The preparation of an elastomer/silicate layer nanocompound with an exfoliated structure and a strong ionic interfacial interaction by utilizing an elastomer latex containing pyridine groups.

A great variety of polymer/layered silicate (PLS) nanocomposites have been reported, however, there are few exfoliated PLS nanocomposites and their inorganic-organic interfaces are still a great problem, especially for the elastomers. In this research, a kind of exfoliated elastomer/silicate layer nanocompound was prepared and proved by XRD and TEM, in which 10 phr Na(+)-montmorillonite was dispersed in butadiene-styrene-vinyl pyridine rubber by latex compounding method with acidic flocculants. Moreover, a dynamic mechanical thermal analyzer (DMTA) suggested a strong interfacial interaction (interaction parameter B(H) = 4.91) between the silicate layers and macromolecules in addition to the weak inorganic-organic interfacial interaction, and solid state (15)N NMR indicated the formation of a strong ionic interface through the acidifying pyridine. Subsequently, a remarkable improvement of the dispersing morphology, mechanical performance and gas barrier property appeared, compared to that using calcium ion flocculants. This supports the formation of an exfoliated structure and an improved interfacial interaction.

Acellular Spinal Cord Scaffold Implantation Promotes Vascular Remodeling with Sustained Delivery of VEGF in a Rat Spinal Cord Hemisection Model.

BACKGROUND: Promoting angiogenesis provides a possible therapeutic approach in treating spinal cord injury (SCI). Vascular endothelial growth factor (VEGF) is a pro-angiogenic substance that is involved in endothelial cell (EC) proliferation, migration, and survival. Exogenous administration of VEGF to the lesion epicenter of the spinal cord has been recently revealed as a potential method for promoting the blood vessel sprouting. METHODS: Spinal cord hemisection in a rat model was established and angiogenesis was studied through implant of an acellular spinal cord scaffold (ASCS) with sustained delivery of VEGF₁₆₅. The poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) encapsulating VEGF₁₆₅ were fabricated on basis of an emulsion and solvent evaporation method and conjugated to ASCS by a Genipin (GP) crosslinking technology. The resultant scaffolds were marked as V-ASCS. VEGF₁₆₅ entrapment efficiency (EE) and released kinetics were determined by an ultraviolet absorption measurement. Angiogenesis and vascular remodeling were observed via a high-resolution micro-CT and analyzed quantitatively by vascular morphometric parameters. Spinal cord histology and Basso, Beattie, and Bresnahan (BBB) locomotor rating scale were further studied. RESULTS: VEGF₁₆₅ was entrapped with high efficiency (90.8±3.1) %. In vitro VEGF₁₆₅ release kinetics study showed an initial burst of 1.966 µg mg NPs-1 and 1.045µg mg V-ASCS-1 respectively in the first 24 hours. In the phase of sustained release, approximately 0.040µg mg NPs-1 and 0.022µg mg V-ASCS-1 per day was on-going until 720h. In the rat spinal cord hemisection model, implant of V-ASCS at the injured site showed a promotion of angiogenesis and vascular remodeling following SCI. A better outcome can be confirmed histologically. However, functional improvement is limited in the animal model. CONCLUSION: The results indicate that progress of vascular reconstruction is accelerated in the V-ASCS implanted SCI rats.

A comparison of biomechanical stability and pullout strength of two C1-C2 fixation constructs.

