High-performance immunosensor for urine albumin using hybrid architectures of ZnO nanowire/carbon nanotube.

In this work, the authors reported the hybrid architecture of carbon nanotube (CNT)-zinc oxide (ZnO) nanowire as a multi-functional probe in amperometric immunosensor for the detection of urine albumin. Low-cost substrate such as glass is possible because of novel low-temperature growth process of CNT/ZnO nanowires as a multi-function electrode in this sensor. Based on Schottky like behaviour this structure exhibit excellent high current density to achieve higher performance. Measurement of urine albumin is a new way for early detection of diabetic and also low concentration of it in culture media is also considered in order to verify the conversion of stem cells to liver cells. Human albumin serum antibody is used as a selective and sensitive part. The amperometric performance of immunosensor is studied and showed excellent performance for detection of albumin in urine samples. Very high linear range (from 3.3 ng/µl to 3.3 mg/µl) with a correlation coefficient of 0.825 and low detection limit (3.3 ng/µl or 4.96 × 10-8 mol l-1) are the main characteristics of this sensor. Due to the high dynamic range and sensitivity, this sensor was also used in medical diagnosis and biomedical applications.

A conductive cell-imprinted substrate based on CNT-PDMS composite.

Cell function regulation is influenced by continuous biochemical and biophysical signal exchange within the body. Substrates with nano/micro-scaled topographies that mimic the physiological niche are widely applied for tissue engineering applications. As the cartilage niche is composed of several stimulating factors, a multifunctional substrate providing topographical features while having the capability of electrical stimulation is presented. Herein, we demonstrate a biocompatible and conductive chondrocyte cell-imprinted substrate using polydimethylsiloxane (PDMS) and carbon nanotubes (CNTs) as conductive fillers. Unlike the conventional silicon wafers or structural photoresist masters used for molding, cell surface topographical replication is challenging as biological cells showed extremely sensitive to chemical solvent residues during molding. The composite showed no significant difference compared with PDMS with regard to cytotoxicity, whereas an enhanced cell adhesion was observed on the conductive composite's surface. Integration of nanomaterials into the cell seeding scaffolds can make tissue regeneration process more efficient.

Cell-Imprint Surface Modification by Contact Photolithography-Based Approaches: Direct-Cell Photolithography and Optical Soft Lithography Using PDMS Cell Imprints.

New cell-imprint surface modification techniques based on direct-cell photolithography and optical soft lithography using poly(dimethylsiloxane) (PDMS) cell imprints are presented for enhanced cell-based studies. The core concept of engineering materials for cell-based studies is the material's ability to redesign the physicochemical characteristics of the cellular niche. There is a growing interest in direct molding from cells (cell imprinting). These negative copies of cell surface topographies have been shown to affect cell shape and direct mesenchymal stem cells' differentiation. Analyzing the results is however challenging as cells seeded on these substrates do not always end up in a cell pattern, which leads to decreased effectiveness and biased quantification. To gain control over cell seeding into the patterns and avoid unwanted cell population outside of the patterns, the cell-imprinted surface needs to be modified. From this perspective, the standard optical contact lithography process was modified and cells were introduced to the cleanroom. Direct-cell photolithography was used for a single-step PDMS cell-imprint (chondrocytes as the molding template) surface modification down to single-cell (approximately 5 µm in diameter) resolution. As cells come in a variety of shapes, sizes, and optical profiles, a complementary optical soft lithography-based photomask fabrication technique is also reported. The simplicity of the fabrication process makes this cell-imprint surface modification technique compatible with any adherent cell type and leads to efficient cell-based studies.

Fabrication of sensitive glutamate biosensor based on vertically aligned CNT nanoelectrode array and investigating the effect of CNTs density on the electrode performance.

In this report, the fabrication of vertically aligned carbon nanotube nanoelectrode array (VACNT-NEA) by photolithography method is presented. Electrochemical impedance spectroscopy as well as cyclic voltammetry was performed to characterize the arrays with respect to different diffusion regimes. The fabricated array illustrated sigmoidal cyclic voltammogram with steady state current dominated by radial diffusion. The fabricated VACNT-NEA and high density VACNTs were employed as electrochemical glutamate biosensors. Glutamate dehydrogenase is covalently attached to the tip of CNTs. The voltammetric biosensor, based on high density VACNTs, exhibits a sensitivity of 0.976 mA mM(-1) cm(-2) in the range of 0.1-20 µM and 0.182 mA mM(-1) cm(-2) in the range of 20-300 µM glutamate with a low detection limit of 57 nM. Using the fabricated VACNT-NEA, the sensitivity increases approximately to a value of 2.2 Am M(-1) cm(-2) in the range of 0.01 to 20 µM and to 0.1 A mM(-1) cm(-2) in the range of 20-300 µM glutamate. Using this electrode, a record of low detection limit of 10 nM was achieved for glutamate. The results prove the efficacy of the fabricated NEA for low cost and highly sensitive enzymatic biosensor with high sensitivity well suited for voltammetric detection of a wide range of clinically important biomarkers.