Ming-Da Zhou

Facile synthesis of magnetic mesoporous hollow carbon microspheres for rapid capture of low-concentration peptides.

Mesoporous and hollow carbon microspheres embedded with magnetic nanoparticles (denoted as MHM) were prepared via a facile self-sacrificial method for rapid capture of low-abundant peptides from complex biological samples. The morphology, structure, surface property, and magnetism were well-characterized. The hollow magnetic carbon microspheres have a saturation magnetization value of 130.2 emu g–1 at room temperature and a Brunauer–Emmett–Teller specific surface area of 48.8 m2 g–1 with an average pore size of 9.2 nm for the mesoporous carbon shell. The effectiveness of these MHM affinity microspheres for capture of low-concentration peptides was evaluated by standard peptides, complex protein digests, and real biological samples. These multifunctional hollow carbon microspheres can realize rapid capture and convenient separation of low-concentration peptides. They were validated to have better performance than magnetic mesoporous silica and commercial peptide-enrichment products. In addition, they can be easily recycled and present excellent reusability. Therefore, it is expected that this work may provide a promising tool for high-throughput discovery of peptide biomarkers from biological samples for disease diagnosis and other biomedical applications.

An implantable Fabry-Pérot pressure sensor fabricated on left ventricular assist device for heart failure

Continuous flow left ventricular assist devices (LVADs) are commonly used as bridge-to-transplantation or destination therapy for heart failure patients. However, non-optimal pumping speeds can reduce the efficacy of circulatory support or cause dangerous ventricular arrhythmias. Optimal flow control for continuous flow LVADs has not been defined and calls for an implantable pressure sensor integrated with the LVAD for real-time feedback control of pump speed based on ventricular pressure. A MEMS pressure sensor prototype is designed, fabricated and seamlessly integrated with LVAD to enable real-time control, optimize its performance and reduce its risks. The pressure sensing mechanism is based on Fabry-Pérot interferometer principle. A biocompatible parylene diaphragm with a silicon mirror at the center is fabricated directly on the inlet shell of the LVAD to sense pressure changes. The sensitivity, range and response time of the pressure sensor are measured and validated to meet the requirements of LVAD pressure sensing.

On-demand one-step synthesis of monodisperse functional polymeric microspheres with droplet microfluidics.

A simple and robust method for one-step synthesis of monodisperse functional polymeric microspheres was established by generation of reversed microemulsion droplets in aqueous phase inside microfluidic chips and controlled evaporation of the organic solvent. Using this method, water-soluble nanomaterials can be easily encapsulated into biodegradable Poly(D,L-lactic-co-glycolic acid) (PLGA) to form functional microspheres. By controlling the flow rate of microemulsion phase, PLGA polymeric microspheres with narrow size distribution and diameters in the range of ∼50-100 μm were obtained. As a demonstration of the versatility of the approach, high-quality fluorescent CdTe:Zn(2+) quantum dots (QDs) of various emission spectra, superparamagnetic Fe3O4 nanoparticles, and water-soluble carbon nanotubes (CNTs) were used to synthesize fluorescent PLGA@QDs, magnetic PLGA@Fe3O4, and PLGA@CNTs polymeric microspheres, respectively. In order to show specific applications, the PLGA@Fe3O4 were modified with polydopamine (PDA), and then the silver nanoparticles grew on the surfaces of the PLGA@Fe3O4@PDA polymeric microspheres by reducting the Ag(+) to Ag(0). The as-prepared PLGA@Fe3O4@PDA-Ag microspheres showed a highly efficient catalytic reduction of the 4-nitrophenol, a highly toxic substance. The monodisperse uniform functional PLGA polymeric microspheres can potentially be critically important for multiple biomedical applications.

