Biodegradable electrospun poly(l-lactide) fibers containing antibacterial silver nanoparticles

Biodegradable poly(l-lactide) (PLA) ultrafine fibers containing nanosilver particles were prepared via electrospinning. Morphology of the Ag/PLA fibers and distribution of the silver nanoparticles were characterized. The release of silver ions from the Ag/PLA fibers and their antibacterial activities were investigated. These fibers showed antibacterial activities (microorganism reduction) of 98.5% and 94.2% against Staphylococcus aureus and Escherichia coli, respectively, because of the presence of the silver nanoparticles.     

Magnolol entrapped ultra-fine fibrous mats electrospun from poly(ethylene glycol)-<Emphasis Type="Italic">b</Emphasis>-poly(L-lactide) and <Emphasis Type="Italic">in vitro</Emphasis> release

Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly(ethylene glycol) blocked poly(L-lactide). Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry. According to in vitro drug release investigation by high performance liquid chromatography, it was found that fibers with 10%, 20% and 30% drug entrapped respect to polymer (mass ratio) presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K. The reason may be that fibers with 10% drug entrapped was more easily affected by enzyme while, to some degree, magnolol in fibers with 20% and 30% entrapped prevented polymer from being degraded by enzyme.     

Preparation of Core‐Sheath Composite Nanofibers by Emulsion Electrospinning

Summary: Uniform core‐sheath nanofibers are prepared by electrospinning a water‐in‐oil emulsion in which the aqueous phase consists of a poly(ethylene oxide) (PEO) solution in water and the oily phase is a chloroform solution of an amphiphilic poly(ethylene glycol)‐poly(L ‐lactic acid) (PEG‐PLA) diblock copolymer. The obtained fibers are composed of a PEO core and a PEG‐PLA sheath with a sharp boundary in between. By adjusting the emulsion composition and the emulsification parameters, the overall fiber size and the relative diameters of the core and the sheath can be changed. A mechanism is proposed to explain the process of transformation from the emulsion to the core‐sheath fibers, i.e., the stretching and evaporation induced de‐emulsification. In principle, this process can be applied to other systems to prepare core‐sheath fibers in place of concentric electrospinning and it is especially suitable for fabricating composite nanofibers that contain water‐soluble drugs.

Schematic mechanism for the formation of core‐sheath composite fibers during emulsion electrospinning.     

Cationic poly(ester‐phosphoester)s: Facile synthesis and antibacterial properties

Biodegradable poly(ester‐phosphoester)s bearing multiple chloroethyl groups were synthesized facilely by the ring‐opening copolymerization of 2‐(2‐chloroethoxy)‐2‐oxo‐1,3,2‐dioxaphospholane (CEP) and ε‐caprolactone (CL) in the presence of lanthanum tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)s (La(DBMP)₃) as single‐component catalyst under mild conditions. Then the quaternization reaction was carried out between the halide copolymers and a series of N,N‐dimethyl alkylamines to give poly(ester‐phosphoester)s containing ammonium groups with various charge density and alkyl chain length. The antibacterial properties of these cationic poly(esterphosphoester)s were evaluated by OD600 and zone of inhibition methods against gram‐negative (Escherichia coli) and gram‐positive (Staphylococcus aureus) bacteria. Cationic poly(esterphosphoester)s with long alkyl chain on the ammonium groups show excellent antibacterial activity for both gram‐negative and gram‐positive bacteria even with low charge density. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3667–3673     

Electrospinning and cutting of ultrafine bioerodible poly(lactide‐co‐ethylene oxide) tri‐ and multiblock copolymer fibers for inhalation applications

Triblock copolymers made up of poly(ethylene oxide) (PEO) and polylactide (PLA) were synthesized and converted to fibers by the electrospinning process. A two‐step in situ‐synthesis in bulk was applied to extend PLA‐PEO‐PLA triblock copolymers with relatively short block length and low molecular weight in order to obtain electrospinnable materials. DL‐lactide was polymerized to the hydroxyl chain ends of PEO via the stannous octoate route. Hexamethylene diisocyanate (HDI) was added as chain extender in the second step, leading to poly(ether‐ester‐urethane) multiblock copolymers. The materials were electrospun from solutions in chloroform. Different concentrations and voltages were analyzed. The ether and ester blocks were varied in their block length and their effects on the fiber morphology was studied. Variations in the electrical conductivity of the chloroform solutions were investigated by adding triethyl benzyl ammonium chloride (TEBAC) in different amounts. Finally, with high quality electrospun PLA‐PEO‐PEO triblock copolymer fibers mechanical cutting was possible. Copyright © 2009 John Wiley & Sons, Ltd.     

