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BACKGROUND Colorectal cancer screening by fecal occult blood testing has been an important public health test and shown to reduce colorectal cancer–related mortality. However, the low participation rate in colorectal cancer screening by the general public remains a problematic public health issue. This fact could be attributed to the complex and unpleasant operation of the screening tool. OBJECTIVE This study aimed to validate a novel toilet paper–based point-of-care test (ie, JustWipe) as a public health instrument to detect fecal occult blood and provide detailed results from the evaluation of the analytic characteristics in the clinical validation. METHODS The mechanism of fecal specimen collection by the toilet-paper device was verified with repeatability and reproducibility tests. We also evaluated the analytical characteristics of the test reagents. For clinical validation, we conducted comparisons between JustWipe and other fecal occult blood tests. The first comparison was between JustWipe and typical fecal occult blood testing in a central laboratory setting with 70 fecal specimens from the hospital. For the second comparison, a total of 58 volunteers were recruited, and JustWipe was compared with the commercially available Hemoccult SENSA in a point-of-care setting. RESULTS Adequate amounts of fecal specimens were collected using the toilet-paper device with small day-to-day and person-to-person variations. The limit of detection of the test reagent was evaluated to be 3.75 µg of hemoglobin per milliliter of reagent. Moreover, the test reagent also showed high repeatability (100%) on different days and high reproducibility (>96%) among different users. The overall agreement between JustWipe and a typical fecal occult blood test in a central laboratory setting was 82.9%. In the setting of point-of-care tests, the overall agreement between JustWipe and Hemoccult SENSA was 89.7%. Moreover, the usability questionnaire showed that the novel test tool had high scores in operation friendliness (87.3/100), ease of reading results (97.4/100), and information usefulness (96.1/100). CONCLUSIONS We developed and validated a toilet paper–based fecal occult blood test for use as a point-of-care test for the rapid (in 60 seconds) and easy testing of fecal occult blood. These favorable characteristics render it a promising tool for colorectal cancer screening as a public health instrument.

Background This study examines whether the measurement of circulating epithelial cells (CECs) facilitates the identification and follow-up of a patient with thyroid cancer. Methods A 29-y-old woman with no cancer history was enrolled as a healthy control in a CEC study. CECs were enriched from the peripheral blood by the negative selection system PowerMag. Various medical examinations were performed on the patient to establish the diagnosis and to follow-up her disease status during treatment. Results This patient had unexpectedly high CEC counts that were sustained for more than two weeks. Thyroid gland ultra-sonography revealed lesions in the left lobe that could not be confirmed as cancer by magnetic resonance imaging, 18 F–fludeoxyglucose-positron emission tomography–computed tomography or cytopathological analysis, but were histologically confirmed after thyroidectomy as papillary thyroid microcarcinoma. Both the CEC count and serum thyroglobulin (Tg) concentration were significantly decreased after thyroidectomy, and they and the patient's disease status were correlated during remnant ablation therapy. The CEC count returned to normal when the patient was disease-free 10 months after thyroidectomy. Conclusions CEC testing facilitates the identification of individuals at risk for cancer. Longitudinal follow-up of the CEC count may complement serum Tg testing for monitoring the status of patients with thyroid cancer.

Background Colorectal cancer screening by fecal occult blood testing has been an important public health test and shown to reduce colorectal cancer–related mortality. However, the low participation rate in colorectal cancer screening by the general public remains a problematic public health issue. This fact could be attributed to the complex and unpleasant operation of the screening tool. Objective This study aimed to validate a novel toilet paper–based point-of-care test (ie, JustWipe) as a public health instrument to detect fecal occult blood and provide detailed results from the evaluation of the analytic characteristics in the clinical validation. Methods The mechanism of fecal specimen collection by the toilet-paper device was verified with repeatability and reproducibility tests. We also evaluated the analytical characteristics of the test reagents. For clinical validation, we conducted comparisons between JustWipe and other fecal occult blood tests. The first comparison was between JustWipe and typical fecal occult blood testing in a central laboratory setting with 70 fecal specimens from the hospital. For the second comparison, a total of 58 volunteers were recruited, and JustWipe was compared with the commercially available Hemoccult SENSA in a point-of-care setting. Results Adequate amounts of fecal specimens were collected using the toilet-paper device with small day-to-day and person-to-person variations. The limit of detection of the test reagent was evaluated to be 3.75 µg of hemoglobin per milliliter of reagent. Moreover, the test reagent also showed high repeatability (100%) on different days and high reproducibility (>96%) among different users. The overall agreement between JustWipe and a typical fecal occult blood test in a central laboratory setting was 82.9%. In the setting of point-of-care tests, the overall agreement between JustWipe and Hemoccult SENSA was 89.7%. Moreover, the usability questionnaire showed that the novel test tool had high scores in operation friendliness (87.3/100), ease of reading results (97.4/100), and information usefulness (96.1/100). Conclusions We developed and validated a toilet paper–based fecal occult blood test for use as a point-of-care test for the rapid (in 60 seconds) and easy testing of fecal occult blood. These favorable characteristics render it a promising tool for colorectal cancer screening as a public health instrument.

