Study on Enhancing the Corrosion Resistance and Photo-Thermal Antibacterial Properties of the Micro-Arc Oxidation Coating Fabricated on Medical Magnesium Alloy.

Photo-thermal antibacterial properties have attracted much attention in the biomedical field because of their higher antibacterial efficiency. Through fabricating micro-arc oxidation coatings with different treating current densities set on a Mg-Zn-Ca alloy, the present study tried to systematically investigate and optimize the corrosion resistance and photo-thermal antibacterial properties of MAO coatings. The results indicated that different current densities had great influence on the corrosion resistance and photo-thermal property of the MAO coatings, and a current density at 30 A·dm-2 exhibited the best corrosion resistance, light absorption capacity at 808 nm, and photo-thermal capability, simultaneously with good antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). This photo-thermal property of MAO coatings was probably related to the effect of current density on MgO content in the coating that could promote the separation of photo-generated electron carriers and hinder the recombination of photo-generated electron carriers and holes.

Association of leisure sedentary time with common chronic disease risk factors: A longitudinal study of China Health and Nutrition Surveys.

BACKGROUND: Although the common risk factors were identified and controlled for many years, the overall prevalence of chronic diseases continued to increase in China. OBJECTIVE: We presumed the leisure sedentariness as a latent but pivotal factor of chronic diseases, and examined its distribution and changing trend, analysed its interaction effects on common risk factors, which could provide a new perspective for the prevention and management. METHODS: A total of 5013 participants were screened out from China Health and Nutrition Survey. Random-effects ordered logistic models were used for ordinal dependent variables, and fixed-effects or random-effects logit models were used for binary dependent variables. RESULTS: From 2004 to 2011, the prevalence of high leisure sedentary time (LSED) increased by 58.58%. Members of the high LSED group were likely to choose fast food, salty snacks, soft drinks and more likely to smoke or drink alcohol compared with those of the low LSED group. However, they preferred walking, sports and body building more than those of the low LSED group. CONCLUSIONS: For the unhealthy dietary, tobacco and alcohol consumption, more targeted introduction and guidance related to sedentary time should be promoted. Meanwhile, the appeal for physical exercise as well as adequate facilities should be initiated.

Fabrication, characterization and in vitro evaluation of triboelectric nanogenerator based on 317 L stainless steel and polylactic acid.

A novel, cost-effective biomedical triboelectric nanogenerator (TENG) has been fabricated based on biocompatible medical 317 L stainless steel (317 L SS) and polylactic acid (PLLA) films as the friction layers, whose surface roughness was designed by simple and low-cost laser etching and hot-embossing template methods, respectively. With the increase of the TENG's tribo-interface roughness and the molecular weight of the PLLA, the power output of TENG was greatly increased owing to more charges being produced and the excellent mechanical properties PLLA possessed. When the 317 L SS plate surface roughness was 66.54% measured by the image J software and the PLLA film with a larger molecular weight at 500 000 was patterned with the 1000 mesh screen template, the maximal short current, open voltage and transferred charge of TENG reached up to 60 µA, 150 V and ∼125 nC, respectively. At the optimum condition, the maximum instantaneous power of the TENG was 5.5 mW at a load resistance of ∼2.5 MΩ and the saturation voltage was 20 V when the load capacitance was 0.1 µF. The evaluation of the TENG's biocompatibility in vitro was performed by using the simulated body fluid (SBF) solution and ultrasonic wave to mimic the body environment with various vibrations, respectively. After 6 h ultrasonic bath for the directly immersed TENG, the pH of the SBF solution just changed slightly from 7.4 to 7.61 with an acceptable degradation of the output power of TENG. The cellular toxicity test also demonstrates that the mouse L929 cells grow excellently with normal morphology even after 5 d. These results indicate that the TENG has a good stability in the body environment and the output performance can still drive many micro-medical devices.

The Degradation Properties of MgO Whiskers/PLLA Composite In Vitro.

