Three-dimensional immobilization of β-galactosidase on a silicon surface

Harnessing the power of thermosensitive liposomes with gold nanoprisms and silica for controlled drug delivery in combined chemotherapy and phototherapy

In recent years, the scientific community has tried to address the treatment of complex diseases such as cancer in a more appropriate and promising way. Regarding this and benefiting from the unique optical properties of gold nanoprisms (AuNPRs), the physicochemical properties of thermosensitive liposomes (TSLs), and the tunable drug encapsulation and release properties of silica nanoparticles (BioSi@NPs), this study has developed two nanoformulations. These nanoformulations have the potential to integrate chemotherapy and photothermal therapy within a single entity. Once their components were synthesized and characterized separately, two strategies were taken in order to develop these multifunctional nanoformulations: (1) covalent binding of AuNPRs to TSLs and (2) co-encapsulation of both components within BioSi@NPs, without modifying the optical and physicochemical properties of AuNPRs and TSLs. Finally, the suitability of both nanoformulations to carry and release hydrophilic drugs when triggered by a 1064 nm NIR laser has been explored by using the fluorescent probe 5(6)-carboxyfluorescein (CF) as a hydrophilic drug model. Different laser power and time of exposure were also tested evidencing that hydrophilic drugs were only released from TSLs in the presence of AuNPRs and that the drug release profile was dependent on the type of nanoformulation and irradiation conditions used. In conclusion, these multifunctional nanoformulations exhibit promising potential for controlled drug delivery in combined chemotherapy and phototherapy, with the capability to precisely control the release kinetics based on specific therapeutic needs.

Carbohydrate microcapsules tailored and grafted for covalent immobilization of glucose isomerase for pharmaceutical and food industries

Carrageenan is one of the most common carbohydrates utilised in the entrapment industry to immobilise cells and enzymes. However, it lacks functionality. Carrageenan has been grafted to produce fructose by covalently immobilising glucose isomerase (GI). Fructose is one of the most widely used sweeteners in beverages, food production, and the pharmaceutical business. Up to 91.1 U g^-1 gel beads are immobilised by the grafted beads. Immobilized GI has a V_max of 13.8 times that of the free enzyme. pH of immobilized GI was improved from 6.5-7 to 6-7.5 that means more stability in wide pH range. Also, optimum temperature was improved and become 65-75 °C while it was at 70 °C for free enzyme. The immovability and tolerance of the gel beads immobilised with GI over 15 consecutive cycles were demonstrated in a reusability test, with 88 percent of the enzyme's original activity retained, compared to 60 percent by other authors. These findings are encouraging for high-fructose corn syrup producers.

Stabilization of β-Galactosidase on Modified Gold Nanoparticles: A Preliminary Biochemical Study to Obtain Lactose-Free Dairy Products for Lactose-Intolerant Individuals

The unique chemical, optical, and electrical characteristics of nanoparticles make their utilization highly successful in every field of biological sciences as compared to their bulk counterpart. These properties arise as a result of their miniature size, which provides them an excellent surface area-to-volume ratio, inner structure, and shape, and hence increases their surface characteristics. Therefore, this study was undertaken to engineer gold nanoparticles (AuNPs) for improving their catalytic activity and stability in biotechnological processes. The characterization of AuNPs was performed by XRD, UV spectra, and TEM. The synthesized AuNPs were surface-modified by polyvinyl alcohol (PVA) for binding the enzyme in excellent yield. The developed immobilized enzyme system (PVA-AuNPs-β-galactosidase) displayed pH optima at pH 7.0 and temperature optima at 40 °C. Moreover, the stability of PVA-AuNPs-β-galactosidase was significantly enhanced at wider pH and temperature ranges and at higher galactose concentrations, in contrast to the free enzyme. β-galactosidase bound to PVA-modified AuNPs exhibited greater operational activity, even after its sixth reuse. The developed nanosystem may prove useful in producing lactose-free dairy products for lactose-intolerant patients.

