scholarly journals Surface Modification of Poly(l–lactic acid) through Stereocomplexation with Enantiomeric Poly(d–lactic acid) and Its Copolymer

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1757
Author(s):  
Qianjin Zhu ◽  
Kaixin Chang ◽  
Liyan Qi ◽  
Xinyi Li ◽  
Woming Gao ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Surface Modification ◽  
Lactic Acid ◽  
Low Molecular Weight ◽  
Water Contact ◽  
Casting Technique ◽  
Melting Temperatures ◽  
Melt Polycondensation ◽  
Plla Film ◽  
Surface Modified

Poly(l–lactic acid) with high molecular weight was used to prepare PLLA films by means of the solvent casting technique. Poly(d–lactic acid) (PDLA) and poly(d–lactic acid–co–glucose) copolymer (PDLAG) with a low molecular weight were synthesized from d–lactic acid and glucose through melt polycondensation. PLLA films were immersed in PDLA or PDLAG solution to prepare surface-modified PLLA films. The modified PLLA film presented stereocomplex crystal (SC) on its surface and homogeneous crystals (HC) in its bulk. The HC structure and surface morphology of modified PLLA films were obviously damaged by PDLA or PDLAG solution. With increasing immersion time, the PLLA films modified by PDLA decreased both the HC and SC structure, while the PLLA films modified by PDLAG increased the SC structure and decreased the HC structure. Hydrophilic glucose residues of PDLAG on the surface would improve the hydrophilicity of surface-modified PLLA films. Moreover, the hydrophilicity of glucose residues and the interaction of glucose residues with lactic acid units could retard HC destruction and SC crystallization, so that PLLA films modified by PDLAG possessed lower melting temperatures of HC and SC, the crystallinity of SC and the water contact angle, compared with PDLAG–modified PLLA films. The SC structure could improve the heat resistance of modified PLLA film, but glucose residues could block crystallization to promote the thermal degradation of PLA materials. The surface modification of PLLA films will improve the thermal stability, hydrophilicity and crystallization properties of PLA materials, which is essential in order to obtain PLA-based biomaterials.

scholarly journals Poly(lactic Acid): A Versatile Biobased Polymer for the Future with Multifunctional Properties—From Monomer Synthesis, Polymerization Techniques and Molecular Weight Increase to PLA Applications

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1822
Author(s):  
Evangelia Balla ◽  
Vasileios Daniilidis ◽  
Georgia Karlioti ◽  
Theocharis Kalamas ◽  
Myrika Stefanidou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Chain Extension ◽  
Poly Lactic Acid ◽  
Plastic Pollution ◽  
Practical Applications ◽  
Decomposition Reactions ◽  
Melt Polycondensation ◽  
Polymerization Conditions ◽  
Molecular Weight Increase

Environmental problems, such as global warming and plastic pollution have forced researchers to investigate alternatives for conventional plastics. Poly(lactic acid) (PLA), one of the well-known eco-friendly biodegradables and biobased polyesters, has been studied extensively and is considered to be a promising substitute to petroleum-based polymers. This review gives an inclusive overview of the current research of lactic acid and lactide dimer techniques along with the production of PLA from its monomers. Melt polycondensation as well as ring opening polymerization techniques are discussed, and the effect of various catalysts and polymerization conditions is thoroughly presented. Reaction mechanisms are also reviewed. However, due to the competitive decomposition reactions, in the most cases low or medium molecular weight (MW) of PLA, not exceeding 20,000–50,000 g/mol, are prepared. For this reason, additional procedures such as solid state polycondensation (SSP) and chain extension (CE) reaching MW ranging from 80,000 up to 250,000 g/mol are extensively investigated here. Lastly, numerous practical applications of PLA in various fields of industry, technical challenges and limitations of PLA use as well as its future perspectives are also reported in this review.

ChemInform Abstract: The First Low Molecular Weight Antibiotic from Lactic Acid Bacteria: Reutericyclin (I), a New Tetramic Acid

ChemInform ◽  
2000 ◽  
Vol 31 (45) ◽  
pp. no-no
Author(s):  
Alexandra Hoeltzel ◽  
Michael G. Gaenzle ◽  
Graeme J. Nicholson ◽  
Walter P. Hammes ◽  
Guenther Jung
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Low Molecular Weight ◽  
Tetramic Acid

scholarly journals Blends of low molecular weight of poly lactic acid (PLA) with gondorukem (gum rosin)

2018 ◽  
Author(s):  
Mujtahid Kaavessina ◽  
Sperisa Distantina ◽  
Achmad Chafidz ◽  
Aditya Utama ◽  
Venisa Mega Puteri Anggraeni
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Poly Lactic Acid ◽  
Low Molecular Weight ◽  
Gum Rosin

scholarly journals Low Molecular Weight Heparin Protects Lung, Renal and Microcirculation Function in Patients with Covid-19 Pneumonia

