Biosensor for total cholesterol estimation using N-(2-aminoethyl)-3-aminopropyltrimethoxysilane self-assembled monolayer

Single CsPbBr3 Perovskite Microcrystals: From Microcubes to Microrods with Improved Crystallinity and Green Emission

All-inorganic perovskite materials are promising in optoelectronics, but their morphology is a key parameter for achieving high device efficiency. We prepared CsPbBr3 perovskite microcrystals with different shapes grown directly on planar substrate by conventional drop casting. We observed the formation of CsPbBr3 microcubes on bare indium tin oxide (ITO)-coated glass. Interestingly, with the same technique, CsPbBr3 microrods were obtained on (3-Aminopropyl) triethoxysilane (APTES)-modified ITO-glass, which we ascribe to the modification of formation kinetics. The obtained microcrystals exhibit an orthorhombic structure. A green photoluminescence (PL) emission is revealed from the CsPbBr3 microrods. Contact angle measurements, Fourier-transform infrared and PL spectroscopies confirmed that APTES linked successfully to the ITO-glass substrate. We propose a qualitative mechanism to explain the anisotropic growth. The microrods exhibited improved PL and a slower PL lifetime compared to the microcubes, likely due to the diminished occurrence of defects. This work demonstrates the importance of the substrate surface to control the growth of perovskite single crystals and to boost the radiative recombination in view of high-performance optoelectronic devices.

Recent Advances in Nano-Bio-Sensing Fabrication Technology for the Detection of Oral Cancer

Nanotechnology-based miniaturized devices have been a breakthrough in the pre-clinical and clinical research areas, e.g. drug delivery, personalized medicine. They have revolutionized the discovery and development of biomarker-based diagnostic devices for detection of various diseases such as tuberculosis, malaria and cancer. Nanomaterials (NMs) hold tremendous diagnostic potential due to their high surface-to-volume ratio and quantum confinement phenomenon, improving the detection limit of clinically relevant biomolecules in bio-fluids. Thus, they are helpful in the translation of bench-on platform to point-of-care (POC) screening device. The nanomaterial-based biosensor fabrication technology has also simplified and improved oral cancer (OC) or oral squamous cell carcinomas (OSCC) diagnosis. The fabrication of nano-bio sensors involves application specific modifications of NMs. The unique properties functionalized NMs have augmented their application on the nano-biosensing platform for the detection of clinically relevant biomolecules in bio-fluids. Therefore, this article summarizes the recent advancements in the process of fabrication of nano-biosensors for detection of OC.

A novel chemiluminescence sensor for sensitive detection of cholesterol based on the peroxidase-like activity of copper nanoclusters

A sensitive and selective chemiluminescence (CL) sensor based on the peroxidase-like activity of copper nanoclusters was established for the detection of cholesterol. Copper nanoclusters catalyse the CL reaction between luminol and H₂O₂. Because H₂O₂ is the oxidative product of cholesterol in the presence of cholesterol oxidase, the oxidation of cholesterol can be quantitatively converted to a CL response by combining the two reactions. The proposed method is simple and can be completed in a few minutes with high sensitivity. Under the optimal conditions, the CL intensity was proportional to the concentration of cholesterol over a wide range of 0.05-10 mM, with a detection limit of 1.5 μM. Furthermore, the method was successfully applied to determine cholesterol in milk powder and human serum with satisfactory accuracy and precision. This method expands the applications of nano-mimic enzymes in the field of CL-based sensors.

Identification and statistical optimization of fermentation conditions for a newly isolated extracellular cholesterol oxidase-producing Streptomyces cavourensis strain NEAE-42

BACKGROUND

Due to broad range of clinical and industrial applications of cholesterol oxidase, isolation and screening of bacterial strains producing extracellular form of cholesterol oxidase is of great importance.

RESULTS

One hundred and thirty actinomycete isolates were screened for their cholesterol oxidase activity. Among them, a potential culture, strain NEAE-42 is displayed the highest extracellular cholesterol oxidase activity. It was selected and identified as Streptomyces cavourensis strain NEAE-42. The optimization of different process parameters for cholesterol oxidase production by Streptomyces cavourensis strain NEAE-42 using Plackett-Burman experimental design and response surface methodology was carried out. Fifteen variables were screened using Plackett-Burman experimental design. Cholesterol, initial pH and (NH4)2SO4 were the most significant positive independent variables affecting cholesterol oxidase production. Central composite design was chosen to elucidate the optimal concentrations of the selected process variables on cholesterol oxidase production. It was found that, cholesterol oxidase production by Streptomyces cavourensis strain NEAE-42 after optimization process was 20.521U/mL which is higher than result obtained from the basal medium before screening process using Plackett-Burman (3.31 U/mL) with a fold of increase 6.19.

CONCLUSIONS

The cholesterol oxidase level production obtained in this study (20.521U/mL) by the statistical method is higher than many of the reported values.

Application of APTES-Anti-E-cadherin film for early cancer monitoring

Cancer staging is a way to classify cancer according to the extent of the disease in the body. The stage is usually determined by several factors such as the location of the primary tumor, the tumor size, the degree of spread in the surrounding tissues, etc. The study of E-cadherin (EC) expression on cancerous cells of patients has revealed variations in the molecular expression patterns of primary tumors and metastatic tumors. The detection of these cells requires a long procedure involving conventional techniques, thus, the requirement for development of new rapid devices that permit direct and highly sensitive detection stimulates the sensing field progress. Here, we explore if E-cadherin could be used as a biomarker to bind and detect epithelial cancer cells. Hence, the sensitive and specific detection of E-cadherin expressed on epithelial cells is approached by immobilizing anti-E-cadherin antibody (AEC) onto aminosilanized indium-tin oxide (ITO) surface. The immunosensing surfaces have been characterized by electrochemical measurements, wettability and confocal microscopy and their performance has been assessed in the presence of cancer cell lines. Under optimal conditions, the resulting immunosensor displayed a selective detection of E-cadherin expressing cells, which could be detected either by fluorescence or electrochemical techniques. The developed immunosensing surface could provide a simple tool that can be applied to cancer staging.

