Determination of work of adhesion of biological cell under AFM bead indentation

Hertz contact theory has been widely used for the determination of cell elasticity based on AFM indentation experiments. In light of the adhesive contact between AFM tip and cell, this study applied Johnson–Kendall–Roberts (JKR) model to fit the indentation force–displacement (F–D) curves reported previously. A MIN6 cell has been modeled as first a sphere and then a flattened cell with different thicknesses. The results have shown that both basic JKR model and “generalized” JKR model can best describe the unloading force–displacement behaviors of the indentation curves. The Young׳s modulus of the cell and the work of adhesion of the cell–indenter interface are obtained. In comparison to the Hertzian contact model, the JKR model provides obviously better fitting to the experimental results, indicating that the adhesion is significant in the cell interaction

Selective measurement of anti-tTG antibodies in coeliac disease and IgA deficiency : an alternative pathway

Objective To determine the ability of selective antibody testing to screen for coeliac disease in the presence of IgA deficiency and to define the sensitivity of a pathway using this method (Figure1). Method All IgA and IgG anti-tTG tests performed at our centre between January 2008 and December 2009, using the Immunocap 250 analyser, were retrospectively reviewed. Positive results were correlated with histology. Results were used to validate our diagnostic pathway. Results 12,289 consecutive serological tests were reviewed. IgA deficient patients gave either an “error” reading or very low response on the Immunocap 250 analyser. Subsequent testing of this sub-group demonstrated raised IgG anti-tTG antibodies in those with histologically proven coeliac disease. Conclusions Using our antibody screening pathway, which involves the selective use of IgG antitTG, sensitivity increased from 87% to 92% in those with IgA deficiency. Adoption of this pathway for coeliac screening would negate the routine screening of immunoglobulin levels, with resultant cost saving

Capillary force in adhesive contact between hydrogel microspheres

The paper reports an experimental study of the adhesive contact between liquid-bridged hydrogel microparticles. A novel nanomechanical tester has been developed to measure both the force-approach curves at sub-micro resolutions as well as the side-view images between two agarose spheres during pull-off. Meanwhile, the JKR theory has been extended to quantify the work of adhesion at the solid-liquid-vapor interface and Young’s modulus of the particles based on the measured parameters. Our research findings show the work of adhesion is independent of the separation speed and, by contrast, Young’s modulus exhibits a linear increase. Our study also demonstrates that JKR reconciles with the generalized Hertz theory, which takes capillary force into account for soft microspheres in a relationship that the work of adhesion is equal to twice the surface tension of water. These new findings are essential for developing techniques to quantitatively characterize capillary adhesion of soft particulate materials and potentially to improve the material performance in their applications

Soft polymer-based technique for cellular force sensing

Soft polymers have emerged as a vital type of material adopted in biomedical engineering to perform various biomechanical characterisations such as sensing cellular forces. Distinct advantages of these materials used in cellular force sensing include maintaining normal functions of cells, resembling in vivo mechanical characteristics, and adapting to the customised functionality demanded in individual applications. A wide range of techniques has been developed with various designs and fabrication processes for the desired soft polymeric structures, as well as measurement methodologies in sensing cellular forces. This review highlights the merits and demerits of these soft polymer-based techniques for measuring cellular contraction force with emphasis on their quantitativeness and cell-friendliness. Moreover, how the viscoelastic properties of soft polymers influence the force measurement is addressed. More importantly, the future trends and advancements of soft polymer-based techniques, such as new designs and fabrication processes for cellular force sensing, are also addressed in this review. View Full-Tex

Collagen matrix stiffness influences on fibroblast contraction force

Cell-embedded hydrogel has been widely used as engineered tissue equivalents in biomedical applications. In this study, contraction force in human aortic adventitial fibroblasts seeded within a 3D collagen matrix was quantified by a novel force sensing technique. We demonstrate that contraction forces in cells treated with histamine are regulated by the gel stiffness in a linear manner. These findings provide novel insights for the design of collagen-based biomaterials for tissue engineering and clinical applications

Effects of varying acupuncture manipulations at ST36 (Zusanli) on gastric electrical frequency and amplitude in bradygastria rabbits

Objective. To observe the effects of different manual acupuncture (MA) manipulation on gastric electrical amplitude and frequency for noradrenaline-induced bradygastria in rabbits. Methods. A total of 60 rabbits were randomly allocated into six groups: four MA manipulation groups; reinforcing by twisting the manipulation group (FTG), reducing by twisting the manipulation group (RTG), reinforcing by lifting and thrusting the manipulation group (FLG), and reducing by lifting and thrusting the manipulation group (RLG), a control group (CG), and a model group (MG). The total treatment time length was 45 minutes. The bradygastria was induced via administration of noradrenaline via the marginal ear vein of the rabbits at 5 minutes from baseline, and the bradygastria model was established at 12 minutes from baseline. The rabbits in the four MA manipulation groups received different stimulation parameters at ST36 (Zusanli) for a duration of 3 minutes in accordance with their respective group allocation. The needles were then retained without further manipulation for a further 25 minutes. Gastric electrical amplitude and frequency were recorded using a data acquisition system (Biopac System MP150) at five different time points: baseline (for a duration of 5 minutes), after the bradygastria model was established at 12 minutes from baseline (for a duration of 5 minutes), during MA manipulation commencing at 17 minutes from baseline (for a duration of 3 minutes), 5 minutes after MA manipulation at 25 minutes from baseline (for a duration of 5 minutes), and at 20 minutes following MA manipulation at 40 minutes from baseline (for a duration of 5 minutes). Results. After noradrenaline induction, gastric electrical frequency levels in MA and MG groups were significantly decreased compared to the CG group (P 0.05). During MA manipulation, gastric electrical frequency levels in RTG, FLG, and RLG groups were higher than in the MG group (P < 0.05). At 5 minutes after MA manipulation, gastric electrical frequency levels in RTG and FLG groups were higher than in the MG group (P < 0.05), and gastric electrical frequency level in the RTG group was higher than in the CG group (P < 0.05). At 20 minutes after MA manipulation, gastric electrical frequency levels in FTG, RTG, and FLG groups were higher than in the MG group (P < 0.05). Conclusion. All four variations of MA manipulations have a recovery effect on the gastric electrical frequency of rabbits with bradygastria. In particular, results indicated that FTG, RTG, and FLG at ST36 may have a regular and significant recovery trend through the whole process of the acupuncture intervention

