Leidong Mao

• PhD
• Professor (Full) at University of Georgia

Glioblastoma (GBM) is an aggressive brain tumor with limited treatment options and poor patient survival, underscoring the need for novel therapeutic strategies and improved preclinical models. Patient-derived tumor spheroids (PDTSs) offer a physiologically relevant in vitro platform for evaluating treatments such as chimeric antigen receptor (CAR)...

Utilizing a microfluidic chip with serpentine channels, we inoculated the chip with an agar plug with Neurospora crassa mycelium and successfully captured individual hyphae in channels. For the first time, we report the presence of an autonomous clock in hyphae. Fluorescence of a mCherry reporter gene driven by a clock-controlled gene-2 promoter (c...

Introduction: Glioblastoma (GBM) is a stage IV astrocytoma that presents a therapeutic challenge with a poor prognosis and a median survival of 15 months post diagnosis and treatment, primarily due to therapeutic resistance mediated by the tumor microenvironment (TME). Characterizing its microenvironment is crucial for tailoring patient-specific tr...

Quantitative oblique back-illumination microscopy (qOBM) is a label-free imaging technique that enables tomographic phase imaging of thick scattering samples with epi-illumination. Here, we propose the use of two forms of functional imaging with qOBM to study tissue and cell cultures. In doing so, we obtain the spatiotemporal and quantitative funct...

Distinctive subpopulations of circulating tumor cells (CTCs) with increased motility are considered to possess enhanced tumor-initiating potential and contribute to metastasis. Single-cell analysis of the migratory CTCs may increase our understanding of the metastatic process, yet most studies are limited by technical challenges associated with the...

Spheroids offer a unique opportunity to study personalized disease treatment; however, monitoring of these spheroids relies on time-consuming, end-point analyses. Here we apply 3D QPI using quantitative oblique back illumination microscopy (qOBM) to continuously monitor glioblastoma spheroids treated with radiation, immunotherapies, and chemotherap...

Introduction: Glioblastoma multiforme (GBM) is a primary brain tumor with a low survival rate of 12-15 months post-diagnosis and treatment. The current standard of care (SOC) treatments for GBM involves maximal surgical resection followed by radiotherapy and chemotherapy, which is ineffective and does not provide any survival benefit to patients. T...

Simultaneous cell profiling and isolation based on cellular antigen-binding capacity plays an important role in understanding and treating diseases. However, fluorescence-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) are not able to meet this need, due to their requirement for a large quantity of target cells and the limi...

Introduction: Glioblastoma multiforme (GBM) is the most aggressive and malignant form of brain tumor in adults, with a five-year survival rate of 5%. There are no treatment options known to be significantly effective. CAR T-cell therapy uses patient-derived T-cells that have been engineered to express a chimeric antigen receptor (CAR), which can ta...

We determined the macroscopic limit for phase synchronization of cellular clocks in an artificial tissue created by a “big chamber” microfluidic device to be about 150,000 cells or less. The dimensions of the microfluidic chamber allowed us to calculate an upper limit on the radius of a hypothesized quorum sensing signal molecule of 13.05 nm using...

Adaptive and bioinspired droplet-based materials are built using the droplet interface bilayer (DIB) technique, assembling networks of lipid membranes through adhered microdroplets. The properties of these lipid membranes are linked to the properties of the droplets forming the interface. Consequently, rearranging the relative positions of the drop...

Profiling circulating tumor cells (CTCs) of cancer patients is critical to understanding the nature of metastasis. Here we report a combinational approach for the simultaneous biochemical and functional phenotyping of patient-derived CTCs, using an integrated inertial ferrohydrodynamic cell separation (i2FCS) method and a single-cell microfluidic m...

Rapid and label-free separation of target cells in biological samples provided a unique opportunity for disease diagnostics and treatment. Here we described an ultrahigh-throughput microfluidic technology, termed inertial-ferrohydrodynamic cell separation (inertial-FCS), that rapidly sorted through over 60 milliliters of samples at a 100,000 cells/...

