Osteointegration of poly(L-lactic acid)PLLA and poly(L-lactic acid)PLLA/poly(ethylene oxide)PEO implants in rat tibiae

Natural or synthetic materials may be used to aid tissue repair of fracture or pathologies where there has been a loss of bone mass. Polymeric materials have been widely studied, aiming at their use in orthopaedics and aesthetic plastic surgery. Polymeric biodegradable blends formed from two or more kinds of polymers could present faster degradation rate than homopolymers. The purpose of this work was to compare the biological response of two biomaterials: poly(L-lactic acid)PLLA and poly(L-lactic acid)PLLA/poly(ethylene oxide)PEO blend. Forty four-week-old rats were divided into two groups of 20 animals, of which one group received PLLA and the other PLLA/PEO implants. In each of the animals, one of the biomaterials was implanted in the proximal epiphysis of the right tibia. Each group was divided into subgroups of 5 animals, and sacrificed 2, 4, 8 and 16 weeks after surgery, respectively. Samples were then processed for analysis by light microscopy. Newly formed bone was found around both PLLA and PLLA/PEO implants. PLLA/PEO blends had a porous morphology after immersion in a buffer solution and in vivo implantation. The proportion 50/50 PLLA/PEO blend was adequate to promote this porous morphology, which resulted in gradual bone tissue growth into the implant.

Zidovudine-poly (L-lactic acid) solid dispersions with improved intestinal permeability prepared by supercritical antisolvent process

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

In vitro and in vivo evaluation of the biocompatibility of a calcium phosphate/poly(lactic-co-glycolic acid) composite

This study assess the effects of bioceramic and poly(lactic-co-glycolic acid) composite (BCP/PLGA) on the viability of cultured macrophages and human dental pulp fibroblasts, and we sought to elucidate the temporal profile of the reaction of pulp capping with a composite of bioceramic of calcium phosphate and biodegradable polymer in the progression of delayed dentine bridge after (30 and 60 days) in vivo. Histological evaluation of inflammatory infiltrate and dentin bridge formation were performed after 30 and 60 days. There was similar progressive fibroblast growth in all groups and the macrophages showed viability. The in vivo study showed that of the three experimental groups: BCP/PLGA composite, BCP and calcium hydroxide (Ca(OH)(2)) dentin bridging was the most prevalent (90 %) in the BCP/PLGA composite after 30 days, mild to moderate inflammatory response was present throughout the pulp after 30 days. After 60 days was observed dentine bridging in 60 % and necrosis in 40 %, in both groups. The results indicate that understanding BCP/PLGA composite is biocompatible and by the best tissue response as compared to calcium hydroxide in direct pulp capping may be important in the mechanism of delayed dentine bridge after 30 and 60 days.

Development of novel melt-processable biopolymer nanocomposites based on poly(L-lactic acid) and WS2 inorganic nanotubes.

The use of tungsten disulphide inorganic nanotubes (INT-WS2) offers the opportunity to produce novel and advanced biopolymer-based nanocomposite materials with excellent nanoparticle dispersion without the need for modifiers or surfactants via conventional melt blending. The study of the non-isothermal melt-crystallization kinetics provides a clear picture of the transformation of poly(L-lactic acid) (PLLA) molecules from the non-ordered to the ordered state. The overall crystallization rate, final crystallinity and subsequent melting behaviour of PLLA were controlled by both the incorporation of INT-WS2 and the variation of the cooling rate. In particular, it was shown that INT-WS2 exhibits much more prominent nucleation activity on the crystallization of PLLA than other specific nucleating agents or nano-sized fillers. These features may be advantageous for the enhancement of mechanical properties and process-ability of PLLA-based materials. PLLA/INT-WS2 nanocomposites can be employed as low cost biodegradable materials for many eco-friendly and medical applications, and the exceptional crystallization behaviour observed opens new perspectives for scale-up and broader applications.

