PDLLA Matrix Research Articles

Development and characterization of ceramic-polymeric hybrid scaffolds for bone regeneration: incorporating of bioactive glass BG-58S into PDLLA matrix

In recent years, there has been a notable surge of interest in hybrid materials within the biomedical field, particularly for applications in bone repair and regeneration. Ceramic-polymeric hybrid scaffolds have shown promising outcomes. This study aimed to synthesize bioactive glass (BG-58S) for integration into a bioresorbable polymeric matrix based on PDLLA, aiming to create a bioactive scaffold featuring stable pH levels. The synthesis involved a thermally induced phase separation process followed by lyophilization to ensure an appropriate porous structure. BG-58S characterization revealed vitreous, bioactive, and mesoporous structural properties. The scaffolds were analyzed for morphology, interconnectivity, chemical groups, porosity and pore size distribution, zeta potential, pH, in vitro degradation, as well as cell viability tests, total protein content and mineralization nodule production. The PDLLA scaffold displayed a homogeneous morphology with interconnected macropores, while the hybrid scaffold exhibited a heterogeneous morphology with smaller diameter pores due to BG-58S filling. The hybrid scaffold also demonstrated a pH buffering effect on the polymer surface. In addition to structural characteristics, degradation tests indicated that by incorporating BG-58S modified the acidic degradation of the polymer, allowing for increased total protein production and the formation of mineralization nodules, indicating a positive influence on cell culture.

Functionally Graded Multilayer Composites Based on Poly(D,L lactide)/Bioactive Fillers Fabricated by a 3D Direct Pellet Printing Multi-Extrusion Process

The aim of the present work was to investigate a 3D manufacturing process dealing with 3D Direct Pellet multi-Extrusion (DPPmE). Throughout this paper, various functionally graded materials (FGM) were obtained with tailored properties for bone regeneration. Therefore, an experimental investigation was performed to gain a better understanding of the structure-processing-properties relationships. A poly(D,l-lactic acid) (PDLLA) matrix and bioglass (BG) or hydroxyapatite (HA) bioactive fillers were chosen to obtain hybrid FGM in comparison to composite references. Different compositions and shape factors (from microspheres to fibers) of these bioactive fillers were used to control the PDLLA matrix degradation. Then, different strategies of DPPmE were used to tailor and tune the desired gradient of properties. Interestingly, good interfaces and adhesion properties were obtained. Subsequently, rheological, size-exclusion chromatography, and porosity measurements corroborated the present findings. Besides, tensile as well as thermomechanical properties showed the advantages of the DPPmE process to fabricate FGM composites with tailored architectures.

Preparation of PDLLA based nanocomposites with modified silica by in situ polymerization: Study of molecular, morphological, and mechanical properties

In order to prepare poly-D,L-lactide/silica nanocomposites and to improve the interfacial adhesion between these two materials, silanization of silica was realized adopting two different organosilanes, i.e. 3-glycidyloxytrimethoxysilane or 3-aminopropyltrimethoxysilane. Then, resulting modified silica with epoxy or amino terminal functions served as initiating sites for D,L-lactide in situ polymerization allowing the production of poly-D,L-lactide/silica nanocomposites.Silica dispersion and mechanical properties of these hybrids were compared to composites prepared with hydrophilic or hydrophobic commercial silica by in situ polymerization. These latter composites disclosed heterogeneities with microscale agglomerates and a drop in mechanical properties for 5 wt% of silica loading. In contrast, composites made from poly-D,L-lactide chains chemically grafted on silica carrying initiation sites disclosed nanoscale dispersion of nanofiller in the PDLLA matrix. In particular, with only 1 wt% of these modified silicas, thanks to the nanoscale dispersion of the inorganic nanofiller, an improvement of 24 % for Young modulus and 51 % for ultimate tensile strength was achieved.

