Polyactic Acid Research Articles

Measurement of environmental aspect of 3-D printing process using soft computing methods

For improving the environmental performance of the manufacturing industry across the globe, 3-D printing technology should be increasingly adopted as a manufacturing procedure. It is because this technology uses the polymer PLA (Polyactic acid) as a material, which is biodegradable, and saves fuel and reduces waste when fabricating prototypes. In addition, the technology can be located near to industries and fabricates raw material itself, resulting in reduction of transport costs and carbon emission. However, due to its high production cost, 3-D printing technology is not yet being adopted globally. One way of reducing the production cost and improving environmental performance is to formulate models that can be used to operate 3-D printing technology in an efficient way. Therefore, this paper aims to deploy the soft computing methods such as genetic programming (GP), support vector regression and artificial neural network in formulating the laser power-based-open porosity models. These methods are applied on the selective laser sintering (a 3-D printing process) process data. It is found that GP evolves the best model that is able to predict open porosity satisfactorily based on given values of laser power. The laser power-based-open porosity model formulated can assist decision makers in operating the SLS process in an effective and efficient way, thus increasing its viability for being adopted as a manufacturing procedure and paving the way for a sustainable environment across the globe.

충격보강제로 강인화된 PLA와 cellulose ester 블렌드의 상용성 및 모폴로지, 열적, 기계적 특성에 관한 연구

CAB는 광학적 특성이 우수한 생분해성 수지이나 취약한 가공성으로 인해 필름 어플리케이션에 제한되어 있다. 본 실험에서는 비교적 가공성이 우수한 폴리락틱산을 이용하여 CAB의 가공성을 향상시키고, 충격보강제 도입으로 기계적 물성을 보완하고자 하였다. 이전 실험에서 PLA/CAB binary 블렌드의 PLA75CAB25조성이 상용성을 보이는 것을 확인하였으므로 PLA75CAB25 조성에 한하여 충격보강 연구를 수행하였다. 이축압출기를 이용하여 충격보강제를 도입하고, <TEX>$140^{\circ}C$</TEX>(hopper)-<TEX>$200^{\circ}C$</TEX>(die)의 온도 범위에서 200rpm의 속도로 제조하였다. 충격보강제 도입에 따른 상용성을 평가하기 위해 DSC와 FE-SEM을 통해 유리전이온도 거동과 모폴로지를 관찰하였다. 또한 충격보강효과를 확인하기 위해 DMA와 Izod 충격강도 시험기를 이용하여 저장탄성률과 충격강도를 측정하였다. 충격보강제가 10wt%가 도입되었을 때 상용성이 가장 좋았으며, Izod 충격강도가 PLA75CAB25 조성에 비해 4배 이상 향상되었음을 확인하였다. Cellulose acetate butyrate (CAB) is a biodegradable resin with excellent optical properties, but it is difficult to apply film process. In this study, an attempt was made to improve the processability of CAB using polyactic acid and the mechanical properties using an impact modifier. Polylacitc acid (PLA)/Cellulose acetate butyrate (CAB) blends with an impact modifier were prepared using a twin screw extruder. The temperature range was <TEX>$140^{\circ}C$</TEX> to <TEX>$200^{\circ}C$</TEX>, and the screw speed was fixed to 200 rpm. To evaluate the miscibility of impact modified CAB/PLA, the glass transition behavior and morphology were observed by DSC and FE-SEM. The mechanical properties were investigated by dynamic mechanical analysis (DMA) and a Universal Testing Machine (UTM). In addition, the effect of an impact modifier in the polymer matrix was determined using a notched Izod impact strength tester. Finally, the PLA/CAB/impact modifier 75/25/10 ratio was found to be a compatible system. In the 10wt.% impact modifier, the sample had a 4 times higher izod impact strength than the non-toughening composition.

Nanotechnology-based drug delivery in mucosal immune diseases: hype or hope?

Nanotechnology-based drug delivery in mucosal immune diseases: hype or hope?

