate the metabolic conditions of diarrheic calves. In further investigations, attention should be focused on effects of d-lactate or its metabolites on endothelial tissue.

Immobilization of Heparan Sulfate on Electrospun Meshes to Support Embryonic Stem Cell Culture and Differentiation *

As our understanding of what guides the behavior of multi- and pluripotent stem cells deepens, so too does our ability to utilize certain cues to manipulate their behavior and maximize their therapeutic potential. Engineered, biologically functionalized materials have the capacity to influence stem cell behavior through a powerful combination of biological, mechanical, and topographical cues. Here, we present the development of a novel electrospun scaffold, functionalized with glycosaminoglycans (GAGs) ionically immobilized onto the fiber surface. Bound GAGs retained the ability to interact with GAG-binding molecules and, crucially, presented GAG sulfation motifs fundamental to mediating stem cell behavior. Bound GAG proved to be biologically active, rescuing the neural differentiation capacity of heparan sulfate-deficient mouse embryonic stem cells and functioning in concert with FGF4 to facilitate the formation of extensive neural processes across the scaffold surface. The combination of GAGs with electrospun scaffolds creates a biomaterial with potent applicability for the propagation and effective differentiation of pluripotent stem cells.

Studying the Effective Concentration of RGDS on RGDS-Poly(DL-Lactic Acid)

Studying the Effective Concentration of RGDS on RGDS-Poly(DL-Lactic Acid)

Preparation and Characterization of PLGA/PLLA/PDLLA Composite Fiber Membrane Loading Naringin

The composite fiber membranes loading Naringin containing poly(lactide-co-glycolide), L polylactic acid and poly(DL-lactic acid) were prepared via electrostatic spinning. The composite fiber membranes were characterized via scanning electron microscope (SEM), mechanical properties test, contact angle measurement, while the release curve of naringin in vitro was developed via ultra-violet spectrum. The results showed that the fibers with smooth surfaces were in a narrow diameter range. The strength of composite fiber membranes was improved as the content of naringin increasing, while the hydrophobicity of the materials decreased. The release of naringin in vitro was sustained and steady and less initial burst release occurred in the system.

Hydrolytic degradation behavior of stereo multiblock and diblock poly(lactic acid)s: Effects of block lengths

Stereo multiblock and diblock poly(lactic acid)s (PLAs), poly(DL-lactide) (PDLLA), and poly(DL-lactic acid), with block lengths comprising 3.8–61.9 lactyl units were synthesized. The effects of the block length sequence on the hydrolytic degradation behavior were investigated at 37 °C and pH 7.4 using amorphous (quenched) samples of these polymers, in comparison with quenched neat poly(l-lactide) (PLLA), poly(d-lactide) (PDLA), and PLLA/PDLA blend. 13C NMR spectra revealed that chain cleavage during the hydrolytic degradation occurred rapidly on the atactic segments connecting relatively long isotactic l-lactyl and d-lactyl segments. The rates of weight loss and hydrolytic degradation of stereoblock PLAs, PDLLA, and poly(DL-lactic acid) decreased with an increase in the average stereoblock length. The hydrolytic degradation of the stereo multiblock PLAs with average block lengths higher than 27 and 15 lactyl units was suppressed as compared to that of the PLLA/PDLA blend and the neat PLLA or PDLA, respectively. The stereocomplex crystallization occurred during the hydrolytic degradation of stereoblock PLAs and PDLLA with average stereoblock lengths higher than 7 lactyl units, in agreement with the results reported for the stereocomplex crystallization from the melt. The crystallization rate of stereoblock PLAs during the hydrolytic degradation increased on increasing the block length; however the rate of the hydrolytic degradation of the diblock PLA with the highest average stereoblock length was lower than that of the PLLA/PDLA blend.

Synthesis and Properties of New Biodegradable Polyurethane Containing Natural Rubber and Poly(lactic Acid): Effect of NR and PLA Ratio

Biodegradable polyurethane was synthesized using poly(DL-lactic acid) diol and hydroxytelechelic natural rubber as hydroxyl containing precursor, 1,4-butane diol as chain extender, isophorone diisocyanate and dibutyltin dilaurate as catalyst. Poly(DL-lactic acid) diol was prepared by condensation polymerization of DL-lactic acid using 1,4-butane diol as initiator and stannous octoate as catalyst. Hydroxyltelechelic natural rubber synthesized via oxidative degradation of natural rubber and then reduced carbonyl end group to hydroxyl group. Chemical structure of products was characterized by 1H-NMR. Molecular weight and polydispersity determined by SEC. Thermal properties was characterized by DSC and TGA. Segmented polyurethane show two Tgs and two degradation steps corresponding to natural rubber and poly(DL-lactic acid) segment. Polyurethane containing poly(lactic acid) more than 40%mol are become brittle. This result caused by brittle characteristic of PLA. Moreover, mechanical properties increased as content of PLA increased.