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The internal topography of the root canal is complex, especially for the permanent molar's mesial root. In response to such issues, improved irrigation techniques have been created, which use laser pulses to agitate fluids and improve microbial deposit removal. Objective: To assess the effectiveness of the Er,Cr:YSGG laser with a wavelength of 2,780 nm via photon-induced photoacoustic streaming (PIPS) protocol which agitated of 2% chlorohexidine (CHX) in removing mature Enterococcus faecalis (E. faecalis) biofilm in root canal systems of lower molars. Material and Methods: The mesial roots of lower first and second molars were separated and inoculated with E. faecalis bacterial suspension for 30 days. The roots were irrigated with CHX, some of them were agitated with a passive ultrasonic device (PUI), while the other roots were agitated by an Er,Cr:YSGG laser in PIPS at 60 µs/pulse, 5 Hz, (0.25, 0.5, 0.75, and 1) W. An atomic force microscope (AFM) was used as a new method to get the results in the isthmus area; the obtained results from each group were compared with each other. Results: Based on the AFM and SEM analyses, laser and ultrasonic activation groups showed higher antimicrobial efficacy than the conventional syringe irrigation group (P<0.05). Conclusion: Based on the investigation's findings, the activation of 2% CHX solution by Er,Cr:YSGG laser in PIPS and PUI offers better mature bacterial biofilm removal in the mesial root of lower human molars than the same irrigant with the SI technique (AU)
A topografia interna do canal radicular é complexa, especialmente para a raiz mesial do molar permanente. Em resposta a esses problemas, foram criadas técnicas aprimoradas de irrigação, que utilizam pulsos de laser para agitar fluidos e melhorar a remoção de depósitos microbianos. Objetivo: Avaliar a eficácia do laser Er,Cr:YSGG com comprimento de onda de 2.780 nm via protocolo de streaming fotoacústico induzido por fótons (PIPS) que agitou clorohexidina a 2% (CHX) na remoção de Enterococcus faecalis maduro (E. faecalis) biofilme em sistemas de canais radiculares de molares inferiores. Material e Métodos: As raízes mesiais de 28 primeiros e segundos molares inferiores foram separadas e inoculadas com suspensão bacteriana de E. faecalis por 30 dias. As raízes foram irrigadas com CHX, sendo algumas delas agitadas com aparelho ultrassônico passivo (PUI), enquanto as demais raízes foram agitadas com laser Er,Cr:YSGG em PIPS a 60 µs/pulso, 5 Hz (0,25, 0,5, 0,75 e 1) W. Um microscópio de força atômica (AFM) foi utilizado como um novo método para obter os resultados na área do istmo; os resultados obtidos de cada grupo foram comparados entre si. Resultados: Com base nas análises de AFM e SEM, os grupos de ativação por laser e ultrassom apresentaram maior eficácia antimicrobiana do que o grupo de irrigação com seringa convencional (P<0.05). Conclusão: Com base nos achados da investigação, a ativação da solução de CHX a 2% pelo laser Er,Cr:YSGG em PIPS a (60 µs/pulso, 5 Hz, 0,75 W) oferece melhor remoção de biofilme (AU)
Subject(s)
Enterococcus faecalis , Dental PlaqueABSTRACT
At present, the exact pathogenesis of dental fluorosis is not clear, and there is no exact standard of enamel acid etching in the adhesive restoration of dental fluorosis. Atomic force microscope represents a great progress in high-resolution imaging of biomaterials, and its advantage is that it can provide three-dimensional images and quantitative data of observed samples at the nanometer level. In recent years, the application of atomic force microscope in enamel study has made some progress. Whether the quantitative analysis of enamel ultrastructure can become a new way to study the pathogenesis of dental fluorosis and find the best repair method is worthy of further exploration. This paper reviews the application of atomic force microscope in the study of enamel with dental fluorosis.
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SUMMARY: The aim of this study was to explore promoting effect of external applying Panax Notoginseng Saponins (PNS) on fractures. For this analysis 18 New Zealand male rabbits were divided into control group, splintage group and PNS group. All rabbits were performed left radius fractures and natural healing, splintage healing and splintage coated with PNS healing. 2 rabbits in each group were sacrificed on day 14, day 28 and day 42 after surgery, separately. Atomic force microscope scanning and nanoindentation tests were performed on the callus sections. The particle size and roughness in PNS group was both less than that in splintage group. The elastic modulus of callus in PNS group was consistent with normal bone tissue started from day 28 after surgery, two weeks earlier than that in splintage group. PNS could significantly reduce fracture healing time and increase strength of callus.