Influence of cell number and collagen concentration on the mechanical behaviour of collagen hydrogel constructs [Abstracts]

Influence of cell number and collagen concentration on the mechanical behaviour of collagen hydrogel constructs [Abstracts

Administration of a Decoction of Sucrose- and Polysaccharide-Rich Radix Astragali (Huang Qi) Ameliorated Insulin Resistance and Fatty Liver but Affected Beta-Cell Function in Type 2 Diabetic Rats

The current investigation attempted to confirm the beneficial actions of a chemically characterized Radix Astragali decoction (AM-W) against type 2 diabetic (T2D) Sprague-Dawley (SD) rats. Using a case/control design, after 2 months of treatment with AM-W (500 mg/kg, daily i.p.) in T2D rats therapeutic outcomes were compared. Sucrose and Astragalus polysaccharides (ASPs) were shown to exist in nearly equal proportions in AM-W. Body weight loss, an improvement in insulin sensitivity, and an attenuation of fatty liver after AM-W administration in T2D rats were evident. Surprisingly, blood sugar, beta-cell function, and glucose tolerance in T2D rats did not improve with AM-W treatment. Further investigation indicated the deleterious effects of the addition of sucrose (100 and 500 μg/mL) and APSs (500 μg/mL) on glucose-stimulated insulin secretion and viability, respectively. In conclusion, a proper administration dosage and a reduction in the sucrose content are keys to maximizing the merits of this herb

Ageing modulates human dermal fibroblast contractility : quantification using nano-biomechanical testing

Dermal fibroblasts play a key role in maintaining homoeostasis and functionality of the skin. Their contractility plays a role in changes observed during ageing, especially in processes such as wound healing, inflammation, wrinkling and scar tissue formation as well as structural changes on extracellular matrix. Although alternations in skin physiology and morphology have been previously described, there remains a paucity of information about the influence of chronological ageing on dermal fibroblast contractility. In this study, we applied a novel nano-biomechanical technique on cell-embedded collagen hydrogels in combination with mathematical modelling and numerical simulation to measure contraction forces of normal human dermal fibroblasts (NHDF). We achieved quantitative differentiation of the contractility of cells derived from ‘young’ ( 60 years old) donors. Transforming growth factor β1 (TGF-β1) was used to stimulate the fibroblasts to assess their contractile potential. NHDF from aged donors exhibited a greater basal contractile force, while in contrast, NHDF from young donors have shown a significantly larger contractile force in response to TGF-β1 treatment. These findings validate our nano-biomechanical measurement technique and provide new insights for considering NHDF contractility in regenerative medicine and as a biomarker of dermal ageing processes

Enhanced plasmonic biosensor utilizing paired antibody and label-free Fe3O4 nanoparticles for highly sensitive and selective detection of Parkinson’s α-synuclein in serum

Parkinson’s disease (PD) is an acute and progressive neurodegenerative disorder, and diagnosis of the disease at its earliest stage is of paramount importance to improve the life expectancy of patients. α-Synuclein (α-syn) is a potential biomarker for the early diagnosis of PD, and there is a great need to develop a biosensing platform that precisely detects α-syn in human body fluids. Herein, we developed a surface plasmon resonance (SPR) biosensor based on the label-free iron oxide nanoparticles (Fe3O4 NPs) and paired antibody for the highly sensitive and selective detection of α-syn in serum samples. The sensitivity of the SPR platform is enhanced significantly by directly depositing Fe3O4 NPs on the Au surface at a high density to increase the decay length of the evanescent field on the Au film. Moreover, the utilization of rabbit-type monoclonal antibody (α-syn-RmAb) immobilized on Au films allows the SPR platform to have a high affinity-selectivity binding performance compared to mouse-type monoclonal antibodies as a common bioreceptor for capturing α-syn molecules. As a result, the current platform has a detection limit of 5.6 fg/mL, which is 20,000-fold lower than that of commercial ELISA. The improved sensor chip can also be easily regenerated to repeat the α-syn measurement with the same sensitivity. Furthermore, the SPR sensor was applied to the direct analysis of α-syn in serum samples. By using a format of paired α-syn-RmAb, the SPR sensor provides a recovery rate in the range from 94.5% to 104.3% to detect the α-syn in diluted serum samples precisely. This work demonstrates a highly sensitive and selective quantification approach to detect α-syn in human biofluids and paves the way for the future development in the early diagnosis of PD