Graphene oxide as a matrix for enzyme immobilization

Advances in photoactivated carbon-based nanostructured materials for targeted cancer therapy

In this review, we explore key innovations in photoactivated therapeutic programming of carbon-based nanomaterials (CBNs), focusing on their diverse nanostructural configurations and their exceptional photothermal, photochemical, and photoacoustic properties. These attributes position CBNs as remarkable phototherapeutic agents, capable of addressing critical challenges in targeted cancer therapy through their precision, multifunctionality, and adaptability to specific therapeutic modalities. We will explore their diverse derivatives, and the role of chemical augmentation and site-specific surface functionalisation, which are pivotal in optimising the targeting and efficacy of phototherapeutic interventions. The biological and physical relevance of this ever-growing library of nanomaterials in targeted phototherapy will be thoroughly explored. Dynamic photo-triggering of the underlying molecular mechanisms of action e.g., energy conversion modalities lie at the heart of these therapeutic innovations. We will further discuss the tunability and programming of these carriers and structure-function alterations at specific therapeutic wavelengths. The application space of phototherapies is thoroughly mapped exploring the three primary approaches of photothermal therapy, photodynamic therapy and photochemical internalisation as well as emerging techniques and promising multimodal approaches that combine two or more of these processes. The specificity of the target tissue site and the approach under study forms another critical focus area of this review, with an emphasis on three types of cancer-breast cancer, lung cancer, and gliomas-that have demonstrated some of the most promising outcomes from photomedicine. We also provide a perspective on in vitro and in vivo validation and preclinical testing of CBNs for phototherapeutic applications. Finally, we reflect on the potential of CBNs to revolutionise targeted cancer therapy through data-driven materials design and integration with computational tools for biophysical performance optimisation. The exciting integration of machine learning into nanoparticle research and phototherapy has potential to fundamentally transform the landscape of nanomedicine. These techniques ranging from supervised learning algorithms such as random forests and support vector machines to more advanced neural networks and deep learning, can enable unprecedented precision in predicting, optimising, and tailoring the properties of nanoparticles for targeted applications. The transformative impact of photoactivated CBNs in advancing cancer treatment, paves the way for their clinical application and widespread adoption in personalised photomedicine. We conclude with a section on the current challenges facing the reproducibility, manufacturing throughput, and biocompatibility of these nanostructured materials including their long-term effects in trials and degradation profiles in biological systems as evaluated in vitro and in vivo.

Enzymatic synthesis of antioxidant peptides with controllable and adjustable molecular weights using magnetically recyclable immobilized Alcalase

Enzymatic hydrolysis of proteins to obtain bioactive peptides is increasingly attractive, but the poor stability and low reusability of enzymes remain unsolved. Here, the magnetically recyclable immobilized Alcalase (Alcalase@SGO-PEGA) was constructed by immobilizing the free protease of Alcalase to the superparamagnetic graphene oxide (SGO) whose surface was modified with polyethylene glycol diamine (PEGA). The results indicate that Alcalase@SGO-PEGA significantly improved the thermostability and pH tolerance of Alcalase, withstanding temperatures up to 70 °C and pH levels up to 12. Additionally, Alcalase@SGO-PEGA with a saturation magnetizations (Ms) of 20.64 emu/g allowed for efficient recovery using external magnetic fields, and its catalytic stability was demonstrated by retaining 50 % of its initial activity after seven cycles of reuse. Using Alcalase@SGO-PEGA for the enzymatic hydrolysis of soy protein isolate, casein, bovine, serum protein, β-lactoglobulin, sesame protein and flaxseed, bioactive peptides with different molecular weights were obtained by adjusting the hydrolysis temperature and time. Additionally, the antioxidative capacity of the bioactive peptides was confirmed by their ABTS+ free radicals scavenging rate and Fe2+ chelating activity. This paper presents a novel, sustainable strategy for obtaining antioxidant peptides with adjustable molecular weights using magnetically recyclable immobilized Alcalase, advancing its application and promoting cleaner protein processing.

Research Progress on the Enhancement of Immobilized Enzyme Catalytic Performance and Its Application in the Synthesis of Vitamin E Succinate

Vitamin E succinate is a more mature vitamin E derivative, and its chemical stability and many effects have been improved compared with vitamin E, which can not only make up for the shortcomings of vitamin E application but also broaden the application field of vitamin E. At present, in developed countries such as Europe, America, and Japan, vitamin E succinate is widely used in health foods, and due to its good water solubility and stability, the vitamin E added to most nutritional supplements (tablets and hard capsules) is vitamin E succinate. At the same time, vitamin E succinate used in the food and pharmaceutical industries is mainly catalyzed by enzymatic catalysis. In this paper, Candida rugosa lipase (CRL) was studied. Chemical modification and immobilization were used to improve the enzymatic properties of CRL, and immobilized lipase with high stability and high activity was obtained. It was applied to the enzymatic synthesis of vitamin E succinate, and the reaction conditions were optimized to improve the yield and reduce the production cost. The review covered the research progress of the methods for enhancing the catalytic performance of immobilized enzymes and discussed its application in the synthesis of vitamin E succinate, providing new ideas and technical support for the catalytic performance enhancement of immobilized enzymes and its application in the synthesis of vitamin E succinate and promoting the production and application of vitamin E succinate.

Graphene-based materials and electrochemical biosensors: an overview

Graphene, an exceptional two-dimensional material, has attracted significant attention from the scientific community. Its unique physiochemical properties make it a suitable candidate for many applications in the field of biotechnology and medical sciences. High specific surface area, exceptionally high electrical conductivity, and good biocompatibility of graphene give it a large scope in disease diagnosis and biosensing applications. This review aims at presenting the advances in the journey of graphene-based materials and their successful implication as electrochemical nanobiosensors. The first part of the review summarizes the history, structure, and recent developments in the large-scale production of graphene. It further includes the sensing mechanism, the recent trends in biosensing, and improvements in graphene-based biosensors. The comparative analysis shows graphene-based electrochemical biosensors to have high sensitivity, long-term stability, and low detection limits compared to the various other biosensors.