The influence of architecture on degradation and tissue ingrowth into three-dimensional poly(lactic-co-glycolic acid) scaffolds in vitro and in vivo

The in vitro and in vivo degradation properties of poly(lactic-co-glycolic acid) (PLGA) scaffolds produced by two different technologies-therm ally induced phase separation (TIPS), and solvent casting and particulate leaching (SCPL) were compared. Over 6 weeks, in vitro degradation produced changes in SCPL scaffold dimension, mass, internal architecture and mechanical properties. TIPS scaffolds produced far less changes in these parameters providing significant advantages over SCPL. In vivo results were based on a microsurgically created arteriovenous (AV) loop sandwiched between two TIPS scaffolds placed in a polycarbonate chamber under rat groin skin. Histologically, a predominant foreign body giant cell response and reduced vascularity was evident in tissue ingrowth between 2 and 8 weeks in TIPS scaffolds. Tissue death occurred at 8 weeks in the smallest pores. Morphometric comparison of TIPS and SCPL scaffolds indicated slightly better tissue ingrowth but greater loss of scaffold structure in SCPL scaffolds. Although advantageous in vitro, large surface area:volume ratios and varying pore sizes in PLGA TIPS scaffolds mean that effective in vivo (AV loop) utilization will only be achieved if the foreign body response can be significantly reduced so as to allow successful vascularisation, and hence sustained tissue growth, in pores less than 300 mu m. (C) 2005 Elsevier Ltd. All rights reserved.

The visualisation of vitreous using surface modified poly(lactic-co-glycolic acid) microparticles

AIMS To demonstrate the potential use of in vitro poly(lactic-co-glycolic acid) (PLGA) microparticles in comparison with triamcinolone suspension to aid visualisation of vitreous during anterior and posterior vitrectomy. METHODS PLGA microparticles (diameter 10-60 microm) were fabricated using single and/or double emulsion technique(s) and used untreated or following the surface adsorption of a protein (transglutaminase). Particle size, shape, morphology and surface topography were assessed using scanning electron microscopy (SEM) and compared with a standard triamcinolone suspension. The efficacy of these microparticles to enhance visualisation of vitreous against the triamcinolone suspension was assessed using an in vitro set-up exploiting porcine vitreous. RESULTS Unmodified PLGA microparticles failed to adequately adhere to porcine vitreous and were readily washed out by irrigation. In contrast, modified transglutaminase-coated PLGA microparticles demonstrated a significant improvement in adhesiveness and were comparable to a triamcinolone suspension in their ability to enhance the visualisation of vitreous. This adhesive behaviour also demonstrated selectivity by not binding to the corneal endothelium. CONCLUSION The use of transglutaminase-modified biodegradable PLGA microparticles represents a novel method of visualising vitreous and aiding vitrectomy. This method may provide a distinct alternative for the visualisation of vitreous whilst eliminating the pharmacological effects of triamcinolone acetonide suspension.

Poly lactic-co-glycolic acid controlled delivery of Disulfiram to target liver cancer stem-like cells

Disulfiram (DS), an anti-alcoholism drug, shows very strong cytotoxicity in many cancer types. However its clinical application in cancer treatment is limited by the very short half-life in the bloodstream. In this study, we developed a poly lactic-co-glycolic acid (PLGA)-encapsulated DS protecting DS from the degradation in the bloodstream. The newly developed DS-PLGA was characterized. The DS-PLGA has very satisfactory encapsulation efficiency, drug-loading content and controlled release rate in vitro. PLGA encapsulation extended the half-life of DS from shorter than 2 minutes to 7 hours in serum. In combination with copper, DS-PLGA significantly inhibited the liver cancer stem cell population. CI-isobologram showed a remarkable synergistic cytotoxicity between DS-PLGA and 5-FU or Sorafenib. It also demonstrated very promising anticancer efficacy and antimetastatic effect in liver cancer mouse model. Both DS and PLGA are FDA approved products for clinical application. Our study may lead to repositioning of DS into liver cancer treatment.