In vitro release study of sirolimus from a PDLLA matrix on a bioresorbable drug-eluting stent

Releasing the correct therapeutic drug dose from a bioresorbable drug-eluting stent (DES) is important for inhibiting smooth muscle cell growth, neointimal hyperplasia and in-stent restenosis (ISR). In this study, the in vitro release profiles of sirolimus-in-poly (D, l-lactide) (PDLLA) coatings were investigated under various conditions. First, single-layer, bilayer and various ratios of sirolimus/PDLLA coatings on biodegradable poly (l-lactide) (PLLA) stents and tubes were prepared. There was no apparent delamination or cracking on the stent coating surfaces that had undergone crimping and expansion. Second, the degradation performance of drug-free PDLLA films was investigated to analyse the effects of changes in molecular weight and mass loss. Finally, the in vitro sirolimus release profiles of various coating formulas in phosphate-buffered saline (PBS) were studied by high-performance liquid chromatography (HPLC). The results indicated that the profiles exhibited similar two-phase release kinetics, but the initial release rates were quite different. Moreover, coatings with polyethylene glycol (PEG) additives were prepared to assess their controlled release behaviours. The work reported herein represents a step towards establishing an in vitro release model, which will be verified in future works after comparison with in vivo release profiles.

PDLLA scaffolds with Cu- and Zn-doped bioactive glasses having multifunctional properties for bone regeneration.

Novel multifunctional scaffolds for bone regeneration can be developed by incorporation of bioactive glasses (BG) doped with therapeutic and antibacterial metal ions, such as copper (Cu) and zinc (Zn), into a biodegradable polymer. In this context, porous composite materials of biodegradable poly(d, l-lactide) (PDLLA) mixed with sol-gel BG of chemical composition 60SiO2 ; 25CaO; 11Na2 O; and 4P2 O5 (mol %) doped with either 1 mol % of CuO or ZnO, and with both metals, were prepared. The cytocompatibility of the scaffolds on bone marrow stromal cells (ST-2) depended on both, the amount of glass filler and the concentration of metal ion, as evaluated by lactate dehydrogenase (LDH) activity, cell viability (water-soluble tetrazolium salt [WST-8]), and by cell morphology (scanning electron microscopy [SEM]) tests. In particular, scaffolds having a filler content of 10 wt % showed the highest cytocompatibility. In addition, compared to the neat polymer, the scaffolds containing Cu promoted the angiogenesis marker (Vascular endothelial growth factor concentration) to a larger extent while scaffolds containing Zn increased the osteogenesis marker (specific alkaline phosphatase-activity). Noteworthy, the scaffolds with both metal ions showed a combined effect on both properties. Cu- and Zn-doped glasses also provided higher antibacterial capacity to PDLLA-based scaffolds against methicillin-resistant S. aureus bacteria than undoped glass. In combination, our results showed that by a proper addition of Cu- and Zn-doped BG to a PDLLA matrix, multifunctional composite scaffolds with enhanced biological activity can be designed for bone tissue regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 746-756, 2017.

High loading of graphene oxide/multi-walled carbon nanotubes into PDLLA: A route towards the design of osteoconductive, bactericidal and non-immunogenic 3D porous scaffolds

We have prepared a novel 3D porous biomaterial combining poly (dl-lactic acid) (PDLLA) and graphene and multi-walled carbon nanotubes oxides (MWCNTO-GO) composite. PDLLA as control and a high loading of PDLLA/MWCNTO-GO (50/50 w/w) bioscaffolds were prepared and functionalized. MWCNTs were exfoliated to form MWCNTO-GO by oxygen plasma etching. The later was also applied to enhance the scaffolds wettability, attaching oxygen-containing groups on their surfaces. This approach produced a porous architecture observed by scanning electron microscopy and semi-quantified by electrochemical analysis. The later also indicated a notable increase on the conductivity of PDLLA/MWCNTO-GO scaffold compared to MWCNTO-GO free PDLLA (about 5 orders of magnitudes at low frequencies). Thermogravimetric analysis showed that the MWCNTO-GO acted protecting the PDLLA matrix, enhancing its thermal stability. The PDLLA/MWCNTO-GO scaffolds had significant cellular adhesion, did not present cytotoxicity effect, besides reduced bactericidal proliferation and produced mineralized tissues in SBF media. The metallic MWCNTO-GO powder held together by PDLLA polymer opens a whole new branch of applications, including bioelectroanalyses, drug delivery systems and tissue engineering.

