A superoxide dismutase mimic nanocomposite for amperometric sensing of superoxide anions

Increased Range of Catalytic Activities of Immobilized Compared to Colloidal Gold Nanoparticles

Gold nanoparticles (AuNPs) can be described as nanozymes, species that are able to mimic the catalytic activities of several enzymes, such as oxidase/peroxidase, reductase, or catalase. Most studies in the literature focus on the colloidal suspension of AuNPs, and it is obvious that their immobilization could open the doors to new applications thanks to their increased stability in this state. This work aimed to investigate the behavior of surfaces covered by immobilized AuNPs (iAuNPs). Citrate-stabilized AuNPs (AuNPs-cit) were synthesized and immobilized on glass slides using a simple dip coating method. The resulting iAuNPs were characterized (surface plasmon resonance, microscopy, quantification of immobilized AuNPs), and their multi-enzymatic-like activities (oxidase-, peroxidase-, and catalase-like activity) were evaluated. The comparison of their activities versus AuNPs-cit highlighted their added value, especially the preservation of their activity in some reaction media, and their ease of reuse. The huge potential of iAuNPs for heterogeneous catalysis was then applied to the degradation of two model molecules of hospital pollutants: metronidazole and methylene blue.

Chromogenic Mechanisms of Colorimetric Sensors Based on Gold Nanoparticles

The colorimetric signal readout method is widely used in visualized analyses for its advantages, including visualization of test results, simple and fast operations, low detection cost and fast response time. Gold nanoparticles (Au NPs), which not only exhibit enzyme-like activity but also have the advantages of tunable localized surface plasmon resonance (LSPR), high stability, good biocompatibility and easily modified properties, provide excellent platforms for the construction of colorimetric sensors. They are widely used in environmental monitoring, biomedicine, the food industry and other fields. This review focuses on the chromogenic mechanisms of colorimetric sensors based on Au NPs adopting two different sensing strategies and summarizes significant advances in Au NP-based colorimetric sensing with enzyme-like activity and tunable LSPR characteristics. In addition, the sensing strategies based on the LSPR properties of Au NPs are classified into four modulation methods: aggregation, surface modification, deposition and etching, and the current status of visual detection of various analytes is discussed. Finally, the review further discusses the limitations of current Au NP-based detection strategies and the promising prospects of Au NPs as colorimetric sensors, guiding the design of novel colorimetric sensors.

Development of nanozyme based sensors as diagnostic tools in clinic applications: a review

Since 1970, many artificial enzymes that imitate the activity and structure of natural enzymes have been discovered. Nanozymes are a group of nanomaterials with enzyme-mimetic properties capable of catalyzing natural enzyme processes. Nanozymes have attracted great interest in biomedicine due to their excellent stability, rapid reactivity, and affordable cost. The enzyme-mimetic activities of nanozymes may be modulated by numerous parameters, including the oxidative state of metal ions, pH, hydrogen peroxide (H2O2) level, and glutathione (GSH) concentration, indicating the tremendous potential for biological applications. This article delivers a comprehensive overview of the advances in the knowledge of nanozymes and the creation of unique and multifunctional nanozymes, and their biological applications. In addition, a future perspective of employing the as-designed nanozymes in biomedical and diagnostic applications is provided, and we also discuss the barriers and constraints for their further therapeutic use.

Synergistic effect of manganese (II) phosphate & diamond nanoparticles in electrochemical sensors for reactive oxygen species determination in seminal plasma

In this work, we explore the ability of manganese (II) phosphate (MnP) as a catalytic element for the determination of reactive oxygen species (ROS) in seminal plasma, when MnP is employed as modifier of a glassy carbon electrode. The electrochemical response of the manganese (II) phosphate-modified electrode shows a wave at around +0.65 V due to the oxidation of Mn²⁺ to MnO₂⁺, which is clearly enhanced after addition of superoxide, the molecule considered as the mother of ROS. Once proved the suitability of manganese (II) phosphate as catalyst, we evaluate the effect of including a 0D (diamond nanoparticles) or a 2D (ReS₂) nanomaterial in the sensor design. The system consisting of manganese (II) phosphate and diamond nanoparticles yielded the largest improvement of the response. The morphological characterization of the sensor surface was performed by scanning electron microscopy and atomic force microscopy, while cyclic and differential pulse voltammetry were employed for the electrochemical characterization of the sensor. After optimizing the sensor construction, calibration procedures by chronoamperometry were performed, leading to a linear relation between peak intensity and the superoxide concentration in the range of 1.1 10^-4 M - 1.0 10^-3 M with a limit of detection of 3.2 10^-5 M. Seminal plasma samples were analysed by the standard addition method. Moreover, the analysis of samples fortified with superoxide at the μM level leads to recoveries of 95%.

