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1.
Bioelectrochemistry ; 145: 108050, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-35074732

RESUMO

Quorum sensing (QS) is a process of bacterial communication that involves the use of biochemical signals and adjusts the expression of specific genes as a response to the bacterial cell density within an environment. This process is employed by both Gram-positive and Gram-negative bacteria to regulate different physiological functions. In both cases, QS involves production, detection and responses to signalling chemicals, termed auto-inducers. Expression of virulence factors and formation of biofilms are the typical processes controlled by QS, which, therefore, inspires the exploration of QS as a plausible solution to mitigating the increasing microbial resistance to antibiotics. QS inhibitors (QSIs) from different origins have been recognised as a promising solution to biofilm related challenges in a large variety of applications. Though QSIs have demonstrated some strength in tackling biofouling, a key focus in the literature on QSIs based strategies has been to control microbially influenced corrosion. This article reviews the principles of QS, its mechanistic roles in biofilm formation and the feasibility of QSIs to mitigate biofilm related challenges in a number of commercial applications. The potential of QSIs in microbially influenced corrosion for future applications is also discussed.

2.
Early Hum Dev ; 165: 105522, 2021 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-34959193

RESUMO

BACKGROUND: Cardiorespiratory instability occurs very often in very-low-birth-weight (VLBW) and extremely-low-birth-weight (ELBW) infants undergoing patent ductus arteriosus (PDA) ligation during the early postoperative period. This study aimed to investigate ultrasonic cardiac output monitor (USCOM) as a bedside tool by evaluating the hemodynamic changes in preterm infants following PDA ligation and assessing factors that may influence these changes. METHODS: This was a single-center prospective observational study at a third-level neonatal intensive care unit. A total of 33 infants, including 21 VLBW and 12 ELBW infants, were involved. Hemodynamic measurements were performed in these infants using a USCOM preoperatively as well as 0-1 h, 8-10 h, and 24 h postoperatively. RESULTS: The PDA ligation was associated with reductions of the left ventricular cardiac output (LVCO) (P < 0.001), cardiac index (P < 0.001), flow time corrected (FTC) (P < 0.001), Smith-Madigan inotropy index (SMII) (P < 0.001), oxygen delivery (DO2) (P < 0.001), and oxygen delivery index (DO2I) (P < 0.001) and an increase of the systemic vascular resistance index (SVRI) (P < 0.001) at 0-1 h, 8-10 h, and 24 h post-ligation compared with the respective preoperative values. Compared with the respective values at 0-1 h post-ligation, there was no significant difference in the CI, SMII, or FTC at 8-10 h and 24 h post-ligation. However, the SVRI decreased at 8-10 h and 24 h post-ligation. Moreover, the DO2I increased at 8-10 h and 24 h post-ligation, and the LVCO and DO2 increased at 24 h post-ligation. CONCLUSION: Our study confirmed that the hemodynamic changes measured by the USCOM were similar to those measured by echocardiography in previous reports. Thus, USCOM is a useful and convenient bedside tool for assessing hemodynamic changes to guide the use of fluids, inotropic agents, and vasopressors and help modify the post-ligation course, and they may be a surrogate for repeated echocardiography during the early post-ligation period in preterm infants or a preliminary screening method.

