Microchip based on 3D printing technology for simulating intestinal villi and tumor surface topography / 上海交通大学学报（医学版）

Objective: To propose a method for making organ-on-a-chip based on 3D printing, and study the relationship between cell growth on the chips and various factors. Methods: Through 3D printing technology and surface microstructure transfer method, ulcer-like and ridge-like mi-crostructures of the tumor surface and the intestinal villi were fabricated on a polydimethylsiloxane (PDMS) chip. Combined with fluorescence imaging, the effects of surface modification, shapes and heights of microstructures, and culture time on the surface coverage and density of Caco-2 cells on the chip were measured. Results:The PDMS chip was more likely to induce cell adhesion and growth rather than the 3D printing resin chip. On the surface of three-dimensional structure, cell surface coverage and cell density increased after the surface was treated with rat tail collagen (P0.05). Conclusion: The intestinal villi and tumor topological organ chips can be fabricated by 3D printing technology and surface microstructure transfer method. The surface modification and microstructure height affect the cell growth on the surface.

Preparation of Silver Nanowires Flexible Electrode for Electrochemical Detection of Trace Copper in Water / 分析化学

A silver nanowires(AgNWs) flexible electrode was prepared using polydimethylsiloxane (PDMS) as the substrate and AgNWs as the conductive layer. It is easier to change the shapes and sizes of the flexible electrode due to its excellent stretchability and foldability. A square wave stripping voltammetry (SWSV) method for the detection of trace copper in water was established using the electrode as the working electrode.The characterization of AgNWs flexible electrode showed that the spread of AgNWs was uniform and the average resistance was 1.03 Ω. The data of electrochemical analysis showed that the properties of the electrode were superior to commercialized gold electrode and silver electrode. The effects of Bi3+concentration, supporting electrolyte,pH value, enrichment potential and enrichment time were determined and optimized. We achieved the sharpest and highest peak of the SWSV curves for the detection of Cu2+in the range of-0.3-0.3 V,which means the most sensitive detection, under the following conditions such as 0.5 mg/L Bi3+,0.1 mol/L support electrolyte tartaric acid-sodium tartrate solution (pH, 4.8), 0.6 V of enrichment potential, and 600 s of enrichment time. Under such conditions, the linear detection range of Cu2+concentration was from 0.001 mg/L to 0.100 mg/L and the detection limit was 9.27×10-5mg/L. The advantages of this detection method are fast speed,high sensitivity and wide detection range. Therefore,it can not only meet the requirements for the copper ion detection but also provide a new method or experimental basis for the detection of other metal ions in water. In addition, the AgNWs flexible electrode has great potential in detections under special circumstances or instantaneous detections due to its wonderful flexibility and biocompatibility.

Experimental implantation of an arterial substitute made of silicone reinforced with polyester fabric in rabbits

OBJECTIVES: The aim of this study was to analyze silicone tubes with an internal diameter of 4 mm as a possible material for vascular prostheses. METHODS: Grafts were implanted into the infrarenal aortas of 33 rabbits. Fluoroscopic examinations were performed within 150 days after surgical implantation. Sample grafts were analyzed via electron microscopy to evaluate the eventual endothelialization of the prostheses. RESULTS: The patency rates of the prostheses were 87% (±6.7%) after 30 days, 73% (±9.3%) after 60 days and 48% (±12%) after 120 days. The material presented characteristics that support surgical implantation: good tolerance promoted by polyester tear reinforcement, ease of postoperative removal and a lack of pseudoaneurysms. However, intimal hyperplasia was a limiting factor for the patency rate. CONCLUSIONS: We concluded that polydimethylsiloxane has limited potential as an alternative material for small vascular prostheses.

