Synthesis and biological evaluation of PMMA/MMT nanocomposite as denture base material.

Inorganic-polymer nanocomposites are of significant interest for emerging materials due to their improved properties and unique combination of properties. Poly (methylmethacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by in situ suspension polymerization with dodecylamine used as MMT-modifier. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the structures of the nanocomposites. Cytotoxicity test, hemolysis test, acute systemic toxicity test, oral mucous membrane irritation test, guinea-pig maximization test and mouse bone-marrow micronucleus test were used to evaluate the biocompatibility of PMMA/MMT nanocomposites. The results indicated that an exfoliated nanocomposite was achieved, and the resulting nanocomposites exhibited excellent biocompatibility as denture base material and had potential application in dental materials.

[Application of elastin in biomedical materials].

Elastin is a natural biomedical material of great potential. Being endowed with the special crosslinking and hydrophobic structure, elastin retains many good properties such as good elasticity, ductibility, biocompatibility, biodegradability and so on. Nowadays, elastin as a material, which is gradually attracting people' s attention in the biomedical materials field, has been used as tissue engineering scaffolds, derma substitutes and other biomedical materials. In this context, a systematic review on the characteristics of elastin as a biomedical material and on the actuality of its application is presented. Future developments of elastin in the field of biomedical applications are also discussed.

[Advances in interaction of macrophages with tissue engineering related biomaterials].

The host inflammatory reaction is a normal response to injury and the presence of foreign substances. Macrophage is one of the principal cell types in controlling host inflammatory and immune processes; hence, its response to biomaterials has a direct impact on biocompatibility and stability of biomaterials in vivo. This review describes the interaction of macrophages with tissue engineering related biomaterials. The bulk physicochemical structure and surface performance of biomaterials could be designed to control macrophages behaviors (i. e. adhesion, activation, fusion, apoptosis) and host responses, resulting in improving biocompatibility of biomaterials.

Modulation of nano-hydroxyapatite size via formation on chitosan-gelatin network film in situ.

Natural bone is actually an inorganic/organic composite mainly make up of nano-hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), nHA) and collagen fibers. It is most important to form nHA/polymer composites in order to provide good biocompatibility and integration with bone tissue. In this work, nHA was formed in-situ on the surface of chitosan-gelatin (CG) network films in tris-buffer solution containing Ca(NO(3))(2)-Na(3)PO(4). The interaction between CG network film and nHA crystalline were studided using the diffuse reflectance FT-IR (ATR-FTIR), thermal analysis (TGA) and X-ray diffraction analysis (XRD), and the influence the nHA size factors, e.g. the ratio of chitosan (CS) and gelatin (Gel), concentration of calcium ions and reaction temperature, were elucidated by XRD and transmission electron microscope (TEM). Results suggested that carboxyl groups, CO and amino groups play crucial roles for HA formatting on the surface of CG network films and the average size of nHA crystalline decreasing with enhancing Gel content and increase with the increasing calcium and phosphate concentration, and when the reaction temperature below 50 degrees C the nHA crystalline size is almost fixedness (range from 17.2 to 19.2 nm) but when the temperature arrived at 70 degrees C it increase to 52.3 nm.

Hybrid nanofibrous membranes of PLGA/chitosan fabricated via an electrospinning array.