Single-cell electrical properties (e.g., specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm)) have been regarded as potential label-free biophysical markers for the evaluation of cellular status. However, whether there exist correlations between these biophysical markers and cellular status (e.g., membrane-associate protein expression) is still unknown. To further validate the utility of single-cell electrical properties in cell type classification, Cspecific membrane and σcytoplasm of single PC-3 cells with membrane staining and/or fixation were analyzed and compared in this study. Four subtypes of PC-3 cells were prepared: untreated PC-3 cells, PC-3 cells with anti-EpCAM staining, PC-3 cells with fixation, and fixed PC-3 cells with anti-EpCAM staining. In experiments, suspended single cells were aspirated through microfluidic constriction channels with raw impedance data quantified and translated to Cspecific membrane and σcytoplasm. As to experimental results, significant differences in Cspecific membrane were observed for both live and fixed PC-3 cells with and without membrane staining, indicating that membrane staining proteins can contribute to electrical properties of cellular membranes. In addition, a significant decrease in σcytoplasm was located for PC-3 cells with and without fixation, suggesting that cytoplasm protein crosslinking during the fixation process can alter the cytoplasm conductivity. Overall, we have demonstrated how to classify single cells based on cellular electrical properties.

This study reports an optically-induced dielectrophoretic (ODEP) force-based microfluidic platform for live and dead cell separation and collection. ODEP forces are used to separate the live and dead cells due to their opposite responses to an ODEP force. Combining the flow control in a microfluidic system, the live and dead cells can be separated and subsequently collected in an efficient and effective manner. The operating conditions of the ODEP force for manipulating the live and dead chondrocytes is characterized, and separation performance is experimentally evaluated. Results revealed that an applied voltage of 8 V resulted in a maximum difference of manipulation force for the live (49.4 pN) and dead (-20.1 pN) cells. Results of further separation experiments showed that the recovery rate and purity of the isolated live cells was as high as 78.3±6.8 % and 96.4 ±2.2 %, respectively. Overall, the proposed method is found to be particularly valuable for biological research which requires the isolation of highly pure live or dead cells.

OBJECTIVES To systematically and quantitatively summarise the current evidence on the utility of the procalcitonin test (PCT) in discriminating pulmonary tuberculosis (TB) from other pulmonary infections. METHODS We searched MEDLINE, EMBASE and the Cochrane database up to August 2013 for studies that reported the performance of PCT alone or compared with other biomarkers in diagnosing pulmonary TB. We summarised PCT using forest plots, hierarchical summary receiver operating characteristic curves and bivariate random effects models. RESULTS We found nine qualifying studies covering 951 episodes of suspected TB along with 426 confirmed TB cases. The bivariate pooled sensitivity and specificity of PCT to distinguish TB from non-TB were respectively 42% (95%CI 30-56) and 87% (95%CI 63-96). The bivariate pooled sensitivity and specificity for PCT in distinguishing TB from bacterial pneumonia were respectively 78% (95%CI 67-86) and 85% (95%CI 78-90). Low heterogeneity was noted in studies comparing TB with bacterial pneumonia patients. CONCLUSION The results suggest consistently acceptable sensitivity and specificity of the PCT test in distinguishing TB from bacterial pneumonia. However, given the imperfect sensitivity and specificity of the test, medical decisions should be based on both the PCT test results as well as on clinical findings.

a b s t r a c t This study reports a microfluidic platform for clogging-free electrical property analysis of single cells. A pneumatically driven membrane-based active valve was integrated in this platform to unblock clogging events of constriction microchannels where pneumatic pressures were used to tune the deformation of a polydimethylsiloxan (PDMS) membrane serving as one wall of the constriction microchannel. The proposed platform was first tested to unblock trapped polystyrene beads at the entrance of constriction microchannels and then the characterization of the cellular electrical properties of lung cancer cells was successfully demonstrated. Results showed that the measured cytoplasm conductivity (0.74 ± 0.20 S/m) and specific membrane capacitance (2.17 ± 0.58 F/cm2) of cells were consistent with the results from the previous publications (0.73 ± 0.17 S/m, and 2.00 ± 0.60 F/cm 2 , respectively). Overall, this study has presented a microfluidic platform for single cell analysis with an enhanced function for unblocking cell aggregates at the entrance of microchannels.

This study reports a piezoelectric polyvinylidene fluoride (PVDF) polymer-based sensor patch for simultaneous heartbeat and respiration detections. The principle is based on the piezoelectric sensing mechanism to detect the pulsatile vibrations, and periodical deformations on the chest wall of human body during heartbeats and respirations, respectively. In this study, the sensor patch with a structurally curved PVDF film was designed, and fabricated. The role of the curved structure design to enhance detection signals, and the capability of the sensor to faithfully detect the heartbeats and respirations were experimentally evaluated. Results revealed that the design of curved structure of PVDF film was capable of increasing detection signal by 151% for the respiration measurements compared with its flat counterpart. Moreover, the sensor was proved to be able to generate the heartbeat and respiration signals which were in concordance with those based on a commercial electrocardiogram (ECG), and respiratory effort transducer, respectively. Finally, the heart rate and respiratory rate measured through the sensor patch were proved to have no statistical significance compared with the reference data obtained from the ECG, and respiratory effort transducer-based detections, respectively. As a whole, this study has developed a PVDF-based sensor patch which was capable of monitoring the heartbeats and respirations with high fidelity. Other distinctive features include its small size, light weight, ease of use, low cost, and portability. All these make it a promising sensing device to monitor heartbeats and respirations either in medical centers, or home care units.