pH-Sensitive surfactants from lysine: assessment of their cytotoxicity and environmental behavior

The toxicity and environmental behavior of new pH-sensitive surfactants from lysine are presented. Three different chemical structures are studied: surfactants with one amino acid and one alkyl chain, surfactants with two amino acids on the polar head and one alkyl chain, and gemini surfactants. The pH sensitivity of these compounds can be tuned by modifying their chemical structures. Cytotoxicity has been evaluated using erythrocytes and fibroblast cells. The toxic effects against these cells depend on the hydrophobicity of the molecules as well as their cationic charge density. The effect of hydrophobicity and cationic charge density on toxicity is different for each type of cells. For erythrocytes, the toxicity increases as hydrophobicity and charge density increases. Nevertheless, for fibroblasts cationic charge density affects cytotoxicity in the opposite way: the higher charge density, the lower the toxicity. The effect of the pH on hemolysis has been evaluated in detail. The aquatic toxicity was established using Daphnia magna . All surfactants yielded EC(50) values considerably higher than that reported for cationic surfactants based on quaternary ammonium groups. Finally, their biodegradability was evaluated using the CO(2) headspace test (ISO 14593). These lysine derivatives showed high levels of biodegradation under aerobic conditions and can be classified as "readily biodegradable compounds".     

Electrospun poly(aniline‐co‐ethyl 3‐aminobenzoate)/poly(lactic acid) nanofibers and their potential in biomedical applications

Poly(aniline‐co‐ethyl 3‐aminobenzoate) (3EABPANI) copolymer was blended with poly(lactic acid) (PLA) and co‐electrospun into nanofibers to investigate its potential in biomedical applications. The relationship between electrospinning parameters and fiber diameter has been investigated. The mechanical and electrical properties of electrospun 3EABPANI‐PLA nanofibers were also evaluated. To assess cell morphology and biocompatibility, nanofibrous mats of pure PLA and 3EABPANI‐PLA were deposited on glass substrates and the proliferation of COS‐1 fibroblast cells on the nanofibrous polymer surfaces determined. The nanofibrous 3EABPANI‐PLA blends were easily fabricated by electrospinning and gave enhanced mammalian cell growth, antioxidant and antimicrobial capabilities, and electrical conductivity. These results suggest that 3EABPANI‐PLA nanofibrous blends might provide a novel bioactive conductive material for biomedical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Probing the Effects of Antimicrobial-Lysozyme Derivatization on Enzymatic Degradation of Poly(ε-caprolactone) Film and Fiber

Surface derivatization is essential for incorporating unique functionalities into biodegradable polymers. Nonetheless, its precise effects on enzymatic biodegradation still lack comprehensive understanding. In this study, a facile solution-based method is employed to surface derivatize poly(ε-caprolactone) films and electrospun fibers with lysozyme, aiming to impart antimicrobial properties and examine the impact on enzymatic degradation. The derivatized films and fibers have shown high antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Through gravimetric analysis, it is observed that the degradation rate experiences a slight decrease upon lysozyme derivatization. However, this reduction is effectively countered by the inclusion of Tween-20, as affirmed by isothermal titration calorimetry. Comparing films and fibers, the latter undergoes degradation at a more accelerated pace, coupled with a rapid decline in molecular weight. This study provides valuable insights into the factors influencing the degradation of surface-derivatized biopolymers through electrospinning, offering a simple strategy to mitigate biomaterial-associated infections.     

Enzymatic degradation of poly(L-lactide) and poly(epsilon-caprolactone) electrospun fibers

Poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) ultrafine fibers were prepared by electrospinning. The influence of cationic and anionic surfactants on their enzymatic degradation behavior was investigated by measuring weight loss, molecular weight, crystallinity, and melting temperature of the fibers as a function of degradation time. Under the catalysis of proteinase K, the PLLA fibers containing the anionic surfactant sodium docecyl sulfate (SDS) exhibited a faster degradation rate than those containing cationic surfactant triethylbenzylammonium chloride (TEBAC), indicating that surface electric charge on the fibers is a critical factor for an enzymatic degradation. Similarly, TEBAC-containing PCL fibers exhibited a 47% weight loss within 8.5 h whereas SDS-containing PCL fibers showed little degradation in the presence of lipase PS. By analyzing the charge status of proteinase K and lipase PS under the experimental conditions, the importance of the surface charges of the fibers and their interactions with the charges on the enzymes were revealed. Consequently, a "two-step" degradation mechanism was proposed: (1) the enzyme approaches the fiber surface; (2) the enzyme initiates hydrolysis of the polymer. By means of differential scanning calorimetry and wide-angle X-ray diffraction, the crystallinity and orientation changes in the PLLA and PCL fibers during the enzymatic degradation were investigated, respectively.     