Antioxidant Nanozymes: Mechanisms, Activity Manipulation, and Applications

Antioxidant enzymes such as catalase, superoxide dismutase, and glutathione peroxidase play important roles in the inhibition of oxidative-damage-related pathological diseases. However, natural antioxidant enzymes face some limitations, including low stability, high cost, and less flexibility. Recently, antioxidant nanozymes have emerged as promising materials to replace natural antioxidant enzymes for their stability, cost savings, and flexible design. The present review firstly discusses the mechanisms of antioxidant nanozymes, focusing on catalase-, superoxide dismutase-, and glutathione peroxidase-like activities. Then, we summarize the main strategies for the manipulation of antioxidant nanozymes based on their size, morphology, composition, surface modification, and modification with a metal-organic framework. Furthermore, the applications of antioxidant nanozymes in medicine and healthcare are also discussed as potential biological applications. In brief, this review provides useful information for the further development of antioxidant nanozymes, offering opportunities to improve current limitations and expand the application of antioxidant nanozymes.

Interaction Mechanisms and Interface Configuration of Cysteine Adsorbed on Gold, Silver, and Copper Nanoparticles

Cysteine-protected metal nanoparticles (NPs) have shown interesting physicochemical properties of potential utility in biomedical applications and in the understanding of protein folding. Herein, cysteine interaction with gold, silver, and copper NPs is characterized by Raman spectroscopy and density functional theory calculations to elucidate the molecular conformation and adsorption sites for each metal. The experimental analysis of Raman spectra upon adsorption with respect to free cysteine indicates that while the C-S bond and carboxyl group are similarly affected by adsorption on the three metal NPs, the amino group is sterically influenced by the electronegativity of each metal, causing a greater modification in the case of gold NPs. A theoretical approach that takes into consideration intermolecular interactions using two cysteine molecules is proposed using a S-metal-S interface motif anchored to the metal surface. These interactions generate the stabilization of an organo-metallic complex that combines gauche (P_H) and anti (P_C) rotameric conformers of cysteine on the surface of all three metals. Similarities between the calculated Raman spectra and experimental data confirm the thiol and carboxyl as adsorption groups for gold, silver, and copper NPs and suggest the formation of monomeric "staple motifs" that have been found in the protecting monolayer of atomic-precise thiolate-capped metal nanoclusters.

Electrochemical sensors based on metal nanoparticles with biocatalytic activity

Biosensors have attracted a great deal of attention, as they allow for the translation of the standard laboratory-based methods into small, portable devices. The field of biosensors has been growing, introducing innovations into their design to improve their sensing characteristics and reduce sample volume and user intervention. Enzymes are commonly used for determination purposes providing a high selectivity and sensitivity; however, their poor shelf-life is a limiting factor. Researchers have been studying the possibility of substituting enzymes with other materials with an enzyme-like activity and improved long-term stability and suitability for point-of-care biosensors. Extra attention is paid to metal and metal oxide nanoparticles, which are essential components of numerous enzyme-less catalytic sensors. The bottleneck of utilising metal-containing nanoparticles in sensing devices is achieving high selectivity and sensitivity. This review demonstrates similarities and differences between numerous metal nanoparticle-based sensors described in the literature to pinpoint the crucial factors determining their catalytic performance. Unlike other reviews, sensors are categorised by the type of metal to study their catalytic activity dependency on the environmental conditions. The results are based on studies on nanoparticle properties to narrow the gap between fundamental and applied research. The analysis shows that the catalytic activity of nanozymes is strongly dependent on their intrinsic properties (e.g. composition, size, shape) and external conditions (e.g. pH, type of electrolyte, and its chemical composition). Understanding the mechanisms behind the metal catalytic activity and how it can be improved helps designing a nanozyme-based sensor with the performance matching those of an enzyme-based device.