Mechanical compression plays an important role in modulating cell physiology. To precisely investigate the cellular response to compression, a stable culture condition is required. In this study, we developed a microbioreactor platform capable of providing dynamic compressive loading to the 3-D cell culture constructs under a steady environment. The mechanism of generating compression stimulation to cells is based on the pneumatically-driven deformation of a polydimethylsiloxane (PDMS) membrane, which then exerts compressive loading to the cultured cells through a micropillar. By modulating the magnitude and frequency of the applied pneumatic pressure, the compressive loading can be generated in a tunable manner. In this study, the quantitative relationship between the applied pneumatic pressure and the generated compressive strain on the culture construct was established. Moreover, the effects of compression on the cell viability and the metabolic and biosynthetic activities of articular chondrocytes were investigated. The results disclosed that the dynamic compressive loading (51.3% strain, 1 Hz) might up-regulate the metabolic activity and glycosaminoglycan biosynthesis of articular chondrocytes after 5 day culture. Overall, this study presents a micro cell culture device that is capable of exploring the effects of compressive loading on cell physiology in a precise, high-throughput, low-cost, and user-friendly manner.

This study reports a new perfusion-based, micro three-dimensional (3-D) cell culture platform for high-throughput cell culture using enabling microfluidic technologies. In this work, the micro 3-D cell culture platform is fabricated based on SU-8 lithography and polydimethylsiloxane replication processes. The micro cell culture platform can maintain homogenous and stable culture environments, as well as provide pumping of multiple mediums and efficient cell/agarose (scaffold) loading functions, which allows realization of more precise and high-throughput cell culture-based assays. In this study, the design of a high-throughput medium pumping mechanism was especially highlighted. A new serpentine-shaped pneumatic micropump was used to provide the required medium pumping mechanism. Pneumatic microchannels with a varied length and U-shape bending corners were designed to connect three rectangular pneumatic chambers such that one can fine-tune the pumping rate of the S-shape micropump by using the fluidic resistance. To achieve a high-throughput medium pumping function, a pneumatic tank was designed to simultaneously activate all of the 30 pneumatic micropumps with a uniform pumping rate. Results show that the pumping rates of the 30 integrated micropumps were statistically uniform with a flow rate ranging from 8.5 to 185.1 microl h(-1), indicating the present multiple medium pumping mechanism is feasible for high-throughput medium delivery purposes. Furthermore, as a demonstration case study, 3-D culture of oral cancer cell was successfully performed, showing that the cell viability remained as high as 95% - 98% during the 48 h cell culture. As the result of miniaturization, this perfusion-based 3-D cell culture platform not only provides a well-defined and stable culture condition, but also greatly reduces the sample/reagent consumption and the need for human intervention. Moreover, due to the integrated capability for multiple medium pumping, high-throughput research work can be achieved. These traits are found particularly useful for high-precision and high-throughput, 3-D cell culture-based assay.

The mechanical behavior of biological cells is largely determined by their cytoskeletons; abnormal cellular functions can change cytoskeletons, leading to variations in cellular mechanical properties. This chapter begins with a summary of the relationships between cellular mechanical properties and various disease processes and changes in cell states: (1) changes in stiffness of red blood cells in cytoskeletal disorders, such as malaria and sickle cell anemia; (2) increased cell deformability of invasive cancer cells, compared with benign counterparts; (3) increased stiffness of leukocytes in sepsis; and (4) decreased deformability during the stem cell differentiation process. In the following section, we discuss the well-established techniques that are being used to measure the mechanical properties of single cells, including atomic force microscopy and micropipette aspiration. Finally, we describe the microfluidic approaches—including microfluidic constriction channels, microfluidic optical stretchers, and microfluidic hydrodynamic stretchers—that are being developed as next-generation, automated, and high-throughput techniques for characterization of the mechanical properties of single cells. The advantages and limitations of each technique are compared and future research opportunities are highlighted.

This study reports a new microfluidic device for continuous generation of alginate microbeads. The working mechanism is based on the use of a pneumatically driven micro-vibrator to continuously generate tiny alginate microdroplets into a thin oil layer. The temporarily formed alginate microdroplets soon sink into a sterile calcium chloride solution to form jelled microbeads. By regulating the flow rate of the alginate suspension and the pulsing frequency of the micro-vibrator, the size of the alginate microbeads can be controlled. Experimental results showed that alginate microbeads with sizes ranging from 73 to 302 μm in diameter can be generated at suspension flow rates and vibration frequency ranges of 1.48–9.35 μl/min and 2–16 Hz, respectively. For the aforementioned parameter ranges, the alginate microbeads had reasonable size uniformity with coefficients of variation from 3.8% to 7.8%. Moreover, its application for the microencapsulation of chondrocytes in alginate microbeads has also been demonstrated with high cell viability (94 ± 2%). As a whole, the proposed device has opened up a route to generate alginate microbeads or microencapsulation of cells in a simple, continuous, controllable, uniform, and cell-friendly manner with less contamination.