We determined the macroscopic limit for phase synchronization of cellular clocks in an artificial tissue created by a “big chamber” microfluidic device to be about 150,000 cells or less. The dimensions of the microfluidic chamber allowed us to calculate an upper limit on the radius of a hypothesized quorum sensing signal of 13.05 nm using a diffusi...

Profiling circulating tumour cells (CTCs) in cancer patients' blood samples is critical to understand the complex and dynamic nature of metastasis. This task is challenged by the fact that CTCs are not only extremely rare in circulation but also highly heterogeneous in their molecular programs and cellular functions. Here we report a combinational...

Rapid and label-free separation of target cells from biological samples provided unique opportunity for disease diagnostics and treatment. However, even with advanced technologies for cell separation, the limited throughput, high cost and low separation resolution still prevented their utility in separating cells with well-defined physical features...

Methods to separate circulating tumor cells (CTCs) from blood samples were intensively researched in order to understand the metastatic process and develop corresponding clinical assays. However current methods faced challenges that stemmed from CTCs' heterogeneity in their biological markers and physical morphologies. To this end, we developed int...

Animal models are frequently used in drug discovery because they represent a mammalian in vivo model system, they are the closest approximation to the human brain, and experimentation in humans is not ethical. Working with postmortem human brain samples is challenging and developing human in vitro systems, which mimic the in vivo human brain, has b...

The vegetative life cycle in the model filamentous fungus, Neurospora crassa, relies on the development of conidiophores to produce new spores. Environmental, temporal, and genetic components of conidiophore development have been well characterized; however, little is known about their morphological variation. We explored conidiophore architectural...

Isolation of exosomes from biological samples provides a minimally-invasive alternative for basic understanding, diagnosis, and prognosis of metastatic cancers. The biology and clinical values of exosomes are under intensive investigation, yet most studies are limited by technical challenges in recovering these exosomes with heterogeneous sizes and...

Invasive spread of glioblastoma (GBM) is linked to changes in chondroitin sulfate (CS) proteoglycan (CSPG)‐associated sulfated glycosaminoglycans (GAGs) that are selectively up‐regulated in the tumor microenvironment (TME). We hypothesized that inhibiting CS‐GAG signaling in the TME would stem GBM invasion. Rat F98 GBM cells demonstrated enhanced p...

Four inter-related measures of phase are described to study the phase synchronization of cellular oscillators, and computation of these measures is described and illustrated on single cell fluorescence data from the model filamentous fungus, Neurospora crassa. One of these four measures is the phase shift ϕ in a sinusoid of the form x(t) = A(cos(ωt...

Using a microfluidics device, fluorescence of a recorder (mCherry or mVenus) gene driven by a clock-controlled gene-2 promoter ( ccg-2p ) was measured simultaneously on over 1000 single cells of Neurospora crassa every half hour for 10 days under each of varied light and temperature conditions. Single cells were able to entrain to light over a...

Isolation of circulating tumor cells (CTCs) from blood provides a minimally-invasive alternative into the basic understanding, diagnosis and prognosis of metastatic cancers. The roles and clinical values of CTCs are under intensive investigation, yet most studies are limited by technical challenges in the comprehensive enrichment of intact and viab...

Isolation of exosomes from biological samples provides a minimally-invasive alternative for basic understanding, diagnosis, and prognosis of metastatic cancers. The biology and clinical values of exosomes are under intensive investigation, yet most studies are limited by technical challenges in recovering these exosomes with heterogeneous sizes and...

In article number 1800246, Yiping Zhao and co‐workers demonstrate a unique non‐contact single cell manipulation technique based on the actuation of magnetic nanorods or clusters by non‐uniform alternating magnetic fields. This single cell manipulation system is simple, involves low costs and power consumption, and helps advance the progress of sing...

A unique noncontact single cell manipulation technique based on the actuation of magnetic nanorods (MNRs) or clusters (MCs) by nonuniform alternating magnetic fields (nuAMFs) is demonstrated. Compared to the actuation of MNRs/MCs by conventional magnetophoresis, the motion of MNRs/MCs actuated by nuAMFs can be tuned by additional parameters includi...