Room-Temperature Harvesting Oxidase-Mimicking Enzymes with Exogenous ROS Generation in One Step

Despite the advantages of low cost, high stability, and activities, a majority of nanozymes rely on strict synthesis conditions and precise size/structure control, hindering the stable, bulk, and high-yield production that is necessary for general use. To facilitate the transition of nanozymes from benchtop to real-world applications, we herein present a one-step approach, which only needs mixing of two broad commercialized reagents at room temperature, to harvest gold nanoparticles-bovine serum albumin (BSA) nanocomposite (BSA-Au) with distinct oxidase-like activity and good stability in a broad range of harsh conditions. Density functional theory (DFT) calculations demonstrate the oxidase-like activity of BSA-Au stemming from thermodynamically and kinetically favored facets for O2 activation. The reactive oxygen species (ROS) generation of BSA-Au contributes to the catalytic activities and further enables water sterilization and antibacterial applications against superbugs. This one-step strategy promises great potential in bulk production of nanozyme for broad application beyond laboratory use.

Methods to evaluate the scavenging activity of antioxidants toward reactive oxygen and nitrogen species (IUPAC Technical Report)

This project was aimed to identify the quenching chemistry of biologically important reactive oxygen and nitrogen species (ROS/RNS, including radicals), to show antioxidant action against reactive species through H‐atom and electron transfer reactions, and to evaluate the ROS/RNS scavenging activity of antioxidants with existing analytical methods while emphasizing the underlying chemical principles and advantages/disadvantages of these methods. In this report, we focused on the applications and impact of existing assays on potentiating future research and innovations to evolve better methods enabling a more comprehensive study of different aspects of antioxidants and to provide a vocabulary of terms related to antioxidants and scavengers for ROS/RNS. The main methods comprise the scavenging activity measurement of the hydroxyl radical (•OH), dioxide(•1–) (O2 •–: commonly known as the superoxide radical), dihydrogen dioxide (H2O2: commonly known as hydrogen peroxide), hydroxidochlorine (HOCl: commonly known as hypochlorous acid), dioxidooxidonitrate(1–) (ONOO−: commonly known as the peroxynitrite anion), and the peroxyl radical (ROO•). In spite of the diversity of methods, there is currently a great need to evaluate the scavenging activity of antioxidant compounds in vivo and in vitro. In addition, there are unsatisfactory methods frequently used, such as non-selective UV measurement of H2O2 scavenging, producing negative errors due to incomplete reaction of peroxide with flavonoids in the absence of transition metal ion catalysts. We also discussed the basic mechanisms of spectroscopic and electrochemical nanosensors for measuring ROS/RNS scavenging activity of antioxidants, together with leading trends and challenges and a wide range of applications. This project aids in the identification of reactive species and quantification of scavenging extents of antioxidants through various assays, makes the results comparable and more understandable, and brings a more rational basis to the evaluation of these assays and provides a critical evaluation of existing ROS/RNS scavenging assays to analytical, food chemical, and biomedical/clinical communities by emphasizing the need for developing more refined, rapid, simple, and low‐cost assays and thus opening the market for a wide range of analytical instruments, including reagent kits and sensors.

Potentiality of Nanoenzymes for Cancer Treatment and Other Diseases: Current Status and Future Challenges

Studies from past years have observed various enzymes that are artificial, which are issued to mimic naturally occurring enzymes based on their function and structure. The nanozymes possess nanomaterials that resemble natural enzymes and are considered an innovative class. This innovative class has achieved a brilliant response from various developments and researchers owing to this unique property. In this regard, numerous nanomaterials are inspected as natural enzyme mimics for multiple types of applications, such as imaging, water treatment, therapeutics, and sensing. Nanozymes have nanomaterial properties occurring with an inheritance that provides a single substitute and multiple platforms. Nanozymes can be controlled remotely via stimuli including heat, light, magnetic field, and ultrasound. Collectively, these all can be used to increase the therapeutic as well as diagnostic efficacies. These nanozymes have major biomedical applications including cancer therapy and diagnosis, medical diagnostics, and bio sensing. We summarized and emphasized the latest progress of nanozymes, including their biomedical mechanisms and applications involving synergistic and remote control nanozymes. Finally, we cover the challenges and limitations of further improving therapeutic applications and provide a future direction for using engineered nanozymes with enhanced biomedical and diagnostic applications.

