Page 81 - ASME_NEMB_2016_Program

TRACK 6 TRACK 6 Technical Program

with 250 µl reservoirs. FTC and TAF were mixed separately in aqueous, Currently, the novel chip was designed to detect the level of hydrogen sul-
isotonic solutions near their solubility limits (110 and 20 mg/ml, respectively) fide present in the blood. A unique LOC device has a various parts which
and syringe loaded individually into implant reservoirs. The implants incor- serves as specific purpose. The micro-fabricated layer was coated with
porated membranes with nanochannels either 20 or 250 nm in height. The the sulfide liberation buffer. The liberated gas was then passed via a highly
drug concentration was measured using an HPLC protocol developed by selective polymer membrane and then collected at the final chamber for
our group. The transcutaneous refill method was tested by loading a 600 µL its quantification. The electrochemical detection was made possible at this
capsule with a known FTC concentration and placing it under the skin of a chamber using boron doped nanocrystalline diamond electrode (BDUNCD)
chicken thigh. Venting and loading needles were inserted into the ports of electrode of various sizes. Both direct and indirect detection have been
the device through the skin, and 1.5 ml of air was circulated through the de- investigated and compared. Detection of sulfide via the catalytic electro-
vice to remove all liquid before pushing either 1, 1.5, 2, and 2.5 ml volumes chemical oxidation of ferrocyanide was much promising and low power
of fresh FTC solution through the reservoir. Drug concentration was then consumption. This research highlights the optimization of sensor integrated
measured using UV-Vis spectroscopy. lab on the chip device to detect sulfide in biological range in a water based
sample. The working of the device proof detection of hydrogen sulfide or
Results and Discussion: other blood gas in similar fashion. The optimized sensor have a linear detec-
Constant, sustained delivery was measured for up to 2 weeks in vitro for tion which makes the sensor possible for calibration. The limit of detection
the 20 nm membranes. In addition, FTC’s higher loading concentration was 0.1 µM. The detection of the gas was less labor intensive, fast and low
(about 6X) and smaller size resulted in a higher average daily release of 650 cost compared to the any other techniques due to its possibility of the minia-
µg than 120 µg for TAF. The 250 nm nanochannels demonstrated a burst turization and batch fabrication. The first commercialized product will server
release on Day 1 with a release of 4 mg and 3 mg followed by an average for peripheral artery disease (PAD) patients.
daily release of 420 µg and 160 µg for FTC and TAF, respectively. This initial
burst release is associated with insufficient nanoconfinement, leading to an
exponential decay of drug from the implant reservoir, which is in contrast to A Robust Oil-Free DC Digital Microfluidic Device By Induced Lat-
the more clinically desirable linear decay seen in the 20 nm membranes. eral Electric Field (LEF)
The transcutaneously refilled drug solution was removed from the reser-
voir and measured to be 87%, 93%, 96%, and 97% of the loading solution
concentration for the 1, 1.5, 2, and 2.5 ml refill volumes, respectively. This Poster Presentation. NEMB2016-6034
indicates that at least 2 ml of the FTC drug solution must be used to achieve
at least a 95% nominal drug concentration. This volume may be reduced by Md Enayet Razu, Dept. of Mechanical Eng./Texas Tech University,
increasing the FTC drug concentration to approximately 105% of the desired Lubbock, TX, United States, Jungkyu Kim, Texas Tech University,
loading concentration. Lubbock, TX, United States