Root hairs are lateral extensions of epidermal cells and constitute up to 60% of the root surface. If grown in abiotic stress conditions, such as phosphorous (P) and nitrogen (N) deficiency, root hairs show distinctive phenotypes that are linked to improved nutrient acquisition. These phenotypes are typically observed and evaluated after 1-2 weeks...

It is well-known that Ferromagnetic microrods form linear chains under an external uniform magnetic field B and the chain length is strongly dependent on the applied field, the applied time duration, and the microrod density. When the chains become long enough and the B-field switches to its orthogonal direction, an irreversible morphological trans...

A major challenge in systems biology is to infer the parameters of regulatory networks that operate in a noisy environment, such as in a single cell. In a stochastic regime it is hard to distinguish noise from the real signal and to infer the noise contribution to the dynamical behavior. When the genetic network displays oscillatory dynamics, it is...

Summary features of MCMC runs with parallel tempering for the 868 and 1591 single cell data sets. (DOCX)

Bar charts of the parameters from the macroscopic deterministic model (Table 2 in column 3) in blue and single cell stochastic model (Table 2 in column 6) in orange. Parameters are subdivided into: (A) decay rates; (B) transcription and translation rates; (C) interaction parameters between genes and their products on a log scale; (D) initial condit...

Fluoresecent data from a recorder downstream of a ccg-2 promoter from 1591 single cells stored in an excel file. Rows are different times, and columns are different cells. Time points are spaced at half-hour intervals over more than 11 days. (CSV)

Higher risk patient populations require continuous physiological monitoring and, in some cases, connected life-support systems, during magnetic resonance imaging examinations. While recently there has been a shift toward wireless technology, some of the magnetic resonance imaging devices are still connected to the outside using cabling that could i...

Droplet interface bilayer (DIB) networks allow for the construction of stimuli-responsive, membrane-based materials. Traditionally used for studying cellular transport phenomena, the DIB technique has proven its practicality when creating structured droplet networks. These structures consist of aqueous compartments capable of exchanging their conte...

Circulating tumor cells (CTCs) have significant implications in both basic cancer research and clinical applications. To address the limited availability of viable CTCs for fundamental and clinical investigations, effective separation...

We present a novel growth phenomenon in N. crassa identified using microfluidic technologies. N. crassa cells form a complex web-like network through hyphal extension, branching, and fusion. Our preliminary data indicate that after this filamentous network has been established, bursts of tree-like structures build upon these pre-existing network tr...

This paper reports a biocompatible and label-free cell separation method using ferrofluids that can separate a variety of low-concentration cancer cells from cell culture lines (~100 cancer cells/mL) from undiluted white blood cells, with a throughput of 1.2 mL/h and an average separation efficiency of 82.2%. The separation is based on size differe...

The synchronization of stochastic coupled oscillators is a central problem in physics and an emerging problem in biology, particularly in the context of circadian rhythms. Most measurements on the biological clock are made at the macroscopic level of millions of cells. Here measurements are made on the oscillators in single cells of the model funga...

A controlled configurational change of micro-clusters in suspensions is essential for many smart material applications. In this paper, the dynamic process of ferromagnetic microrod clusters (FMRCs) under an external magnetic field was studied as a function of the cluster size N and the applied field B. The FMRCs rearranged from a side-by-side raft-...

A fundamental problem in physics is measuring and modeling the synchronization of coupled stochastic oscillators. The problem is relatively recent in biology, where it has become possible to measure stochastic oscillators in single cells. A variety of synchronization measures have been proposed to describe a field of coupled stochastic oscillators....

Glioblastoma multiforme (GBM) is the most aggressive form of astrocytoma accounting for a majority of primary malignant brain tumors in the United States. Chondroitin sulfate proteoglycans (CSPGs) and their glycosaminoglycan (GAG) side chains are key constituents of the brain extracellular matrix (ECM) implicated in promoting tumor invasion. Howeve...

