Cell Electrical Impedance as a Novel Approach for Studies on Senescence Not Based on Biomarkers.

Senescence of cardiac myocytes is frequently associated with heart diseases. To analyze senescence in cardiac myocytes, a number of biomarkers have been isolated. However, due to the complex nature of senescence, multiple markers are required for a single assay to accurately depict complex physiological changes associated with senescence. In single cells, changes in both cytoplasm and cell membrane during senescence can affect the changes in electrical impedance. Based on this phenomenon, we developed MEDoS, a novel microelectrochemical impedance spectroscopy for diagnosis of senescence, which allows us to precisely measure quantitative changes in electrical properties of aging cells. Using cardiac myocytes isolated from 3-, 6-, and 18-month-old isogenic zebrafish, we examined the efficacy of MEDoS and showed that MEDoS can identify discernible changes in electrical impedance. Taken together, our data demonstrated that electrical impedance in cells at different ages is distinct with quantitative values; these results were comparable with previously reported ones. Therefore, we propose that MEDoS be used as a new biomarker-independent methodology to obtain quantitative data on the biological senescence status of individual cells.

Microelectrical Impedance Spectroscopy for the Differentiation between Normal and Cancerous Human Urothelial Cell Lines: Real-Time Electrical Impedance Measurement at an Optimal Frequency.

PURPOSE: To distinguish between normal (SV-HUC-1) and cancerous (TCCSUP) human urothelial cell lines using microelectrical impedance spectroscopy (µEIS). MATERIALS AND METHODS: Two types of µEIS devices were designed and used in combination to measure the impedance of SV-HUC-1 and TCCSUP cells flowing through the channels of the devices. The first device (µEIS-OF) was designed to determine the optimal frequency at which the impedance of two cell lines is most distinguishable. The µEIS-OF trapped the flowing cells and measured their impedance at a frequency ranging from 5 kHz to 1 MHz. The second device (µEIS-RT) was designed for real-time impedance measurement of the cells at the optimal frequency. The impedance was measured instantaneously as the cells passed the sensing electrodes of µEIS-RT. RESULTS: The optimal frequency, which maximized the average difference of the amplitude and phase angle between the two cell lines (p < 0.001), was determined to be 119 kHz. The real-time impedance of the cell lines was measured at 119 kHz; the two cell lines differed significantly in terms of amplitude and phase angle (p < 0.001). CONCLUSION: The µEIS-RT can discriminate SV-HUC-1 and TCCSUP cells by measuring the impedance at the optimal frequency determined by the µEIS-OF.

Polymeric check valve with an elevated pedestal for precise cracking pressure in a glaucoma drainage device.

This paper presents the design, fabrication, and characterization of a polymeric micro check valve for a glaucoma drainage device (GDD) featuring the precise regulation of intraocular pressure (IOP) and effective aqueous humor turnover (AHT). The pedestal, slightly elevated by selective coating of a parylene C film, induces pre-stress in the thin valve membrane, which enhances the predictability of the cracking pressure of the GDD. The proposed GDD comprises a cannula and a normally closed polymeric micro check valve, which are made of PDMS, a biocompatible polymer, with three layers: top (cover), intermediate (thin valve membrane), and bottom (base plate). A feedback channel, located between the top and intermediate layers, prevents reverse flow by feeding the pressure of the outlet channel back to the thin valve membrane. To achieve a precise cracking pressure and sufficient drainage of humor for humans, the thicknesses of the valve membrane and parylene C film are designed to be 58 µm and 1 µm, respectively, which are confirmed using a COMSOL simulation. The experimental results show that the cracking pressure of the fabricated GDD lies within the range of normal IOP (1.33-2.67 kPa). The forward flow rate (drainage rate), 4.3 ± 0.9 µL/min at 2.5 kPa, is adequate to accommodate the rate of AHT in a normal human eye (2.4 ± 0.6 µL/min). The reverse flow was not observed when a hydrostatic pressure of up to 4 kPa was applied to the outlet and the feedback channel.

Evaluation of a Polymeric Flap Valve-Attached Ureteral Stent for Preventing Vesicoureteral Reflux in Elevated Intravesical Pressure Conditions: A Pilot Study Using a Porcine Model.