Responsiveness of voltage-gated calcium channels in SH-SY5Y human neuroblastoma cells on quasi-three-dimensional micropatterns formed with poly (l-lactic acid)

Introduction: In this study, quasi-three-dimensional (3D) microwell patterns were fabricated with poly (l-lactic acid) for the development of cell-based assays, targeting voltage-gated calcium channels (VGCCs). Methods and materials: SH-SY5Y human neuroblastoma cells were interfaced with the microwell patterns and found to grow as two dimensional (2D), 3D, and near two dimensional (N2D), categorized on the basis of the cells’ location in the pattern. The capability of the microwell patterns to support 3D cell growth was evaluated in terms of the percentage of the cells in each growth category. Cell spreading was analyzed in terms of projection areas under light microscopy. SH-SY5Y cells’ VGCC responsiveness was evaluated with confocal microscopy and a calcium fluorescent indicator, Calcium GreenTM-1. The expression of L-type calcium channels was evaluated using immunofluorescence staining with DM-BODIPY. Results: It was found that cells within the microwells, either N2D or 3D, showed more rounded shapes and less projection areas than 2D cells on flat poly (l-lactic acid) substrates. Also, cells in microwells showed a significantly lower VGCC responsiveness than cells on flat substrates, in terms of both response magnitudes and percentages of responsive cells, upon depolarization with 50 mM K+. This lower VGCC responsiveness could not be explained by the difference in L-type calcium channel expression. For the two patterns addressed in this study, N2D cells consistently exhibited an intermediate value of either projection areas or VGCC responsiveness between those for 2D and 3D cells, suggesting a correlative relation between cell morphology and VGCC responsiveness. Conclusion: These results suggest that the pattern structure and therefore the cell growth characteristics were critical factors in determining cell VGCC responsiveness and thus provide an approach for engineering cell functionality in cell-based assay systems and tissue engineering scaffolds.

Cationic Bovine Serum Albumin (CBA) conjugated Poly Lactic-co-Glycolic Acid (PLGA) nanoparticles for extended delivery of methotrexate into brain tumor

Current treatment strategies for the treatment of brain tumor have been hindered primarily by the presence of highly lipophilic insurmountable blood-brain barrier (BBB). The purpose of current research was to investigate the efficiency of engineered biocompatible polymeric nanoparticles (NPs) as drug delivery vehicle to bypass the BBB and enhance biopharmaceutical attributes of anti-metabolite methotrexate (MTX) encapsulated NPs. The NPs were prepared by solvent diffusion method using cationic bovine serum albumin (CBA), and characterized for physicochemical parameters such as particle size, polydispersity index, and zeta-potential; while the surface modification was confirmed by FTIR, and NMR spectroscopy. Developed NPs exhibited zestful relocation of FITC tagged NPs across BBB in albino rats. Further, hemolytic studies confirmed them to be non-toxic and biocompatible as compared to free MTX. In vitro cytotoxicity assay of our engineered NPs on HNGC1 tumor cells proved superior uptake in tumor cells; and elicited potent cytotoxic effect as compared to plain NPs and free MTX solution. The outcomes of the study evidently indicate the prospective of CBA conjugated poly (D,L-lactide-co-glycolide) (PLGA) NPs loaded with MTX in brain cancer bomber with amplified capability to circumvent BBB.

Development and characterization of Poly(L-lactic acid) (PLLA) platforms for bone tissue engineering

