Microfluidic-Integrated Multicolor Immunosensor for Visual Detection of HIV-1 p24 Antigen with the Naked Eye.

Here, a fully integrated multicolor immunosensor was developed for sensitive and reliable semiquantitative analysis of HIV-1 p24, which integrates the multistep reactions of horseradish peroxidase (HRP)-linked immunoassay and gold nanorod (AuNR)-based multicolor assay into a single microfluidic chip. The HRP-linked immunoassay functions by moving magnetic beads bound to a capture antibody through different aqueous phases containing immunoassay reagents. HRP-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) is used to mediate AuNRs etching for producing various color changes. Multiple etching processes can be activated by simple mixing of the reagents from the reagent storage reservoir. The fully integrated strategy with sample-in answer-out capability is initiated by simple chip manipulation and finally concluded by converting recognition of antigen-antibody into a vivid color variation for direct visualization and semiquantitative analysis. By bare eye observation, our integrated multicolor immunosensor allows sensitive and reliable semiquantitative analysis of HIV-1 p24 within 1 h. The microfluidic chip device demonstrated here simplifies the operation significantly and thus allows broader application of a multicolor immunosensor for point of care (POC) testing in low-resource settings.

Enhanced α-ketoglutaric acid production in Yarrowia lipolytica WSH-Z06 by an improved integrated fed-batch strategy.

This study aimed at enhancing α-ketoglutaric acid (α-KG) production by Yarrowia lipolytica WSH-Z06. Batch culture experiments demonstrated that CaCO(3) and a relatively low pH (3.0) in the α-KG production phase contributed to α-KG synthesis. Using a two-stage pH control strategy, in which pH was buffered by CaCO(3) in the growth phase and then maintained at 3.0 in the α-KG production phase, the yield of α-KG reached 53.4 g L(-1). In the later phase of batch fermentation, the glycerol was exhausted but synthesis of α-KG did not cease. Therefore, glycerol was fed with an integrated fed-batch mode, and α-KG production increased to 66.2 g L(-1) with a productivity of 0.35 g L(-1) h(-1). Compared to optimal batch culture, α-KG production and productivity were enhanced by 23.9% and 16.7%, respectively. The two-stage pH control strategy, constant feeding approach and lower pH in later phase would be useful for α-KG industrial production.