Horseradish peroxidase-nanoclay hybrid particles of high functional and colloidal stability

Optimization of Interfacial Properties Improved the Stability and Activity of the Catalase Enzyme Immobilized on Plastic Nanobeads

The immobilization of catalase (CAT), a crucial oxidoreductase enzyme involved in quenching reactive oxygen species, on colloids and nanoparticles presents a promising strategy to improve dispersion and storage stability while maintaining its activity. Here, the immobilization of CAT onto polymeric nanoparticles (positively (AL) or negatively (SL) charged) was implemented directly (AL) or via surface functionalization (SL) with water-soluble chitosan derivatives (glycol chitosan (GC) and methyl glycol chitosan (MGC)). The interfacial properties were optimized to obtain highly stable AL-CAT, SL-GC-CAT, and SL-MGC-CAT dispersions, and confocal microscopy confirmed the presence of CAT in the composites. Assessment of hydrogen peroxide decomposition ability revealed that applying chitosan derivatives in the immobilization process not only enhanced colloidal stability but also augmented the activity and reusability of CAT. In particular, the use of MGC has led to significant advances, indicating its potential for industrial and biomedical applications. Overall, the findings highlight the advantages of using chitosan derivatives in CAT immobilization processes to maintain the stability and activity of the enzyme as well as provide important data for the development of processable enzyme-based nanoparticle systems to combat reactive oxygen species.

Confinement of Triple-Enzyme-Involved Antioxidant Cascade in Two-Dimensional Nanostructure

Application of antioxidant enzymes in medical or industrial processes is limited due to their high sensitivity to environmental conditions. Incorporation of such enzymes in nanostructures provides a promising route to obtain highly efficient and robust biocatalytic system to scavenge reactive oxygen species (ROS). Here, this question was addressed by confinement of superoxide dismutase (SOD), horseradish peroxidase (HRP), and catalase (CAT) enzymes into nanostructures containing polyelectrolyte building blocks (alginate (Alg) and trimethyl chitosan (TMC)) and delaminated layered double hydroxide (dLDH) nanoparticle support. The nanocomposite possessed excellent structural and colloidal stability, while antioxidant tests revealed that the enzymes remained active upon immobilization and the developed composite greatly reduced intracellular oxidative stress in two-dimensional cell cultures. Moreover, it effectively prevented hydrogen peroxide-induced double stranded DNA breaks, which is a common consequence of oxidative stress. The results provide important tools to design complex nanostructures with multienzymatic antioxidant activities for ROS scavenging.

Development of polymer-based multifunctional composite particles of protease and peroxidase activities

A hybrid material (SL-PPN-HEP-HRP) of dual enzyme function was prepared by co-immobilization of papain (PPN) and horseradish peroxidase (HRP) on sulphate latex (SL) microspheres using heparin (HEP) polyelectrolyte as a building block in the sequential adsorption method. The doses of PPN, HEP and HRP were optimized in each step of the preparation process to achieve high functional and colloidal stability. The enzymes and the polyelectrolyte strongly adsorbed on the oppositely charged surfaces via electrostatic forces, and enzyme leakage was not observed from the hybrid material, as confirmed by colorimetric protein tests and microscopy measurements. It was found that the polyelectrolyte acted as a separator between PPN and HRP to prevent hydrolytic attack on the latter enzyme, which otherwise prevents the joint use of these important biocatalysts. Excellent colloidal stability was obtained for the SL-PPN-HEP-HRP composite and the embedded PPN and HRP showed remarkable protease and peroxidase activities, respectively, at least until five days after preparation. The present results offer a promising approach to develop biocatalytic systems of dual function, which are often required in manufacturing processes in the food industry, where the colloidal stability of such multifunctional materials is a key parameter to achieve remarkable efficiency.