RESUMEN: El objetivo de este estudio fue evaluar el efecto de la aplicación externa de Panax Notoginseng Saponins (PNS) en fracturas óseas. Se usaron 18 conejos machos de raza Nueva Zelanda divididos en grupos control, entablillado y PNS. Se realizaron fracturas del radio izquierdo y cicatrización natural en todos los animales, además de la cicatrización con entablillado y entablillado recubierto con PNS. Se sacrificaron, posterior a la cirugía, dos conejos de cada grupo los día 14, 28 y 42. Se realizaron pruebas de escaneo con microscopio de fuerza atómica y nanoindentación en las secciones de callos. El tamaño de la partícula y la rugosidad en el grupo de PNS fue menor que en el grupo entablillado. El módulo elástico del callo en el grupo de PNS fue consistente con el tejido óseo normal iniciado el día 28 después de la cirugía, dos semanas antes que en el grupo de entablillado. El PNS podría redu- cir significativamente el tiempo de curación de la fractura y aumentar la fuerza del callo.
Subject(s)
Animals , Male , Rabbits , Saponins/administration & dosage , Fracture Healing/physiology , Microscopy, Atomic Force , Fractures, Bone/drug therapy , Panax notoginseng/chemistry , Saponins/chemistry , Fractures, Bone/surgeryABSTRACT
Objective To study the hardness properties of pig esophageal at the nanoscale using atomic force microscope (AFM). Methods The porcine esophagus was chosen as experimental sample to study the hardness properties of esophageal tissues at different loading rates, deflection and dwell time with AFM. Results The hardness of esophageal tissues at the nanoscale was strongly correlated with the loading rate and the deflection, which increased with the increasing loading rate and decreased with the increasing deflection of cantilever. The difference in the hardness was associated with the viscoelasticity and viscoplasticity of esophageal tissues, including contact stress, energy transition and strain plastic gradient. Conclusions The experimental results have important significance for clinical diagnosis, surgical operation and artificial material development, and reveal the changing patterns for mechanical properties of the esophageal tissues at the microscale.
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@#Dental bonding technology and materials have been used widely in dentistry because of their excellent properties. The development of novel bonding technology and materials is constantly being performed to improve the effect of dental bonding restorations. Observation and analysis of the dental bonding interface is one of the most important methods for laboratory evaluation of bonding efficiency. This paper aims to review the methods of observation and analysis of dental bonding interfaces to provide a reference for the selection of evaluation methods in dental bonding research. The features of 6 methods, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), Raman spectroscopy (RS), optical coherence tomography (OCT) and atomic force microscopy (AFM), were described and summarized. Among these methods, SEM and TEM are used most often in the analysis of fine structures; CLSM and OCT are used for the acquisition of characteristic image signals, such as microleakage and exogenous and endogenous fluorescence; and RS and AFM can test chemical composition and mechanical properties.
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BACKGROUND: Articular cartilage has a high-weight-bearing area and a low-weight-bearing area. There are different macroscopic elastic moduli in the two regions, but the modulus of the two areas at the micro and nano levels is unknown. Such information is important for further understanding of cartilage micro and nano mechanics. Moreover, the micro and nano structures of the two areas, which influence the cartilage mechanical properties, should be discussed. OBJECTIVE: To investigate the mechanical properties and structure of high- and low-weight-bearing areas of the hip articular cartilage at the micro and nano levels. METHODS: Normal porcine femoral head cartilage was used. Atomic force microscopy with a spherical tip of 5 µm in diameter was used to measure the microscale compressive elastic modulus of different weight-bearing areas of the cartilage. The nanoscale compressive elastic modulus, nano structure, and collagen fiber diameter were measured using a ScanAsyst-Air probe with a radius of curvature of 5 nm. Scanning electron microscopy was employed to identify the microstructure of different weight-bearing areas of the cartilage. RESULTS AND CONCLUSION: The microscale elastic modulus of the high-weight-bearing area of the femoral head cartilage was (433.05±146.52) kPa, and the microscale elastic modulus of the low-weight-bearing area was (331.19±84.88) kPa. The nanoscale elastic modulus of the high- and low-weight-bearing areas of the femoral head cartilage was (1.24±0.42) GPa and (1.28±0.41) GPa, respectively. While no statistically significant differences were found in the elastic modulus of collagen fibers at the nano level (P=0.846 2). The collagen fibers of the high-weight-bearing area arranged more regularly than those of the low-weight-bearing area at the micro level. No significant differences between collagen fiber diameter of the two areas at the nano level were observed (P=0.926 4). To conclude, the collagen fibers of the high-weight-bearing area are cross-linked more regularly than those of low-weight-bearing area. Therefore, the compressive elastic modulus of the high-weight-bearing area at the micro level is significantly higher than that of the low-weight-bearing area, which is consistent with the macroscopic compressive elastic modulus trend. However, high-weight-bearing has no impact on individual collagen fibers at the nano level.