Effect of polydimethylsiloxane matrix elasticity on osteogenic differentiation of rat marrow stromal cells / 中华口腔医学杂志

Objective@#To investigate the effect of polydimethylsiloxane (PDMS) matrix elasticity on osteogenic differentiation of rat marrow stromal cells (rBMSC).@*Methods@#A series of PDMS composite substrates with different elastic modulus were constructed by adjusting the relative concentrations of cross-linking agent. The Young's modulus was used to describe the elasticity of PDMS after measurement by atomic force microscope (AFM). After surface modification, rBMSC was seeded on PDMS matrix, and 7 days after rBMSC was cultured on the five different Young's moduli matrix, the differences of osteogenic differentiation of rBMSC were observed by the method of real-time PCR, Western blotting, and alkaline phosphatase assay.@*Results@#The PDMS was suitable for cell culture after surface modification, and by altering the concentration of cross-linking agent, PDMS could mimic the majority of the tissues' elasticity in vivo. The related osteogenic differentiation markers expression showed significant difference between the five matrixes (P<0.05), including type Ⅰ collagen (Col-Ⅰ), osteocalcin (OCN), osteopontin (OPN) and bone morphogenetic protein 2 (BMP2). The expression of osteogenic markers was up-regulated in the group that the Young's modulus was (354.1±40.9) kPa (P<0.05).@*Conclusions@#PDMS is a tunable elasticity matrix which could be used in the investigation of inducing rBMSCs into osteoblastic lineages. PDMS substrate stiffness has an obvious influence on rBMSC osteogenic differentiation.

Design and Validation of a Microfluidic Chip with Micropillar Arrays for Three-dimensional Cell Culture / 分析化学

A microfluidic chip with micropillar arrays for three-dimensional (3D) cell culture was designed and validated.The chip consisted of a polydimethylsiloxane (PDMS) channel plate and a glass cover plate.One cell culture chamber composed of two rows of micropillar arrays and two lateral channels for transporting the culture medium were integrated on the PDMS channel plate.The spacing between micropillars directly affects the chip performance, which is critical for the design of the chip.In this work, the spacing between micropillars was optimized by numerical simulation and experimental validation.With the optimized microfluidic chip, the mixture of cells and extracellular matrix mimics could be steadily injected into the cell culture chamber, the nutrients in the culture medium from the lateral channels could quickly diffuse into the chamber, and the cell metabolites could also timely diffuse out of the chamber.To test the stability of the microenvironment in the microfluidic chip, neural stem cells were three-dimensionally cultured.

Highly Efficient Reprogramming and Characterization of Induced Pluripotent Stem Cells by Using a Microwell Array

Reprogramming of human somatic cells to induced pluripotent stem cells (iPSCs) enables the possibility of generating patient-specific cells. However, the low efficiency issue associated with iPSCs generation has limited iPSCs usage in research and clinical applications. In this study, we developed a high efficiency system to generate iPSCs by using a polydimethylsiloxane stencil. This device could be applied to the localization and reprogramming of human fibroblasts. Herein, a well-defined culture system based on a stencil, which supported efficient reprogramming of fibroblasts into iPSCs with 2–4 fold increase in efficacy over conventional methods, is presented. Subsequently, we prepared a multiple analysis system, which used a micro-patterned scissile microarray to characterize iPSCs. The results showed that iPSCs could be cultured into micro-patterns in a precisely controlled manner on the scissile poly(ethylene terephthalate) sheet, which was cut into pieces for subsequent analyses, indicating that this method allows multiple analyses to establish iPSC pluripotency in the same sample. Our approach provides a simple, cost-effective, but highly efficient system for the generation and characterization of iPSCs, and will serve as a powerful tool for establishing patient- and disease-specific pluripotent stem cells.

A Microfluidic Chip with Integrated Microelectrode for Real-time Dopamine Detection / 分析化学

A microfluidic chip with integrated microelectrode for real-time dopamine detection was designed and fabricated. The chip consisted of a polydimethylsiloxane ( PDMS) channel plate and a glass electrode plate. One central channel as the culture chamber of neural stem cells and two lateral channels for transport of the culture medium were integrated on the PDMS channel plate. Microelectrodes for real-time dopamine detection were integrated on the glass electrode plate. To solve the problem in demoulding the PDMS channel plate from the silicon mould, a novel demoulding method was developed. An Au-Au-Au three-electrode system was constructed, and it performed well in electrochemical detection. The performance of the microfluidic chip was primarily studied by detecting dopamine dissolved in the medium for the culture of neural stem cells. The limit of detection was 3. 92 μmol/L, the linear detection range was from 10 μmol/L to 500 μmol/L, and the detection reproducibility from different chips was less than 4%.