Effects of copper/graphene oxide core-shell nanoparticles on Rhipicephalus ticks and their detoxification enzymes

Nanopesticides have been recently introduced as novel pesticides to overcome the drawbacks of using traditional synthetic pesticides. The present study evaluated the acaricidal activity of Copper/Graphene oxide core-shell nanoparticles against two tick species, Rhipicephalus rutilus and Rhipicephalus turanicus. The Copper/Graphene oxide core-shell nanoparticles were synthetized through the solution plasma (SP) method under different conditions. The nanoparticles synthesized at 180 W and 45 min were highly toxic to Rh. rutilus and Rh. turanicus, with 50% lethal concentration (LC50) values of 248.1 and 195.7 mg ml-1, respectively, followed by those which were synthesized at 120 W/30 mins (LC50 = 581.5 and 526.5 mg ml-1), 120 W/15 mins (LC50 = 606.9 and 686.7 mg ml-1), and 100/45 mins (LC50 = 792.9 and 710.7 mg ml-1), after 24 h of application. The enzyme assays revealed that 180 W/45 min treatment significantly inhibited the activity of acetylcholinesterase (115 ± 0.81 and 123 ± 0.33 U/ mg protein/min) and superoxide dismutase (290 ± 0.18 and 310 ± 0.92 U/ mg protein/min) in Rh. rutilus and Rh. turanicus, respectively, as compared with the negative control. The results also revealed a significantly increased catalase activity (895 ± 0.37 and 870 ± 0.31 U/ mg protein/min) in Rh. rutilus and Rh. turanicus, respectively. The above results indicated that Copper/Graphene oxide core-shell nanoparticles could be a promising alternatives for the management of ticks.

Innovative approaches in invertase immobilization: Utilizing green synthesized zinc oxide nanoparticles to improve biochemical properties

Invertase enzyme can effectively improve the taste, color, and durability of these products. Various methods have been proposed to increase the stability and efficiency of enzymes. One of the most important is enzyme immobilization, which can be implemented on different materials. The purpose of this study was to immobilize the invertase enzyme on the surface of green synthesized zinc oxide nanoparticles and to investigate its biochemical properties. The enzyme immobilization was confirmed by SEM and Raman spectroscopy. Then, the biochemical characteristics, such as optimal pH and temperature, thermal stability, and storage stability of free and immobilized enzymes, were determined. The results of SEM showed that the diameter of synthesized nanoparticles was about 60 ± 5 nm. FTIR of immobilized invertase confirmed the immobilization process. The immobilization efficiency was determined to be 72 %. Immobilized enzyme showed higher thermal stability at 40 and 50 °C. Immobilized enzyme could be used 8 times in optimum condition. Also, an Examination of the kinetic parameters of the immobilized enzyme compared with those of the free enzyme showed a decrease in the maximum velocity of the enzyme. It seems that the immobilized invertase has improved characteristics for application in different industries.

Natural Affinity Driven Modification by Silicene to Construct a "Thermal Switch" for Tumorous Bone Loss

Tumorous bone defects present significant challenges for surgical bio-reconstruction due to the dual pathological conditions of residual tumor presence and extensive bone loss following excision surgery. To address this challenge, a "thermal switch" smart bone scaffold based on the silicene nanosheet-modified decalcified bone matrix (SNS@DBM) is developed by leveraging the natural affinity between collagen and silicene, which is elucidated by molecular dynamics simulations. Benefitting from its exceptional photothermal ability, biodegradability, and bioactivity, the SNS@DBM "thermal switch" provides an integrated postoperative sequential thermotherapy for tumorous bone loss by exerting three levels of photothermal stimulation (i.e., strong, moderate, and nonstimulation). During the different phases of postoperative bioconstruction, the SNS@DBM scaffold realizes simultaneous residual tumor ablation, tumor recurrence prevention, and bone tissue regeneration. These biological effects are verified in the tumor-bearing nude mice of patient-derived tissue xenografts and critical cranium defect rats. Mechanism research prompts moderate heat stimulus generated by and coordinating with SNSs can upregulate osteogenic genes, promote macrophages M2 polarization, and intensify angiogenesis of H-type vessels. This study introduces a versatile approach to the management of tumorous bone defects.

A graphene oxide-assisted protein immobilization paper-tip immunosensor with smartphone and naked eye readout for the detection of okadaic acid

BACKGROUND

Okadaic acid (OA), as a diarrhetic shellfish poisoning, can increase the risk of acute carcinogenic or teratogenic effects for the ingestion of OA contaminated shellfish. At present, much effort has been made to graft immunoassay onto a paper substrate to make paper-based sensors for rapid and simple detection of shellfish toxin. However, the complicated washing steps and low protein fixation efficiency on the paper substrate need to be further addressed.

RESULTS

A novel paper-tip immunosensor for detecting OA was developed combined with smartphone and naked eye readout. The trapezoid paper tip was consisted of quantitative and qualitative detection zones. To improve the OA antigen immobilization efficiency on the paper substrate, graphene oxide (GO)-assisted protein immobilization method was introduced. Meanwhile, Au nanoparticles composite probe combined with the lateral flow washing was developed to simplify the washing step. The OA antigen-immobilized zone, as the detection zone Ⅰ, was used for quantitative assay by smartphone imaging. The paper-tip front, as the detection zone Ⅱ, which could qualitatively differentiate OA pollution level within 45 min using the naked eye. The competitive immunoassay on the paper tip exhibited a wide linear range for detecting OA (0.02-50 ng∙mL-1) with low detection limit of 0.02 ng∙mL-1. The recovery of OA in spiked shellfish samples was in the range of 90.3 %-113.%.

SIGNIFICANCE

These results demonstrated that the proposed paper-tip immunosensor could provide a simple, low-cost and high-sensitivity test for OA detection without the need for additional large-scale equipment or expertise. We anticipate that this paper-tip immunosensor will be a flexible and versatile tool for on-site detecting the pollution of marine products.