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This study aimed to explore the link between block copolymers' interfacial properties and nanoscale carrier formation and found out the influence of length ratio on these characters to optimize drug delivery system. A library of diblock copolymers of PEG-PCL and triblock copolymers with additional PEI (PEG-PCL-PEI) were synthesized. Subsequently, a systematic isothermal investigation was performed to explore molecular arrangements of copolymers at air/water interface. Then, structural properties and drug encapsulation in self-assembly were investigated with DLS, SLS and TEM. We found the additional hydrogen bond in the PEG-PCL-PEI contributes to film stability upon the hydrophobic interaction compared with PEG-PCL. PEG-PCL-PEI assemble into smaller micelle-like (such as PEG-PCL4006-PEI) or particle-like structure (such as PEG-PCL8636-PEI) determined by their hydrophilic and hydrophobic block ratio. The distinct structural architectures of copolymer are consistent between interface and self-assembly. Despite the disparity of constituent ratio, we discovered the arrangement of both chains guarantees balanced hydrophilic-hydrophobic ratio in self-assembly to form stable construction. Meanwhile, the structural differences were found to have significant influence on model drugs incorporation including docetaxel and siRNA. Taken together, these findings indicate the correlation between molecular arrangement and self-assembly and inspire us to tune block compositions to achieve desired nanostructure and drug loading.
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Abstract Trans-endodontic implants are an artificial extension through root apex anchored in periradicular bone tissue. The aim is to improve the crown-root ratio and to provide stability to dental organ present. Zirconium oxide (ZrO2) is a material of great technological importance, having good natural color, high strength, high toughness, high chemical stability, does not suffer any corrosion, chemical and microbial resistance and excellent esthetic properties. Objective: The aim of this study was to evaluate chemical and microscopy of surface conditions of ZrO2 trans-endodontic implant. Materials and Methods: A blocks of ZrO2 were manufactured for produce trans-endodontic implants and divided in two groups: monoclinic and tetragonal phase. They were evaluated using Scanning Electroning Microscope (SEM), EnergyDispersive X-ray Spectroscopy (EDS), and Atomic Force Microscope (AFM) and Vickers Micro hardness. Results: The Monoclinic phase through AFM analysis showed roughness Ra = 0.320μm, whereas in the Tetragonal phase was 0.126μm, SEM/EDX indicated that the phases are not properly uniform and the addition of the Yttrium to favor the stabilization of the Tetragonal phase. The Vickers hardness analysis showed a value of 1500HV. Conclusion: The characterization of the surface of trans-endodontic zirconium oxide implants provides a guideline to know the surface characteristics of the material, since a greater roughness on the surface of the implant will favor the Osseo-integration capacity.
Resumen Los implantes trans-endodónticos son una extensión artificial a través del ápice radicular anclado en el tejido óseo periradicular. El objetivo es mejorar la relación corona-raíz y proporcionar estabilidad al órgano dental presente. El óxido de zirconio (ZrO2) es un material de gran importancia tecnológica, con buen color natural, alta resistencia, alta tenacidad, alta estabilidad química, no sufre corrosión, resistencia química y microbiana y excelentes propiedades estéticas. Objetivo: El objetivo de este estudio fue evaluar las condiciones superficiales de ZrO2 para su aplicación clínica a los implantes transendodónticos. Materiales y Métodos: se trituraron bloques de ZrO2 en implantes trans-endodónticos y se dividieron en: monoclínico y tetragonal. Luego se evaluaron mediante microscopía electrónica de barrido (SEM), espectroscopia de rayos X de energía dispersiva (EDS) y microscopio de fuerza atómica (AFM) y microdureza vickers. Resultados: La fase monoclínica a través del análisis AFM presenta Ra = 0.320 μm, mientras que en la fase Tetragonal es 0.126 μm, SEM / EDS muestra que las fases no son adecuadamente uniformes y la adición del Ytrio para favorecer la estabilización de la fase tetragonal. El análisis de microdureza mostro un valor de 1500HV. Conclusión: La caracterización de la superficie de los implantes trans-endodónticos de óxido de zirconio, brinda una pauta para conocer las características superficiales del material, ya que al haber una mayor rugosidad en la superficie del implante se verá favorecida la capacidad de oseointegración.
