Wentao Su

Microfluidic platform towards point-of-care diagnostics in infectious diseases

Rapid and timely diagnosis of infectious diseases is a critical determinant of clinical outcomes and general public health. For the detection of various pathogens, microfluidics-based platforms offer many advantages, including speed, cost, portability, high throughput, and automation. This review provides an overview of the recent advances in microfluidic technologies for point-of-care (POC) diagnostics for infectious diseases. The key aspects of such technologies for the development of a fully integrated POC platform are introduced, including sample preparation, on-chip nucleic acid analysis and immunoassay, and system integration/automation. The current challenges to practical implementation of this technology are discussed together with future perspectives.

Dissimilatory nitrate reduction by Pseudomonas alcaliphila with an electrode as the sole electron donor

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were considered two alternative pathways of dissimilatory nitrate reduction. In this study, we firstly reported that both denitrification and DNRA occurred in Pseudomonas alcaliphila strain MBR with an electrode as the sole electron donor in a double chamber bio‐electrochemical system (BES). The initial concentration of nitrate appeared as a factor determining the type of nitrate reduction with electrode as the sole electron donor at the same potential (−500 mV). As the initial concentration of nitrate increased, the fraction of nitrate reduced through denitrification also increased. While nitrite (1.38 ± 0.04 mM) was used as electron acceptor instead of nitrate, the electrons recovery via DNRA and denitrification were 43.06 ± 1.02% and 50.51 ± 1.37%, respectively. The electrochemical activities and surface topography of the working electrode catalyzed by strain MBR were evaluated by cyclic voltammetry and scanning electron microscopy. The results suggested that cells of strain MBR were adhered to the electrode, playing the role of electron transfer media for nitrate and nitrite reduction. Thus, for the first time, the results that DNRA and denitrification occurred simultaneously were confirmed by powering the strain with electricity. The study further expanded the range of metabolic reactions and had potential value for the recognization of dissimilatory nitrate reduction in various ecosystems. Biotechnol. Bioeng. 2012; 109: 2904–2910.

The direct electrocatalysis of phenazine-1-carboxylic acid excreted by Pseudomonas alcaliphila under alkaline condition in microbial fuel cells

In this paper, we reported a kind of exoelectrogens, Pseudomonas alcaliphila (P. alcaliphila) strain MBR, which could excrete phenazine-1-carboxylic acid (PCA) to transfer electron under alkaline condition in microbial fuel cells (MFCs). The electrochemical activity of strain MBR and the extracellular electron transfer mechanism in MFCs were evaluated by cyclic voltammetry (CV) and electricity generation curve measurement. The results indicated a soluble mediator was the key factor for extracellular electron transfer of strain MBR under alkaline condition. The soluble mediator was PCA detected by gas chromatography-mass (GC-MS) analyses.

Autotrophic nitrogen removal from ammonium at low applied voltage in a single-compartment microbial electrolysis cell

A new approach was developed to achieve autotrophic nitrogen removal from ammonium at low applied voltage in a single-compartment 3-dimensional microbial electrolysis cell (MEC). The MEC consisted of anodic and cathodic electrodes, on which nitrifying and denitrifying biofilms, respectively, were attached. Nitrogen removal can be enhanced at an applied voltage in the MEC. Besides, the nitrogen removal efficiency gradually increased from 70.3% to 92.6% with the increase of applied voltage from 0.2 to 0.4V, as well as the maximum current was varied from 4.4 to 14 mA. The corresponding coulombic efficiency also increased from 82% to 94.4%, indicating that the increasing applied voltage could enhance electron extraction from ammonium during its oxidative removal. The DO was found to be a critical factor which affected the nitrogen removal in this MEC system. These results demonstrated that the MEC process was applicable to achieve autotrophic nitrogen removal from wastewater containing ammonium.

Simultaneous biodegradation of Ni-citrate complexes and removal of nickel from solutions by Pseudomonas alcaliphila.

The objective of this study was to study the simultaneous biodegradation of Ni-citrate complexes and removal of Ni from solutions by Pseudomonas alcaliphila. Adding excess citrate to 1:1 Ni-citrate complexes promoted the degradation of the complexes and removal of Ni. The alkaline pH generated by the metabolism of excess citrate caused partial dissociation of citrate from the Ni-citrate complexes, allowing degradation, and the released Ni was removed through bioaccumulation and precipitation. Addition of Fe(3+) enhanced the degradation of Ni-citrate complexes and removal of Ni from solutions. The displacement of Ni from recalcitrant Ni-citrate complexes by Fe(3+) and subsequent biodegradation of the degradable Fe(III)-citrate complex resulted in complete metabolism of citrate. The almost complete removal of Ni (>98%) can be attributed to the combination of coprecipitation with Fe(3+), bioaccumulation and precipitation. P. alcaliphila potentially could be applied in the treatment of effluent containing Ni-citrate complexes.

