PLLA Surface Research Articles

The crystallization behaviors and mechanical properties of poly(l-lactic acid)/magnesium oxide nanoparticle composites

Nanocomposites of biodegradable PLLA and magnesium oxide composite (PLLA/MgO-NPs) and surface modified magnesium oxide composite (PLLA/m-MgO-NPs) were prepared using a solution casting method.

Modification of poly(l-lactic acid) electrospun fibers and films with poly(propylene imine) dendrimer

Poly(l-lactic acid) (PLLA) electrospun fibers and films were modified with the second generation of poly(propylene imine) dendrimer (PPI-G2) by three different approaches, namely, sodium hydroxide hydrolysis, plasma treatment and direct application of PPI-G2. For the first and the second approaches, PLLA was modified by sodium hydroxide hydrolysis or plasma treatment to produce carboxylic acid groups. Then, the carboxylic acid groups were activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) and N,N′-dicyclohexyl carbodiimide (DCC) as a hetero bi-functional cross-linker. The cross-linkers promoted the grafting of carboxylic acid groups on the modified PLLA with NH2 groups of PPI-G2. In the third approach, the PPI-G2 dendrimer was directly used as an aminolysis agent for the functionalization of PLLA in a one step process. FTIR analysis confirmed the presence of NH2 groups of PPI-G2 on the modified PLLA samples, resulting from each one of the three modification methods. Studies by SEM shows bead free electrospun fibers. Also, FE-SEM shows nano-cracks on the surface of films after modification. Contact angle, drug release tests, antibacterial effects and the dying results confirmed that these functionalization methods increased hydrophilicity and reactive side-chains of PLLA in the wet chemical process resulted in providing host–guest properties on the PLLA surface for adsorbing various kinds of guest molecules.

Bone-regenerative activity of parathyroid hormone-releasing nano-hydroxyapatite/poly(L-lactic acid) hybrid scaffolds

We developed a bone-regenerative scaffold based on systematic combination of porous organic-inorganic hybrid scaffolds and recombinant human parathyroid hormone (rhPTH). The hybrid scaffold was fabricated by immobilization of polyphosphate-functionalized nano-hydroxyapatite (PP-n-HAp) on the surface of porous poly(L-lactic acid) (PLLA) scaffolds, which was followed by rhPTH loading on the polyphosphates of n-HAp surfaces. The surface polyphosphate functionalities of PP-n-HAp enabled the stable chemical immobilization of n-HAp on the amine-treated pore surface of the PLGA scaffolds. rhPTH with a positive charge was bound at a high efficiency of 98.1~99.5% onto the anionic polyphosphates of PP-n-HAp immobilized on PLLA surfaces and was sustainably released for up to 50 days. The release rate was manipulated by adjusting the amount of loaded rhPTH, and the release data were moderately fitted to the Higuchi’s diffusion model. Four types of scaffolds were tested in rabbit calvarias models (PLLA only, PP-n-HAp-PLLA, rhPTH (2 µg) loaded PP-n-HAp-PLLA, and rhPTH (10 µg) loaded PP-n-HAp-PLLA). After 5 weeks, rhPTH-loaded PP-n-HAp-PLLA (2 and 10 µg of rhPTH) displayed higher bone growth than the control (PLLA only) group. Nano-HAp and sustained release of rhPTH might be synergistically able to enhance the bone healing in the animal model. Open image in new window

PLLAコーティングによるパクリタキセル溶出分解吸収性ステントの開発と薬剤溶出挙動の評価

A drug‐eluting fully bioabsorbable stent which is made of poly(L‐lactic acid) (PLLA) and coated with a drug using PLLA as coating substrate was developed. Drug release behavior from the stent was evaluated in vitro in terms of different molecular weights of substrate PLLA and different coating methods. Four different types of coating method including, PLLA spray coating on the PLLA stent followed by immersion in the drug solution (type 1), spray coating of PLLA/drug mixture (type 2), spray coating of PLLA/drug mixture followed by the heating process (type 3), and spray coating of PLLA/drug mixture followed by immersion in the drug solution (type 4), were employed. The inner and surface structures of the spray coated layer varied depending on the molecular weights of PLLA and/or the drug coating methods, and consequently led to the change in the amount of drug contained as well as the drug releasing behavior. Spraying a pure PLLA onto stent created a dense PLLA coating layer, which prevented the invasion of the drug deep in the layer, and the drug was just only adhered to the pure PLLA surface, resulted in the significant reduction of drug content on the stent surface. On the contrary, the spray coating of PLLA/drug mixture provided a porous layer, which allowed for the drug to invade deep into the layer and resulted in increase of drug content. Porosity and the size of the pore tended to decrease with increasing PLLA molecular weight, and drug release rate also decreased accordingly. Additional heat process facilitated PLLA crystallization, leading to significant reduction of the drug release rate.