Subject(s)
Spectrometry, X-Ray Emission , Zirconium/therapeutic use , Dental Implants/microbiologyABSTRACT
This study investigated and compared the surface roughness achieved by glazing porcelain samples in a conventional and a microwave oven. Materials and Methods: Two commercial brands of metal ceramics were used, VITA VMK MASTER and IPS CLASSIC. Sixty samples were fabricated, 30 for each type of ceramic. The samples were sintered in the conventional oven and hand-polished to remove any irregularities. Samples (n = 10) from each type of ceramic were further divided into three groups as follows: hand-polished (Group A), conventional oven glazed (Group B), and microwave glazed (Group C). Each specimen was evaluated for surface roughness by atomic force microscope. Data were statistically analyzed using two-way analysis of variance (ANOVA) and Tukey's post hoc test (a = 0.05). Results: Two-way ANOVA indicated a highly significant difference in surface roughness based on the type of glazing (P < 0.001), there was a significant difference based on the metal ceramics (P = 0.002). There was also a significant interaction between the type of glazing and metal ceramics (P = 0.009). The images obtained from the atomic force microscope corroborated the measured values. Conclusions: All the results indicate that microwave glazing can be a feasible option for glazing porcelain specimens. It was concluded that surface topography is influenced by surface treatment and microwave glazed ceramic is superior to conventional oven glazed ceramic and hand-polishing showed greater surface roughness when compared to glazing. IPS CLASSIC ceramic showed relatively smooth surface when compared to VITA VMK MASTER irrespective of the surface treatment.
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Objective @#To investigate different Er:YAG laser power settings on the bonding properties of IPS e.max CAD ceramics. @*Methods@# 96 IPS e.max CAD ceramics blocks (5 mm × 5 mm × 5 mm) were prepared and randomly divided into 8 groups (n = 12), the untreated blocks served as the control, while one of the experimental groups was treated with 4.5% HF for 20 seconds, six remaining test group (C、D、E、F、G、H) were treated with different Er: YAG laser power settings: 100 mJ、200 mJ、300 mJ、400 mJ、500 mJ and 600 mJ. Morphology of the ceramic surface was observed by atomic force microscopy and its shear bond strength (SBS) was tested. @*Results @#Higher shear bond strength values were found in group C-H compared to group B, the highest is group F (24.12 ± 1.91) MPa. The difference was statistically significant. The atomic force microscope observation of the surface structure showed that the control group was smooth and flat, and the HF-like etching group formed a uniform needle-like convex structure. The laser group gradually formed a regularly arranged cylindrical convex structure, in which the surface of the G and H groups was damaged. @*Conclusion @#The Er: YAG laser power settings of 400 mJ can be used as an effective pretreatment method before bonding of IPS e.max CAD ceramic.