Transferrin Immobilized Graphene Oxide Nanocomposite for Targeted Cancer Chemodynamic Therapy via Increasing Intracellular Labile Fe2+ Concentration

Recently, different alternative regulated cell death (RCD) pathways, viz., necroptosis, pyroptosis, ferroptosis, cuproptosis etc., have been explored as important targets for the development of cancer medications in recent years, as these can change the immunogenicity of the tumor microenvironment (TME) and will finally lead to the inhibition of cancer progression and metastasis. Here, we report the development of transferrin immobilized graphene oxide (Tfn@GOAPTES) nanocomposite as a therapeutic strategy toward cancer cell killing. The electrostatic immobilization of Tfn on the GOAPTES surface was confirmed by different spectroscopy and microscopy techniques. The Tfn immobilization was found to be ∼74 ± 4%, whereas the stability of the protein on the GO surface suggested a robust nature of the nanocomposite. The MTT assay suggested that Tfn@GOAPTES exhibited cytotoxicity toward HeLa cells via increased lipid peroxidation and DNA damage. Western blot studies resulted in decreased expression of acetylation on lysine 40 of α-tubulin and increased expression of LC3a/b for Tfn@GOAPTES treated HeLa cells, suggesting autophagy to be the main cause of the cell death mechanism. Overall, we predict that the present approach can be used as a therapeutic strategy for cancer cell killing via selective induction of a high concentration of intracellular iron.

Progress and mechanism of graphene oxide-composited materials in application of peripheral nerve repair

Peripheral nerve injuries (PNI) are one of the most common nerve injuries, and graphene oxide (GO) has demonstrated significant potential in the treatment of PNI. GO could enhance the proliferation, adhesion, migration, and differentiation of neuronal cells by upregulating the expression of relevant proteins, and regulate the angiogenesis process and immune response. Therefore, GO is a suitable additional component for fabricating artificial nerve scaffolds (ANS), in which the slight addition of GO could improve the physicochemical performance of the matrix materials, through hydrogen bonds and electrostatic attraction. GO-composited ANS can increase the expression of nerve regeneration-associated genes and factors, promoting angiogenesis by activating the RAS/MAPK and AKT-eNOS-VEGF signaling pathway, respectively. Moreover, GO could be metabolized and excreted from the body through the pathway of peroxidase degradation in vivo. Consequently, the application of GO in PNI regeneration exhibits significant potential for transitioning from laboratory research to clinical use.

Bio-Inspired Microreactors Continuously Synthesize Glucose Precursor from CO2 with an Energy Conversion Efficiency 3.3 Times of Rice

Excessive CO2 and food shortage are two grand challenges of human society. Directly converting CO2 into food materials can simultaneously alleviate both, like what green crops do in nature. Nevertheless, natural photosynthesis has a limited energy efficiency due to low activity and specificity of key enzyme D-ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). To enhance the efficiency, many prior studies focused on engineering the enzymes, but this study chooses to learn from the nature to design more efficient reactors. This work is original in mimicking the stacked structure of thylakoids in chloroplasts to immobilize RuBisCO in a microreactor using the layer-by-layer strategy, obtaining the continuous conversion of CO2 into glucose precursor at 1.9 nmol min-1 with enhanced activity (1.5 times), stability (≈8 times), and reusability (96% after 10 reuses) relative to the free RuBisCO. The microreactors are further scaled out from one to six in parallel and achieve the production at 15.8 nmol min-1 with an energy conversion efficiency of 3.3 times of rice, showing better performance of this artificial synthesis than NPS in terms of energy conversion efficiency. The exploration of the potential of mass production would benefit both food supply and carbon neutralization.

Glutamate oxidase sheets-Prussian blue grafted amperometric biosensor for the real time monitoring of glutamate release from primary cortical neurons

Glutamate (GLU) is a primary excitatory neurotransmitter, and its dysregulation is associated with several neurodegenerative disorders. A major challenge in GLU estimation is the existence of other biomolecules in the brain that could directly get oxidized at the electrode. Hence, highly selective electroenzymatic biosensors that enable rapid estimation of GLU are needed. Initially, a copolymer, poly(2-dimethylaminoethyl methacrylate- styrene) was synthesized through reversible addition-fragmentation chain transfer polymerization to noncovalently functionalize reduced graphene oxide (rGO), named DS-rGO. Glutamate oxidase macromolecule immobilized DS-rGO formed enzyme nanosheets, which was drop-coated over Prussian blue electrodeposited disposable electrodes to fabricate the GLU biosensor. The interconnectivity between the enzyme nanosheets and the Prussian blue endows the biosensor with enhanced conductivity and electrochemical activity. The biosensor exhibited a linearity: 3.25-250 μM; sensitivity: 3.96 μA mM-1 cm-2, and a limit of detection: 0.96 μM for GLU in the Neurobasal Medium. The biosensor was applied to an in vitro primary rat cortical model to discriminate GLU levels in Neurobasal Medium, before and after KCl mediated depolarization, which provides new insights for elucidating neuronal functioning in the brain.

Improvement of thermal-stability of chondroitinase ABCI immobilized on graphene oxide for the repair of spinal cord injury

Spinal cord injury healing has been shown to be aided by chondroitinase ABC I (cABCI) treatment. The transport of cABCI to target tissues is complicated by the enzyme's thermal instability; however, cABCI may be immobilized on nanosheets to boost stability and improve delivery efficiency. This investigation's goal was to assess the immobilization of cABC I on graphene oxide (GO). for this purpose, GO was produced from graphene using a modified version of Hummer's process. the immobilization of cABC I on GO was examined using SEM, XRD, and FTIR. The enzymatic activity of cABC I was evaluated in relation to substrate concentration. The enzyme was then surface-adsorption immobilized on GO, and its thermal stability was examined. As compared to the free enzyme, the results showed that the immobilized enzyme had a greater Km and a lower Vmax value. The stability of the enzyme was greatly improved by immobilization at 20, 4, 25, and 37 °C. For example, at 37 °C, the free enzyme retained 5% of its activity after 100 min, while the immobilized one retained 30% of its initial activity. The results showed, As a suitable surface for immobilizing cABC I, GO nano sheets boost the enzyme's stability, improving its capability to support axonal regeneration after CNC damage and guard against fast degradation.