Structure and blood compatibility of highly oriented poly(l-lactic acid) chain extended by ethylene glycol diglycidyl ether

Highly-oriented poly(l-lactic acid) (PLLA) with fibrillar structure and micro-grooves was fabricated through solid hot drawing technology for further improving the mechanical properties and blood biocompatibility of PLLA as blood-contacting medical devices. In order to enhance the melt strength and thus obtain high orientation degree, PLLA was first chain extended with ethylene glycol diglycidyl ether (EGDE). The extending degree as high as 25.79 mol% can be obtained at 0.7 wt% EGDE content. The complex viscosity, storage and viscous modulus for chain extended PLLA were improved resulting from the enhancement of molecular entanglement, and consequently higher draw ratio can be achieved during the subsequent hot stretching. The tensile strength and modulus of PLLA were improved dramatically by stretching. The stress-induced crystallization of PLLA occurred during drawing. The interfacial tension (γs·blood) between PLLA surface and blood decreased by chain extension and molecular orientation, indicating the weakened interaction between bioactive substance in the blood and the surface of PLLA. Modification and orientation could significantly enhance the blood compatibility of PLLA by prolonging clotting time and decreasing hemolysis ratio, protein adsorption and platelet activation. The bionic character of oriented PLLA and its anti-coagulation mechanism were tried to be explored.

Imaging the intracellular degradation of biodegradable polymer nanoparticles.

In recent years, the development of smart drug delivery systems based on biodegradable polymeric nanoparticles has become of great interest. Drug-loaded nanoparticles can be introduced into the cell interior via endocytotic processes followed by the slow release of the drug due to degradation of the nanoparticle. In this work, poly(L-lactic acid) (PLLA) was chosen as the biodegradable polymer. Although common degradation of PLLA has been studied in various biological environments, intracellular degradation processes have been examined only to a very limited extent. PLLA nanoparticles with an average diameter of approximately 120 nm were decorated with magnetite nanocrystals and introduced into mesenchymal stem cells (MSCs). The release of the magnetite particles from the surface of the PLLA nanoparticles during the intracellular residence was monitored by transmission electron microscopy (TEM) over a period of 14 days. It was demonstrated by the release of the magnetite nanocrystals from the PLLA surface that the PLLA nanoparticles do in fact undergo degradation within the cell. Furthermore, even after 14 days of residence, the PLLA nanoparticles were found in the MSCs. Additionally, the ultrastructural TEM examinations yield insight into the long term intercellular fate of these nanoparticles. From the statistical analysis of ultrastructural details (e.g., number of detached magnetite crystals, and the number of nanoparticles in one endosome), we demonstrate the importance of TEM studies for such applications in addition to fluorescence studies (flow cytometry and confocal laser scanning microscopy).

LBL coating of type I collagen and hyaluronic acid on aminolyzed PLLA to enhance the cell-material interaction

The aim of the present work is to assemble extracellular matrix components onto poly (L-lactic acid) (PLLA) films using layer-by-layer (LBL) depositing method to enhance the cell-material interaction. To introduce charges onto the hydrophobic and neutral PLLA surface so that the electronic assembly can be processed, poly (ethylene imine) (PEI) was covalently bonded to modify the PLLA films. Positively charged collagen I (Col I) was then deposited onto the aminolyzed PLLA film surface in a LBL assembly manner using hyaluronic acid (HA) as a negatively charged polyelectrolyte. The PEI modification efficiency was monitored via X-ray photoelectron spectroscopy (XPS) measurements. The results of Surface Plasmon Resonance (SPR) and Water contact angle (WCA) monitoring the LBL assemble process presented that the HA/Col I deposited alternately onto the PLLA surface. The surface topography of the films was observed by Atomic force microscope (AFM). In vitro osteoblast culture found that the presence of Col I layer greatly improved the cytocompatibility of the PLLA films in terms of cell viability, cell proliferation and Alkaline Phosphatase (ALP) expression. Furthermore, osteoblast extensions were found to be directed by contact guidance of the aligned Col I fibrils. Thus, these very flexible systems may allow broad applications for improve the bioactivity of polymeric materials, which might be a potential application for bone tissue engineering.