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<p><b>OBJECTIVE</b>To study the effects of Astragalus polysaccharide (APS), the primary effective component of the Chinese herb medicine Astragalus membranaceus (frequently used for its anti-hepatic fibrosis effects), on nanoscale mechanical properties of liver sinusoidal endothelial cells (SECs).</p><p><b>METHODS</b>Using endothelial cell medium as the control, 5 experimental groups were established utilizing different concentrations of APS, i.e. 12.5, 25, 50, 100, and 200 μg/mL. By using atomic force microscopy along with a microcantilever modified with a silicon dioxide microsphere as powerful tools, the value of Young's modulus in each group was calculated. SAS 9.1 software was applied to analyze the values of Young's modulus at the pressed depth of 300 nm. Environmental scanning electron microscopy was performed to observe the surface microtopography of the SECs.</p><p><b>RESULTS</b>The value of Young's modulus in each APS experimental group was significantly greater than that of the control group: as APS concentration increased, the value of Young's modulus presented as an increasing trend. The difference between the low-concentration (12.5 and 25 μg/mL) and high-concentration (200 μg/mL) groups was statistically significant (P<0.05), but no significant differences were observed between moderateconcentration (50 and 100 μg/mL) groups versus low- or high-concentration groups (P>0.05). Surface topography demonstrated that APS was capable of increasing the total area of fenestrae.</p><p><b>CONCLUSIONS</b>The values of Young's modulus increased along with increasing concentrations of APS, suggesting that the stiffness of SECs increases gradually as a function of APS concentration. The observed changes in SEC mechanical properties may provide a new avenue for mechanistic research of anti-hepatic fibrosis treatments in Chinese medicine.</p>
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Animals , Rats , Astragalus Plant , Chemistry , Biomechanical Phenomena , Elastic Modulus , Endothelial Cells , Cell Biology , Liver , Cell Biology , Microscopy, Atomic Force , Microspheres , Nanotechnology , Polysaccharides , Pharmacology , Silicon Dioxide , Chemistry , Surface PropertiesABSTRACT
The study of interaction mechanism between chrysin and leptin was investigated by various spectroscopic techniques and atom force microscope. The ultraviolet spectrum presents a red shift in 200-220 nm after chrysin upon. And there is a structure alternative showed in 270 nm when the concentration ratio of chrysin and leptin in 10-15. From the fluorescence spectrum, it was found that chrysin could combine with leptin in physiological condition. The binding constant (Ka) values, at 298 K and 310 K, were (0.41±0.05)×10⁶ and (3.26±0.46)×10⁶ L·mol⁻¹, and the binding site number were 1.02±0.04 and 0.51±0.01, respectively. The atom force microscope results showed that the dimension of leptin molecules became more swollen after binding with chrysin because of the hydrophobicity. These results demonstrate that the mechanism of chrysin and leptin interaction could play a role in leptin adjust in human body, and it could provide a new aspect for the study of obesity treatment.
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Objective@#To investigate different Er:YAG laser power settings on the bonding properties of IPS e.max CAD ceramics. @*Methods @# 96 IPS e.max CAD ceramics blocks (5 mm × 5 mm × 5 mm) were prepared and randomly divided into 8 groups (n = 12), the untreated blocks served as the control, while one of the experimental groups was treated with 4.5% HF for 20 seconds, six remaining test group (C、D、E、F、G、H) were treated with different Er: YAG laser power settings: 100 mJ、200 mJ、300 mJ、400 mJ、500 mJ and 600 mJ. Morphology of the ceramic surface was observed by atomic force microscopy and its shear bond strength (SBS) was tested. @*Results @#Higher shear bond strength values were found in group C-H compared to group B, the highest is group F (24.12 ± 1.91) MPa. The difference was statistically significant. The atomic force microscope observation of the surface structure showed that the control group was smooth and flat, and the HF-like etching group formed a uniform needle-like convex structure. The laser group gradually formed a regularly arranged cylindrical convex structure, in which the surface of the G and H groups was damaged. @*Conclusion@# The Er: YAG laser power settings of 400 mJ can be used as an effective pretreatment method before bonding of IPS e.max CAD ceramic.
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Objective To explore the surface morphological and biomechanical properties differences of peripheral blood mononuclear cells (PBMCs) between groups of patients with mitochondrial diabetes caused by mt.3243A ＞ G mutation and healthy controls.Methods 2 milliliters blood were obtained from each subject of the mitochondrial diabetes group (n =5) and the control group (n =5).The PBMCs were separated from the blood using the standard Ficoll-Hypaque density-gradient centrifugation method and detected by atomic force microscope (AFM).Results The morphological analysis revealed that compared with control group,the PBMCs of diabetic patients tended to have a lower cell height (0.73 ± 0.24μm vs 2.49 ± 1.17μm,P =0.011) and a much rougher cell membrane (Ra:161.8 ± 33.2nm vs 66.4 ± 16.3 nm,P =0.000;Rq:202.2 ± 40.9nm vs 85.4 ± 17.1 nm,P =0.000).The adhesion force distribution was nearly three times higher in PBMCs of diabetic patients than that of the control group (779.6 ± 190.0pN vs 161.1 ± 83.1 pN,P =0.000).The Young's modulus of PBMCs was significantly increased in diabetic patients (421.4 ± 140.0kPa vs 138.3 ± 77.2kPa,P ＜ 0.01),indicating that diabetic PBMCs were stiffer than control cells.Conclusion Our study demonstrated the surface morphological and biomechanical properties changes in mitochondrial diabetes caused by mt.3243A ＞ G mutation at PBMCs level,which was beneficial to the better understanding of the pathophysiological mechanisms of mitochondrial diabetes associated with mt.3243A ＞ G mutation.
