Highly Tough and Reliable Poly(Amic Acid) with Ballistic Impact-Resistance through Modulation of Hydrogen Bonding Interactions.

Poly(amic acid) (PAA) materials as the precursor of polyimide generally show remarkably poor mechanical properties, thus limiting their application as the engineering plastics. In this study, it is demonstrated that the mechanical properties of PAA materials can be improved significantly for tens of folds with breaking strength >50 MPa, Young's modulus >400 MPa, and elongation at break >300% by incorporation of 20% (mol%) poly(propylene glycol) (PPO) soft segments. The optimization for suitable hard-soft composition with 20% PPO and the existence of various hydrogen bonds with different binding energies can dissipate energies efficiently, which simultaneously improve the material strength and toughness. In addition, PAA82 films exhibit excellent tolerance toward cyclic stretch, and have the capability to resist various harsh conditions including solar radiation testing (1 sun), heat (85 °C), alkalinity (pH 10), and acidity (pH 4) over one month. Noted that PAA82 films can be laminated with Kapton films, which show excellent resistance to ultrahigh (200 °C) and ultralow temperature (-196 °C). The laminated film also exhibits bulletproof property with a thickness of 6 mm. The strategy via modulation of hard-soft compositions and hydrogen bonds in PAA materials shows great potentials to improve the mechanical properties of polymeric materials.

Coordination Polymer-Mediated Molecular Surgery for Precise Interconversion of Dicyclobutane Compounds.

A Cd(II)-based coordination polymer {[Cd2(5-F-1,3-bpeb)2(FBA)4]·H2O}n (CP1) was obtained from Cd(II) salt, 5-fluoro-1,3-bis[2-(4-pyridyl)ethenyl]benzene (5-F-1,3-bpeb), and p-fluorobenzoic acid (HFBA). Within the one-dimensional chain structure of CP1, a pair of 5-F-1,3-bpeb was arranged in a face-to-face style. Upon UV irradiation and heat treatment, multiple cyclobutane isomers, including specific monocyclobutanes (1 with an endo-cyclobutane ring in CP1-1 and 1' with an exo-cyclobutane ring in CP1-1') and dicyclobutanes (endo,endo-dicyclobutane 2α in CP1-2α, exo,endo-dicyclobutane 2ß in CP1-2ß, and exo,exo-dicyclobutane 2γ in CP1-2γ) were stereoselectively produced. These isomers could be interconverted inside the CP via cutting/coupling specific bonds, which may be regarded as a type of molecular surgery. The precision of cutting/coupling relied on the thermal stability of the cyclobutanes and the alignment of the reactive alkene centers. The conversion processes were tracked through nuclear magnetic resonance, in situ powder X-ray diffraction, and IR spectroscopy. This approach can be considered as skeletal editing to construct complex organic compounds directly from one precursor.

A chiral porous organic polymer COP-1 used as stationary phase for HPLC enantioseparation under normal-phase and reversed-phase conditions.

A spherical chiral porous organic polymer (POPs) COP-1 is synthesized by the Friedel-Crafts alkylation reaction of Boc-3-(4-biphenyl)-L-alanine (BBLA) and 4,4'-bis(chloromethyl)-1,1'-biphenyl (BCMBP), which was used as a novel chiral stationary phase (CSPs) for mixed-mode high-performance liquid chromatography (HPLC) enantioseparation. The racemic compounds were resolved in normal-phase liquid chromatography (NPLC) using n-hexane/isopropanol as mobile phase and reversed-phase liquid chromatography (RPLC) using methanol/water as mobile phase. The COP-1-packed column exhibited excellent separation performance toward various racemic compounds including alcohols, amines, ketones, esters, epoxy compounds, organic acids, and amino acids in NPLC and RPLC modes. The effects of analyte mass and column temperature on the separation efficiency of racemic compounds were investigated. In addition, the chiral resolution ability of the COP-1-packed column not only can be complementary in RPLC/NPLC modes but also exhibit a good chiral recognition complementarity with Chiralpak AD-H column and chiral porous organic cage (POC) NC1-R column. The relative standard deviations (RSD) (n = 5) of the retention time, resolution value, and peak area by repeated separation of 1-(4-chiorophenyl)ethanol are all below 3.0%. The COP-1 column shows high column efficiency (e.g., 17,320 plates m-1 for 1-(4-chlorophenyl)ethanol on COP-1 column in NPLC), high enantioselectivity, and good reproducibility toward various racemates. This work demonstrates that chiral POPs microspheres are promising chiral materials for HPLC enantioseparation.

