Fabrication of Cell Chip for Detection of Cell Cycle Progression Based on Electrochemical Method

Sensors-integrated organ-on-a-chip for biomedical applications

As a promising new micro-physiological system, organ-on-a-chip has been widely utilized for in vitro pharmaceutical study and tissues engineering based on the three-dimensional constructions of tissues/organs and delicate replication of in vivo-like microenvironment. To better observe the biological processes, a variety of sensors have been integrated to realize in-situ, real-time, and sensitive monitoring of critical signals for organs development and disease modeling. Herein, we discuss the recent research advances made with respect to sensors-integrated organ-on-a-chip in this overall review. Firstly, we briefly explore the underlying fabrication procedures of sensors within microfluidic platforms and several classifications of sensory principles. Then, emphasis is put on the highlighted applications of different types of organ-on-a-chip incorporated with various sensors. Last but not least, perspective on the remaining challenges and future development of sensors-integrated organ-on-a-chip are presented.

Copper nanowire array as highly selective electrochemical sensor of nitrate ions in water

Contamination of water with nitrate ions is a significant problem that affects many areas of the world. For this reason, European legislation has set the maximum permissible concentration of nitrates in drinking water at 44 mg/L. Thus, it is clear that a continuous monitoring of nitrate ions is of high technological interest but it must be rapid, easy to perform and directly performable in situ. In this work we have developed a nanostructured sensor based on array of copper nanowires obtained with the simple method of galvanic deposition. The nanostructured sensors have a very short response time with a detection limit less than 10 μM. Different interfering species were tested finding a negligible effect except for the chloride ions. However, this problem has been solved by removing chloride ions from the water through a simple precipitation of chloride compounds with low solubility. Nanostructured sensors were also used to analyze real water samples (rain, river and drinking water). In the case of drinking water, we have measured a concentration of nitrate ions very close to the that measured by conventional laboratory techniques.

Adhesion, proliferation and differentiation of human mesenchymal stem cell on chitosan/collagen composite scaffold

In vitro tissue engineering requires a progenitor cell source and a porous scaffold providing three dimensional (3D) supports for growth and differentiation to attain tissue architectures. This research focused on fabrication and characterization of 3D porous scaffolds using chitosan (CS), collagen (CG) and chitosan-collagen (CS-CG) composite to investigate their influence on human mesenchymal stem cell (hMSC) adhesion, proliferation and differentiation. Material dependent variations in porous morphology and mechanical behavior of the fabricated CS, CG and CS-CG scaffold showed significant impact on hMSC adhesion, proliferation and differentiation. The maximum hMSC adhesion and proliferation was reported on CS-CG scaffold among all fabricated scaffold groups. Interconnectivity of pores structure in CS-CG scaffold was considered as preferable attribute for such enhanced growth and distribution throughout the scaffold. Besides, CS scaffold with well interconnected pores showed poor adhesion and proliferation because of inadequate adhesion motifs. In case of CG scaffold, optimum growth and distribution of hMSC occurs only at the surface because of the absence of interconnectivity in their pore structures. Likewise, osteogenic differentiation of hMSC occurs most preferably in CS-CG composite scaffold among all scaffold groups. Such enhanced hMSC proliferation and differentiation in CS-CG scaffold significantly influenced on mechanical behavior of scaffold which is essential for in vivo application of a bone tissue implant. Thus CS-CG composite scaffold holds promise to be a suitable platform for in vitro engineering of bone tissue implant.

Engineered chitosan for improved 3D tissue growth through Paxillin-FAK-ERK activation