In this study, composite films of stearic acid⁻modified magnesium oxide whiskers (Sa⁻w-MgO)/poly-l-lactic acid (PLLA) were prepared through solution casting, and the in vitro degradation properties and cytocompatibility of the composites with different whisker contents were investigated. The results showed that the degradation behavior of the composite samples depended significantly on the whisker content, and the degradation rate increased with the addition of MgO content. Furthermore, the degradation of the composites with higher contents of whiskers was influenced more severely by the hydrophilicity and pH value, leading to more final weight loss, but the decomposition rate decreased gradually. Furthermore, the pH value of the phosphate buffer solution (PBS) was obviously regulated by the dissolution of MgO whiskers through neutralization of the acidic product of PLLA degradation. The cytocompatibility of the composites also increased remarkably, as determined from the cell viability results, and was higher than that of PLLA at the chosen whisker content. This was beneficial for the cell affinity of the material, as it notably led to an enhanced biocompatibility of the PLLA, in favor of promoting cell proliferation, which significantly improved its bioactivity, as well.

The effect of anodized Ti on output performance of biomedical compatible triboelectric nanogenerators used for controlling the degradation of Mg-3wt%Zn-0.8wt%Zr.

Triboelectric nanogenerators (TENGs) can convert amorphous mechanical energy into electrical energy and solve the issue of source power for biological electronics implanted in the human body. Biomedical metal Ti was selected as the bottom plate, to fabricate a TENG with a poly-L-lactic-acid (PLLA) Ti structure. The Ti sheets were treated with a two-step anodization method, and the growth of titanium dioxide nanotube arrays (TNTAs) was controlled by variation in anodic oxidation time. The results showed that the output voltage and current of the PLLA-TNTAs biocompatible triboelectric nanogenerator (BCTENG), prepared by the two-step anodization method under 60 V for 6 h, can reach 220.6 V and 15.1 µA, respectively. The output voltage and current increased by 96.3% and 91.1%, respectively, compared with TENGs prepared without using the anode oxidation method. The choice of materials and modification of the surface morphology of the TENG components was found to be critical for increasing the triboelectrically generated surface charge. The output of the BCTENG can regulate degradation of magnesium alloys freely by using cathodic protection.

[Mutation analysis and prenatal diagnosis in families of X-linked agammaglobulinemia caused by BTK gene mutation].

OBJECTIVE: To evaluate the genetic diagnostic feasibility of Bruton's tyrosine kinase (BTK) gene in three families with X-linked agammagobulinemia (XLA) birth history, mutation analysis and prenatal genetic diagnosis of BTK gene for two families with XLA. METHODS: Polymerase chain reaction (PCR) was applied to amplify the regions of exon and exon-intron boundaries of BTK gene in 3 unrelated patients of XLA and their mothers from January 2011 to June 2012. The PCR products were further analyzed by direct sequencing. Prenatal genetic diagnosis was performed by chorionic villus sampling after genotyping of mothers of probands. RESULTS: Three novel mutations of BTK gene were identified in 3 pedigrees of XLA. A missense mutation c.1117C > A (p.L373I) were detected in pedigree 1. The mutation was possible damage by predicting in sillico. A nonsense mutation c.126T > G (p.Y42X) was found in pedigree 2. A single base deletion mutation c.1679delC (p. P560fsX10) was found in pedigree 3. The three mutations, p.L373I, p.Y42X and p. P560fsX10 were novel. The three novel mutations were absent in the 100 normal controls. The male fetus in pedigree 3 was free of mutations identical to the proband and the female fetus in pedigree 2 was a carrier. The two families continued the pregnancies and the infants showed no symptom of XLA after one year old. CONCLUSIONS: Three novel mutations were identified. The mutations of p.Y42X and p. P560fsX10 in BTK gene may be the major causes of pedigrees 2 and 3 with XLA. The mutation p.L373I of BTK gene is possibly the cause of pedigree 1 with XLA, but functional verification is needed. For pedigree of XLA, direct sequencing of BTK gene is available for providing genetic counseling, prenatal diagnosis.

Chaenomeles sinensis (Thouin) Koehne fruit polyphenols alleviate high-fat diet-induced obesity and liver steatosis by improving lipid metabolism in mice.