Two-dimensional layered double hydroxide nanoadjuvant: recent progress and future direction

Layered double hydroxide (LDH) is a 'sandwich'-like two-dimensional clay material that has been systematically investigated for biomedical application in the past two decades. LDH is an alum-similar adjuvant, which has a well-defined layered crystal structure and exhibits high adjuvanticity. The unique structure of LDH includes positively charged layers composed of divalent and trivalent cations and anion-exchangeable interlayer galleries. Among the many variants of LDH, MgAl-LDH (the cationic ions are Mg2+ and Al3+) has the highest affinity to antigens, bioadjuvants and drug molecules, and exhibits superior biosafety. Past research studies indicate that MgAl-LDH can simultaneously load antigens, bioadjuvants and molecular drugs to amplify the strength of immune responses, and induce broad-spectrum immune responses. Moreover, the size and dispersity of MgAl-LDH in biological environments can be well controlled to actively deliver antigens to the immune system, realizing the rapid induction and maintenance of durable immune responses. Furthermore, the functionalization of MgAl-LDH nanoadjuvants enables it to capture antigens in situ and induce personalized immune responses, thereby more effectively overcoming complex diseases. In this review, we comprehensively summarize the development and application of MgAl-LDH nanoparticles as a vaccine adjuvant, demonstrating that MgAl-LDH is the most potential adjuvant for clinical application.

Nanocomposite-based dual enzyme system for broad-spectrum scavenging of reactive oxygen species

A broad-spectrum reactive oxygen species (ROS)-scavenging hybrid material (CASCADE) was developed by sequential adsorption of heparin (HEP) and poly(L-lysine) (PLL) polyelectrolytes together with superoxide dismutase (SOD) and horseradish peroxidase (HRP) antioxidant enzymes on layered double hydroxide (LDH) nanoclay support. The synthetic conditions were optimized so that CASCADE possessed remarkable structural (no enzyme leakage) and colloidal (excellent resistance against salt-induced aggregation) stability. The obtained composite was active in decomposition of both superoxide radical anions and hydrogen peroxide in biochemical assays revealing that the strong electrostatic interaction with the functionalized support led to high enzyme loadings, nevertheless, it did not interfere with the native enzyme conformation. In vitro tests demonstrated that ROS generated in human cervical adenocarcinoma cells were successfully consumed by the hybrid material. The cellular uptake was not accompanied with any toxicity effects, which makes the developed CASCADE a promising candidate for treatment of oxidative stress-related diseases.

Enhancing Tumor Accumulation and Cellular Uptake of Layered Double Hydroxide Nanoparticles by Coating/Detaching pH-Triggered Charge-Convertible Polymers

Layered double hydroxide (LDH) nanoparticles are extensively explored as multifunctional nanocarriers due to their versatility in both the host layer and the interlayer anion. In this study, we report modification of positively charged Cu-containing LDH nanoparticles with a pH-responsive charge-changeable polymer to improve the particle colloidal stability in blood circulation, reduce the nonspecific uptake by normal cells in organs, and subsequently facilitate tumor accumulation and uptake by tumor cells in the acidic tumor microenvironment. In vitro experimental results demonstrate that this promising charge-convertible polymer-LDH nanocarrier well reduces the capture by macrophages in the physiologic medium (pH 7.4) but facilitates the uptake by tumor cells due to detaching of the coated polymer layer in the weakly acidic condition (pH 6.8). Cu-containing LDH nanoparticles also show pH-responsive magnetic resonance imaging (MRI) contrast capacity (i.e., r ₁ relaxivity). In vivo MRI further confirms effective tumor accumulation of the charge-convertible nanohybrids, with ∼4.8% of the injected dose accumulated at 24 h postintravenous injection, proving the potential as a versatile delivery nanocarrier to enhance the antitumor treatment.

Layered double hydroxide-based antioxidant dispersions with high colloidal and functional stability

Highly stable antioxidant dispersions were designed on the basis of ring-opened ellagic acid (EA) intercalated into MgAl-layered double hydroxide (LDH) nanoparticles. The morphology of the composite was delicately modified with ethanolic washing to obtain EtOH-EA-LDH with a high specific surface area. The colloidal stability was optimized by surface functionalization with positively charged polyelectrolytes. Polyethyleneimine (PEI), protamine sulfate (PS) and poly(acrylamide-co-diallyl dimethyl ammonium chloride) (PAAm-co-DADMAC) was adsorbed onto the surface of the oppositely charged EtOH-EA-LDH leading to charge neutralization and overcharging at appropriate doses. Formation of adsorbed polyelectrolyte layers provided remarkable colloidal stability for the EtOH-EA-LDH. Modification with PEI and PAAm-co-DADMAC outstandingly improved the resistance of the particles against salt-induced aggregation with a critical coagulation concentration value above 1 M, while only limited stability was achieved by covering the nanoparticles with PS. The high antioxidant activity of EtOH-EA-LDH was greatly preserved upon polyelectrolyte coating, which was proved in the scavenging of radicals in the test reaction applied. Hence, an active antioxidant nanocomposite of high drug dose and remarkable colloidal stability was obtained to combat oxidative stress in systems of high electrolyte concentrations.

