Surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) are among the most common and powerful label-free refractive index-based biosensing techniques available nowadays. ...Focusing on LSPR sensors, their performance is highly dependent on the size, shape, and nature of the nanomaterial employed. Indeed, the tailoring of those parameters allows the development of LSPR sensors with a tunable wavelength range between the ultra-violet (UV) and near infra-red (NIR). Furthermore, dealing with LSPR along optical fiber technology, with their low attenuation coefficients at NIR, allow for the possibility to create ultra-sensitive and long-range sensing networks to be deployed in a variety of both biological and chemical sensors. This work provides a detailed review of the key science underpinning such systems as well as recent progress in the development of several LSPR-based biosensors in the NIR wavelengths, including an overview of the LSPR phenomena along recent developments in the field of nanomaterials and nanostructure development towards NIR sensing. The review ends with a consideration of key advances in terms of nanostructure characteristics for LSPR sensing and prospects for future research and advances in this field.
Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes. It is based on immobilization
via
interfacial activation of lipase B from
Candida antarctica
on a resin, ...Lewatit VP OC 1600. This resin is a macroporous support formed by poly(methyl methacrylate) crosslinked with divinylbenzene. N435 is perhaps the most widely used commercial biocatalyst in both academy and industry. Here, we review some of the success stories of N435 (in chemistry, energy and lipid manipulation), but we focus on some of the problems that the use of this biocatalyst may generate. Some of these problems are just based on the mechanism of immobilization (interfacial activation) that may facilitate enzyme desorption under certain conditions. Other problems are specific to the support: mechanical fragility, moderate hydrophilicity that permits the accumulation of hydrophilic compounds (
e.g.
, water or glycerin) and the most critical one, support dissolution in some organic media. Finally, some solutions (N435 coating with silicone, enzyme physical or chemical crosslinking, and use of alternative supports) are proposed. However, the N435 history, even with these problems, may continue in the coming future due to its very good properties if some simpler alternative biocatalysts are not developed.
Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.
This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives. This includes their use to activate supports and ...immobilize enzymes
via
ion exchange, as well as to improve immobilized enzymes by coating with PEI. PEI is a polymer containing primary, secondary and tertiary amino groups, having a strong anion exchange capacity under a broad range of conditions, and the capability to chemically react with different moieties on either an enzyme or a support. Also, as a multifunctional polymer, it has been modified stepwise to introduce different functionalities into the same polymer. This polymer (in combination with other anionic ones) permits the generation of "saline" environments around enzyme molecules, improving enzyme stability in the presence of hydrophobic compounds. The use of PEI as a physical glue useful to crosslink enzyme subunits in multimeric enzymes, monomeric enzymes immobilized
via
physical interactions or production of enzyme multilayers will be specially emphasized as new open avenues for enzyme coimmobilization. The coimmobilization of enzymes and cofactors using PEI may become one of the future developments allowed through an adequate use of this polymer and new pathways towards the design of enzyme combi-catalysts for their use in cascade reactions. Some unexplored but suggested uses derived from the properties of PEI are also proposed in the review, like the use of the buffering power of this multifunctional polymer to avoid pH gradients inside biocatalyst particles. Thus, although PEI has been a largely popular polymer in biocatalyst design, it looks like a long and in some cases almost unexplored road lies ahead.
This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives.
Biochemical-chemical sensing with plasmonic sensors is widely performed by tracking the responses of surface plasmonic resonance peaks to changes in the medium. Interestingly, consistent sensitivity ...and resolution improvements have been demonstrated for gold nanoparticles by analyzing other spectral features, such as spectral inflection points or peak curvatures. Nevertheless, such studies were only conducted on planar platforms and were restricted to gold nanoparticles. In this work, such methodologies are explored and expanded to plasmonic optical fibers. Thus, we study-experimentally and theoretically-the optical responses of optical fiber-doped gold or silver nanospheres and optical fibers coated with continuous gold or silver thin films. Both experimental and numerical results are analyzed with differentiation methods, using total variation regularization to effectively minimize noise amplification propagation. Consistent resolution improvements of up to 2.2× for both types of plasmonic fibers are found, demonstrating that deploying such analysis with any plasmonic optical fiber sensors can lead to sensing resolution improvements.
Enzymatic biocatalysis is a sustainable technology. Enzymes are versatile and highly efficient biocatalysts, and have been widely employed due to their biodegradable nature. However, because the ...three-dimensional structure of these enzymes is predominantly maintained by weaker non-covalent interactions, external conditions, such as temperature and pH variations, as well as the presence of chemical compounds, can modify or even neutralize their biological activity. The enablement of this category of processes is the result of the several advances in the areas of molecular biology and biotechnology achieved over the past two decades. In this scenario, metal–organic frameworks (MOFs) are highlighted as efficient supports for enzyme immobilization. They can be used to ‘house’ a specific enzyme, providing it with protection from environmental influences. This review discusses MOFs as structures; emphasizes their synthesis strategies, properties, and applications; explores the existing methods of using immobilization processes of various enzymes; and lists their possible chemical modifications and combinations with other compounds to formulate the ideal supports for a given application.
