High Oxidation Stability of Tea Polyphenol-stabilized Highly Crosslinked UHMWPE Under an in Vitro Aggressive Oxidative Condition.

BACKGROUND: Synovial fluid components, especially lipids, can trigger oxidation of ultrahigh-molecular-weight polyethylene (UHMWPE) artificial joint components in vivo. The use of antioxidants such as vitamin E effectively diminishes the oxidative cascade by capturing free radicals and reducing the oxidation potential of UHMWPE implants. Using a thermo-oxidative aging method, we recently found that tea polyphenols can enhance the oxidation resistance of irradiated UHMWPE in comparison with commercial vitamin E. However, it is yet unknown whether tea polyphenols can reduce lipid-induced oxidation. QUESTIONS/PURPOSES: We explored whether tea polyphenol-stabilized UHMWPE would exhibit (1) lower squalene absorption; (2) stronger oxidation resistance; and (3) lower content of free radicals than vitamin E-stabilized UHMWPE under a physiologically-motivated in vitro accelerated-aging model. METHODS: Tea polyphenol (lipid-soluble epigallocatechin gallate [lsEGCG]) and vitamin E were blended with UHMWPE powders followed by compression molding and electron beam irradiation at 100 and 150 kGy. Small cubes (n = 3, 60 mg, 4 × 4 × 4 mm) cut from the blocks were doped in squalene at 60°, 80°, 100°, and 120° C for 2 hours. Gravimetric change of the cubes after squalene immersion was measured to assess absorption. Thin films (n = 3, ∼60 µm) were also microtomed from the blocks and were doped at 120° C for 24 hours. Oxidation induction time (n = 3, 5 mg of material from the cubes) and incipient oxidation temperature (n = 3, thin films) were obtained to determine the oxidation stability. Signal intensity of the free radicals, obtained by electron spin resonance spectroscopy, was used to qualitatively rank the antioxidant ability of vitamin E and lsEGCG. RESULTS: Squalene absorption was comparable between lsEGCG/UHMWPE and vitamin E/UHMWPE at a given temperature and radiation dose. The oxidation induction time of 100 kGy-irradiated UHMWPE was increased with lsEGCG compared with vitamin E except at 120° C. For example, the oxidation induction time value of 100 kGy-irradiated lsEGCG/UHMWPE immersed at 60 C was 25.3 minutes (24.2-27.8 minutes), which was 8.3 minutes longer than that of 100 kGy-irradiated vitamin E/UHMWPE which was 17.0 minutes (15.0-17.1 minutes) (p = 0.040). After squalene immersion at 120° C, the incipient oxidation temperature of 100 and 150 kGy irradiated lsEGCG/UHMWPE was 234° C (227-240° C) and 227° C (225-229° C), which was higher than vitamin E-stabilized counterparts with value of 217° C (214-229° C; p = 0.095) and 216° C (207-218° C; p = 0.040), respectively. The electron spin resonance signal of 150 kGy irradiated lsEGCG/UHMWPE was qualitatively weaker than that of 150 kGy irradiated vitamin E/UHMWPE. CONCLUSIONS: lsEGCG-stabilized UHMWPE demonstrated higher oxidation resistance than vitamin E-stabilized UHMWPE after squalene immersion, likely because lsEGCG donates more protons to eliminate macroradicals than vitamin E. CLINICAL RELEVANCE: Our in vitro findings provide support that lsEGCG may be effective in protecting against oxidation that may be associated with synovial fluid-associated oxidation of highly crosslinked UHMWPE joint replacement components.

Characterization of a Thermoresponsive Chitosan Derivative as a Potential Draw Solute for Forward Osmosis.