Chaenomeles sinensis (Thouin) Koehne fruit is a rich source of medicinally and nutritionally important natural phytochemicals that benefit human health. Based on the information provided, we hypothesized that Chaenomeles sinensis (Thouin) Koehne fruit polyphenols (CSFP) possessed in vivo protective effect of on high-fat diet (HFD)-induced obesity and hepatic steatosis. Specific pathogen-free male C57BL/6J mice were randomly divided into 3 groups and fed with a low-fat diet, HFD, or HFD supplemented with CSFP by intragastric administration for 14 weeks. Obesity-related biochemical indexes and hepatic gene expression profile were determined. The findings of this study demonstrated notable reductions in body weight gain, serum triglycerides, total cholesterol, low-density lipoprotein cholesterol, and steatosis grade in the group supplemented with CSFP compared with the HFD group. Gene expression analysis provided insights into the molecular mechanisms, demonstrating that CSFP downregulated the expression of key genes involved in lipogenesis (e.g., Fas, Fads2, Scd1) and upregulated the genes associated with fatty acid oxidation (e.g., Pparα, Cpt1a, Acox1), while also suppressing genes implicated in cholesterol homeostasis (e.g., HMGCoR, Insig1, AdipoR2). These molecular changes suggest that CSFP exerts protective effects by modulating hepatic lipid metabolism pathways, thereby mitigating the metabolic derangements associated with HFD-induced obesity and hepatic steatosis.

Effects of MgO nanoparticle addition on the mechanical properties, degradation properties, antibacterial properties and in vitro and in vivo biological properties of 3D-printed Zn scaffolds.

Bone tissue engineering is the main method for repairing large segment bone defects. In this study, a layer of bioactive MgO nanoparticles was wrapped on the surface of spherical Zn powders, which allowed the MgO nanoparticles to be incorporated into 3D-printed Zn matrix and improved the biodegradation and biocompatibility of the Zn matrix. The results showed that porous pure Zn scaffolds and Zn/MgO scaffolds with skeletal-gyroid (G) model structure were successfully prepared by selective laser melting (SLM). The average porosity of two porous scaffolds was 59.3 and 60.0%, respectively. The pores were uniformly distributed with an average pore size of 558.6-569.3 µm. MgO nanoparticles regulated the corrosion rate of scaffolds, resulting in a more uniform corrosion degradation behavior of the Zn/MgO scaffolds in simulated body fluid solution. The degradation ratio of Zn/MgO composite scaffolds in vivo was increased compared to pure Zn scaffolds, reaching 15.6% at 12 weeks. The yield strength (10.8 ± 2.4 MPa) of the Zn/MgO composite scaffold was comparable to that of cancellous bone, and the antimicrobial rate were higher than 99%. The Zn/MgO composite scaffolds could better guide bone tissue regeneration in rat cranial bone repair experiments (completely filling the scaffolds at 12 weeks). Therefore, porous Zn/MgO scaffolds with G-model structure prepared with SLM are a promising biodegradable bone tissue engineering scaffold.

The mediating effect of depression on new-onset stroke in diabetic population: Evidence from the China health and retirement longitudinal study.

BACKGROUND: Diabetes has a high incidence in China, which may cause stroke and depression. However, the relationship between diabetes and the incidence of new-onset stroke and depression has not been fully studied. METHODS: The data from the China Longitudinal Study on Health and Retirement (CHARLS) from 2013 to 2018 were used. A total of 8530 respondents aged ≥45 years old were included in the follow-up study. Logistic regression model, Cox regression, and Mediation analyses were used to explore the association between diabetes, depression, and new-onset stroke. RESULTS: The depression score of patients with diabetes history was higher (HR,95%CI = 1.02, 1.01-1.04) and were more likely to experience new-onset stroke events (HR, 95%CI = 1.046, 1.02-1.07). With a history of hypertension (HR,95%CI = 1.747, 1.381-2.208), older (HR,95%CI = 1.033, 1.020-1.046) with high BMI (HR,95%CI = 1.056, 1.027-1.086) have a high risk of new-onset stroke. In the combined subgroup analysis, the incidence of new-onset stroke in the subgroup with diabetes depression was higher than in others. The mediating effect of depression on new-onset stroke events in diabetic patients is more pronounced in the medium to long term (>3 years) after adjusting covariates. LIMITATIONS: We defined new-onset stroke by patient self-report, there might be some memory bias. In addition, new-onset stroke was not classified in the CHARLS questionnaire, which would hinder us to evaluate the mediating effect of depression on different types of new-onset stroke. CONCLUSION: Our results showed that depression has a partial mediating effect between diabetes and new-onset stroke in the middle-aged and elderly population in China.

