Corrosion Behavior and Biocompatibility of Na2EDTA-Induced Nacre Coatings on AZ91D Alloys Prepared via Hydrothermal Treatment.

An effective method for controlling the corrosion rate of Mg-based implants must be urgently developed to meet the requirements of clinical applications. As a naturally occurring osteoid material, nacre offers a strategy to endow biomedical Mg alloys with excellent biocompatibility, and corrosion resistance. In this study, pearl powder and NaH2PO4 were used as precursors to deposit coatings on AZ91D alloy substrates hydrothermally based on Na2EDTA-assisted induction. Na2EDTA-induced nacre coatings were fabricated at various pH values, and its chemical composition and microstructure were analyzed via energy-dispersive X-ray, scanning electron microscopy, and X-ray diffraction spectroscopy. The corrosion-resistant performance and cytocompatibility of the samples were evaluated via electrochemical measurements and in vitro cell experiments. Results showed that the samples hydrothermally treated under faint acid conditions present excellent corrosion resistance, whereas the samples treated under slight alkaline conditions demonstrate improved biocompatibility due to high Ca and P content and large Ca/P atomic ratio. This study provides substantial evidence of the potential value of nacre coatings in expanding the biological applications of implanted biomaterials.

Application of Electrochemical Atomic Force Microscopy (EC-AFM) in the Corrosion Study of Metallic Materials.

Electrochemical atomic force microscopy (EC-AFM), a branch of a scanning probe microscopy (SPM), can image substrate topography with high resolution. Since its inception, it was extended to a wide range of research areas through continuous improvement. The presence of an electrolytic cell and a potentiostat makes it possible to observe the topographical changes of the sample surface in real time. EC-AFM is used in in situ corrosion research because the samples are not required to be electrically conductive. It is widely used in passive film properties, surface dissolution, early-stage corrosion initiation, inhibitor efficiency, and many other branches of corrosion science. This review provides the research progress of EC-AFM and summarizes the extensive applications and investigations using EC-AFM in corrosion science.

Effects of blending sequences and molecular structures of the compatibilizers on the morphology and properties of PLLA/ABS blends.

The effects of molecular structures of the compatibilizers and blending sequences on the morphology and properties of the immiscible poly(l-lactide)/acrylonitrile-butadiene-styrene (PLLA/ABS) blend are investigated herein. The comb-like polymers (RC), which are constituted by a poly(methyl methacrylate) (PMMA) backbone and side chains and a few epoxy groups distributed randomly along the backbone, are found to be better compatibilizers for improving the morphology and mechanical properties of the PLLA/ABS blend, compared to linear polymers (RL) constituted by a PMMA backbone and epoxy groups along the backbone. In addition, the blending sequence, which dictates the extent of grafting reaction between carboxyl end groups of PLLA and epoxy groups in the RL and RC compatibilizers, is found to influence the diffusion and location of the in situ formed RL-g-PLLA and RC-g-PLLA polymers in the blend system. By blending RL or RC polymers with ABS phase firstly, the epoxy groups are diluted by ABS phase; thus, during the second step, blending with PLLA phase, lightly grafted polymers are formed. This method is found to be the best sequence to compatibilize the PLLA/ABS system. When the PLLA phase is mixed with the compatibilizers firstly, the highly grafted polymers are prone to be trapped in the PLLA phase, because the PMMA segments are shielded by the densely grafted PLLA segments from interacting efficiently with the ABS phase, and thus the morphology and mechanical properties of the blend deteriorate accordingly.

Diagnostic value of near-infrared or fluorescent indocyanine green guided sentinel lymph node mapping in gastric cancer: A systematic review and meta-analysis.