A thermoresponsive chitosan derivative was synthesized by reacting chitosan (CS) with butyl glycidyl ether (BGE) to break the inter- and intramolecular hydrogen bonds of the polymer. An aqueous solution of the thermoresponsive CS derivative exhibits a lower critical solution temperature (LCST) than CS, and it undergoes a phase transition separation when the temperature changes. Successful incorporation of BGE into the CS was confirmed by FTIR and XPS analyses. Varying the BGE content and the concentration of the aqueous solution produced different LCST ranges, as shown by transmittance vs temperature curves. The particle size was observed by scanning electron microscopy, which revealed that the particles were smaller and well dispersed at 15 °C, whereas the particles became larger and tended to aggregate at 60 °C. A similar trend was observed with the mean particle size measured using dynamic light scattering. Positron annihilation lifetime spectroscopy data also revealed the reversibility of the particle properties as a function of temperature. Microstructure analysis showed that the particles had larger free-volume sizes at 15 °C than at 60 °C. The particles were also found to be nontoxic with 92% cell survival. A simple forward osmosis (FO) test for dye dehydration revealed the potential use of the thermoresponsive chitosan derivative as a draw solute with a flux of 8.6 L/m2 h and rejection of 99.8%.

Appliance-induced osteopenia of dentoalveolar bone in the rat: effect of reduced bone strains on serum bone markers and the multifunctional hormone leptin.

To understand, in greater detail, the molecular mechanisms regulating the complex relationship between mechanical strain and alveolar bone metabolism during orthodontic treatment, passive cross-arch palatal springs were bonded to the maxillary molars of 6-wk-old rats, which were killed after 4 and 8 d. Outcome measures included serum assays for markers of bone formation and resorption and for the multifunctional hormone leptin, and histomorphometry of the inter-radicular bone. The concentration of the bone-formation marker alkaline phosphatase (ALP) was significantly reduced at both time points in the appliance group, accompanied by a 50% reduction in inter-radicular bone volume; however, osteocalcin (bone Gla protein) levels remained unaffected. Bone collagen deoxypyridinoline (DPD) crosslinks increased 2.3-fold at 4 d only, indicating a transient increase in bone resorption; in contrast, the level of the osteoclast-specific marker, tartrate-resistant acid phosphatase 5b (TRACP 5b), was unchanged. Leptin levels closely paralleled ALP reductions at both time points, suggesting an important role in the mechanostat negative-feedback loop required to normalize bone mass. These data suggest that an orthodontic appliance, in addition to remodeling the periodontal ligament (PDL)-bone interface, may exert unexpected side-effects on the tooth-supporting alveolar bone, and highlights the importance of recognizing that bone strains can have negative, as well as positive, effects on bone mass.

[Three-dimension model analysis for physiological drift of the mandibular dentition after extraction of mandibular second premolars of Angle class II patients].

OBJECTIVE: To observe the self-adjustment of the mandibular dental arch after extraction of the second mandibular premolars. METHODS: Mandibular dental casts of 20 Angle class II patients treated with extraction of lower second premolars and upper first premolars, bonded with Alexander appliance,were taken before (T1) and after self-adjustment (T2). All the casts were laser scanned, Little index, curve of Spee, arch width, arch length and extraction spaces of casts were digitally measured and analyzed with SPSS 16.0. RESULTS: Little index,lower molar width, lower arch length and extraction spaces were reduced [(12.70±3.28) mm vs.(8.82±2.69) mm, P<0.001;(41.21±2.48) mm vs.(40.54±2.23) mm, P<0.001; (24.63±3.19) mm vs.(22.12±2.97) mm, P<0.001;(8.06±0.48) mm vs.(4.17±1.51) mm, P<0.001;(8.13±0.95) mm vs.(4.14±1.98) mm, P<0.001],while the curve of Spee and anterior lower arch length were increased significantly[(2.14±0.75) mm vs.(2.65±0.88) mm, P<0.05; (15.88±2.86) mm vs.(17.55±2.33) mm, P<0.05]. Width between lower canines remained the same[(27.25±2.69) mm vs.(27.26±1.73) mm, P>0 .05]. CONCLUSION: Severe crowding and Angle class II molar relationship could be successfully relived with lower second premolar extraction followed by self-adjustment.

