Nanocomposite Of Gold Nanoparticles Research Articles

Application of Recycled Battery-Graphite Electrode Decorated with Polyglutamic Acid/Au Nanoparticles for Detection of Nalbuphine Drug Abuse

Abstract We report a highly-uniform nanocomposite of polyglutamic acid (PGA) and gold nanoparticles (AuNPs) electrodeposited on a recycled battery graphite electrode (BGE) for the detection of Nalbuphine (NB), a semi-synthetic opioid. The sensor was optimized and characterized morphologically (via scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray analysis) and electrochemically (via cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy). Under optimized conditions, the PGA/AuNPs/BGE revealed two linear ranges, 2.5×10-8 to1.0×10-6 M, and 2.0 × 10-6 to 1.0 × 10-4 M for Nalbuphine (NB), that is equivalent to 9.825×10-3 to 0.393 µg/mL and 0.786 to 39.30 µg/mL, with R2 = 0.995 and 0.994, respectively, and showed good catalytic activity for the determination of nalbuphine in the presence of tramadol and the oxidation potential of these opioid analgesic drugs were separated. The sensor was successfully applied for the detection of NB in its pharmaceutical formulations, spiked urine, and human plasma samples, without applying any sample pretreatment, at a recovery range of 99±0.03 to102±0.02% and thus, the developed can be considered as a promising approach for NB abuse testing in clinical and forensic agencies.

An ultra-sensitive bimetallic based electrochemical sensor for analysis of total iron, total dissolved iron, and granular iron in coastal water

Different iron species play crucial roles in the biogeochemical cycle, so their determination is important. Electrochemical methods are among the most promising and easiest methods for the rapid on-site determination of different iron species. In this study, a new electrode—Au–Bi/ITO—based on the commercial indium tin oxide (ITO) electrode was etched and functionalized with bismuth nanoparticles (BiNPs) and gold nanoparticles (AuNPs) nanocomposites for voltammetric analysis of iron species in coastal water. After etching, the ITO electrode exhibits a higher number of attachment sites for the nanomaterials, thereby improving the stability of the resulting electrode, and the introduction of the nanomaterials improves the sensitivity of the electrode, making it easier to realize on-site detection. Under the synergistic effect of the two nanomaterials, the Au-Bi/ITO electrode showed excellent performance for the determination of different iron species in coastal water. Under the optimal conditions, the Au-Bi/ITO electrode peak current was linear in the concentration range from 5 nM to 1.5 μM with an ultralow detection limit of 1.4 nM. The results are consistent with certified values when the electrode is used for the determination of Fe(III) in certified reference materials. In summary, the Au-Bi/ITO electrode, with its high stability and sensitivity, has been successfully used for the direct determination of different Fe(III) species in coastal water via cathodic stripping voltammetry. This electrode is simple to prepare, easy to use, economical, and highly promising for future applications involving the rapid on-site detection of different iron species.

Multiplex electrochemical aptasensor for the simultaneous detection of linomycin and neomycin antibiotics

The escalating use of antibiotics across diverse sectors, including human healthcare, agriculture, and livestock, has led to their pervasive presence in the environment, raising concerns about their impact on ecosystems and human health. Traditional detection methods, reliant on high-performance liquid chromatography and immuno-assays, face challenges of complexity, cross-reactivity, and limited specificity. Aptamer-based biosensors offer a promising alternative, leveraging the specificity, stability, and cost-effectiveness of aptamers. Herein, we present a novel dual-screen-printed carbon electrode (SPCE) biosensor, modified with a nanocomposite of gold nanoparticles (AuNPs) and carbon nanofibers (CNFs), for the label-free electrochemical detection of lincomycin and neomycin antibiotics. Lincomycin and neomycin, two antibiotics of environmental concern due to their widespread usage and potential ecological impact, were simultaneously detected using square wave voltammetry. The aptasensors showed high sensitivity with detection limits of 0.02 pg/mL and 0.035 pg/mL for lincomycin and neomycin, respectively. The developed biosensor exhibited high selectivity and reproducibility in detecting both antibiotics. This multiplex biosensing platform offers a promising strategy for efficient and cost-effective monitoring of antibiotic residues in environmental samples, addressing the critical need for robust detection methods in environmental monitoring and public health surveillance.

