Au nanoparticles-3D graphene hydrogel nanocomposite to boost synergistically in situ detection sensitivity toward cell-released nitric oxide

In situ detection of nitric oxide (NO) released from living cells has become very important in studies of some critical physiological and pathological processes, but it is still very challenging due to the low concentration and fast decay of NO. A nanocomposite of Au nanoparticles deposited on three-dimensional graphene hydrogel (Au NPs-3DGH) was prepared through a facile one-step approach by in situ reduction of Au(3+) on 3DGH to build a unique sensing film for a strong synergistic effect, in which the highly porous 3DGH offers a large surface area while Au NPs uniformly deposited on 3DGH efficiently catalyze the electrochemical oxidation of NO for sensitive detection of NO with excellent selectivity, fast response, and low detection limit. The sensor was further used to in situ detect NO released from living cells under drug stimulation, showing significant difference between normal and tumor cells under drug stimulation.

Immobilization of Myoglobin from Horse Skeletal Muscle in Hydrophilic Polymer Networks

This work examines the immobilization of myoglobin from horse skeletal muscle in hydrophilic polymer networks. Due to specific changes in the spectroscopic properties of hemoproteins during ligand binding, they could be employed in optical sensing devices. Two immobilization techniques were considered: imbibition and entrapment. Anionic hydrogels composed of methacrylic acid (MAA), cationic hydrogels composed of dimethylamino ethyl methacrylate (DMAEM), and neutral hydrogels composed of poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMA; molecular weight = 200, 400, or 1000), all crosslinked with poly(ethylene glycol) dimethacrylate (PEGDMA) (molecular weight = 200, 600, or 1000), were synthesized by free-radical solution polymerization. By the imbibition method, MAA-based hydrogels incorporated the highest amount of myoglobin in comparison with PEGMA or DMAEM polymers. The evaluation of the correlation length of the networks revealed that MAA hydrogels had the highest correlation length in comparison with PEGMA-containing matrices or DMAEM hydrogels. Release experiments from MAA hydrogels at pHs 5.8 and 7.0 showed that the solute-transport mechanism was a combination of Fickian and chain relaxation diffusion. Myoglobin-loaded MAA hydrogels retained their heme reactivity after the immobilization process. The release of myoglobin incorporated by entrapment in MAA-PEGDMA hydrogels was highly influenced by the chain relaxation process. The diffusion coefficients of myoglobin incorporated by entrapment into anionic hydrogels were 2 orders of magnitude smaller (~10-13) than those for myoglobin incorporated by imbibition (10-11), both evaluated at pH 7.0. Substrate binding studies indicated that the protein biological activity was not compromised in those hydrogels loaded by the imbibition method, whereas prepolymeric solutions showed detrimental effects on protein stability.

Third-generation biosensors based on the direct electron transfer of proteins

Recent progress in third-generation electrochemical biosensors based on the direct electron transfer of proteins is reviewed. The development of three generations of electrochemical biosensors is also simply addressed. Special attention is paid to protein-film voltammetry, which is a powerful way to obtain the direct electron transfer of proteins. Research activities on various kinds of biosensors are discussed according to the proteins (enzymes) used in the specific work.

The immobilization of hepatocytes on 24 nm-sized gold colloid for enhanced hepatocytes proliferation

Bioartificial liver and hepatocyte transplantation is anticipated to supply a temporary metabolic support for candidates of liver transplantation or for patients with fulminant liver failure. An essential restriction of this form is the inability to acquire an enough amount of hepatocytes. Enhancement of the proliferation and differentiated function of hepatocytes is becoming a pursued target. Here, porcine hepatocytes were successfully immobilized on nano-sized gold colloid particles to construct a "hepatocyte/gold colloid" interface at which hepatocytes can be quickly proliferated. The properties of this resulting interface were characterized and confirmed by scanning electron microscopy and atomic force microscopy. The proliferative mechanism of hepatocytes was also discussed. The proliferated hepatocytes could be applied to the clinic based on their excellent functions for the synthesis of protein, glucose and urea as well as lower lactate dehydrogenase release.

An Electrochemical Biosensor for Nitric Oxide Based on Silver Nanoparticles and Hemoglobin

A nitric oxide (NO) biosensor based on silver nanoparticles was fabricated with high sensitivity and selectivity as well as stability. Silver nanoparticles could preserve the microstructures of hemoglobin, but the electrochemical reactivity of the protein and its detection sensitivity toward NO could be greatly enhanced. Accordingly, a NO biosensor was developed. The linear concentration range was from 1.0 x 10(-6) to 5.0 x 10(-5) M. Its detection limit was 3.0 x 10(-7) M with a sensitivity of 0.0424 microA microM(-1) NO. The possible co-existing compounds would not interfere with the detection.