Multilayered poly(vinylidene fluoride) composite membranes with improved interfacial compatibility: correlating pervaporation performance with free volume properties.

A spin-coating process integrated with an ozone-induced graft polymerization technique was applied in this study. The purpose was to improve the poor interfacial compatibility between a selective layer of poly(2-hydroxyethyl methacrylate) (PHEMA) and the surface of a poly(vinylidene fluoride) (PVDF) substrate. The composite membranes thus fabricated were tested for their pervaporation performance in dehydrating an ethyl acetate/water mixture. Furthermore, the composite membranes were characterized by field emission scanning electron microscopy (FE-SEM) for morphological change observation and by Fourier transform infrared spectroscopy equipped with attenuated total reflectance (ATR-FTIR) for surface chemical composition analysis. Effects of grafting density and spin-coating speed on pervaporation performance were examined. The composite membrane pervaporation performance was elucidated by means of free volume and depth profile data obtained with the use of a variable monoenergy slow positron beam (VMSPB). Results indicated that a smaller free volume was correlated with a higher pervaporation performance of a composite membrane consisting of a selective layer of spin-coated PHEMA on a PHEMA-grafted PVDF substrate (S-PHEMA/PHEMA-g-PVDF). The composite membrane depth profile illustrated that an S-PHEMA layer spin-coated at a higher revolutions per minute (rpm) was thinner and denser than that at a lower rpm.

Phosphonium Modification Leads to Ultrapermeable Antibacterial Polyamide Composite Membranes with Unreduced Thickness.

Water transport rate in network membranes is inversely correlated to thickness, thus superior permeance is achievable with ultrathin membranes prepared by complicated methods circumventing nanofilm weakness and defects. Conferring ultrahigh permeance to easily prepared thicker membranes remains challenging. Here, a tetrakis(hydroxymethyl) phosphonium chloride (THPC) monomer is discovered that enables straightforward modification of polyamide composite membranes. Water permeance of the modified membrane is ≈6 times improved, give rising to permeability (permeance × thickness) one magnitude higher than state-of-the-art polymer nanofiltration membranes. Meanwhile, the membrane exhibits good rejection (RNa2SO4 = 98%) and antibacterial properties under crossflow conditions. THPC modification not only improves membrane hydrophilicity, but also creates additional angstrom-scale channels in polyamide membranes for unimpeded transport of water. This unique mechanism provides a paradigm shift in facile preparation of ultrapermeable membranes with unreduced thickness for clean water and desalination.

Cationic nanoparticle as an inhibitor of cell-free DNA-induced inflammation.

Cell-free DNA (cfDNA) released from damaged or dead cells can activate DNA sensors that exacerbate the pathogenesis of rheumatoid arthritis (RA). Here we show that ~40 nm cationic nanoparticles (cNP) can scavenge cfDNA derived from RA patients and inhibit the activation of primary synovial fluid monocytes and fibroblast-like synoviocytes. Using clinical scoring, micro-CT images, MRI, and histology, we show that intravenous injection of cNP into a CpG-induced mouse model or collagen-induced arthritis rat model can relieve RA symptoms including ankle and tissue swelling, and bone and cartilage damage. This culminates in the manifestation of partial mobility recovery of the treated rats in a rotational cage test. Mechanistic studies on intracellular trafficking and biodistribution of cNP, as well as measurement of cytokine expression in the joints and cfDNA levels in systemic circulation and inflamed joints also correlate with therapeutic outcomes. This work suggests a new direction of nanomedicine in treating inflammatory diseases.

Biocompatibility and characterization of polylactic acid/styrene-ethylene-butylene-styrene composites.