Hybrid nanofibrous membranes of poly(lactic-co-glycolic acid) (PLGA) and chitosan with different chitosan amounts (32.3, 62.7, and 86.5%) were fabricated via a specially designed electrospinning setup consisting of two sets of separate syringe pumps and power supplies. After soaking in chloroform overnight to dissolve PLGA, the amount of chitosan in the hybrid membranes was determined. The structure, mechanical properties, water uptake, and cytocompatibilities of the nanofibrous membranes were investigated by scanning electron microscopy, tensile testing, incubation in phosphate buffer solution, and human embryo skin fibroblasts culturing. Results showed that the chitosan amount in PLGA/chitosan membranes could be well controlled by adjusting the number of syringe for electrospinning of PLGA or chitosan, respectively. Because of the introduction of chitosan, which is a naturally hydrophilic polymer, the hybrid PLGA/chitosan membranes after chitosan crosslinking exhibited good mechanical and water absorption properties. The cytocompatibility of hybrid PLGA/chitosan membranes was better than that of the electrospun PLGA membrane. The electrospun hybrid nanofibrous membranes of PLGA and chitosan appear to be promising for skin tissue engineering. The concept of using an electrospinning array to form multicomponent nanofibrous membranes will lead to the creation of novel scaffolds for tissue engineering applications.

Surface modification of three-dimensional poly(d,l-lactic acid) scaffolds with baicalin: a histological study.

To improve the biocompatibility of three dimensional (3D) poly(d,l-lactic acid) (PDLLA), surface modification with baicalin was performed via a physical entrapment method in this study. The tissue reactions and bone conductivities of such modified PDLLA scaffolds were histologically assessed by using a rabbit radialis defect model in vivo. The native PDLLA scaffolds were prepared via a thermally induced phase separation technique and were characterized by scanning electron microscopy and fluorescence microscopy. The tissue reactions and bone conductivities of both baicalin-modified PDLLA scaffolds and native PDLLA scaffolds were comparably evaluated with histological assay and histomorphometry at different implantation intervals (2, 4, 8 and 12 weeks). Osteocalcin assay, a method to evaluate the bone formation potential, has shown that the osteocalcin production in the baicalin-modified 3D PDLLA scaffold group was significantly higher (p<0.01 or <0.05) than that in the control. Histological observation and histomorphometry results reflected a higher bone formation potential and better biocompatibility of baicalin-modified PDLLA scaffold when compared with those of the native PDLLA scaffolds.

Guanidinylated allylamine-N-isopropylacrylamide copolymer nonviral transgene vectors.

N-Isopropylacrylamide and allylamine copolymers (PNIALM) were prepared by radical polymerization method. To endow them with arginine-like cell membrane penetrating function, the aminos in PNIALMs were transformed to guanidinium groups by chemical modification. The formation and guanidinylation PNIALM were confirmed by NMR; the composition of copolymers and the degree of substitution of guanidino in modified copolymer (PNIALM-G) were estimated as well. The electrophoretic assay revealed that PNIALM-G was capable of condensing DNA in spite of lower binding affinity compared to its parent copolymers. The results of particle size analyzer and TEM indicated that at higher copolymer/DNA weight ratios, the copolymer/DNA complexes were condensed to nanoparticles. PNIALM-G1-3 was shown to be very efficient in mediating plasmid DNA transfection to COS-1 cells both in the presence and absence of serum, even superior to PEI.

[The biologic functional surfaces and their applications in tissue engineering].

The construction of biologic functional surfaces of materials, from the visual angle of material science, is aimed to make the biomaterials adapted by tissues, and to endow them with dynamic conformity; moreover, from the view-point of clinical applications, it is the functional surface to join the environmental tissues with the implanted material, playing the role of artificial extracellular matrix (ECM). The architecture of biologic functional surface is very important in tissue engineering science. Here the primary concepts of biological surface science and the construction and application of biofunctional surfaces in tissue engineering are reviewed.

[Research advances in the controlled release of growth factor related to blood vessel tissue engineering].

Growth factors play an important role in cell adhesion and proliferation as well as in tissue regeneration. By incorporating growth factors into polymer scaffolds, controlled release of them can be performed. The release mechanism is varied with the incorporation methods. In this paper, the latest advances in the controlled release of growth factors by blending, hydrogel, microsphere embedding and chemical bonding are reviewed. The potential application of ultrafine fibric embedding in growth factor delivery is described as well.

Thermosensitive N-isopropylacrylamide-N-propylacrylamide-vinyl pyrrolidone terpolymers: synthesis, characterization and preliminary application as embolic agents.