BACKGROUND: This meta-analysis was conducted to evaluate the diagnostic value of near-infrared (NIR) or fluorescent indocyanine green (ICG) guided sentinel lymph node (SLN) mapping in gastric cancer (GC). METHODS: This meta-analysis was registered at the PROSPERO. Clinical studies were retrieved from the electronic database Pubmed, Embase, Medline, Web of science, and the Cochrane Library. Quality assessment was conducted by an adapted checklist of QUADAS-2. A bivariate mixed-effects model was used to pool the data. Evaluation of articles quality, analysis for publication bias, summary receiver operator characteristic (SROC) curves, and meta-regression were also performed. Subgroup analysis was used to explain the heterogeneities. RESULTS: A total of 13 clinical studies (971 patients) were included. The NIR or fluorescent imaging (FI) involved infrared ray electronic endoscopy (IREE), infrared ray laparoscopic system (IRLS), and FI system. Significant evidence of heterogeneity was found for sensitivity and specificity (I 2 = 91.1% and I 2 = 98.2%), respectively. The pooled SLN sensitivity (Sen), specificity (Spe), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were 0.94(95%CI: 0.80-0.99), 1.00(95%CI: 0.60-1.00), 34.0(95%CI: 9.25-125.29), 0.06(95%CI:0.02-0.22), and 252.50(95%CI: 94.93-671.61), respectively. Area under curve (AUC) of SROC curve was 1.00 (95%CI: 0.99-1.00), and the summary operating point (cut-off value) was SENS = 0.94(95%CI: 0.80-0.99) and SPEC = 1.00(95%CI: 0.60-1.00). Subgroup analysis showed that NIR imaging, imaging performed 20 minutes after intraoperative injection, preoperative injection (especially for FI imaging), stained with immunohistochemistry (IHC) (+hematoxylin-eosin [HE]), cT1 stage, submucosa injection (especially for cT1), mean number of SLN ≥ 5, study size > 26 were associated with higher SLN sensitivity. In terms of ICG concentration, diluted ICG concentration that 0.5 mg/mL (compared with 5 mg/mL) in NIR imaging and 0.05 mg/mL (compared with 0.5 mg/mL) in FI system showed higher sensitivities. However, the differences in tumor diameter (≤30 mm vs >30 mm), gastrectomy methods (opening vs laparoscopy), lymphadenectomy methods (LBD vs pick-up), and publication year (≥2010 vs <2010) did not achieve statistical significance. CONCLUSION: ICG combined with NIR or FI guided SLN mapping is technically feasible for GC. Based on the small sample size evidence, the IREE and IRLS devices may have higher sensitivity than FI in current clinical studies; and there may be an excessive ICG concentration used for current SLN mapping in GC. However, well-designed further studies with large sample size are needed to confirm the best procedure and suitable criteria. MINI-ABSTRACT: This meta-analysis was registered at PROSPERO. Clinical studies on this topic were retrieved from the electronic database Pubmed, Embase, Medline, Web of Science, and the Cochrane Library. The NIR or FI involved IREE, IRLS, and FI techniques. A total of 13 clinical studies (971 patients) were included. Based on the small sample size evidence, NIR or FI ICG guided SLN mapping in GC is technically feasible.

Nanosized sustained-release drug depots fabricated using modified tri-axial electrospinning.

Nanoscale drug depots, comprising a drug reservoir surrounded by a carrier membrane, are much sought after in contemporary pharmaceutical research. Using cellulose acetate (CA) as a filament-forming polymeric matrix and ferulic acid (FA) as a model drug, nanoscale drug depots in the form of core-shell fibers were designed and fabricated using a modified tri-axial electrospinning process. This employed a solvent mixture as the outer working fluid, as a result of which a robust and continuous preparation process could be achieved. The fiber-based depots had a linear morphology, smooth surfaces, and an average diameter of 0.62±0.07µm. Electron microscopy data showed them to have clear core-shell structures, with the FA encapsulated inside a CA shell. X-ray diffraction and IR spectroscopy results verified that FA was present in the crystalline physical form. In vitro dissolution tests revealed that the fibers were able to provide close to zero-order release over 36h, with no initial burst release and minimal tailing-off. The release properties of the depot systems were much improved over monolithic CA/FA fibers, which exhibited a significant burst release and also considerable tailing-off at the end of the release experiment. Here we thus demonstrate the concept of using modified tri-axial electrospinning to design and develop new types of heterogeneous nanoscale biomaterials. STATEMENT OF SIGNIFICANCE: Nanoscale drug depots with a drug reservoir surrounded by a carrier are highly attractive in biomedicine. A cellulose acetate based drug depot was investigated in detail, starting with the design of the nanostructure, and moving through its fabrication using a modified tri-axial electrospinning process and a series of characterizations. The core-shell fiber-based drug depots can provide a more sustained release profile with no initial burst effect and less tailing-off than equivalent monolithic drug-loaded fibers. The drug release mechanisms are also distinct in the two systems. This proof-of-concept work can be further expanded to conceive a series of new structural biomaterials with improved or new functional performance.