Manipulating particles and cells in magnetic liquids through "negative magnetophoresis" is a new research field. It has resulted in label-free and low-cost manipulation techniques in microfluidic systems and many exciting applications. It is the goal of this review to introduce the fundamental principles of negative magnetophoresis and its recent a...

The presented article discusses recent advances in biomedical applications of classical magnetohydrodynamics (MHD), with a focus on operating principles and associated material considerations. These applications address novel approaches to common biomedical problems from microparticle sorting for lab-on-a-chip devices to advanced physiological moni...

Microscopic medical robots capable of translating in a bloodstream or similar liquid represent a new type of therapeutic technology for surgical interventions. This study aims to characterize a new MRI compliant method of propulsion for swimming robots using the magnetohydrodynamic effect (MHD). An MHD drive is a method of propulsion employing only...

In this study, a label-free, low-cost, and fast ferrohydrodynamic cell separation scheme is demonstrated using HeLa cells (an epithelial cell line) and red blood cells. The separation is based on cell size difference, and conducted in a custom-made biocompatible ferrofluid that retains the viability of cells during and after the assay for downstrea...

This work explores incorporating ferrofluids with droplet interface bilayer (DIB) membranes. Ferrofluids contain magnetic nanoparticles in solution with a stabilizing surfactant, providing a magnetically-responsive fluid. These fluids allow for remote mechanical manipulation of ferrofluid droplets through magnetic fields, and will allow for better...

We report a novel magnetic field-assisted method for the fabrication and manipulation of non-spherical polymer particles within a ferrofluid-based droplet microfluidic device. Shape control and chain assembly of droplets with tunable lengths have been achieved.

A new separation method that combines both positive and negative magnetophoreses based on ferrofluids is used to separate mixtures of particles with different magnetic properties. Ferrofluids are stable magnetic nanoparticles suspensions. Under external magnetic field gradients, particles with a larger magnetization within the ferrofluids are attra...

This paper reports a new continuous-flow and label-free sorting scheme based on biocompatible ferrofluid hydrodynamics (ferrohydrodynamics) for the separation of mammalian cells (HeLa cells and mouse whole blood). Ferrofluids are stable magnetic nanoparticles suspensions used as sorting media in microfluidics for both particles and cells. Here we d...

We develop a simple and effective method that separates HeLa cells from human blood cells, and immediately extracts HeLa cells from ferrofluids into a buffer stream through laminar flow and negative magnetophoresis. The exposure time of cells in ferrofluids is estimated to be on the order of seconds, making it ideal for live mammalian cell manipula...

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 stoke 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 mol...

Embodiments of the present disclosure provide for devices, methods for forming non-spherical particles, and the like.

This paper reports a droplet microfluidic system that is capable of generating droplets, encapsulating cells, incubating cells, and measuring biological clock behavior via fluorescent signals on a large number of single cells simultaneously over a long period of time (∼48 hours).

We report a novel on-chip cell and droplet manipulation scheme using magnetic nanoparticles suspension (i.e., ferrofluids). The design and characterization of a size-based cell-sorting device are presented. Magnetic field-assisted fabrication and manipulation of non-spherical polymer particles within a ferrofluidic droplet device is also presented.

We present an analytical model that can predict the three-dimensional (3D) transport of non-magnetic particles in magnetic fluids inside a microfluidic channel coupled with permanent magnets. The magnets produce a spatially non-uniform magnetic field that gives rise to a magnetic buoyancy force on the particles. Resulting 3D trajectories of the par...

A new sorting scheme based on ferrofluid hydrodynamics (ferrohydrodynamics) was used to separate mixtures of particles and live cells simultaneously. Two species of cells, including Escherichia coli and Saccharomyces cerevisiae, as well as fluorescent polystyrene microparticles were studied for their sorting throughput and efficiency. Ferrofluids a...

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 experiment...

Appendix: Mathematical Treatment of the simulation of heating experiment.

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/m...