4.
Cancer Manag Res ; 13: 6911-6923, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34512030

RESUMO

Purpose: We aimed to construct of a nomogram to predict progression-free survival (PFS) in locoregionally advanced nasopharyngeal carcinoma (LA-NPC) with risk stratification using computed tomography (CT) radiomics features and clinical factors. Patients and Methods: A total of 311 patients diagnosed with LA-NPC (stage III-IVa) at our hospital between 2010 and 2014 were included. The region of interest (ROI) of the primary nasopharyngeal mass was manually outlined. Independent sample t-test and LASSO-logistic regression were used for selecting the most predictive radiomics features of PFS, and to generate a radiomics signature. A nomogram was built with clinical factors and radiomics features, and the risk stratification model was tested accordingly. Results: In total, 20 radiomics features most associated with prognosis were selected. The radiomics nomogram, which integrated the radiomics signature and significant clinical factors, showed excellent performance in predicting PFS, with C-index of 0.873 (95% CI: 0.803~0.943), which was better than that of the clinical nomogram (C-index, 0.729, 95% CI: 0.620~0.838) as well as of the TNM staging system (C-index, 0.689, 95% CI: 0.592-0.787) in validation cohort. The calibration curves and the decision curve analysis (DCA) plot obtained suggested satisfying accuracy and clinical utility of the model. The risk stratification tool was able to predict differences in prognosis of patients in different risk categories (p<0.001). Conclusion: CT-based radiomics features, an in particular, radiomics nomograms, have the potential to become an accurate and reliable tool for assisting with prognosis prediction of LA-NPC.

5.
Allergol Int ; 2021 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-34400075

RESUMO

BACKGROUND: The effects of bronchial thermoplasty (BT) on smooth muscle (SM) and nerves in small airways are unclear. METHODS: We recruited 15 patients with severe refractory asthma, who received BT treatment. Endobronchial optical-coherence tomography (EB-OCT) was performed at baseline, 3 weeks' follow-up and 2 years' follow-up to evaluate the effect of BT on airway structure. In addition, we divided 12 healthy beagles into a sham group and a BT group, the latter receiving BT on large airways (inner diameter >3 mm) of the lower lobe. The dogs' lung lobes were resected to evaluate histological and neuronal changes of the treated large airways and untreated small airways 12 weeks after BT. RESULTS: Patients receiving BT treatment had significant improvement in Asthma Control Questionnaire (ACQ) scores and significant reduction in asthma exacerbations. EB-OCT results demonstrated a notable increase in inner-airway area (Ai) and decrease in airway wall area percentage (Aw%) in both large (3rd-to 6th-generation) and small (7th-to 9th-generation) airways. Furthermore, the animal study showed a significant reduction in the amount of SM in BT-treated large airways but not in untreated small airways. Protein gene product 9.5 (PGP9.5)-positive nerves and muscarinic receptor 3 (M3 receptor) expression in large and small airways were both markedly decreased throughout the airway wall 12 weeks after BT treatment. CONCLUSIONS: BT significantly reduced nerves, but not SM, in small airways, which might shed light on the mechanism of lung denervation by BT.

6.
Respiration ; 100(11): 1097-1104, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34412056

RESUMO

BACKGROUND: The treatment of pulmonary malignancies remains a challenge. The efficacy and safety of bronchoscopic radiofrequency ablation (RFA) for the treatment of lung cancer are not well elucidated. OBJECTIVE: This study aimed to evaluate the feasibility and safety of RFA guided by bronchoscopic transparenchymal nodule access (BTPNA) in vivo. METHODS: In an attempt to determine the parameters of RFA, we first performed RFA in conjunction with automatic saline microperfusion in the lung in vitro with various ablation energy (10, 15, 20, 25, and 30 W) and ablation times (3, 5, 8, and 10 min). The correlation between ablated area and RFA parameter was recorded and analyzed. Further, we conducted a canine study with RFA by BTPNA in vivo, observing the ablation effect and morphological changes in the lung assessed by chest CT and histopathologic examination at various follow-up time points (1 day, n = 3; 30 days, n = 4; 90 days, n = 4). The related complications were also observed and recorded. RESULTS: More ablation energy, but not ablation time, induced a greater range of ablation area in the lung. Ablation energy applied with 15 W for 3 min served as the appropriate setting for pulmonary lesions ≤1 cm. RFA guided by BTPNA was performed in 11 canines with 100% success rate. Inflammation, congestion, and coagulation necrosis were observed after ablation, which could be repaired within 7 days; subsequently, granulation and fibrotic scar tissue developed after 30 days. No procedure-related complication occurred during the operation or in the follow-up periods. CONCLUSION: The novel RFA system and catheter in conjunction with automatic saline microperfusion present a safe and feasible modality in pulmonary parenchyma. RFA guided by BTPNA appears to be well established with an acceptable tolerance; it might further provide therapeutic benefit in pulmonary malignancies.