The development of scaffolds based on biomaterials is a promising strategy for Tissue Engineering and cellular regeneration. This work focuses on Bone Tissue Engineering, the aim is to develop electrically tailored biomaterials with different crystalline and electric features, and study their impacts onto cell biological behavior, so as to predict the materials output in the enhancement of bone tissue regeneration. It is accepted that bone exhibits piezoelectricity, a property that has been proved to be involved in bone growth/repair mechanism regulation. In addition electrical stimulations have been proved to influence bone growth and repair. Piezoelectric materials are therefore widely investigated for a potential use in bone tissue engineering. The main goal is the development of novel strategies to produce and employ piezoelectric biomaterials, with detailed knowledge of mechanisms involved in cell-material interaction. In the current work, poly (L-lactic) acid (PLLA), a synthetic semi-crystalline polymer, exhibiting biodegradibility, biocompatibility and piezoelectricity is studied and proposed as a promoter of enhanced tissue regeneration. PLLA has already been approved for implantation in human body by the Food and Drug Administration (FDA), and at the moment it is being used in several clinical strategies. The present study consists of first preparing films with different degrees of crystallinity and characterizing these PLLA films, in terms of surface and structural properties, and subsequently assessing the behavior of cells in terms of viability, proliferation, morphology and mineralization for each PLLA configuration. PLLA films were prepared using the solvent cast technique and submitted to different thermal treatments in order to obtain different degrees of crystallinity. Those platforms were then electrically poled, positively and negatively, by corona discharge in order to tailor their electrical properties. The cellular assays were conducted by using two different osteoblast cell lines grown directly onto the PLLA films:Human osteoblast Hob, a primary cell culture and Human osteosarcoma MG-63 cell line. This thesis gives also a comprehensive introduction to the area of Bone Tissue Engineering and provides a review of the work done in this field in the past until today, in that same field, including the one related with bone’s piezoelectricity. Then the experimental part deals with the effects of the crystallinity degrees and of the polarization in terms of surface properties and cellular bio assays. Three different degrees of crystallinity, and three different polarization conditions were prepared; which results in 9 different configurations under investigation.

Development of semicrystalline morphology of poly(L-lactic acid) during processing of a vascular scaffold

New and promising treatments for coronary heart disease are enabled by vascular scaffolds made of poly(L-lactic acid) (PLLA), as demonstrated by Abbott Vascular’s bioresorbable vascular scaffold. PLLA is a semicrystalline polymer whose degree of crystallinity and crystalline microstructure depend on the thermal and deformation history during processing. In turn, the semicrystalline morphology determines scaffold strength and biodegradation time. However, spatially-resolved information about the resulting material structure (crystallinity and crystal orientation) is needed to interpret in vivo observations.

The first manufacturing step of the scaffold is tube expansion in a process similar to injection blow molding. Spatial uniformity of the tube microstructure is essential for the consistent production and performance of the final scaffold. For implantation into the artery, solid-state deformation below the glass transition temperature is imposed on a laser-cut subassembly to crimp it into a small diameter. Regions of localized strain during crimping are implicated in deployment behavior.

To examine the semicrystalline microstructure development of the scaffold, we employed complementary techniques of scanning electron and polarized light microscopy, wide-angle X-ray scattering, and X-ray microdiffraction. These techniques enabled us to assess the microstructure at the micro and nano length scale. The results show that the expanded tube is very uniform in the azimuthal and axial directions and that radial variations are more pronounced. The crimping step dramatically changes the microstructure of the subassembly by imposing extreme elongation and compression. Spatial information on the degree and direction of chain orientation from X-ray microdiffraction data gives insight into the mechanism by which the PLLA dissipates the stresses during crimping, without fracture. Finally, analysis of the microstructure after deployment shows that it is inherited from the crimping step and contributes to the scaffold’s successful implantation in vivo.

Synthesis and structural characterization of block and random low molecular weight copolymers composed of L-lactic acid and isosorbide succinate moieties

Isosorbide succinate moieties were incorporated into poly(L-lactide) (PLLA) backbone in order to obtain a new class of biodegradable polymer with enhanced properties. This paper describes the synthesis and characterization of four types of low molecular weight copolymers. Copolymer I was obtained from monomer mixtures of L-lactide, isosorbide, and succinic anhydride; II from oligo(L-lactide) (PLLA), isosorbide, and succinic anhydride; III from oligo(isosorbide succinate) (PIS) and L-lactide; and IV from transesterification reactions between PLLA and PIS. MALDI-TOFMS and 13C-NMR analyses gave evidence that co-oligomerization was successfully attained in all cases. The data suggested that the product I is a random co-oligomer and the products II-IV are block co-oligomers.