We report a novel on-chip microparticles focusing technique using stable magnetic nanoparticles suspension (i.e., ferrofluids). The principle of focusing is based on magnetic buoyancy forces exerted on non-magnetic particles within ferrofluids under non-uniform magnetic field. The design, modeling, fabrication, and characterization of the focusing...

This study describes an analytical model and experimental verifications of transport of non-magnetic spherical microparticles in ferrofluids in a microfluidic system that consists of a microchannel and a permanent magnet. The permanent magnet produces a spatially non-uniform magnetic field that gives rise to a magnetic buoyancy force on particles w...

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 gener...

Ferrofluids have a wide application potential in the field of biomedicine, including cellular manipulation and sorting, hyperthermia and targeted drug delivery. For such applications to be practical, the colloidal suspension of magnetic nanoparticles within a ferrofluid needs to be stable under physiological conditions. Current approaches that util...

We present a novel and label-free continuous flow non-magnetic microparticle separation scheme in a microfluidic device under static magnetic fields. The separation process is conducted inside water-based ferrofluids. We exploit the difference in particle sizes to achieve binary separation of microparticles with high throughput. We demonstrate size...

Surfaces containing reactive ester polymer brushes were functionalized with cyclopropenone-masked dibenzocyclooctynes for the light activated immobilization of azides using catalyst-free click chemistry. The photodecarbonylation reaction in the amorphous brush layer is first order for the first 45 s with a rate constant of 0.022 s(-1). The catalyst...

We present a simple, low-cost, effective, and label-free continuous flow non-magnetic microparticle separation scheme in a microfluidic device under static magnetic fields. The separation process is based on negative magnetophoresis and uses water-based ferrofluids. We exploit the difference in particle sizes to achieve continuous binary separation...

We present a simple microfluidic platform that uses biocompatible ferrofluids for the controlled manipulation and rapid separation of both microparticles and live cells. This low-cost platform exploits differences in particle size, shape, and elasticity to achieve rapid and efficient separation. Using microspheres, we demonstrate size-based separat...

In a previous work, we demonstrated that traveling wave excitations from integrated electrodes can continuously pump magnetic liquids within a microfluidic channel. The optimum excitation frequency of this pumping is strongly dependent on the hydrodynamic size of the magnetic nanoparticles, and the effect can be used to detect whenever a molecule o...

We report on the design, development, fabrication and characterization of a novel, micro-scale mixing device based on stable water suspensions of magnetic nanoparticles (i.e. ferrofluids). The micromixer prototypes are built using standard microfabrication and simple soft-lithography, and the design can be incorporated as a sub-system into any chem...

In this paper, we show that ferrofluids can be pumped very effectively in closed-channel geometries both in the macro- and micro-scales using spatially travelling, sinusoidally time-varying magnetic fields. The results from numerical modelling demonstrate that the optimum pumping frequency is the reciprocal of the Brownian relaxation time constant...

A novel ferrofluid micropump utilizing traveling magnetic fields is designed based on previous numerical analysis. A cost-effective fabrication process combining insulated metal substrate etching and soft lithography is used to realize the prototype ferrofluid micropump. Preliminary results show good agreement of pumping characteristics between the...

In this paper, we present a numerical method to simulate the dynamics of ferrofluids in spatially traveling, sinusoidally time-varying magnetic fields. Actuation using traveling waves involves magnetic body forces and torque on the magnetic moment of nanoparticles, both of which affect the overall pumping.

Ferrofluids are stable colloidal suspensions of nanosize ferromagnetic particles in either an aqueous or an oil-based solvent 1 . In the presence of a magnetic field gradient within a fer-rofluid, magnetic forces and torque are developed to drive magnetic particles, which subse-quently draw along the liquid solvent carrier. This allows continuous a...

We present the design, numerical analysis, fabrication and experimental investigation of an integrated, high flow rate ferrofluid micropump. The dynamics of ferrofluids in spatially-traveling, sinusoidally time-varying magnetic fields is simulated. A prototype ferrofluid micropump is designed and fabricated based on the numerical simulations. Preli...

A study of ferrohydrodynamics under traveling magnetic field excitations