Effects and differences of sleep duration on the risk of new-onset chronic disease conditions in middle-aged and elderly populations.

BACKGROUND: Few longitude cohort studies investigated the risk of the duration of nighttime sleep and naps to the new-onset common chronic disease conditions (CDCs) in middle-aged (45-60) and the elderly (age ≥ 60) populations using an age-stratified strategy. METHODS: The 7025 participants from The China Health and Retirement Longitudinal Study were screened as eligible subjects. Established 13 cohorts with CDCs, acquired their' sleep records in 2011, and obtained new-onset incidents of CDCs during follow-up in 2011-2018. Performed risk association analyses between sleep duration and 13 new-onset CDCs respectively. RESULTS: New-onset risk of four CDCs decreased with increasing nighttime sleep (p-nonlinear>0.05). The risk threshold was approximately 7 hours in middle-aged people and 6 hours in the elderly. For the middle-aged population, compared with 7-9hours sleep, <5hour and 5-7hours nighttime sleep were associated with 1.312∼1.675 times more risk of hypertension, kidney disease, diabetes or high blood sugar status, and multimorbidity; Compared with no nap, a 0-30 min nap was associated with 1.413(1.087∼1.837) times the heart disease risk. In the elderly, < 5 hours of night sleep was a significant risk factor for four CDCs including kidney disease and multimorbidity, etc. A long night's sleep (>9 hours) was connected with 61.2% reduction in risk of memory disease, a >90 min nap increased 62% risk of memory disease, and a 0-30 min nap was associated with higher risks of heart disease, hypertension, and a lower kidney disease risk. CONCLUSIONS: Nighttime sleep and daytime naps may have their own implications for the new-onset CDCs' risk in the aging process.

Inhibition of mammalian target of rapamycin complex 1 in the brain microvascular endothelium ameliorates diabetic Aß brain deposition and cognitive impairment via the sterol-regulatory element-binding protein 1/lipoprotein receptor-associated protein 1 signaling pathway.

AIMS: Mammalian target of rapamycin complex 1 (mTORC1) is highly activated in diabetes, and the decrease of low-density lipoprotein receptor-associated protein 1 (LRP1) in brain microvascular endothelial cells (BMECs) is a key factor leading to amyloid-ß (Aß) deposition in the brain and diabetic cognitive impairment, but the relationship between them is still unknown. METHODS: In vitro, BMECs were cultured with high glucose, and the activation of mTORC1 and sterol-regulatory element-binding protein 1 (SREBP1) was observed. mTORC1 was inhibited by rapamycin and small interfering RNA (siRNA) in BMECs. Betulin and siRNA inhibited SREBP1, observed the mechanism of mTORC1-mediated effects on Aß efflux in BMECs through LRP1 under high-glucose conditions. Constructed cerebrovascular endothelial cell-specific Raptor-knockout (Raptorfl/+ ) mice to investigate the role of mTORC1 in regulating LRP1-mediated Aß efflux and diabetic cognitive impairment at the tissue level. RESULTS: mTORC1 activation was observed in HBMECs cultured in high glucose, and this change was confirmed in diabetic mice. Inhibiting mTORC1 corrected the reduction in Aß efflux under high-glucose stimulation. In addition, high glucose activated the expression of SREBP1, and inhibiting of mTORC1 reduced the activation and expression of SREBP1. After inhibiting the activity of SREBP1, the presentation of LRP1 was improved, and the decrease of Aß efflux mediated by high glucose was corrected. Raptorfl/+ diabetic mice had significantly inhibited activation of mTORC1 and SREBP1, increased LRP1 expression, increased Aß efflux, and improved cognitive impairment. CONCLUSION: Inhibiting mTORC1 in the brain microvascular endothelium ameliorates diabetic Aß brain deposition and cognitive impairment via the SREBP1/LRP1 signaling pathway, suggesting that mTORC1 may be a potential target for the treatment of diabetic cognitive impairment.

