Specific Immobilization Research Articles

Engineering Phi29-DNAP Variants for Customized DNA Hydrogel Materials.

DNA hydrogels, which hold potential for use in medicine, biosensors, and tissue engineering, can be produced through enzymatic rolling circle amplification (RCA) using phi29 DNA polymerase (DNAP). This paper introduces new DNAP variants designed for RCA-based DNA hydrogel production, featuring enzymes with modified DNA binding, enhanced thermostability, reduced exonuclease activity, and protein tags for fluorescence detection or specific immobilization. We evaluated these enzymes by quantifying DNA output via quantitative PCR (qPCR) and assessing hydrogel mechanical properties through micromechanical indentation. The results showed that most variants generated similar DNA amounts and hydrogels with comparable mechanical properties. Additionally, all variants successfully incorporated non-natural nucleotides, such as base-modified dGTP derivatives and 2'fluoro-dGTP, during RCA. This study's robust analytical approach offers a strong foundation for selecting new enzymes and producing DNA hydrogels with tailored material properties.

Rice rhizospheric effects and mechanism on soil cadmium bioavailability during silicon application

Exogenous Si mitigates the mobility and bioavailability of Cd in the soil, thereby alleviating its phytotoxicity. This study focused on specific Si-induced immobilisation effects within the rhizosphere (S1), near-rhizosphere (S2), and far-rhizosphere (S3) zones. Based on the rhizobox experiment, we found that applying Si significantly elevated soil pH, and the variation amplitudes in the S3 soil exceeded those in the S1 and S2 soils. Si-induced changes in the rhizosphere also included enhanced dissolved organic carbon and diminished soil Eh, particularly in the Si400 treatment. Meanwhile, the introduction of Si greatly enhanced the Fe2+ and Mn2+ concentrations in the S1 soil, but reduced them in the S2 soil. The rhizosphere effect of Si which enriched Fe2+ and Mn2+ subsequently promoted the formation of Fe and Mn oxides/hydro-oxides near the rice roots. Consequently, the addition of Si significantly reduced the available Cd concentrations in S1, surpassing the reductions in S2 and S3. Moreover, Si-treated rice exhibited increased Fe plaque generation and fixation on soil Cd, resulting in decreased Cd concentrations in rice tissues, accompanied by reduced Cd translocation from roots to shoots and shoots to grains. Structural equation modelling further highlighted that Si is essential in Cd availability in S1 and Fe plaque development, ultimately mitigating Cd accumulation in rice. Si-treated rice also exhibited higher biomass and grain yield than those of control groups. These findings provide valuable insights into Si-based strategies for addressing the Cd contamination of agricultural soils.

One-Step Purification and Immobilization of Glycosyltransferase with Zn-Ni MOF for the Synthesis of Rare Ginsenoside Rh2.

Uridine diphosphate (UDP)-glucosyltransferases (UGTs) have received increasing attention in the field of ginsenoside Rh2 conversion. By harnessing the metal chelation between transition metal ions and imidazole groups present on His-tagged enzymes, a specific immobilization of the enzyme within metal-organic frameworks (MOFs) is achieved. This innovative approach not only enhances the stability and reusability of the enzyme but also enables one-step purification and immobilization. Consequently, the need for purifying crude enzyme solutions is effectively circumvented, resulting in significant cost savings during experimentation. The use of immobilized enzymes in catalytic reactions has shown great potential for achieving higher conversion rates of ginsenoside Rh2. In this study, highly stable mesoporous Zn-Ni MOF materials were synthesized at 150 °C by a solvothermal method. The UGT immobilized on the Zn-Ni MOF (referred to as UGT@Zn-Ni MOF) exhibited superior pH adaptability and thermal stability, retaining approximately 76% of its initial activity even after undergoing 7 cycles. Furthermore, the relative activity of the immobilized enzyme remained at an impressive 80.22% even after 45 days of storage. The strong specific adsorption property of Zn-Ni MOF on His-tagged UGT was confirmed through analysis using polyacrylamide gel electrophoresis. UGT@Zn-Ni MOF was used to catalyze the conversion reaction, and the concentration of rare ginsenoside Rh2 was generated at 3.15 μg/mL. The results showed that Zn-Ni MOF is a material that can efficiently purify and immobilize His-tagged enzyme in one step and has great potential for industrial applications in enzyme purification and ginsenoside synthesis.