A pH-Responsive Zwitterionic Polyurethane Prodrug as Drug Delivery System for Enhanced Cancer Therapy.

Numerous nanocarriers with excellent biocompatibilities have been used to improve cancer therapy. However, nonspecific protein adsorption of nanocarriers may block the modified nanoparticles in tumor cells, which would lead to inefficient cellular internalization. To address this issue, pH-responsive polyurethane prodrug micelles with a zwitterionic segment were designed and prepared. The micelle consisted of a zwitterionic segment as the hydrophilic shell and the drug Adriamycin (DOX) as the hydrophobic inner core. As a pH-responsive antitumor drug delivery system, the prodrug micelles showed high stability in a physiological environment and continuously released the drug under acidic conditions. In addition, the pure polyurethane carrier was demonstrated to be virtually non-cytotoxic by cytotoxicity studies, while the prodrug micelles were more efficient in killing tumor cells compared to PEG-PLGA@DOX. Furthermore, the DOX cellular uptake efficiency of prodrug micelles was proved to be obviously higher than the control group by both flow cytometry and fluorescence microscopy. This is mainly due to the modification of a zwitterionic segment with PU. The simple design of zwitterionic prodrug micelles provides a new strategy for designing novel antitumor drug delivery systems with enhanced cellular uptake rates.

Intermediate analysis of magnesium alloy covered stent for a lateral aneurysm model in the rabbit common carotid artery.

OBJECTIVE: To analyze the outcomes of a magnesium alloy covered stent (MACS) for a lateral aneurysm model in common carotid artery (CCA). METHODS: In 32 rabbits, a MACS (group A, n = 17) or a Willis covered stent (WCS; group B, n = 15) was inserted and the rabbits were sacrificed 1, 3, 6, or 12 months after stenting. Angiography and intravascular ultrasound (IVUS) were performed at 3, 6, and 12 months. Scanning electron microscopy was performed for six stents in each group at 1, 3, and 6 months, and histopathology and histomorphology were conducted at 3 (n = 4), 6 (n = 4), and 12 (n = 12) months. RESULTS: Final angiography showed complete occlusion of the aneurysms in 12 cases. IVUS at 6 and 12 months revealed a significant increase in mean lumen area of the stented CCA in group A and also showed greater mean lumen area in group A than in group B. The endothelialization process was quicker in group A than in group B. CONCLUSION: MACS is effective for occlusion of lateral aneurysms and is superior to WCS in growth of the stented CCA and endothelialization. Further work is needed to make this device available for human use. KEY POINTS: • The MACS is an effective approach for occlusion of a lateral aneurysm. • IVUS showed that the CCA could grow following degradation of the MACS. • The lumen area of the stented CCA was excellent in MACS. • HE staining displayed the degradation of the magnesium alloy stent. • Combination of IVUS and DSA were applied in this study.

Piezoelectric Sensor to Measure Soft and Hard Stiffness with High Sensitivity for Ultrasonic Transducers.

During dental sinus lift surgery, it is important to monitor the thickness of the remaining maxilla to avoid perforating the sinus membrane. Therefore, a sensor should be integrated into ultrasonic dental tools to prevent undesirable damage. This paper presents a piezoelectric (PZT) sensor installed in an ultrasonic transducer to measure the stiffness of high and low materials. Four design types using three PZT ring materials and a split PZT for actuator and sensor ring materials were studied. Three sensor locations were also examined. The voltage signals of the sensor and the displacement of the actuator were analyzed to distinguish the low and high stiffness. Using sensor type T1 made of the PZT-1 material and the front location A1 provided a high sensitivity of 2.47 Vm/kN. The experimental results demonstrated that our design can measure soft and hard stiffness.

[Association between chronic periodontitis and metabolic syndrome related mitochondria single nucleotide polymorphism].

OBJECTIVE: To investigate the relationship between Mitochondrial DNA(mtDNA) SNP and the severity of periodontitis. METHODS: In the study, 227 subjects in a community of Beijing received questionnaire interview, periodontal examination and biochemical laboratory examination in 2005. The designed primer was used to amplify the specific mtDNA fragments with PCR, and sequence the PCR products. Finally, the relationship between severity of chronic periodontitis and mtDNA SNP at site 10398 was analyzed. RESULTS: The number of the subjects included at mtDNA site 10398 was 227. The G allele frequency in the metabolic syndrome(MS) subjects was significantly higher than that in the non MS subjects [80(70.2%) vs. 34(29.8%),P=0.039 ]. The result of Logistic regression showed that the subjects with G allele had higher risk of MS than the subjects with A allele(OR=1.77,95%CI=1.02-3.06, P=0.042). But there was no significant relationship between the 10398 A→G SNP and severity of periodontitis. CONCLUSION: In this population, mtDNA SNP 10398 A→G may be associated with MS. However, there was no relationship between the 10398 A→G SNP and severity of chronic periodontitis.