An electrochemical/SERS dual-mode immunosensor using TMB/Au nanotag and Au@2D-MoS2 modified screen-printed electrode for sensitive detection of prostate cancer biomarker

This study describes a novel dual-mode immunosensor that combines electrochemical (EC) and surface-enhanced Raman scattering (SERS) techniques for the detection of prostate-specific antigen (PSA), a biomarker associated with prostate cancer. The sensor consists of a nanocomposite of gold nanoparticles (AuNPs) deposited on two-dimensional (2D) molybdenum disulfide (Au@MoS2) modified on a working carbon electrode of a screen-printed electrode (SPE). Subsequently, the primary antibody (Ab1) is immobilized on the modified electrode, creating Ab1/Au@MoS2/SPE for specific recognition of the target PSA. In parallel, AuNPs are conjugated with a secondary antibody (Ab2) and a probe molecule, 3,3′,5,5′-tetramethylbenzidine (TMB), leading nanotags (TMB/Ab2/AuNPs) formation exhibiting strong SERS and EC responses. Upon the presence of the target, sandwich immunocomplexes can be formed through antigen-antibody interactions (Ab1-PSA-Ab2). The differential pulse voltammetry (DPV) technique is employed for EC detection mode, while a handheld Raman spectrometer with a 785 nm excitation laser is utilized to collect SERS signals. The developed system demonstrates excellent selectivity and sensitivity, with low limits of detection (LODs) of 3.58 pg mL−1 and 4.83 pg mL−1 for EC and SERS sensing, respectively. Importantly, the dual-mode immunosensor proves effective quantifying PSA protein in human serum samples with good recovery. Given its high sensitivity and proficiency in analyzing biological samples, this proposed immunosensor holds promise as an alternative tool for the early diagnosis of cancers.

Electroanalysis of Catechol and Hydroquinone by Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes, β-cyclodextrin Decorated with Reduced Graphene Oxide - Gold Nanoparticle Nanocomposite

In this work, the glassy carbon electrode was modified by multi-walled carbon nanotubes, β-cyclodextrin, reduced graphene oxide, and gold nanoparticle nanocomposites GC/MWCNTs/β-CD-rGO@Au). The GC/MWCNTs/β-CD-rGO@Au electrode was utilized for simultaneous monitoring of catechol (CC) and hydroquinone (HQ). The modified electrode has a clear pair of voltammetric peaks for CC and HQ, which makes it an appropriate tool for the simultaneous determination of the two isomers. Under optimized conditions, the oxidation peak currents of CC and HQ at GC/MWCNTs/β-CD-rGO@Au were increased linearly in the 1–173 μM and 2–80 μM concentration range with the limit of detection (LOD) (based on S/N = 3) of 0.17 μM and 0.26 μM. The GC/MWCNTs/β-CD-rGO@Au exhibits adequate stability, repeatability, and recovery in analyzing two dihydroxybenzenes isomers.

Sensitive Electrochemical Sensor for Gallic Acid Determination in Honey Based on g-C3N4/AuNPs Modified Carbon Paste Electrode

Gallic acid (GA) is a well-known polyphenol that occurs naturally in plants and is used as a chemical marker or standard antioxidant in analytical research. Here, a carbon paste electrode was modified with a nanocomposite of graphitic carbon nitride and gold nanoparticles (g-C3N4/AuNPs/CPE). The g-C3N4/AuNPs was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. Electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry methods were used to investigate the electrochemical behavior of GA on the electrode. EIS analysis exhibited lower charge-transfer resistance in g-C3N4/AuNPs/CPE than CPE; 250 vs 1500 Ω, respectively. The g-C3N4/AuNPs/CPE was used to GA sensing with limit of detection and linear response range of 0.025 and 0.16–4.10 μM, respectively via DPV. Then, the GA content in Iranian honey samples with different floral origins such as Ziziphus, Barberry, Thyme, Astragalus, Eucalyptus and Coriander was successfully determined. According to result, the fabricated electrochemical sensor could be useful for GA evaluation in food samples.

A sensitive aptasensor mediated by gold nanoparticles/metal organic framework lattice for detection of Pb2+ ion in marine products

Herein, an enzyme-free fluorescent aptasensor was introduced for the ultrasensitive quantification of lead (Pb2+) ion as a hazardous pollutant of the environment and foodstuffs. A nanocomposite of zeolitic imidazolate frameworks-8 and gold nanoparticles (ZIF-8@AuNPs) was utilized as an efficient quencher of the fluorescence intensity of carboxyfluorescein (FAM) signal reporter. The establishment of a hybrid structure between attached aptamer on ZIF-8@AuNPs nanocomposite, and its FAM-tagged complementary (CP) strand decreased the fluorescence response. The preferential binding between the aptamer and Pb2+ released CP strands, which retrieved the fluorescence signal. The aptasensor could assess Pb2+ in the linear concentration range of 1 pM-1 nM with a detection limit (LOD) of 0.24 pM. Besides, it could quantify Pb2+ in various samples, including fish, shrimp, tap water, milk, and serum samples. The developed aptasensor with the superiorities of easiness, cost-effectiveness, easy-to-operate, and rapidness is promising for controlling marine foodstuff safety.

