Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

Microfabricated device for impedance-based electronic detection of bacterial metabolism

The objective of this research project was to develop a microfabricated technology platform for studying the use of a microscale impedance-based method for the detection of bacterial metabolism. Listeria innocua and Listeria monocytogenes were chosen as model microorganisms for testing the technology. Impedance-based detection of bacterial metabolism relies on measuring changes in the AC impedance of two electrodes immersed in a liquid were the bacteria are cultured, caused by the release of ionic species by metabolizing bacterial cells. Two silicon-based microfluidic biochip prototypes were fabricated, containing a network of microfluidic channels and chambers fitted with interdigitated metallic electrodes. The first biochip was used to demonstrate that the metabolic activity of bacterial cells can be detected in a few hours, and to study methods for extracting metabolism-related information from the impedance data. Bacterial suspensions were injected into the chip and incubated in a nutrient broth in a 5.3 nl chamber, at a temperature that results in optimal bacterial growth. During incubation the complex impedance of the suspensions was measured over time at several frequencies between 100 Hz and 1 MHz, using electrodes in direct contact with the suspensions. A circuit model of the electrodes was fitted to the measured impedance curves, and some of the parameters extracted from the fit, together with the raw impedance, were used as detection signals. The shape and magnitude of the changes in these parameters over time indicated the presence or absence of metabolic activity inside the chip. Impedance measurements of suspensions of live L. innocua and L. monocytogenes cells showed a very clear metabolic signal, compared with measurements done on suspensions of dead cells or of sterile media. The second biochip was designed to concentrate and capture cells from dilute suspensions, using dielectrophoresis, into a 0.4 nl chamber where incubation and impedance measurements were performed after the cells were captured. This biochip was used to concentrate cells from dilute suspensions by factors of 104 to 105. The metabolic activity of concentrated L. monocytogenes cells could be detected in one hour or less, while that of non-concentrated cells was detected after more than 7 hours of incubation

Multinozzle Emitter Array Chips for Small-Volume Proteomics

High-throughput multiplexed proteomics of small-volume biospecimens will generate new opportunities in theranostics. Achieving parallel top-down and bottom-up mass spectrometry analyses of target proteins using a unified apparatus will improve proteome characterization. We have developed a novel silicon-based microfluidic device, multinozzle emitter array chip (MEA chip), as a new platform for small-volume proteomics using liquid chromatography-nanoelectrospray ionization mass spectrometry (LC-nanoESI-MS). We demonstrate parallel, on-chip, and online LC-MS analysis of hemoglobin and its tryptic digests directly from microliters of blood, achieving a detection limit of less than 5 red blood cells. Our MEA chip will enable clinical proteomics of small-volume samples

An open-source, programmable pneumatic setup for operation and automated control of single- and multi-layer microfluidic devices

Microfluidic technologies have been used across diverse disciplines (e.g. high-throughput biological measurement, fluid physics, laboratory fluid manipulation) but widespread adoption has been limited in part due to the lack of openly disseminated resources that enable non-specialist labs to make and operate their own devices. Here, we report the open-source build of a pneumatic setup capable of operating both single and multilayer (Quake-style) microfluidic devices with programmable scripting automation. This setup can operate both simple and complex devices with 48 device valve control inputs and 18 sample inputs, with modular design for easy expansion, at a fraction of the cost of similar commercial solutions. We present a detailed step-by-step guide to building the pneumatic instrumentation, as well as instructions for custom device operation using our software, Geppetto, through an easy-to-use GUI for live on-chip valve actuation and a scripting system for experiment automation. We show robust valve actuation with near real-time software feedback and demonstrate use of the setup for high-throughput biochemical measurements on-chip. This open-source setup will enable specialists and novices alike to run microfluidic devices easily in their own laboratories. Keywords: Microfluidics, Pneumatics, Laboratory automation, Biochip, BioMEMs, Biohacking, Fluid handling, Micro total analysis systems (μTAS), Quake-style valve

A single-cell transcriptomic atlas characterizes ageing tissues in the mouse

Ageing is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death1. Despite rapid advances over recent years, many of the molecular and cellular processes that underlie the progressive loss of healthy physiology are poorly understood2. To gain a better insight into these processes, here we generate a single-cell transcriptomic atlas across the lifespan of Mus musculus that includes data from 23 tissues and organs. We found cell-specific changes occurring across multiple cell types and organs, as well as age-related changes in the cellular composition of different organs. Using single-cell transcriptomic data, we assessed cell-type-specific manifestations of different hallmarks of ageing-such as senescence3, genomic instability4 and changes in the immune system2. This transcriptomic atlas-which we denote Tabula Muris Senis, or 'Mouse Ageing Cell Atlas'-provides molecular information about how the most important hallmarks of ageing are reflected in a broad range of tissues and cell types