Site‐selective immobilization of anti‐CD34 antibodies to poly(l‐lactide) for endovascular implant surfaces

Aiming at a speed up of the re-endothelialization process of biodegradable endovascular implants, novel approaches for the functionalization of poly(l-lactide) (PLLA) with anti-CD34 antibodies were established. We propose a three-step process involving PLLA surface activation with functional amino groups, attachment of a protein repelling peptide spacer, and covalent random or site-selective immobilization of the antibodies. Obtainable antibody surface densities and antigen binding capacities were thoroughly evaluated by means of enzyme-linked immunosorbent assay. Results indicate that a lower amount of anchoring sites on the antibody favors high coupling efficiency, while localization of the anchoring sites, facing the antigen binding moiety, strongly enhances the antigen capture capacity of the support. Besides minimization of physisorption and cell adhesion exemplarily shown with bovine serum albumin, avidin, and human umbilical vein endothelial cells, respectively, the inclusion of the protein-repelling spacer strengthened this effect, yielding antigen capture capacities exceeding values so far reported in literature. In contrast, the number of amino groups on the PLLA surfaces, which is indeed highly dependent on the applied activation procedure, does not seem to influence antibody coupling efficiency and antigen capture capacity considerably. This allows the choice of surface activation treatment, plasma or wet-chemical, regarding other processing parameters as for instance sterilizability or favored modification depth.

Plasma treatment induces internal surface modifications of electrospun poly(L-lactic) acid scaffold to enhance protein coating

Advanced biomaterials should also be bioactive with regard to desirable cellular responses, such as selective protein adsorption and cell attachment, proliferation, and differentiation. To enhance cell-material interactions, surface modifications have commonly been performed. Among the various surface modification approaches, atmospheric pressure glow discharge plasma has been used to change a hydrophobic polymer surface to a hydrophilic surface. Poly(L-lactic acid) (PLLA)-derived scaffolds lack cell recognition signals and the hydrophobic nature of PLLA hinders cell seeding. To make PLLA surfaces more conducive to cell attachment and spreading, surface modifications may be used to create cell-biomaterial interfaces that elicit controlled cell adhesion and maintain differentiated phenotypes. In this study, (He) gaseous atmospheric plasma glow discharge was used to change the characteristics of a 3D-type polymeric scaffold from hydrophobic to hydrophilic on both the outer and inner surfaces of the scaffold and the penetration efficiency with fibronectin was investigated. Field-emission scanning electron microscope images showed that some grooves were formed on the PLLA fibers after plasma treatment. X-ray photoelectron spectroscopy data also showed chemical changes in the PLLA structure. After plasma treatment, -CN (285.76 eV) was increased in C1s and -NH2 (399.70 eV) was increased significantly and –N=CH (400.80 eV) and –NH3+ (402.05 eV) were newly appeared in N1s. These changes allowed fibronectin to penetrate into the PLLA scaffold; this could be observed by confocal microscopy. In conclusion, helium atmospheric pressure plasma treatment was effective in modifying the polymeric scaffold, making it hydrophilic, and this treatment can also be used in tissue engineering research as needed to make polymers hydrophilic.

Impact of synthetic talc on PLLA electrospun fibers

Poly(l-lactic acid) (PLLA) is an important biomaterial with application as surgical meshes, sutures, and in artificial tissue. Here we prepared novel fibers by electrospinning solutions containing PLLA and a specially synthesized talc (ts), characterized by the presence of aliphatic chains in the structure and completely soluble in the electrospinning solutions. Even a small amount of ts (2wt.%) in the toluene/chloroform solvent increases the solution viscosity, most likely because of specific interactions between talc and PLLA. Morphological characterization demonstrated that homogenous fibers, of neat PLLA and PLLA/ts, are obtained by proper choice of electrospinning conditions. Among the parameters studied, relative humidity (Rh) was found significantly to affect fiber morphology. Morphological homogeneity increases by increasing Rh. In contrast to fibers containing a commercial talc, which is insoluble in the electrospinning mixture, and whose aggregates render the fiber irregular, in the case of PLLA/ts fibers the dispersion of the synthetic talc is achieved at the nanometric length scale. Electrospun mats based on PLLA/ts showed a much higher water contact angle than the neat PLLA mats, the contact angle increasing from 92° to ca. 140°, thus highlighting that a superhydrophobic PLLA surface is obtained by dispersing synthetic talc into PLLA fibers, widening the potential for biomedical applications of this material. Fiber properties of superhydrophobic PLLA were studied by means of differential scanning calorimetry (DSC), static and real-time wide angle X-ray diffraction (WAXD), and water contact angle measurements. Talc was found to promote the development of a small amount of crystallinity during the electrospinning process, and to favor the development of the α crystallographic form during annealing.