Selective Determination of Nicotinamide Adenine Dinucleotide (NADH) on Screen-Printed Polyethylene Terephthalate (PET) Electrodes Modified with a Reduced Graphene Oxide (rGO), Gold Nanoparticle (AuNP), and Poly-Methylene Blue Nanocomposite

The present work reports the development of a disposable nanocomposite-based amperometric sensor for reduced nicotinamide adenine dinucleotide (NADH). To fabricate disposable electrodes, conductive carbon and silver ink were screen-printed on a polyethylene terephthalate (PET) film substrate. The surface of the working electrode was modified with gold nanoparticles (AuNPs) decorated reduced graphene oxide (rGO) and subsequently electro-polymerized with methylene blue for the determination of NADH. The nanocomposite modified electrode decreases the potential for NADH oxidation with a significant increase in the current due to the synergy between AuNP and rGO. The developed electrochemical sensor determined NADH at 0 V versus pseudo-Ag/AgCl with linear relationships from 25 µmol L−1 to 1.0 mmol L−1 and 1.0 mmol L−1 to 10 mmol L−1. The sensor exhibits a good sensitivity of 35.49 µA/mmol L−1/cm2 and a detection limit of 6.61 µmol L−1 based upon a signal-to-noise ratio of 3. Furthermore, interferences from electroactive substances such as ascorbic acid and uric acid are eliminated at an oxidation potential of 0 V. Thus, the modified electrode provides a simple, selective, disposable, and low-cost approach for the amperometric determination of NADH.

Functionalized gold nanoparticle enhanced nanorod hyperbolic metamaterial biosensor for highly sensitive detection of carcinoembryonic antigen

Hyperbolic metamaterial (HMM) biosensors based on metals have superior performance in comparison with conventional plasmonic biosensors in the detection of low concentrations of molecules. In this study, a nanorod HMM (NHMM) biosensor based on refractive index changes for carcinoembryonic antigen (CEA) detection is developed using secondary antibody modified gold nanoparticle (AuNP-Ab2) nanocomposites as signal amplification element for the first time. Numerical analysis based on finite element method is conducted to simulate the perturbation of the electric field of bulk plasmon polariton (BPP) supported by a NHMM in the presence of a AuNP. The simulation reveals an enhancement of the localized electric field, which arises from the resonant coupling of BPP to the localized surface plasmon resonance supported by AuNPs and is beneficial for the detection of changes of the refractive index. Furthermore, the AuNP-Ab2 nanocomposites-based NHMM (AuNP/Ab2-NHMM) biosensor enables CEA detection in the visible and near-infrared regions simultaneously. The highly sensitive detection of CEA with a wide linear range of 1–500 ng/mL is achieved in the near-infrared region. The detectable concentration of the AuNP/Ab2-NHMM biosensor has a 50-fold decrease in comparison with a NHMM biosensor. A low detection limit of 0.25 ng/mL (1.25 pM) is estimated when considering a noise level of 0.05 nm as the minimum detectable wavelength shift. The proposed method achieves high sensitivity and good reproducibility for CEA detection, which makes it a novel and viable approach for biomedical research and early clinical diagnostics.

Mediated Electrosynthesis of Nanocomposites of Gold Nanoparticles with Cyclobis (paraquat-p-phenylene)

The result of cyclobis(paraquat-p-phenylene) (CBPQT4+) –mediated reduction of gold ions generated by anodic oxidation of metallic gold in MeCN (50% vol.)—H2O/0.05 M Bu4NCl medium in the absence and presence of such stabilizers as cetyltrimethylammonium chloride and polyvinylpyrrolidone is polydisperse aggregated composite nanoparticles with sizes ranging from several nm to 100 nm or more. The resulting AuNP@(CBPQT4+)n nanocomposite is a gold nanoparticle encapsulated in a shell of macrocycle molecules. CBPQT4+ is bound to the surface of the gold nanoparticle by donor-acceptor interactions between the electron-withdrawing viologen units and the electron-donating metal particle. Theoretical calculations suggest that the cavity of the bound macrocycle is not empty, but filled with 10–12 gold atoms. CBPQT4+ presumably forms a monomolecular layer on the metal surface, and its excess amount is involved in the aggregation and sedimentation of the nanocomposites. The encapsulation of AuNPs in the macrocyclic shell is the main reason for the suppression of the metal catalytic activity in the test reaction of p-nitrophenol reduction with sodium borohydride.