BACKGROUND CONTEXT: Several fusion techniques are used to treat atlantoaxial instability. Recent literature suggests that intralaminar screw (LS) fixation and pedicle screw (PS) fixation offer similar stability and comparable pullout strength. No studies have compared these characteristics after cyclic loading. PURPOSE: To compare the stability and pullout strength of intra-LSs and PSs in a C1-C2 instability model after 1,000 cycles of axial loading. STUDY DESIGN: In vitro biomechanical study. OUTCOME MEASURES: Stability in axial rotation and screw pullout strength after cyclic loading. METHODS: Six fresh-frozen human cadaveric cervical spines (C1-C2) were used in this study. C1-C2 instability was mimicked via odontoidotomy at its base and posterior soft-tissue release, including the supraspinous ligaments and facet joint capsules. Specimens were tested to 1,000 cycles after stabilization with two fixation constructs: C1 lateral mass (LM) screws and C2 intra-LSs (C1LM-C2LS) and C1 LM screws and C2 PSs (C1LM-C2PS). Angular motion was recorded for right and left axial rotation using an Optotrak 3020 system (Northern Digital, Waterloo, Ontario, Canada). Tensile loading to failure was then performed collinear to the longitudinal axis of the screw, and the data were recorded as peak pullout strength in newtons. RESULTS: There was no statistically significant difference in stability (measured in degrees of rotation) between the intra-LS and PS constructs at 250, 500, 750, and 1,000 cycles of axial rotation. Furthermore, there was no significant difference in stability at 250 cycles versus 1,000 cycles for the LS (1.30 vs. 1.49, p = .80) or PS (0.84 vs. 0.85, p = .96). Pedicle screws had higher pullout strength when compared with the intra-LSs (757.5 ± 239 vs. 583.4 ± 472 N); however, high standard deviation precluded statistical significance (p = .44). CONCLUSIONS: Our data suggest that a C1LM and C2LS construct has similar biomechanical stability when compared with a C1LM and C2PS construct after 1,000 cycles of axial rotation. Furthermore, PSs had higher pullout strength when compared with LSs; however, this result was not statistically significant.

[Biological characteristic comparison between long junctional epithelium cells and junctional epithelium cells].

PURPOSE: To culture long junctional epithelium (LJE) cells in vitro and compare its biological characteristics with junctional epithelium (JE) cells. METHODS: LJE samples were collected from the patients with chronic periodontitis during flap surgery. Sulcular parts of tissues were removed by sterile scissor then enzymatic method and keratinocyte-serum free medium (KSFM) were used for culturing. JE samples were obtained from healthy bicuspid premolars or third morlars for orthodontic or impaction reasons and the cells were cultured in the same way as LJE. The two types of cells were compared in cell morphology, dimension,viability, proliferation, apoptosis and cytokeratin expression by means of cytoanalyzer, confocal laser scanning microscope and flowcytometry. Statistical analysis was performed using SPSS11.5 software package for independent-samples t test. RESULTS: LJE and JE cells exhibited similar cell morphology. Although the viability of LJE cells were lower than JE cells, there were no statistical significance (P>0.05). The mean diameter and volume of LJE cells were (19.03+/-0.19)microm and (4.29+/-0.19)x10(3) fL versus (17.16+/-0.95)microm and (3.20+/-0.52)x10(3)fL of JE cells (P<0.05). The doubling time of LJE cells, was longer than that of JE cells.CK19 expression of LJE cells was weaker than of JE cells and there were no difference in the expression pattern of CK6 and CK13. Compared with control cells, the early- and late-stage apoptosis ratio of LJE cells were (4.62+/-2.16)% and (9.46+/-1.84)%, respectively which were all higher than JE cells which were (0.47+/-0.63)% and (3.84+/-0.98)% (P<0.05). CONCLUSION: There is difference between LJE and JE cells in dimension, CK19 expression, proliferation time and apoptosis. This study provides some clinical significance and aid in understanding the biological characteristics of LJE and the healing process of periodontitis.

Preparation and properties of a novel biodegradable polyester elastomer with functional groups.

A novel biodegradable poly(sebacate-glycerol-citrate) (PGSC) elastomer with functional groups was prepared in this study. First, moldable mixtures were obtained by mixing citric acid with the poly(glycerol-sebacate) (PGS) pre-polymers synthesized in our lab. The PGSC elastomers were obtained from moldable mixtures that were thermally cured in the moulds. Then, the structures, compositions and properties of the elastomers were studied by Fourier transformation infrared spectroscopy (FT-IR), swelling test, differential scanning calorimeter (DSC), tensile test, water contact angle measurement, water absorption experiments and a in vitro degradation test. It showed that the hydroxyl groups remained in the elastomers which would endow the polymer chains with functionality such as good surface modification. By controlling the thermal curing time, the compositions of the PGSC elastomers were adjusted for different mechanical and biodegradable properties. Therefore, PGSC elastomers might be used as anti-conglutination films in surgery, guided tissue regeneration membranes and drug-delivery matrices.