Preparation and characterization of GRGDY modified poly(dl-lactic acid)/hydroxyapatite porous composite

Event Abstract Back to Event Preparation and characterization of GRGDY modified poly(dl-lactic acid)/hydroxyapatite porous composite Youfa Wang1 and Xiao Yu1 1 Wuhan University of Technology, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, China Introduction: Weak hydrophilicity and poor cell affinity of poly(d,l-lactic acid) (PDLLA) are major drawbacks that restrict its wide applications in medical areas. This article focuses on organic/inorganic composite scaffolds for tissue regeneration. RGD (Arg-Gly-Asp) peptide is an amino acid sequence for tissue cells recognize and grafted with PDLLA matrix. Nano hydroxyapatite (n-HAP) is induced into degradable PDLLA/RGD composite to neutralize the acidity. Finally porous composite material with hydroxyapatite (HA) was prepared. Scaffold with high porosity and high interconnectivity is beneficial tissue regeneration. Materials and Methods: The poly{(lactic acid)-co-[(maleic anhydride)-alt-(hexanediamine)]}(BMPLA) was synthesized and modified with RGD peptide. The structures of PRGD and its precursors were characterized by FT-IR, 1H NMR, 13C NMR, UV, SEM, Amino acid analysis (AAA). Firstly, Maleic anhydride (MAH) was grafted onto the backbone of PDLLA by melt free radical copolymerization using BPO as initiator. The reaction process was exactly controlled by temperature and treating time. Secondly, Hexanediamine was grafted onto the backbone of PDLLA at low temperatures. The reaction lasted for 10 min below 8°C and 30 min at 28°C. The final product was HMPLA. The main factors affecting the produce rate of HMPLA was investigated . Thirdly, the polymer matrix was modified with RGD peptide at low temperatures. The pH of the mixture was adjusted to 7-8 with tri-ethylamine. The amino acid concentrations determined by AAA. The material hydrophilicity was tested by the material hydrophilicity. Finally, Nano hydroxyapatite (n-HAP) is induced into degradable PDLLA/RGD composite to prepared the porous composite materials used sodium chloride as porogen. Results and Discussion: PRGD/PDLLA/n-HAP scaffolds were obtained by the above method. HAP particles homogeneously dispersed in matrix are 60-80nm in diameter. The pore size of composited is about 200μm. The concentration, temperature and reaction time were the main factors affecting the produce rate of HMPLA. The results show that the best experimental program is temperature 8 °C, time 1 h and the amount of material hexanediamine excess by 80%. Table 1 shows RGD peptide content grafted on PRGD. The amino acid contents ranges from 16.5μmol/g to 48.8 μmol/g. The hydrophilicity on PRGD is significantly higher than that the pure PDLLA. Table 1 Amino acid analysis PRGD Glycine (μmol/g) Arginine (μmol/g) Aspartic acid (μmol/g) Tyrosine (μmol/g) 48.8 21.5 28.7 16.5 . Conclusions: 1.The maleic anhydride, hexanediamine and GRGDY were successfully grafted onto polylactic acid side chain. The hydrophilicity on PRGD is significantly higher than that the pure PDLLA. 2. The amount of hexanediamine should not be too much, because the polylactic acid will accelerate the degradation and molecular weight reduction under alkaline condition. 3. The pore size of composited is about 200μm when sodium chloride was used as porogen. Natural Science Foundation of China (Project No. 51172172); Key Scientific and Technological Project of Wuhan City (Project No. 201160923310)

Incorporation of Mg particles into PDLLA regulates mesenchymal stem cell and macrophage responses.

In this work, we investigated a new approach to incorporate Mg particles within a PDLLA matrix using a solvent-free commercially available process. PDLLA/Mg composites were manufactured by injection moulding and the effects of Mg incorporated into PDLLA on MSC and macrophage responses were evaluated. Small amounts of Mg particles (≤ 1 wt %) do not cause thermal degradation of PDLLA, which retains its mechanical properties. PDLLA/Mg composites release hydrogen, alkaline products and Mg(2+) ions without changing pH of culture media. Mg-containing materials provide a noncytotoxic environment that enhances MSC viability. Concentration of Mg(2+) ions in extracts of MSCs increases with the increment of Mg content in the composites. Incorporation of Mg particles into PDLLA stimulates FN production, ALP activity, and VEGF secretion in MSCs, an effect mediated by degradation products dissolved from the composites. Degradation products of PDLLA induce an increase in MCP-1, RANTES, and MIP-1α secretion in macrophages while products of composites have minimal effect on these chemokines. Regulation of MSC behavior at the biomaterial's interface and macrophage-mediated inflammatory response to the degradation products is related to the incorporation of Mg in the composites. These findings suggest that including small amounts of Mg particles into polymeric devices can be a valuable strategy to promote osseointegration and reduce host inflammatory response.