This study reports a new microfluidic-based filter for size-tunable separation of microbeads or cells. The filtration separation mechanism is based on the pneumatically tunable deformation of poly-dimethylsiloxane (PDMS) membranes, which block the fluid channel with a varied degree. This defines the dimensions of the open area of the fluid channel and thus determines the maximum diameter the microbeads or cells which can pass through. The proposed device incorporates pneumatic micropumps for automatic liquid handling. Another unique feature of this filter is an unclogging mechanism using a back-flush operating mode, by which a reverse-directional flow is utilized to flush the clogged filter zone. The separation performance of the proposed device has been experimentally evaluated. Results show that this developed device is able to provide precise size-dependent filtration, with a high passage efficiency (82–89%) for microbeads with sizes smaller than the defined void space in the filter zone. Also, the proposed separation mechanism is also capable of providing a reasonable filtration rate (14.9–3.3 μl/min). Furthermore, the separation of chondrocytes from a 30 μl suspension of enzymatically digested tissue is successfully demonstrated, showing an excellent cell passage efficiency of 93% and a cell viability of 96%. The proposed device is therefore capable of performing cell separation in situations where either the harvested specimen is limited or the sample cell content is sparse. It also paves a new route to delicately separate or to isolate cells in a simple and controllable manner.

This study reports a new microfluidic cell culture platform for real-time, in vitro microscopic observation and evaluation of cellular functions. Microheaters, a micro temperature sensor, and micropumps are integrated into the system to achieve a self-contained, perfusion-based, cell culture microenvironment. The key feature of the platform includes a unique, ultra-thin, culture chamber with a depth of 180 mum, allowing for real-time, high-resolution cellular imaging by combining bright field and fluorescent optics to visualize nanoparticle-cell/organelle interactions. The cell plating, culturing, harvesting and replenishing processes are performed automatically. The developed platform also enables drug screening and real-time, in situ investigation of the cellular and sub-cellular delivery process of nano vectors. The mitotic activity and the interaction between cells and the nano drug carriers (conjugated quantum dots-epirubicin) are successfully monitored in this device. This developed system could be a promising platform for a wide variety of applications such as high-throughput, cell-based studies and as a diagnostic cellular imaging system.

Before microfluidic-based cell culture models can be practically utilized for bioassays, there is a need for a transitional cell culture technique that can improve conventional cell culture models. To address this, a hybrid cell culture system integrating an active cover lid and a multi-well microplate was proposed to achieve perfusion 3-D cell culture. In this system, a microfluidic-based pneumatically-driven liquid transport mechanism was integrated into the active cover lid to realize 6-unit culture medium perfusion. Experimental results revealed that the flow of culture medium could be pneumatically driven in a flow-rate uniform manner. We used the system to successfully perform a perfusion 3-D cell culture of mesenchymal stem cells (MSCs) for up to 16 days. Moreover, we investigated the effects of various cell culture models on the physiology of MSCs. The physiological nature of MSCs can vary with respect to the cell culture model used. Using the perfusion 3-D cell culture format might affect the proliferation and osteogenic differentiation of MSCs. Overall, we have developed a cell culture system that can achieve multi-well microplate-based perfusion 3-D cell culture in an efficient, cost-effective and user-friendly manner. These features could facilitate the widespread application of perfusion cell culture models for cell-based assays.

This study presents a new pneumatic micropump featuring three membrane-enclosed air chambers with different volumes, such that serially connected actuation of these membranes can generate fluid movement. When compressed air fills the chambers, the membranes are pushed downward sequentially, resulting in the liquid in the underlying fluid channels being pumped forward peristaltically. Since the chambers are filled up sequentially with compressed air, from the smallest to largest chamber, this time delay generates a peristaltic motion in the membranes and forces the liquids to flow only along one direction. The pneumatic micropump is made of polydimethylsiloxane (PDMS) using soft lithography techniques. When compared with other pneumatic micropumps that usually require at least three electromagnetic valves (EMV), this new micropump can be operated by using a single EMV. Experimental results show that the micropump provides good performance even at low flow rates. The back pressure of the pneumatic micropump is measured at a fixed peak frequency to demonstrate the functionality of the micropump. The optimum operating conditions and geometric parameters of the micropump are systematically explored. A maximum flow of 108 µl min−1 is obtained at a driving frequency of 10 Hz and an air pressure of 25 psi (172.4 kPa) when a membrane with a thickness of 80 µm and a microchannel with a width of 500 µm are tested. The development of these micropumps could be crucial for automatic miniature biomedical and chemical analysis systems.