Research on Mechanical Behavior of the Flax/Polyactic Acid Composites

Composite boards were fabricated using a heat press machine with flax fiber as the reinforcement material and polyactic acid fiber as the matrix. Mechanical properties of the material were tested, and the results indicated that the flax fiber volume fraction of 35% may be a better choice as far as the tensile and bending properties are concerned. Too low a flax volume fraction would reduce the reinforcing effect of the flax fiber. Too high a flax volume fraction may induce defective bonding between the fiber and the matrix. The orientation of the reinforcing fiber in the material played an important role in determining the mechanical behavior of the materials.

Sustained release abilityand safety of matrine polyactic acid microsphere intravitreal injection

：Background Theanti-proliferative effect of matrine has been demonstrated and its relevance to preventionand treatment of proliferative retinovitreopathy is concerned.Howeverthe intravitreousinjection of free-matrine reiteratively may raise the risk of ocularinfection.ObjectiveThe goal of the present study is to investigate the sustained releasingability and safety of matrine polyactic acid microsphere(MAT-PLA-MS intravitrealinjection.MethodsMAT-PLA-MS was prepared by Hebei Medical University and examined underthe transmission electron microscope.The release of MAT-PLA-MS was monitored byultraviolet spectrophotometry.Free-matrine with the dose of 1,2,4mg was intravitreallyinjected respectively in 12 eyes of New Zealand albino rabbits in free-matrine group andMAT-PLA-MS with matrine(2,4,6mg respectively was administered in 16 eyes separately inmatrine microsphere group.The blank microsphere was injected in 6 right eyes as blankcontrol group and normal saline solution was injected in 6 fellow eyes as controlgroup.The retinal function change was evaluated by electroretinogram(ERG),and themorphological and histological change of retina following drug injection were assessedunder the slit lamp biomicroscope,indirect ophthalmoscope,light microscope andtransmission electron microscope.The decomposed process of MAT-PLA-MS in vitreous wasrecorded with ocular anterior segment and fundus color camera.Results MAT-PLA-MScontaining matrine showed the spherical shape with the mean diameter of 2.28±47μm under the transmission electronmicroscope and the drug-loading rate 6.17% and drug-release rate 87.93% in vitro for 672hours,presenting the controllable release characteristics.After implantation into thevitreous,the MAT-PLA-MS containing matrine decomposed gradually with the prolong oftime.The b amplitudes of ERG maximum response were significantly declined in 4mgfree-matrine injection group in comparison with before injection in various timepoints(P 0.05).No obvious abnormal was seen under the slim lamp and ophthalmoscopethrough the study period.The changes of retinal ultrastructure were found from 1 through28 days after injection of 4mg free-matrine,and slight retinal structural damage was seenfrom 7 through 28 days after injection of 6mg MAT-PLA-MS containingmatrine.ConclusionThese results suggest that MAT-PLA-MS possesses good sustained releasefeature.MAT-PLA-MS containing matrine has less toxicity to retina than free-matrine afterintravitreal injection.MAT-PLA-MS is an excellent drug delivery system. Key words: matrine; polyactic acid; microsphere; vitreous

Preventive effect of matrine polyactic acid microsphere on proliferative vitreoretinopathy

目的 评价苦参碱聚乳酸微球防治实验性增生性玻璃体视网膜病变(PVR)的效果.方法 30只新西兰白兔玻璃体腔注入成纤维细胞悬液制备PVR模型.随机分为3组,玻璃体腔分别注入载药微球(含苦参碱4mg)、游离苦参碱(2mg)、生理盐水和空白聚乳酸微球.玻璃体腔手术操作后第1、3、7、14、21、28、35天观察眼前节炎症反应情况、玻璃体混浊程度、玻璃体腔内微球分解过程、玻璃体内增生情况及视网膜是否脱离以及脱离的程度.结果 所有动物1周内前房有轻～中度的炎症反应,1周后消失.各组均有不同比例的动物在不同时间点发展为PVR Ⅰ～Ⅲ级.视网膜脱离的发生率:游离药物组与对照组比较,除35d外,其余各时间点差异均有统计学意义(P＜0.05);载药微球组与对照组相比,各时间点差异均有统计学意义(P＜0.05);载药微球组与游离药物组比较,28d和35d时差异均有统计学意义(P＜0.05).结论 苦参碱聚乳酸微球兔眼玻璃体腔注射能够有效防治实验性PVR。

