Reversing current rectification to improve DNA-sensing sensitivity in conical nanopores.

Herein, we report the ultrasensitive DNA detection through designing an elegant nanopore biosensor as the first case to realize the reversal of current rectification direction for sensing. Attributed to the unique asymmetric structure, the glass conical nanopore exhibits the sensitive response to the surface charge, which can be facilely monitored by ion current rectification curves. In our design, an enzymatic cleavage reaction was employed to alter the surface charge of the nanopore for DNA sensing. The measured ion current rectification was strongly responsive to DNA concentrations, even reaching to the reversed status from the negative ratio (-6.5) to the positive ratio (+16.1). The detectable concentration for DNA was as low as 0.1 fM. This is an ultrasensitive and label-free DNA sensing approach, based on the rectification direction-reversed amplification in a single glass conical nanopore.

Targeted disruption of the spermatid-specific gene Spata31 causes male infertility.

Spata31, a novel testis-specific gene, was first isolated from the testis of a vitamin A-deficient rat model. To gain insight into its physiological function, Spata31-targeted knockout mice were generated by homologous recombination. Spata31-deficient (Spata31(flox/flox) ; Vasa-Cre) male mice exhibited low sperm count and premature shedding of germ cells into the lumen, ultimately causing azoospermia and male sterility. Mechanistically, the Spata31 deficiency resulted in reduced expression of the adhesion protein nectin-3 and cytoskeletal protein ß-actin at the apical ectoplasmic specialization. Our findings demonstrate that the disruptions to the SPATA31 ortholog could be linked to human male infertility.

Smart Nano-switch with Flexible Modulation of Ion Transport Using Multiple Environmental Stimuli.

In this work, we demonstrate a unique nano-switch with triple environmental stimuli based on the action of functional copolymer brushes in a single conical nanochannel. This nanodevice flexibly and efficiently modulates ion transport properties under the influence of three environmental stimuli: light, pH and temperature. The triple factors can not only play a regulatory role independently, but their synergistic cooperation could fully activate the ionic gate and reversibly control the gating direction. In addition, the nano-switch can switch transport properties on demand in the face of complex combinations of different factors. This work promotes the development of intelligent bionic ion channels, which holds promise for biosensing, energy conversion and biomedical research.

Smart pH-Modulated Two-Way Photoswitch Based on a Polymer-Modified Single Nanochannel.

In this article, we have demonstrated a smart pH-modulated two-way photoswitch that can reversibly switch ion transport under alternating light exposure over a wide pH range. This photoswitch was prepared by functionalizing the interior of a single conical glass nanochannel with a poly-spiropyran-linked methacrylate (P-SPMA) polymer through surface-initiated atom transfer radical polymerization. The P-SPMA polymer brushes comprise functional groups that are responsive to light and pH, which can cause configuration and charge changes to affect the properties of the nanochannel wall. The SPMA polymer-modified nanochannel not only reversibly controlled ion transport under alternating light irradiation but also efficiently and flexibly regulated the direction and extent of the ion transport based on the pH. This two-way photoswitch exhibits the considerable potential of photoresponsive polymers for the advancement of "intelligent" bionic nanochannel devices for ion screening and optical sensing in various applications.

Encapsulated three-dimensional bioprinted structure seeded with urothelial cells: a new construction technique for tissue-engineered urinary tract patch.

BACKGROUND: Traditional tissue engineering methods to fabricate urinary tract patch have some drawbacks such as compromised cell viability and uneven cell distribution within scaffold. In this study, we combined three-dimensional (3D) bioprinting and tissue engineering method to form a tissue-engineered urinary tract patch, which could be employed for the application on Beagles urinary tract defect mode to verify its effectiveness on urinary tract reconstruction. METHODS: Human adipose-derived stem cells (hADSCs) were dropped into smooth muscle differentiation medium to generate induced microtissues (ID-MTs), flow cytometry was utilized to detect the positive percentage for CD44, CD105, CD45, and CD34 of hADSCs. Expression of vascular endothelial growth factor A (VEGFA) and tumor necrosis factor-stimulated gene-6 (TSG-6) in hADSCs and MTs were identified by Western blotting. Then the ID-MTs were employed for 3D bioprinting. The bioprinted structure was encapsulated by transplantation into the subcutaneous tissue of nude mice for 1 week. After retrieval of the encapsulated structure, hematoxylin and eosin and Masson's trichrome staining were performed to demonstrate the morphology and reveal collagen and smooth muscle fibers, integral optical density (IOD) and area of interest were calculated for further semi-quantitative analysis. Immunofluorescent double staining of CD31 and α-smooth muscle actin (α-SMA) were used to reveal vascularization of the encapsulated structure. Immunohistochemistry was performed to evaluate the expression of interleukin-2 (IL-2), α-SMA, and smoothelin of the MTs in the implanted structure. Afterward, the encapsulated structure was seeded with human urothelial cells. Immunofluorescent staining of cytokeratins AE1/AE3 was applied to inspect the morphology of seeded encapsulated structure. RESULTS: The semi-quantitative assay showed that the relative protein expression of VEGFA was 0.355 ±â€Š0.038 in the hADSCs vs. 0.649 ±â€Š0.150 in the MTs (t = 3.291, P = 0.030), while TSG-6 expression was 0.492 ±â€Š0.092 in the hADSCs vs. 1.256 ±â€Š0.401 in the MTs (t = 3.216, P = 0.032). The semi-quantitative analysis showed that the mean IOD of IL-2 in the MT group was 7.67 ±â€Š1.26, while 12.6 ±â€Š4.79 in the hADSCs group, but semi-quantitative analysis showed that there was no statistical significance in the difference between the two groups (t = 1.724, P = 0.16). The semi-quantitative analysis showed that IOD was 71.7 ±â€Š14.2 in non-induced MTs (NI-MTs) vs. 35.7 ±â€Š11.4 in ID-MTs for collagen fibers (t = 3.428, P = 0.027) and 12.8 ±â€Š1.9 in NI-MTs vs. 30.6 ±â€Š8.9 in ID-MTs for smooth muscle fibers (t = 3.369, P = 0.028); furthermore, the mean IOD was 0.0613 ±â€Š0.0172 in ID-MTs vs. 0.0017 ±â€Š0.0009 in NI-MTs for α-SMA (t = 5.994, P = 0.027), while 0.0355 ±â€Š0.0128 in ID-MTs vs. 0.0035 ±â€Š0.0022 in NI-MTs for smoothelin (t = 4.268, P = 0.013), which indicate that 3D bioprinted structure containing ID-MTs could mimic the smooth muscle layer of native urinary tract. After encapsulation of the urinary tract patch for additional cell adhesion, urothelial cells were seeded onto the encapsulated structures, and a monolayer urothelial cell was observed. CONCLUSION: Through 3D bioprinting and tissue engineering methods, we provided a promising way to fabricate tissue-engineered urinary tract patch for further investigation.