In this article, thermosensitive N-isopropylacrylamide (NIPAAm)-N-propylacrylamide (NPAAm)-vinyl pyrrolidone (VP) terpolymers (PNINAVP) were prepared by varying feed ratios with free radical copolymerization method. The composition ratios and molecular weights of PNINAVP were examined by NMR and GPC. The thermo-responsive behaviors of copolymer solutions in the absence and with addition of Iohexol, a radiopaque agent, were investigated by differential scanning calorimetry (DSC) and rheometer. The sol-gel transition of the copolymer solutions occurred reversibly within 1 min in response to temperature. Incorporation of Iohexol increased the transition time and transition temperature of PNINAVP solutions; the rheological properties were also influenced. It was observed that at body temperature, PNINAVP and Iohexol could form an integrated bulky hydrogel presumably due to the hydrogen bonding between them, which was favorable for the clinical follow-up and reducing toxic side effects. In vitro embolic model experiment indicated that 5 wt% 16:16:1H PNINAVP solution containing Iohexol displayed a satisfactory embolization effect. This solution was injected into the rete mirabiles (RM) of six swines through a microcatheter. The angiographical results obtained immediately after the operation showed a complete occlusion of the RM, and no recanalization was observed at postoperative month 1. The histological examination demonstrated no acute inflammatory reaction inside the RM and surrounding tissue. This work could provide a beneficial guidance for designing a new temperature-sensitive polymer-based embolic agent.

An investigation on the physicochemical properties of chitosan/DNA polyelectrolyte complexes.

In this work, to eliminate the effect of the hydrophobicity of N-acetyl groups in chitosan on the interaction between chitosan and DNA, a water soluble chitosan with molecular weight of 5000 and deacetylated degree of 99% was selected to complex with DNA at varied charged ratios. The physicochemical properties of chitoplexes were investigated by means of FTIR, circular dichroism (CD), static fluorescence spectroscopy, and atomic force microscopy (AFM). The results indicated that upon interacting with chitosan, the DNA molecules saved a B conformation, and the binding affinity of chitosan to DNA was dependent on pH of media. At pH 5.5, highly charged chitosan had a strong binding affinity with DNA; whereas in pH 12.0 medium, only weak interactions existed. The CD spectra of Hoechst 33258 competitive displacement revealed that chitosan was partially bound to the minor groove of DNA. The morphology of chitosan/DNA complexes was strongly dependent upon the charge ratios. At charge ratio (+/-) of 1:4, not all DNA could be entrapped in the complex; at ratio of 8:1, the spherical complexes with mean size of nanoscale were formed without free DNA, but no typical toroid patterns were observed, which might stem from the strong compact of DNA caused by highly charged chitosan. It was supposed that the strong interaction of chitosan with DNA possibly prevented gene unpacking from chitosan vector, consequently restraining gene expression in nucleus.

Porous poly (DL-lactic acid) modified chitosan-gelatin scaffolds for tissue engineering.

Chitosan-gelatin (Cs-Gel) scaffolds are modified with poly (DL-lactic acid) (PDLLA) dichloromethane solution of different concentrations (0.1, 0.5, and 1.0%) and immersed in water after the evaporation of the solvent. The swollen scaffolds are freeze dried. The concentration of PDLLA has significant effects on both the physicomechanical properties and the cytocompatibility. Data reveal that only the 0.1% concentration could increase the tensile strength fourfold in comparison with the pristine Cs-Gel scaffold, while maintaining the human fibroblast adhesion, migration, and proliferation just like the Cs-Gel scaffold.

[Electrospinning and morphology of ultrafine poly (D, L-lactide) fibers].