Surface modification of poly(D,L-lactic acid) scaffolds for orthopedic applications: a biocompatible, nondestructive route via diazonium chemistry.

Scaffolds made with synthetic polymers such as polyesters are commonly used in bone tissue engineering. However, their hydrophobicity and the lack of specific functionalities make their surface not ideal for cell adhesion and growth. Surface modification of these materials is thus crucial to enhance the scaffold's integration in the body. Different surface modification techniques have been developed to improve scaffold biocompatibility. Here we show that diazonium chemistry can be used to modify the outer and inner surfaces of three-dimensional poly(D,L-lactic acid) (PDLLA) scaffolds with phosphonate groups, using a simple two-step method. By changing reaction time and impregnation procedure, we were able to tune the concentration of phosphonate groups present on the scaffolds, without degrading the PDLLA matrix. To test the effectiveness of this modification, we immersed the scaffolds in simulated body fluid, and characterized them with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman, and infrared spectroscopy. Our results showed that a layer of hydroxyapatite particles was formed on all scaffolds after 2 and 4 weeks of immersion; however, the precipitation was faster and in larger amounts on the phosphonate-modified than on the bare PDLLA scaffolds. Both osteogenic MC3T3-E1 and chondrogenic ATDC5 cell lines showed increased cell viability/metabolic activity when grown on a phosphonated PDLLA surface in comparison to a control PDLLA surface. Also, more calcium-containing minerals were deposited by cultures grown on phosphonated PDLLA, thus showing the pro-mineralization properties of the proposed modification. This work introduces diazonium chemistry as a simple and biocompatible technique to modify scaffold surfaces, allowing to covalently and homogeneously bind a number of functional groups without degrading the scaffold's polymeric matrix.

Scaffolds of PDLLA/bioglass 58S produced via selective laser sintering

Scaffolds of PDLLA were produced to be implemented in maxilofacial surgeries inducing bone repair and regeneration. To prepare these scaffolds, bioglass (BG58S) was synthesized by sol-gel method, in order to be applied as osteoconductive dispersed particles in PDLLA matrix. Once presenting greater facility on parts fabrication, this polymeric matrix enables complex geometries production besides presenting compatible degradation rate for scaffold absorption and bone regeneration. Scaffolds production was performed by selective laser sintering in order to obtain tailored-made parts. FTIR and XRD analyses were carried out to observe the composition and evaluate the presence of crystalized phases in bioglass, obtaining Wollastonite. SEM was used to observe the BG particle distribution in PDLLA matrix and flexural test was performed to evaluate the composite mechanical properties. Results showed that was possible to obtain pieces using SLS method and with addition of 10%wt BG to polymeric matrix, flexural modulus and strength increased regarding to pure polymer.

Blends of poly(d,l‐lactide) with polyhedral oligomeric silsesquioxanes‐based biodegradable polyester: Synthesis, morphology, miscibility, and mechanical property

ABSTRACTA highly branched hybrid copolymer based on polyhedral oligomeric silsesquioxane (POSS) was designed to improve the brittleness of poly(d,l‐lactide) (PDLLA). The toughening material was synthesized using POSS‐OH as the core, which initiated the ring‐opening polymerization of ε‐caprolactone and d,l‐lactide sequentially to form the highly branched POSS‐g‐poly (ε‐caprolactone)‐b‐poly(d,l‐lactide) (POSS‐g‐PCL‐b‐PLA) copolymer with eight PCL‐b‐PLA arms. The POSS‐g‐PCL‐b‐PLA copolymer had a very good dispersion in the PDLLA matrix with the size of microdomains smaller than 1 µm when added at a low content below 10 wt %. In related to the nano‐scale size of microdomains in the blends, the crystallinity of PCL blocks was significantly suppressed. Thus, the addition of POSS‐g‐PCL‐b‐PLA is very effective to improve the roughness of the matrix polymer when added at a low content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40776.