Environmental biotechnology and the involving biological process using graphene-based biocompatible material

Biotechnology is a promising approach to environmental remediation but requires improvement in efficiency and convenience. The improvement of biotechnology has been illustrated with the help of biocompatible materials as biocarrier for environmental remediations. Recently, graphene-based materials (GBMs) have become promising materials in environmental biotechnology. To better illustrate the principle and mechanisms of GBM application in biotechnology, the comprehension of the biological response of microorganisms and enzymes when facing the GBMs is needed. The review illustrated distinct GBM-microbe/enzyme composites by providing the GBM-microbe/enzyme interaction and the determining factors. There are diverse GBM modifications for distinct biotechnology applications. Each of these methods and applications depends on the physicochemical properties of GBMs. The applications of these composites were mainly categorized as pollutant adsorption, anaerobic digestion, microbial fuel cells, and organics degradation. Where information was available, the strategies and mechanisms of GBMs in improving application efficacies were also demonstrated. In addition, the biological response, from microbial community changes, extracellular polymeric substances changes to biological pathway alteration, may become important in the application of these composites. Furthermore, we also discuss challenges facing the environmental application of GBMs, considering their fate and toxicity in the ecosystem, and offer potential solutions. This research significantly enhances our comprehension of the fundamental principles, underlying mechanisms, and biological pathways for the in-situ utilization of GBMs.

Nanobio Interface Between Proteins and 2D Nanomaterials

Two-dimensional (2D) nanomaterials have significantly contributed to recent advances in material sciences and nanotechnology, owing to their layered structure. Despite their potential as multifunctional theranostic agents, the biomedical translation of these materials is limited due to a lack of knowledge and control over their interaction with complex biological systems. In a biological microenvironment, the high surface energy of nanomaterials leads to diverse interactions with biological moieties such as proteins, which play a crucial role in unique physiological processes. These interactions can alter the size, surface charge, shape, and interfacial composition of the nanomaterial, ultimately affecting its biological activity and identity. This review critically discusses the possible interactions between proteins and 2D nanomaterials, along with a wide spectrum of analytical techniques that can be used to study and characterize such interplay. A better understanding of these interactions would help circumvent potential risks and provide guidance toward the safer design of 2D nanomaterials as a platform technology for various biomedical applications.

An Up-to-Date Review on the Remediation of Dyes and Phenolic Compounds from Wastewaters Using Enzymes Immobilized on Emerging and Nanostructured Materials: Promises and Challenges

Addressing the critical issue of water pollution, this review article emphasizes the need to remove hazardous dyes and phenolic compounds from wastewater. These pollutants pose severe risks due to their toxic, mutagenic, and carcinogenic properties. The study explores various techniques for the remediation of organic contaminants from wastewater, including an enzymatic approach. A significant challenge in enzymatic wastewater treatment is the loss of enzyme activity and difficulty in recovery post-treatment. To mitigate these issues, this review examines the strategy of immobilizing enzymes on newly developed nanostructured materials like graphene, carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). These materials offer high surface areas, excellent porosity, and ample anchoring sites for effective enzyme immobilization. The review evaluates recent research on enzyme immobilization on these supports and their applications in biocatalytic nanoparticles. It also analyzes the impact of operational factors (e.g., time, pH, and temperature) on dye and phenolic compound removal from wastewater using these enzymes. Despite promising outcomes, this review acknowledges the challenges for large-scale implementation and offers recommendations for future research to tackle these obstacles. This review concludes by suggesting that enzyme immobilization on these emerging materials could present a sustainable, environmentally friendly solution to the escalating water pollution crisis.

Graphene Oxide Hosting a pH-Sensitive Prodrug: An In Silico Investigation of Graphene Oxide-Based Nanovehicle toward Cancer Therapy

Prodrug and drug delivery systems are two effective strategies for improving the selectivity of chemotherapeutics. Herein, via molecular dynamics (MD) simulation and free energy calculation, the effectiveness of the graphene oxide (GO) decorated with the pH-sensitive prodrug (PD) molecules in cancer therapy is investigated. PEI-CA-DOX (prodrug) was loaded onto the GO surface, in which the hydrogen bonding and pi-pi stacking interactions play the main role in the stability of the GO-PD complex. Due to the strong interaction of GO and PD (about -800 kJ/mol), the GO-PD complex remains stable during the membrane penetration process. The obtained results confirm that GO is a suitable surface for hosting the prodrug and passing it through the membrane. Furthermore, the investigation of the release process shows that the PD can be released under acidic conditions. This phenomenon is due to the reduction of the contribution of electrostatic energy in the GO and PD interaction and the entry of water into the drug delivery system. Moreover, it is found that an external electrical field does not have much effect on drug release. Our results provide a deep understanding of the prodrug delivery systems, which helps the combination of nanocarriers and modified chemotherapy drugs in the future.

Developing Enzyme Immobilization with Fibrous Membranes: Longevity and Characterization Considerations

Fibrous membranes offer broad opportunities to deploy immobilized enzymes in new reactor and application designs, including multiphase continuous flow-through reactions. Enzyme immobilization is a technology strategy that simplifies the separation of otherwise soluble catalytic proteins from liquid reaction media and imparts stabilization and performance enhancement. Flexible immobilization matrices made from fibers have versatile physical attributes, such as high surface area, light weight, and controllable porosity, which give them membrane-like characteristics, while simultaneously providing good mechanical properties for creating functional filters, sensors, scaffolds, and other interface-active biocatalytic materials. This review examines immobilization strategies for enzymes on fibrous membrane-like polymeric supports involving all three fundamental mechanisms of post-immobilization, incorporation, and coating. Post-immobilization offers an infinite selection of matrix materials, but may encounter loading and durability issues, while incorporation offers longevity but has more limited material options and may present mass transfer obstacles. Coating techniques on fibrous materials at different geometric scales are a growing trend in making membranes that integrate biocatalytic functionality with versatile physical supports. Biocatalytic performance parameters and characterization techniques for immobilized enzymes are described, including several emerging techniques of special relevance for fibrous immobilized enzymes. Diverse application examples from the literature, focusing on fibrous matrices, are summarized, and biocatalyst longevity is emphasized as a critical performance parameter that needs increased attention to advance concepts from lab scale to broader utilization. This consolidation of fabrication, performance measurement, and characterization techniques, with guiding examples highlighted, is intended to inspire future innovations in enzyme immobilization with fibrous membranes and expand their uses in novel reactors and processes.