Polylactic acid (PLA)/styrene-ethylene-butylene-styrene (SEBS) composites were prepared by melt blending. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WXRD) were used to characterize PLA and PLA/SEBS composites in terms of their melting behavior and crystallization. Curves from thermal gravimetric analysis (TGA) illustrated that thermostability increased with SEBS content. Further morphological analysis of PLA/SEBS composites revealed that SEBS molecules were not miscible with PLA molecules in PLA/SEBS composites. The tensile testing for PLA and PLA/SEBS composites showed that the elongation at the break was enhanced, but tensile strength decreased with increasing SEBS content. L929 fibroblast cells were chosen to assess the cytocompatibility; the cell growth of PLA was found to decrease with increasing SEBS content. This study proposes possible reasons for these properties of PLA/SEBS composites.

[Analysis of the plaster casts of Class II division 1 non-extraction patients treated with Alexander technique].

OBJECTIVE: To investigate the changes of arch width and arch length in Class II division 1 non-extraction patients treated with Alexander technique. METHODS: Dental casts of 21 Class II division 1 non-extraction patients treated with Alexander appliance were taken before (T1) and after treatment (T2). All the casts were laser scanned. The arch width and arch length were digitally measured. The differences of arch width and arch length between T1 and T2 were recorded and analyzed. RESULTS: The upper arch length decreased from (32.82 ± 2.51) mm to (31.97 ± 2.17) mm (P < 0.05). The lower arch length increased from (27.53 ± 2.61) mm to (28.80 ± 1.81) mm (P < 0.05). The intercanine width in the upper arch changed significantly from T1 to T2. The intermolar width in the upper and lower arches increased significantly from T1 to T2. CONCLUSIONS: Class II division 1 non-extraction patients could be treated successfully by increasing the upper arch width.

Tuning nanostructure of graphene oxide/polyelectrolyte LbL assemblies by controlling pH of GO suspension to fabricate transparent and super gas barrier films.

A technique of layer-by-layer (LbL) self-assembly was used to prepare transparent multilayered gas barrier films consisting of graphene oxide (GO)/branched poly(ethylenimine) (BPEI) on a poly(ethylene terephthalate) substrate. The effect of the GO suspension pH on the nanostructure and oxygen barrier properties of the GO/BPEI film was investigated. The oxygen barrier properties of the assemblies were shown to be highly dependent on the pH. It was demonstrated that the film assemblies prepared using a GO suspension with a pH of 3.5 exhibited very dense and ordered structures and delivered very low oxygen transmission rates (the lowest was <0.05 cm(3) m(-2) day(-1)). The assemblies were characterized with ultraviolet-visible spectroscopy and ellipsometry to identify the film growth mechanism, and the result indicated a linear growth behavior. To analyze the nanostructure of the films, atomic force microscopy, transmission electronic microscopy, and grazing incidence wide-angle X-ray diffraction were used.

[Posttreatment stability of four first bicuspid extraction cases treated with the Alexander technique--model analysis].

OBJECTIVE: To evaluate the posttreatment stability of four first bicuspid extraction cases with the Alexander technique. METHODS: Fifteen patients, 8 males and 7 females in the permanent dentition were selected. The age range of the patients was 10.3 to 16.2 years old. Four first bicuspids of every patient were extracted and all patients were treated with the Alexander technique. The study casts were taken before (T(1)), after treatment (T(2)) and 27.8 months averagely follow-up (T(3)). Data were correlated by means of paired t tests. RESULTS: Although maxillary and mandibular intercanine widths were increased by 0.98 mm and 0.87 mm, respectively, during treatment, they were decreased by 0.37 mm and 0.72 mm, respectively, during follow-up period. Maxillary and mandibular crowding were increased by 0.53 mm and 0.98 mm, respectively, during follow-up period. No statistical significance were found. Upper and lower arch depth were decreased significantly due to retraction of anterior teeth and remained stable during follow-up period. CONCLUSIONS: According to this study, the design of the Alexander appliance and the Alexander technique are helpful for stability of extraction therapy. Follow-up is still necessary to evaluate the long-term stability.