Influence of Lactic Acid on Endogenous and Viral RNA-Induced Immune Mediator Production by Vaginal Epithelial Cells

OBJECTIVE: To evaluate the influence of lactic acid on immune mediator release from vaginal epithelial cells. METHODS: The human vaginal epithelial cell line, VK2/E6E7, was cultured in the presence or absence of physiological concentrations of lactic acid, and in the presence or absence of the viral Toll-like receptor 3 agonist, poly (inosinic acid: cytidylic acid). Supernatants were assayed by enzyme-linked immunosorbent assay (ELISA) for interleukin (IL)-1 beta, IL-6, IL-8, IL-23, transforming growth factor (TGF)-beta and secretory leukocyte protease inhibitor. RESULTS: Vaginal epithelial cells spontaneously released IL-1 beta (25.9 pg/mL), IL-8 (1.0 ng/mL), TGF-beta (175 pg/mL), and secretory leukocyte protease inhibitor (33.8 ng/mL). Only TGF-beta production was marginally enhanced (49%) by addition of lactic acid alone. Poly (inosinic acid: cytidylic acid) by itself stimulated the release of IL-6 (305 pg/mL) and enhanced IL-8 production (2.8 ng/mL). The combination of poly (inosinic acid: cytidylic acid) and lactic acid markedly increased IL-8 production (5.0 ng/mL) and induced the release of IL-1 beta (96.2 pg/mL). The poly (inosinic acid: cytidylic acid)-mediated lactic acid effect on IL-1 beta and IL-8 release was abrogated when the lactic acid was neutralized or if acetic acid was substituted for lactic acid. CONCLUSION: Lactic acid enhances the release of selective mediators from vaginal epithelial cells and stimulates antiviral immune responses. (Obstet Gynecol 2011;118:840-6) DOI: 10.1097/AOG.0b013e31822da9e9

Block Copolymers Containing (R)-3-Hydroxybutyrate and Isosorbide Succinate or (S)-Lactic Acid Mers

A new aliphatic block copolyester was synthesized in bulk from transesterification techniques between poly((R)-3-hydroxybutyrate) (PHB) and poly(isosorbide succinate) (PIS). Additionally, other two block copolyesters were synthesized in bulk either from transesterification reactions involving PHB and poly(l-lactide) (PLLA) or from ring-opening copolymerization of l-lactide and hydroxyl-terminated PHB, as result of a previous transesterification reactions with isosorbide. Two-component blends of PHB and PIS or PLLA were also prepared as comparative systems. SEC, MALDI-TOF mass spectrometry (MALDI-TOFMS), (1)H and (13)C NMR spectroscopy, WAXD, solubility tests, and TG thermal analysis were used for characterization. The block copolymer structures of the products were evidenced by MALDI-TOFMS, (13)C NMR, and WAXD data. The block copolymers and the corresponding binary blends presented different solubility properties, as revealed by solubility tests. Although the incorporation of PIS sequences into PHB main backbone did not enhance the thermal stability of the product, it reduced its crystallinity, which could be advantageous for faster biodegradation rate. These products, composed of PHB and PIS or PLLA sequences, are an interesting alternative in biomedical applications.

Combined Effect of Poly(hydroxybutyrate) and Plasticizers on Polylactic acid Properties for Film Intended for Food Packaging

Poly(lactic acid) PLA, and poly(hydroxybutyrate) PHB, blends were processed as films and characterized for their use in food packaging. PLA was blended with PHB to enhance the crystallinity. Therefore, PHB addition strongly increased oxygen barrier while decreased the wettability. Two different environmentally-friendly plasticizers, poly(ethylene glycol) (PEG) and acetyl(tributyl citrate) (ATBC), were added to these blends to increase their processing performance, while improving their ductile properties. ATBC showed higher plasticizer efficiency than PEG directly related to the similarity solubility parameters between ATBC and both biopolymers. Moreover, ATBC was more efficiently retained to the polymer matrix during processing than PEG. PLA–PHB–ATBC blends were homogeneous and transparent blends that showed promising performance for the preparation of films by a ready industrial process technology for food packaging applications, showing slightly amber color, improved elongation at break, enhanced oxygen barrier and decreased wettability.