Isolation of cells from heterogeneous biological samples is critical in both basic biological research and clinical diagnostics. Affinity-based methods, such as those that recognise cells by binding antibodies to cell membrane biomarkers, can be used to achieve specific cell isolation. Microfluidic techniques have been employed to achieve more efficient and effective cell isolation. By employing aptamers as surface-immobilised ligands, cells can be easily released and collected after specific capture. However, these methods still have limitations in cell release efficiency and spatial selectivity. This study presents an aptamer-based microfluidic device that not only achieves specific affinity cell capture, but also enables spatially selective temperature-mediated release and retrieval of cells without detectable damage. The specific cell capture is realised by using surface-patterned aptamers in a microchamber on a temperature-control chip. Spatially selective cell release is achieved by utilising a group of microheater and temperature sensor that restricts temperature changes, and therefore the disruption of cell–aptamer interactions, to a design-specified region. Experimental results with CCRF-CEM cells and sgc8c aptamers have demonstrated the specific cell capture and temperature-mediated release of selected groups of cells with negligible disruption to their viability.

Ligand–receptor binding site model is used to elucidate the binding affinity between ligands and receptors, with transistor-based sensors. AlGaN/GaN high electron mobility transistors (HEMTs) were immobilised with antibodies and human immunodeficiency virus type 1 reverse transcriptase enzymes to detect peptides and human immunodeficiency virus drugs, respectively. The signals generated by the sensors because of the binding of the ligands to the receptors were fitted into the binding-site models and analysed. The dissociation constants of the ligand–receptor pairs and the number of the binding sites on the receptors were revealed. The results are very consistent with the data reported by the other methods from the literatures. The incorporation of the HEMTs and the binding-site models is demonstrated to be useful for studying the mechanism of the biomolecular interaction and the application for quick and cost-effective drug developments.

Receptor–ligand binding has been one of the more popular approaches to specifically targeting tumour cells. In this work, targeting efficiency was quantitatively characterized using silica particles functionalized with EpCAM antibodies and EpCAM-expressing BT-20 breast cancer cells. The effects of incubation time and particle concentration on the number of functionalised particles bound to target cells were experimentally investigated. The number of bound particles was found to increase with particle concentration, but not necessarily with incubation time. Binding affinity loss because of cell–particle–cell interaction was identified as a limiting mechanism for the number of particles bound to target cells. While cell-surface coverage because of bound particles rises exponentially under low particle concentration, it features a peak value at high particle concentration. The current findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity.

This study reports a correlation between cellular morphology and the ability of adapting to vesicular stomatitis virus infection. A time-lapse approach was employed to track the individual difference between homologous cells in adapting to viral infection. The authors single-cell analysis indicates that upon viral infection, mature cells that are in spindle shape are less likely to be infected after 24 h infection. On the other hand, cells undergoing proliferation, which are in rounder shape, tend to adopt a much higher viral infection within the same amount of time. This fact suggests that cellular morphology may be an early bioindicator for viral infection. The findings in this study could potentially be applied to other viral infection models.

This work mainly describes an electrochemical microsensor based on the reduction of molybdophosphate complex for total phosphorus (TP) determinations in water. The microelectrode was fabricated using microelectromechanical systems (MEMS) techniques and porous, branching gold nanoparticles (AuNPs) were electrodeposited on the microelectrode to improve its sensitivity. Calibration of the microsensor was performed with standard phosphate solutions prepared with KH₂PO₄ with pH adjusted to 1.0. The experimental results showed that both sensitivity and current response are improved effectively using this modified microelectrodes: The limit of detection of the microsensor is 1.2 × 10⁻⁷ mol/l and linear range is 3 × 10⁻⁷ to 3 × 10⁻⁴ mol/l. The sensitivity of unmodified electrode is −0.27 nA/μmol·l⁻¹ (R ² = 0.994), whereas the sensitivity of AuNPs modified electrode is −0.89 nA/μmol l⁻¹(R ² = 0.98). The current response of modified electrode is 6 times larger than that of unmodified electrode in average. Detection of TP was also carried out with digested TP standard solutions for both modified and unmodified electrodes, and results were consistent with the nominal value of phosphorus concentration. This microsensor provides the probability of combining TP detection device with micro-digesting device to form a TP detection system, which can realise the automotive and on-line monitoring of TP in surface water.

The authors developed a cantilever-arrayed blood pressure sensor array fabricated by (111) silicon bulk-micromachining for the non-invasive and continuous measurement of blood pressure. The blood pressure sensor measures the blood pressure based on the change in the resistance of the piezoresistor on a 5-μm-thick-arrayed perforated membrane and 20-μm-thick metal pads. The length and the width of the unit membrane are 210 and 310 μm, respectively. The width of the insensible zone between the adjacent units is only 10 μm. The resistance change over contact force was measured to verify the performance. The good linearity of the result confirmed that the polydimethylsiloxane package transfers the forces appropriately. The measured sensitivity was about 4.5%/N. The maximum measurement range and the resolution of the fabricated blood pressure sensor were greater than 900 mmHg ( = 120 kPa) and less than 1 mmHg ( = 133.3 Pa), respectively.

The development of carbon nanotube (CNT)-based sensors remains an active area of research. Towards this end, a new method for manipulating CNTs, assembling CNT networks and fabricating CNT-based nanosensors was demonstrated in this study. CNTs were collected and concentrated by optically-induced dielectrophoresis (ODEP) forces and aligned between a pair of electrodes. This assembly was then used directly as a temperature sensor and a hot-film anemometer, which detects changes in windspeed. By offering efficient CNT collection and ready-to-use sensor fabrication, this ODEP-based approach presents a promising method for the development of CNT-based sensing applications and massively parallel assembly of CNT-lines. The developed CNT-based nanosensors may be used to measure the temperature and the flow velocity of bio-samples in the near future.

Water sorption in sulphonated polyimides with or without ionic block structure was analysed with Feng's new dual mode model. The effect of their molecular structure that determines the chain organisation in the solid materials was analysed by using the model parameters. The model parameters C _p and A′ correspond to the sorbed water molecules on the first layer close to the ionic groups and on the subsequent layers, respectively. Based on these fitted physical parameters, the water sorption on the membranes with different counterions was studied and the hydration energy was proved to have much influence on the C _p values. The effect of the structure of the block and the random copolymers on the C _p and A′ values was discussed and compared with that for the well-known Nafion^® membranes. The large amount of sorbed water at high activities may induce a sufficiently large mobility of the polymer segments in the hydrophilic domains for material inflation, which leads to high A′ values.