8.
Nat Commun ; 12(1): 4616, 2021 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-34326339

RESUMO

Conventional ultrafine-grains can generate high strength in Mg alloys, but significant tradeoff of corrosion resistance due to inclusion of a large number of non-equilibrium grain boundaries. Herein, an ultrafine-grain structure consisting of dense ultrafine twins is prepared, yielding a high strength up to 469 MPa and decreasing the corrosion rate by one order of magnitude. Generally, the formation of dense ultrafine twins in Mg alloys is rather difficult, but a carefully designed multi-directional compression treatment effectively stimulates twinning nucleation within twins and refines grain size down to 300 nm after 12-passes compressions. Grain-refinement by low-energy twins not only circumvents the detrimental effects of non-equilibrium grain boundaries on corrosion resistance, but also alters both the morphology and distribution of precipitates. Consequently, micro-galvanic corrosion tendency decreases, and severe localized corrosion is suppressed completely. This technique has a high commercial viability as it can be readily implemented in industrial production.

9.
Transl Lung Cancer Res ; 10(5): 2218-2228, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-34164271

RESUMO

Background: Airway stenting is frequently used in the palliative treatment of patients with advanced tumor-induced airway stenosis and fistulas. However, there is paucity of studies regarding the use of airway stents in restoring patency. The aim of the study was to assess the efficacy and safety of hybrid silicon Y stents and covered self-expanding metal stents (SEMS) and in reestablishing patency in airway stenoses and fistulas. Methods: This retrospective study included 31 patients between January 2016 to December 2019 with inoperable complex malignant airway stenoses and fistulas, managed with Silicone Y stents, and covered SEMS. The clinical details, clinical outcomes and complications up to 6 months were extracted from medical records. The improvement of performance was assessed based on modified British Medical Research Council (mMRC) dyspnea scores (t=6.892, P<0.001), Karnofsky Performance Scores (KPS) (t=-11.653, P<0.001), and performance status (PS) (t=3.503, P<0.001). Result: A total of 31 silicon Y stents and 35 covered SEMSs were inserted. Of the 31 patients (M:F 20:11; age: 54.64±9.57), 25/31 (80.6%) experienced immediate relief of symptoms following stent placement. Patients' mMRC dyspnea scores, KPS, and PS showed significant improvement following stenting. The mean duration of stent placement was 146.3±47.7 days, and 17/31 (55%) patients were alive at 6 months. No major complications related to hybrid stenting were observed during the follow-up period. Conclusions: Hybrid stenting is a feasible and safe palliative treatment for malignant airway stenosis and fistulas to improve quality of life and can be performed without major complications.

10.
Ther Adv Respir Dis ; 15: 17534666211019564, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34044660

RESUMO

BACKGROUND AND AIMS: Post-tuberculosis bronchial stenosis (PTBS) is one of the most common complications of tracheobronchial tuberculosis. Silicone stent serves as a major treatment for maintaining airway patency. However, silicone stent placement remains a large challenge in patients with severe cicatricial PTBS. Our objective was to evaluate the efficacy and safety of covered, self-expanding, metallic stents (SEMSs) as a transition to silicone stent implantation for treating severe PTBS. METHODS: We retrospectively reviewed the data of patients with severe PTBS who received airway stenting in the First Affiliated Hospital of Guangdong Medical University between September 2015 and May 2019. The types of the stent, intervention procedures, bronchoscopic findings, clinical outcomes and related complications were collected and analyzed. RESULTS: Fifty-eight cases with severe PTBS were included in this study. Thirteen (22.4%) of the patients received bronchial silicone stent implantation immediately after dilations. For the remaining 45 (77.6%) patients, silicone stents could not be deployed after dilations and SEMSs implantation was implemented as a bridge to silicone stenting. The SEMSs were placed for an interval of 28.4 ± 11.1 days. All of the silicone stents were inserted successfully following the removal of SEMSs. No SEMS-related complication occurred. The subgroup analysis showed that patients who received transitional SEMSs had less luminal caliber but fewer transbronchial dilations before silicone stent implantation (p < 0.05). CONCLUSION: Covered SEMS placement as a transition to silicone stenting could serve as a feasible procedure to reduce complications and improve the success rate of silicone stent implantation in patients with severe PTBS.The reviews of this paper are available via the supplemental material section.