Preparation of magnetic graphene composites with hierarchical structure for selective capture of phosphopeptides

A novel graphene composite affinity material consisting of graphene scaffold, Fe3O4 nanoparticles for actuation and fully covered porous titania nanostructures as affinity coating has been designed and constructed. The obtained magnetic graphene composites have a saturation magnetization (Ms) value of 7.3 emu g-1, a BET specific surface area of 111.8 m2 g-1 and an average pore size of 15.1 nm for the porous affinity coating. The multifunctional graphene composites can realize the selective capture and convenient magnetic separation of target phosphopeptides by taking advantage of the decorated magnetic nanoparticles, highly pure and well crystallized affinity coating, and unique porous structure. Sensitivity and selectivity of the affinity graphene composites were evaluated using digests of standard proteins and complex biosamples as well as by comparison with the widely used TiO2 affinity microspheres. The results show that the affinity graphene composites can realize selective capture and rapid separation of low-abundance phosphopeptides from complex biological samples. Thus, this work will contribute to future applications in the purification and separation of specific biomolecules, in particular, low-abundance phosphopeptide biomarkers.

Abstract 5214: Development of a microfiltration system for the improved detection and viable capture of metastatic circulating tumor cells

The ability of metastatic cancer to release cells that travel through the circulatory system and invade different parts of the body accounts for over 90% of cancer related deaths. The fundamental challenge with detecting these circulating tumor cells (CTCs) in blood samples is the fact that they are so rare, with only a few tumors cells occurring among billions of blood cells. Since tumor cells are almost always significantly larger and more rigid than normal blood cells, size based separation has been demonstrated to be an effective method for CTC capture and enrichment. While useful for detection, size based techniques apply concentrated stresses that affect the viability of captured cells. We have incorporated novel spring structures into our microfilter design that mitigate the stresses experienced by CTCs during filtration to encourage their health and survival. The geometric design and filtration pressures have been optimized to maximize capture efficiency, enrichment against white blood cells, and tumor cell viability. This was achieved through repeated filtrations using a model system of fluorescently labeled cells from various established tumor cell lines spiked into healthy donor blood. The viability of captured cells has been confirmed through exclusion dye testing, and through the proliferation and culture of captured cells directly on the filter surface. The successful capture and primary culture of viable CTCs from clinical patient samples will allow unprecedented analysis and genetic testing of the cells directly responsible for metastasis. This could provide the basis for externally testing tumor cell response to a variety of anticancer drugs without having to expose a patient to the unnecessary cost and toxic effects of chemotherapy, thereby improving patient outcomes through the development of personalized treatment plans. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5214. doi:10.1158/1538-7445.AM2011-5214

Clinical translation of a novel microfilter technology Capture, characterization and culture of circulating tumor cells

The most important determinant of prognosis and management of cancer is the presence or absence of metastasis [1]. The road to metastasis involves tumor cells to become detached from the primary tumor and travel in the blood to distant sites, causing secondary tumors. These tumor cells traveling in blood are termed Circulating tumor cells (CTC). Capture of CTC from whole blood has been a challenging feat. The fact that these CTC are few in number, to effectively and efficiently isolate them from whole blood can be thought of as looking for a needle in a haystack. Our microfilter technology exploits the use of size based capture of the larger CTC from the smaller white blood cells and components of whole blood. The effective capture potential of the microfilter platform has driven the area of CTC analysis into a new age of research in the field of cancer. The ability to finally analyze CTC at a molecular level, leads to a deeper understanding of metastatic process, while providing an opportunity to evaluate, monitor and manage treatment options as well as the adherent possibility of having an “on-chip” drug sensitivity assay for focused treatment options. We have demonstrated through clinical trials the ability to effectively identify, enumerate and characterize CTC based on immunfluorescence and FISH assays and provide a companion endpoint for monitoring and evaluating treatment management. Our work on viable CTC capture has resulted in successfully capturing and culturing CTC from blood in mouse models that have been inoculated with breast cancer cell lines to form primary and secondary metastatic cancer sites. The future potential within the microfilter technology to capture viable CTC for culture, will catapult therapeutic interventions to a new level of personalized medicine in cancer management.

Viable circulating tumor cell enrichment by flexible micro spring array

We demonstrated a high throughput versatile platform capable of isolating circulating tumor cells (CTCs) from clinically relevant volumes of blood while preserving their viability and ability to proliferate. The enrichment is based on the fact that CTCs are larger compared with normal blood cells. The incorporated system allows size-based separation of CTCs at the micro-scale, while taking advantage of a high throughput and rapid processing speed. Testing results of model systems using cell lines show that this device can enrich CTCs from 7.5 mL of whole blood samples with 90% capture efficiency, higher than 104 enrichment, and better than 80% viability in approximately ten minutes without any incidence of clogging.