Scaffold engineering has attracted significant attention for three-dimensional (3D) growth, proliferation and differentiation of stem cells in vitro. Currently available scaffolds suffer from issues such as poor ability for cell adhesion, migration and proliferation. This paper addresses these issues with 3D porous chitosan scaffold, fabricated and functionalized with cysteine-terminated Arg-Gly-Asp (Cys-RGD) tri-peptide on their walls. The study reveals that the compressive moduli of the scaffold is independent to RGD functionalization but shows dependence on the applied freezing temperature (TM) during the fabrication process. The low freezing TM (-80°C) produces scaffold with high compressive moduli (14.64 ± 1.38 kPa) and high TM (-30°C) produces scaffold with low compressive moduli (5.6 ± 0.38 kPa). The Cys-RGD functionalized scaffolds lead to significant improvements in adhesion (150%) and proliferation (300%) of human mesenchymal stem cell (hMSC). The RGD-integrin coupling activates the focal adhesion signaling (Paxillin-FAK-ERK) pathways, as confirmed by the expression of p-Paxillin, p-FAK and p-ERK protein, and results in the observed improvement of cell adhesion and proliferation. The proliferation of hMSC on RGD functionalized surface was evaluated with scanning electron microscopy imaging and distribution though pore was confirmed by histochemistry of transversely sectioned scaffold. The hMSC adhesion and proliferation in scaffold with high compressive moduli showed a constant enhancement (with a slope value 9.97) of compressive strength throughout the experimental period of 28 days. The improved cell adhesion and proliferation with RGD functionalized chitosan scaffold, together with their mechanical stability, will enable new interesting avenues for 3D cell growth and differentiation in numerous applications including regenerative tissue implants.

Association of Gpx1 fluctuation in cell cycle progression

This research demonstrates fluctuation of glutathione peroxidase1 (Gpx1) throughout cell cycle progression with significant decreased expression at mitosis of HeLa cell. This was achieved with western blot (WB) analysis of target proteins from each phase of synchronized cells. The synchronizations were performed with double thymidine (T/T) for G1/S arrest and thymidine followed by nocodazole (T/N) for G2/M arrest. The G1/S arrested cells were released in fresh medium for 3, 6, 9, 10, and 15h to obtain cell at each phase such as gap1 (G1), synthesis (S), gap2 (G2), mitosis (M), and gap1 (G1) phase, respectively, for investigating Gpx1 expression throughout a complete cycle. The synchronizations were confirmed using fluorescence activated cell sorting (FACS) and WB analysis of phase-specific markers. The fluctuations of Gpx1 expression were verified with universal protein actin and peroxiredoxin1 (Prx1) which are stable throughout the cell cycle. Intriguingly, immunoblots showed the level of Gpx1 decreases at mitosis phase and increased during mitotic exit to G1 phase in HeLa cells, while Prx1 protein level remained constant. The fractionation experiments reveal that only the cytosolic Gpx1 was decreased while their levels at mitochondria remain constant. The highest levels of mitochondrial ROS were measured in mitosis phase with FACS analysis using Mito sox indicating that antioxidant activity of Gpx1 for detoxifying excessive induced endogenous reactive oxygen species (ROS) in the mitosis phase could be the reason for such decreasing level. For unfolding the molecular mechanism of such decreased expression, the Gpx1 was investigated at transcriptional, translational, and proteosomal level. The results revealed that translational mechanism is involve in the decreased expression rather than transcriptional or proteosomal degradation at mitosis phase. This finding supports that Gpx1 is involved in the cell cycle progression through regulation of endogenous ROS. Based on this observation, further research could uncover their possible association with the infinitive division of a cancer cell.

Advances in sensing and biosensing of bisphenols: A review

Bisphenols (BPs) are well known endocrine disrupting chemicals (EDCs) that cause adverse effects on the environment, biotic life and human health. BPs have been studied extensively because of an increasing concern for the safety of the environment and for human health. They are major raw materials for manufacturing polycarbonates, thermal papers and epoxy resins and are considered hazardous environmental contaminants. A vast array of sensors and biosensors have been developed for the sensitive screening of BPs based on carbon nanomaterials (carbon nanotubes, fullerenes, graphene and graphene oxide), quantum dots, metal and metal oxide nanocomposites, polymer nanocomposites, metal organic frameworks, ionic liquids and molecularly imprinted polymers. This review is devoted mainly to a variety of sensitive, selective and reliable sensing and biosensing methods for the detection of BPs using electrochemistry, fluorescence, colorimetry, surface plasmon resonance, luminescence, ELISAs, circular dichroism, resonance Rayleigh scattering and adsorption techniques in plastic products, food samples, food packaging, industrial wastes, pharmaceutical products, human body fluids and many other matrices. It summarizes the advances in sensing and biosensing methods for the detection of BPs since 2010. Furthermore, the article discusses challenges and future perspectives in the development of novel sensing methods for the detection of BP analogs.