Nanostructured supports for multienzyme co-immobilization for biotechnological applications: Achievements, challenges and prospects

The synergistic combination of current biotechnological and nanotechnological research has turned to multienzyme co-immobilization as a promising concept to design biocatalysis engineering. It has also intensified the development and deployment of multipurpose biocatalysts, for instance, multienzyme co-immobilized constructs, via biocatalysis/protein engineering to scale-up and fulfil the ever-increasing industrial demands. Considering the characteristic features of both the loaded multienzymes and nanostructure carriers, i.e., selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness, multienzyme-based green biocatalysts have become a powerful norm in biocatalysis/protein engineering sectors. In this context, the current state-of-the-art in enzyme engineering with a synergistic combination of nanotechnology, at large, and nanomaterials, in particular, are significantly contributing and providing robust tools to engineer and/or tailor enzymes to fulfil the growing catalytic and contemporary industrial needs. Considering the above critics and unique structural, physicochemical, and functional attributes, herein, we spotlight important aspects spanning across prospective nano-carriers for multienzyme co-immobilization. Further, this work comprehensively discuss the current advances in deploying multienzyme-based cascade reactions in numerous sectors, including environmental remediation and protection, drug delivery systems (DDS), biofuel cells development and energy production, bio-electroanalytical devices (biosensors), therapeutical, nutraceutical, cosmeceutical, and pharmaceutical oriented applications. In conclusion, the continuous developments in nano-assembling the multienzyme loaded co-immobilized nanostructure carriers would be a unique way that could act as a core of modern biotechnological research.

Recent Prospects of Carbonaceous Nanomaterials-Based Laccase Biosensor for Electrochemical Detection of Phenolic Compounds

Phenolic compounds (PhCs) are ubiquitously distributed phytochemicals found in many plants, body fluids, food items, medicines, pesticides, dyes, etc. Many PhCs are priority pollutants that are highly toxic, teratogenic, and carcinogenic. Some of these are present in body fluids and affect metabolism, while others possess numerous bioactive properties such as retaining antioxidant and antimicrobial activity in plants and food products. Therefore, there is an urgency for developing an effective, rapid, sensitive, and reliable tool for the analysis of these PhCs to address their environmental and health concern. In this context, carbonaceous nanomaterials have emerged as a promising material for the fabrication of electrochemical biosensors as they provide remarkable characteristics such as lightweight, high surface: volume, excellent conductivity, extraordinary tensile strength, and biocompatibility. This review outlines the current status of the applications of carbonaceous nanomaterials (CNTs, graphene, etc.) based enzymatic electrochemical biosensors for the detection of PhCs. Efforts have also been made to discuss the mechanism of action of the laccase enzyme for the detection of PhCs. The limitations, advanced emerging carbon-based material, current state of artificial intelligence in PhCs detection, and future scopes have also been summarized.

A comprehensive review on bio-mimicked multimolecular frameworks and supramolecules as scaffolds for enzyme immobilization

Immobilization depicts a propitious route to optimize the catalytic performances, efficient recovery, minimizing autocatalysis, and also augment the stabilities of enzymes, particularly in unnatural environments. In this opinion, supramolecules and multimolecular frameworks have captivated immense attention to achieve profound controllable interactions between enzyme molecules and well-defined natural or synthetic architectures to yield protein bioconjugates with high accessibility for substrate binding and enhanced enantioselectivities. This scholastic review emphasizes the possibilities of associating multimolecular complexes with biological entities via several types of interactions, namely covalent interactions, host-guest complexation, π - π ${\rm{\pi }}-{\rm{\pi }}$ interactions, intra/inter hydrogen bondings, electrostatic interactions, and so forth offers remarkable applications for the modulations of enzymes. The potential synergies between artificial supramolecular structures and biological systems are the primary concern of this pedagogical review. The majority of the research primarily focused on the dynamic biomolecule-responsive supramolecular assemblages and multimolecular architectures as ideal platforms for the recognition and modulation of proteins and cells. Embracing sustainable green demeanors of enzyme immobilizations in a quest to reinforce site-selectivity, catalytic efficiency, and structural integrality of enzymes are the contemporary requirements of the biotechnological sectors that instigate the development of novel biocatalytic systems.

Nanomaterials and Their Impact on the Immune System

Nanomaterials have been the focus of intensive development and research in the medical and industrial sectors over the past several decades. Some studies have found that these compounds can have a detrimental impact on living organisms, including their cellular components. Despite the obvious advantages of using nanomaterials in a wide range of applications, there is sometimes skepticism caused by the lack of substantial proof that evaluates potential toxicities. The interactions of nanoparticles (NPs) with cells of the immune system and their biomolecule pathways are an area of interest for researchers. It is possible to modify NPs so that they are not recognized by the immune system or so that they suppress or stimulate the immune system in a targeted manner. In this review, we look at the literature on nanomaterials for immunostimulation and immunosuppression and their impact on how changing the physicochemical features of the particles could alter their interactions with immune cells for the better or for the worse (immunotoxicity). We also look into whether the NPs have a unique or unexpected (but desired) effect on the immune system, and whether the surface grafting of polymers or surface coatings makes stealth nanomaterials that the immune system cannot find and get rid of.

Development of Nanoscale Graphene Oxide Models for the Adsorption of Biological Molecules

Graphene oxide (GO), a nanomaterial with promising applications that range from water purification to enzyme immobilization, is actively present in scientific research since its discovery. GO studies with computational methodologies such as molecular dynamics are frequently reported in the literature; however, the models used often rely on approximations, such as randomly placing functional groups and the use of generalized force fields. Therefore, it is important to develop new MD models that provide a more accurate description of GO structures and their interaction with an aqueous solvent and other adsorbate molecules. In this paper, we derived new force field non-bonded parameters from linear-scaling density functional theory calculations of nanoscale GO sheets with more than 10,000 atoms through an atoms-in-molecules (AIM) partitioning scheme. The resulting GAFF2-AIM force field, derived from the bonded terms of GAFF2 parameterization, reproduces the solvent structure reported in ab initio MD simulations better than the force field nowadays widely used in the literature. Additionally, we analyzed the effect of the ionic strength of the medium and of the C/O ratio on the distribution of charges surrounding the GO sheets. Finally, we simulated the adsorption of natural amino acid molecules to a GO sheet and estimated their free energy of binding, which compared very favorably to their respective experimental values, validating the force field presented in this work.