Z-microscopy for parallel axial imaging with micro mirror array

We propose and demonstrate a method of “z-microscopy” by utilizing an array of 45°-tilted micro mirrors arranged along the axial direction. Image signals emitted from different axial positions can be orthogonally reflected by the corresponding micro mirrors and spatially separated for parallel detection, essentially converting the more challenging axial imaging to a lateral imaging problem. Each micro mirror also provides optical sectioning capability due to its finite dimension. Numerical analysis shows that nearly diffraction limited axial resolution can be achieved. Experimental demonstration of z-imaging of fluorescent microspheres is also presented.

Chopper-modulated gas chromatography electroantennography enabled using high-temperature MEMS flow control device

We report the design, fabrication and characterization of a microelectromechanical systems (MEMS) flow control device for gas chromatography (GC) with the capability of sustaining high-temperature environments. We further demonstrate the use of this new device in a novel MEMS chopper-modulated gas chromatography-electroantennography (MEMS-GC-EAG) system to identify specific volatile organic compounds (VOCs) at extremely low concentrations. The device integrates four pneumatically actuated microvalves constructed via thermocompression bonding of the polyimide membrane between two glass substrates with microstructures. The overall size of the device is 32 mm×32 mm, and it is packaged in a 50 mm×50 mm aluminum housing that provides access to the fluidic connections and allows thermal control. The characterization reveals that each microvalve in the flow control chip provides an ON to OFF ratio as high as 1000:1. The device can operate reliably for more than 1 million switching cycles at a working temperature of 300 °C. Using the MEMS-GC-EAG system, we demonstrate the successful detection of cis-11-hexadecenal with a concentration as low as 1 pg at a demodulation frequency of 2 Hz by using an antenna harvested from the male Helicoverpa Virescens moth. In addition, 1 μg of a green leafy volatile (GLV) is barely detected using the conventional GC-EAG, while MEMS-GC-EAG can readily detect the same amount of GLV, with an improvement in the signal-to-noise ratio (SNR) of ~22 times. We expect that the flow control device presented in this report will allow researchers to explore new applications and make new discoveries in entomology and other fields that require high-temperature flow control at the microscale.

Abstract LB-193: Separable bilayer microfiltration device for viable label-free enrichment of circulating tumor cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA We designed a new separable bilayer (SB) microfiltration device for the viable enrichment of circulating tumor cells (CTCs) independent of antigen expression. Bilayer pore structures at the micro scale decrease cell damage to preserve viability, while maintaining throughput to allow rapid enrichment. The large pore size (40 um) of the upper layer facilitates the CTCs proliferation on chip. The separability enables the efficient release of the CTCs after successful on chip culture of captured CTCs. We characterized the device performances including capture efficiency, enrichment against leukocytes, viability and proliferability. The SB device can enrich tumor cells with 80% capture efficiency, higher than 103 enrichment, and better than 70% viability from 1 mL whole blood samples on a 1 cm2 device. Multiple cell lines were shown to be able to proliferate after captured on SB device. Furthermore, using CTCs derived from an in vivo model system, cell cultures were established by releasing the captured CTCs from the chip. The cultured CTCs and their corresponding parental cell lines were injected into mice. Tumors were established with no discernable differences in volume and rate of growth, demonstrating similar tumorigenicity of viable CTCs recovered by the SB device. In a feasibility study, we successfully detected CTCs from 1 mL of clinical whole blood sample enriched via SB device. Citation Format: Ming-Da Zhou, Sijie Hao, Anthony J. Williams, Bo Lv, Jiyue Zhu, Richard J. Cote, Ram H. Datar, Yu-Chong Tai, Siyang Zheng. Separable bilayer microfiltration device for viable label-free enrichment of circulating tumor cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-193. doi:10.1158/1538-7445.AM2014-LB-193