Shape memory behaviour of HA-g-PDLLA nanocomposites prepared via in situ polymerization.

The shape memory properties of hydroxyapatite-graft-poly(d,l-lactide) (HA-g-PDLLA) nanocomposites were investigated in the present study. Hybrid nanocomposites with various HA proportions (5, 10, 15 and 25 wt%) were prepared via in situ grafting polymerization. It is found that the nanocomposites exhibit various shape memory (SM) performances with different HA loadings. Excellent shape memory properties were found for HA-g-PDLLA nanocomposites with 15 wt% inorganic HA proportions, observed through a well-established four-step SM programming cycle method. However, at low HA loading (including pure PDLLA), the samples experienced a severe relaxation process, which caused a plastic, irreversible deformation of the sample and resulted in a poor SM recovery ratio. In addition, the shape memory behaviours of HA25-g-PDLLA nanocomposites and HA25/PDLLA blends were compared. Due to the serious relaxation process caused by the weak interaction forces of hydrogen bonding between HA and PDLLA, the HA25/PDLLA blends had much worse shape recovery ability than the HA25-g-PDLLA nanocomposites.

Asymmetric PDLLA membranes containing Bioglass® for guided tissue regeneration: Characterization and in vitro biological behavior

ObjectiveIn the treatment of periodontal defects, composite membranes might be applied to protect the injured area and simultaneously stimulate tissue regeneration. This work describes the development and characterization of poly(d,l-lactic acid)/Bioglass® (PDLLA/BG) composite membranes with asymmetric bioactivity. We hypothesized that the presence of BG microparticles could enhance structural and osteoconductivity performance of pure PDLLA membranes. MethodsThe membranes were prepared by an adjusted solvent casting method that promoted a non-uniform distribution of the inorganic component along the membrane thickness. In vitro bioactive behavior (precipitation of an apatite layer upon immersion in simulated body fluid, SBF), SEM observation, FTIR, swelling, weight loss and mechanical properties of the developed biomaterials were evaluated. Cell behavior on the membranes was assessed using both human bone marrow stromal cells and human periodontal ligament cells. ResultsJust the BG rich face of the composite membranes induced the precipitation of bone-like apatite in SBF, indicating that this biomaterial exhibit asymmetric osteoconductive properties. SEM images, DNA content and metabolic activity quantification revealed an improved cell adhesion and proliferation on the composite membranes. Composite membranes also stimulated cell differentiation, mineralization, and production of extracellular matrix and calcium nodules, suggesting the positive effect of adding the bioactive microparticles in the PDLLA matrix. SignificanceThe results indicate that the proposed asymmetric PDLLA/BG membranes could have potential to be used in guided tissue regeneration therapies or in orthopedic applications, with improved outcomes.

Comparison of abiotic and biotic degradation of PDLLA, PCL and partially miscible PDLLA/PCL blend

