An iridium oxide microelectrode for monitoring acute local pH changes of endothelial cells.

pH sensors were fabricated by anodically electrodepositing iridium oxide films (AEIROFs) onto microelectrodes on chips and coated with poly(ethyleneimine) (PEI) for mechanical stability. These demonstrate super-Nernstian response to pH from pH 4.0 to 7.7 in chloride-free phosphate buffer. The surface of the chip was coated with fibronectin for the attachment of porcine aortic endothelial cells (PAECs). The working capability of the pH sensor for monitoring acute local pH changes was investigated by stimulating the PAECs with thrombin. Our results show that thrombin induced acute extracellular acidification of PAECs and dissolution of fibronectin, causing the local pH to decrease. The use of PD98059, a mitogen-activated protein kinase (MAPK) inhibitor, reduced extracellular acidification and an increase in local pH was observed. This study shows that our pH sensors can facilitate the investigation of acute cellular responses to stimulation by monitoring the real-time, local pH changes of cells attached to the sensors.

Advances of lab-on-a-chip in isolation, detection and post-processing of circulating tumour cells.

Circulating tumour cells (CTCs) are shed by primary tumours and are found in the peripheral blood of patients with metastatic cancers. Recent studies have shown that the number of CTCs corresponds with disease severity and prognosis. Therefore, detection and further functional analysis of CTCs are important for biomedical science, early diagnosis of cancer metastasis and tracking treatment efficacy in cancer patients, especially in point-of-care applications. Over the last few years, there has been an increasing shift towards not only capturing and detecting these rare cells, but also ensuring their viability for post-processing, such as cell culture and genetic analysis. High throughput lab-on-a-chip (LOC) has been fuelled up to process and analyse heterogeneous real patient samples while gaining profound insights for cancer biology. In this review, we highlight how miniaturisation strategies together with nanotechnologies have been used to advance LOC for capturing, separating, enriching and detecting different CTCs efficiently, while meeting the challenges of cell viability, high throughput multiplex or single-cell detection and post-processing. We begin this survey with an introduction to CTC biology, followed by description of the use of various materials, microstructures and nanostructures for design of LOC to achieve miniaturisation, as well as how various CTC capture or separation strategies can enhance cell capture and enrichment efficiencies, purity and viability. The significant progress of various nanotechnologies-based detection techniques to achieve high sensitivities and low detection limits for viable CTCs and/or to enable CTC post-processing are presented and the fundamental insights are also discussed. Finally, the challenges and perspectives of the technologies are enumerated.

RGD-peptide functionalized graphene biomimetic live-cell sensor for real-time detection of nitric oxide molecules.

It is always challenging to construct a smart functional nanostructure with specific physicochemical properties to real time detect biointeresting molecules released from live-cells. We report here a new approach to build a free-standing biomimetic sensor by covalently bonding RGD-peptide on the surface of pyrenebutyric acid functionalized graphene film. The resulted graphene biofilm sensor comprises a well-packed layered nanostructure, in which the RGD-peptide component provides desired biomimetic properties for superior human cell attachment and growth on the film surface to allow real-time detection of nitric oxide, an important signal yet short-life molecule released from the attached human endothelial cells under drug stimulations. The film sensor exhibits good flexibility and stability by retaining its original response after 45 bending/relaxing cycles and high reproducibility from its almost unchanged current responses after 15 repeated measurements, while possessing high sensitivity, good selectivity against interferences often existing in biological systems, and demonstrating real time quantitative detection capability toward nitric oxide molecule released from living cells. This study not only demonstrates a facial approach to fabricate a smart nanostructured graphene-based functional biofilm, but also provides a powerful and reliable platform to the real-time study of biointeresting molecules released from living cells, thus rendering potential broad applications in neuroscience, screening drug therapy effect, and live-cell assays.

In situ molecular detection of ischemic cells by enhanced protein direct electron transfer on a unique horseradish peroxidase-Au nanoparticles-polyaniline nanowires biofilm.

To overcome shortcomings of the ex situ approaches, in situ detection using H(2)O(2) molecules to diagnose ischemia through enhanced protein direct electron transfer on a unique horseradish peroxidase-Au nanoparticles-polyaniline nanowires biofilm is demonstrated and it is discovered that the extracellular H(2)O(2) molecule released per ischemic cell is 2.7-times of that of a normal cell.