11.
World J Gastrointest Surg ; 13(1): 87-95, 2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33552396

RESUMO

BACKGROUND: Anastomosis of the testicular vein with the superior mesenteric vein rarely causes severe gastrointestinal bleeding. To date, there have been few studies describing its appearance on medical imaging. Here, we present multidetector computed tomography three-dimensional and multiplanar reconstruction (MPR) images of a typical digital subtraction angiography showing proven ectopic bleeding and provide the first review of the image performance. CASE SUMMARY: A 68-year-old man who had been rushed to the hospital with a four-day history of melena and fainting underwent multiple esophagogastroduodenoscopy procedures that failed to identify the source of bleeding. We used MPR combined with three-dimensional reconstruction images, and found that the testicular vein had anastomosed with the superior mesenteric vein, and they clustered together in the jejunal vessel wall, which caused severe gastrointestinal bleeding. Digital subtraction angiography confirmed the location of bleeding. After transfusion and embolization therapy, the patient's condition improved. CONCLUSION: Computed tomography-MPR combined with three-dimensional images offers significant value in the localization and qualitative assessment of rare gastrointestinal hemorrhage. The features of multiphase spiral scanning can improve the accuracy of the diagnosis.

12.
Glob Chall ; 5(2): 2000082, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33552555

RESUMO

Photoreduction of CO2 into value-added fuels is one of the most promising strategies for tackling the energy crisis and mitigating the "greenhouse effect." Recently, metal-organic frameworks (MOFs) have been widely investigated in the field of CO2 photoreduction owing to their high CO2 uptake and adjustable functional groups. The fundamental factors and state-of-the-art advancements in MOFs for photocatalytic CO2 reduction are summarized from the critical perspectives of light absorption, carrier dynamics, adsorption/activation, and reaction on the surface of photocatalysts, which are the three main critical aspects for CO2 photoreduction and determine the overall photocatalytic efficiency. In view of the merits of porous materials, recent progress of three other types of porous materials are also briefly summarized, namely zeolite-based, covalent-organic frameworks based (COFs-based), and porous semiconductor or organic polymer based photocatalysts. The remarkable performance of these porous materials for solar-driven CO2 reduction systems is highlighted. Finally, challenges and opportunities of porous materials for photocatalytic CO2 reduction are presented, aiming to provide a new viewpoint for improving the overall photocatalytic CO2 reduction efficiency with porous materials.

13.
J Thorac Dis ; 13(1): 82-91, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33569188

RESUMO

Background: The short-term efficacy of Dumon stent has been well demonstrated. Across years, however, due to insufficient sample size and absent of the randomized controlled trial, no reliable conclusion could be reach for Dumon stent's long-term efficacy. So, we conducted the first meta-analysis to evaluate the long-term efficacy and safety of the Dumon stent for benign tracheal stenosis. Methods: Data on related trials were obtained by doing a literature search in PubMed, Web of Science and Cochrane Library. Random-effect and fixed-effect models were used to calculate the efficacy and incidence of complication of Dumon stent placement. Results: A total of 395 patients from 8 studies were included in this study, revealing that the stability rate was 41.12% (95% CI, 34.85-48.52%) of Dumon stenting. Further, a curative rate of 40.74% (95% CI, 34.92-47.53%), and efficacy of 75.49% (95% CI, 70.89-80.39%) were obtained from this study. Analysis of the incidence of complications indicated 25.04% of migration (95% CI, 17.52-35.79%), 15.66% granulation (95% CI, 9.39-26.11%) and 23.82% of mucus retention 23.82% (95% CI, 13.77-41.20%). Conclusions: Dumon stent has a moderate efficacy for treating benign tracheal stenosis with approximately 20% incidence of complication, regular bronchoscopy follow-up should be conducted. Thus, further research is required to modified Dumon stenting.

