Solid MRI contrast agents for long-term, quantitative in vivo oxygen sensing.

Targeted MRI contrast agents have proven useful in research and clinical studies for highlighting specific metabolites and biomarkers [Davies GL, et al. (2013) Chem Commun (Camb) 49(84):9704-9721] but their applicability in serial imaging is limited owing to a changing concentration postinjection. Solid enclosures have previously been used to keep the local concentration of contrast agent constant, but the need to surgically implant these devices limits their use [Daniel K, et al. (2009) Biosens Bioelectron 24(11):3252-3257]. This paper describes a novel class of contrast agent that comprises a responsive material for contrast generation and an injectable polymeric matrix for structural support. Using this principle, we have designed a contrast agent sensitive to oxygen, which is composed of dodecamethylpentasiloxane as the responsive material and polydimethylsiloxane as the matrix material. A rodent inspired-gas model demonstrated that these materials are functionally stable in vivo for at least 1 mo, which represents an order of magnitude improvement over an injection of liquid siloxane [Kodibagkar VD, et al. (2006) Magn Reson Med 55(4):743-748]. We also observed minimal adverse tissue reactions or migration of contrast agents from the initial injection site. This class of contrast agents, thus, represented a new and complementary method to monitor chronic diseases by MRI.

Cytotoxicity analysis of water disinfection byproducts with a micro-pillar microfluidic device.

Water disinfection byproducts (DBPs) are a class of chemicals that are produced when chemical disinfectants react with organic materials in untreated water. Cytotoxicity and genotoxicity of DBPs have been systematically evaluated to compile a comparative, quantitative database of in vitro mammalian cell toxicity of DBPs. However, one of the most challenging limitations for current DBP cytotoxicity assessment assays is sample availability. Although our current cytotoxicity assay using a 96-well microplate has been designed to reduce sample consumption, further minimization of the size of the test system would allow us to explore various possibilities for point-of-care applications. We have developed a microfluidic device with micro-pillars that shows high uniformity in distribution of cells across all chambers with low cell count. We compare the performance between the 96-well microplate and the microfluidic device by running 72-hour standalone-on-chip cell culture and cytotoxicity analysis experiments, using dimethyl sulfoxide (DMSO) and ethanol as model toxic agents, and bromoacetic acid (BAA) as a representative DBP. The results show close agreement between the two systems. The measured LC(50) values for the 96-well microplate and the microfluidic device are 1.54% v/v and 1.27% v/v for DMSO, 1.44% v/v and 2.92% v/v for ethanol, and 17.6 µM and 8.20 µM for BAA, respectively. The micro-pillar microfluidic device offers a great reduction in sample consumption while maintaining the accuracy of the cytotoxicity analyses of water disinfection byproducts.

Microparticle and cell counting with digital microfluidic compact disc using standard CD drive.

Lab-on-chip medical diagnostics in a global health setting would greatly benefit from highly portable, cost effective and readily available devices. Digital compact disc (CD) and the corresponding detection device-CD drives-for personal computers are extremely affordable and distributable worldwide, therefore they can be immediately used in global health applications if empowered with molecular and cellular biosensing functions. Here we present a novel digital microfluidic CD device derived from conventional music or data CD and demonstrate its preliminary application of counting polystyrene microparticles and living cells in minute-volume fluidic samples. No other detection instruments except for a standard CD drive in a personal computer is used for reading and decoding the quantitative liquid sample information from the digital microfluidic CD. The results presented herein are the first step towards creating a truly portable, low-cost and ubiquitously accessible device-health diagnostic compact disc (HDCD)-for biosensing and health diagnostics, especially in remote or impoverished settings with limited medical infrastructure and healthcare workers.