Microfluidic paper-based analysis device applying black phosphorus nanosheets@MWCNTs-COOH: A portable and efficient strategy for detection of β-Lactoglobulin in dairy products

This study prepared a novel, portable and cost-effective microfluidic paper-based electrochemical analysis device (μ-PAD) using black phosphorus nanosheets@carboxylated multi-walled carbon nanotubes (BPNSs@MWCNTs-COOH) nanocomposites for β-lactoglobulin (β-LG) detection. At the appreciate ratio, the synthesized BPNSs@MWCNTs-COOH was demonstrated to not only serve as a high-quality substrate for the specific aptamer immobilization, but also improve the electron transfer capability of the sensing interface. The μ-PADs, utilizing BPNSs@MWCNTs-COOH and aptamer recognition, exhibited a wider detection range (10–1000 ng mL−1) and lower detection limit (LOD: 0.12 ng mL−1) for β-LG, and demonstrated enhanced specificity, satisfactory anti-interference ability and stability. When applied to the β-LG determination in dairy samples, the μ-PAD yielded β-LG concentrations highly correlated with those obtained using the HPLC method (R2: 0.9982). These results emphasized the reliable performance of the developed μ-PADs in β-LG allergen quantification, highlighting their potential as an efficient platform for the rapid screening of β-LG allergens.

A paradigm shift for biocatalytic microreactors: Decoupling application from reactor design

Microreactors have been successfully applied to execute a broad range of biotransformations in flow. However, microreactors have typically been designed with a specific biotransformation or a specific biocatalyst immobilization method in mind, constraining their wider applicability. Furthermore, their design is typically either applicable for whole-cell or for enzyme biocatalysis, but not for both. We present a novel microreactor design which offers cartridge-like insertion of both immobilised enzymes and cells. A T-shaped lid opens and closes the reaction chamber (whilst leaving the rest of the microreactor unchanged), enables the easy insertion of immobilised biocatalysts, and thus allows the user to configure different reactor types. We demonstrated this novel concept showing three different reactor types: a hydrogel microreactor containing entrapped E. coli cells overexpressing transketolase (volumetric productivity of 2.23 ± 0.83 mmoll-ERY Lvoid1 min1), a packed-bed microreactor containing commercial beads with immobilised Candida antarctica lipase B (volumetric productivity of 317.69 ± 96.74 mmolBB Lvoid1 min1), and a micropillar microreactor containing surface-immobilised ω-transaminase (volumetric productivity of 0.08 ± 0.02 mmolACP Lvoid1 min1). The proposed design showed consistency and robustness for 10 consecutive T-shaped lid ‘open and close’ cycles and withstood the pressure of at least 4 bar. Design analysis further included Computational Fluid Dynamics models and Residence Time Distribution measurements. The presented design offers a standardised approach for multiple applications, underpinning process development and paving the way for off-the-shelf microreactor technology for biocatalysis.