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“Tendon gel” secreted from a parent tendon is regenerated for tendon repair by applying tension. However, the details of the tensile stimulus have not been clarified. This study aimed to evaluate an appropriate tensile stimulus mode and the optimal timing of applying tension to promote tendon gel regeneration. Tendon gel was prepared using a film model method in mice and was preserved in vivo for 3, 5, and 10 days. Unlike tendon gel on day 3 or day 5, a fibrous structure developed in the tendon gel on day 10 when tension was applied. Infrared spectroscopy revealed that characteristic peaks appearing for the tendon gel on days 3 and 5 disappeared on day 10. Disappearance of the peaks indicated maturity of the tendon gel, and it showed the optimal timing for tension application to the tendon gel. The effect of tensile load on tendon gel preserved for 10 days was investigated using a tensile test, a creep test, or a cycle test. In the tensile test, tendon gel was elongated into a thin cord of collagen fibers with an increase in stress, and the maximum diameter of the collagen fiber was approximately 50 times larger than that in the normal Achilles tendon of mice. The results suggest that the diameter of the oriented collagen fiber is controllable by adjusting the applied load and the time in mature tendon gel.
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Animals , Humans , Mice , Achilles Tendon , Collagen , Methods , Parents , Regeneration , Spectrum Analysis , TendonsABSTRACT
Aim To study the mechanism of DSF-Cu induced apoptosis of human nasopharyngeal carcinoma CNE-2 Z cells by affecting the function of mitochondria and cytoskeleton. Methods The cell cycle,the rate of apotosis,the levels of intracellular ROS and MMP in CNE-2 Z cells were tested by flow cytometry after trea-ted with different concentration of DSF-Cu. The chan-ges of the cell surface morphology, ultrastructure, cell height, width and roughness were detected by AFM. The distribution and reorganization of cytoskeleton F-actin were observed by Laser scanning confocal micro-scope. Results Cells were incubated with different concentration of DSF-Cu ( 0 ~200 nmol · L-1 ) for 24 h, the apoptotic ratio increased significantly and the treatment of DSF-Cu resulted in a concentration-de-pendent accumulation of CNE-2Z cells in G2/M phase. Furthermore,the treatment of DSF-Cu was able to in-crease the production of intracellular ROS and decrease the MMP in CNE-2Z cells. In addition,AFM imaging showed that compared to the control group,with the in-crease of DSF-Cu concentration,the CNE-2Z cells be-came smaller, cytoplasm condensed, the height in-creased,and the surface roughness reduced. Moreover, the filopodia became shorter, shrinked and even com-pletely destroyed after treated with different concentra-tion of DSF-Cu. At last,the LSCM image showed that the fluorescence intensity of F-actin networks was de-creased, then the structure was rearranged and de-stroyed obviously by treated with DSF-Cu. Conclusion DSF-Cu can induce apoptosis and arrest cell cycle at G2/M phase in CNE-2Z cell through a mitochondria-dependent pathway. Above findings highlight the appli-cations of AFM at the single cell level for the investiga-tion of antineoplastic drug in nasopharyngeal carcinoma therapy.
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Objective To investigate changes of the elastic modulus of astrocytes induced by injury. Methods The astrocytes were isolated and extracted from the 2-day old SD rats, and identified by immunofluorescence staining with glial fiber acidic protein (GFAP) antibody. Cells were divided into control group and injured group. The injured group was astrocytes 6 h after being injured by the cell damage instrument. The control group was astrocytes without any injury. The elastic modulus in liquid phase was tested by atomic force microscope in two groups. Results were compared and analyzed between two groups. Results The purification rate of rat astrocytes was more than 95%. Six hours after the injury, the astrocytes were in disorder, and some of cell bodies were swelling. The mechanical topographic maps and force indentation curves were obtained. The elastic modulus of astrocytes was significantly increased in injured group compared with that of control group[(1 689±693) Pa vs. (724±283) Pa, P<0.01]. Conclusion The injury stimulus increases the elastic modulus of astrocytes, which provides theoretical basis for understanding intracranial physical microenvironment after traumatic brain injury in animal experiments.