A Spring in Performance: Silica Nanosprings Boost Enzyme Immobilization in Microfluidic Channels

Enzyme microreactors are important tools of miniaturized analytics and have promising applications in continuous biomanufacturing. A fundamental problem of their design is that plain microchannels without extensive static internals, or packings, offer limited exposed surface area for immobilizing the enzyme. To boost the immobilization in a manner broadly applicable to enzymes, we coated borosilicate microchannels with silica nanosprings and attached the enzyme, sucrose phosphorylase, via a silica-binding module genetically fused to it. We showed with confocal fluorescence microscopy that the enzyme was able to penetrate the ∼70 μm-thick nanospring layer and became distributed uniformly in it. Compared with the plain surface, the activity of immobilized enzyme was enhanced 4.5-fold upon surface coating with nanosprings and further increased up to 10-fold by modifying the surface of the nanosprings with sulfonate groups. Operational stability during continuous-flow biocatalytic synthesis of α-glucose 1-phosphate was improved by a factor of 11 when the microreactor coated with nanosprings was used. More than 85% of the initial conversion rate was retained after 840 reactor cycles performed with a single loading of enzyme. By varying the substrate flow rate, the microreactor performance was conveniently switched between steady states of quantitative product yield (50 mM) and optimum productivity (19 mM min^-1) at a lower product yield of 40%. Surface coating with silica nanosprings thus extends the possibilities for enzyme immobilization in microchannels. It effectively boosts the biocatalytic function of a microstructured reactor limited otherwise by the solid surface available for immobilizing the enzyme.

Encapsulation of Pancreatic Lipase in Hydrogel Beads with Self-Regulating Internal pH Microenvironments: Retention of Lipase Activity after Exposure to Gastric Conditions

Oral delivery of lipase is important for individuals with exocrine pancreatic insufficiency; however, lipase loses activity when exposed to the highly acidic gastric environment. In this study, pancreatic lipase was encapsulated in hydrogel beads fabricated from alginate (gel former), calcium chloride (cross-linker), and magnesium hydroxide (buffer). Fluorescence confocal microscopy imaging was used to map the pH microclimate within the hydrogel beads under simulated gastrointestinal tract (GIT) conditions. The pH within buffer-free beads rapidly decreased when they moved from mouth (pH 6.3) to stomach (pH <4), leading to a loss of lipase activity in the small intestine. Conversely, the pH inside buffer-loaded beads remained close to neutral in the mouth (pH 7.33) and stomach (pH 7.39), leading to retention of lipase activity in the small intestine, as shown by pH-stat analysis of lipid digestion. The presence of the encapsulated buffer also reduced bead shrinkage under gastric conditions.

Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed.

Production of an endoinulinase from Aspergillus niger AUMC 9375, by solid state fermentation of agricultural wastes, with purification and characterization of the free and immobilized enzyme

Two different substrates, sunflower (Helianthus annuus L.) tubers and lettuce (Lactuca sativa) roots, were tested. Using a mixture of both wastes resulted in higher production of endoinulinase than either waste alone. Also, ten fungal species grown on these substrates as inexpensive, carbon sources were screened for the best production of endoinulinase activities. Of these, Aspergillus niger AUMC 9375 was the most productive, when grown on the mixture using a 6:1 w/w ratio of sun flower: lettuce, and yielded the highest levels of inulinase at 50% moisture, 30°C, pH 5.0, with seven days of incubation, and with yeast extract as the best nitrogen source. Inulinase was purified to homogeneity by ion-exchange chromatography and gel-filtration giving a 51.11 fold purification. The mixture of sunflower tubers and lettuce roots has potential to be an effective and economical substrate for inulinase production. Inulinase was successfully immobilized with an immobilization yield of 71.28%. After incubation for 2 h at 60°C, the free enzyme activity decreased markedly to 10%, whereas that of the immobilized form decreased only to 87%. A reusability test demonstrated the durability of the immobilized inulinase for 10 cycles and in addition, that it could be stored for 32 days at 4°C. These results indicate that this inulinase, in the immobilized form, is a potential candidate for large-scale production of high purity fructose syrups.

Optimal immobilization of β-galactosidase onto κ-carrageenan gel beads using response surface methodology and its applications

β-Galactosidase (β-gal) was immobilized by covalent binding on novel κ-carrageenan gel beads activated by two-step method; the gel beads were soaked in polyethyleneimine followed by glutaraldehyde. 2² full-factorial central composite experiment designs were employed to optimize the conditions for the maximum enzyme loading efficiency. 11.443 U of enzyme/g gel beads was achieved by soaking 40 units of enzyme with the gel beads for eight hours. Immobilization process increased the pH from 4.5 to 5.5 and operational temperature from 50 to 55°C compared to the free enzyme. The apparent K_m after immobilization was 61.6 mM compared to 22.9 mM for free enzyme. Maximum velocity V_max was 131.2 μmol·min⁻¹ while it was 177.1 μmol·min⁻¹ for free enzyme. The full conversion experiment showed that the immobilized enzyme form is active as that of the free enzyme as both of them reached their maximum 100% relative hydrolysis at 4 h. The reusability test proved the durability of the κ-carrageenan beads loaded with β-galactosidase for 20 cycles with retention of 60% of the immobilized enzyme activity to be more convenient for industrial uses.

