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.

G-Fresnel smartphone spectrometer.

We report a smartphone spectrometer with nanometer resolution working in the visible range. A G-Fresnel device with the dual functionality of focusing and dispersion is used to enable miniaturization. Proof of principle application to Bradford assay of protein concentration is also demonstrated.

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.

Separable bilayer microfiltration device for viable label-free enrichment of circulating tumour cells.

The analysis of circulating tumour cells (CTCs) in cancer patients could provide important information for therapeutic management. Enrichment of viable CTCs could permit performance of functional analyses on CTCs to broaden understanding of metastatic disease. However, this has not been widely accomplished. Addressing this challenge, we present a separable bilayer (SB) microfilter for viable size-based CTC capture. Unlike other single-layer CTC microfilters, the precise gap between the two layers and the architecture of pore alignment result in drastic reduction in mechanical stress on CTCs, capturing them viably. Using multiple cancer cell lines spiked in healthy donor blood, the SB microfilter demonstrated high capture efficiency (78-83%), high retention of cell viability (71-74%), high tumour cell enrichment against leukocytes (1.7-2 × 10(3)), and widespread ability to establish cultures post-capture (100% of cell lines tested). In a metastatic mouse model, SB microfilters successfully enriched viable mouse CTCs from 0.4-0.6 mL whole mouse blood samples and established in vitro cultures for further genetic and functional analysis. Our preliminary studies reflect the efficacy of the SB microfilter device to efficiently and reliably enrich viable CTCs in animal model studies, constituting an exciting technology for new insights in cancer research.

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 m(2) 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.

Flexible micro spring array device for high-throughput enrichment of viable circulating tumor cells.

BACKGROUND: The dissemination of circulating tumor cells (CTCs) that cause metastases in distant organs accounts for the majority of cancer-related deaths. CTCs have been established as a cancer biomarker of known prognostic value. The enrichment of viable CTCs for ex vivo analysis could further improve cancer diagnosis and guide treatment selection. We designed a new flexible micro spring array (FMSA) device for the enrichment of viable CTCs independent of antigen expression. METHODS: Unlike previous microfiltration devices, flexible structures at the micro scale minimize cell damage to preserve viability, while maximizing throughput to allow rapid enrichment directly from whole blood with no need for sample preprocessing. Device performance with respect to capture efficiency, enrichment against leukocytes, viability, and proliferability was characterized. CTCs and CTC microclusters were enriched from clinical samples obtained from breast, lung, and colorectal cancer patients. RESULTS: The FMSA device enriched tumor cells with 90% capture efficiency, higher than 10(4) enrichment, and better than 80% viability from 7.5-mL whole blood samples in <10 min on a 0.5-cm(2) device. The FMSA detected at least 1 CTC in 16 out of 21 clinical samples (approximately 76%) compared to 4 out of 18 (approximately 22%) detected with the commercial CellSearch® system. There was no incidence of clogging in over 100 tested fresh whole blood samples. CONCLUSIONS: The FMSA device provides a versatile platform capable of viable enrichment and analysis of CTCs from clinically relevant volumes of whole blood.

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 10(4) enrichment, and better than 80% viability in approximately ten minutes without any incidence of clogging.

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.

Extraction of naringin from pomelo peels as dihydrochalcone's precursor.

A new method for the separation of naringin from pomelo peels was investigated by using ultrasonic-assisted extraction and macroporous resin purification technology. The ultrasonic extraction efficiency was dependent on agent's concentration, ratio of sample and solvent and ultrasonic time. Several parameters of macroporous resin-purified process, including resin selection, initial concentration, concentration of eluted agent and pH, were optimized. The experimental results showed that the naringin content in the mature pomelo peels was 2.20% and purification rate of naringin was 77.26% under optimum conditions of purification. The structure of synthetic naringin dihydrochalcone was determined by a series of spectroscopic methods, such as UV, NMR and MS.