Microfluidics enables multiplex evaluation of the same cells for further studies.

OBJECTIVE: The continuous discovery of biomarkers and their evolving use for the diagnosis and guidance of therapy for patients with cancer has increased awareness of the need to triage biospecimens properly. On occasion, cytology samples are the only type of biospecimen available for analysis. Often, the current approach for these latter specimens is cytopathology-centric, with cells limited to examination by bright field microscopy. When specimens are paucicellular, there is often insufficient material for ancillary testing. Therefore, a need exists to develop an alternative approach that allows for the multiplexed analysis of cells when they are limited in number. In recent previous publications, we demonstrated that clinically derived cells from tissue are suitable for evaluation in a microfluidic device. In our current endeavour, we seek to expand upon those findings and determine if those same cells can be recovered for further analysis. METHODS: A microfluidic channel was designed, fabricated and tested using cytology specimens generated from tissue specimens. The cytological features of the cells tested were examined prior to entering the channel; they were then compared to similar cells while in the channel, and upon recovery from the channel. Recovery of DNA and proteins were also tested. RESULTS: The morphology of the tested cells was not compromised in either the channel or upon recovery. More importantly, the integrity of the cells remained intact, with the recovery of proteins and high molecular weight DNA possible. CONCLUSIONS: We developed and tested an alternative approach to the processing of cytopathology specimens that enables multiplexed evaluation. Using microfluidics, cytological examination of biopecimens can be performed, but in contrast to existing approaches, the same cells examined can be recovered for downstream analysis.

Computational analysis of enhanced magnetic bioseparation in microfluidic systems with flow-invasive magnetic elements.

A microfluidic design is proposed for realizing greatly enhanced separation of magnetically-labeled bioparticles using integrated soft-magnetic elements. The elements are fixed and intersect the carrier fluid (flow-invasive) with their length transverse to the flow. They are magnetized using a bias field to produce a particle capture force. Multiple stair-step elements are used to provide efficient capture throughout the entire flow channel. This is in contrast to conventional systems wherein the elements are integrated into the walls of the channel, which restricts efficient capture to limited regions of the channel due to the short range nature of the magnetic force. This severely limits the channel size and hence throughput. Flow-invasive elements overcome this limitation and enable microfluidic bioseparation systems with superior scalability. This enhanced functionality is quantified for the first time using a computational model that accounts for the dominant mechanisms of particle transport including fully-coupled particle-fluid momentum transfer.

Recycling of steel slag and glass cullet from energy saving lamps by fast firing production of ceramics.

The paper reports on some experimental results obtained from the production of ceramics containing steel slag and glass cullet from exhaust energy saving lamps mixed in different proportions. Blending of components was done by attrition milling. Pressed powders were fast fired (50 min, cold to cold) in air up to several temperatures in the range 1000-1140 degrees C. The sintering behaviour was studied by shrinkage and water absorption measurements. Density, strength and hardness of the fired bodies were determined and XRD were examined. The fired samples were finally tested in acidic environment in order to evaluate their elution behaviour and consequently their possible environmental compatibility. It is observed that the composition containing 60 wt.% of steel slag and 40 wt.% of glass cullet displayed the best overall behaviour.

Fast firing of tiles containing paper mill sludge, glass cullet and clay.

The paper describes results obtained in the development of a previous research. We study here, in fast firing, the sintering behaviour and measure some properties of tiles containing a mixture of 60 wt% of paper mill sludge and 40 wt% of glass cullet. The behaviour of this material is compared to those displayed by materials obtained by the same mixture added with 10, 20 and 30 wt% of a natural red clay. In parallel, the same properties are measured also on a reference blend, which is presently used to produce commercial tiles. We show that powders containing 60 wt% of paper sludge and 40 wt% of glass cullet to which 30 wt% of clay is added give rise to materials that display a stable sintering process and have good hardness and strength and therefore could be used for the industrial production of tiles.

Nanoscale magnetic biotransport with application to magnetofection.

We present a model for predicting the transport of biofunctional magnetic nanoparticles in a passive magnetophoretic system that consists of a fluidic chamber positioned above a rare-earth magnet. The model is based on a drift-diffusion equation that governs the particle concentration in the chamber. We solve this equation numerically using the finite volume method. We apply the model to the magnetofection process wherein the magnetic force produced by the magnet attracts magnetic carrier particles with surface-bound gene vectors toward the bottom of the chamber for transfection with target cells. We study particle transport and accumulation as a function of key variables. Our analysis indicates that the particles are magnetically focused toward the center of the chamber during transport, and that the rate of accumulation at the base can be enhanced using larger particles and/or by reducing the spacing between the magnet and the chamber. The model provides insight into the physics of particle transport at the nanoscale and enables rapid parametric analysis of particle accumulation, which is useful for optimizing novel magnetofection systems.

Production and characterization of sintered ceramics from paper mill sludge and glass cullet.

Three different types of paper mill sludge were first incinerated and then attrition milled separately or mixed with glass cullet in varying proportions to obtain powders of different compositions. These powders were then dried, sieved, uniaxially pressed into samples and air sintered. Fired samples were characterized by density, water absorption, shrinkage on firing, strength, hardness and fracture toughness measurements; SEM and X-ray diffractions were also carried out to investigate microstructure and phase composition. Some sintered samples displayed fairly good physical and mechanical properties as a consequence of their low residual porosity and fine microstructure.

A model for predicting magnetic particle capture in a microfluidic bioseparator.

A model is presented for predicting the capture of magnetic micro/nano-particles in a bioseparation microsystem. This bioseparator consists of an array of conductive elements embedded beneath a rectangular microfluidic channel. The magnetic particles are introduced into the microchannel in solution, and are attracted and held by the magnetic force produced by the energized elements. Analytical expressions are obtained for the dominant magnetic and fluidic forces on the particles as they move through the microchannel. These expressions are included in the equations of motion, which are solved numerically to predict particle trajectories and capture time. This model is well-suited for parametric analysis of particle capture taking into account variations in particle size, material properties, applied current, microchannel dimensions, fluid properties, and flow velocity.

Analytical model of magnetic nanoparticle transport and capture in the microvasculature.

An analytical model is presented for predicting the transport and capture of therapeutic magnetic nanoparticles in the human microvasculature. The nanoparticles, with surface bound drug molecules, are injected into the vascular system upstream from malignant tissue, and are captured at the tumor site using a local applied magnetic field. The applied field is produced by a rare-earth cylindrical magnet positioned outside the body. An analytical expression is derived for predicting the trajectory of a particle as it flows through the microvasculature in proximity to the magnet. In addition, a scaling relation is developed that enables the prediction of the minimum particle radius required for particle capture. The theory takes into account the dominant magnetic and fluidic forces, which depend on the position and properties of the magnet, the size and magnetic properties of the nanoparticles, the dimensions of the microvessel, the hematocrit level of the blood, and the flow velocity. The model is used to study noninvasive drug targeting, and the analysis indicates that submicron particles can be directed to tumors that are several centimeters from the field source.