Bulky Barbiturates as Non-Toxic Ionic Dye Insulators for Enhanced Emission in Polymeric Nanoparticles

Bulky hydrophobic counterions (weakly coordinating anions) can insulate ionic dyes against aggregation-caused quenching (ACQ) and enable preparation of highly fluorescent dye-loaded nanoparticles (NPs) for bioimaging, biosensing and light harvesting. Here, we introduce a family of hydrophobic anions based on fluorinated C-acyl barbiturates with delocalized negative charge and bulky non-polar groups. Similarly to fluorinated tetraphenylborates, these barbiturates prevent ACQ of cationic dye alkyl rhodamine B inside polymer NPs made of biodegradable poly(lactic-co-glycolic acid) (PLGA). Their efficiency to prevent ACQ increases for analogues with higher acidity and bulkiness. Their structure controls dye-dye communication, yielding bright NPs with on/off switching or stable emission. They enhance dye encapsulation inside NPs, allowing intracellular imaging without dye leakage. Compared to fluorinated tetraphenylborates known as cytotoxic transmembrane ion transporters, the barbiturates display a significantly lower cytotoxicity. These chemically available and versatile barbiturate derivatives are promising counterion scaffolds for preparation of bright non-toxic fluorescent nanomaterials.     

Effects of solvent casted poly (lactic acid)/poly(ethylene glycol)/paraben derivative triazine films on antibacterial performance and cytotoxicity

A series of poly(lactic acid) (PLA) films that including fully paraben substituted triazine derivatives having anti-bacterial properties have been prepared by utilizing the solvent-casting method. PLA as biodegradable polymer, poly(ethylene glycol) (PEG) as a plasticizing agent and s-triazine molecules (TA01, TA02, TA03, TA04, and TA05) behaving as an anti-bacterial component have been utilized in the experiments. The influence of TA compounds on the antibacterial performance of PLA/PEG films was investigated for the first time against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria via the contact active method. TA01-03-05 incorporated PLA/PEG films gave the best results against E.coli bacteria and log10 reductions of these films were 0.78, 0.64, and 0.65 respectively. The effect of TA compounds on the cell viability was investigated against cancer and non-cancerous cell lines using an MTS assay. The results showed that TA compounds had a positive effect on cell growth in non-cancerous cells, while they had a negative effect on cell growth in cancer cells. Furthermore, the addition of TA considerably increased the decomposition temperatures from 349° to 361° and char yield from 0.65 for PLA/PEG film to 2.3 for PLA/PEG/TA05. All of the films had good transparency and low opacity which was 7.2 for pure PLA used for control and the maximum opacity value was 11.2 observed for PLA/PEG/01. TA03 and TA04 caused a decrement of water vapor permission when compared to PLA/PEG films from 1439 to 749 and 664. It was also observed that pure PLA/PEG film lost weight rapidly over time during degradation tests. On the other hand, weight loss wasn't observed in PLA/PEG/TA films. This study focused on demonstrating the use of our new, flexible PLA/PEG derivatives in food and medical packaging.     

Largely improved toughness of poly(lactic acid) by unique electrospun fiber network structure of thermoplastic polyurethane

Oriented thermoplastic polyurethane (TPU) fiber and fiber network were first prepared by electrospinning. The as-prepared TPU fiber or fiber network was then pre-fixed in poly(lactic acid) (PLA)/TPU composite to improve the toughness of PLA. For comparison purpose, TPU/PLA composites with sea-island morphology were also prepared by traditional solution blending and mechanical blending. The results show that the toughness of PLA is greatly increased by the special pre-fixed oriented TPU fibers even at a low content, and the toughness is further increased by the TPU fiber network. Our results indicate for the first time that the toughening effect of special TPU fibers or fiber network is much better than that of traditional TPU with sea-island morphology. This study provides guidance to largely improve the toughness of PLA by designing the special phase morphology of TPU.     

