A novel approach for efficient immobilization and stabilization of papain on magnetic gold nanocomposites

Green immobilization: Enhancing enzyme stability and reusability on eco-friendly support

In the current years of heightened focus on green chemistry and sustainable materials, this study delves into the untapped potential of hyaluronic acid (HA), chitin, and chitosan-prominent polysaccharides for groundbreaking applications. The primary aim is to effectively immobilize catalase enzymes onto matrices composed of chitosan, chitin, HA/chitin, and HA/chitosan. The rigorous investigation covers a spectrum of structural enhancements encompassing pH and temperature stability, thermal resilience, half-life extension, storage durability, reusability, and comprehensive FTIR analyses of the catalase immobilization. Notably, catalase activity demonstrated remarkable resilience on HA/chitin and HA/chitosan matrices, maintaining 73.80% and 79.55% efficacy even after 25 cycles. The introduction of covalent cross-linking between catalase and HA/chitin or HA/chitosan, facilitated by a cross-linking agent, significantly amplified stability and recycling efficiency. Consequently, the immobilized catalase showcases substantial promise across a spectrum of industrial applications, spanning from food and detergent production to bioremediation and diverse commercial processes. This underscores its pivotal role as a versatile and invaluable innovation in the realm of sustainable technologies.

The Relationship Between the Cross-Linker on Chitosan-Coated Magnetic Nanoparticles and the Properties of Immobilized Papain

The immobilized enzymes' properties can be affected by cross-linkers on the surface of supports. To study how cross-linkers alter enzymes function, chitosan-coated magnetic nanoparticles (CMNPs) with immobilized papain were prepared using glutaraldehyde and or genipin, and then, the properties of the nanoparticles and the immobilized enzymes were assessed. The Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), and X-Ray Diffraction (XRD) results showed that the CMNPs were prepared and papain molecules were immobilized on CMNPs by glutaraldehyde (CMNP-Glu-Papain) or by genipin (CMNP-Gen-Papain). Also, the results associated with enzymes activity indicated that the immobilization by glutaraldehyde and genipin increased the pH optimum of papain from 7 to 7.5 and 9, respectively. The kinetic results indicated that the immobilization by genipin slightly affects the enzyme affinity to the substrate. The stability results showed that CMNP-Gen-Papain has more thermal stability than CMNP-Glu-Papain and papain immobilization on CMNPs by genipin leads to stabilization of the enzyme in the presence of polar solvents, probably due to the more hydroxyl groups on CMNPs activated by genipin. In conclusion, this study suggests that there is a relationship between the types of cross-linker on the surface of supports, and the mechanism of action, kinetic parameters, and the stability of immobilized papain.

Structural Transitions of Papain-like Cysteine Proteases: Implications for Sensor Development

The significant role of papain-like cysteine proteases, including papain, cathepsin L and SARS-CoV-2 PLpro, in biomedicine and biotechnology makes them interesting model systems for sensor development. These enzymes have a free thiol group that is suitable for many sensor designs including strong binding to gold nanoparticles or low-molecular-weight inhibitors. Focusing on the importance of the preservation of native protein structure for inhibitor-binding and molecular-imprinting, which has been applied in some efficient examples of sensor development, the aim of this work was to examine the effects of the free-thiol-group's reversible blocking on papain denaturation that is the basis of its activity loss and aggregation. To utilize biophysical methods common in protein structural transitions characterization, such as fluorimetry and high-resolution infrared spectroscopy, low-molecular-weight electrophilic thiol blocking reagent S-Methyl methanethiosulfonate (MMTS) was used in solution. MMTS binding led to a two-fold increase in 8-Anilinonaphthalene-1-sulfonic acid fluorescence, indicating increased hydrophobic residue exposure. A more in-depth analysis showed significant transitions on the secondary structure level upon MMTS binding, mostly characterized by the lowered content of α-helices and unordered structures (either for approximately one third), and the increase in aggregation-specific β-sheets (from 25 to 52%) in a dose-dependant manner. The recovery of this inhibited protein showed that reversibility of inhibition is accompanied by reversibility of protein denaturation. Nevertheless, a 100-fold molar excess of the inhibitor led to the incomplete recovery of proteolytic activity, which can be explained by irreversible denaturation. The structural stability of the C-terminal β-sheet rich domain of the papain-like cysteine protease family opens up an interesting possibility to use its foldamers as a strategy for sensor development and other multiple potential applications that rely on the great commercial value of papain-like cysteine proteases.