The Fabrication, Properties, and Application of a Printed Green Ag NWs-Based Flexible Electrode and Circuit.

A suitable conductive ink for office inkjet printers is important for the convenient design of flexible electrodes for triboelectric nanogenerators (TENG). Ag nanowires (Ag NWs) easily printed with an average short length of 1.65 µm were synthesized by using soluble NaCl as a growth regulator and adjusting the amount of chloride ion. The water-based Ag NWs ink with a low solid content of 1% but with low resistivity was produced. The printed flexible Ag NWs-based electrodes/circuits showed excellent conductivity with RS/R0 values kept at 1.03 after bending 50,000 times on PI substrate and an excellent anticlimate property in acidic conditions for 180 h on polyester woven fabric. The sheet resistance was reduced to 4.98 Ω/sqr heated at 30-50 °C for 3 min by a blower due to the formed excellent conductive network when compared to Ag NPs-based electrodes. Finally, the integration of printed Ag NWs electrode and circuits was applied to the TENG, which can be used to predict a robot's out-of-balance direction by the change of the TENG signal. In all, a suitable conductive ink with a short length of Ag NWs was fabricated, and flexible electrodes/circuits can be conveniently and easily printed by office inkjet printers.

Development of a predictive risk stratification tool to identify the population over age 45 at risk for new-onset stroke within 7 years.

Background and purpose: With the acceleration of the aging process of society, stroke has become a major health problem in the middle-aged and elderly population. A number of new stroke risk factors have been recently found. It is necessary to develop a predictive risk stratification tool using multidimensional risk factors to identify people at high risk for stroke. Methods: The study included 5,844 people (age ≥ 45 years) who participated in the China Health and Retirement Longitudinal Study in 2011 and its follow-up up to 2018. The population samples were divided into training set and validation set according to 1:1. A LASSO Cox screening was performed to identify the predictors of new-onset stroke. A nomogram was developed, and the population was stratified according to the score calculated through the X-tile program. Internal and external verifications of the nomogram were performed by ROC and calibration curves, and the Kaplan-Meier method was applied to identify the performance of the risk stratification system. Results: The LASSO Cox regression screened out 13 candidate predictors from 50 risk factors. Finally, nine predictors, including low physical performance and the triglyceride-glucose index, were included in the nomogram. The nomogram's overall performance was good in both internal and external validations (AUCs at 3-, 5-, and 7-year periods were 0.71, 0.71, and 0.71 in the training set and 0.67, 0.65, and 0.66 in the validation set, respectively). The nomogram was proven to excellently discriminate between the low-, moderate-, and high-risk groups, with a prevalence of 7-year new-onset stroke of 3.36, 8.32, and 20.13%, respectively (P < 0.001). Conclusion: This research developed a clinical predictive risk stratification tool that can effectively identify the different risks of new-onset stroke in 7 years in the middle-aged and elderly Chinese population.

The in vivo and in vitro corrosion behavior of MgO/Mg-Zn-Ca composite with different Zn/Ca ratio.

The effect of Zn/Ca ratio on the corrosion behavior of Mg-3Zn-0.2Ca-1.0MgO (3ZX) and Mg-1Zn-0.2Ca-1.0MgO (ZX) was investigated on the as-extruded specimens. Microstructure observations revealed that the low Zn/Ca ratio led to the grain growth from 1.6 µm in 3ZX to 8.1 µm in ZX. At the same time, the low Zn/Ca ratio changed the nature of second phase from the existence of Mg-Zn and Ca2Mg6Zn3 phases in 3ZX to the dominated Ca2Mg6Zn3 phase in ZX. The local galvanic corrosion caused by the excessive potential difference was alleviated obviously due to the missing of MgZn phase in ZX. Besides, the in vivo experiment also showed that ZX composite exhibited a good corrosion performance and the bone tissue around the implant grew well.

Mechanical properties, degradation behavior and cytocompatibility of biodegradable 3vol%X (X = MgO, ZnO and CuO)/Zn matrix composites with excellent dispersion property fabricated by graphene oxide-assisted hetero-aggregation.