An Economical and Scalable Method to Synthesize Graphitic-Like Films

An economical and facile method to synthesize a precursor for carbon films and materials has been developed. This precursor can be easily coated onto substrates without binder reagents and then converted into a graphitic-like structure after mild thermal treatment. This approach potentially allows the coating of glass surfaces of different shapes and forms, such as the inside of a glass tube, for instance. The precursor consists of tetrahedral halocarbyne units which randomly combine through single electron transfer with organometallic compounds to create a poly(carbyne)-like polymeric material. Advanced characterization tools reveal that the synthesized product (poly(halocarbyne) or PXC, where X indicate the presence of halogens, is composed mostly of carbon, hydrogen, and a variable percentage of residual halocarbon groups. Therefore, it possesses good solubility in organic solvents and can be coated on any complex substrate. The coated PXC material produced here was annealed under mild conditions, leading to the production of a graphitic-like film on a glass substrate. The chemical homogeneity of the carbon material of the film was confirmed by Raman spectroscopy.

Carbon nanomaterial functionalization with pesticide-detoxifying carboxylesterase

Four carbon materials, spent coffee-ground biochar, carbon black, short CNTs, and nitrogen-doped few-layer graphene (N-graphene) were tested for their functionalization with a commercial carboxylesterase. Their robustness to variations in time and key physicochemical parameters (temperature and pH) was analysed. In general, carbon nanomaterials showed better performance than biochar, both in terms of binding capacity and resilience in harsh conditions, at statistically significant levels. Among the tested materials, functionalized N-graphene also showed the highest level of inhibition of carboxylesterase by pesticide exposure. Therefore, N-graphene was selected for biotechnological application of pesticide scavenging toxicity in T. thermophila, a ciliate bioindicator of water quality. While immobilization of the enzyme was not effective in the case of carbaryl, a methyl carbamate, in the case of the organophosphorus dichlorvos, a 1- or 30-min contact time with a water solution containing 5 times the LC100 - 0.5 mM - allowed 50% and 100% rescue of ciliate survival, respectively. These results suggest that functionalization with carboxylesterase may be of additional benefit compared to bare carbon in water clean-up procedures, especially for highly hydrophilic pesticides such as dichlorvos.

3D Bioprinted Hydroxyapatite or Graphene Oxide Containing Nanocellulose-Based Scaffolds for Bone Regeneration

Bone tissue is usually damaged after big traumas, tumors, and increasing aging-related diseases such as osteoporosis and osteoarthritis. Current treatments are based on implanting grafts, which are shown to have several inconveniences. In this regard, tissue engineering through the 3D bioprinting technique has arisen to manufacture structures that would be a feasible therapeutic option for bone regenerative medicine. In this study, nanocellulose-alginate (NC-Alg)-based bioink is improved by adding two different inorganic components such as hydroxyapatite (HAP) and graphene oxide (GO). First, ink rheological properties and biocompatibility are evaluated as well as the influence of the sterilization process on them. Then, scaffolds are characterized. Finally, biological studies of embedded murine D1 mesenchymal stem cells engineered to secrete erythropoietin are performed. Results show that the addition of both HAP and GO prevents NC-Alg ink from viscosity lost in the sterilization process. However, GO is reduced due to short cycle autoclave sterilization, making it incompatible with this ink. In addition, HAP and GO have different influences on scaffold architecture and surface as well as in swelling capacity. Scaffolds mechanics, as well as cell viability and functionality, are promoted by both elements addition. Additionally, GO demonstrates an enhanced bone differentiation capacity.

Optimized study of the annealing effect on the electrical and structural properties of HDLC thin-films

The plasma-enhanced chemical vapor deposition (PECVD) technique has been utilized for the facile surface deposition of hydrogenated diamond-like carbon (HDLC) thin-films onto Si(100) substrates. The as-deposited film surface is homogenous, free of pinholes, and adheres to the substrate. Annealing of the synthesized HDLC surface in a vacuum was performed in the temperature range of 200 to 1000 °C. A host of instrumental techniques, viz. FTIR spectroscopy, AFM, STM, and EC-AFM, were successfully employed to detect the morphological transformation in the HDLC films upon annealing. EC-AFM studies show irreversible biased behavior after undergoing a surface redox couple reaction and morphological change. Raman spectroscopy was carried out along with STM and EC-AFM to determine the functional nature and conductivity of the annealed surface.

The plasma-enhanced chemical vapor deposition (PECVD) technique has been utilized for the facile surface deposition of hydrogenated diamond-like carbon (HDLC) thin-films onto Si(100) substrates.

Graphene and graphene-based materials in axonal repair of spinal cord injury

Graphene and graphene-based materials have the ability to induce stem cells to differentiate into neurons, which is necessary to overcome the current problems faced in the clinical treatment of spinal cord injury. This review summarizes the advantages of graphene and graphene-based materials (in particular, composite materials) in axonal repair after spinal cord injury. These materials have good histocompatibility, and mechanical and adsorption properties that can be targeted to improve the environment of axonal regeneration. They also have good conductivity, which allows them to make full use of electrical nerve signal stimulation in spinal cord tissue to promote axonal regeneration. Furthermore, they can be used as carriers of seed cells, trophic factors, and drugs in nerve tissue engineering scaffolds to provide a basis for constructing a local microenvironment after spinal cord injury. However, to achieve clinical adoption of graphene and graphene-based materials for the repair of spinal cord injury, further research is needed to reduce their toxicity.