Multipoint Immobilization at Inert Center of Papain on Homo-Functional Diazo-Activated Silica Support: A Way of Restoring "Above Room-Temperature" Bio-Catalytic Sustainability

Although enzymes play a significant role in industrial applications, their potential usage at high-level efficiency, particularly above room temperature, has not yet been fully harnessed. It brings above room-temperature catalytic sustainability of an immobilized (imm.) bio-catalyst as a long pending issue to improve enzyme stability, activity, specificity, or selectivity, particularly the enantio-selectivity over the native-enzymes. At this juncture, in a robust methodology, a heterogeneous solid phase bio-catalyst, {Si(OSi)₄(H₂O)_1.03}_n=328{OSi(CH₃)₂-NH-C₆H₄-N═N}₄{papain}(H₂O)₂₅₁, has efficiently been prepared by immobilizing papain on homo-functionalized SG (silica-gel) via multipoint covalent attachment. The bio-catalyst is easy to be recovered and reused multiple times. The homo-functional -N═N⁺, which appears on the SG-surface, makes the multipoint diazo-links with the inert center of the tyrosine-moiety to couple the enzyme where all the amino, thiol, phenol, and so forth, groups of the protein, including those that belong to the active-site, remain intact. The immobilized enzyme (13.9 μmol g^-1) swims in pore-water within the pore-channel, remains stable up to 70 ± 5 °C, and exhibits wider temperature adaptability in performing its hydrolyzing activities. The relative activity, 78 ± 2% at 27 °C, remains quantitative for 60 days and can be reused for 60 cycles with 53% activity at room-temperature. The thermal (relative activity: 87%; incubated at 70 ± 5 °C for 24 h) and mechanical (relative activity: 92%; incubated at 2500 rpm for 2 h at 27 °C) stability was outstanding.

Hybridization of papain molecules and DNA-wrapped single-walled carbon nanotubes evaluated by atomic force microscopy in fluids

Although various conjugates of single-walled carbon nanotubes (SWNTs) and biomolecules, such as nanobiosensors and nanobiodevices, have been reported, the conjugation of papain and SWNTs have not been reported because of the formation of unexpected aggregates. In this study, atomic force microscopy (AFM) in liquid was used to investigate the interactions between papain and DNA-wrapped SWNTs (DNA-SWNTs) at two different pH values (pH 3.0 and 10.5). The direct AFM observation of the mixture of papain and DNA-SWNTs confirmed the aggregation of papain molecules with DNA-SWNTs in the buffer solutions. The numerous and non-uniform adsorption of papain molecules onto DNA-SWNTs was more pronounced at pH 3.0 than that at pH 10.5. Furthermore, thick conjugates appeared when papain and DNA-SWNTs were simultaneously mixed. The near-infrared photoluminescence spectra of the SWNTs drastically changed when the papain molecules were injected into the DNA-SWNT suspension at pH 3.0. Thus, the regulation of electrostatic interactions is a key aspect in preparing optimal conjugates of papain and DNA-SWNTs. Furthermore, although previous papers reported AFM images of dried samples, this study demonstrates the potential of AFM in liquid in evaluating individual bioconjugates of SWNTs.

