Efficient nanobiocatalytic systems of nuclease P immobilized on PEG-NH2 modified graphene oxide: effects of interface property heterogeneity

Polydopamine-Modified 2D Iron (II) Immobilized MnPS3 Nanosheets for Multimodal Imaging-Guided Cancer Synergistic Photothermal-Chemodynamic Therapy

Manganese phosphosulphide (MnPS3 ), a newly emerged and promising member of the 2D metal phosphorus trichalcogenides (MPX3 ) family, has aroused abundant interest due to its unique physicochemical properties and applications in energy storage and conversion. However, its potential in the field of biomedicine, particularly as a nanotherapeutic platform for cancer therapy, has remained largely unexplored. Herein, a 2D "all-in-one" theranostic nanoplatform based on MnPS3 is designed and applied for imaging-guided synergistic photothermal-chemodynamic therapy. (Iron) Fe (II) ions are immobilized on the surface of MnPS3 nanosheets to facilitate effective chemodynamic therapy (CDT). Upon surface modification with polydopamine (PDA) and polyethylene glycol (PEG), the obtained Fe-MnPS3 /PDA-PEG nanosheets exhibit exceptional photothermal conversion efficiency (η = 40.7%) and proficient pH/NIR-responsive Fenton catalytic activity, enabling efficient photothermal therapy (PTT) and CDT. Importantly, such nanoplatform can also serve as an efficient theranostic agent for multimodal imaging, facilitating real-time monitoring and guidance of the therapeutic process. After fulfilling the therapeutic functions, the Fe-MnPS3 /PDA-PEG nanosheets can be efficiently excreted from the body, alleviating the concerns of long-term retention and potential toxicity. This work presents an effective, precise, and safe 2D "all-in-one" theranostic nanoplatform based on MnPS3 for high-efficiency tumor-specific theranostics.

A chemiresistive biosensor for detection of cancer biomarker in biological fluids using CVD-grown bilayer graphene

A chemiresistive biosensor is described for simple and selective detection of miRNA-21. We developed chemical vapor deposition (CVD) and low-damage plasma treatment (LDPT)-treated bilayer graphene composite of graphene oxide/graphene (GO/GR) for the determination of a reliable biomarker. We have successfully overcome the self-limiting growth mechanism by using CVD method to grow more than one layer of graphene on copper foil. In addition, LDPT can be used to form GO/GR structures for chemiresistive biosensor applications. Due to the direct formation of BLGR (bilayer graphene), the coupling between graphene layers is theoretically superior to that of stacked BLGR, which is also confirmed by the blue shift of the characteristic peak of graphene in Raman spectroscopy. The shift is about double compared with that of stacked BLGR. Based on the results, the limit of detection for the target miRNA-21 was calculated to be 5.20 fM and detection rage is calculated as 100 fM to 10 nM, which is obviously better performance. Compared with previous work, this chemiresistive biosensor has good selectivity, and stability towards detection of miRNA-21. The ability to detect miRNA-21 in different biological fluids was almost identical to that in pH 7.4 phosphate-buffered saline (PBS). Thus, the proposed bilayer GO/GR of modified chemiresistive biosensor may potentially be applied to detect cancer cells in clinical examinations.

Immobilization of Sucrose Isomerase from Erwinia sp. with Graphene Oxide and Its Application in Synthesizing Isomaltulose