Cross-linked laminar graphene oxide membranes for wastewater treatment and desalination: A review

Two-dimensional (2D) lamellar graphene oxide (GO) membranes are emerging as attractive materials for molecular separation in water treatment because of their single atomic thickness, excellent hydrophilicity, large specific surface areas, and controllable properties. To yet, commercialization of GO laminar membranes has been hindered by their propensity to swell in hydrated conditions. Thus, chemical crosslinking of GO sheets with the polymer matrix is used to improve GO membrane hydration stability. This review focuses on pertinent themes such as how chemical crosslinking improves the hydration stability, separation performance, and antifouling properties of GO membranes.

On the interface between biomaterials and two-dimensional materials for biomedical applications

Two-dimensional (2D) materials have garnered significant attention due to their ultrathin 2D structures with a high degree of anisotropy and functionality. Reliable manipulation of interfaces between 2D materials and biomaterials is a new frontier for biomedical nanoscience and combining biomaterials with 2D materials offers a promising way to fabricate innovative 2D biomaterials composites with distinct functionality for biomedical applications. Here, we focus exclusively on a summary of the current work in the interface investigation of 2D biomaterials. Specifically, we highlight extraordinary features that make 2D materials so desirable, as well as the molecular level interactions between 2D materials and biomaterials that have been studied thus far. Furthermore, the approaches for investigating the interface characteristics of 2D biomaterials are presented and described in depth. To capture the emerging trend in mass manufacturing of 2D materials, we review the research progress on biomaterial-assisted exfoliation. Finally, we present a critical assessment of newly developed 2D biomaterials in biomedical applications.

In Planta Nitrate Sensor Using a Photosensitive Epoxy Bioresin

Nitrogen management through monitoring of crop nitrate status can improve agricultural productivity, profitability, and environmental performance. Current plant nitrate test methods require expensive instruments, time-intensive labor, and trained personnel. Frequent monitoring of in planta nitrate levels of the stalks in living plants can help to better understand the nitrogen cycle and the physiological responses to environmental variations. Although existing enzymatic electrochemical sensors provide high selectivity, they suffer from short shelf life, high cost, low-temperature storage requirement, and potential degradation over time. To overcome these issues, an artificial enzyme (vitamin B12 or VB12) and a two-dimensional material (graphene oxide or GO) are introduced into a conventional photoresist (SU8) to form a bioresin SU8-GO-VB12 that can be patterned with photolithography and laser-pyrolyzed into a carbon-based nanocomposite C-GO-VB12. The electrocatalytic activity of the cobalt factor in VB12, the surface enhancement properties of GO, and the porous feature of pyrolytic carbon are synergized through design to provide C-GO-VB12 with a superior ability to detect nitrate ions through redox reactions. In addition, laser writing-based selective pyrolysis allows applying thermal energy to target only SU8-GO-VB12 for selective pyrolysis of the bioresin into C-GO-VB12, thus reducing the total energy input and avoiding the thermal influence on the materials and structures in other areas of the substrate. The C-GO-VB12 nitrate sensor demonstrates a year-long shelf lifetime, high selectivity, and a wide dynamic range that enables a direct nitrate test for the extracted sap of maize stalk. For in situ monitoring of the nitrate level and dynamic changes in living maize plants, a microelectromechanical system-based needle sensor is formed with C-GO-VB12. The needle sensor allows direct insertion into the plant for in situ measurement of nitrate ions under different growth environments over time. The needle sensor represents a new method for monitoring in planta nitrate dynamics with no need for sample preparation, thus making a significant impact in plant sciences.

One-Pot Purification and Immobilization of Phenylalanine Dehydrogenase from Bacillus nanhaiensi by Functional Reduced Graphene Oxide

The one-pot immobilization of halophilic phenylalanine dehydrogenase from marine microorganism with metal ions modified reduced graphene oxide (CRGO) material was studied. Phenylalanine dehydrogenase was from Bacillus nanhaiensi and expressed with a C-terminal His-tag. Investigation of CRGO, CRGO-PEI, CRCO-Mn, and CRGO-PEI-Mn for one-pot purification and immobilization of phenylalanine dehydrogenase from crude enzyme solution was carried out. Enzyme activity yield rate achieved 80.0% by immobilization with CRCO-Mn, and the loading capacity was 6.7 mg/mg. Manganese ion coordination greatly improved the selectivity of the CRGO for the target His-tagged enzyme. Furthermore, the effect of NaCl concentration on the immobilization was investigated, which the loading capacity of CRGO-PEI and CRGO-Mn-PEI was increased by 10.7% and 30.6% with 1 M NaCl, respectively. The adsorption curves of crude enzyme one-pot immobilized by CRGO-Mn and purified enzyme immobilized by CRGO-Mn were similar. Therefore, one-pot immobilization strategy is promising for industrial application with advantages such as high efficiency and low cost, which shorten the pipelines for enzyme discovery towards industrial applications through the establishing of marine enzyme collections.

A smartphone-assisted microarray immunosensor coupled with GO-based multi-stage signal amplification strategy for high-sensitivity detection of okadaic acid

Okadaic acid (OA) is one of the main virulence factors of diarrheal shellfish toxins (DSP), which can cause acute carcinogenic or teratogenic effects after ingestion of contaminated shellfish. Therefore, high-sensitivity and fast detection of OA is a key to preventing the occurrence of safety accidents. In this paper, we effectively established a smartphone-assisted microarray immunosensor combined with an indirect competitive ELISA (iELISA) for quantitative colorimetric detection of OA. To further improve the detection sensitivity and match the smartphone imaging, a novel graphene oxide (GO) composite probe was developed to realize the multi-stage signal amplification. The system exhibited a wide linear range for the detection of OA (0.02-33.6 ng ·mL^-1) with low detection limit of 0.02 ng ·mL^-1. The recovery of OA in spiked shellfish samples was in the range of 80%-103.5%, which indicates the good applicability of this biosensor. The whole detection system has advantages of simplicity, low cost, high sensitivity and portability, which is expected to be a powerful alternative tool for on-site detecting and early warning of the pollution of marine products.