OBJECTIVE: To evaluate the effectiveness of a polymeric flap valve-attached ureteral stent for preventing vesicoureteral reflux (VUR) in an animal model. MATERIALS AND METHODS: One female Yorkshire pig was included in this study. A flap valve-attached and a conventional stent was inserted in the right and left ureters, respectively. The bladder was filled with contrast medium until the intravesical pressure reached 20 cm H2O. Subsequently, simulated voiding cystourethrography (VCUG) was performed 50 times by manually compressing the suprapubic area until the intravesical pressure reached 50 cm H2O. Intravenous pyelography (IVP) was performed thereafter to evaluate the urinary drainage. In addition, an in vitro durability test of the function of the flap valve was conducted under continuous hydrostatic pressure for 24 h. RESULTS: The volume of contrast medium needed to achieve an intravesical pressure of 20 cm H2O was 1740 mL. In the repeated simulated VCUG for the right ureter, VUR grades of 0 and I were recorded in 82.0 (n = 41) and 18.0% (n = 9) tests, respectively, whereas for the left ureter, grades of I, II, and III were recorded in 14.0 (n = 7), 82.0 (n = 41), and 4.0% (n = 2), respectively. Thus, a significantly lower VUR grade was recorded for the right ureter than for the left ureter (p < 0.001). In the bilateral VUR condition, the pressure for VUR occurrence was significantly greater in the right ureter than in the left ureter (p = 0.007). No urinary obstruction was caused by the flap valve-attached ureteral stent according to the IVP findings. The in vitro durability test demonstrated slightly enhanced antireflux function and slightly decreased intraluminal drainage at 12 h, and these findings sustained thereafter. CONCLUSION: A flap valve-attached ureteral stent effectively prevented VUR under conditions of elevated intravesical pressure without urinary obstruction.

Anti-Reflux Ureteral Stent with Polymeric Flap Valve Using Three-Dimensional Printing: An In Vitro Study.

PURPOSE: This article aims to describe the design of an anti-reflux ureteral stent with a polymeric flap valve and the fabrication methods using three-dimensional (3D) printing. The stent effectively prevents backward flow with a negligible reduction in forward flow. Fabrication of miniaturized valves was easy with high precision and rapid prototyping. MATERIALS AND METHODS: The proposed stent comprised a 7F Double-J (DJ) stent and a polymeric flap valve. The valve was made of Tango Plus FLX980 and was fabricated using a 3D printer. Two types of stent were prepared for in vitro tests: DJ stents with (1) an uncoated valve (UCV) stent and (2) a parylene C coated valve (PCV) stent for enhanced biocompatibility. The flow characteristics of each stent were evaluated considering flow direction, parylene coating, and stent side holes, and were compared to the intact DJ stent. RESULTS: The forward flow rate for the distal portion of the UCV and PCV stents was 9.8 mL/min and 7.8 mL/min at applied pressure of 15 cm H2O (normal anterograde pressure in patients with stents), respectively. Backward flow rate for the distal portion of the UCV and PCV stents was decreased by 28 times and 8 times at applied pressure of 50 cm H2O (maximum bladder pressure), respectively, compared with the distal portion of the intact DJ stent. Forward flow rates of whole stents were 22.2 mL/min (UCV stent) and 20.0 mL/min (PCV stent) at applied pressure of 15 cm H2O, and backward flow rates of whole UCV and PCV stents were decreased by 8.3 times and 4.0 times at applied pressure of 50 cm H2O, respectively, compared with the intact DJ stent. CONCLUSIONS: The anti-reflux ureteral stent was successfully designed and fabricated using a 3D printer. In vitro studies showed that the stent effectively prevented backward flow while minimizing reduction in forward flow.

Selectively bonded polymeric glaucoma drainage device for reliable regulation of intraocular pressure.

A novel glaucoma drainage device (GDD) using a polymeric micro check valve with no reverse flow is presented for the effective regulation of intraocular pressure (IOP). A significant functional improvement was achieved by reducing the possible incidence of hypotony, as the proposed GDD only drains aqueous humor at a certain cracking pressure or higher. The device consists of three biocompatible polymer layers: a top layer (cover), an intermediate layer (membrane), and a bottom layer (base plate with a cannula). All three layers, made of soft polydimethylsiloxane (PDMS), were bonded together to realize the thin GDDs. The bottom layer was selectively coated with chromium (Cr)/gold (Au) to prevent stiction between the valve seat and the valve orifice so that the device could show enhanced reliability in operation and high yield in production. Two types of polymeric devices were fabricated; one was a glaucoma drainage device for humans (GDDH) and the other was a glaucoma drainage device for animals (GDDA). From subsequent in vitro tests, the cracking pressures were 18.33 ± 0.66 mmHg (mean ± standard deviation) for GDDH and 12.42 mmHg for GDDA, both of which were very close to the corresponding normal IOPs. From in vivo tests of GDDA, the IOP of all implanted devices was properly regulated within the target pressure (10-15 mmHg). The experimental results showed that the proposed polymeric GDD has high potential for use in the treatment of glaucoma disease in terms of its repeatability of the cracking pressure and patients' relief from post-operative discomfort.