Effects of different concentrations of tetramethylpyrazine, an active constituent of Chinese herb, on human corneal epithelial cell damaged by hydrogen peroxide.

AIM: To discuss the effects of different concentrations of tetramethylpyrazine (TMP), an active constituent of Chinese herb, on damaged Shandong human corneal epithelial cell (SDHCEC) induced by hydrogen peroxide. METHODS: We detected the combined effects of TMP with concentrations ranging from 4 mg/mL to 0.03 mg/mL and 800 µM hydrogen peroxide on SDHCEC. The methyl thiazolyl tetrazolium (MTT) assay was processed at 3, 6 and 12h separately while the detection of cell apoptosis at 6h only by flow cytometry. RESULTS: The viability of SDHCEC with 0.5 mg/mL, 0.25 mg/mL, 0.125 mg/mL and 0.06 mg/mL TMP joint with 800 µM hydrogen peroxide at 3h and 6h was significantly higher than that with 800 µM hydrogen peroxide only, P<0.05. However, except 0.25 mg/mL, TMP with other concentrations joint with 800 µM hydrogen peroxide at 12h could not significantly inhibit decreased SDHCEC viability induced by 800 µM hydrogen peroxide. At 12h, TMP of 0.5 mg/mL, 0.25 mg/mL, 0.125 mg/mL and 0.06 mg/mL could significantly inhibit SDHCEC early apoptosis induced by 800 µM hydrogen peroxide, most remarkable at 0.25 mg/mL TMP, P<0.05. CONCLUSION: Our results suggested that hydrogen peroxide can induce apoptosis related damage to SDHCEC. TMP can protect SDHCEC from the damage, and the protective effects may be associated with its anti-apoptosis mechanism.

Establishment of the mild, moderate and severe dry eye models using three methods in rabbits.

BACKGROUND: Dry eye (DE) is a common eye disease, and appropriate animal models are essential to explore the pathogenesis and therapy of DE. In this study, we aimed to establish rabbit models by three methods. METHODS: In group A, the lacrimal gland, Harderian gland, and nictitating membrane of the left eyes were surgically removed. In group B, the bulbar conjunctiva of the left eyes was burned with 50% trichloroacetic acid. In group C, both methods above were used. The right eyes served as normal controls. The Schirmer I test (SIt), fluorescein staining, and impression cytology were evaluated at baseline and on days 28, 42, and 56. RESULTS: Both the SIt and goblet cell density were significantly lower in operated eyes compared to the control eyes, while the corneal fluorescein staining scores in the operated eyes were significantly higher than in the control eyes on days 28, 42, and 56 (p < 0.05, p < 0.01 or p < 0.001). The SIt and goblet cell densities in groups B and C were significantly lower than group A on days 28, 42, and 56 (p < 0.05, p < 0.01 or p < 0.001). In addition, the corneal fluorescein staining scores in group C were significantly higher than either group A or group B on days 28, 42, and 56, while fluorescein staining scores were higher in group B than group A on days 42 and 56 days (p < 0.05, p < 0.01 or p < 0.001), with mean score 3.8 ± 1.30 (group A), 7.4 ± 1.14 (group B) and 10.8 ± 1.30 (group C) on day 56. CONCLUSIONS: Results suggest that three separate DE models, with mild, moderate, and severe manifestations of DE, could be stably established, in which conjunctival goblet cells took an important role.