This study reports a microfluidic system for high throughput, uniform, and size-tunable generation of cell-containing collagen microbeads. The principle is based on two pneumatically-driven mechanisms to achieve multi-channel mixture suspension transportation, and to actuate the spotting actions of micro-vibrators that continuously generate tiny collagen micro-droplets into a thin oil layer and then a sterile Pluronic® F127 surfactant solution located below. The temporarily formed collagen microdroplets are then thermally gelatinized. By regulating the feeding rate of cells/collagen suspension, and the spotting frequency of micro-vibrator, the size of the collagen microbeads can be manipulated. One of the key technical features is its capability to generate uniform collagen microbeads (coefficient of variation: 5.4–8.6 %) with sizes ranging from 73.9 to 349.3 μm in diameter. This is currently difficult to achieve using the existing methods particularly the generation of cell-encapsulating collagen microbeads with diameter less than 100 μm. Another advantageous trait is that the ultrastructure of the generated collagen microbeads is similar to that found in native collagen. In this study, moreover, the use of the proposed device for the microencapsulation of 3T3 cells in collagen microbeads has been successfully demonstrated showing that the encapsulated cells maintained high cell viability (96 ± 2 %). Furthermore, a reasonable proliferative capability of the encapsulated cells was observed during 7 days culture. As a whole, the proposed device has opened up a new route to generate cell-containing collagen microbeads, which is found particularly meaningful for biomedical applications.

Compressive stimulation can modulate articular chondrocyte functions. Nevertheless, the relevant studies are not comprehensive. This is primarily due to the lack of cell culture apparatuses capable of conducting the experiments in a high throughput, precise, and cost-effective manner. To address the issue, we demonstrated the use of a perfusion microcell culture system to investigate the stimulating frequency (0.5, 1.0, and 2.0 Hz) effect of compressive loading (20% and 40% strain) on the functions of articular chondrocytes. The system mainly integrates the functions of continuous culture medium perfusion and the generation of pneumatically-driven compressive stimulation in a high-throughput micro cell culture system. Results showed that the compressive stimulations explored did not have a significant impact on chondrocyte viability and proliferation. However, the metabolic activity of chondrocytes was significantly affected by the stimulating frequency at the higher compressive strain of 40% (2 Hz, 40% strain). Under the two compressive strains studied, the glycosaminoglycans (GAGs) synthesis was upregulated when the stimulating frequency was set at 1 Hz and 2 Hz. However, the stimulating frequencies explored had no influence on the collagen production. The results of this study provide useful fundamental insights that will be helpful for cartilage tissue engineering and cartilage rehabilitation.

This paper presents a microfluidic system enabling continuous characterization of specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm) of single cells by aspirating cells continuously through a constriction channel with cell elongations and impedance profiles at two frequencies (1 kHz and 100 kHz) measured simultaneously. 1 kHz impedance data were used to evaluate cellular sealing properties and 100 kHz impedance data were used to quantify membrane capacitance and cytoplasm conductance, which were than translated to Cspecific membrane and σcytoplasm based on the proposed equivalent circuit model. Four cell lines were used to evaluate this technique, producing Cspecific membrane and σcytoplasm of 3.81±0.90 μF/cm2 and 0.49±0.07 S/m (CRL-5803, n=489), 4.28±1.05 μF/cm2 and 0.45±0.08 S/m (CCL-185, n=487), 3.67±1.00 μF/cm2 and 0.47±0.09 S/m (CRL-1932, n=302), as well as 4.53±1.51 μF/cm2 and 0.55±0.14 S/m (CRL-1999, n=216), respectively.

This paper presents a microfluidic system enabling cell type classification based on continuous characterization of size-independent electrical properties (e.g., specific membrane capacitance (C(specific membrane)) and cytoplasm conductivity (σ(cytoplasm)). In this study, cells were aspirated continuously through a constriction channel, while cell elongation and impedance profiles at two frequencies (1 kHz and 100 kHz) were measured simultaneously. Based on a proposed distributed equivalent circuit model, 1 kHz impedance data were used to evaluate cellular sealing properties with constriction channel walls and 100 kHz impedance data were translated to C(specific membrane) and σ(cytoplasm). Two lung cancer cell lines of CRL-5803 cells (n(cell) = 489) and CCL-185 cells (n(cell) = 487) were used to evaluate this technique, producing a C(specific membrane) of 1.63 ± 0.52 μF cm(-2) vs. 2.00 ± 0.60 μF cm(-2), and σ(cytoplasm) of 0.90 ± 0.19 S m(-1)vs. 0.73 ± 0.17 S m(-1). Neural network-based pattern recognition was used to classify CRL-5803 and CCL-185 cells, producing success rates of 65.4% (C(specific membrane)), 71.4% (σ(cytoplasm)), and 74.4% (C(specific membrane) and σ(cytoplasm)), suggesting that these two tumor cell lines can be classified based on their electrical properties.

This paper presents a microfluidic system enabling continuous characterization of specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm) of single biological cells. In this study, cells were aspirated through a constriction channel while cell elongations and impedance profiles at 1 kHz and 100 kHz were measured simultaneously using microscopy imaging and a lock-in amplifier. Based on the proposed equivalent circuit model, raw data were translated to Cspecific membrane and σcytoplasm, which were 3.67±1.00 vs. 4.53±1.51 μF/cm2 and 0.47±0.09 vs. 0.55±0.14 S/m for the kidney tumor cell line of 786-O (n=302) and the vascular smooth muscle cell line of T2 (n=216), respectively.