Poly-l -lactic acid modified by etching and grafting with gold nanoparticles

This work is focused on characterization of plasma treated and consequently etched and grafted biocompatible polymer poly(l-lactide acid) (PLLA). The interaction of biodegradable polymers with cold plasma is of a great importance in a tissue engineering and surface science. Cold plasma exposure, grafting with gold nanoparticles and etching processes were successfully applied to biopolymer substrate. A method for biopolymer nanostructuring as combination of cold plasma treatment and Au nanoparticle grafting for biocompatibility improvement is introduced. Surface roughness, morphology and surface chemistry was determined. The plasma modification leads to significant increase in surface roughness of PLLA and appearance of sharp spikes and ridges on the PLLA surface. Modification by grafting and etching leads to significant changes in PLLA surface morphology and chemistry. The surface ablation of PLLA has been proved to be significant. In etching of plasma-modified PLLA, methanol proves to be stronger etching agent than water. The grafting of PLLA with gold nanoparticles improved mouse embryonic fibroblasts (NIH 3T3) adhesion and proliferation significantly.

Large-scale and highly efficient synthesis of micro- and nano-fibers with controlled fiber morphology by centrifugal jet spinning for tissue regeneration

PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min(-1). During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation.

A novel method for biopolymer surface nanostructuring by platinum deposition and subsequent thermal annealing

A novel procedure for biopolymer surface nanostructuring with defined surface roughness and pattern dimension is presented. The surface properties of sputtered platinum layers on the biocompatible polymer poly(l-lactic acid) (PLLA) are presented. The influence of thermal treatment on surface morphology and electrical resistance and Pt distribution in ca. 100 nm of altered surface is described. The thickness, roughness and morphology of Pt structures were determined by atomic force microscopy. Surface sheet resistance was studied by a two-point technique. It was the sequence of Pt layer sputtering followed by thermal treatment that dramatically changed the structure of the PLLA’s surface. Depending on the Pt thickness, the ripple-like and worm-like patterns appeared on the surface for thinner and thicker Pt layers, respectively. Electrokinetic analysis confirmed the Pt coverage of PLLA and the slightly different behaviour of non-annealed and annealed surfaces. The amount and distribution of platinum on the PLLA is significantly altered by thermal annealing.

Bacterial Adhesion on Honeycomb-Structured Poly(L-Lactic Acid) Surface with Ag Nanoparticles

Polymeric materials with ordered porous structure have received increasing interest due to their potential applications in biomaterials. However, the enhancement of cell proliferation by this porous structure also raises worries about the increase of bacterial adhesion. For their further use as biomaterials in vivo, it is essential to assess the bacterial adhesion on porous polymer films and find strategies to inhibit the bacterial retention. Honeycomb-structured poly(L-lactic acid) (PLLA) films with Ag nanoparticles were used in this purpose. The Ag+ release rate of Ag/PLLA films was analyzed. In vitro bacterial adhesions of S. aureus and E. coli on flat PLLA films, flat Ag/PLLA films, and honeycomb-structured Ag/PLLA films were compared. Ag nanoparticles activity appears to be more effective against bacteria in honeycomb-structured films compared with flat films of the same material. This activity is particularly significant when E. col is used. The results suggest that the honeycomb surface topography, as well as the enhanced release of Ag+, can greatly contribute to the anti-adhesion property of PLLA surface. These honeycomb-structured Ag/PLLA films also have no significant cytotoxicity. The decoration of Ag nanoparticles in honeycomb structure provides an effective and safe strategy to reduce the bacterial adhesion on porous polymer surface.