14.
ACS Appl Mater Interfaces ; 12(41): 46862-46873, 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-32960039

RESUMO

Device-associated infection is one of the significant challenges in the biomedical industry and clinical management. Controlling the initial attachment of microbes upon the solid surface of biomedical devices is a sound strategy to minimize the formation of biofilms and infection. A synergistic coating strategy combining superhydrophobicity and bactericidal photodynamic therapy is proposed herein to tackle infection issues for biomedical materials. A multifunctional coating is produced upon pure Mg substrate through a simple blending procedure without involvement of any fluoride-containing agents, differing from the common superhydrophobic surface preparations. Superhydrophobic features of the coating are confirmed through water contact angle measurements (152.5 ± 1.9°). In vitro experiments reveal that bacterial-adhesion repellency regarding both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) strains approaches over 96%, which is evidently ascribed to the proposed synergistic strategy, that is, superhydrophobic nature and microbicidal ability of photodynamic therapy. Electrochemical analysis indicates that the superhydrophobic coating provides pronounced protection against corrosion to underlying Mg with 80% reduction in the corrosion rate in minimum essential medium and retains the original surface features after 168 h exposure to neutral salt spray. The proof-of-concept research holds a great promise for tackling the notorious bacterial infection and poor corrosion resistance of Mg-based biodegradable materials in a simple, efficient, and environmentally benign manner.


Assuntos
Antibacterianos/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Escherichia coli/efeitos dos fármacos , Magnésio/farmacologia , Fotoquimioterapia , Staphylococcus aureus/efeitos dos fármacos , Antibacterianos/química , Aderência Bacteriana/efeitos dos fármacos , Materiais Revestidos Biocompatíveis/química , Interações Hidrofóbicas e Hidrofílicas , Magnésio/química , Testes de Sensibilidade Microbiana , Tamanho da Partícula , Propriedades de Superfície
15.
Angew Chem Int Ed Engl ; 59(44): 19716-19721, 2020 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-32924218

RESUMO

Herein we report two new TPE-based 3D MOFs, that is, Sr-ETTB and Co-ETTB (TPE=Tetraphenylethylene, H8 ETTB=4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-3,5-dicarboxylic acid))). Through tailoring outer shell electron configurations of SrII and CoII cations, the fluorescence intensity of the MOFs is tuned from high emission to complete non-emission. Sr-ETTB with strong blue fluorescence shows reversible fluorescence variations in response to pressure and temperature, which is directly related to the reversible deformation of the crystal structure. In addition, non-emissive Co-ETTB counterpart exhibits a turn-on fluorescent enhancement under the stimulation of analyte histidine. In the process, TPE-cored linkers in the MOFs are released through competitive coordination substitution and subsequently reassembled to perform aggregation-induced luminescence behavior originated from the organic linkers.

16.
Chem Commun (Camb) ; 56(40): 5389-5392, 2020 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-32285888

RESUMO

A stable nanoscaled single-excitation ratiometric luminescent pH sensor (MPDB-PCN) over a broad pH range from 2.5 to 8.6 is fabricated through post-synthetic modification of PCN-224 with naphthalimide-derived molecules. Due to the rapid, sensitive and linear response to pH, MPDB-PCN is capable of detecting 3-nitropropionic acid (3-NPA), an acid neurotoxin in food safety, with a low detection limit of 15 µM in sugarcane juice.