Immobilization and purification of enzymes are usual requirements for their industrial use. Both purification and immobilization have a common factor: they use a solid activated support. Using a ...support for enzyme purification means having mild conditions for enzyme release and a selective enzyme–support interaction is interesting. When using a support for immobilization, however, enzyme desorption is a problem. The improvement of enzyme features through immobilization is a usual objective (e.g., stability, selectivity). Thus, a support designed for enzyme purification and a support designed for enzyme immobilization may differ significantly. In this review, we will focus our attention on the requirements of a support surface to produce the desired objectives. The ideal physical properties of the matrix, the properties of the introduced reactive groups, the best surface activation degree to reach the desired objective, and the properties of the reactive groups will be discussed.
The key to enzymes: The support surface and its activation (number and kind of groups) is a key point in the design of a matrix for enzyme purification (determining the selectivity of enzyme adsorption) and immobilization (controlling the stabilization, enzyme orientation and activity). This paper reviews the most relevant features of a support to determine their feasibility in both techniques.
The pyrolysis process consists of the thermal decomposition of biomass in an inert atmosphere, which produces a liquid (bio-oil) composed of a complex mixture of organic compounds, including an oil ...and water phase. The aqueous fraction can reach up to 45% w/w, and understanding its composition is of utmost importance in determining its intended destination, whether for the reuse of compounds in industrial applications or for treating the effluent for disposal. In this study, a fast, direct, and efficient method using ultra-high-performance supercritical fluid chromatography (UHPSFC) was developed and optimized for monitoring phenols in aqueous samples obtained from the pyrolysis processing of six different biomass sources. The following parameters were evaluated for method optimization: stationary phase type, mobile phase flow, organic modifier, sample diluent, temperature, pressure, and modifier gradient time. With a total analysis time of 26 min, out of the fourteen (14) investigated phenolic compounds, eleven (11) were successfully separated after method optimization, and among them, five (5) were quantified in all six aqueous fractions. The aqueous fractions of residue from cowpea pod (1.89 mg.mL
−1
), sugar apple (3.09 mg.mL
−1
), and acerola (4.79 mg.mL
−1
) presented lower concentrations compared to grape (8.16 mg.mL
−1
), pine nuts (6.68 mg.mL
−1
), and guava (6.05 mg.mL
−1
) fractions. However, even at lower concentrations, all biomasses showed promising results regarding the phenolic compound content, analytes that have high added value for the chemical industry.
Graphical abstract
In this communication, lipase A from
(CALA) was immobilized by covalent bonding on magnetic nanoparticles coated with chitosan and activated with glutaraldehyde, labelled CALA-MNP, (immobilization ...parameters: 84.1% ± 1.0 for immobilization yield and 208.0 ± 3.0 U/g ± 1.1 for derivative activity). CALA-MNP biocatalyst was characterized by X-ray Powder Diffraction (XRPD), Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetry (TG) and Scanning Electron Microscope (SEM), proving the incorporation of magnetite and the immobilization of CALA in the chitosan matrix. Besides, the immobilized biocatalyst showed a half-life 8-11 times higher than that of the soluble enzyme at pH 5-9. CALA showed the highest activity at pH 7, while CALA-MNP presented the highest activity at pH 10. The immobilized enzyme was more active than the free enzyme at all studied pH values, except pH 7.
Enzymes serve as biocatalysts for innumerable important reactions, however, their application has limitations, which can in many cases be overcome by using appropriate immobilization strategies. ...Here, a new support for immobilizing enzymes is proposed. This hybrid organic-inorganic support is composed of chitosan-a natural, nontoxic, biodegradable, and edible biopolymer-and sodium polyphosphate as the inorganic component. Lipase B from
(CALB) was immobilized on microspheres by encapsulation using these polymers. The characterization of the composites (by infrared spectroscopy, thermogravimetric analysis, and confocal Raman microscopy) confirmed the hybrid nature of the support, whose external part consisted of polyphosphate and core was composed of chitosan. The immobilized enzyme had the following advantages: possibility of enzyme reuse, easy biocatalyst recovery, increased resistance to variations in temperature (activity declined from 60 °C and the enzyme was inactivated at 80 °C), and increased catalytic activity in the transesterification reactions. The encapsulated enzymes were utilized as biocatalysts for transesterification reactions to produce the compound responsible for the aroma of jasmine.
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