Comparison of the Schirmer I test with and without topical anesthesia for diagnosing dry eye.

AIM: To determine the value of Schirmer I test (S I t) without anesthesia and with topical anesthesia for diagnosing dry eye (DE). METHODS: Totally 220 eyes in 110 patients, male (44) and female (66), (39.56±12.67) years old diagnosed with DE were examined. S I t without anesthesia was performed firstly, and 15 minutes later, it was applied again in the same person after topical anesthesia with 0.5% proparacaine hydrochloride eye drops. The wetting strips counted <10mm per 5 minutes were defined positive, while ≤5mm per 5 minutes were defined strong positive. RESULTS: The wetting length in S I t after topical anesthesia was significantly lower than that in S I t without anesthesia (P<0.001). The positive rate and strong positive rate of S I t after topical anesthesia were significantly higher than that of S I t without anesthesia (P<0.001). The positive rate and strong positive rate of S I t without anesthesia and the strong positive rate of S I t after topical anesthesia in patients with aqueous-deficiency dry eye (ADDE) were significantly higher than those in total patients whereas those in patients with evaporative dry eye (EDE) were significantly lower than those in total patients (P<0.001). CONCLUSION: S I t after topical anesthesia with 0.5% proparacaine hydrochloride eye drops is more objective and reliable than that without anesthesia in reflecting the status of DE, and its diagnostic value in patients with ADDE was even higher, making itself a meaningful evidence for the diagnosis and treatment of DE.

Effect of (-)-epigallocatechin gallate on electrochemical behavior and surface film composition of Co-Cr alloy used in dental restorations.

The aim of this study was to investigate the electrochemical behavior of Co-Cr alloy in artificial saliva containing (-)-epigallocatechin gallate (EGCG) and to characterize the composition and structure of the passive film formed by potentiodynamic polarization.Electrochemical measurements ranked the corrosion resistance of Co-Cr dental cast alloy as follows when exposed to artificial saliva containing different concentrations of EGCG: 4.0 g/L<2.0 g/L<0 g/L<0.5 g/L<1.0 g/L. This showed that the concentration of EGCG in artificial saliva affected the corrosion behavior of Co-Cr alloy. X-ray photoelectron spectroscopy (XPS) results revealed that the outermost surface layer on Co-Cr alloy was mainly composed of Cr2O3 and EGCG-Cr (III) ion complex, which were formed by redox and complex formation reactions respectively. When the redox reaction was dominant, Co-Cr alloy exhibited high corrosion resistance in EGCG-containing artificial saliva. On the contrary, when the complex formation reaction was dominant, Co-Cr alloy exhibited low corrosion resistance.

Protective effects and mechanism of tetramethylpyrazine against lens opacification induced by sodium selenite in rats.

Tetramethylpyrazine (TMP), extracted from the Chinese herbal medicine Ligusticum wallichii franchat (chuan xiong in Chinese), is a potent anti-free radical and calcium antagonist. Correspondingly, two important hypotheses in the causation of cataracts are free radical toxicity and calcium ion overload. In this study we investigated the effect of TMP on lens opacification induced by sodium selenite in rats, addressing the potential of TMP eye drops to prevent and treat cataracts. Results showed that the extent of lens opacification in the untreated Normal Control group (NC group) was significantly less than that of selenite-injected untreated rats (MC group) on days 3, 5, 7 and 10 (p < 0.001), while TMP treated selenite-injected rats (TMP group) had less lens opacification than the MC group on days 3, 5, 7 and 10 (p < 0.05). Compared with the NC group, the MC group had significantly decreased activity of super-oxide dismutase (SOD), glutathione peroxidase (GSH-PX) and catalase (CAT) and significantly elevated malondialdehyde (MDA) and calcium ion content (p < 0.001). Compared with the MC group, the activity of (SOD), (GSH-PX) and (CAT) were significantly higher while (MDA) and calcium ion levels were significantly lower in the TMP group at all time points (p < 0.01). The findings demonstrate that the selenite-induced cataract rat models were successfully built and the TMP eye drops can delay lens opacification induced by sodium selenite in rats. The mechanism by which TMP preserves lens transparency from selenite treated animals is associated with the lenses' ability to maintain normal levels of activity of SOD, GSH-PX and CAT and normal concentrations of MDA and calcium ion.