A new method for establishing temperature gradient field in micro-channel on glass-PDMS microfluidic chip and for investigating thermal biological effect of cells / 军事医学

Objective To develop a new method for establishing a temperature gradient field in the microchannel on a glass-polydimethylsiloxane ( PDMS ) microfluidic chip and to verify its applicability in the study of cellular thermal biological effect.Methods The establishment and control of the temperature gradient field in the microchannel were implemented by a peripheral indium tin oxide ( ITO) heater and a heating micro-wire embedded in the PDMS chip.The temperature gradient field established in the microchannel was represented by the finite element numerical analysis and temperature-dependent fluorescent dye rhodamine B.Finally, the thermal biological effect, which used cell survival rate of human prostate cancer cells T24 as an indicator, was investigated in the microchannel.Results The results of finite element numerical analysis proved that this method established a temperature gradient field along the length of the microchannel successfully.The distribution range of the temperature gradient field was controlled by the ITO heater, while the gradient of the temperature gradient field was controlled by the heating micro-wire.The measurement result of rhodamine B was identical with the result of the finite element numerical analysis.The thermal biological effect of T24 tumor cell research showed that the cell survival rate decreased with the rise of the regional temperature in the microchannel.Conclusion The method developed in this paper for establishing a temperature gradient field in the microchannel on a glass-PDMS microfluidic chip is simple and easy to implement, and it can be used for parallel study of the cellular thermal biological effect on the microfluidic chip in the future.

An ex vivo evaluation of the sealing ability of polydimethylsiloxane-based root canal sealers.

Aim: The aim was to study the sealing efficacy of polydimethylsiloxane‑based root canal sealers. Materials and Methods: Polydimethylsiloxane‑based root canal sealers were reviewed and subjected to an ex vivo study. A total of 60 extracted maxillary incisors were included in this study, which was conducted under two groups, Groups A and B, of 30 teeth each. In Group A, GuttaFlow and in Group B, RoekoSeal as sealers were used for obturation with Gutta‑percha cones after preparing canal with a step back technique. The criterion for evaluating sealing efficacy of the sealers was light absorption by spectrophotometer. The collected data were analyzed statistically using one‑way ANOVA test. Results: The findings of the study revealed that the mean leakage in Group B (0.1027) was significantly less than Group A (0.1649) (P < 0.001). RoekoSeal showed superior sealing ability. Conclusion: RoekoSeal had the better sealing ability than GuttaFlow and may be recommended for clinical use.

Experience of Subureteral Polydimethylsiloxane Injection Treatment in Children with Vesicoureteral Reflux / 대한비뇨기과학회지

PURPOSE: Our data was retrospectively reviewed to assess the efficacy, safety and costs of endoscopic subureteral polydimethylsiloxane (PDS, Macroplastique(R)) injection treatment for children with vesicoureteral reflux (VUR). MATERIALS AND METHODS: Between December 1997 and May 2006, a total of 24 (29 renal units) VUR patients, whose parents showed reluctance toward open surgery, underwent subureteral PDS injection treatment. All of the patients were postoperatively assessed by voiding cystourethrography (VCUG) and ultrasound to evaluate any complications and reflux. The medical costs of the injection treatment were compared with those of open surgery for VUR over the same period. RESULTS: The mean follow-up was 15 months (range 2-72). Of the 29 renal units treated, 24 (82.8%) were cured. Hydronephrosis, which postoperatively developed in three renal units, was spontaneously improved or resolved after minimal endourological procedures. Temporary gross hematuria and voiding difficulty occurred in one patient each, but were also improved. The total medical costs of the injection treatment were cheaper than those of open surgery (p<0.05). CONCLUSIONS: An endoscopic subureteral PDS injection is an effective and safe procedure; in addition, compared to open surgery, is an economic treatment for children with VUR.