Immobilization of papain: A review

Papain is a cysteine protease from papaya, with many applications due to its broad specificity. This paper reviews for first time the immobilization of papain on different supports (organic, inorganic or hybrid supports) presenting some of the features of the utilized immobilization strategies (e.g., epoxide, glutaraldehyde, genipin, glyoxyl for covalent immobilization). Special focus is placed on the preparation of magnetic biocatalysts, which will permit the simple recovery of the biocatalyst even if the medium is a suspension. Problems specific to the immobilization of proteases (e.g., steric problems when hydrolyzing large proteins) are also defined. The benefits of a proper immobilization (enzyme stabilization, widening of the operation window) are discussed, together with some artifacts that may suggest an enzyme stabilization that may be unrelated to enzyme rigidification.

Evaluation of antiplasmodial activity and cytotoxicity assays of amino acids functionalized magnetite nanoparticles: Hyperthermia and flow cytometry applications

We report the synthesis of magnetite nanoparticles (MNP) and their functionalization with glycine (MNPGly), β-alanine (MNPAla), L-phenylalanine (MNPPhAla), D-(-)-α-phenylglycine (MNPPhGly) amino acids. The functionalized nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), vibrating sample magnetometry (VSM), Mössbauer spectroscopy (MS), magnetic hyperthermia (MH), dynamic light scattering and zeta potential. The functionalized nanoparticles had isoelectric points (IEP) at pH ≃ 4.4, 5.8, 5.9 and 6.8 for samples MNPGly, MNPAla, MNPPhGly and MNPPhAla, respectively, while pure magnetite had an IEP at pH 5.6. In the MH experiments, the samples showed specific absorption rate (SAR) of 64, 71, 74, 81 and 66 W/g for MNP, MNPGly, MNPAla, MNPPhGly, and MNPPhAla, respectively. We used a flow cytometric technique to determine the cellular magnetic nanoparticles plus amino acids content. Magnetic fractionation and characterization of Resovist® magnetic nanoparticles were performed for applications in magnetic particle imaging (MPI). We have also studied the antiproliferative and antiparasitic effects of functionalized MNPs. Overall, the data showed that the functionalized nanoparticles have great potential for using as environmental, antitumor, antiparasitic agents and clinical applications.

Various type immobilizations of Isocitrate dehydrogenases enzyme on hyaluronic acid modified magnetic nanoparticles as stable biocatalysts

Magnetic nanoparticles (MNPs) were modified by hyaluronic acid (HA). After the process of functionalization, two different strategies have been used to immobilize isocitrate dehydrogenases (IDH) on MNPs. In the first strategy, cross-linked enzyme aggregates were prepared. For this, firstly hyaluronic acid modified magnetic nanoparticles cross-linked enzyme fine aggregates of isocitrate dehydrogenases (IDH/HA/MNPs-CLEAs) were synthesized, and secondly bovine serum albumin (BSA) as co-feeder was used to synthesize the IDH/BSA/HA/MNPs-CLEAs. In the second strategy, the IDH was effectively immobilized on the HA/MNPs surface. The features of MNPs and its derivatives have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and zeta potential measurements. The activity and stability of IDH in IDH/HA/MNPs, IDH/HA/MNPs-CLEAs, and IDH/BSA/HA/MNPs-CLEAs were enhanced. Besides, the enzyme immobilized was readily separated via external magnet from the reaction medium and reused many times. The acquired findings indicate that HA/MNPs are a novel binder/support system to IDH, and IDH immobilized on this system can become a very important biocatalyst working with high accuracy and sensitivity for the determination of magnesium in drinking water and other biological solutions.

Immobilization of dihydroflavonol 4-reductase on magnetic Fe3O4–PEI-pMaltose nanomaterials for the synthesis of anthocyanidins

An Fe3O4–PEI-pMaltose-immobilized DFR enzyme was prepared using nano-biotechnology, which can catalyze the synthesis of anthocyanidins in vitro.