Ultrafine poly (D, L-lactide) (PLA) fibers with diameter less than 200 nm produced by electrospinning were studied to obtain tissue restoration resembling extracellular matrix. Scanning electron microscopy was used to observe the fiber morphology. Results showed that the solvent was the critical factor to determine the formation of the electrospun PLA fibers. Compared with acetone, N,N-dimethylformamide (DMF) was a better solvent for PLA to electrospin. Entrance of an organic salt, triethylbenzylammonium chlorate, led to a great increase of the conductivity of PLA/DMF solutions, so that the average fiber diameter of the electrospun PLA fibers decreased dramatically from 500 nm to 100-200 nm. The addition of surfactant, Span-80, did not improve the fiber morphology but formed beaded fiber web.

Influence of the concentrations of hyaluronic acid on the properties and biocompatibility of Cs-Gel-HA membranes.

The object of this study was to investigate the relationship between the concentrations of HA solutions and the physicochemical properties and the biocompatibility of Cs-Gel-HA membranes. The addition of different concentrations of HA not only improved the wettability significantly and extended the degradation time of Cs-Gel-HA membranes, but also changed their mechanical properties. The concentration of HA had a significant influence on the biocompatibility of Cs-Gel-HA membranes. Results demonstrated that it was only the concentrations of HA in a certain range (0.01-0.1%), that could promote the cell adhesion, migration and proliferation, while the concentration of HA was above 0.1% it would either reduce or even inhibit these behaviors.

Influence of different surface modification treatments on poly(D,L-lactic acid) with silk fibroin and their effects on the culture of osteoblast in vitro.

The objective of this study was to investigate the efficiency of two treatments for poly(D,L-lactic acid) (PDLLA) surface modification using silk fibroin. one chemical treatment and one physical treatment: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (WSC) and entrapment. The properties of control films, WSC-modified and entrapment-treated PDLLA films were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). The water-contact angle measurement indicated the change of hydrophilicity and the ESCA analysis suggested that the modified PDLLA film using silk fibroin became enriched with nitrogen atoms. The biocompatibility of PDLLA film might be altered, which in turn would affect the functions of cells that were seeded on it. Therefore, attachment and proliferation of osteoblasts that were seeded on modified PDLLA films and control films were examined. Cell viability was evaluated by the MTT assay and differentiated cell function was assessed by measuring alkaline phosphatase activity. These results suggested that silk fibroin was used to modify PDLLA surface via WSC and that entrapment could improve the interactions between osteoblasts and PDLLA films. The entrapment treatment was more effective thin WSC treatment to accomplish the goal of surface modification.

Poly(D,L-lactic acid) surfaces modified by silk fibroin: effects on the culture of osteoblast in vitro.

The objective of this study was to modify the surface of poly(D,L-lactic acid) (PDLLA) with different molecular weight of silk fibroins, and assess the effects of the modified surfaces on the functions of rat osteoblasts cultured in vitro. The properties of the modified PDLLA surface and the control one were investigated by contact angle and electron spectroscopy for chemical analysis (ESCA). The former indicated the variation of hydrophilicity and the latter suggested that the modified PDLLA film using silk fibroin is enriched with nitrogen atoms. The biocompatibility of the PDLLA film may be altered and in turn affects the seeded cell functions. Therefore, attachment and proliferation of osteoblasts seeded on the modified PDLLA films and the control one were examined. Cell morphologies on these films were studied by scanning electron microscopy (SEM) and cell viability was evaluated by MTT assay. In addition, differentiated cell function was assessed by measuring the alkaline phosphatase (ALP) activity. These results suggest that the silk fibroin-modified PDLLA surface can improve the interaction between osteoblasts and the PDLLA films.

Preparation and histological evaluation of biomimetic three-dimensional hydroxyapatite/chitosan-gelatin network composite scaffolds.