Engineered peptide-based nanobiomaterials for electrochemical cell chip

Biomaterials having cell adhesion ability are considered to be integral part of a cell chip. A number of researches have been carried out to search for a suitable material for effective immobilization of cell on substrate. Engineered ECM materials or their components like collagen, Poly-l-Lysine (PLL), Arg-Gly-Asp (RGD) peptide have been extensively used for mammalian cell adhesion and proliferation with the aim of tissue regeneration or cell based sensing application. This review focuses on the various approaches for two- and three-dimensionally patterned nanostructures of a short peptide i.e. RGD peptide on chip surfaces together with their effects on cell behaviors and electrochemical measurements. Most of the study concluded with positive remarks on the well-oriented engineered RGD peptide over their homogenous thin film. The engineered RGD peptide not only influences cell adhesion, spreading and proliferation but also their periodic nano-arrays directly influence electrochemical measurements of the chips. The electrochemical signals found to be enhanced when RGD peptides were used in well-defined two-dimensional nano-arrays. The topographic alteration of three-dimensional structure of engineered RGD peptide was reported to be suitably contacted with the integrin receptors of cellular membrane which results indicated the enhanced cell-electrode adhesion and efficient electron exchange phenomenon. This enhanced electrochemical signal increases the sensitivity of the chip against the target analytes. Therefore, development of engineered cellular recognizable peptides and its 3D topological design for fabrication of cell chip will provide the synergetic effect on bio-affinity, sensitivity and accuracy for the in situ real-time monitoring of analytes.

Neural Cell Chip Based Electrochemical Detection of Nanotoxicity

Development of a rapid, sensitive and cost-effective method for toxicity assessment of commonly used nanoparticles is urgently needed for the sustainable development of nanotechnology. A neural cell with high sensitivity and conductivity has become a potential candidate for a cell chip to investigate toxicity of environmental influences. A neural cell immobilized on a conductive surface has become a potential tool for the assessment of nanotoxicity based on electrochemical methods. The effective electrochemical monitoring largely depends on the adequate attachment of a neural cell on the chip surfaces. Recently, establishment of integrin receptor specific ligand molecules arginine-glycine-aspartic acid (RGD) or its several modifications RGD-Multi Armed Peptide terminated with cysteine (RGD-MAP-C), C(RGD)₄ ensure farm attachment of neural cell on the electrode surfaces either in their two dimensional (dot) or three dimensional (rod or pillar) like nano-scale arrangement. A three dimensional RGD modified electrode surface has been proven to be more suitable for cell adhesion, proliferation, differentiation as well as electrochemical measurement. This review discusses fabrication as well as electrochemical measurements of neural cell chip with particular emphasis on their use for nanotoxicity assessments sequentially since inception to date. Successful monitoring of quantum dot (QD), graphene oxide (GO) and cosmetic compound toxicity using the newly developed neural cell chip were discussed here as a case study. This review recommended that a neural cell chip established on a nanostructured ligand modified conductive surface can be a potential tool for the toxicity assessments of newly developed nanomaterials prior to their use on biology or biomedical technologies.

3D graphene oxide-encapsulated gold nanoparticles to detect neural stem cell differentiation

Monitoring of stem cell differentiation and pluripotency is an important step for the practical use of stem cells in the field of regenerative medicine. Hence, a new non-destructive detection tool capable of in situ monitoring of stem cell differentiation is highly needed. In this study, we report a 3D graphene oxide-encapsulated gold nanoparticle that is very effective for the detection of the differentiation potential of neural stem cells (NSCs) based on surface-enhanced Raman spectroscopy (SERS). A new material, 3D GO-encapsulated gold nanoparticle, is developed to induce the double enhancement effect of graphene oxide and gold nanoparticle on SERS signals which is only effective for undifferentiated NSCs. The Raman peaks achieved from undifferentiated NSCs on the graphene oxide (GO)-encapsulated gold nanoparticles were 3.5 times higher than peaks obtained from normal metal structures and were clearly distinguishable from those of differentiated cells. The number of CC bonds and the Raman intensity at 1656 cm(-1) was found to show a positive correlation, which matches the differentiation state of the NSCs. Moreover, the substrate composed of 3D GO-encapsulated gold nanoparticles was also effective at distinguishing the differentiation state of single NSC by using electrochemical and electrical techniques. Hence, the proposed technique can be used as a powerful non-destructive in situ monitoring tool for the identification of the differentiation potential of various kinds of stem cells (mesenchymal, hematopoietic, and neural stem cells).