Nanozymes in Point-of-Care Diagnosis: An Emerging Futuristic Approach for Biosensing

Nanomaterial-based artificial enzymes (or nanozymes) have attracted great attention in the past few years owing to their capability not only to mimic functionality but also to overcome the inherent drawbacks of the natural enzymes. Numerous advantages of nanozymes such as diverse enzyme-mimicking activities, low cost, high stability, robustness, unique surface chemistry, and ease of surface tunability and biocompatibility have allowed their integration in a wide range of biosensing applications. Several metal, metal oxide, metal-organic framework-based nanozymes have been exploited for the development of biosensing systems, which present the potential for point-of-care analysis. To highlight recent progress in the field, in this review, more than 260 research articles are discussed systematically with suitable recent examples, elucidating the role of nanozymes to reinforce, miniaturize, and improve the performance of point-of-care diagnostics addressing the ASSURED (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to the end user) criteria formulated by World Health Organization. The review reveals that many biosensing strategies such as electrochemical, colorimetric, fluorescent, and immunological sensors required to achieve the ASSURED standards can be implemented by using enzyme-mimicking activities of nanomaterials as signal producing components. However, basic system functionality is still lacking. Since the enzyme-mimicking properties of the nanomaterials are dictated by their size, shape, composition, surface charge, surface chemistry as well as external parameters such as pH or temperature, these factors play a crucial role in the design and function of nanozyme-based point-of-care diagnostics. Therefore, it requires a deliberate exertion to integrate various parameters for truly ASSURED solutions to be realized. This review also discusses possible limitations and research gaps to provide readers a brief scenario of the emerging role of nanozymes in state-of-the-art POC diagnosis system development for futuristic biosensing applications.

Biomimetic electrochemical sensors: New horizons and challenges in biosensing applications

The urge to meet the ever-growing needs of sensing technology has spurred research to look for new alternatives to traditional analytical methods. In this scenario, the glucometer is the flagship of commercial electrochemical sensing platforms, combining selectivity, reliability and portability. However, other types of enzyme-based biosensors seldom achieve the market, in spite of the large and increasing number of publications. The reasons behind their commercial limitations concern enzyme denaturation, and the high costs associated with procedures for their extraction and purification. In this sense, biomimetic materials that seek to imitate the desired properties of natural enzymes and biological systems have come out as an appealing path for robust and sensitive electrochemical biosensors. We herein portray the historical background of these biomimicking materials, covering from their beginnings until the most impactful applications in the field of electrochemical sensing platforms. Throughout the discussion, we present and critically appraise the major benefits and the most significant drawbacks offered by the bioinspired systems categorized as Nanozymes, Synzymes, Molecularly Imprinted Polymers (MIPs), Nanochannels, and Metal Complexes. Innovative strategies of fabrication and challenging applications are further reviewed and evaluated. In the end, we ponder over the prospects of this emerging field, assessing the most critical issues that shall be faced in the coming decade.

Atomically Dispersed Co to an End-Adsorbing Molecule for Excellent Biomimetically and Prime Sensitively Detecting O2•- Released from Living Cells

Single-atom catalysis efficiently exposes the catalytic sites to reactant molecules while rendering opportunity to investigate the catalysis mechanisms at atomic levels for scientific insights. Here, for the first time, atomically dispersed Co atoms are synthesized as biomimetic "enzymes" to monitor superoxide anions (O₂^•-), delivering ultraordinary high sensitivity (710.03 μA·μM^-1·cm^-2), low detection limit (1.5 nM), and rapid response time (1.2 s), ranking the best among all the reported either bioenzymatic or biomimetic O₂^•- biosensors. The sensor is further successfully employed to real-time monitor O₂^•- released from living cells. Moreover, theoretical calculation and analysis associated with experimental results discover that a mode of end adsorption of the negatively charged O₂^•- on the Co³⁺ atom rather than a bridge or/and side adsorption of the two atoms of O₂^•- on two Co³⁺ atoms, respectively, plays an important role in the single-atomic catalysis toward O₂^•- oxidation, which not only facilitates faster electron transfer but also offers better selectivity. This work holds great promise for an inexpensive and sensitive atomic biomimetic O₂^•- sensor for bioresearch and clinic diagnosis, while revealing that the adsorption mode plays a critical role in single-atom catalysis for a fundamental insight.