[Aqueous humor penetration of ligustrazine hydrochloride eye drops after topical administration in rabbit eyes].

PURPOSE: To study the aqueous humor penetration of ligustrazine hydrochloride after ocular administration in rabbits. METHODS: Eighteen rabbits were randomly divided into 6 groups. The aqueous humor was collected at 5, 15, 30, 60, 120 and 180 minutes following topical administration of ligustrazine hydrochloride eye drops and the concentration of ligustrazine hydrochloride was determined by HPLC. Analytical column was Diamonsil C18 stainless steel column (250 mm x 4.6 mm, 5 microm); The mobile phase was methanol: water(62:38); Flow rate was 0.9 ml/min; The detection wavelength was 280 nm. RESULTS: The concentrations of ligustrazine hydrochloride in aqueous humor were (15.785 +/- 2.988) microg/mL, (11.900 +/- 1.743) microg/mL, (8.286 +/- 1.182) microg/mL, (2.745 +/- 0.807) microg/mL, (0.379 +/- 0.091) microg/mL, (0.049 +/- 0.038) microg/mL, respectively, after a time interval of 5 min, 15 min, 30 min, 60 min, 120 min, 180 min. The maximum concentration was 15.785 microg/mL at 5 min, and then the concentration of ligustrazine hydrochloride gradually decreased and declined to a lower point at 180 min. CONCLUSION: The penetration of ligustrazine hydrochloride in aqueous humor after ocular administration was good. The results provided experimental data for the management of eye diseases with ligustrazine hydrochloride by topical administration.

[Cytotoxic effects of three kinds of eye drops for Chinese herbal medicines on various cell lines in vitro].

OBJECTIVE: To study the cytotoxic effects of three kinds of eye drops on human cancer cells and normal cells. METHODS: Cytotoxic effects of Yuxingcao Eye Drop (YXC), Gegensu Eye Drop (GGS) and Shuanghuanglian Eye Drop (SHL) on 6 cell lines (CNE2, Glc-82, HRPE, Fibro, 3T3 and ECV-304) were assayed using MTF method. And cytotoxic efficacy was evaluated using fifty percent of inhibitory concentration (IC50). RESULTS: IC50 of YXC to human cancer cells CNE2 and Glc-82 were (11.5 +/- 0.25) microl/ml and (24.0 +/- 0.8) microl/ml; to normal cells HRPE, Fibro, 3T3 and ECV-304 were (18.0 +/- 3.5) microl/ml, (52.0 +/- 14.0) microl/ml, (17.5 +/- 3.5) microl/ml and (17.5 +/- 1.3) microl/ml, respectively. IC50 of GGS to CNE2, Glc-82, ECV-304 cells were (9.8 +/- 2.3) microl/ml, (17.0 +/- 5.0) microl/ml and (10.5 +/- 0.95) microl/ml, respectively. Under the concentration of 100 microl/ml, the average survival rates of HRPE, Fibro and 3T3 cells were 60.0%, 87.8% and 58.2%, respectively. IC50 of SHL to CNE2, Glc-82 and HRPE cells were (18.9 +/- 5.0) microl/ ml, (23.9 +/- 0.6) micorl/ml and (113.9 +/- 25.6) microl/ml. At the concentration of 100 microl/ml, the average survival rates of Fibro, 3T3 and ECV-304 Cells were 89.6%, 77.2% and 74.7%. CONCLUSION: YXC has evident cytotoxicities to human cancer cells and normal cells. While, GGS and SHL has not obvious cytotoxic effects to normal cells.