Important differences between the biotic and abiotic hydrolysis of neat poly(dl-lactide) (PDLLA), poly(ε-caprolactone) (PCL) and a partially miscible PDLLA/PCL blend were found in this work. In abiotic conditions, the degradation process of all the studied specimens mainly proceeded by a bulk degradation mechanism and the diffusion rate of degradation products into the medium was relatively slow after 18weeks. The hydrophobic and semi-crystalline nature of PCL matrix made this polymer very stable against abiotic hydrolysis, whereas the degradation of PDLLA proceeded much faster due to its amorphous structure. In the first stages of degradation, PDLLA/PCL blend showed that its rich continuous PDLLA phase catalyzed the hydrolysis of the PCL phase, while the low content of PCL molecules partially delayed hydrolysis of PDLLA matrix. In compost, higher levels of degradation were found for all the studied systems during the first 12weeks of degradation, indicating an important effect of enzymes from microbes in compost on the degradation of PDLLA and PCL. Neat PDLLA and PDLLA/PCL blend seemed to degrade mainly by a bulk degradation mechanism, at least during the first 12weeks, such as previously observed in abiotic conditions, whereas PCL was preferentially degraded by a surface mechanism due to a very strong catalytic effect of microorganisms on its degradation. Contrary to the abiotic degradation, it was observed that the presence of a low content of PCL molecules in the rich-PDLLA blend did not interfere with the degradation trend of PDLLA in compost, and that the continuous PDLLA phase could partially suppress the biotic degradation of PCL molecules.In general, abiotic and biotic hydrolysis of PDLLA/PCL blends seems to be a complex phenomenon depending not only on the mixing ratio of both polymers but also on their crystallinity, miscibility level of polymer phases and the preferential degradation mechanism of each polymer component. If blends of PDLLA/PCL present a similar level of miscibility, it would be possible to estimate if the presence of the PDLLA or PCL phase could have a general catalytic or delaying role in the blend during the initial degradation stages, depending on which environment they are subjected to and the content of each polymer phase in the blend.

Osteopontin functionalization of hydroxyapatite nanoparticles in a PDLLA matrix promotes bone formation

We studied the osteoconductive tissue response of hydroxyapatite (HA) nanoparticles functionalized with osteopontin (OPN) in a matrix of poly-D,L-lactic-acid (PDLLA). In a canine endosseus 0.75-mm gap implant model, we tested the osteointegrative impact of the OPN functionalized composite as an implant coating, and a non-functionalized composite was used as reference control. During the four weeks of observation, the OPN functionalized composite coating significantly increased the formation of new bone in the porosities of the implant, but no differences were observed in the gap. The study provides evidence of its potential use either alone or in combination with other osteoconductive compounds.

Impregnation of paclitaxel into poly(dl-lactic acid) using high pressure mixture of ethanol and carbon dioxide

Paclitaxel (PT) is a mitotic inhibitor used in cancer chemotherapy. Impregnation of PT into amorphous poly(DL-lactic acid) (PDLLA) in mixtures of high-pressure ethanol (EtOH) and carbon dioxide (CO2) at various compositions was investigated at 313 K and 20 MPa. It was demonstrated that the high pressure EtOH–CO2 mixture is a promising solvent for fabrication of polymer-based drug delivery systems (DDS) materials, which enables the avoidance of drug deterioration due to processing at elevated temperatures. A mixture with 25 mol% EtOH allowed impregnation of the largest amount of PT in the PDLLA matrix. The amount of impregnated PT in the EtOH–CO2 mixtures was 10 times and 28 times larger than those in supercritical CO2 and liquid EtOH, respectively. The composition of the EtOH–CO2 mixture affected the amount of PT that could be impregnated. The increase in the amount of impregnated PT in the mixture is probably attributed to plasticization of PDLLA and increased solubility of PT into the EtOH–CO2 mixture. The degree of swelling observed in the PDLLA caused by plasticization depended on the composition of the EtOH–CO2 mixture, with the volume increasing to 1.7 times the initial size for a mixture containing 40 mol% EtOH at 313 K and 20 MPa. Physical aging was induced after the swollen PDLLA in supercritical CO2 was vitrified by pressure drop from 20 MPa to atmospheric pressure at 313 K, whereas vitrification hardly occurred in the EtOH–CO2 mixture under the same conditions.

Premature degradation of poly(α-hydroxyesters) during thermal processing of Bioglass®-containing composites