Enhanced enzymatic activity and stability by in situ entrapment of α-Glucosidase within super porous p(HEMA) cryogels during synthesis

Here, poly(2-hydroxyethyl methacrylate) (p(HEMA)) cryogel were prepared in the presence 0.48, 0.96, and 1.92 mL of α-Glucosidase enzyme (0.06 Units/mL) solutions to obtain enzyme entrapped superporous p(HEMA) cryogels, donated as α-Glucosidase@p(HEMA)-1, α-Glucosidase@p(HEMA)-2, and α-Glucosidase@p(HEMA)-3, respectively. The enzyme entrapped p(HEMA) cryogels revealed no interruption for hemolysis and coagulation of blood rendering viable biomedical application in blood contacting applications. The α-Glucosidase@p(HEMA)-1 was found to preserve its' activity% 92.3 ± 1.4 % and higher activity% against free α-Glucosidase enzymes in 15-60℃ temperature, and 4-9 pH range. The Km and Vmax values of α-Glucosidase@p(HEMA)-1 cryogel was calculated as 3.22 mM, and 0.0048 mM/min, respectively versus 1.97 mM, and 0.0032 mM/min, for free enzymes. The α-Glucosidase@p(HEMA)-1 cryogel was found to maintained enzymatic activity more than 50 % after 10 consecutive uses, and also preserved their activity more than 50 % after 10 days of storage at 25 ℃, whereas free α-Glucosidase enzyme maintained only 1.9 ± 0.9 % activity under the same conditions.

Exploring the antioxidant effects of peptides from almond proteins using PAni-Ag-GONC conjugated trypsin by improving enzyme stability & applications

Functionalized graphene oxide nano-sheets (PAni-Ag-GONC) were prepared and employed as carrier for covalent immobilization of trypsin. This low cost setting, which involves loading of high amount of enzyme on the matrix, displayed significantly enhanced thermo-stability and pH resistance. The nano-composite (NC) bound trypsin preserved 90% of activity whereas native trypsin retained only 44% of activity after 60 days of storage at a temperature of 4°C. Immobilized trypsin conserved 80.5% of activity even after its ten repeated uses. Almond protein hydrolysates prepared by native and conjugated enzyme was investigated for antioxidant activities and found that peptides resulted from NC bound trypsin displayed increase in radical scavenging activity (i.e. around 30% and 37% scavenging activity observed, respectively by native and NC bound trypsin from same concentration of peptides). This strategy provides a new approach for production of potential biopeptides which may be incorporated in drugs and functional food industries applying PAni-Ag-GONC based biocatalysis. CHEMICAL COMPOUNDS: Trichloroacetic acid (PubChem CID: 6421); Tris (hydroxymethyl)aminomethane (PubChem CID: 6503); Glycine (PubChem CID: 750); and 2,2'-diphenyl-1-picrylhydrazyl (PubChem CID: 74358); Nα- Benzoyl-DL-arginine 4-nitroanilide hydrochloride (PubChem CID: 2724371); Ammonium sulphate (PubChem CID: 6097028).

Covalent immobilization of papain onto poly(hydroxyethyl methacrylate)-chitosan cryogels for apple juice clarification

Enzyme immobilization appears as a remarkable technique to safely attach enzymes for several applications and cryogels stand as promising support materials to be used in such investigations. In this work, papain enzyme was immobilized onto an interpenetrating network obtained by cryogelation of N,N′-methylenebisacrylamide cross-linked 2-hydroxyethyl methacrylate and glutaraldehyde cross-linked chitosan. Cryogels were modified with –NH2 functionality and glutaraldehyde in order to attach papain covalently. Immobilization was carried out at 25 ℃ in 0.1 M pH 7.0 phosphate buffer at 1.0 mg/ml enzyme concentration for 5 h. The amount of papain immobilized onto cryogel was calculated to be 15.2 ± 2.54 mg/g cryogel. Macroporous structure and surface area were determined by scanning electron microscopy and Brunauer–Emmett–Teller techniques, respectively. Energy dispersive X-ray analysis showed that papain was bound to the cryogel and cryogel structure was composed of 2-hydroxyethyl methacrylate, chitosan, and glutaraldehyde. Proteolytic activities of free and immobilized papain were measured using casein as substrate. Optimum pH values and temperatures were 8.0 and 65 ℃ for free and immobilized enzymes and kinetic parameters were calculated at these conditions. Reusability and storage stability results indicated that immobilization enhanced the stability of papain compared to free form. Efficiency of immobilized papain was demonstrated by apple juice clarification study as an industrial use of the enzyme. Phenolic compound, protein, total soluble solid contents, and viscosity of apple juice before and after clarification were determined.