Clinical study of guided bone regeneration of extracted socket with PLA/PGA membrane and silk fibroin membrane

Purpose: This study was designed to compare the bond regeneratiom effects of treatment using silk fibroin membrane ( Nanogide-S Ⓡ ) resorbable barrier with control group treated by polyactic acid / polylacticglycolic acid membrane(Biomesh Ⓡ ) Methods: 44 severe bone loss on extraction socket from 44 patients were used in this study. In experimental group 22 sites of them were treated by silk fibrin membrane as and the other 22 sites were treated by polyactic acid/ polylacticglycolic acid membrane as a control group. Clinical parameters including recovered bone width, length and radiographic parameter of vertical length were evlauated at base line and 3 months after surgery. Results: 1) Severe bone width, length was significantlly decreased in two group. 2) Bone width, length was significantlly decreased in two group. 3) Decreased bone width, length and radiographic examination differences between group. Conclusions: On the basis of these results, silk fibrin resorbable membrane has similar bone regeneration ability to polyactic acid / polylacticglycolic acid membrane in guided bone regeneration for severe bone loss defect on extraction socket. (J Korean Acad Periodontol 2009;39:129-138)

Experimental study on 5-fluourouracil-loaded immunonanoparticles targeting to lens epithelial cells

To evaluate the immunological characteristics of an immunonanoparticles targeting to human lens epithelial cells and to study if it could internalize into and inhibit the proliferation of target cells in vitro. Crosslinker carbodiimide was used to couple McAb HILE6 (anti-lens epithelial cells antibody) with 5-fluourouracil-loaded polyactic acid nanoparticles PLA (5-FU)-NP to prepare the immunonanoparticles HILE6-PLA (5-FU)-NP. The molar ratio of HILE6 and 5-FU in the immunonanoparticles were observed. The immunological activity of the antibodies in the immunonanoparticles was assessed by ELISA. The third passage lens epithelial cells were divided into four groups; immunonanoparticles, 5-FU nanoparticles, mixed HILE6 and 5-FU nanoparticles and the controls. The proliferation of lens epithelial cells were evaluated by MTT analysis. Internalization of immunonanoparticles, 5-FU nanoparticles and McAb HILE6 were observed by indirect immunofluorescence study of lens epithelial cells. The molar ratio of 5-FU to HILE6 in the immunonanoparticles was 1809:1 and 84% of the original immunological activity of antibodies could be retained. The immunonanoparticles inhibited the proliferation of lens epithelial cells, which was significantly greater than original 5-FU nanoparticles or the blend group. The IC(50) inhibition of immunonanoparticles was 5.0 microg/ml 2 hours after treatment. The immunonanoparticles were bound to the cells surface in 30 minutes; internalized in 2 hours and accumulated around the nucleus after 4 hours. The immunonanoparticles retain immunological activity and could specifically internalize into the lens epithelial cells to inhibit their proliferation.

Efficacy of 5-fluorouracil polyactic acid microsphere in prevention of proliferative vitreoretinopathy