Unique Enzyme Activity of Peroxidase on a Clay Nanosheet

The adsorption behavior and enzyme activity of horseradish peroxidase (HRP) was examined on a synthetic clay nanosheet, whose surface is flat at the atomic level and is negatively charged. The results showed that HRP is adsorbed effectively (adsorption equilibrium constant, K = 1.61 × 10⁷ L mol^-1) and that the structure of HRP was altered on the clay surface. The enzyme activity of HRP on the clay surface was evaluated by using H₂O₂ and tert-BuOOH as a substrate. As a result, HRP on the clay surface was able to work for tert-BuOOH, while HRP in solution did not show any activity. In addition, HRP on SSA showed reactivity even under the high-temperature conditions. These results indicate that the clay nanosheet can be a unique modifier for enzyme activity of HRP.

Exploring the bactericidal performance and application of novel mimic enzyme Co4S3

Novel and uniform Co₄S₃ nanoparticles were synthesized through a two-step hydrothermal process and testified to possess intrinsic peroxidase (POx)-like activity for the first time. As a fresh POx mimic, we studied its catalytic properties, kinetic, and mechanism to catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine in the presence of H₂O₂. According to the experiments, the bactericidal mechanism is the same as that of simulated enzyme. Based on the ability of Co₄S₃ inducing H₂O₂ to express O₂^-, the bactericidal rate can be as high as 100%. Besides, using the POx-like activity of Co₄S₃, a new off-on sensor for H₂O₂ and l-cysteine (l-Cys) detection is constructed. The sensor reveals a good wide linear response to H₂O₂ in the 40-2000 µM with a detection limit of 18 µM, while l-Cys in the 20-100 mM with a detection limit of 10 mM. The proposed method also shows great stability, high selectivity, and excellent practicability.

Antioxidant Materials Based on 2D Nanostructures: A Review on Recent Progresses

Counteracting reactive oxygen species (ROS, e.g., superoxide radical ion, H2O2 and hydroxyl radical) is an important task in fighting against oxidative stress-related illnesses and in improving product quality in industrial manufacturing processes. This review focuses on the recent advances on two-dimensional (2D) nanomaterials of antioxidant activity, which are designed for effective decomposition of ROS and thus, for reduction of oxidative stress. Some materials featured in this paper are of uni- or multi-lamellar structures modified with small molecular or enzymatic antioxidants. Others are enzyme-mimicking synthetic compounds (the so-called nanozymes) prepared without antioxidant additives. However, carbon-based materials will not be included, as they were extensively reviewed in the recent past from similar aspects. Given the landmark development around the 2D materials used in various bio-applications, sheet-like antioxidant compounds are of great interest in the scientific and technological communities. Therefore, the authors hope that this review on the recent progresses will be helpful especially for researchers working on novel developments to substantially reduce oxidative stress either in biological systems or industrial liquors.

Design of stable magnetic hybrid nanoparticles of Si-entrapped HRP

Hybrid and composite nanoparticles represent an attractive material for enzyme integration due to possible synergic advantages of the structural builders in the properties of the nanobiocatalyst. In this study, we report the synthesis of a new stable hybrid nanobiocatalyst formed by biomimetic silica (Si) nanoparticles entrapping both Horseradish Peroxidase (HRP) (EC 1.11.1.7) and magnetic nanoparticles (MNPs). We have demonstrated that tailoring of the synthetic reagents and post immobilization treatments greatly impacted physical and biocatalytic properties such as an unprecedented ~280 times increase in the half-life time in thermal stability experiments. The optimized nanohybrid biocatalyst that showed superparamagnetic behaviour, was effective in the batch conversion of indole-3-acetic acid, a prodrug used in Direct Enzyme Prodrug Therapy (DEPT). Our system, that was not cytotoxic per se, showed enhanced cytotoxic activity in the presence of the prodrug towards HCT-116, a colorectal cancer cell line. The strategy developed proved to be effective in obtaining a stabilized nanobiocatalyst combining three different organic/inorganic materials with potential in DEPT and other biotechnological applications.