Assuntos
Substâncias Luminescentes/química , Estruturas Metalorgânicas/química , Micotoxinas/análise , Nanopartículas/química , Contaminação de Alimentos/análise , Concentração de Íons de Hidrogênio , Limite de Detecção , Neurotoxinas/análise , Nitrocompostos/análise , Extratos Vegetais/análise , Propionatos/análise , Saccharum/química , Espectrometria de Fluorescência/métodos , Zircônio/química
17.
Cancer Manag Res ; 11: 9439-9448, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31807073

RESUMO

Purpose: This study aimed to develop and validate a nomogram for predicting the malignancy of small (8-20 mm) solid indeterminate solitary pulmonary nodules (SPNs) in a Chinese population by using routine clinical and computed tomography data. Methods: The prediction model was developed using a retrospective cohort that comprised 493 consecutive patients with small indeterminate SPNs who were treated between December 2012 and December 2016. The model was independently validated using a second retrospective cohort comprising 216 consecutive patients treated between January 2017 and May 2018. The investigated variables included patient characteristics (e.g., age and smoking history), nodule parameters (e.g., marginal spiculation and significant enhancement), and tumor biomarker levels (e.g., carcinoembryonic antigen). A prediction model was developed by using multivariable logistic regression analysis, and the model's performance was presented as a nomogram. The model was evaluated based on its discriminative ability, calibration, and clinical usefulness. Results: The developed nomogram was ultimately based on age, marginal spiculation, significant enhancement, and pleural indentation. The Harrell concordance index values were 0.869 in the training cohort (95% confidence interval: 0.837-0.901) and 0.847 in the validation cohort (95% confidence interval: 0.792-0.902). The Hosmer-Lemeshow test revealed good calibration in each of the training and validation cohorts. Decision curve analysis confirmed that the nomogram was clinically useful (risk threshold from 0.10 to 0.85). Conclusion: Patient age, marginal spiculation, significant enhancement, and pleural indentation are independent predictors of malignancy in small indeterminate solid SPNs. The developed nomogram is easy-to-use and may allow the accurate prediction of malignancy in small indeterminate solid SPNs among Chinese patients.

18.
Clin Ther ; 41(11): 2263-2272, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31561881

RESUMO

PURPOSE: The aim of the study is to compare the free hexafluoro-isopropanol (HFIP) concentration in adults' blood and the incidence of emergence agitation (EA) after inhaled different concentrations of sevoflurane. METHODS: Sixty adult patients planning to undergo laparoscopic gastrointestinal surgery were randomly assigned to 3 groups. Each group received sevoflurane as the volatile anesthetic at different concentrations: 0.5 minimum alveolar concentration (MAC), 1.0 MAC, and 1.5 MAC. The use of sevoflurane was continued until the end of surgery. Venous blood samples were obtained at 30, 60, 120, and 180 minutes after starting the use of sevoflurane and subsequently at 60, 180, and 300 minutes after discontinuation of volatile anesthetic administration. Blood concentrations of sevoflurane and free HFIP were determined using gas chromatography. The recovery time and the incidence of EA at different time points were evaluated among the 3 groups. FINDINGS: Changes in the blood concentrations of sevoflurane and free HFIP during and after the use of sevoflurane were similar in all 3 groups. The peak blood concentration of free HFIP occurred 60 minutes after onset of sevoflurane anesthesia in all 3 groups (P < 0.05). The lowest level of free HFIP and the longest recovery time were found in the 1.5-MAC group (P < 0.05). No significant difference was found in the incidence of EA or moderate pain among the 3 groups during recovery. IMPLICATIONS: The generation of HFIP would be inhibited when the inhaled sevoflurane concentration increased to 1.5 MAC. However, the incidence of EA during recovery had nothing to do with the inhaled different sevoflurane concentrations (within 1.5 MAC) in adults. ChicCTR.org identifier: ChiCTR-IPD-17011558.