Plasticization of poly(lactide) with blends of tributyl citrate and low molecular weight poly(d,l-lactide)-b-poly(ethylene glycol) copolymers

Polylactide (PLA) is a potential candidate for the partial replacement of petrochemical polymers because it is biodegradable and produced from annually renewable resources. Characterized by its high tensile strength, unfortunately the brittleness and rigidity limit its applicability. For a great number of applications such as packaging, fibers, films, etc., it is of high interest to formulate new PLA grades with improved flexibility and better impact properties.In order to develop PLA-based biodegradable packaging, the physico-mechanical properties of commercially available PLA should be modified using biodegradable plasticizers. To this end, PLA was melt-mixed with blends of tributyl citrate and more thermally stable low molecular weight block copolymers based on poly(d,l-lactide) and poly(ethylene glycol) of different molecular weights and topologies. The copolymers have been synthesized using a potassium based catalyst which is expected to be non toxic and were characterized by utilization of TGA, GPC and NMR techniques.The effect of the addition of up to 25 wt% plasticizer on the thermo-mechanical properties of PLA was investigated and the results were correlated with particular attention to the relationship between properties and applications.To confirm the safety of the catalyst used for the preparation of the copolymers, in vitro cytotoxicity tests have been carried out using MTS assay and the results show their biocompatibility in the presence of the fibroblast cells.Compost biodegradation experiments carried out using neat and plasticized PLA have shown that the presence of plasticizers accelerates the degradation of the PLA matrix.     

Structure and wettability relationship of coelectrospun poly (L‐lactic acid)/gelatin composite fibrous mats

Coelectrospun polylactide(PLA)/gelatin (GE) composite fibrous matrixes have been identified to exhibit much improved performances compared to the respective components; however, the reasons for their water contact angles decreasing to zero at proper PLA/GE ratios remain unclear. To get a deep understanding of the phenomenon, PLA and GE were coelectrospun with different PLA/GE ratios in this study. Although the resulting composite fibers were homogeneous in appearance, they were detected different microscopic structures by transmission electron mircroscope (TEM) and via morphological observations after selective removal of either PLA or GE component. Together with the results of degradation study in phosphate buffered solution, a kind of cocontinuous phase separation microstructure could be identified for the PLA(50 wt%)/GE(50 wt%) composite fibers, which also showed the water contact angle of 0°. This value was far lower than those of electrospun PLA (～123°) and GE (～42°) fibrous matrixes. The X‐ray photoelectron spectrometry (XPS) data revealed that the polar side groups of protein macromolecules have moved toward composite fiber surface with solvent evaporation during electrospinning, due to the hydrophobic interaction between PLA and GE. Then the excellent hydrophilicity of PLA(50 wt%)/GE(50 wt%) composite fibers could be suggested as the consequence of: (1) the cocontinuous phase separation structure could provide more interface and void for water molecules penetrating; and (2) the accumulation of polar groups on composite fiber surface significantly increased the surface wettability. Copyright © 2010 John Wiley & Sons, Ltd.     

Novel 3D Neuron Regeneration Scaffolds Based on Synthetic Polypeptide Containing Neuron Cue

Neural tissue engineering has become a potential technology to restore the functionality of damaged neural tissue with the hope to cure the patients with neural disorder and to improve their quality of life. This paper reports the design and synthesis of polypeptides containing neuron stimulate, glutamic acid, for the fabrication of biomimetic 3D scaffold in neural tissue engineering application. The polypeptides are synthesized by efficient chemical reactions. Monomer γ‐benzyl glutamate‐N‐carboxyanhydride undergoes ring‐opening polymerization to form poly(γ‐benzyl‐l ‐glutamate), then hydrolyzes into poly(γ‐benzyl‐l ‐glutamate)‐r‐poly(glutamic acid) random copolymer. The glutamic acid amount is controlled by hydrolysis time. The obtained polymer molecular weight is in the range of 200 kDa for good quality of fibers. The fibrous 3D scaffolds of polypeptides are fabricated using electrospinning techniques. The scaffolds are biodegradable and biocompatible. The biocompatibility and length of neurite growth are improved with increasing amount of glutamic acid in scaffold. The 3D scaffold fabricated from aligned fibers can guide anisotropic growth of neurite along the fiber and into 3D domain. Furthermore, the length of neurite outgrowth is longer for scaffold made from aligned fibers as compared with that of isotropic fibers. This new polypeptide has potential for the application in the tissue engineering for neural regeneration.     