Quantum Dots and Gold Nanoparticles as Scaffolds for Enzymatic Enhancement: Recent Advances and the Influence of Nanoparticle Size

Nanoparticle scaffolds can impart multiple benefits onto immobilized enzymes including enhanced stability, activity, and recoverability. The magnitude of these benefits is modulated by features inherent to the scaffold–enzyme conjugate, amongst which the size of the nanoscaffold itself can be critically important. In this review, we highlight the benefits of enzyme immobilization on nanoparticles and the factors affecting these benefits using quantum dots and gold nanoparticles as representative materials due to their maturity. We then review recent literature on the use of these scaffolds for enzyme immobilization and as a means to dissect the underlying mechanisms. Detailed analysis of the literature suggests that there is a “sweet-spot” for scaffold size and the ratio of immobilized enzyme to scaffold, with smaller scaffolds and lower enzyme:scaffold ratios generally providing higher enzymatic activities. We anticipate that ongoing studies of enzyme immobilization onto nanoscale scaffolds will continue to sharpen our understanding of what gives rise to beneficial characteristics and allow for the next important step, namely, that of translation to large-scale processes that exploit these properties.

Encapsulated functionalized stereocomplex PLA particles: An effective system to support mucolytic enzymes

In this work, the preparation of a novel enzyme carrier based on a polymer multicomponent system was assessed. Indeed, the design of the above system considered several issues that are the need of applying a biodegradable polymer carrier, characterized by a nanometric dimension, thus suitable to diffuse into the dense mucus structure, with functionalities capable of interacting/reacting with enzymes but resistant to enzymatic degradation. The particles were prepared from solutions containing equimolar amount of high-molecular-weight poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) and by applying the nanoprecipitation method. Dynamic Light Scattering (DLS) measurements allowed to establish the optimal preparation conditions to obtain polymer particles characterized by diameters lower than 1 μm, which dimensions were confirmed by Field Emission Scanning Electron Microscope (FE-SEM) analysis. In order to produce surface functionalization, necessary for anchoring enzymes, the stereocomplexed particles, whose structuration was confirmed by Differential Scanning Calorimetry (DSC) measurements, underwent an amminolysis reaction by using a diamine as reactant. The treated particles were characterized by means of FE-SEM, Fourier-Transform Infrared Spectroscopy (FTIR), DLS and zeta potential measurements and their characteristics were compared with those of the neat PLLA/PDLA particles. The degree of functionalization turned out to depend on the applied conditions, it increasing by enhancing the reaction time. The activity of enzymes, i.e. papain and alginate lyase, anchored to the particles, was evaluated by Quartz Crystal Microbalance (QCM) and UV measurements. Moreover, with the aim at exploiting the material for an inhalation administration, a method to encapsulate the enzyme-particles systems was assessed. Conversely to free enzymes, the developed systems were found to be capable of diminishing the viscosity of two hydrogels, ad hoc prepared and based on the main constituents of the real mucus.