Metal matrix composites have been recognized as a feasible approach to obtain a new generation of biodegradable Zn-based material. Nevertheless, there is a great challenge in achieving good dispersion properties of the bioactive reinforcements within zinc matrix. A novel and facile approach, namely graphene oxide (GO)-assisted hetero-aggregation, were developed to achieve uniformly dispersed nanoceramics in the Zn matrix, by using very low-content (0.03 vol%) GO as a linker between the Zn matrix and reinforcement. The negatively-charged GO becomes a suitable "bridge" connected the positively-charged metallic powder and bioactive reinforcement by charge neutralization in polarity solvent. Three kinds of reinforcements, including MgO, ZnO and CuO, were used to verify the feasibility of the above-mentioned method. As-sintered 3CuO/Zn matrix composites, which possessed uniformly distributed reinforcement, uniaxial compressive strength of 301.2 MPa, failure strain over 40%, moderate corrosion rate of 0.063 mm·y-1, acceptable cytocompatibility and antibacterial property, should be a useful material for orthopedic applications.

Association of the depressive scores, depressive symptoms, and conversion patterns of depressive symptoms with the risk of new-onset chronic diseases and multimorbidity in the middle-aged and elderly Chinese population.

Background: The relationship between depressive symptoms (DS) and their conversion patterns over time and the new-onset risk of diseases in the middle-aged and elderly population has not been extensively studied. Methods: Based on The China Health and Retirement Longitudinal Study participants in 2013, we established 13 cohorts involving 12 types of chronic diseases and multimorbidity, who were identified by face-to-face questionnaires. We retrospectively assessed their DS during 2011 and 2013 through the 10-item Center for Epidemiological Studies Depression Scale (CES-D), which were classified into never, newly developed, relieved, and persistent DS, and these participants were followed from 2013 to 2018. Findings: CES-D scores were new-onset risk factors for 9 diseases. The new-onset risk of diseases increased with higher CES-D scores. When CES-D scores were higher than approximately 6, the hazard ratios (HRs) of emergent diseases were greater than 1. DS was independent new-onset risk factors for 8 diseases, with HRs (95% CI) ranging from 1.2635 (1.0061-1.5867) to 1.5231 (1.0717-2.165). Persistent DS was an independent risk factor for most diseases but might be an independent protective factor for new-onset cancer (HR, 95% CI: 0.276, 0.106-0.723). Interpretation: DS is closely associated with new-onset risk of chronic diseases and multimorbidity, and awareness of the risk associated with pre-DS status (6

In vivo urinary compatibility of Mg-Sr-Ag alloy in swine model.

A biodegradable metallic ureteral stent with suitable mechanical properties and antibacterial activity remains a challenge. Here we reveal the scientific significance of a biodegradable Mg-Sr-Ag alloy with a favorable combination of balanced mechanical properties, adjustable indwelling time in urinary tract and evident antibacterial activity via in vivo experiments in a swine model. Attributed to the rheo-solidification process, equiaxial microstructure and significantly refined grains (average grain size: 27.1 µm) were achieved. Mg17Sr2 and Mg4Ag were found as the primary precipitates in the matrix, due to which the alloy obtained ca. 111% increase in ultimate tensile strength in comparison to pure magnesium. Both the in vitro and in vivo results demonstrated the satisfactory biocompatibility of the alloy. Histological evaluation and bioindicators analysis suggested that there was no tissue damage, inflammation and lesions in the urinary system caused by the degradation process. The stent also improved the post-operative bladder functions viewed from the urodynamic results. Our findings highlight the potential of this alloy as antibacterial biodegradable urinary implant material.

Fabrication and characterization of biodegradable zinc matrix composites reinforced by uniformly dispersed beta-tricalcium phosphate via graphene oxide-assisted hetero-agglomeration.