Combining the physical adsorption approach and the covalent attachment method to prepare a bifunctional bioreactor

Aminopropyl-functionalized SBA-15 mesoporous silica was used as a support to adsorb myoglobin. Then, in order to avoid the leakage of adsorbed myoglobin, lysozyme was covalently tethered to the internal and external surface of the mesoporous silica with glutaraldehyde as the coupling agent. The property of amino-functionalized mesoporous silica was characterized by N₂ adsorption-desorption and thermogravimetric (TG) analysis. The feature of the silica-based matrix before and after myoglobin adsorption was identified by fourier transform infrared (FTIR) and UV/VIS measurement. With o-dianisidine and H₂O₂ as the substrate, the peroxidase activity of adsorbed myoglobin was determined. With Micrococus lysodeilicus as the substrate, the antibacterial activity of covalently tethered lysozyme was measured. Results demonstrated that the final product not only presented peroxidase activity of the myoglobin but yielded antibacterial activity of the lysozyme.

Immobilization of β-galactosidase onto functionalized graphene nano-sheets using response surface methodology and its analytical applications

Background

β-Galactosidase is a vital enzyme with diverse application in molecular biology and industries. It was covalently attached onto functionalized graphene nano-sheets for various analytical applications based on lactose reduction.

Methodology/Principal Findings

Response surface methodology based on Box-Behnken design of experiment was used for determination of optimal immobilization conditions, which resulted in 84.2% immobilization efficiency. Native and immobilized functionalized graphene was characterized with the help of transmission and scanning electron microscopy, followed by Fourier transform infrared (FTIR) spectroscopy. Functionalized graphene sheets decorated with islands of immobilized enzyme were evidently visualized under both transmission and scanning electron microscopy after immobilization. FTIR spectra provided insight on various chemical interactions and bonding, involved during and after immobilization. Optimum temperature and energy of activation (E_a) remains unchanged whereas optimum pH and K_m were changed after immobilization. Increased thermal stability of enzyme was observed after conjugating the enzyme with functionalized graphene.

Significance

Immobilized β-galactosidase showed excellent reusability with a retention of more than 92% enzymatic activity after 10 reuses and an ideal performance at broad ranges of industrial environment.

Nanotube-supported bioproduction of 4-hydroxy-2-butanone via in situ cofactor regeneration

Nicotinamide cofactor-dependent oxidoreductases have been widely employed during the bioproduction of varieties of useful compounds. Efficient cofactor regeneration is often required for these biotransformation reactions. Herein, we report the synthesis of an important pharmaceutical intermediate 4-hydroxy-2-butanone (4H2B) via an immobilized in situ cofactor regeneration system composed of NAD(+)-dependent glycerol dehydrogenase (GlyDH) and NAD(+)-regenerating NADH oxidase (nox). Both enzymes were immobilized on functionalized single-walled carbon nanotubes (SWCNTs) through the specific interaction between the His-tagged enzymes and the modified SWCNTs. GlyDH demonstrated ca. 100% native enzyme activity after immobilization. The GlyDH/nox ratio, pH, and amount of nicotinamide cofactor were examined to establish the optimum reaction conditions for 4H2B production. The nanoparticle-supported cofactor regeneration system become more stable and the yield of 4H2B turned out to be almost twice (37%) that of the free enzyme system after a 12-h reaction. Thus, we believe that this non-covalent specific immobilization procedure can be applied to cofactor regeneration system for bioconversions.

Study of gherkin lactase in cell culture and in seedlings

A synthetic substrate replacing lactose has facilitated application of a simple, rapid and sensitive method for the identification and determination of extracellular and intracellular gherkin lactase. The intracellular enzyme activity was estimated from the cell suspension, while the extracellular enzyme activity was established within the cell free cultivation medium. A suspension of gherkin cells was permeabilized by Tween 20, or Tween 80, or hexadecyltrimethyl ammonium bromide, or hexadecylpyridinium chloride or ethanol added one at a time and then immobilized by glutaraldehyde. The highest lactase activity was at pH 4.8 at a temperature of 55°C. The hydrolysis of substrate was linear for 4.5h and reached 60% conversion. The cells had high lactase activity and good stability. During long-term storage they demonstrated convenient physico-mechanical properties.