Microorganism Immobilization Device Using Artificial Siderophores

Inspired by the mechanism by which microorganisms utilize siderophores to ingest iron, four different FeIII complexes of typical artificial siderophore ligands containing catecholate and/or hydroxamate groups, K3[FeIII-LC3], K2[FeIII-LC2H1], K[FeIII-LC1H2], and [FeIII-LH3], were prepared. They were modified on an Au substrate surface (Fe-L/Au) and applied as microorganism immobilization devices for fast, sensitive, selective detection of microorganisms, where H6LC3, H5LC2H1, H4LC1H2, and H3LH3 denote the tri-catecholate, biscatecholate-monohydroxamate, monocatecholate-bishydroxamate, and tri-hydroxamate type of artificial siderophores, respectively. Their adsorption properties for the several microorganisms were investigated using scanning electron microscopy (SEM), quartz crystal microbalance (QCM), and electric impedance spectroscopy (EIS) methods. The artificial siderophore-iron complexes modified on the Au substrates Fe-LC3/Au, Fe-LC2H1/Au, Fe-LC1H2/Au, and Fe-LH3/Au showed specific microorganism immobilization behavior with selectivity based on the structure of the artificial siderophores. Their specificities corresponded well with the structural characteristics of natural siderophores that microorganisms release from the cell and/or use to take up an iron. These findings suggest that release and uptake are achieved through specific interactions between the artificial siderophore-FeIII complexes and receptors on the cell surfaces of microorganisms. This study revealed that Fe-L/Au systems have specific potential to serve as effective immobilization probes of microorganisms for rapid, selective detection and identification of a variety of microorganisms.

Advanced applications in enzyme-induced electrospun nanofibers.

Electrospun nanofibers, renowned for their high specific surface area, robust mechanical properties, and versatile chemical functionalities, offer a promising platform for enzyme immobilization. Over the past decade, significant strides have been made in developing enzyme-induced electrospun nanofibers (EIEN). This review systematically summarizes the advanced applications of EIEN which are fabricated using both non-specific immobilization methods including interfacial adsorption (direct adsorption, cross-linking, and covalent binding) and encapsulation, and specific immobilization techniques (coordination and affinity immobilization). Future research should prioritize optimizing immobilization techniques to achieve a balance between enzyme activity, stability, and cost-effectiveness, thereby facilitating the industrialization of EIEN. We elucidate the rationale behind various immobilization methods and their applications, such as wastewater treatment, biosensors, and biomedicine. We aim to provide guidelines for developing suitable EIEN immobilization techniques tailored to specific future applications.

Polymer Brushes: Novel Surfaces for Biomedical Applications

Polymer brushes played an important role in surface modification techniques to improve the biocompatibility of modified surfaces inside the human body for different biological and biomedical applications. This modification give the ability to control biointerfacial interactions such as cell attachment, protein adsorption and bacterial biofilm formation. Surface modification with polymer layers can be utilized to alter the surface properties, including biocompatibility, antifouling ability, corrosion resistance and wettability, and it can be achieved by immobilisation or spraying of polymers from solution. Also, it is easy to graft polymers with reactive end groups onto surfaces leading to the formation of polymer brushes at high density, which have specific features, such as chemical robustness, tunable mechanical properties and the flexibility to use polymers of different chemistry or introduction of bifunctional polymers for specific immobilisation of other molecules, especially proteins and enzymes. The specific properties of polymer brushes make them ideal candidates to be used in the biomedical field. For example,

Synthesis and characterization of sodium-aluminophosphate based glass-ceramics containing NZP phase for HLW immobilization

Stable sodium-aluminophosphate (SAP) based glass-ceramics with sodium zirconium phosphate (NZP) crystalline phase for high-level nuclear waste (HLW) immobilization were prepared by a melt-quenching process, and the effects of ZrO2 and B2O3 on their phase composition, structural features and properties were discussed in detail. The results show that the SAP based glass-ceramics obtained by the melt-quenching process show good aqueous durability and thermal stability. ZrO2 addition improves the formation of NZP phase but restrains the crystallization of AlPO4 phases. It is found that the correct ratios of ZrO2 and B2O3 allow only phase formation of NZP within the SAP glass, and the reasons were also analyzed. The conclusions demonstrate that the SAP based glass-ceramics with NZP phase as the crystalline phase are the potential matrices for specific HLW immobilization, and suggest that the melt-quenching process is an applicable way to prepare certain glass-ceramic waste forms.