The Early Experience and Technical Aspects of Endoscopic Subureteral Polydimethylsiloxane Injection for Vesicoureteral Reflux / 대한비뇨기과학회지

PURPOSE: We reviewed the operative outcome and the cause of failure for performing subureteral injection of polydimethylsiloxane (PDS, Macroplastique(R), Uroplasty Inc. Geleen, The Netherlands), when it is used as a bulking agent for the endoscopic treatment of vesicoureteral reflux (VUR) patients. MATERIALS AND METHODS: A total of 29 patients (a total of 37 ureters), with primary grades I to V VUR were treated with a single subureteral injection from 2001 to 2004; these patients were followed for an average of 21.5 months. Each patient underwent preoperative voiding cystourethrography, renal ultrasound, a dimercapto-succinic acid (DMSA) scan and urine culture. With the patient under general anesthesia, the PDS implant was injected transurethrally at the 6 o'clock position of the ureteral opening in the affected renal unit by a modified subureteral transurethral injection (STING) procedure. Renal ultrasound was done at 1 week and voiding cystourethrography was done at 3 months to rule out obstruction at the injection site and/or persistent reflux, respectively. Cure was defined as an absence of VUR on voiding cystourethrography at 3 months after injection. Statistical analyses were performed using the chi-square test. RESULTS: The grade of reflux was I, II, III, IV and V in 6, 4, 12, 9 and 6 ureteral units respectively. After a single injection, the VUR was cured in 30 ureteral units (81.1%). There were 7 (18.9%) patients who received a second injection after a failed single injection. In these patients, the injected PDS volume was not changed on ultrasound. On the other hand, cystoscopy showed mound displacement in 4 patients, no volcano appearance but rather a broad elevation in 2 patient, and distal ureteral fistula and mound extrusion in 1 patient. CONCLUSIONS: These results suggest that endoscopic subureteral polydimethylsiloxane injection is an effective treatment of VUR. The efficacy of subureteral injection can be improved by using the correct injection technique.

An Experience of Endoscopic Polydimethylsiloxane Injection for the Treatment of Vesicoureteral Reflux in Children / 대한비뇨기과학회지

PURPOSE: We evaluated the efficacy of an endoscopic subureteral injection of polydimethylsiloxane (Macroplastique) for the correction of vesicoureteral reflux in children. MATERIALS AND METHODS: The medical records of 15 children (19 refluxing ureters), who had undergone a single endoscopic subureteral injection of polydimethylsiloxane for the treatment of vesicoureteral reflux, were reviewed. After the injection, voiding cystourethrograms were performed after 3 to 10 months to evaluate the results. Renal and bladder ultrasonograms were taken after 3 to 30 months to check for the development of de novo hydroureteronephrosis and the presence of the implant at the bladder base. The follow-up duration was between 7 and 43 months. RESULTS: Of the 15 patients, there were 6 boys and 9 girls, with ages ranging from 12 months to 14 years. The reflux was resolved in 10 of the 19 ureters, in 8 of the 15 children, after a single injection. The resolutions of reflux, by grade, were none in 2, 2 in 4, 5 in 7, 1 in 4 and 2 in 2 of the ureters of grade I to V, respectively. The unilateral reflux was resolved in 7 of the 12, the bilateral reflux in 2 (3 ureters) of the 3 and the reflux in a duplicated system in 1 of the 3 cases (2 ureters out of 4 ureters). In two cases with persistent reflux, ureteral reimplantations were performed due to repeated urinary tract infections and de novo upper pole ureteral refluxes. The remaining 5 cases with persistent reflux were observed with prophylactic antibiotics. Refluxes recurred in 2 of the ureters at 29 and 36 months after the injection, so chemoprophylaxis was restarted. CONCLUSIONS: The single endoscopic subureteral polydimethylsiloxane injections resulted in a low success rate, but at a high cost. This procedure is considered inappropriate as a first line method for the correction of vesicoureteral reflux in children.

Micropatterning of endothelial cells on poly-dimethylsiloxane flow channel bottom / 第三军医大学学报

Objective To simulate the blood flow features of the susceptible sites of atherosclerosis in vitro.The cell micro-patterning is to be obtained on the bottom of channel for the information about single cell or cell groups.Methods Poly-dimethylsiloxane(PDMS) flow channel and PDMS stamp were fabricated by soft lithography.Fibronectin pattern was formed on chamber bottom by micro-contact printing method and cells selectively attached on fibronectin pattern.Results The PDMS-patterned chamber that possessed favorable optical property and the PDMS stamps with different sizes were obtained.Cells attached on fibronectin pattern presented square array.Conclusion The fabricated methods are quick and simple.The chamber could be used for the advanced real-time investigation of cell mechanical behavior in vitro.