Bioactive, biodegradable composites are increasingly being explored as bone replacement materials and as scaffolds for tissue engineering. Their properties are not only dependent on the properties of the filler and matrix, but are also determined by their interaction. This study investigated the effect on poly(D,L-lactide) (PDLLA) matrix when processed at high-temperatures in the presence of Bioglass particulate filler. Composites with different filler contents were compounded at elevated temperatures by co-extrusion followed by compression moulding and compared with composites of similar composition prepared by thermally induced phase separation (TIPS), a low-temperature processing route. It was found that the inclusion of Bioglass in PDLLA under elevated temperatures resulted in the degradation of the matrix, leading to a reduction in the mechanical properties of the composites and in the molecular weight of the matrix. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy showed the presence of a peak at 1600 cm(-1) in the composite material, particularly when processed at elevated temperatures, whereas no peak at this wavelength was discernible for the pure PDLLA. Furthermore, time-based ATR-FTIR spectra taken at elevated temperatures on the TIPS-processed composites showed an increase in the intensity of the peak at 1600 cm(-1) and a concomitant reduction of the CO stretch peak at 1745 cm(-1) with time. This suggested the formation of a carboxylate salt by-products as a consequence of a reaction at the interface between the Bioglass filler and the PDLLA matrix. Therefore, the results confirmed that this degradation was not solely due to shear effects during the extrusion process. This work thereby supports the assertion that, in the presence of Bioglass filler particles, poly(alpha-hydroxyester)-based composites should not be processed at elevated temperatures.

Effects of hydrolysis on dodecyl alcohol modified β-CaSiO3 particles and PDLLA/modified β-CaSiO3 composite films

In this research, β-CaSiO3 particles were surface modified with dodecyl alcohol, and Poly-(DL-lactic acid) (PDLLA)/modified β-CaSiO3 composite films were fabricated with a homogenous dispersion of β-CaSiO3 particles in the PDLLA matrix. The aim of the study was to investigate the properties of the composite films before and after hydrolytic treatment. SEM images showed retained homogenous dispersion of β-CaSiO3 particles after hydrolysis and tensile test also showed maintained mechanical property. Simulated body fluid (SBF) incubation experiment suggested that hydrolytic treatment did not affect the formation of hydroxyapatite on the surface of the composite films. The hydrophilicity of the composites was greatly recovered (from 69.82° to 50.28°) after hydrolysis. In addition, cells cultured on composite films after hydrolysis presented the highest cell proliferation rate and differentiation level. All of these results suggested that the surface modification of silicate particles with dodecyl alcohol along with reversible hydrolytic treatment was an effective and feasible approach to fabricate polymer/silicate composite materials with improved properties.

In situ preparation and characterization of a novel gelatin/poly(D,L‐lactide)/hydroxyapatite nanocomposite

A novel biodegradable polymer-ceramic nanocomposite was prepared using the in situ preparation method, which consisted of gelatin (gel), poly(D,L-lactide) (PDLLA), and hydroxyapatite (HA) nanofibers. In this article, the HA nanofibers with length/diameter (L/D) ratio of 19.8 in gel/PDLLA/HA nanocomposites were synthesized and precipitated in polymeric matrix by one-step hydrothermal mineralization. The crystalline phases, structural morphology, mechanical characterization, and chemical interaction of gel/PDLLA/HA nanocomposites were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, mechanical test, and Fourier transform infrared spectroscopy. The results showed that the crystalline HA nanofibers were uniformly mineralized in gel and PDLLA matrix and the interaction between Ca(2+) in HA (nanofibers and negative-charged functional groups in gel and PDLLA molecular chains was formed. Thus, the schematic model of two polymeric chains bridged by inorganic nanofibers was designed on the basis of the experimental results. Moreover, it can clearly explain why the mechanical properties of gel/PDLLA/HA nanocomposites turned strong.

Shape memory effect of poly( d, l-lactide)/Fe 3O 4 nanocomposites by inductive heating of magnetite particles

In this paper, the preparation of biocompatible poly( d, l-lactide) (PDLLA)/magnetite (Fe 3O 4) nanocomposites and their shape memory effect are reported. Fe 3O 4 nanoparticles with an average size of 20 nm were synthesized by chemical co-precipitation and mixed uniformly with a PDLLA matrix. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mechanical testing were carried out to determine the micro-surface morphology, glass transition temperature ( T g), functional groups change and mechanical properties of the PDLLA/Fe 3O 4 nanocomposites. The interesting shape memory behavior of the nanocomposites induced by an ultrasonic alternating magnetic field were also observed. SEM and DSC showed that there was a close interaction between the polymer matrix and the magnetic nanoparticles. Formation of weak hydrogen bonds between the C O in PDLLA and Fe–OH groups of the surface of nano-crystalline Fe 3O 4 was examined by FTIR. The PDLLA/Fe 3O 4 nanocomposites displayed a desirable shape memory effect.