Recent Advances in Polyoxometalates with Enzyme-like Characteristics for Analytical Applications

Artificial enzymes based on inorganic solids with both enzyme-mimetic activities and the special material features has been a promising candidate to overcome many deleterious effects of native enzymes in analytical applications. Polyoxometalates (POMs) are an importance class of molecular metal-oxygen anionic clusters. Their outstanding physicochemical properties, versatility and potential applications in energy conversion, magnetism, catalysis, molecular electronics and biomedicine have long been studied. However, the analytical applications of them is limited. Recently, the intrinsic enzymatic activities of POMs have also been found and become an area of growing interest. In this review, along with other reports, we aimed to classify the enzymatic activity of POMs, summarize the construction of POMs-based enzymes, and survey their recent advances in analytical fields. Finally, the current challenges and trends of the polyoxometalates with enzymatic activity in future chemo-/bio-sensing applications are briefly discussed.

Graphene Biosensors-A Molecular Approach

Graphene is the material elected to study molecules and monolayers at the molecular scale due to its chemical stability and electrical properties. The invention of scanning tunneling microscopy has deepened our knowledge on molecular systems through imaging at an atomic resolution, and new possibilities have been investigated at this scale. Interest on studies on biomolecules has been demonstrated due to the possibility of mimicking biological systems, providing several applications in nanomedicine: drug delivery systems, biosensors, nanostructured scaffolds, and biodevices. A breakthrough came with the synthesis of molecular systems by stepwise methods with control at the atomic/molecular level. This article presents a review on self-assembled monolayers of biomolecules on top of graphite with applications in biodevices. Special attention is given to porphyrin systems adsorbed on top of graphite that are able to anchor other biomolecules.

Recent Advances in Electrochemical Sensing of Hydrogen Peroxide (H2O2) Released from Cancer Cells

Cancer is by far the most common cause of death worldwide. There are more than 200 types of cancer known hitherto depending upon the origin and type. Early diagnosis of cancer provides better disease prognosis and the best chance for a cure. This fact prompts world-leading scientists and clinicians to develop techniques for the early detection of cancer. Thus, less morbidity and lower mortality rates are envisioned. The latest advancements in the diagnosis of cancer utilizing nanotechnology have manifested encouraging results. Cancerous cells are well known for their substantial amounts of hydrogen peroxide (H₂O₂). The common methods for the detection of H₂O₂ include colorimetry, titration, chromatography, spectrophotometry, fluorimetry, and chemiluminescence. These methods commonly lack selectivity, sensitivity, and reproducibility and have prolonged analytical time. New biosensors are reported to circumvent these obstacles. The production of detectable amounts of H₂O₂ by cancerous cells has promoted the use of bio- and electrochemical sensors because of their high sensitivity, selectivity, robustness, and miniaturized point-of-care cancer diagnostics. Thus, this review will emphasize the principles, analytical parameters, advantages, and disadvantages of the latest electrochemical biosensors in the detection of H₂O₂. It will provide a summary of the latest technological advancements of biosensors based on potentiometric, impedimetric, amperometric, and voltammetric H₂O₂ detection. Moreover, it will critically describe the classification of biosensors based on the material, nature, conjugation, and carbon-nanocomposite electrodes for rapid and effective detection of H₂O₂, which can be useful in the early detection of cancerous cells.

Graphene-Based Nanomaterials for Biomedical Imaging

Graphene is sp²-hybridized carbon structure-based two-dimensional (2D) sheet. Graphene-based nanomaterials possess several features such as unique mechanical, electronic, thermal, and optical properties, high specific surface area, versatile surface functionalization, and biocompatibility, which attracted researcher's interests in various fields including biomedicine. In this chapter, we particularly focused on the biomedical imaging applications of graphene-based nanomaterials like graphene oxide (GO), reduced graphene oxide (rGO), graphene quantum dots (GQDs), graphene oxide quantum dots (GOQDs), and other derivatives, which utilize their outstanding optical properties. There are some biomedical imaging modalities using Graphene-based Nanomaterials, among which we will highlight fluorescence imaging, Raman imaging, magnetic resonance imaging, and photoacoustic imaging. We also discussed the brief perspectives and future application related to them.

Colorimetric Biosensor Based on Magnetic Enzyme and Gold Nanorods for Visual Detection of Fish Freshness

Histamine, an important safety index for aquatic products, can also be used as a freshness indicator for red-fleshed fish. In this work, magnetic graphene oxide (Fe3O4@GO, MGO) was applied to immobilize diamine oxidase (DAO) through a method of adsorption and covalent bonding. Under the optimized conditions, magnetic DAO prepared by adsorption immobilization had a higher enzyme activity than that of free enzyme, which was selected for the sensor construction. A colorimetric biosensor based on magnetic DAO induced etching of gold nanorods (AuNRs) was developed for the detection of histamine in fish. The developed biosensor showed an excellent response toward histamine with a low detection limit of 1.23 μM and had negligible interference from other diamines. With increasing the histamine concentration, the AuNRs after the reaction exhibited colors ranging from dark green to blue-green, blue, purple, red, and colorless. The etching induced multicolor change of AuNRs indicated the presence of different contents of histamine in mackerel during storage, and was consistent with the overall change in the content of the total volatile basic nitrogen (TVB-N). Thus, it was indicated that the proposed colorimetric biosensor with a naked-eye-detectable readout has a great potential to evaluate the freshness of red-fleshed fish high in histamine.

Preparation and characterization of stable core/shell Fe3O4@Au decorated with an amine group for immobilization of lipase by covalent attachment

The self-assembly approach was used for amine decoration of core/shell Fe₃O₄@Au with 4-aminothiophenol. This structure was used for covalent immobilization of lipase using a Ugi 4-component reaction. The amine group on the structure and carboxylic group from lipase can react in the Ugi reaction and a firm and stable covalent bond is created between enzyme and support. The synthesized structure was fully characterized and its activity was explored in different situations. The results showed the pH and temperature stability of immobilized lipase compared to free lipase in a wide range of pH and temperature. Also after 60 days, it showed excellent activity while residual activity for the free enzyme was only 10%. The synthesized structure was conveniently separated using an external magnetic field and reused 6 times without losing the activity of the immobilized enzyme.

The self-assembly approach was used for amine decoration of core/shell Fe₃O₄@Au with 4-aminothiophenol.