Effects of cathode potentials and nitrate concentrations on dissimilatory nitrate reductions by Pseudomonas alcaliphila in bioelectrochemical systems

The effects of cathode potentials and initial nitrate concentrations on nitrate reduction in bioelectrochemical systems (BESs) were reported. These factors could partition nitrate reduction between denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Pseudomonas alcaliphilastrain MBR utilized an electrode as the sole electron donor and nitrate as the sole electron acceptor. When the cathode potential was set from -0.3 to -1.1 V (vs. Ag/AgCl) at an initial nitrate concentration of 100 mg NO3(-)-N/L, the DNRA electron recovery increased from (10.76 ± 1.6)% to (35.06 ± 0.99)%; the denitrification electron recovery decreased from (63.42 ± 1.32)% to (44.33 ± 1.92)%. When the initial nitrate concentration increased from (29.09 ± 0.24) to (490.97 ± 3.49) mg NO3(-)-N/L at the same potential (-0.9 V), denitrification electron recovery increased from (5.88 ± 1.08)% to (50.19 ± 2.59)%; the DNRA electron recovery declined from (48.79 ± 1.32)% to (16.02 ± 1.41)%. The prevalence of DNRA occurred at high ratios of electron donors to acceptors in the BESs and denitrification prevailed against DNRA under a lower ratio of electron donors to acceptors. These results had a potential application value of regulating the transformation of nitrate to N2 or ammonium in BESs for nitrate removal.

Drug absorption related nephrotoxicity assessment on an intestine-kidney chip

Drug absorption in the intestine is tightly related to drug-induced nephrotoxicity, which is a relatively common side effect in clinical practice. It highlights a great need to develop predictive models with high accuracy in the early stage during new drug discovery and development. Herein, we presented a novel intestine-kidney chip, which recapitulated drug absorption in the intestine and its resultant drug toxicity on the kidney. This work aims to provide an integrated tool for accurate assessment of drug absorption-related nephrotoxicity in vitro. A microfluidic device with multi-interfaces was designed, which facilitated the co-culture of the intestinal and glomerular endothelial cells in compartmentalized micro-chambers. Thus, drug absorption and following nephrotoxicity could be explored in a single assay based on the formation of the intact intestine function on the chip. Specifically, we adopt digoxin (DIG) as a model drug combined with colestyramine (COL) or Verapamil (VER), which significantly influence DIG absorption in the intestine. Different degrees of nephrotoxicity under drug combinations were further observed on the chip, including cell apoptosis, cell viability, and lactate dehydrogenase leakage. These features were consistent with the variance of DIG absorption by the intestinal cells. In agreement with clinical observations, our data demonstrated that DIG-induced nephrotoxicity was enhanced combined with VER but weakened with COL. All of these findings suggest that the established microdevice might provide a useful and cost-effective platform in vitro for testing drug absorption and nephrotoxicity in preclinical trials during new drug development.

Assessment of hepatic metabolism-dependent nephrotoxicity on an organs-on-a-chip microdevice

Drug-induced nephrotoxicity is one of the most frequent adverse events in pharmacotherapy. It has resulted in numerous clinical trial failures and high drug development costs. The predictive capabilities of existing in vitro models are limited by their inability to recapitulate the complex process of drug metabolism at the multi-organ level in vivo. We present a novel integrated liver-kidney chip that allows the evaluation of drug-induced nephrotoxicity following liver metabolism in vitro. The liver-kidney chip consists of two polydimethylsiloxane layers with compartmentalized micro-channels separated by a porous membrane. Hepatic and renal cells were co-cultured in separate micro-chambers on a single chip. Ifosfamide and verapamil were used as model drugs, and their metabolites produced by hepatic metabolism were identified using mass spectrometry, respectively. The metabolites triggered significantly distinct nephrotoxic effects as assessed by cell viability, lactate dehydrogenase leakage and permeability of renal cells. This in vitro liver-kidney model facilitates the characterization of drug metabolism in the liver as well as the assessment of subsequent nephrotoxicity in a single assay. Obviously, this multi-organ platform is simple and scalable, and maybe widely applicable to the evaluation of drug metabolism and safety during the early phases of drug development.

A Biomimetic Human Gut-on-a-Chip for Modeling Drug Metabolism in Intestine

Drug metabolism in the intestine is considered to substantially contribute to the overall first-pass metabolism, which has been neglected for a long time. It is highly desirable to develop a reliable model to evaluate drug metabolism in the intestine in vitro. In this work, we made the first attempt to develop a biomimetic human gut-on-a-chip for modeling drug metabolism in intestine. In this chip, constant flow, together with porous nitrocellulose membrane and collagen I, mimics an in vivo-like intestinal microenvironment. The Caco-2 cells grown in the chip formed a compact intestinal epithelial layer with continuous expression of the tight junction protein, ZO-1. Furthermore, higher gene expression of villin, sucrase-isomaltase, and alkaline phosphatase demonstrated that cells in the biomimetic human gut-on-a-chip device were more mature with near-physiological functions compared to the control on planar substrate. In particular, cellular metabolic activity was assessed on different substrates, indicating higher metabolic efficiency of ifosfamide and verapamil in the biomimetic human gut-on-a-chip model. Taken together, our results suggested that this biomimetic human gut-on-a-chip promoted the differentiation of intestinal cells with enhanced functionality by creating a biomimetic 3D microenvironment in vitro. It might offer a bioactive, low-cost, and flexible in vitro platform for studies on intestinal metabolism as well as preclinical drug development.