표면개질된 생분해성 PLLA 필름 및 지지체의 연골세포와 조골세포 점착거동

Poly(L-lactic acid)(PLLA) 고분자 필름 및 지지체의 세포 친화성을 향상시키기 위하여 산소 플라즈마 처리후 카복실기를 함유한 아크릴산(AA)을 <TEX>$in$</TEX> <TEX>$situ$</TEX> 그래프트시켰다. Stimulated body fluid(SBF) 용액에 15일간 담지시킨 후 hydroxyapatite(HA)를 형성시킨 시료와 phosphate-buffered saline(PBS), fetal bovine serum(FBS), 식염수 및 세포 배양용 배지에 담지시킨 다음 PLLA 시료 표면의 접촉각을 비교해 본 결과, HA 표면이 가장 낮은 접촉각을 나타내었다. 또한 연골세포와 조골세포는 HA 표면 위에서 높은 점착과 성장을 보였으며 연골세포가 HA에 많은 영향을 받는 것으로 확인되었다. 조골세포의 경우 HA 표면 이외에도 FBS나 세포 배양배지에 담지된 표면에서도 높은 세포 증식을 보였다. 더욱이 필름형태보다는 3차원 입체 구조의 다공성 지지체에서 연골세포와 조골세포의 점착과 세포 증식이 향상됨도 확인할 수 있었다. 이러한 표면개질된 PLLA는 조직공학적으로 연골이나 뼈 재생을 위한 유-무기 하이브리드 지지체로 응용될 수 있을 것으로 기대된다. Surface-modified poly(L-lactic acid) (PLLA) films and scaffolds were treated with plasma discharge in oxygen gas and subsequently subjected to <TEX>$in$</TEX> <TEX>$situ$</TEX> grafting of acrylic acid (AA) in order to increase the cell compatibility. The surface of AA-grafted PLLA was converted to hydroxyapatite (HA)-deposited PLLA in stimulated body fluid (SBF). After the samples were immersed in phosphate-buffered saline (PBS), fetal bovine serum (FBS), normal saline, or cell medium, the water contact angles were significantly reduced on the surface of HA-deposited PLLA. Chondrocyte and osteoblast showed a higher attachment and cell proliferation on HA-deposited surfaces and in particular, it was confirmed that chondrocyte was considerably influenced by HA. However, osteoblast showed better cell proliferation on the surfaces immersed in FBS, cell medium or HA-deposited surface. In addition, the cell proliferation in 3D scaffolds was much higher than that on film type, irrespective of chondrocyte and osteoblast. Therefore, such surface-modified PLLAs are expected to be useful as organic-inorganic hybrid scaffolds in the regeneration of cartilage and bone.

The biological response of poly(L‐lactide) films modified by different biomolecules: Role of the coating strategy

The interactions between the surface of synthetic scaffolds and cells play an important role in tissue engineering applications. To improve these interactions, two strategies are generally followed: surface coating with large proteins and surface grafting with small peptides. The proteins and peptides more often used and derived from the extracellular matrix, are fibronectin, laminin, and their active peptides, RGD and SIKVAV, respectively. The aim of this work was to compare the effects of coating and grafting of poly(L-lactide) (PLLA) films on MRC5 fibroblast cells. Grafting reactions were verified by X-ray photoelectron spectroscopy. Cell adhesion and proliferation on coated and grafted PLLA surfaces were measured by cell counting. Vinculin localization and distribution were performed on cell cultured on PLLA samples using a fluorescence microscopy technique. Finally, western blot was performed to compare signals of cell adhesion proteins, such as vinculin, Rac1, and RhoA, as well as cell proliferation, such as PCNA. These tests showed similar results for fibronectin and laminin coated PLLA, while RGD grafting is more effective compared with SIKVAV grafting. Considering the overall view of these results, although coating and grafting can both be regarded as effective methods for surface modification to enhance cell adhesion and proliferation on a biomaterial, RGD grafted PLLA show better cell adhesion and proliferation than coated PLLA, while SIKVAV grafted PLLA show similar adhesion but worse proliferation. These data verified different biological effects depending on the surface modification method used.