Synthesis, Catalytic Properties and Application in Biosensorics of Nanozymes and Electronanocatalysts: A Review

The current review is devoted to nanozymes, i.e., nanostructured artificial enzymes which mimic the catalytic properties of natural enzymes. Use of the term "nanozyme" in the literature as indicating an enzyme is not always justified. For example, it is used inappropriately for nanomaterials bound with electrodes that possess catalytic activity only when applying an electric potential. If the enzyme-like activity of such a material is not proven in solution (without applying the potential), such a catalyst should be named an "electronanocatalyst", not a nanozyme. This paper presents a review of the classification of the nanozymes, their advantages vs. natural enzymes, and potential practical applications. Special attention is paid to nanozyme synthesis methods (hydrothermal and solvothermal, chemical reduction, sol-gel method, co-precipitation, polymerization/polycondensation, electrochemical deposition). The catalytic performance of nanozymes is characterized, a critical point of view on catalytic parameters of nanozymes described in scientific papers is presented and typical mistakes are analyzed. The central part of the review relates to characterization of nanozymes which mimic natural enzymes with analytical importance ("nanoperoxidase", "nanooxidases", "nanolaccase") and their use in the construction of electro-chemical (bio)sensors ("nanosensors").

Bacteriophage-Based Biosensor for Detection of E. coli Bacteria on Graphene Modified Carbon Paste Electrode

Background:

Escherichia coli (E. coli) bacteria is one of the hazardous human pathogens. Consequently, developing the rapid and effective method for identification and quantization of E. coli is popular in biotechnological researches in recent years.

Experimental:

In this research, a label-free capacitance E. coli biosensor was fabricated based on immobilizing bacteriophage on the carbon paste electrode (Cp). Reduced graphene (RGr) was synthesized and used as a substrate for immobilization of bacteriophage on the Cp surface. E. coli bacteriophage was trapped in graphene modified carbon paste electrodes. The immobilization accuracy was confirmed via electrochemical techniques. The modified electrodes were applied as indicator electrodes for capacitance measurements of E. coli.

Results:

Through this method, E. coli was detected in a concentration range of 33×10-3 to 330×10-3 N L-1 (number of E. coli per Liter) with a correlation coefficient of 0.99 and a detection limit of 12×10-3 N L-1.

Conclusion:

The proposed biosensor has a fast response time of about 5 s and good selectivity over other bacteria.

Electrochemical detection of superoxide anions in HeLa cells by using two enzyme-free sensors prepared from ZIF-8-derived carbon nanomaterials

Two kinds of carbon-based nanozymes were constructed from the same precursor of zeolitic imidazolate framework-8 (ZIF-8) for O₂^•- determination. Hollow carbon cubic nanomaterial (labelled as HCC) was obtained by chemically etching ZIF-8 with tannic acid and a subsequent calcination. A porous carbon cubic nanomaterial (labelled as PCC) was prepared by directly pyrolysis. Then HCC and PCC were immobilized on the surface of screen printed carbon electrodes (SPCE), fabricating HCC and PCC modified electrodes (denoted as HCC/SPCE and PCC/SPCE). HCC/SPCE, best operated at -0.5 V (vs. Ag/AgCl), has a sensitivity of 6.55 × 10² nA μM^-1 cm^-2 with a detection limit of 207 nM (at S/N = 3) for O₂^•- sensing. And PCC/SPCE, best operated at -0.4 V (vs. Ag/AgCl), exhibited a superior performance for O₂^•- detection with a sensitivity of 1.14 × 10³ nA μM^-1 cm^-2 and a low detection limit of 140 nM (at S/N = 3). The two sensors possess excellent reproducibility and stability. They were used to sense O₂^•- released from HeLa cells. Graphical abstract Illustration of the synthesis of the hollow carbon cubic nanomaterial (HCC) and of the porous carbon cubic nanomaterial (PCC), and the scheme for detection of superoxide anions in HeLa cell.

Tailoring pore structures with optimal mesopores to remarkably promote DNA adsorption guiding the growth of active Mn3(PO4)2 toward sensitive superoxide biomimetic enzyme sensors

The great challenge in preparing a biomimetic enzyme sensor is to have sensitivity and selectivity equal to or better than its corresponding biological sensor. Porous electrodes possess a large surface area and are often used to greatly improve the sensor sensitivity. However, how to tailor the pore structure, especially the pore size distribution to further improve the sensitivity and selectivity of a biomimetic sensor, has not been investigated yet. The superoxide anion (O2˙-) plays essential roles in various biological processes and is of importance in clinical diagnosis and life science research. It is generally detected by the superoxide dismutase enzyme. Herein, we delicately tailor the pore structure of carbon nanofibers (CNFs) by pyrolysis to obtain an optimal mesopore structure for strong adsorption of DNA, followed by guiding the growth of Mn3(PO4)2 as a biomimetic enzyme toward highly sensitive detection of O2˙-. The Mn3(PO4)2-DNA/CNF sensor achieves the best sensitivity among the reported O2˙- sensors while possessing good selectivity. The enhancement mechanism is also investigated, indicating that the mesopore ratio of CNFs plays an essential role in the high sensitivity and selectivity due to their strong adsorption of DNA for guiding the growth of a large amount of uniform sensing components, Mn3(PO4)2, toward high sensitivity and selectivity. The biomimetic sensor was further used to in situ monitor O2˙- released from human keratinocyte cells and human malignant melanoma cells under drug stimulation, showing high sensitivity to real-time quantitative detection of O2˙-. This work provides a highly sensitive in situ real-time biomimetic O2˙- sensor for applications in biological research and diagnosis, while shedding light on the enhancement mechanism of the pore structure, especially the pore size distribution of a porous electrode for high performance sensing processes.