Tailored hydrogel entrapped catalyst with highly active, controlled catalytic activity for the removal of 4-nitrophenol (4-NP)

In catalytic reactions, achieving large specific surface area immobilisation of the catalyst is an important factor affecting the catalytic effect, however, the primary challenges in utilizing hydrogels as catalyst carriers are to enhance the mechanical properties of the hydrogel to improve the activity and controllability of the catalyst. In this study, a new structure of P(AM-co-AA)/SMA/NH2-SiO2 hydrogels was synthesized via free radical polymerization, and the effects of the content of AA and NH2-SiO2 on the mechanical properties of the hydrogels were investigated. Without the use of additional cross-linking agents, both a chemical cross-linking network and a hydrophobic linkage network were established, which effectively reconstructed the structure of the hydrogels and dissipated energy. As a result, P(AM-co-AA-1.5 %)/SMA/NH2-SiO2-0.5 % hydrogel exhibited high mechanical properties, with tensile strength, elongation, and toughness reaching 1456 KPa, 4605 %, and 23.59 MJ/m3, respectively. This hydrogel can be utilized as a template for in situ and stable Ag NPs. Additionally, P(AM-co-AA)/SMA/NH2-SiO2@Ag composite hydrogels were prepared using cation exchange and in situ reduction methods for the catalytic reduction of 4-nitrophenol (4-NP). The composite hydrogel exhibited fast catalysis, high efficiency, stable cycling, recyclability and adjustable catalytic activity at 35 °C with Kapp = 0.811 min−1. Furthermore, using this composite hydrogel alleviated the need for separating metal nanoparticle catalysts from the reaction system, thereby enabling the development of robust hydrogel materials with controlled catalytic activity for the wastewater treatment industry.

The clinical relevance of margins in frameless stereotactic radiosurgery for intact brain metastases: A randomized trial of 0 vs 2 mm margins.

TPS2080 Background: Stereotactic radiosurgery (SRS) is a commonly utilized treatment strategy for brain metastases which offers a relatively low rate of morbidity and high rate of local control. SRS delivers an ablative dose of radiation in a single session to a limited target volume while minimizing dose to surrounding normal tissue. Image-guided linear accelerator (LINAC)-based frameless SRS has enabled effective, safe delivery of high dose radiation without the discomfort and logistical complications associated with use of a rigid frame. Localization errors during frameless SRS vary depending on the specific LINAC configuration and immobilization technique. The clinical relevance of potential inaccuracies in localization with frameless SRS remains controversial. When employing frameless systems, many centers will account for set-up uncertainties by adding a circumferential margin of 1-3 mm around the GTV to create a planning target volume (PTV). This PTV expansion ensures adequate tumor coverage if target motion occurs, but exposes more normal brain tissue to radiation and may increase the risk of adverse events, chiefly radionecrosis. There is limited literature available to guide radiation oncologists on the appropriate choice of margin size, if any, for frameless SRS. There are no randomized data evaluating the safety and efficacy of omitting the margin entirely. Given the paucity of data examining margin extent and the potentially significant consequences for treatment efficacy and morbidity, we propose a phase II randomized prospective clinical trial evaluating 0 vs 2 mm marginal GTV to PTV expansions for treating patients with intact brain metastases with frameless SRS. Methods: Eligible patients will have brain metastases from solid tumors with ECOG performance status of 0-2 and life expectancy of >3 months. Patients must have 1 - 5 newly diagnosed well-circumscribed, measurable intraparenchymal brain metastases with maximum tumor diameter ≤3.0 cm. At least one lesion must be ≥ 0.5 cm in maximum diameter to be considered measurable. SRS will be delivered in a single fraction to either 20 Gy or 18 Gy dependent on tumor size. Importantly, PTV margin randomization is blinded and occurs after delineation of tumor volume by radiation oncologist to not bias contouring based on knowledge of margin randomization. This is two-armed multi-center phase II randomized controlled trial. The trial is powered to demonstrate non- inferiority of the experimental arm with regard to the primary endpoint of local PFS at 6 months and the superiority of the experimental arm with regard to the secondary endpoint of radionecrosis or pseudoprogression. We expect the total study duration, from the start of screening for the first participant until the end of follow-up for the last one, to be approximately six years. We plan to accrue 166 patients to this trial at all sites. Clinical trial information: NCT02747303 .