Protein adsorption and cytocompatibility of poly(L‐lactic acid) surfaces modified with biomacromolecules

AbstractSurface modification of biomaterials has been adopted over the years in order to improve their biocompatibility. In this study, heparin, hyaluronic acid and chondroitin sulfate were used to modify the surface of poly(L‐lactic acid) (PLLA) films by an entrapment method to promote its biocompatibility and to introduce natural recognition sites to the surface of PLLA films. The surface properties of PLLA films before and after modification were characterized by using water contact angle measurement, scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS). Subsequently, the protein adsorption behavior of radiolabeled (125I) fibronectin (Fn) was evaluated on the modified PLLA surfaces, including adsorption kinetics, isotherm adsorption, competitive adsorption with bovine serum albumin (BSA) or serum. The cytocompatibility of the modified PLLA films was further investigated by testing osteoblasts‐like compatibility, including cell attachment, cell proliferation, alkaline phosphatase activity and cell cycle. Experimental results indicated that the hydrophilicity of the modified PLLA films was improved by the enriched biomacromolecules. In the study of protein absorption, the entrapment of the biomacromolecules on PLLA surface could decrease and reduce Fn adsorption speed and capacity, while the three biomacromolecules had almost the same adsorption capacity. Addition of BSA or serum had great effect on the adsorption of Fn on the modified PLLA surfaces. Moreover, the modifications could significantly promote osteoblasts‐like compatibility of PLLA films. The biomacromolecules modified PLLA films, combining their individual advantages such as good mechanical property and excellent cytocompatibility, are promising candidates for tissue engineering. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Plasma surface modification of porous PLLA films: Analysis of surface properties and in vitro hydrolytic degradation

AbstractThe aim of this research was to investigate the effects of plasma treatment on the surface and on the in vitro degradation behavior of poly(L‐lactide) (PLLA) films. Polymer films were prepared by solvent casting, and their surface was modified by radiofrequency plasma treatments by using oxygen and tetrafluorocarbon gas. Pristine and treated PLLA films were characterized by field emission and atomic force microscopy and by contact angle measurements. In vitro hydrolytic degradation studies were conducted by measurements of weight loss, water absorption, visual inspection, and thermal transitions as a function of the incubation time. As‐deposited PLLA films show a uniform distribution of ring‐like porous structures on the surface due to solvent evaporation. Plasma treatments produce a mass reduction following the etching of the polymer surface. Moreover, the morphology of the porous polymer is modified by the plasma, which induces different micro/nanometric topographic reliefs as a function of the different selected plasma processing parameters. The results indicate PLLA surface become hydrophilic and the surface roughness increased with treatment time in the case of oxygen, whereas a hydrophobic behavior was induced with tetrafluorocarbon plasma treatment. However, in vitro degradation studies show that plasma treatments do not affect the PLLA bulk and the hydrolytic degradation properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Ripple-like structure on PLLA induced by gold deposition and thermal treatment

This paper deals with the surface characterization of biocompatible polymer substrate poly(L-lactic acid) (PLLA) altered by gold sputtering combined with thermal treatment. The influence of gold deposition combined with thermal treatment on surface morphology is studied. The thickness of gold layer was determined by the atomic force microscopy study. Surface sheet resistance of sputtered layers was studied by two-point technique method. The heat treatment induced changes were studied with microscopy. The thermal stress combined with gold sputtering dramatically changes the structure of PLLA's surface. With increasing gold thickness the ripple-like pattern appears and the surface roughness of biopolymer surface significantly increases. These structures are interesting for tissue engineering.

Characterization and morphology analysis of degradable poly(l-lactide) film in in-vitro gastric juice incubation

The purpose of this study was to evaluate the use of the biodegradable poly(l-lactide) (PLLA) as a gastro-jejunal tube anchored in the duodenum for duodenal exclusion. PLLA film was fabricated using a hot melting process to a thickness of around 40–50μm and was then immersed in human gastric juice to estimate the in vitro biodegradability behavior. PLLA film was more biodegradable in human gastric juice than in HCl and PBS. Measurements of weight loss indicated that 60% of original the PLLA was lost after 42 days of incubation. Surface functional group characterization, thermal stability, and surface morphology of the degraded PLLA film in human gastric juice showed that the decomposed sections of the PLLA film were primarily from the amorphous region. The degradation of the PLLA film in human gastric juice began with the erosion of continuous nanocavities in the range of 100–200nm on the PLLA surface over the course of 21 days. The PLLA film collapsed and spiral PLLA fiber was obtained after 42 days of decomposing in human gastric juice.