Sucrose isomerase (SIase) is a key enzyme used for the production of isomaltulose from sucrose. In this study, an SIase gene from Erwinia sp. Ejp617 (ErSIase) was heterologously expressed in Escherichia coli BL21(DE3), and the recombinant ErSIase was served as biocatalyst combined with the graphene oxide (GO) as carrier for ErSIase immobilization. The Fourier transform infrared spectroscopy, transmission electron microscope, and confocal laser microscopy analyses showed that ErSIase was successfully immobilized on the surface of GO to form ErSIase-GO. The loading capacity of ErSIase on GO reached up to 460 mg/g with a specific activity of 727.04 U/mg protein when the optimal immobilization time of 12 h and the ErSIase/GO ratio of 7.4:4 (w/w) were applied. A high conversion rate of 95.3% was reached from sucrose to isomaltulose using ErSIase-GO as biocatalyst with 600 g/L sucrose as substrate, after 180 min at 40 °C and pH 6.0. Moreover, stabilities of the immobilized ErSIase-GO in the aspects of thermal, pH, and storage were improved, and its activity after 10 batches still remained around 80% under the optimal conditions. The Km value of ErSIase-GO was 29.32 mM, and the kcat/Km was increased to 27.34 s-1 mM-1 when 0.1% (w/v) detergent NP40 was added. These results indicated that the ErSIase was well immobilized onto GO, and the ErSIase-GO is a promising biocatalyst with high operational stability and catalytic activity for industrial production of isomaltulose.

Recombinant Expression of Serratia marcescens Outer Membrane Phospholipase A (A1) in Pichia pastoris and Immobilization With Graphene Oxide-Based Fe3O4 Nanoparticles for Rapeseed Oil Degumming

Enzymatic degumming is an effective approach to produce nutritional, safe, and healthy refined oil. However, the high cost and low efficiency of phospholipase limit the application of enzymatic degumming. In this study, an 879 bp outer membrane phospholipase A (A1) (OM-PLA1) gene encoding 292 amino acid residues was isolated from the genome of Serratia marcescens. The recombinant OM-PLA1 profile of appropriately 33 KDa was expressed by the engineered Pichia pastoris GS115. The OM-PLA1 activity was 21.2 U/mL with the induction of 1 mM methanol for 72 h. The expression efficiencies of OM-PLA1 were 0.29 U/mL/h and 1.06 U/mL/OD600. A complex of magnetic graphene oxide (MGO) and OM-PLA1 (MGO-OM-PLA1) was prepared by immobilizing OM-PLA1 with graphene oxide-based Fe3O4 nanoparticles by cross-linking with glutaraldehyde. The content of phosphorus decreased to 5.1 mg/kg rapeseed oil from 55.6 mg/kg rapeseed oil with 0.02% MGO-OM-PLA1 (w/w) at 50°C for 4 h. MGO-OM-PLA1 retained 51.7% of the initial activity after 13 times of continuous recycling for the enzymatic degumming of rapeseed oil. This study provided an effective approach for the enzymatic degumming of crude vegetable oil by developing a novel phospholipase and improving the degumming technology.

Immobilization of Horseradish Peroxidase on Multi-Armed Magnetic Graphene Oxide Composite: Improvement of Loading Amount and Catalytic Activity

In this study, a novel type of multi-armed polymer (poyltehylene glycol, PEG) magnetic graphene oxide (GO) composite (GO@Fe₃O₄@6arm-PEG-NH₂) has been synthesized as a support for immobilization of horseradish peroxidase (HRP) for the first time. The loading amount of HRP was relatively high (186.34 mg/g) due to the surface of carrier material containing a large amount of amino groups from 6arm-PEG-NH₂, but degradation rate of phenols was also much higher (95.4%), which is attributed to the synergistic effect between the free HRP (45.4%) and the support material of GO@Fe₃O₄@6arm-PEG-NH₂ (13.6%). Compared with the free enzyme, thermal, storage and operational stability of the immobilized HRP improved. The immobilized HRP still retained over 68.1% activity after being reused 8 times. These results suggest that the multi-armed magnetic composite has good application prospect for enzyme immobilization.