To evaluate the efficacy of 5-fluorouracil polyactic acid microsphere in prevention of proliferative vitreoretinopathy (PVR). 5-fluorouracil polyactic acid microsphere or 5-fluorouracil were used to implant into rabbits vitreous cavity. 48 healthy rabbits were divided into 3 groups: rabbits in Group 1 received implantation of 5-fluorouracil polyactic acid microsphere; rabbits Group 2 served as polyactic acid microsphere control; rabbits in Group 3 received only 5-fluorouracil powder. Macrophages were injected into vitreous cavity of rabbit to induce PVR. 0.2 ml BSS containing 25 mg microsphere with 2.6 mg 5-fluorouracil was injected into vitreous cavity of two eyes in Group 1. 0.2 ml BSS containing 25 mg microsphere without medicine and 0.2 ml BSS containing 2.6 mg 5-fluorouracil were injected into rabbits vitreous cavity in Group 2 and 3 respectively, Drug content in aqueous humor was measured regularly. Release feature of 5-fluorouracil polyactic acid microsphere in vivo was observed. The efficacy of the inhibition of PVR was evaluated according to Ryan's grade of proliferative vitreoretinopathy. The releasing time of 5-fluorouracil polyactic acid microsphere was much longer than 5-fluorouracil powder. Its half life T(1/2) was 379.05 h with low clearance rate. The attack rate of retinal detachment in Group 2 was 62.5% and 71.9% on the 21st and 28th day respectively. The attack rate of retinal detachment in Group 3 was 64.3% and 78.6% whereas that of Group 1 was 13.3% and 13.3% on the 21st and 28th day. There was statistical difference in retinal detachment rate in Group 1 and 2 or 3 (P < 0.01). No differences was found in retinal detachment ration in Group 2 and 3 (P > 0.05). Implantation of 5-fluorouracil polyactic acid microsphere into vitreous cavity can effectively prevent proliferative vitreoretinopathy induced by macrophages in rabbit model.

Technological and economic potential of poly(lactic acid) and lactic acid derivatives

Lactic acid has been an intermediate-volume specialty chemical (world production ∼ 40,000 tons/yr) used in a wide range of food processing and industrial applications. Lactic acid has the potential of becoming a very large volume, commodity-chemical intermediate produced from renewable carbohydrates for use as feedstocks for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly ‘green’ solvents, and specialty chemical intermediates. The recent announcements of new development-scale plants for producing lactic acid and polymer intermediates by major U.S. companies, such as Cargill, Ecochem (DuPont/ConAgra), and Archer Daniels Midland, attest to this potential. In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polylactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed.

Technological and economic potential of poly(lactic acid) and lactic acid derivatives

Lactic acid has been an intermediate-volume specialty chemical (world production ∼ 40,000 tons/yr) used in a wide range of food processing and industrial applications. Lactic acid has the potential of becoming a very large volume, commodity-chemical intermediate produced from renewable carbohydrates for use as feedstocks for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly ‘green’ solvents, and specialty chemical intermediates. The recent announcements of new development-scale plants for producing lactic acid and polymer intermediates by major U.S. companies, such as Cargill, Ecochem (DuPont/ConAgra), and Archer Daniels Midland, attest to this potential. In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polyactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed.

In vivo release profiles of leuprolide acetate from microcapsules prepared with polylactic acids or copoly(lactic/glycolic) acids and in vivo degradation of these polymers.

To screen a suitable polymer for preparing a controlled-release dosage form effective for one month, square plates of polyactic acid (PLA) with average molecular weights of 6000 to 50000 and copoly(lactic/glycolic) acid (PLGA) with average molecular weights of 6000 to 13500 and a copolymer ratio of 90/10 to 55/45 were implanted in rats subcutaneously, and the weight losses were determined over 100 d. Typically the pattern of weight loss was biphasic with a lag time followed by a period when the weight fell exponentially. The lag times and the half lives of the degradation period increased with increase in the molecular weight or with decrease in glycolide content. Release of leuprolide acetate from PLA microcapsules at the injection site in rats (in vivo release) tended to be comparable to the bioerosion rate of the polymer used as the wall substance, and the in vivo release of the drug from PLGA microcapsules tended to be comparable to the biodegradation rate of the polymer. The in vivo release profile of the drug from microcapsules prepared with PLGA of average molecular weight 14000 and copolymer ratio 75/25 was ideal for one month's controlled release. The in vivo release profile from microcapsules injected subsutaneously in rats was comparable to the in vitro release.