The development of biodegradable Zn matrix composites has been considered a promising approach to achieving enhanced mechanical properties, controllable degradation rate, good biocompatibility, and good osseointegration as orthopedic implants. However, scant literature regarding Zn matrix composites has been reported because of the great difficulty in dispersing the nano-sized bioactive reinforcements uniformly within the Zn matrix. In the present study, a novel and effective method were employed to obtain Zn matrix composites reinforced by uniformly dispersed beta-tricalcium phosphate (ß-TCP) via graphene oxide (GO)-assisted hetero-agglomeration and subsequent spark plasma sintering process. A very low-content (0.04 vol%) few-layered GO was used as a coupling reagent to connect the Zn matrix and nano-sized TCP particles. In an appropriate polarity solvent, the negatively charged GO sheets could combine with both the positively charged Zn powder and TCP particles by electrostatic attraction and charge neutralization. Due to the nature of hetero-agglomeration, the flexible GO sheet could adhere to the large Zn powder and attracted a certain amount of TCP particles to form a Zn/GO/TCP sandwich structure by charge neutralization thereby forming a uniform dispersion of TCP particles within Zn matrix. After the spark plasma sintering (SPS) process, the TCP particles incorporated with very thin ZnO layers (thickness of a few dozen nanometers) formed a homogeneous and unique 3D network-like distribution in as-sintered TCP/Zn composites. A unique "snap pea"-like structure was confirmed at the grain boundary of α-Zn grains, which consisted of the TCP particles as "pea" and thin ZnO layer as "pod". Due to the uniform dispersion of bioactive TCP particles and unique structure of the TCP incorporating grain boundary, as-sintered 3TCP/Zn matrix composites possessed yield strength (YS) of 140.8 ± 7.7 MPa, failure strain of 36.0 ± 2.8%, the moderate degradation rate of 19.1 ± 3.3 µm·y-1 and good cytocompatibility to MC3T3-E1 cells. Moreover, osteogenic differentiation activity evaluation revealed that the addition of TCP could significantly improve the expressions of the osteogenic differentiation-related gene (ALP) in MC3T3-E1 cells, thereby resulting in improved osteogenic capability. Therefore, biodegradable 3TCP/Zn matrix composites fabricated by GO-assisted hetero-agglomeration and subsequent SPS process could be a promising material as orthopedic implants.

In vitro corrosion resistance and cytocompatibility of nano-hydroxyapatite reinforced Mg-Zn-Zr composites.

Due to good biocompatibility and mechanical properties, magnesium (Mg) and its alloys are considered promising degradable materials for orthopedic applications. In this work, a Mg metal matrix composite (MMC) was fabricated using Mg-2.9Zn-0.7Zr alloy as the matrix and 1 wt% nano-hydroxyapatite (n-HA) particles as reinforcements. In vitro corrosion behavior and cytocompatibility of a Mg-Zn-Zr/n-HA composite and a Mg-Zn-Zr alloy were investigated. In contrast with the Mg-Zn-Zr alloy, the MMC has better properties. The average corrosion rate of MMC is 0.75 mm/yr after immersion in simulated body fluid (SBF) for 20 days, and the surface of MMC is covered with white Ca-P precipitates. The electrochemical test results show that the corrosion potential (E(corr)) of MMC increases to -1.615 V and its polarization resistance (R(p)) is 2.56 KOmega with the addition of n-HA particles. The co-cultivation of MMC with osteoblasts results in the adhesion and proliferation of cells on the surface of the composite. The maximum cell density is calculated to be (1.85+/-0.15) x 10(4)/l after 5 days of co-culture with osteoblasts. The average cell numbers for two groups after culturing for 3 and 5 days (P<0.05) are significantly different. All the results demonstrate that the Mg-Zn-Zr/n-HA composite can be potentially used as biodegradable bone fixation material.

Non-aqueous liquid crystals of hydroxyapatite nanorods.

Hydroxyapatite (HA) nanorods in the collagen matrix of bone have a macroscopically ordered structure that has many similarities to the ordered structure of anisotropic nano-units in inorganic liquid crystals (LCs). Inspired by these similarities, we conducted the first (to our best knowledge) synthesis of HA LCs in non-polar solvents (such as cyclohexane and toluene), thus expanding the range of applicable monomers and polymers. We synthesized HA nanorods by a simple, effective, and oleic-acid-assisted hydrothermal route. The hydrothermal temperature directly modulates the aspect ratio of the HA nanorods, and indirectly modulates their LC behavior. The LC phase transition has no size limitation. Thus, our approach may be used to develop high solid content, macroscopically assembled, large-scale polymer-based bio(mimetic)-materials.