Strategies for Stabilization of Enzymes in Organic Solvents

Trends in protein-based biosensor assemblies for drug screening and pharmaceutical kinetic studies

The selection of natural and chemical compounds for potential applications in new pharmaceutical formulations constitutes a time-consuming procedure in drug screening. To overcome this issue, new devices called biosensors, have already demonstrated their versatility and capacity for routine clinical diagnosis. Designed to perform analytical analysis for the detection of a particular analyte, biosensors based on the coupling of proteins to amperometric and optical devices have shown the appropriate selectivity, sensibility and accuracy. During the last years, the exponential demand for pharmacokinetic studies in the early phases of drug development, along with the need of lower molecular weight detection, have led to new biosensor structure materials with innovative immobilization strategies. The result has been the development of smaller, more reproducible biosensors with lower detection limits, and with a drastic reduction in the required sample volumes. Therefore in order to describe the main achievements in biosensor fields, the present review has the main aim of summarizing the essential strategies used to generate these specific devices, that can provide, under physiological conditions, a credible molecule profile and assess specific pharmacokinetic parameters.

Application of iron magnetic nanoparticles in protein immobilization

Due to their properties such as superparamagnetism, high surface area, large surface-to-volume ratio, easy separation under external magnetic fields, iron magnetic nanoparticles have attracted much attention in the past few decades. Various modification methods have been developed to produce biocompatible magnetic nanoparticles for protein immobilization. This review provides an updated and integrated focus on the fabrication and characterization of suitable magnetic iron nanoparticle-based nano-active materials for protein immobilization.

Reusable and mediator-free cholesterol biosensor based on cholesterol oxidase immobilized onto TGA-SAM modified smart bio-chips

A reusable and mediator-free cholesterol biosensor based on cholesterol oxidase (ChOx) was fabricated based on self-assembled monolayer (SAM) of thioglycolic acid (TGA) (covalent enzyme immobilization by dropping method) using bio-chips. Cholesterol was detected with modified bio-chip (Gold/Thioglycolic-acid/Cholesterol-oxidase i.e., Au/TGA/ChOx) by reliable cyclic voltammetric (CV) technique at room conditions. The Au/TGA/ChOx modified bio-chip sensor demonstrates good linearity (1.0 nM to 1.0 mM; R = 0.9935), low-detection limit (∼0.42 nM, SNR∼3), and higher sensitivity (∼74.3 µAµM⁻¹cm⁻²), lowest-small sample volume (50.0 μL), good stability, and reproducibility. To the best of our knowledge, this is the first statement with a very high sensitivity, low-detection limit, and low-sample volumes are required for cholesterol biosensor using Au/TGA/ChOx-chips assembly. The result of this facile approach was investigated for the biomedical applications for real samples at room conditions with significant assembly (Au/TGA/ChOx) towards the development of selected cholesterol biosensors, which can offer analytical access to a large group of enzymes for wide range of biomedical applications in health-care fields.

Modification of PEGylated enzyme with glutaraldehyde can enhance stability while avoiding intermolecular crosslinking

We demonstrate an enzyme stabilization approach whereby a model enzyme is PEGylated, followed by controlled chemical modification with glutaraldehyde. Using this stabilization strategy, size increases and aggregation due to intermolecular crosslinking are avoided. Immediately following synthesis, the PEGylated enzyme with and without glutaraldehyde modification possessed specific activities of 372.9 ± 20.68 U/mg and 373.9 ± 15.14 U/mg, respectively (vs. 317.7 ± 19.31 U/mg for the native enzyme). The glutaraldehyde-modified PEGylated enzyme retains 73% original activity after 4 weeks at 37 °C (vs. 2% retention for control).

Optimized production of vanillin from green vanilla pods by enzyme-assisted extraction combined with pre-freezing and thawing

Production of vanillin from natural green vanilla pods was carried out by enzyme-assisted extraction combined with pre-freezing and thawing. In the first step the green vanilla pods were pre-frozen and then thawed to destroy cellular compartmentation. In the second step pectinase from Aspergillus niger was used to hydrolyze the pectin between the glucovanillin substrate and β-glucosidase. Four main variables, including enzyme amount, reaction temperature, time and pH, which were of significance for the vanillin content were studied and a central composite design (CCD) based on the results of a single-factor tests was used. Response surface methodology based on CCD was employed to optimize the combination of enzyme amount, reaction temperature, time, and pH for maximum vanillin production. This resulted in the optimal condition in regards of the enzyme amount, reaction temperature, time, and pH at 84.2 mg, 49.5 °C, 7.1 h, and 4.2, respectively. Under the optimal condition, the experimental yield of vanillin was 4.63% ± 0.11% (dwb), which was in good agreement with the value predicted by the model. Compared to the traditional curing process (1.98%) and viscozyme extract (2.36%), the optimized method for the vanillin production significantly increased the yield by 133.85% and 96%, respectively.

Pectin cross-linked enzyme aggregates (pectin-CLEAs) of glucoamylase

CLEAs of glucoamylase were prepared using pectin as non-toxic and macromolecular cross-linker which showed improved thermal stability and good reusability.

Enzyme immobilization in biosensor constructions: self-assembled monolayers of calixarenes containing thiols

Herein, an amperometric glucose oxidase (GOx) biosensor is presented using calixarenes as an immobilization matrix of the biomolecule.

Lipase catalyzed synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione)

Synthesis of 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) (3) catalyzed by lipase.

Penicillium expansum lipase-coated magnetic Fe3O4–polymer hybrid hollow nanoparticles: a highly recoverable and magnetically separable catalyst for the synthesis of 1,3-dibutylurea

Amino-epoxy supports were innovatively imported onto magnetic nanoparticles for immobilizing enzyme which represents a novel class of heterogeneous catalyst for the synthesis of 1,3-dibutylurea from ethylene carbonate and butylamine.

Immobilization of urease on magnetic nanoparticles coated by polysiloxane layers bearing thiol- or thiol- and alkyl-functions

An optimized strategy for production of a highly active magnetic formulation of urease has been elaborated via systematic studies of the enzyme immobilization on magnetite nanoparticles coated by functional siloxane layers.

Computational tools for designing and engineering enzymes

Protein engineering strategies aimed at constructing enzymes with novel or improved activities, specificities, and stabilities greatly benefit from in silico methods. Computational methods can be principally grouped into three main categories: bioinformatics; molecular modelling; and de novo design. Particularly de novo protein design is experiencing rapid development, resulting in more robust and reliable predictions. A recent trend in the field is to combine several computational approaches in an interactive manner and to complement them with structural analysis and directed evolution. A detailed investigation of designed catalysts provides valuable information on the structural basis of molecular recognition, biochemical catalysis, and natural protein evolution.