Self-polymerization of dopamine at a weak basic condition leads to highly crosslinked, rigid polydopamine that shows strong adhesion against almost any solid substrate28. design of the microchip consisting of flat channels free of common built-in components, such as liquid mixers and surface-anchored sensing elements. The microfluidic assay, using surface-enhanced Raman scattering Alendronate sodium hydrate nanoprobes for signal transduction, allows for streamlined parallel analysis of multiple specimens with greatly improved assay kinetics and delivers ultrasensitive identification and quantification of a panel of cancer protein biomarkers and bacterial species in 1?l of body fluids within 8?min. Introduction Microfluidic systems that offer precise Rabbit Polyclonal to Tau control of fluids, low sample and reagent consumption, and rapid sample processing are of considerable interest for the development of miniaturized, portable and low-cost analytical platforms1,2. In particular, the identification and quantification of molecular and cellular targets using microfluidic biochips are under intense research for a wide spectrum of applications ranging from fundamental biology to clinical diagnostics3C5. Rapid, multiplexed detection of a panel of targets is much needed to address the growing demands for dynamic profiling of analytes, timely diagnosis of heterogeneous diseases and high-throughput screening6C8. Current designs of microfluidic biochips commonly contain built-in components such as sensing element-functionalized surfaces and liquid mixers9,10. Biofunctionalized surfaces serve to separate and enrich targets of interest from complex fluid samples, which is key to specific detection in subsequent signal transduction11,12 On the other hand, spatial confinement in microchannels leads to low Reynolds number fluids under laminar flow, which causes inefficient mixing across the channels mainly controlled by diffusion13. Hence, passive or active mixers are introduced to enhance on-chip liquid mixing and mass transfer, which is critical for improving kinetics and sensitivity of the diffusion-limited on-surface assays in microchips14C16. However, despite recent success in the laboratory-scale demonstration of microfluidic bioanalysis, these necessary built-in components inevitably increase structural, fabricating, operational, and translational complexity of the chips. It remains challenging to realize integrated liquid mixing, bioseparation, and signal transduction in simple microfluidic configurations. Here we report a broadly Alendronate sodium hydrate applicable multiplexing microfluidic biochip based on bioconjugated magnetic nanochains (Magchains). In our Magchain-integrated microchip (MiChip), bioconjugated nanochains are actuated by tailored magnetic fields to play dual-functional functions as nanoscale stir bars to promote rapid active liquid mixing and capture brokers for bioseparation. Magnetic nanostructures were previously used in microfluidic devices to label biomarkers for magnetic detection or separation17C19. However, highly efficient concerted liquid mixing and bioseparation were not performed by magnetic nanostructures for sensing applications. Decoupling these functions traditionally undertaken by on-chip liquid mixers and sensing elements-immobilized surfaces from microfluidic systems enable a simple planar design of the MiChip consisting of flat channels free of built-in components. The Alendronate sodium hydrate MiChip therefore can be broadly adopted for a diverse range of targets and readily refined into multichannel arrays for parallel sample analysis. In this study, we demonstrate that the use of well-dispersed nanochains under continuous mixing overcomes the problem associated with diffusion-limited assay kinetics, giving rise to a rapid turnaround time of <8?min, in contrast to the inefficient target capture at liquidCsolid interfaces in conventional designs. The MiChip assay allows rapid, parallel analysis of small volumes (~1?l) of body fluid specimens, achieving sensitively and selectively quantification, and profiling of cancer protein markers in serum samples from 20 cancer patients and specific bacteria in human saliva. Results Design of the MiChip assay Physique?1 illustrates the design of the MiChip and the on-chip detection of targets by a sandwich immunoassay based on Magchains and Raman-encoded nanoprobes. As shown in Fig.?1a and ?andb,b, the basic unit of the polydimethylsiloxane (PDMS)-on-glass MiChip platform features a mixing chamber, a detection chamber, four fluid ports for sample input and waste output, and two pneumatic microvalves that control the fluid delivery into/from the mixing chamber. The dimensions of each part of the chip are shown in Supplementary Fig.?1a. The chambers and channels have a uniform height of 50 m, with internal surfaces of the MiChip PEGylated to suppress potential biofouling by non-specific constituents in liquid specimens. Of particular note is that the MiChip adopts a simple planar design consisting of flat channels and is free of any target-specific components (Supplementary Fig.?1b). Importantly, the simple design of this basic unit can be easily expanded into integrated multichannel arrays for.