Encapsulation of proteins in poly(l-lactide-co-caprolactone) fibers by emulsion electrospinning

This study was aimed at investigating emulsion electrospinning to prepare biodegradable fibrous mats with encapsulation of human-nerve growth factor (NGF). One of the best methods for fabricating a bio-functional tissue engineering scaffold is to load bioactive agent into the scaffold. In this work, the feasibility of incorporating NGF into poly(l-lactide-co-caprolactone) fibers by emulsion electrospinning has been studied. The release behavior of encapsulated bovine serum albumin (BSA) was investigated. The bioactivity of NGF released from fibrous mats was verified by testing the neurite outgrowth of rat pheochromocytoma cells (PC12). Furthermore, the process of fiber forming during emulsion electrospinning was discussed. The results demonstrate that emulsion electrospun fibers can successfully encapsulate proteins and release them in a sustained manner. The bioactivity of NGF released from emulsion electrospun fibers was confirmed by PC12 bioassays.     

Preparation and Characterization of Aligned PLLA/PCL/HA Composite Fibrous Membranes

Aligned poly(L-lactide) (PLLA)/poly(?-caprolactone) (PCL)/hydroxyapaite (HA) composite fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and biocompatibility were investigated. The electrospun fibers are highly aligned and the HA are oriented along the fiber axis. When HA are incorporated, the PLLA/PCL/HA composite fibers become thinner due to the increased conductivity. In addition, the aligned HA reinforce the electrospun fibrous membranes. The larger porosity and higher hydrophilic properties induced by HA in the electrospun fibers have improved the degradation of the PLLA/PCL/HA fibrous membranes which have no toxic effect on proliferation of adipose-derived stem cells.     

Degradation of Poly(L‐lactide) by a Fungus

Fungal degradation of poly(L ‐lactide) (PLA) was studied using Tritirachium album ATCC 22563. In liquid culture using basal medium and PLA film, no film degradation was observed. However, by the addition of 0.1% gelatin, about 76% of the PLA film was degraded after 14 days of cultivation at 30°C. Furthermore, the culture filtrate showed degradation activity against PLA, silk fibroin and elastin, but not against poly(β‐hydroxybutyrate), poly(butylene succinate) and poly(ε‐caprolactone). The PLA‐degrading enzyme produced is likely to be protease rather than lipase or poly(β‐hydroxybutyrate)‐depolymerase.     

Technology Trends in Biodegradable Polymers: Evidence from Patent Analysis

The public and governmental awareness regarding more sustainable products have gained significant momentum in the last decade and are directing the future research of the next generation of materials and processes. In such a setting, biodegradable polymers are regarded as one of the technologies driving the innovation and current market growth because they provide an additional end of life option. Tracing the evolving trends of these emerging technologies will help researchers, investors, and policy makers to better evaluate the opportunities of the technology as well as to understand the technology's changing characteristics. Therefore, within this study, we perform bibliographic analyses based on patent information to delineate the current research landscape and to anticipate the future development trends by focusing on the cases of poly(lactic acid) (PLA), poly(hydroxyalkanoates) (PHAs), polycaprolactone (PCL), poly(butylene succinate) (PBS), and poly(butylene adipate-co-terephthalate) (PBAT). The following findings were made: First, PLA gets the highest attention from both academia and industry. Second, the overall international presence of biodegradable polymer patents is high, especially in the field of PHAs. Third, technology maturity and technology strength show that PLA is the most promising technology at present in technological terms, whereas PHAs, PCL, and PBS are uncertain technologies and PBAT has a rather low development potential.     

Preparation and characterization of biodegradable poly(l-lactide)/poly(ethylene glycol) microcapsules containing erythromycin by emulsion solvent evaporation technique

In this work, the producing of a biodegradable poly(l-lactide) (PLA)/poly(ethylene glycol) (PEG) microcapsule by emulsion solvent evaporation method was investigated. The effect of PEG segments added to the PLA microcapsules on the degradation, size distribution, and release behavior was studied. According to the results, PLA/PEG copolymer was more hydrophilic than PLA homopolymer, and with lower glass transition temperature. The surface of PLA/PEG microcapsules was not as smooth as that of PLA microcapsules, the mean diameters of prepared PLA and PLA/PEG microcapsules were 40 and 57 microm, respectively. And spherical forms were observed by the image analyzer and the scanning electron microscope (SEM). Drug release from microcapsules was affected by the properties of PLA/PEG copolymers determined by UV-vis spectra. It was found that the drug release rates of the microcapsules were significantly increased with adding of PEG, which explained by increasing hydrophilic groups.