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<p><b>OBJECTIVE</b>This study is to determine the common oral streptococcal adhesion forces by using composite resin and glass ionomer cement (GIC) with different degrees of surface roughness via atomic force microscopy (AFM) analysis. The influence of surface roughness on bacterial adhesion force is also discussed.</p><p><b>METHODS</b>Polishing and grinding were applied to obtain 300, 200, 100, and 10 nm surfaces of light-cured composite resin and GIC samples. Surface topography was assessed by AFM analysis. Initial colonizers (Streptococcus sanguinis and Streptococcus mitis) and cariogenic bacterial strains (Streptococcus mutans and Streptococcus sobrinus) were used to obtain bacteria-modified AFM probes. The force-distance curves were also measured by AFM analysis to determine the adhesion forces of bacteria on the surfaces of the composite resin and GIC. Material surface roughness was analyzed using ANOVA, and adhesion forces were subjected to nonparametric analysis (Kruskal-Wallis test). Comparison among groups was performed by Dunn's test. Material surface roughness and bacterial adhesion forces were subjected to correlation analysis.</p><p><b>RESULTS</b>Bacterial adhesion forces increased with increasing material roughness. The adhesion forces of the four bacterial species reached the maximum on the material surface of 300 nm. The adhesion force of Streptococcus mutans increased from 0.578 nN to 2.876 nN on GIC surfaces with 10 and 300 nm roughness. The adhesion forces of the four species on the surface of the composite resin were stronger than that of GIC. The initial colonizers exhibited stronger adhesion forces to different materials than the cariogenic strains. Intergroup differences were evident on the 200 and 300 nm material surfaces.</p><p><b>CONCLUSIONS</b>The surface roughness of the material significantly affected the bacterial adhesion forces, and a significant linear correlation existed between both factors. The bacterial adhesion forces of the GIC were lower than that of the composite resin. Furthermore, surface roughness exhibited less influence on the cariogenic strains than that on the initial colonizers.</p>
Subject(s)
Bacterial Adhesion , Composite Resins , Dental Materials , Glass Ionomer Cements , Microscopy, Atomic Force , Streptococcus mutans , Streptococcus sobrinus , Surface PropertiesABSTRACT
Objective To study mechanical responses from mesenchymal stem cells (MSCs) under different mechanical stimulus duration, by measuring its elastic modulus and characterizing its stress fibers. Methods High resolution images of MSCs cytoskeleton in vitro were acquired by using atomic force microscope (AFM) and laser scanning confocal microscope (LSCM). AFM cantilever with micro-bead attached probe was used to perform force-distance curve experiment on MSCs at the approaching time of 0.1，0.5, 1, 5,10 s, respectively. The elastic modulus of MSCs at 300 nm indentation depth were measured and compared. Results The rat MSCs cytoskeleton presented an intensely organized network structure. The elastic modulus of rat MSCs varied obviously for different mechanical stimulus duration. The median and quartile (QR) of MSCs elastic modulus were 10.02 (QR=9.66),1.94 (QR=7.71),3.63 (QR=19.33),17.15(QR=35.13), 23.52 kPa(QR=34.87), with probe approaching time at 0.1，0.5, 1, 5,10 s, respectively. The MSCs elastic modulus showed the tendency of increasing with stimulus duration increasing, except for the extremely short stimulus (0.1 s). Conclusions Unlike inorganic elastomer, rat MSCs possess complete and flexible mechanical load-bearing structure and can respond actively to a relatively longer mechanical stimulation, with an increase of elastic modulus. These results may provide basic data for further tissue engineering researches on mechanical regulation of MSCs behavior.
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Stem cells transplantation had been proved to be effective in many clinical diseases. However, microenvi-ronment can influence their growth, migration and differentiation. Under chemical microenvironment, such as hypoxia, neu-ral growing factors and different kinds of ions, stem cells had been intensively studied while little is known about their perfor-mance under physical microenvironment. The effects of mechanical forces, elasticity and rigidity of the matrix of stem cells are still to be further investigated. This article is to summarize how microenvironment controls the fate of stem cells and to re-view the measurement of the mechanical properties.