This study reports a piezoelectric polyvinylidene fluoride (PVDF) polymer-based sensor patch for simultaneous heartbeat and respiration detections. The principle is based on the piezoelectric sensing mechanism to detect the pulsatile vibrations, and periodical deformations on the chest wall of human body during heartbeats and respirations, respectively. In this study, the sensor patch with a structurally curved PVDF film was designed, and fabricated. The role of the curved structure designed to enhance detection signals, and the capability of the sensor to faithfully detect the heartbeats and respirations were experimentally evaluated. Results revealed that the sensor was proved to be able to generate the heartbeat and respiration signals which were in concordance with those based on a commercial electrocardiogram (ECG), and respiratory effort transducer, respectively. As a whole, this study has developed a PVDF-based sensor patch which was capable of monitoring the heartbeats and respirations with high fidelity. Other distinctive features include its small size, light weight, ease of use, low cost, and portability. All these make it a promising sensing device to monitor heartbeats and respirations either in medical centers, or home care units.

This paper presents a microfluidic system enabling continuous characterization of specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm) of single cells in suspension. In this study, cells were aspirated continuously through a constriction channel while cell elongations and impedance profiles at two frequencies (1kHz and 100kHz) were measured simultaneously using microscopy imaging and a lock-in amplifier. 1kHz impedance data were used to evaluate cellular sealing properties with constriction channel walls and 100kHz impedance data were translated to quantify equivalent membrane capacitance and cytoplasm resistance of single cells, which were further translated to Cspecific membrane and σcytoplasm. Two model cell lines (kidney tumor cell line of 786-O (n=302) and vascular smooth muscle cell line of T2 (n=216)) were used to evaluate this technique, producing Cspecific membrane of 3.67±1.00 and 4.53±1.51μF/cm(2) and σcytoplasm of 0.47±0.09 and 0.55±0.14S/m, respectively. Compared to previously reported techniques which can only collect Cspecific membrane and σcytoplasm from tens of cells, this new technique has a higher throughput, capable of collecting Cspecific membrane and σcytoplasm from hundreds of cells in 30min immediately after cell passage.

This study reports a cell culture platform consisting of 48 microbioreactors for high-throughput perfusion three-dimensional (3-D) cell culture-based assays. Its main characteristics are the capability of conducting multiplex backflow-free medium delivery, and the function for both efficient and high-throughput micro-scale 3-D cell culture construct loading. In addition, a micro-scale perfusion 3-D cell culture-based assay was successfully demonstrated using the proposed cell culture chip. The experimental results were also compared with the same evaluation based on conventional static 3-D cell culture with a larger culture scale. It can be concluded that the choice of the cell culture format can bring different assay results. Therefore, because of the inherent natures of miniaturized perfusion 3-D cell culture, the cell culture chip not only can provide stable, well-defined and more biologically-relevant culture environments, but it also features in low consumption of research resource.

In pharmaceutical research, an adequate cell-based assay scheme to efficiently screen and to validate potential drug candidates in the initial stage of drug discovery is crucial. In order to better predict the clinical response to drug compounds, a cell culture model that is faithful to in vivo behavior is required. With the recent advances in microfluidic technology, the utilization of a microfluidic-based cell culture has several advantages, making it a promising alternative to the conventional cell culture methods. This review starts with a comprehensive discussion on the general process for drug discovery and development, the role of cell culture in drug research, and the characteristics of the cell culture formats commonly used in current microfluidic-based, cell-culture practices. Due to the significant differences in several physical phenomena between microscale and macroscale devices, microfluidic technology provides unique functionality, which is not previously possible by using traditional techniques. In a subsequent section, the niches for using microfluidic-based cell culture systems for drug research are discussed. Moreover, some critical issues such as cell immobilization, medium pumping or gradient generation in microfluidic-based, cell-culture systems are also reviewed. Finally, some practical applications of microfluidic-based, cell-culture systems in drug research particularly those pertaining to drug toxicity testing and those with a high-throughput capability are highlighted.

This study presents a new method for generating tunable and uniform magnetic alginate microspheres, which can be widely employed in the field of the bead-based bio sample pretreatment and enrichment process during the clinical diagnoses. A microfluidic device comprising microchannels and controllable moving-wall structures was fabricated by using MEMS processes. The key feature of the controllable moving-wall structure is located nearby the flow-focusing microchannels and can be fine-tuned by the pneumatic pressure such that the sheath flows can be locally accelerated. With this approach, the size of the alginate microspheres can be fine-tuned without adjusting the syringe pumps. Therefore, the uniform magnetic alginate microspheres can be successfully generated.

In the study, we report a microfluidic-based dispenser fabricated by standard soft lithography of PDMS (polydimethylsiloxane) for sub-microliter range precise pipetting. The key feature of the microfluidic-based dispenser is the incorporation of a pressure-generating unit providing the driving force for precise and quick aqueous liquid sampling and pipetting. The microfluidic-based dispenser features in the elegant control of the releasing time of the air pressure in the pneumatic chamber of the pressure-generating unit causing the underside membrane to provide suction, thus contributing to precise pipetting of aqueous liquid volumes ranging from 0.05 ?l to 0.45 ?l (the minimum unit is 0.05 ?l) achieving the multi-volume dispensing capability. Therefore, the developed microfluidic-based dispenser can dispense multiple sub-microliter aqueous liquid volumes precisely and quickly and is promising for further micro-total-analysis-systems in the field of drug dosing or other biomedical applications.