Conclusion: Digital microfluidics (DMF) is used in numerous lab-on-a-chip (LOC) applica-
We have been able to demonstrate controlled, long-term release of FTC and tions including proteomic sample preparation, enzyme assays, polymerase
TAF for HIV pre-exposure prophylaxis using our nDS technology. An in vivo chain reaction, immunoassays, clinical sample processing and applications
pharmacokinetic study on the release of these drugs from the nDS within involving cells. A combination of electrowetting and electromechanical force
macaque models is currently ongoing. These results demonstrate that the applied by DC or AC electric field enables manipulation of droplet surround-
nDS approach has the potential to revolutionize the standard of care for HIV ed by oil or air, respectively. While DC based DMF can be a cheap and por-
prophylaxis. table LOC device, AC based DMF contradicts portability since AC amplifiers
are more expensive and larger in size compare to DC. However, breakdown
of the dielectric layers at micro-nano scale is unpredictable for DC voltage
Boron Doped NanoCrystalline Diamond Sensor Integrated Lab in air medium and DC-based DMF devices working in air medium suffers
On A Chip Device For Blood Gas Sensing Using Electrochemical from electrolysis and charge accumulation. Silicone oil is commonly used as
Approach. surrounding fluid to solve this problem by reducing droplet surface tension,
which limits the applicability of the DMF device in biological processes.
Once silicone oil is applied to the device surface, it’s also nontrivial to clean
Poster Presentation. NEMB2016-6033 device surface. In this study, a robust oil-free DC digital microfluidics device
is developed, which can be long term operational without electrolysis by
Ashok Baniya, Latech, Ruston, LA, United States, Leland Weiss, increasing electrostatic force by electric field modulation.
Louisiana Tech University, Ruston, LA, United States, Prabhu Aru-
mugam, latech, Ruston, LA, United States DMF chip is fabricated by subsequent coating of 2.7 µm parylene and 60 nm
Cytop on 100 nm chromium coated glass slide (75 mm x 25 mm) as bottom
Blood gas measurement are used to evaluate a person’s lung function and electrode and an ITO coated glass slide (50 mm x 25 mm) is used as top
acid /base balance. The proposed sensor integrated lab on the chip device ground electrode. Bottom electrodes were fabricated using standard pho-
was manufactured to severe the diagnostic purposes of such applications. tolithography technique and 1.5 mm x 1.5 mm electrodes were created. The
Hydrogen sulfide (H2S) has emerged as an important signaling molecule device top to bottom plate spacing was kept at 90 µm. Droplets of DI water
that plays significant roles in health and disease. Work from many labs has were dispensed and manipulated by applying + 120dc to electrode adjacent
revealed that H2S bioavailablilty and exogenous hydrogen sulfide therapy to droplet and negative ground to droplet containing electrode along with
regulate numerous disease states including inflammation, cancer, cardio- top ground electrode to induce lateral electric field (LEF), thus increasing
vascular, neurological and gastrointestinal diseases. This proposed work electromechanical force in the direction of droplet translation. By appying
investigates and demonstrates new H2S detection techniques well suited to LEF threshold voltage was reduced down to 80 Vdc while it was >>300 Vdc
disease detection and biomedical application through a Lab on a Chip (LOC) without LEF for 2.7 µm parylene coated electrode. Voltage was amplified us-
approach. ing EMCO Q03-24 and controlled by a custom built switching board, which
can simultaneously apply positive high voltage and negative ground to the
As the significance of H2S grows, the ability to foster clinical detection and electrodes. Repetitive droplet dispensing, transport, split and merging were
promote treatment becomes increasingly critical. Current technology relies performed without any electrolysis in air medium. Dispensing was performed
on elaborate methodologies that impede real world use in a clinical setting. for more than 100 times without any failure with at least three droplets gen-
Present day small scale systems are incapable of micro-molar (µM) H2S erated from a reservoir volume of 3 µL. Average volume of droplets was
detection. This is a critical limitation because disease detection requires this found to be 230 nL with only 3.9 % deviation for reservoir to control elec-
degree of precision. This constraint further hampers the ability to expand trode surface area ratio of 10. In continuation of our current observation, we 81
detection and treatment to medical fields in third world applications or other will present the effect of electric field, effect of charge density and polarity of
environments where cost is a significant issue. droplet on the droplet motion and effect on the biomolecules.