NTA-Cholesterol Analogue for the Nongenetic Liquid-Ordered Phase-Specific Functionalization of Lipid Membranes with Proteins.

The nongenetic modification of cell membranes with proteins is a straightforward way of cellular engineering. In these processes, it is important to specifically address the proteins to liquid-ordered (Lo) or liquid-disordered (Ld) domains as this can largely affect their biological functions. Herein, we report a cholesterol analogue (CHIM) with a nitrilotriacetic acid (NTA) headgroup, named CHIM-NTA. CHIM-NTA integrates into lipid membranes similar to the widely used phospholipid-derived DGS-NTA and, when loaded with Ni2+, allows for specific membrane immobilization of any polyhistidine-tagged proteins of choice. Yet, unlike DGS-NTA, it localizes to the Lo phase in phase-separated giant unilamellar vesicles (GUVs) and allows addressing His-tagged proteins to Lo domains. Furthermore, CHIM-NTA readily integrates into the membranes of live cells and thus enables the nongenetic modification of the cell surface with proteins. Overall, CHIM-NTA provides a facile and flexible way to modify biological membranes, in particular Lo domains, with His-tagged proteins and can serve as a broadly applicable molecular tool for cell surface engineering.

Magnetically purification/immobilization of poly histidine-tagged proteins by PEGylated magnetic graphene oxide nanocomposites

Carbon-based nanomaterials have many applications in biomedicine due to their unique mechanical, chemical, and biological properties. Among them, graphene has received special attention due to its very high specific surface area, high flexibility, and chemical stability. In this study, graphene oxide was first functionalized with amine groups (GO-NH2) and then Fe3O4 nanoparticles were deposited on it using the hydrothermal method. In addition, polyethylene glycol (PEG) was attached to the magnetic graphene nanoparticles to increase their stability and solubility. Finally, PEGylated magnetic graphene nanocomposites were functionalized with nickel-nitrilotriacetic acid (NTA-Ni+2) to bind to the poly-histidine tag in recombinant proteins. The resulting nanocomposites (MG-PEG-NTA-Ni+2) were then used for magnetic immobilization and purification of recombinant β-NGF as a protein with his-tag sequence. Binding and purification were confirmed by FTIR and SDS-PAGE techniques, respectively. Importantly, differentiation of the PC12 cell line into neurons demonstrated that the purified β-NGF was fully functional. Our results suggest that MG-PEG-NTA-Ni+2 nanocomposites may be a suitable alternative to commercial resins for rapid and specific protein immobilization and purification.

Ultrasensitive Electrochemiluminescence Biosensor with Silver Nanoclusters as a Novel Signal Probe and α-Fe2O3-Pt as an Efficient Co-reaction Accelerator for Procalcitonin Immunoassay.

Herein, a high-efficiency biosensor based on ternary electrochemiluminescence (ECL) system was constructed for procalcitonin (PCT) detection. Specifically, silver nanoclusters (Ag NCs) with stable luminescence properties were prepared with small-molecule lipoic acid (LA) as the ligand, and its ECL emission in persulfate (S2O82-) was first reported. Meanwhile, the prepared Ag NCs possessed ligand-to-metal charge-transfer characteristics, thus transferring energy from LA to Ag+ for luminescence. Based on the small particle size, good biocompatibility, and molecular binding ability, Ag NCs-LA was used as an ideal luminescent probe. In addition, α-Fe2O3-Pt was introduced to facilitate the activation of S2O82-, thereby generating more sulfate radicals to react with the free radicals of Ag NCs to enhance ECL emission. The synergistic effect of the variable valence state of transition metals and high catalytic activity of noble metals endows α-Fe2O3-Pt with excellent catalytic ability for S2O82-. Importantly, the sensing mechanism was systematically demonstrated by UV-vis, fluorescence, and ECL analysis, as well as density functional theory calculations. At last, NKFRGKYKC was designed for specific immobilization of antibodies, thus releasing the antigen binding sites to improve the antigen recognition efficiency. Based on this, the developed biosensor showed high sensitivity for PCT detection, with a wide linear range (10 fg/mL-100 ng/mL) and a low detection limit (3.56 fg/mL), which could be extended to clinical detection of multiple biomarkers.