This study reports a new microfluidic-based cell culture platform. Moreover, microheaters, a micro temperature sensor, micropumps were integrated into the system to achieve a self-contained device for standard perfusion mammalian cell culture. One of key features of the proposed platform is the design of ultra-thin cell culture chamber allowing real-time cellular and sub-cellular imaging. The entire cell culture process can be performed automatically without human intervention. The developed platform was used for study of drug delivery on oral cancer cells. Experimental data showed that it can successfully monitor the dividing process of cancer cells. Besides, the cell response to anti-cancer drugs was also investigated. The developed platform can be promising for cell-based study.

This paper reports a new membrane-based pneumatic micropump with new serpentine-shape (S-shape) pneumatic channels intended for achieving high-throughput pumping in a microfluidic system at a relatively low pumping rate and a board flow rate range. The key feature of this design is the ability to modulate the pumping rates by fine-tuning the fluidic resistance of injected compressed air in the designed pneumatic microchannels and the chambers of the micropump. In the study, several S-shape pneumatic micropumps with various layouts were designed and fabricated based on thick-film photoresist lithography and polydimethylsiloxane (PDMS) replication processes. To investigate designs with a suitable pumping performance, S-shape pneumatic micropumps with varied lengths (1000, 5000 and 10 000 νm), varied widths (20, 40 and 200 νm) of the pneumatic microchannel bridging two rectangular pneumatic chambers, and different numbers of pneumatic channel bends (two and four U-shape bends) were designed and evaluated experimentally by using high-speed CCD-coupled microscopic observation of the movement of PDMS membrane pulsation and pumping rate measurements. The results revealed that under the experimental conditions studied, the layout of the S-shape pneumatic micropump with three rectangular pneumatic chambers, 5000 νm long and 40 νm wide pneumatic microchannel and four U-shape bends in the pneumatic microchannel was found to be capable of providing a broader pumping rate range from 0 to 539 νl h-1 compared to the other designs. As a whole, the experimental results demonstrate the use of fluidic resistance of injected air in a pneumatic micropump with S-shape layout to control its pumping performance, which largely expands the flexibility of its pumping application in a microfluidic system. © 2008 IOP Publishing Ltd.

This study reports a new perfusion-based, micro three-dimensional (3-D) cell culture platform for drug testing using enabling microfluidic technologies. The features of this cell culture platform include maintaining homogenous and stable culture environments, efficient medium delivery and cells/agarose (scaffold) loading; allowing realization of more precise and high-throughput cell culture-based assays. In this work, the perfusion-based, micro 3-D cell culture platform was designed and was fabricated based on SU-8 lithography and PDMS (poly-dimethylsiloxane) replication processes. The performance of the integrated pneumatic micropumps and cells/agarose loading mechanism were experimentally evaluated. The results show that in all of the 15 pneumatic micropumps studied, the medium delivery mechanism was able to provide a uniform flow output at flow rates ranging from 3.6 μl/h to 439.0 μl/h, depending on the applied pulsation frequency of the micropumps. In addition, the cell/agarose (scaffold) loading mechanism was proven to be able to perform sample loading tasks precisely and accurately in all of the 15 microbioreactors investigated with adjustable loading volumes of 0.22 μl, 0.18 μl and 0.14 μl at applied air pressures of 10 psi, 12 psi and 15 psi, respectively, in the microvalves. Furthermore, anti-cancer drug testing was successfully demonstrated using the proposed culture platform and fluorescent microscopic observation. As a whole, because of miniaturization, not only does this perfusion 3-D cell culture platform provide a homogenous and steady cell culture environment, but it also reduces the need for human intervention. Moreover, due to the integrated pumping of the medium and the cell/agarose (scaffold) loading mechanisms, time efficient and economical research work can be achieved. These characteristics are found particularly useful for high-precision and high-throughput 3-D cell culture-based drug testing. © 2007 Elsevier B.V. All rights reserved.

This study reports a new perfusion-based, micro three-dimensional (3-D) cell culture platform for drug testing using enabling microfluidic technologies. In this work, a perfusion-based, micro 3-D cell culture platform is designed and is fabricated based on SU-8 lithography and polydimethylsiloxane (PDMS) replication processes. One of the key features of the system is that the incorporation of a multiple medium pumping mechanism, consisting of 15 membrane-based pneumatic micropumps with serpentine-shape (S-shape) layout, coupled with a pneumatic tank, into the micro 3-D cell culture platform to provide efficient and economical culture medium delivery. Moreover, a “smart cell/agarose (scaffold) loading mechanism” was proposed, allowing the cell/3-D scaffold loading process in one step and avoiding too much laborious works and manual error. The results show that in all of the 15 S-shape pneumatic micropumps studied, the medium delivery mechanism is able to provide a uniform flow output ranging from 5.5 to 131 μl/hr depending on the applied pulsation frequency of the micropumps. In addition, the cell/agarose (scaffold) loading mechanism was proved to be able to perform sample loading tasks precisely and accurately in all of the 15 microbioreactors integrated. Furthermore, anti-cancer drug testing was successfully demonstrated using the proposed culture platform and fluorescent microscopic observation. As a whole, because of miniaturization, not only does this perfusion 3-D cell culture platform provide a homogenous and steady cell culture environment, but it also reduces the need for human intervention. Moreover, due to the integrated pumping of the medium and the cell/agarose (scaffold) loading mechanisms, time efficient and economical research work can be achieved. These characteristics are found particularly useful for high-precision and high-throughput 3-D cell culture-based drug testing.Copyright © 2008 by ASME