Enzyme self-assembly on naked iron oxide nanoparticles for aminoaldehyde biosensing

The preservation of enzymatic activity is a fundamental requirement for exploiting hybrid nano-bio-conjugates, and the control over protein-nanoparticle interactions, leading to stable and catalytically active hybrids, represents the key for designing new biosensing platforms. In this scenario, surface active maghemite nanoparticles (SAMNs) represent a new class of naked magnetic nanoparticles, displaying peculiar electrocatalytic features and the ability to selectively bind proteins. Recombinant aminoaldehyde dehydrogenase from tomato (SlAMADH1) was used as a model protein, and successfully immobilized by self-assembly on the surface of naked SAMNs, where its enzymatic activity resulted preserved for more than 6 months. The hybrid nanomaterial (SAMN@SlAMADH1) was characterized by UV-Vis spectroscopy, mass spectrometry, and TEM microscopy, and applied for the development of a biosensor for the determination of aminoaldehydes in alcoholic beverages. Measurements were carried out in a low volume electrochemical flow cell comprising a SAMN modified carbon paste electrode for the coulometric determination of the NADH produced during the enzymatic catalysis. The present findings, besides representing the first example of an electrochemical biosensor for aminoaldehydes in an alcoholic matrix, open the door to the use of immobilized enzymes on naked metal oxides nanomaterials for biosensing.

Highly active nanobiocatalysis in deep eutectic solvents via metal-driven enzyme-surfactant nanocomposite

Metal-driven papain-surfactant nanocomposite (PA@MSNC), a novel soft nanobiocatalyst, was successfully prepared via one-pot self-assembly technique in aqueous solution for the biosynthesis of N-(benzyloxycarbonyl)-L-alanyl-L-glutamine (Z-Ala-Gln) dipeptide in deep eutectic solvents (DESs). The metal-driven self-assembly process generated PA@MSNC as nanospheres of ˜130 nm in diameter, with high protein loading and relative enzyme activity of 420 mg/g and 80% (4270 U/g protein), respectively. PA@MSNC showed high apparent substrate affinity and catalytic efficiency. The stability of PA@MSNC at high temperature and extreme pH was significantly higher than that of free PA. Catalysis efficiency for the biosynthesis of Z-Ala-Gln by PA@MSNC in choline chloride: glycerol reaction medium was 1.69-fold higher than that of free PA, achieving a high product yield of 75.7% within 4 h. PA@MSNC also showed better techno-economic performance. We propose that enzyme-surfactant nanocomposite via metal-driven dynamically reversible coordination interactions contribute simultaneously promotes catalytic flexibility and configurational stability. The generated PA@MSNC has potential practical implications for green synthesis of dipeptide in DESs.

Evaluation of different saccharides and chitin as eco-friendly additive to improve the magnetic cross-linked enzyme aggregates (CLEAs) activities

The cross-linked enzyme aggregates (CLEAs) involves formation of a number of covalent bonds between enzyme and the matrix using glutaraldehyde. In general, amino groups of lysine, sulfhydryl groups of cysteine, phenolic OH groups of tyrosine, or imidazol group of histidine are used for enzyme binding under mild conditions. The main advantage of this method is its simplicity, economic advantages in the industrial bio catalysis. The Fe₃O₄ magnetic nanoparticles were synthesized by coprecipitating Fe²⁺and Fe³⁺in alkaline solution. Tannic acid was used to functionalize the Fe₃O₄ magnetic nanoparticles. After functionalization process, tannic acid magnetic cross-linked enzyme aggregates of enzyme (TA-MNPs-CLEAs) were prepared by cross-linking of enzyme aggregates with different saccharides as additive. The present result reported high stability, simplicity, low cost and recyclability of a saccharide-TA-MNPs-CLEAs-enzyme make it efficient as a highly active biocatalyst in biotechnological applications. The obtained results suggest that disaccharides (maltose, sucrose and lactose) and polysaccharide such as starch are eco-friendly additives to TA-MNPs-lipase and TA-MNPs-CLEAs-peroxidase and can become a powerful biocatalyst in industry applications.

