Sepsis is a lethal disease caused by a systemic microbial infection that spreads via the bloodstream to overwhelm the body's defenses. Current therapeutic approaches are often suboptimal, in part, because they do not fully eliminate the pathogen, and hence the source of deadly toxins. Here we describe an extracorporeal blood cleansing device to selectively remove pathogens from contaminated blood and thereby enhance the patient's response to antibiotic therapy. Immunomagnetic microbeads were modified to create magnetic opsonins that were used to cleanse flowing human whole blood of Candida albicans fungi, a leading cause of sepsis-related deaths. The micromagnetic-microfluidic blood cleansing device generates magnetic field gradients across vertically stacked channels to enable continuous and high throughput separation of fungi from flowing whole blood. A multiplexed version of the device containing four parallel channels achieved over 80% clearance of fungi from contaminated blood at a flow rate of 20 mL/h in a single pass, a rate 1000 times faster than a previously described prototype micromagnetic-microfluidic cell separation system. These results provide the first proof-of-principle that a multiplexed micromagnetic-microfluidic separation system can be used to cleanse pathogens from flowing human blood at a rate and separation efficiency that is relevant for clinical applications.

Rapid progress in understanding the molecular mechanisms associated with cochlear and auditory nerve degenerative processes offers hope for the development of gene-transfer and molecular approaches to treat these diseases in patients. For therapies based on these discoveries to become clinically useful, it will be necessary to develop safe and reliable mechanisms for the delivery of drugs into the inner ear, bypassing the blood-labyrinthine barrier. Toward the goal of developing an inner ear perfusion device for human use, a reciprocating microfluidic system that allows perfusion of drugs into the cochlear perilymph through a single inlet hole in scala tympani of the basal turn was developed. The performance of a prototype, extracorporeal reciprocating perfusion system in guinea pigs is described. Analysis of the cochlear distribution of compounds after perfusion took advantage of the place-dependent generation of responses to tones along the length of the cochlea. Perfusion with a control artificial perilymph solution had no effect. Two drugs with wellcharacterized effects on cochlear physiology, salicylate (5 mM) and DNQX (6,7-Dinitroquinoxaline-2,3-dione; 100 and 300 μM), reversibly altered responses. The magnitude of drug effect decreased with distance from the perfusion pipette for up to 10 mm, and increased with dose and length of application.

A more effective treatment of bacteremia requires a diagnostic platform that is both sensitive, accurate and rapid. Currently, clinical laboratory techniques require growth of bacteria prior to diagnosis, take days to complete, and leave empiric therapy and broad spectrum antibiotics as the only option at the onset of treatment. In order to bypass this growth requirement, we engineered a system that purifies bacteria from blood to improve performance in a bacteriophage-based luminescence assay. To perform the purification, we used acoustophoresis in plastic microfluidic chips, enabling future development into a low cost point-of-care system. Acoustophoresis achieves differential separation on the basis of size differences between bacteria and blood cells. We show isolation of three known pathogen species, including members of both Gram-negative and positive-bacteria from blood, and show isolation at clinically relevant concentrations. Using the device as a preparation step prior to the bacteriophage-based luminescence assay, we demonstrate a 33-fold improvement in limit of detection, compared with the unpurified sample, achieving a limit of detection of 6 bacteria.

The design, fabrication, and evaluation of two dimensional array transducers for real-time volumetric imaging are described. The transducers we have previously described operated at frequencies below 3 MHz and were unwieldy to the operator because of the interconnect schemes used in connecting to the transducer handle. Several new transducers have been developed using new connection technology. A 40 x 40 = 1,600 element, 3.5 MHz array was fabricated with 256 transmit and 256 receive elements. A 60 x 60 = 3,600 element 5.0 MHz array was constructed with 248 transmit and 256 receive elements. An 80 x 80 = 6,400 element, 2.5 MHz array was fabricated with 256 transmit and 208receive elements. 2-D transducer arrays were also developed for volumetric scanning in an intra cardiac catheter, a 10 x 10 = 100 element 5.0 MHz forward-looking array and an 11 x 13 = 143 element 5.0 MHz side-scanning array. The-6dB fractional bandwidths for the different arrays varied from 50% to 63%, and the 50 omega insertion loss for all the transducers was about-64 dB. The transducers were used to generate real-time volumetric images in phantoms and in vivo using the Duke University real time volumetric imaging system, which is capable of generating multiple planes at any desired angle and depth within the pyramidal volume.