Negative selection-based circulating tumor cell (CTC) isolation is believed valuable to harvest more native, and in particular all possible CTCs without biases relevant to the properties of surface antigens on the CTCs. Under such a cell isolation strategy, however, the CTC purity is normally compromised. To address this issue, this study reports the integration of optically-induced-dielectrophoretic (ODEP) force-based cell manipulation, and a laminar flow regime in a microfluidic platform for the isolation of untreated, and highly pure CTCs after conventional negative selection-based CTC isolation. In the design, six sections of moving light-bar screens were continuously and simultaneously exerted in two parallel laminar flows to concurrently separate the cancer cells from the leukocytes based on their size difference and electric properties. The separated cell populations were further partitioned, delivered, and collected through the two flows. With this approach, the cancer cells can be isolated in a continuous, effective, and efficient manner. In this study, the operating conditions of ODEP for the manipulation of prostate cancer (PC-3) and human oral cancer (OEC-M1) cells, and leukocytes with minor cell aggregation phenomenon were first characterized. Moreover, performances of the proposed method for the isolation of cancer cells were experimentally investigated. The results showed that the presented CTC isolation scheme was able to isolate PC-3 cells or OEC-M1 cells from a leukocyte background with high recovery rate (PC-3 cells: 76-83%, OEC-M1 cells: 61-68%), and high purity (PC-3 cells: 74-82%, OEC-M1 cells: 64-66%) (set flow rate: 0.1 μl min(-1) and sample volume: 1 μl). The latter is beyond what is currently possible in the conventional CTC isolations. Moreover, the viability of isolated cancer cells was evaluated to be as high as 94 ± 2%, and 95 ± 3% for the PC-3, and OEC-M1 cells, respectively. Furthermore, the isolated cancer cells were also shown to preserve their proliferative capability. As a whole, this study has presented an ODEP-based microfluidic platform that is capable of isolating CTCs in a continuous, label-free, cell-friendly, and particularly highly pure manner. All these traits are found particularly meaningful for exploiting the harvested CTCs for the subsequent cell-based, or biochemical assays.

Although microfluidic cell culture systems are versatile tools for cellular assays, their use has yet to set in motion an evolutionary shift away from conventional cell culture methods. This situation is mainly due to technical hurdles: the operational barriers to the end-users, the lack of compatible detection schemes capable of reading out the results of a microfluidic-based cellular assay, and the lack of fundamental data to bridge the gap between microfluidic and conventional cell culture models. To address these issues, we propose a high-throughput, perfusion, three-dimensional (3-D) microfluidic cell culture system encompassing 30 microbioreactors. This integrated system not only aims to provide a user-friendly cell culture tool for biologists to perform assays but also to enable them to obtain precise data. Its technical features include (i) integration of a heater chip based on transparent indium tin oxide glass, providing stable thermal conditions for cell culturing; (ii) a microscale 3-D culture sample loading scheme that is both efficient and precise; (iii) a non-mechanical pneumatically driven multiplex medium perfusion mechanism; and (iv) a microplate reader-compatible waste medium collector array for the subsequent high throughput bioassays. In this study, we found that the 3-D culture sample loading method provided uniform sample loading [coefficient of variation (CV): 3.2%]. In addition, the multiplex medium perfusion mechanism led to reasonably uniform (CV: 3.6-6.9%) medium pumping rates in the 30 microchannels. Moreover, we used the proposed system to perform a successful cell culture-based chemosensitivity assay. To determine the effects of cell culture models on the cellular proliferation, and the results of chemosensitivity assays, we compared our data with that obtained using three conventional cell culture models. We found that the nature of the cell culture format could lead to different evaluation outcomes. Consequently, when establishing a cell culture model for in vitro cell-based assays, it might be necessary to investigate the fundamental physiological variations of the cultured cells in different culture systems to avoid any misinterpretation of data. As a whole, we have developed an integrated microfluidic cell culture system that overcomes several technical hurdles commonly encountered in the practical application of microfluidic cell culture systems, and we have obtained fundamental information to reconcile differences found with data acquired using conventional methods.

In this study, we report a pneumatically driven micro-dispenser for precise pipetting of sub-micro-liter samples. The key feature of this micro-dispenser is the use of a suction membrane to provide a driving force for precise and quick aqueous liquid sampling and pipetting. The control of the release time of the suction membrane can generate precise pipetting of liquid volumes ranging from 0.05 µl to 0.45 µl (with 2.9% variation). Experimental results reveal that the micro-dispenser is able to perform liquid dispensing in a high reproducible manner and with a superior performance compared to commercial pipettors. This micro-dispenser is fabricated using standard soft lithography of PDMS (polydimethylsiloxane). Hence it can be easily integrated with other microfluidic devices for subsequent microfluidic applications. The developed pneumatically driven micro-dispenser is promising for further integration into micro-total-analysis systems in the field of drug dosing or for other biomedical analysis applications.