A novel biodegradable hydroxyapatite/chitosan-gelatin network (HA/CS-Gel) composite of similar composition to that of normal human bone was prepared as a three-dimensional biomimetic scaffold by phase separation method for bone tissue engineering. Changing the solid content and the compositional variables of the original mixtures allowed control of the porosities and densities of the scaffolds. The HA granules were dispersed uniformly in the organic network with intimate interface contact via pulverizing and ultrasonically treating commercial available HA particles. Scaffolds of 90.6% porosity were used to examine the proliferation and functions of the cells in this three-dimensional microenvironment by culturing neonatal rat caldaria osteoblasts. Histological and immunohistochemical staining and scanning electron microscopy observation indicated that the osteoblasts attached to and proliferated on the scaffolds. Extracellular matrices including collagen I and proteoglycan-like substrate were synthesized, while osteoid and bone-like tissue formed during the culture period. Furthermore, the cell/scaffold constructs had good biomineralization effect after 3 weeks in culture.

Preparation and characterization of macroporous chitosan-gelatin/beta-tricalcium phosphate composite scaffolds for bone tissue engineering.

A biodegradable composite scaffold was developed using beta-tricalcium phosphate (beta-TCP) with chitosan (CS) and gelatin (Gel) in the form of a hybrid polymer network (HPN) via co-crosslinking with glutaraldehyde. Various types of scaffolds were prepared by freezing and lyophilizing. These scaffolds were characterized by Fourier transform infrared, X-ray diffractometer, and scanning electron microscopy. The macroporous composite scaffolds exhibited different pore structures. Compressive properties were improved, especially compressive modulus from 3.9-10.9 MPa. Biocompatibility was evaluated subcutaneously on rabbits. A mild inflammatory response was observed over 12 weeks. The results suggest that the scaffolds can be utilized in nonloading bone regeneration.

Mechanical and baicalin delivery properties of adhesive matrices for iontophoretic flexible electrodes.

The aim of this work was to evaluate the feasibility and efficacy of flexible adhesive electrodes (FAEs) prepared with adhesive matrices for iontophoretic delivery of baicalin, a drug used for the treatment of atopic dermatitis, viral hepatitis and HIV. Single-layer adhesive matrices (SLAMs) and double-layer adhesive matrices (DLAMs) were prepared from carbomer 940, sodium alginate and polyvinyl alcohol with appropriate mechanical and high baicalin release properties. During the direct-current (DC) iontophoresis with SLAM FAEs, electrochemical reaction caused a clear decrease of pH value at the interface IF(+,FCL) and an increase of pH value at the interface IF(-,FCL). An additional pH-controlling layer in DLAMs could adjust the pH value of interfaces. Thus, deterioration of baicalin stability and the competitive delivery of hydroxyl ions produced with baicalin anions would be avoided during iontophoresis. Iontophoretic flux of baicalin from a DLAM FAE cathode increased proportionally to the time from the onset and affected by the current density and the frequency of pulsed DC. Increasing the applied current or the frequency could enhance the skin permeation flux of baicalin. Moreover, the baicalin skin permeation flux could be further improved from 0.22 microg/cm(2) per h in iontophoresis alone to 0.43 microg/cm(2) per h in the combined approach of iontophoresis and Azone.

beta-TCP/MCPM-based premixed calcium phosphate cements.

Novel premixed calcium phosphate cements (CPCs) were prepared by combining cement liquids comprised of glycerol or polyethylene glycol with CPC powders that consisted of beta-tricalcium phosphate (beta-TCP) and monocalcium phosphate monohydrate (MCPM). Changing the powder to liquid mass ratio enabled the setting time to be regulated, and improved the compressive strength of the CPCs. Although some ratios of the new premixed CPCs had long setting times, these ranged from 12.4 to 27.8 min which is much shorter than the hour or more reported previously for a premixed CPC. The premixed CPCs had tolerable washout resistance before final setting, and the cements had strengths matching that of cancellous bone (5-10 MPa); their maximum compressive strength was up to 12 MPa. The inflammatory response around the premixed CPCs implanted in the subcutaneous tissue in rabbits was more prominent than that of apatite cement. These differences might be due to the much faster resorption rate of the premixed CPCs.