Double Candida antarctica lipase B co-display on Pichia pastoris cell surface based on a self-processing foot-and-mouth disease virus 2A peptide.

To develop a high efficiency Candida antarctica lipase B (CALB) yeast display system, we linked two CALB genes fused with Sacchromyces cerevisiae cell wall protein genes, the Sed1 and the 3'-terminal half of Sag1, separately by a 2A peptide of foot-and-mouth disease virus (FMDV) in a single open reading frame. The CALB copy number of recombinant strain KCSe2ACSa that harbored the ORF was identified, and the quantity of CALB displayed on the cell surface and the enzyme activity of the strain were measured. The results showed that the fusion of multiple genes linked by 2A peptide was translated into two independent proteins displayed on the cell surface of stain KCSe2ACSa. Judging from the data of immunolabeling assay, stain KCSe2ACSa displayed 94 % CALB-Sed1p compared with stain KCSe1 that harbored a single copy CALB-Sed1 and 64 % CALB-Sag1p compared with stain KCSa that harbored a single copy CALB-Sag1 on its surface. Besides, strain KCSe2ACSa possessed 170 % hydrolytic activity and 155 % synthetic activity compared with strain KCSe1 as well as 144 % hydrolytic activity and 121 % synthetic activity compared with strain KCSa. Strain KCSe2ACSa even owned 124 % hydrolytic activity compared with strain KCSe2 that harbored two copies CALB-Sed1. The heterogeneous glycosylphosphatidylinositol-anchored proteins co-displaying yeast system mediated by FMDV 2A peptide was shown to be an effective method for improving the efficiency of enzyme-displaying yeast biocatalysts.

[A controlled study on the treatment of acute progressive cerebral infarction by continuous anticoagulation with small doses of heparin].

OBJECTIVE: To discuss the treatment of acute progressive cerebral infarction by continuous anticoagulation with small doses of heparin. METHODS: A prospective, randomized, and controlled clinical research was conducted. Three hundred and fifty-one patients were randomly divided into three groups. Group A (n=119) was treated with heparin, which was controlled by an infusion pump with a speed of 18 U×kg(-1)×h(-1) for 24 hours, and the dosage was regulated according to the changes in activated partial thromboplastin time (APTT) which was determined every 8 hours. Group B (n=115) was treated with intravenous drip of 12,500 U of heparin with a speed of 18 U×kg(-1)×h(-1) once a day. Group C (n=117) was treated with 5000 U of low-molecular-weight heparin calcium injection twice a day. After 14 days, nerve function defect according to the National Institutes of Heath stroke scale (NIHSS) score was determined, the adverse events (e.g. intracranial hemorrhage, subcutaneous ecchymosis, gingival bleeding, hematuria and occult blood in stools) were observed. After 6 months, the recurrence rate and Barthel index (BI) would be determined. RESULTS: The total efficiency in group A (95.80%) was significantly higher than that in group B (85.22%) and group C (85.47%). Recurrence rate in group A (1.68%) was significantly lower than group B (8.70%) and group C (8.33%) with significant differences (P<0.05 or P<0.01), while there was no significant difference between group B and group C (both P>0.05). The BI of group A (89.27±8.56) was significantly higher than group B (72.57±9.77) and group C (71.66±9.37) with significant difference (both P<0.01), while there was no significant difference between group B and group C (P>0.05). Adverse event rate in group A (5.88%) was slightly higher than that of group B (3.48%) and group C (4.27%), but the difference was not significant (both P>0.05). CONCLUSIONS: Continuous infusion of low dosage of heparin could significantly reduce neurologic impairment score in patients with progressive cerebral infarction, increase cure rate, reduce the recurrence rate, and raise the BI of patients, and it dose not increase the risk of intracranial and extracranial hemorrhage.

Light-driven self-healing polyurethane based on PDA@Ag nanoparticles with improved mechanical and antibacterial properties.