Modeling the clay minerals-enzyme binding by fusion fluorescent proteins and under atomic force microscope

In the present study, binding of cellulase protein to different clay minerals were tested using fluorescent-protein complex and microscopic techniques. Cellulase gene (Cel5H) was cloned into three fluorescent vectors and expressed as fusion enzymes. Binding of Cel5H-mineral particles was confirmed by confocal microscopy, and enzyme assay. Among the Cel5H-fusion enzymes, green-fusion enzyme showed higher intensity compared with other red and yellow fusion-proteins. Intensity of fusion-proteins was dependent on the pH of the medium. Confocal microscopy revealed binding of the all three fusion proteins with different clay minerals. However, montmorillonite displayed higher binding capacity than kaolinite clay. Likewise, atomic force microscopy (AFM) image profile analysis showed proteins appeared globular molecules in free-state on mica surface with an average cross sectional diameter of 110 ± 2 nm and rough surface of montmorillonite made protein appear flattened due to structural alteration. Even surface of kaolinite also exerted some strain on protein molecular conformation after binding to surface. Our results provide further evidence for 3D visualization of enzyme-soil complex and encourage furthering study of the force involved interactions. Therefore, our results indicate that binding of proteins to clay minerals was external and provides a molecular method to observe the interaction of clay minerals-enzyme complex.

Effect of Polyelectrolyte Mono- and Bilayer Formation on the Colloidal Stability of Layered Double Hydroxide Nanoparticles

Sequential adsorption of polyelectrolytes on nanoparticles is a popular method to obtain thin films after deposition. However, the effect of polyelectrolyte multilayer formation on the colloidal stability of the nanoparticles has not been studied in detail. In the present work, layered double hydroxides (LDH) were synthesized and interaction with oppositely and like-charged polyelectrolytes was investigated. Electrophoretic and light scattering measurements revealed that colloidal stability of LDH can be tuned by adsorption of poly(styrene sulfonate) (PSS) on the oppositely charged LDH surface in appropriate doses and thus, unstable or stable dispersions can be designed. Negatively charged LDH of adsorbed PSS monolayer was obtained and a poly(diallyldimethyl ammonium chloride) (PDADMAC) second layer was systematically built on the particles. The obtained polyelectrolyte bilayer provided high colloidal stability for the LDH-PSS-PDADMAC dispersions due to the presence of repulsive interparticle forces of electrostatic and steric origin. The results provide crucial quantitative information on designing highly stable particle-polyelectrolyte systems for the preparation of thin films or immobilization of guest substances between the layers for delivery processes.

High and long-term antibacterial activity against Escherichia coli via synergy between the antibiotic penicillin G and its carrier ZnAl layered double hydroxide

Antibiotic-resistant bacterial infections are a global health problem. A commonly-used antibiotic Penicillin G was incorporated into ZnAl-layered double hydroxides (PNG/LDH) with a varied amount of PNG. PNG/LDH nanocomposites were well characterized in structure and composition using elemental analysis, X-ray diffraction pattern, Fourier transform infrared spectroscopy and TEM images, revealing that PNG were mostly adsorbed on the LDH surfaces at a lower PNG loading but some were intercalated into LDH interlayers at a higher PNG loading. The typical release profile of PNG and Zn²⁺ from PNG/LDH was a quick release, followed by a sustainable slow release. The antibacterial tests against Escherichia coli demonstrated that PNG/LDH with a suitable composition synergistically improved bacterial inhibition compared with free PNG and pristine LDHs. In specific, PNG/LDH with much higher cost-effectiveness showed a potent antimicrobial activity and maintained the activity for up to 10 days, significantly elongating the antibacterial effect compared with just 1 day for free PNG in the same conditions. Our results suggest suitable composition of nanoparticle carriers and antibiotics could significantly enhance antibacterial activity of antibiotics for a long period via the synergistic effect between carrier and antibiotics, a potential approach to overcome the bacterial resistance to antibiotics.