We report a systematic investigation about the mechanism of pH sensing using SnO 2 nanobelt field effect transistors (FETs). The FETs, based on single SnO 2 nanobelts, are channel-limited and with proper contact passivation; the pH sensing was conducted with sodium phosphate solutions through integrated microfluidics. The responses of the FET channel conductance to pH were measured at different gate voltages: a linear pH dependence was observed in the linear transport "on" state, while an exponential dependence was observed in the subthreshold regime. Measurements at the same pH but different ion concentrations demonstrated that the FET's pH sensitivity decreases logarithmically with the ion concentration. The effect of APTES-functionalization was evaluated by comparing the pH responses of the same device with and without the surface modification. The APTES functionalization results in a slight enhancement of the pH sensitivity and a large suppression of the noise level, leading to marked improvement in the signal-to-noise ratio. The results indicate that the pH sensing is based on a screened field-effect response of the FETs to the surface protonation/ deprotonation on the nanobelt. This study provides several useful guidelines for optimizing the sensor performance for chemical and biomolecular detection.There is significant biomedical interest in developing rapid, portable, high-sensitivity pH sensors for very small amount of fluids. For example, the pH values of blood and interstitial *electronic address: xiong@martech.fsu.edu. Figure 1(a)), which makes it possible to independently bias the FET to obtain optimum sensitivity. Second, the absence of a reference electrode which must be electrically connected to the solution could facilitate applications involving minute amount of fluids such as EBC. NIH Public AccessSemiconducting oxide nanobelts, as one type of single-crystalline, uniform and stable Q1D nanostructures, are very attractive for chemical and biosensing applications. Among these binary oxide candidates, SnO 2 has long been a technologically important sensor material 16,17 and has been extensively studied in different forms (powder, 18 thin film, 19, 20 and hybrid 21,22 ) for gas sensing applications. However, to the best of our knowledge, there has been no report on their Q1D nanoscale counterpart for ion and biomolecular detection in aqueous solutions. Here we report the results of a series of pH sensing experiments with back-gated SnO 2 nanobelt FETs. Our devices employ the conventional MOSFET (metal-oxidesemiconductor field-effect transistor) structure. With a back gate and passivated source/drain electrodes, only the nanobelt channel is exposed to the solution.The catalyst-free synthesis of the oxide nanobelts 23 and the fabrication and characterization of the FET devices have been described in detail previously. 24 In brief, high-performance SnO 2 nanobelt FETs were obtained on individual nanobelts on Si/SiO 2 substrates (degenerately doped n-Si with 100 nm thermal oxide). Cr/Au met...

Mitochondria are essential organelles involved in the maintenance of cell growth and function, and have been investigated as therapeutic targets in various diseases. Recent studies have demonstrated that direct mitochondrial transfer can restore cellular functions of cells with inherited or acquired mitochondrial dysfunction. However, previous mitochondrial transfer methods are inefficient and time-consuming. Here, we developed a simple and easy mitochondrial transfer protocol using centrifugation, which can be applied to any cell type. By our simple centrifugation method, we found that the isolated mitochondria could be successfully transferred into target cells, including mitochondrial DNA-deleted Rho0 cells and dexamethasone-treated atrophic muscle cells. We found that mitochondrial transfer normalised ATP production, mitochondrial membrane potential, mitochondrial reactive oxygen species level, and the oxygen consumption rate of the target cells. Furthermore, delivery of intact mitochondria blocked the AMPK/FoxO3/Atrogene pathway underlying muscle atrophy in atrophic muscle cells. Taken together, this simple and rapid mitochondrial transfer method can be used to treat mitochondrial dysfunction-related diseases.

In this study, we developed a composite filler comprising cross-linked hyaluronic acid (HA) and human collagen (COL) derived from the human umbilical cord with the aim of improving its biocompatibility and longevity compared with commercially available fillers. After HA/ COL composite fillers were made in two different ratios (10:1 and 5:1), the physical properties of the fillers were evaluated. The interior morphologies and in vivo weight change of these hydrogels were also characterized at 1-16 weeks after injection into mice. To evaluate their biocompatibility and durability in vivo, we injected the composite fillers into nude mice subcutaneously. The variations of injected gel weight were measured and compared with the commercial dermal fillers (Restylane and TheraFill). The composites showed improved or similar physical properties (complex viscosity of 19-22 × 10(5) cP, and injection force of 10- 12 N) over the commercial dermal fillers. Sixteen weeks following the injection, the ratio of remaining composite filler weight to initial weight (75.5 ± 16.9%; 10:1) was shown to be greater than that of the commercial fillers (43.2 ± 8.1%, Restylane; 12.3 ± 5.3%, TheraFill). In addition, immunohistochemical analysis with angiogenesis-related markers such as isolectin and vWF revealed newly formed blood vessels and cellular influx into the composite filler, which were not observed in the other fillers. These results clearly suggest that the HA/COL composite filler is a superior candidate for soft tissue reconstruction. The filler we developed may be a suitable candidate as an injectable dermal filler for tissue augmentation in humans.

We report a three-dimensional nanoinjection system for direct injection of biomolecules into a single cell.