To endow the polyurethane (PU) coating with antimicrobial and self-healing ability, a PU composite film (PUDA@Ag) based on furfuryl functional polydopamine nanoparticles (FPDA NPs) and Diels-Alder (DA) reaction was prepared successfully. Herein, FPDA NPs were added to maleimide-terminated PU by DA reaction as cross-linking agents and photothermal fillers. Owing to the excellent photothermal effect of PDA NPs and the existence of DA bonds, the PUDA@Ag film had superior self-healing performance (90%). Importantly, with the existence of FPDA@Ag, the PU composite films showed comprehensive mechanical properties (tensile strength up to 50 MPa, toughness of 153.9 MJ m-3, and elongation at break of 895%). Silver nanoparticles (AgNPs) as antibacterial agents and nanofillers endowed the PUDA@Ag with excellent antibacterial and long-term antibacterial properties against Gram-negative E. coli and Gram-positive S. aureus. This work provides a reasonable method to prepare multi-responsive self-healing PU composite films with super-high strength and antimicrobial properties that have great potential in the fields of biomedicine, coating, and thermal management.

Synthesis of hierarchical hollow silica microspheres containing surface nanoparticles employing the quasi-hard template of poly(4-vinylpyridine) microspheres.

A facile method of preparing hierarchical hollow silica microspheres containing surface silica nanoparticles (HHSMs) through the sol-gel process of tetraethylorthosilicate employing a quasi-hard template of non-cross-linking poly(4-vinylpyridine) microspheres is proposed. The quasi-hard template contains the inherent catalyst of the basic pyridine group, and a few of the polymer chains can escape from the template matrix into the aqueous phase, which initiates the sol-gel process spontaneously both on the surface of the template used to prepare the hollow silica shell and in the aqueous phase to produce the surface silica nanoparticles. By tuning the weight ratio of the silica precursor to the quasi-hard template, HHSMs with a size of about 180 nm and a shell thickness ranging from 14 to 32 nm and surface silica nanoparticles ranging from 17 to 36 nm are produced initially through the deposition of surface silica nanoparticles onto the silica shell, followed by template removal either by calcination or solvent extraction. The synthesized HHSMs are characterized, and a possible mechanism for the synthesis of HHSMs is proposed.

The association of tooth loss, toothbrushing, and quality of life among cancer survivors.

BACKGROUND: Tooth loss contributes physically and psychologically to health, and quality of life has been a key indicator of the cancer survivors. However, it is less clear whether tooth loss has impact on cancer survivors' quality of life. Our study aimed to investigate the association between tooth loss, toothbrushing, and quality of life in cancer survivors. METHODS: A cross-sectional study was conducted among 9125 cancer survivors in Shanghai, China. Sociodemographic characteristics, frequency of tooth brushing, number of tooth loss were collected using a self-reported questionnaire. Quality of life was measured using the EORTC QLQ-C30. Chi-square test was used to compare the distribution of tooth loss and toothbrushing frequency among various cancer sites, sociodemographic factors, socioeconomic status, health conditions. Multiple linear regression models were performed to estimate the effects of tooth loss and toothbrushing on quality of life. RESULTS: Participants diagnosed with cancer of oral cavity, pharynx, and nasopharynx reported higher percentage of 11+ tooth loss. Cancer survivors with toothbrushing ≥2 times/d reported higher scores in physical, cognitive, and social function and had milder nausea and vomiting, compared with ones with toothbrushing <2 times/d. Tooth loss was associated with milder physical, role and emotional function scores, and severer fatigue, nausea/vomiting, dyspnea, insomnia, appetite loss, constipation, and diarrhea. CONCLUSIONS: This is the first study to investigate the impact of toothbrushing and tooth loss on quality of life among cancer survivors. Tooth loss was associated with milder physical, role and emotional function scores, and severer fatigue, nausea/vomiting, dyspnea, insomnia, appetite loss, constipation and diarrhea. Toothbrushing had significant positive effect on cancer survivors' quality of life. The present study also provided several public health strategies to improve oral health among cancer survivors.

Synthesis of porous poly(styrene-co-acrylic acid) microspheres through one-step soap-free emulsion polymerization: whys and wherefores.

Synthesis of porous poly(styrene-co-acrylic acid) (PS-co-PAA) microspheres through one-step soap-free emulsion polymerization is reported. Various porous PS-co-PAA microspheres with the particle size ranging from 150 to 240 nm and with the pore size ranging from 4 to 25 nm are fabricated. The porous structure of the microspheres is confirmed by the transmission electron microscopy measurement and Brunauer-Emmett-Teller (BET) analysis. The reason for synthesis of the porous PS-co-PAA microspheres is discussed, and the phase separation between the encapsulated hydrophilic poly(acrylic acid) segment and the hydrophobic polystyrene domain within the PS-co-PAA microspheres is ascribed to the pore formation. The present synthesis of the porous PS-co-PAA microspheres is anticipated to be a new and convenient way to fabricate porous polymeric particles.