An ultrasensitive chemiluminescence immunoassay for fumonisin B1 detection in cereals based on gold-coated magnetic nanoparticles

BACKGROUND

In the present study, a novel highly sensitive magnetic enzyme chemiluminescence immunoassay (MECLIA) was developed to detect fumonisin B₁ (FB₁ ) in cereal samples. The gold-coated magnetic nanoparticles (Fe₃ O₄ @Au, GoldMag) were used as solid phase carrier to develop a competitive CLIA for detecting FB₁ , in which FB₁ in samples would compete with FB₁ -ovalbumin coated on the surface of Fe₃ O₄ @Au nanoparticles for binding with FB₁ antibodies. Successively, horseradish peroxidase labeled goat anti-rabbit IgG (HRP-IgG) was conjugated with FB₁ antibodies on the microplate. In substrate solution containing luminol and H₂ O₂ , HRP-IgG catalyzed luminol oxidation by H₂ O₂ , generating a high chemiluminescence signal. The FB₁ immune GoldMag particles were characterized by Fourier transform infrared spectroscopy, scanning electron microscope and zeta potential analysis, etc. RESULTS: The concentrations and the reaction times of these immunoreagents were optimized to improve the performances of this method. The established method could detect as low as 0.027 ng mL^-1 FB₁ from 0.05 ng mL^-1 to 25 ng mL^-1 , demonstrating little cross-reaction (less than 2.4%) with other structurally related compounds. The average intrassay relative SD (RSD) (n = 6) was 3.4% and the average interassay RSD (n = 6) was 5.4%. This method was successfully applied for the determination of FB₁ in corn and wheat and gave recoveries of between 98-110% and 91-105%, respectively.

CONCLUSION

The results of the present study suggest that the MECLIA approach has potential application for high-throughput fumonisin screening in cereals. © 2018 Society of Chemical Industry.

Papain-functionalized gold nanoparticles as heterogeneous biocatalyst for bioanalysis and biopharmaceuticals analysis

Surface-modified gold nanoparticles (GNPs) were synthesized via layer-by-layer process with alternating cationic polyallylamine and anionic poly(acrylic acid) polyelectrolyte layers leading to a highly hydrophilic biocompatible shell supporting colloidal stability. Afterwards, papain was covalently immobilized on the modified GNPs via amide coupling between the amino groups on papain and the terminal carboxylic groups of the modified GNPs by using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide and N-hydroxysulfosuccinimide sodium as coupling agents. The resultant papain-functionalized gold nanoparticles were characterized by surface plasmon resonance, dynamic light scattering and zeta potential measurements. The new technology resonant mass measurement was applied for determining the average number of papain molecules immobilized per GNP by measurement of the single nanoparticle buoyant mass in the range of femtograms. The activity of the immobilized enzyme was estimated by determination of the kinetic parameters (K_m, V_max and k_cat) with the standard chromogenic substrate N_α-benzoyl-dl-arginine-4-nitroanilide hydrochloride. It was found that K_m of immobilized and free enzyme are in the same order of magnitude. On contrary, turnover numbers k_cat were significantly higher for GNP-conjugated papain. Further, the gold nanobiocatalyst was applied for digestion of polyclonal human immunoglobulin G to yield protein fragments. The resultant fragment mixture was further analyzed by high-performance liquid chromatography-microelectrospray ionization-quadrupole-time-of-flight mass spectrometry, which demonstrated the applicability of the bioreactor based on papain functionalized GNPs. The immobilized papain not only has higher catalytic activity and better stability, but also can be easily isolated from the reaction medium by straightforward centrifugation steps for reuse.

Papain/Zn3(PO4)2 hybrid nanoflower: preparation, characterization and its enhanced catalytic activity as an immobilized enzyme

Flower-like papain/Zn₃(PO₄)₂ hybrid materials are synthesized via a facile, rapid and low-cost method in this study.

Fabrication of a magnetic nanoparticle embedded NH2-MIL-88B MOF hybrid for highly efficient covalent immobilization of lipase

We demonstrate an approach to synthesize an amine-functionalized magnetic metal-organic framework (MOF) for lipase immobilization. The activity of immobilized lipase is enhanced by different parameters like pH, temperature and thermal stability.