Nano-Biocatalysts of Cyt c@ZIF-8/GO Composites with High Recyclability via a de Novo Approach

To improve the stability and recyclability of enzymes immobilized on metal-organic frameworks (MOFs), graphene oxide (GO) with surface oxygen-rich functional groups was selected to form ZIF-8/GO nanocomposites with the zeolitic imidazolate framework (ZIF-8) for cytochrome c (Cyt c) immobilization. It was found that the functional groups on the GO surface were involved in the growth of ZIF-8 without affecting the crystal structure but their particle size was reduced to about 200 nm. The storage stability and resistance to organic solvents of Cyt c were obviously improved after the immobilization on the ZIF-8/GO nanocomposite. On one hand, compared with Cyt c@ZIF-8 and Cyt c@GO with 30 and 60% protein leakage, Cyt c@ZIF-8/GO displayed little protein leakage after 60 h of storage. On the other hand, Cyt c@ZIF-8/GO retained a residual activity of approximately 100% after being stored in ethanol and acetone for 2 h, whereas the free enzyme, Cyt c@ZIF-8, and Cyt c@GO retained only about 10, 50, and 40%, respectively. In addition, the Cyt c@ZIF-8/GO nanocomposites can be utilized up to four cycles with virtually no loss of activity and may be further applied on H₂O₂ biosensing systems. The synergistic effect between MOFs and GO in ZIF-8/GO nanocomposites provides infinite possibilities as immobilized enzyme carriers.

Affinity induced immobilization of adenylate cyclase from the crude cell lysate for ATP conversion

The development of an orientation immobilization technique via affinity between polyhistidine tags and metal ions aims at maintaining biocatalytic activity of the enzymes. In this work, to tackle the issue of the immobilization of adenylate cyclase (AC), a simple and effective approach of synthesizing iminodiacetic acid (IDA)-Ni²⁺ particles was applied for simultaneously purifying and immobilizing his-tagged AC. We chose agarose particles as carriers, and then decorated them with IDA, leading to the formation of a coordination combination of Ni²⁺. The porous carriers with a large pore size of 50 nm and a specific surface area of 45.8 m²/g exhibited favorable enzymatic activity and loading capacity. The optimal pH of the immobilized enzyme increased from 8.0 to 9.0 and the optimal temperature increased from 30 °C to 35 °C, compared to the free AC. Moreover, the immobilized AC retained a residual activity of approximately 80% after storing it at 25 °C for 48 h, whereas only 40% of the activity was left in the free AC at the same conditions. Maximum yield of cyclic adenosine-3', 5'- monophosphate (cAMP) reached up to the summit of the reaction. The immobilized AC by affinity adsorption will provide a promising route for the industrial production of cAMP.

Nitrogen-containing amino compounds functionalized graphene oxide: Synthesis, characterization and application for the removal of pollutants from wastewater: A review

Nowadays, using graphene oxide (GO) as an adsorbent for removing pollutants from wastewater has attracted increasing attention due to its unique physic-chemical properties. Nitrogen-containing amino (NA) compounds have excellently complexing properties due to their abundant amino functional groups. In order to obtain an innovative adsorbent, functionalized GO (NAGO) has been developed by combining the properties of GO with the advantages of NA compounds. The obtained NAGO composites usually exhibit great improvement in adsorption properties and can be used as a promising adsorbent for decontamination of wastewater. This paper reviewed recent progress of synthetic technologies about fabricating various NAGOs, and their morphologies, structures and functional characteristics. Meanwhile, important applications of NAGOs for different kind of pollutants and theory of the adsorption phenomena are discussed based on the isothermal and kinetic adsorption models. Furthermore, the affecting factors, underlying mechanisms and comparison with other adsorbents for the removal of pollutants are reviewed. Conclusively, the perspectives and challenges involved in the application of NAGOs for decontamination of wastewater have also been proposed to promote sustainable development of this new exciting field.

Controlling enzyme function through immobilisation on graphene, graphene derivatives and other two dimensional nanomaterials

Controlling enzyme function through immobilisation on graphene, graphene derivatives and other two dimensional nanomaterials.

Advances in biotechnological synthetic applications of carbon nanostructured systems

In the last few years carbon nanostructures have been applied for the immobilization of enzymes and biomimetic organo-metallic species useful for biotechnological applications. The nature of the support and the method of immobilization are responsible for the stability, reactivity and selectivity of the system. In this review, we focus on the recent advances in the use of carbon nanostructures, carbon nanotubes, carbon nanorods, fullerene and graphene for the preparation of biocatalytic and biomimetic systems and for their application in the development of green chemical processes.