Facile construction of multicompartment multienzyme system through layer-by-layer self-assembly and biomimetic mineralization

In nature, some organelles such as mitochondria and chloroplasts possess multicompartment structure, which render powerful and versatile performance in cascade conversion, selective separation, and energy transfer. In this study, mitochondria-inspired hybrid double membrane microcapsules (HDMMCs) were prepared through synergy between biomimetic mineralization and layer-by-layer (LbL) self-assembly using double templating strategy. The organic inner membrane was acquired via LbL self-assembly of oxidized alginate (o-alginate) and protamine on the CaCO(3) template, the silica template layer was then formed onto the inner membrane through biomimetic silicification using protamine as inducer and silicate as precursor, the organic-inorganic hybrid outer membrane was acquired via biomimetic mineralization of titanium precursor. After the CaCO(3) template and the silica template are removed subsequently, multicompartment microcapsules with microscale lumen and nanoscale intermembrane space were obtained. The double membrane structure of the HDMMCs was verified by high resolution scanning electron microscopy (HRSEM), and the superior mechanical stability of HDMMCs was demonstrated by osmotic pressure experiment and fluorescence microscopy. A multienzyme system was constructed by following this protocol: the first enzyme was encapsulated in the lumen of the HDMMCs, whereas the second enzyme was encapsulated in the intermembrane space. Compared to encapsulated multienzyme in single-compartment microcapsules (SCMCs) or in free form in aqueous solution, enzymatic activity, selectivity, and recycling stability of HDMMCs-enabled multienzyme system were significantly improved. Because of the inherent gentle and generic feature, the present study can be utilized to create a variety of compartment structures for the potential applications in chemical/biological catalysis and separation, drug/gene delivery systems, and biosensors.

Fabrication and activity of silicate nanoparticles and nanosilicate-entrapped enzymes using polyethyleneimine as a biomimetic polymer

In nature, some peptides induce precipitation of silicic acid into silica nanoparticles such as is found in marine algae called diatoms. However, polybasic polymers can act as peptide mimics; one such polymer, polyethyleneimine (PEI), has the advantage that it is stable at room temperature and is inexpensive, in comparison with synthetic peptides. We describe the fabrication and characterization of biosilicate nanoparticles formed by mimicking the peptides using PEI. Brownian motion nanoparticle tracking analysis and field emission gun scanning electron microscopy have been used for the first time to characterize nanoparticles made with tetramethyl orthosilicate (TMOS) and PEI to investigate the fundamental factors that affect particle properties. These factors include the effect of phosphate concentration, PEI molecular weight, TMOS concentration, and species of alkoxy-silane used. The properties of the particles are compared with other particles made with polymers that induce silication. Our results show that using PEI gives differences in particle size compared with previous work using other polymers that induce silication. The entrapment of enzymes during the silication process, rationale for using nonphosphate and phosphate buffers during enzyme entrapment, and the analysis of enzyme activity are also presented. Because enzymes can be entrapped during fabrication, it means that there are many future possibilities for the use of silicate nanoparticles containing enzymes, such as biosensors and biocatalytic reactors.

Fabrication and characterization of bioactive thiol-silicate nanoparticles

Here we describe a new method for the production of thiol-silicate particles and the entrapment of enzymes within the thiol particles as they are formed. When bio-inspired polymers (polyethyleneimine) are combined with a silicic acid source and phosphate buffer under pH neutral conditions, formation of silicate particles occurs. In the method presented here the silica source contains a thiol group and so therefore the silicate particles are pre-functionalized with thiol groups. We have termed the silicate particles produced "thiol particles" and the characterization of these thiol particles is also presented in this chapter. As enzymes can be entrapped during fabrication, it means that the thiol particles can not only attach to metal surfaces but also catalyse certain reactions depending on the enzyme used. This means that there are many future possibilities for the use of thiol particles containing enzymes, as they may be used in a wide range of processes and devices which require catalytic functionalized surfaces, such as biosensors and biocatalytic reactors.

