Thiolene-Based Microfluidic Flow Cells for Surface Plasmon Resonance Imaging

Thiolene-based microfluidic devices have been coupled with surface plasmon resonance imaging (SPRI) to provide an integrated platform to study interfacial interactions in both aqueous and organic solutions. In this work, we develop a photolithographic method that interfaces commercially available thiolene resin to gold and glass substrates to generate microfluidic channels with excellent adhesion that leave the underlying sensor surface free from contamination and readily available for surface modification through self-assembly. These devices can sustain high flow rates and have excellent solvent compatibility even with several organic solvents. To demonstrate the versatility of these devices, we have conducted nanomolar detection of streptavidin-biotin interactions using in situ SPRI. (C) 2011 American Institute of Physics. [doi:10.1063/1.3596395

Magnetic Nanoparticle-Based Hyperthermia for Head & Neck Cancer in Mouse Models

In this study, magnetic iron oxide nanoparticle induced hyperthermia is applied for treatment of head and neck cancer using a mouse xenograft model of human head and neck cancer (Tu212 cell line). A hyperthermia system for heating iron oxide nanoparticles was developed by using alternating magnetic fields. Both theoretical simulation and experimental studies were performed to verify the thermotherapy effect. Experimental results showed that the temperature of the tumor center has dramatically elevated from around the room temperature to about 40oC within the first 5-10 minutes. Pathological studies demonstrate epithelial tumor cell destruction associated with the hyperthermia treatment

Ferrohydrodynamic Isolation of Circulating Tumor Cells and Exosomes

Presented online October 29, 2020 from 11:00 a.m.-12:00 p.m. Fall 2020 NANOFANS Webinar Series: Session 4.Fall 2020 NanoFANS (Focusing on Advanced Nanobio-Systems) Forum - “Bridging Biology & Nanotechnology".Leidong Mao is a Professor in the School of Electrical and Computer Engineering at the University of Georgia in Athens, GA. He received his PhD in electrical engineering from Yale University. He is interested in developing new microfluidic technologies for biological or biomedical applications such as cancer cell isolation and understanding the biological clock.Runtime: 49:06 minutesManipulating micron- and nano-sized objects in magnetic liquids in a continuous flow through so-called “ferrohydrodynamics” is a relatively new research field. It has resulted in label-free manipulation techniques in microfluidic systems and exciting applications such as circulating tumor cells (CTCs) and exosomes enrichment. It is the goal of this talk to introduce the fundamental principles of ferrohydrodynamics and its recent applications in microfluidic enrichment of CTCs and exosomes developed in my lab

A study of ferrohydrodynamics under traveling magnetic field excitations

In this thesis, a new ferrofluid pumping scheme based on traveling magnetic fields is studied. The modeling and the simulation of the ferrofluid pumping under sinusoidally time-varying and spatially traveling magnetic fields are presented. A second order finite difference scheme in both Cartesian and Cylindrical coordinates is used to calculate the flow and spin velocities of the ferrofluid in a one-dimensional case. The two-dimensional case is simulated by using a commercial multi-physics package COMSOL. It is shown theoretically that, under traveling magnetic field excitation, maximum flow velocity is achieved when the product of the excitation wave number and the height of the ferrofluid channel (Cartesian case) or the radius of the ferrofluid channel (Cylindrical case) is unity. Once geometric dimensions are chosen, maximum pumping is achieved when the excitation frequency is the reciprocal of the overall relaxation time constant of the magnetic nanoparticles. In order to verify the theory, macro-scale experiments of this ferrofluid actuation scheme are conducted. The results show that oil-based EFH1 ferrofluids can be pumped up to 7.4 mm/sec under 9 kA/m magnetic fields with a maximum pressure drop of 4.7 Pa. Furthermore, micro-scale experimental study of this ferrofluid actuation scheme and a pathogen detection scheme based on the ferrofluid actuation are also presented. Stopped flow pressure measurements show very good agreement between the simulation and the experimental data. A prototype of the pathogen sensor based on ferrohydrodynamics is fabricated and tested. In the initial experiments, avidin-coated microbeads (3.6 μm in diameter) are used to emulate the geometry of the pathogen cells. The result shows that as few as 66400 microbeads/ml concentration can be detected within minutes. In the end, a new microfluidic mixing concept based on ferrohydrodynamic actuation is demonstrated. The mixer shows 8-12 fold improvement in mixing effectiveness over the diffusive mixing

Direct observation of closed-loop ferrohydrodynamic pumping under traveling magnetic fields

Ferrofluid-based liquid manipulation schemes typically actuate an immiscible liquid via a ferrofluid plug, using high magnetic flux (∼1 T) densities and strong field gradients created with bulky permanent magnets. They rely on surface tension effects to maintain the cohesion of the ferrofluid plug, necessitating miniature channels and slow (∼1 μl/min) flow speeds. Here, we demonstrate direct ferrohydrodynamic pumping using traveling magnetic fields at controllable speeds in a simple, closed-loop geometry without any mechanically actuated components. The pumping approach is compact, scalable, and practical. Using moderate field amplitudes (∼10 mT), we obtained a maximum volumetric flow rate of 0.69 ml/s using a readily available commercial ferrofluid. Our closed-loop pumping approach could lead to integrated and efficient liquid manipulation and cooling schemes based on ferrofluids.National Science Foundation (U.S.) (ECCS-0449264; ECCS-0529190

Thiolene-based microfluidic flow cells for surface plasmon resonance imaging

Thiolene-based microfluidic devices have been coupled with surface plasmon resonance imaging (SPRI) to provide an integrated platform to study interfacial interactions in both aqueous and organic solutions. In this work, we develop a photolithographic method that interfaces commercially available thiolene resin to gold and glass substrates to generate microfluidic channels with excellent adhesion that leave the underlying sensor surface free from contamination and readily available for surface modification through self-assembly. These devices can sustain high flow rates and have excellent solvent compatibility even with several organic solvents. To demonstrate the versatility of these devices, we have conducted nanomolar detection of streptavidin-biotin interactions using in situ SPRI

Magnetic Nanoparticle-Based Hyperthermia for Head & Neck Cancer in Mouse Models

In this study, magnetic iron oxide nanoparticle induced hyperthermia is applied for treatment of head and neck cancer using a mouse xenograft model of human head and neck cancer (Tu212 cell line). A hyperthermia system for heating iron oxide nanoparticles was developed by using alternating magnetic fields. Both theoretical simulation and experimental studies were performed to verify the thermotherapy effect. Experimental results showed that the temperature of the tumor center has dramatically elevated from around the room temperature to about 40oC within the first 5-10 minutes. Pathological studies demonstrate epithelial tumor cell destruction associated with the hyperthermia treatment.</p

Acceleration of Tissue Plasminogen Activator-Mediated Thrombolysis by Magnetically Powered Nanomotors

Dose control and effectiveness promotion of tissue plasminogen activator (t-PA) for thrombolysis are vitally important to alleviate serious side effects such as hemorrhage in stroke treatments. In order to increase the effectiveness and reduce the risk of stroke treatment, we use rotating magnetic nanomotors to enhance the mass transport of t-PA molecules at the blood clot interface for local ischemic stroke therapy. The <i>in vitro</i> experiments demonstrate that, when combined with magnetically activated nanomotors, the thrombolysis speed of low-concentration t-PA (50 μg mL^–1) can be enhanced up to 2-fold, to the maximum lysis speed at high t-PA concentration. Based on the convection enhanced transport theory due to rotating magnetic nanomotors, a theoretical model is proposed and predicts the experimental results reasonably well. The validity and efficiency of this enhanced treatment has been demonstrated in a rat embolic model