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Perfluorooctanoic acid (PFOA) as an emerging environmental contaminant, has become ubiquitous in the environment. It is of significance to study bioconcentration and tissue distribution of aquatic organisms for predicting the persistence of PFOA and its adverse effects on the environment and human body. However, the distribution of PFOA in different tissues is a complex physiological process affected by many factors. It is difficult to be accurately described by a simple kinetic model. In present study, a new strategy was introduced to research the PFOA distribution in tissues and estimate the exposure stages. Zebrafish were continuously exposed to 25 mg/L PFOA for 30 days to simulate environmental process. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) method was used to monitor the spatio-temporal distribution of PFOA in zebrafish tissues. By analyzing the law of change obtained from the high spatial resolution MSI data, two different enrichment trends in ten tissues were summarized by performing curve fitting. Analyzing the ratio of two types of curves, a new “exposure curve” was defined to evaluate the exposure stages. With this model, three levels (mild, moderate, and deep pollution stage) of PFOA pollution in zebrafish can be simply evaluated.

A novel method for one-pot synthesis of functional oil rich in diacylglycerols (DAGs), phytosterol esters (PEs) and α-linolenic acid (ALA) was developed. Firstly, candida rugosa lipase (CRL) and thermomyces lanuginosus lipase (TLL) were co-immobilized on polydopamine coated Fe3O4 nanoparticles (PDA@Fe3O4 NPs) via covalent bonds. The prepared co-immobilized bi-lipases (CRL/TLL-PDA@Fe3O4) displayed excellent thermal stability, catalytic activity and reusability in comparison to the free forms. Then a rapid one-pot enzymatic synthesis of functional oil was conducted by using CRL/TLL-PDA@Fe3O4 as the biocatalyst. Three kinds of functional oils were produced with high DAGs, PEs and ALA content (≥30.09%, ≥15.61% and ≥26.45%, respectively) under the optimized conditions (1:3:2 phytosterols/ALA/triglycerides, 20 mg/mL CRL/TLL-PDA@Fe3O4, 40 °C, 8 h). In comparison to a two-step (sequential/immobilized monolipase) synthesis, a significantly synergistic effects occurred in the co-immobilized bi-lipases system. The results demonstrated the feasibility of the novel strategy and would be helpful for the oils and fats industry.

A fluorometric and magnetic resonance (MR) dual-modal detection scheme is presented for determination of ascorbic acid (AA). It is based on the use of a blended Au/MnO2@BSA mixture that was prepared via a biomimetic strategy, using bovine serum albumin (BSA) as the template at physiological temperature. The MnO2@BSA fraction (one part of the composite) is not susceptible to MR but can be degraded to MR-active compounds upon a redox reaction with even ultralow concentrations of AA. In parallel, the blended Au/MnO2@BSA recovers its fluorescence because MnO2@BSA acts as a quencher of the fluorescence of circumjacent Au@BSA (the other part of the composite). Fluorescence typically is measured at excitation/emission wavelengths of 470/625 nm. Leveraging on this redox reaction between MnO2 and AA, a dual-mode detection scheme for AA was developed. Both the fluorescence and the MR signal increase with the concentration of AA. The lowest limit for the detection of AA is 0.6 μM in the fluorometric mode and 0.4 μM in the MR mode. Analysis of AA-spiked serum samples showed that the recoveries obtained by either the fluorometric and MR mode can reach 94%. This is the first report of the use of blended nanoparticles with their inherent cross-validation regularity.

Axon branching enables neurons to contact with multiple targets and respond to their microenvironment. Owing to its importance in neuronal network formation, axon branching has been studied extensively during the past decades. The chemical properties of extracellular matrices have been proposed to regulate axonal development, but the effects of their density changes on axon branching are not well understood. Here, we demonstrate that both the sharp broadening of substrate geometry and the sharp change of laminin density stimulate axon branching by using microcontact printing (μCP) and microfluidic printing (μFP) techniques. We also found that the change of axon branching stimulated by laminin density depends on myosin II activity. The change of laminin density induces asymmetric extensions of filopodia on the growth cone, which is the precondition for axon branching. These previously unknown mechanisms of change of laminin density-stimulated axon branching may explain how the extracellular matrices regulate axon branching in vivo and facilitate the establishment of neuronal networks in vitro.

Axon specification during neuronal polarization is closely associated with increased microtubule stabilization in one of the neurites of unpolarized neuron, but how this increased microtubule stability is achieved is unclear. Here, we show that extracellular matrix (ECM) component laminin promotes neuronal polarization via regulating directional microtubule assembly through β1 integrin (Itgb1). Contact with laminin coated on culture substrate or polystyrene beads was sufficient for axon specification of undifferentiated neurites in cultured hippocampal neurons and cortical slices. Active Itgb1 was found to be concentrated in laminin-contacting neurites. Axon formation was promoted and abolished by enhancing and attenuating Itgb1 signaling, respectively. Interestingly, laminin contact promoted plus-end microtubule assembly in a manner that required Itgb1. Moreover, stabilizing microtubules partially prevented polarization defects caused by Itgb1 downregulation. Finally, genetic ablation of Itgb1 in dorsal telencephalic progenitors caused deficits in axon development of cortical pyramidal neurons. Thus, laminin/Itgb1 signaling plays an instructive role in axon initiation and growth, both in vitro and in vivo, through the regulation of microtubule assembly. This study has established a linkage between an extrinsic factor and intrinsic cytoskeletal dynamics during neuronal polarization.

In this report we fabricated laminin (LN) stripes on a background of poly-L-lysine as substrates for the growth of rat hippocampal neurons, and found that a sharp change of the concentration of LN guides the growth of neurites by leading the growth cones in a time- and space-dependent manner. The percentage of neurites that grow along the edge of LN stripes (where there is a sharp change of concentration) decreases as a function of the concentration of LN under a threshold value. The actin cytoskeleton plays an important role in the process of growth cone's response to the sharp change of concentration of LN on micropatterns. We believe that the findings here are useful for not only fundamental studies in neuroscience, but also helpful for the design of devices or chips for nervous prosthesis.