Polyvinyl alcohol-ionic liquid composition for promoting the direct electron transfer and electrocatalysis of hemoglobin.

The direct electron transfer and electrocatalysis of hemoglobin (Hb) entrapped in polyvinyl alcohol (PVA)-room temperature ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM]PF(6)) composition has been investigated by using cyclic voltammetry and chronocoulometry. It is found that the composition can promote the direct electron transfer of Hb and the heterogeneous electron transfer rate constant (k(s)) of immobilized Hb is enhanced to 19.9 s(-1). The immobilized Hb also shows high electro-catalytic activity towards the redox of oxygen, hydrogen peroxide and nitrite. The Michaelis constants (K(m)) decrease to 1.2x10(-4) M (for hydrogen peroxide) and 9.4x10(-3) M (for nitrite). The surface concentration of electroactive Hb is estimated and it is ca. 1.4x10(-10) mol cm(-2), meaning that several layers of immobilized Hb take part in the electrochemical reaction. When gold nanoparticles (GNP) is introduced into the composition, the resulting PVA-GNP-[OMIM]PF(6) composition presents better performance. The electrochemical characteristic of immobilized Hb is improved further. Thus PVA-GNP-[OMIM]PF(6) composition is more suitable for the immobilization of Hb. Therefore, it is a good strategy to prepare novel composition for protein immobilization by using several materials with different function.

Intermittent watt-level ultrasonication facilitates vancomycin release from therapeutic acrylic bone cement.

Ultrasound holds promise for enhancing the vancomycin release from cement though the length of time when local drug level exceeded the minimum inhibitory concentration (T(>MIC)) was not prolonged by the previous protocol of milliwatt-level ultrasonication. Here vancomycin-loaded cements were subjected to continuous watt-level ultrasonication (CUG), intermittent watt-level ultrasonication (IUG) or no ultrasonication (NUG) for 14 d during immersion in 40-ml phosphate buffered saline (PBS) for 28 d. The T(>MIC) for IUG was more than three times that for NUG. In contrast, T(>MIC) for CUG was slightly shortened. The subtherapeutic release of vancomycin between 15 d and 28 d for IUG was one-ninth that for NUG. The fitting equations indicated a significant enhancement on the burst release and the slow release for IUG; however, the continuous ultrasonication hampered the slow release. SEM images exhibited denser craters and pores with larger diameters and less residual drug in specimens from IUG relative to those from both CUG and NUG. Intermittent watt-level ultrasonication improved the ultrasound-enhanced vancomycin release from cement in view of the prolonged T(>MIC) and the inhibited subtherapeutic release compared with continuous ultrasonication. The mechanisms may be associated with the distinctive effects of detaching forces and pushing forces by acoustic microstreams.

Effect of delayed pulsed-wave ultrasound on local pharmacokinetics and pharmacodynamics of vancomycin-loaded acrylic bone cement in vivo.

This study sought to investigate the effect of delayed pulsed-wave ultrasound with low frequency on drug release from and the antimicrobial efficacy of vancomycin-loaded acrylic bone cement in vivo and the possible mechanism of this effect. After the implantation of cement and the inoculation of Staphylococcus aureus into the bilateral hips of rabbits, ultrasound (average intensity, 300 mW/cm(2); frequency, 46.5 kHz; on/off ratio, 20 min/10 min) was applied to animals in the normal ultrasound group (UG(0-12)) from 0 through 12 h after surgery and to those in the delayed-ultrasound group (UG(12-24)) from 12 through 24 h after surgery. The control group (CG) was not exposed to ultrasound. Based on vancomycin concentrations in left hip cavities at projected time intervals, the amount of time during which the local drug concentration exceeded the MIC (T(>MIC)) in UG(12-24) was significantly prolonged compared with that in either CG or UG(0-12), and the ratios between the areas under the concentration-time curves over 24 h and the MIC for UG(0-12) and UG(12-24) were both increased compared with that for CG. The greatest reductions in bacterial densities in both right hip aspirates and right femoral tissues at 48 h were achieved with UG(12-24). Local hemorrhage in rabbits of UG(0-12) during the 12-h insonation was more severe than that in rabbits of UG(12-24). Of four variables, the T(>MIC) and the bioacoustic effect were both identified as parameters predictive of the enhancement of the antimicrobial efficacy of cement by ultrasound. Sustained concentrations above the MIC replaced early high maximum concentrations and long-term subtherapeutic release of the drug, provided that ultrasound was not applied until local hemorrhage was relieved. The enhancement of the antimicrobial efficacy of cement by ultrasound may be attributed to the prolonged T(>MIC) and the bioacoustic effect caused by ultrasound.