Dipole moment as the underlying mechanism for enhancing the immobilization of glucose oxidase by ferrocene-chitosan for superior specificity non-invasive glucose sensing.

Non-invasive methods for sensing glucose levels are highly desirable due to the comfortableness, simplicity, and lack of infection risk. However, the insufficient accuracy and ease of interference limit their practical medical applications. Here, we develop a non-invasive salivary glucose biosensor based on a ferrocene-chitosan (Fc-Chit) modified carbon nanotube (CNT) electrode through a simple drop-casting method. Compared with previous studies that relied mainly on trial and error for evaluation, this is the first time that dipole moment was proposed to optimize the electron-mediated Fc-Chit, demonstrating sturdy immobilization of glucose oxidase (GOx) on the electrode and improving the electron transfer process. Thus, the superior sensing sensitivity of the biosensor can achieve 119.97 μA mM-1 cm-2 in phosphate buffered saline (PBS) solution over a wide sensing range of 20-800 μM. Additionally, the biosensor exhibited high stability (retaining 95.0% after three weeks) and high specificity toward glucose in the presence of various interferents, attributed to the specific sites enabling GOx to be sturdily immobilized on the electrode. The results not only provide a facile solution for accurate and regular screening of blood glucose levels via saliva tests but also pave the way for designing enzymatic biosensors with specific enzyme immobilization through fundamental quantum calculations.

Review on rewiring of microalgal strategies for the heavy metal remediation - A metal specific logistics and tactics

Phycoremediation of heavy metals are gaining much attention and becoming an emerging practice for the metal removal in diverse environmental matrices. Still, the physicochemical state of metal polluted sites is often found to be complex and haphazard in nature due to the irregular discharge of wastes, that leads to the lack of conjecture on the application of microalgae for the metal bioremediation. Besides, the foresaid issues might be eventually ended up with futile effect to the polluted site. Therefore, this review is mainly focusing on interpretative assessment on pre-existing microalgal strategies and their merits and demerits for selected metal removal by microalgae through various process such as natural attenuation, nutritional amendment, chemical pretreatment, metal specific modification, immobilization and amalgamation, customization of genetic elements and integrative remediation approaches. Thus, this review provides the ideal knowledge for choosing an efficient metal remediation tactics based on the state of polluted environment. Also, this in-depth description would provide the speculative knowledge of counteractive action required for pass-over the barriers and obstacles during implementation. In addition, the most common metal removal mechanism of microalgae by adsorption was comparatively investigated with different metals through the principal component analysis by grouping various factor such as pH, temperature, initial metal concentration, adsorption capacity, removal efficiency, contact time in different microalgae. Conclusively, the suitable strategies for different heavy metals removal and addressing the complications along with their solution is comprehensively deliberated for metal removal mechanism in microalgae.

Nanostructured electrodes based on multiwalled carbon nanotube/glyconanoparticles for the specific immobilization of bilirubin oxidase: Application to the electrocatalytic O2 reduction

Here we describe the design and the characterization of novel electrode materials consisting of multi-walled carbon nanotubes coated with glyconanoparticles (GNPs) functionalized with anthraquinone sulfonate. The resulting modified electrodes were characterized by scanning electron microscopy and cyclic voltammetry. Their electrochemical behavior reveals a stable pH-dependent redox signal characteristic of anthraquinone sulfonate. Immobilization of bilirubin oxidase on these three-dimensional electrodes leads to the electroenzymatic reduction of O2 to water with an onset potential of 0.5 V/SCE (saturated calomel electrode). A catalytic cathodic current of 174 µA (0.88 mA cm−2) at 0.1 V/SCE, demonstrates that glyconanoparticles modified by anthraquinone sulfonate were able to interact and orientate bilirubin oxidase by electrostatic interactions.