Assuntos
Anestésicos Inalatórios/efeitos adversos , Delírio do Despertar/induzido quimicamente , Propanóis/sangue , Sevoflurano/efeitos adversos , Idoso , Anestesia , Anestésicos Inalatórios/administração & dosagem , Anestésicos Inalatórios/farmacocinética , Procedimentos Cirúrgicos do Sistema Digestório , Relação Dose-Resposta a Droga , Método Duplo-Cego , Delírio do Despertar/sangue , Feminino , Humanos , Laparoscopia , Masculino , Pessoa de Meia-Idade , Sevoflurano/administração & dosagem , Sevoflurano/farmacocinética
19.
Mater Sci Eng C Mater Biol Appl ; 105: 110042, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546440

RESUMO

Influences of proteins on degradation of magnesium alloys are of great significance but not well understood. In particular the roles of amino acids, the basic unit of proteins in regulating the progress of biodegradation of magnesium based materials remain unclear. This study aims to investigate the impacts of alanine, glutamic acid and lysine on degradation of pure magnesium in phosphate buffer solution through SEM, XPS, FTIR, potentiodynamic polarisation curves, electrochemical impedance spectroscopy and immersion tests. The changed contents of amino acids in solutions were detected by UV-vis spectrophotometer. Results demonstrate that the charges of the selected amino acids imposed significant contribution to suppressing the degradation of pure magnesium in phosphate buffer solution. The presence of amino acids led to the formation of phosphate-based corrosion products, increasing free corrosion potential, and reduction in corrosion current density and solution pH depending on their isoelectric points and molecular structures. A plausible corrosion mechanism organised by amino acids on pure magnesium was proposed.


Assuntos
Aminoácidos/química , Magnésio/química , Fosfatos/química , Tampões (Química) , Corrosão , Espectroscopia Dielétrica , Eletroquímica , Humanos , Hidrogênio/análise , Ponto Isoelétrico , Conformação Molecular , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Difração de Raios X
20.
Mater Sci Eng C Mater Biol Appl ; 104: 109926, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499938

RESUMO

Despite of technical advancements in design and development of new biomaterials, device-related infections continue to occur and can be life-threatening. Differing from existing research work pertaining to introducing antibacterial function upon device surface, this study attempts to address such germ-infection issues through controlled release of antibacterial species from bulk gallium (Ga) and strontium (Sr) containing magnesium (Mg) alloys. To validate such a conceptual framework, Mg alloys containing micro-level concentrations of Ga and/or Sr (0.1 wt%) are employed as model materials, along with commercially pure Mg and titanium (Ti) as control groups. Biodegradation progress of such metal specimens is examined through pH and mass loss measurements, and inductively coupled plasma - atomic emission spectrometry (ICP-AES) as a function of immersion time in Trypticase Soy Broth (TSB) solution under physiological conditions. In vitro biocompatibility and antibacterial performance are characterised through MTT proliferation assay with human mesenchymal stem cells (hMSCs) and the spread plate method with three representative bacterial strains, i.e. S. aureus (ATCC 43300), E. coli (ATCC 25922), and S. epidermidis (ATCC 35984). Animal tests are performed through implanting target metal rods into femurs of Sprague Dawley rats, accompanied with injection of S. aureus to build a model of osteomyelitis. Results demonstrate that such lean additions of Ga and/or Sr reduce the degradation kinetics of Mg matrix, and the release of Ga3+ ions plays a crucial role in disabling the viability of all selected bacterial strains. The histological tests confirm that the growth of fibrous tissue has been accelerated in the vicinity of Mg-based implants, in comparison to that of blank and c.p. Ti controls. It is also striking that the smallest number density of S. aureus bacteria on the surface of the retrieved Ga-containing Mg rod implants. Such a proof-of-concept study provides a new and feasible strategy to address the notorious device-infection issues associated with biomedical implants for bone fracture management.


Assuntos
Ligas/farmacologia , Antibacterianos/farmacologia , Gálio/farmacologia , Magnésio/farmacologia , Estrôncio/farmacologia , Animais , Morte Celular/efeitos dos fármacos , Fêmur/efeitos dos fármacos , Fêmur/patologia , Humanos , Implantes Experimentais , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Ratos Sprague-Dawley
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