2020 ◽  
Author(s):  
Li Ma ◽  
Yigang Zeng ◽  
Bing Zhao ◽  
LiLi Xu ◽  
Jian Li ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Renal Function ◽  
Lactic Acid ◽  
Acid Content ◽  
Low Molecular Weight Heparin ◽  
Arterial Oxygen ◽  
Control Group ◽  
Low Molecular Weight ◽  
Arterial Blood ◽  
Lactic Acid Content

Abstract BackgroundCoronavirus disease 2019 (Covid-19) remains a serious health threat worldwide. It is crucial to explore effective treatment measures that reduce mortality. Our aim was to investigate whether low molecular weight heparin (LMWH) can reduce organ injury in patients with Covid-19 pneumonia.MethodsA retrospective study was conducted at the Shanghai Public Health Clinical Center. We initiated a LMWH protocol from January 18th 2020. LMWH was injected subcutaneously at 4100U per day until the D-dimer(DD) level returned to normal, or 5-7 days after admission, whichever occurred first. Admitted patients who received LMWH between January 18th and February 17th 2020 were assigned to the LMWH group. Patients admitted between January 18th and February 17th who did not receive LMWH anticoagulant therapy were the control group. All patients in both groups were aged >18 years, were not pregnant, had no tumors and were in accordance with the following inclusion criteria: 1) DD increased on admission; 2) Body mass index(BMI) >30; 3) History of diabetes. The exclusion criteria were: 1) Platelets <30x109/L or fibrinogen <150 mg/dL; 2) Pregnancy and lactation; 3) Presence of blood system diseases; 4) Immunosuppression; 5) Diseases with a potential risk of bleeding; 6) Receiving anticoagulant drugs or antiplatelet drugs during treatment. General clinical information, indicators for renal function, arterial blood gas analyses and blood lactic acid content were recorded in the two groups 0 (Day 0), 3 (Day 3), 7 (Day 7), and 11 (Day 11) and 15 (Day 15) days after admission.ResultsThere were 48 patients in the LMWH group and 74 patients in the control group. General information, including age, gender, co-existing diseases and onset-to-admission time in both groups was similar. Compared to the control group, LMWH treatment improved the estimated glomerular filtration rate (eGFR) reduced the serum creatinine level (Scr), blood urea nitrogen (BUN)，arterial blood carbon dioxide partial pressure (PaCO2) and arterial blood lactic acid content. However, LMWH treatment reduced arterial oxygen partial pressure (PaO2) and arterial oxygen saturation (SaO2).ConclusionLMWH might be beneficial to improve renal function, CO2 discharge and microcirculation during the early phase of Covid-19 patients . Further randomized controlled trials(RCTs) are warranted in order to further investigate this issue.Trial registrationChiCTR, ChiCTR2000034796. Registered 19 July 2020 - Retrospectively registered, http:// www. chictr.org.cn/listbycreater.aspx.

scholarly journals Products of Metabolism and Processing of Lactic Acid Bacteria as Functional Ingredients

2018 ◽  
Vol 1 (1) ◽  
pp. 47 ◽  
Author(s):  
Antonina Ivanovna Kapustian ◽  
Natalia Cherno ◽  
Alexei Kovalenko ◽  
Kristina Naumenko ◽  
Igor Kushnir
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Organic Acids ◽  
Cell Walls ◽  
Degradation Products ◽  
Lactobacillus Delbrueckii ◽  
Low Molecular Weight ◽  
Gel Chromatography

Lactic acid bacteria (LAB) and bifidobacteria (BB) are unique substances that have a lot of biological and physiological effects. Structural components of LAB and BB – peptidoglycans, compounds of the muramylpeptide series, teichoic acids – have powerful immunological properties. Metabolites of LAB and BB – organic acids, hydrogen peroxide, bacteriocins, etc. – provide antagonistic activity, have an indirect impact on the immune system, reducing the antigenic load caused by pathogenic microorganisms. The expediency of peptidoglycans degradation of LAB and BB cell walls is substantiated. Low molecular weight products of the degradation can easily be absorbed and enter into biochemical processes, accelerating the expected functional-physiological effect. To obtain low-molecular products of peptidoglycans degradation, a combination of LAB and BB was used. The combination of LAB and BB is the sum of the test cultures of Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. Bulgaricus, Bifidobacterium bifidum, Lactococcus cremoris, Streptococcus termophilus. Destruction of peptidoglycans of bacterial cell walls was carried out using a combination of disintegrating factors. The efficiency of destruction was determined by the accumulation of low molecular weight peptides (with molecular weight up to 1500 Da), amino acids and soluble protein in the disintegrate. It has been established that the highest accumulation of low molecular weight degradation products occurs when using autolysis followed by enzymatic hydrolysis during 180 min with the ratio of the enzyme : substrate 1 : 100. At the same time ≈ 53% of protein substances pass from insoluble to soluble state. The molecular weight of the obtained products is determined by the gel chromatography method. The qualitative and quantitative content of organic acids, amino acids and vitamins of group В in the hydrolysis products composition was investigated. It was shown that the obtained product possesses high biological effect in the experiment on animals.

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