Comparative characterization of the Arabidopsis subfamily a1 beta-galactosidases

The Arabidopsis genome contains 17 predicted beta-galactosidase genes, all of which belong to glycosyl hydrolase (GH) Family 35. These genes have been further grouped into seven subfamilies based on sequence similarity. The largest of these, subfamily a1, consists of six genes, Gal-1 (At3g13750), Gal-2 (At3g52840), Gal-3 (At4g36360), Gal-4 (At5g56870), Gal-5 (At1g45130), and Gal-12 (At4g26140), some of which were characterized in previous studies. We report here the purification and biochemical characterization of recombinant Gal-1, Gal-3, Gal-4 and Gal-12 from Pichiapastoris, completing the analysis of all six recombinant proteins, as well as the isolation and characterization of the native Gal-2 protein from Arabidopsis leaves. Comparison of the relative expression levels of the subfamily a1 beta-galactosidases at the mRNA and protein levels uncovered evidence of differential regulation, which may involve post-transcriptional and post-translational processes. In addition, this study provides further support for the proposed function of the subfamily a1 beta-galactosidases in cell wall modification based on analysis of the organ-specific expression and subcellular localization of Gal-1 and Gal-12. Our study suggests that, despite some differences in individual biochemical characteristics and expression patterns, each member of the family has the potential to contribute to the dynamics of the Arabidopsis plant cell wall.

Novel one-pot synthesis and characterization of bioactive thiol-silicate nanoparticles for biocatalytic and biosensor applications

A novel one-pot neutral synthesis using bioinspired polymers to fabricate thiol-nanoparticles is presented. The thiol-particles may be directly tethered to metal surfaces such as gold, allowing the production of self-assembled nanostructured biocatalytic or biosensor surfaces. This one-pot method has also been used to entrap enzymes within the thiol-nanoparticles; it is apparent that once enzyme entrapment is carried out a bimodal distribution of particles is formed, with particles of one mode being very similar in size to thiol-nanoparticles without enzyme entrapped, and particles of the other mode being much larger in size. To this end, efforts have been made to separate the two modes of particles for the sample containing enzyme and it has been observed that the larger mode thiol-nanoparticles do indeed contain significant amounts of enzyme in comparison to the smaller mode ones. As the enzyme-containing thiol-nanoparticles can now be isolated, this means that there are many future possibilities for the use of thiol-particles containing enzyme, as they may be used in a wide range of processes and devices which require catalytic functionalized surfaces, such as biosensors and biocatalytic reactors.

Lactose hydrolysis by beta-galactosidase covalently immobilized to thermally stable biopolymers

Lactose has been hydrolyzed using covalently immobilized beta-galactosidase on thermally stable carrageenan coated with chitosan (hydrogel). The hydrogel's mode of interaction was proven by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and Schiff's base formation. The DSC thermogram proved the formation of a strong polyelectrolyte complex between carrageenan and chitosan followed by glutaraldehyde as they formed one single peak. The modification of carrageenan improved the gel's thermal stability in solutions from 35 degrees C to 95 degrees C. The hydrogel has been proven to be efficient for beta-galactosidase immobilization where 11 U/g wet gel was immobilized with 50% enzyme loading capacity. Activity and stability of free and immobilized beta-galactosidase towards pH and temperature showed marked shifts in their optimum pH from 4.5-5 to 5-5.5 and temperature from 50 degrees C to 45-55 degrees C after immobilization, which reveals higher catalytic activity and reasonable stability at wider pHs and temperatures. The apparent K(m) of the immobilized enzyme increased from 13.2 to 125 mM, whereas the V(max) increased from 3.2 to 6.6 micromol/min compared to the free enzyme, respectively. The free and immobilized enzymes showed lactose conversion of 87% and 70% at 7 h, respectively. The operational stability showed 97% retention of the enzyme activity after 15 uses, which demonstrates that the covalently immobilized enzyme is unlikely to leach. The new carrier could be suitable for immobilization of other industrial enzymes.

Synthesis of bioinorganic antimicrobial peptide nanoparticles with potential therapeutic properties

Amphiphilicity and cationicity are properties shared between antimicrobial peptides and proteins that catalyze biomineralization reactions. Merging these two functionalities, we demonstrate a reaction where a cationic antimicrobial peptide catalyzes self-biomineralization within inorganic matrices. The resultant antimicrobial peptide nanoparticles retain biocidal activity, protect the peptide from proteolytic degradation, and facilitate a continuous release of the antibiotic over time. Taken together, these properties demonstrate the therapeutic potential of self-synthesizing biomaterials that retain the biocidal properties of antimicrobial peptides.