Development of a poly-L-lactide salivary duct stent.

Obstructive salivary gland diseases are common conditions that arise following the disruption of the secretary ductal system and usually results in the swelling and pain of the affected gland(s). There has been an increase in the use of sialendoscopy for the treatment and diagnosis of obstructive salivary gland infection. If damage occurs to a duct or papilla following sialendoscopy, a stent may be necessary to prevent restenosis and for maintaining the salivary duct open after complete sialendoscopy. Currently, there are only non-biodegradable salivary duct stents available. The aim of the current study was to establish a methodology for the fabrication of a biodegradable poly-L-lactide (PLLA) salivary duct stent and to examine its function in an animal model. In the current study, PLLA was used to fabricate a salivary duct stent, which was compared with other commercially available non-biodegradable products. The mechanical tests revealed that the tensile strength of the PLLA stent was similar to that of the commercially available non-biodegradable stents. The Young's modulus, which measures the stiffness of a solid material, was significantly higher for the PLLA stent compared with the commercially available non-biodegradable stents. In addition, the current study demonstrated that the PLLA salivary duct stent was easily used with current sialendoscopy techniques, allowing accurate stent placement in an animal model.

Efficient generation of hepatic cells from mesenchymal stromal cells by an innovative bio-microfluidic cell culture device.

BACKGROUND: Mesenchymal stromal cells (MSCs) are multipotent and have great potential in cell therapy. Previously we reported the differentiation potential of human MSCs into hepatocytes in vitro and that these cells can rescue fulminant hepatic failure. However, the conventional static culture method neither maintains growth factors at an optimal level constantly nor removes cellular waste efficiently. In addition, not only is the duration of differentiating hepatocyte lineage cells from MSCs required to improve, but also the need for a large number of hepatocytes for cell therapy has not to date been addressed fully. The purpose of this study is to design and develop an innovative microfluidic device to overcome these shortcomings. METHODS: We designed and fabricated a microfluidic device and a culture system for hepatic differentiation of MSCs using our protocol reported previously. The microfluidic device contains a large culture chamber with a stable uniform flow to allow homogeneous distribution and expansion as well as efficient induction of hepatic differentiation for MSCs. RESULTS: The device enables real-time observation under light microscopy and exhibits a better differentiation efficiency for MSCs compared with conventional static culture. MSCs grown in the microfluidic device showed a higher level of hepatocyte marker gene expression under hepatic induction. Functional analysis of hepatic differentiation demonstrated significantly higher urea production in the microfluidic device after 21 days of hepatic differentiation. CONCLUSIONS: The microfluidic device allows the generation of a large number of MSCs and induces hepatic differentiation of MSCs efficiently. The device can be adapted for scale-up production of hepatic cells from MSCs for cellular therapy.

Study of clinical practical model of urinary system injury.

BACKGROUND: In order to improve the clinical treatment level of urinary system injury, it is necessary to build up an animal model of urinary system wound, which is not only analogous to real clinical practice, but also simple and practical. METHODS: We have developed the third generation of firearm fragment wound generator based on the first and the second producer. The best explosive charge of the blank cartridge was selected by gradient powder loading experiments. The firearm fragment injuries were made to the bulbous urethra of 10 New Zealand male rabbits. One week preoperatively and 2, 4 and 8 weeks postoperatively, all the animals underwent urethroscopy and urethrography. At 2, 4 and 8 weeks postoperatively, two animals were randomly selected and killed, and the urethra was cut off for pathological examination. RESULTS: The shooting distance of the third generation of firearm fragment wound generator is 2 cm. The best explosive charge of the blank cartridge is 1 g of nitrocotton. All rabbits survived the procedures and stayed alive until they were killed. Injuries were limited to bulbous urethra and distal urethra. Round damaged areas, 1-1.5 cm in length, on the ventral wall were observed. Ureteroscopy results showed that canal diameter gradually shrank by over 50% in 9 rabbits. The rate of success was 90%. Urethrography result noted that a 1-1.3 cm stricture was formed at the bulbous urethra. Histology results of injured stricture urethra showed that fibrous connective tissue hyperplasia and hyaline degeneration caused further stricture in the canal. CONCLUSIONS: The third generation of firearm fragment wound generator imitates the bullet firing process and is more accurate and repeatable. The corresponding rabbit model of traumatic complex urethral stricture simulates the real complex clinical conditions. This animal model provides a standardized platform for clinical researches on treating traumatic injuries to the urinary system.