Stabilization of enzymes for biotechnological applications

The biotechnological applications use stable and eco-friendly biocatalysts, with good operational properties, reusable and easily separable. An efficient method of improving the stability of enzymes as biocatalysts may be the immobilization. The enzymes immobilization research objectives are obtaining stable and versatile insoluble enzyme preparations with high enzymatic activity, capable of catalyzing the reactions of their natural and unnatural substrates. If active and stable water – insoluble enzymes, immobilized enzymes having appropriate substrate specificity can be obtained, it becomes possible to use enzymes conveniently in the same way as ordinary solid catalysts in synthetic biochemical reactions. In addition, since enzymes can catalyse specific reactions under mild conditions (normal temperature and pressure), application of immobilized enzymes in large scale bioconversion processes can reduce energy requirements. For some specific applications simple immobilization methods can be used. To increase the catalytic efficiency of immobilized enzyme preparations combinations of these methods can be handled to maximize the advantages presented by them. The physico-chemical properties of the supports used for enzymes immobilization influence the enzymatic activity and the immobilization yields of the immobilized preparations. The aimed of this work was to find efficient methods to stabilize enzymatic preparations with a good balance between costs associated and biocatalytic efficiency.

Terahertz subwavelength sensing with bio-functionalized germanium fano-resonators

Abstract Localized Surface Plasmon Resonances (LSPR) based on highly doped semiconductors microstructures, such as antennas, can be engineered to exhibit resonant features at THz frequencies. In this work, we demonstrate plasmonic antennas with increased quality factor LSPRs from Fano coupling to dark modes. We also discuss the advances in the biofunctionalization of n-doped Ge antennas for specific protein immobilization and cell interfacing. Finally, albumin biolayers with a thickness of a few hundred nanometers are used to demonstrate the performance of the fano-coupled n-Ge antennas as sensors. A resonant change of over 10% in transmission, due to the presence of the biolayer, can be detected within a bandwidth of only 20 GHz.

Covalent Immobilization of Aldehyde and Alcohol Dehydrogenases on Ordered Mesoporous Silicas

PurposeThis work studies the immobilization of two enzymes, the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (AldDH) both from Saccharomyces cerevisiae, which could be used to produce high value-added molecules from carboxylic acids embedded in anaerobic digestate.MethodsIn particular, three mesoporous siliceous materials, with different specific surface areas and pore sizes, (MSU-H, MSU-F and MCF0.75) were used as supports for covalent immobilization. The support materials were characterized by complementary techniques. Then, after a functionalization, creating a covalent bond between the enzyme and the support was performed. The specific activity and immobilization yield of the biocatalysts were then evaluated.ResultsThe best results were obtained with MSU-H and MSU-F, resulting in an immobilization yield greater than 50% in all cases, a specific activity of 0.13 IU/gsupp with the AldDH/MSU-H, 0.10 IU/gsupp with AldDH/MSU-F, 48.6 IU/gsupp with ADH/MSU-H and 12.6 IU/gsupp with ADH/MSU-H. These biocatalysts were then characterized by optimal pH and temperature and the stability factor was evaluated. With ADH/MSU-F no decrease in activity was observed after 120 h incubated at 50 °C. Finally, the biocatalysts AldDH/MSU-H and ADH/MSU-H were used to perform the reduction reaction and it was seen that after five reaction cycles the residual activity was greater than 20% in both cases.ConclusionThe ADH and AldDH enzymes have been successfully immobilized on mesoporous siliceous supports, considerably increasing their thermal stability and being able to reuse them for several reaction cycles. The use of this immobilization and these supports is adaptable to a wide variety of enzymes.Graphical