Engineered proteins for bioelectrochemistry

It is only in the past two decades that excellent protein engineering tools have begun to meet parallel advances in materials chemistry, nanofabrication, and electronics. This is revealing scenarios from which synthetic enzymes can emerge, which were previously impossible, as well as interfaces with novel electrode materials. That means the control of the protein structure, electron transport pathway, and electrode surface can usher us into a new era of bioelectrochemistry. This article reviews the principle of electron transfer (ET) and considers how its application at the electrode, within the protein, and at a redox group is directing key advances in the understanding of protein structure to create systems that exhibit better efficiency and unique bioelectrochemistry.

Vapor-liquid-solid grown silica nanowire based electrochemical glucose biosensor

Vapor-liquid-solid (VLS) grown silica nanowires (SiO(2)NWs) have been deposited electrophoretically on a gold electrode and utilized for covalent immobilization of glucose oxidase (GOx). Covalent binding has been achieved via 3-aminopropyltriethoxysilane (APTES) modification and N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide chemistry. Scanning electron microscopy, transmission electron microscopy and cyclic voltammetry techniques have been used to characterize SiO(2)NW and GOx/APTES/SiO(2)NW/Au bioelectrode. Electrochemical studies reveal that SiO(2)NW increases the effective electro-active surface area thus resulting in higher loading of enzyme. Response characteristics show linearity in the range of interest 25-300 mg dl(-1), with a detection limit of 11 mg dl(-1), sensitivity: 0.463 µA (mg dl(-1))(-1) and regression coefficient of 0.992.

Cholesterol oxidase: structure and function

Cholesterol oxidase is a bacterial-specific flavoenzyme that catalyzes the oxidation and isomerisation of steroids containing a 3beta hydroxyl group and a double bond at the Delta5-6 of the steroid ring system. The enzyme is a member of a large family of flavin-specific oxidoreductases and is found in two different forms: one where the flavin adenine dinucleotide (FAD) cofactor is covalently linked to the protein and one where the cofactor is non-covalently bound to the protein. These two enzyme forms have been extensively studied in order to gain insight into the mechanism of flavin-mediated oxidation and the relationship between protein structure and enzyme redox potential. More recently the enzyme has been found to play an important role in bacterial pathogenesis and hence further studies are focused on its potential use for future development of novel antibacterial therapeutic agents. In this review the biochemical, structural, kinetic and mechanistic features of the enzyme are discussed.

Characteristics and biotechnological applications of microbial cholesterol oxidases

Microbial cholesterol oxidase is an enzyme of great commercial value, widely employed by laboratories routinely devoted to the determination of cholesterol concentrations in serum, other clinical samples, and food. In addition, the enzyme has potential applications as a biocatalyst which can be used as an insecticide and for the bioconversion of a number of sterols and non-steroidal alcohols. The enzyme has several biological roles, which are implicated in the cholesterol metabolism, the bacterial pathogenesis, and the biosynthesis of macrolide antifungal antibiotics. Cholesterol oxidase has been reported from a variety of microorganisms, mostly from actinomycetes. We recently reported cholesterol oxidases from gram-negative bacteria such as Burkholderia and Chromobacterium. These enzymes possess thermal, detergent, and organic solvent tolerance. There are two forms of cholesterol oxidase, one containing a flavin adenine dinucleotide cofactor non-covalently bound to the enzyme (class I) and the other containing the cofactor covalently linked to the enzyme (class II). These two enzymes have no significant sequence homology. The phylogenetic tree analyses show that both class I and class II enzymes can be further divided into at least two groups.

Purification and characterization of Chromobacterium sp. DS-1 cholesterol oxidase with thermal, organic solvent, and detergent tolerance

A new screening method for 6beta-hydroperoxycholest-4-en-3-one (HCEO)-forming cholesterol oxidase was devised in this study. As the result of the screening, a novel cholesterol oxidase producer (strain DS-1) was isolated and identified as Chromobacterium sp. Extracellular cholesterol oxidase of strain DS-1 was purified from the culture supernatant. The molecular mass of the purified enzyme was 58 kDa. This enzyme showed a visible adsorption spectrum having peaks at 355 and 450 nm, like a typical flavoprotein. The enzyme oxidized cholesterol to HCEO, with the consumption of 2 mol of O2 and the formation of 1 mol of H2O2 for every 1 mol of cholesterol oxidized. The enzyme oxidized 3beta-hydroxysteroids such as cholesterol, beta-cholestanol, and pregnenolone at high rates. The Km value for cholesterol was 26 microM. The enzyme was stable at pH 3 to 11 and most active at pH 7.0-7.5, showing optimal activity at pH 7.0 and 65 degrees C. The enzyme retained about 80% of its activity after incubation for 30 min at 85 degrees C. The thermal stability of the enzyme was the highest among the cholesterol oxidases tested. Moreover, the enzyme was more stable in the presence of various organic solvents and detergents than commercially available cholesterol oxidases.