Carbon-mediated synthesis of shape-controllable manganese phosphate as nanozymes for modulation of superoxide anions in HeLa cells

Here we present a facile method to fabricate shape-controllable transition metal phosphates by using hollow carbon structures as substrates for superoxide sensing.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Silver-gold-apoferritin nanozyme for suppressing oxidative stress during cryopreservation

Reactive oxygen species (ROS) cause oxidative stress, which involves in the pathogenesis of many serious diseases. Apoferittin containing gold-silver nanoparticles (Au-Ag-AFT) was designed and evaluated as a nanozyme for scavenging the ROS. The nanozyme consisting of silver-gold nanohybrid in apoferittin cage represents superoxide dismutase, catalase and peroxidase mimetic activities. The Au-Ag-AFT nanozyme was characterized by spectroscopy, FESEM, TEM and dynamic light scattering. The inhibition process for pyrogallol autoxidation was used for assaying the superoxide dismutase mimetic activity and measuring the kinetic parameters of Au-Ag-AFT nanozyme. Additionally, Aebi method and standard protocol was used for evaluating the catalase and peroxidase mimetic activity. The k_cat values for superoxide dismutase, catalase and peroxidase mimetics activity were 1.4 × 10⁶, 0.1 and 9 × 10³ s^-1 respectively. These values indicated that Au-Ag-AFT nanozyme could act as a suitable ROS scavenger. Additionally, Au-Ag-AFT nanozyme was examined as a protective agent for human sperm against oxidative stress induced during the cryopreservation process. Presence of the nanozyme in the sperm media significantly increased the motility and viability of the cells and also decreased the ROS, apoptosis and necrosis (P < 0.05) compare to the control group.

Cytotoxic effect of albumin coated copper nanoparticle on human breast cancer cells of MDA-MB 231

PURPOSE

The aim of this study was to design a new nanocomposite that would have high cytotoxicity against invasive breast cancer cells and minimum side effects on normal cells.

METHODS

An albumin nano-carrier for delivery of CuNPs was developed. The ACuNPs formation was characterized by TEM, DLS and UV-Vis, fluorescence and circular dichroism spectroscopy. The cytotoxic efficacy of the ACuNPs against human breast cancer cells (MDA-MB 231) and normal cells (MCF-10A) was compared using a standard MTT assay. The mechanism of cell death induced by ACuNPs was considered by inverted and fluorescent microscopy, flow cytometry and gel electrophoresis. The effects of compounds on ROS generations in MDA-MB 231 cells were also studied.

RESULTS

It was found that the resulted ACuNPs with a diameter of 62.7 nm and zeta potential of about -10.76 mV, are suitable for extravasation into tumor cells. In ACuNPs, the 90% of the secondary structure and almost all the tertiary structure of albumin remained intact. Comparing to CuNPs, ACuNPs could significantly suppress the viability of cancer cells while they were less toxic on normal cells. Compared with the untreated cells, the MDA-MB 231 cell line showed higher levels of ROS production after treatment with ACuNPs. The increase in ROS production after 24 hours indicated that ACuNPs induce apoptosis.

CONCLUSIONS

The ACuNPs characteristics such as intact structure of albumin, high toxicity against cancer cells comparing to normal cells and apoptosis induction as the mechanism of cell death, revealed that this nanocomposite is a good candidate to be used as a chemotherapeutic agent against invasive breast cancer cells.

Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers

A novel ratiometric fluorescence nanosensor for superoxide anion (O₂^•- ) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb³⁺ and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O₂^•- . The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O₂^•- demonstrated high sensitivity and selectivity with a wide linear response range (14 nM-10 μM) and a low detection limit (4.7 nM).