Piezo-photodynamic therapy of Au@PEG-ZnO nanostructures enabled with a battery-free wireless cancer therapeutic dot

Cancer remains a global health concern, necessitating advanced therapeutic strategies to address its fatal challenges. Conventional treatments, such as radiotherapy and chemotherapy, often lack tumor specificity and may induce systemic toxicity. Photodynamic therapy (PDT) and sonodynamic therapy (SDT) have emerged as promising alternatives, demonstrating high specificity and minimal side effects. In this study, we propose a novel piezo-photodynamic therapy (PPDT) enabled with battery-free wireless cancer therapeutic dot, in which the nanocomposites of gold nanoparticles (Au NPs), zinc oxide nanorods (ZnO NRs) and hydrophilic polyethylene glycol (PEG) can enhance reactive oxygen species (ROS) generation and effectively inhibit tumor growth. The therapeutic dot is implanted directly inside the tissue around the tumor and wirelessly controlled by ultrasound (US), allowing dual activation of electron-hole pairs from the nanocomposites via US and ultraviolet light (UV). The internally generated piezoelectric field minimizes electron-hole recombination, maximizing ROS induction within tumor cells. This PPDT approach surpasses the efficacy of conventional PDT and SDT, showcasing a synergistic therapeutic effect. The study further elucidates the detailed mechanism of Au@PEG-ZnO NRs catalysts, providing insights into their piezoelectric-photocatalytic action. The battery-free wireless control and minimally invasive implantation of the therapeutic dot with inorganic piezo-photocatalyst open new perspectives in cancer therapy.

Cu2+-doped zeolitic imidazolate frameworks and gold nanoparticle (AuNPs@ZIF-8/Cu) nanocomposites enable label-free and highly sensitive electrochemical detection of oral cancer-related biomarkers.

It is of great significance to accurately and sensitively detect oral cancer-related biomarkers (ORAOV 1) for the early diagnosis of oral cancer. Present here is a novel electrochemical biosensor based on Cu2+-doped zeolitic imidazolate frameworks and gold nanoparticle (AuNPs@ZIF-8/Cu) nanocomposites and a one-step strand displacement reaction for label-free, simple and sensitive detection of ORAOV 1 in saliva. It is worth noting that AuNPs@ZIF-8/Cu nanocomposites show large electrochemically effective surface area, good electrical conductivity and electrocatalytic activity due to the synergistic effect of metal nanoparticles (MNPs) and ZIF-8. Consequently, the newly developed electrochemical sensor displays a wide linear range of 0.1-104 pM and a low limit of detection (LOD) of 63 fM. Meanwhile, the electrochemical biosensor can distinguish single base mismatch. The relative standard deviation (RSD) of intra-assays and inter-assays is 1.46% and 1.76%, respectively, and the peak current values decline by 9.20% with a RSD value of 1.35% after being stored at 4 °C for 7 days, suggesting that the newly designed electrochemical sensor exhibits good selectivity, reproducibility and stability to detect ORAOV 1. More importantly, this novel electrochemical sensor is found to be applicable for detecting ORAOV 1 in human saliva samples with a satisfactory result. The RSD values range from 1.15% to 1.77%, and the recoveries range from 95.46% to 112.98%.

In-situ electropolymerization of congo red-doped polypyrrole and gold nanoparticle nanocomposites and its electrocatalytic application

A one-step electrochemical approach has been utilized to synthesize congo-red doped polypyrrole film embedded with gold nanoparticles (PPy-CR-AuNP). This study discusses for the first time the electrocatalytic properties of PPy-CR and PPy-CR-AuNP as counter-electrode in dye-sensitized solar cell (DSSC). Physicochemical characterizations of the films with and without AuNP have been presented. Both films/electrodes displayed excellent charge transfer abilities, as demonstrated by cyclic voltammetry analysis. Notably, PPy-CR-AuNP exhibited enhanced electron transfer kinetics with a 17% increase in electroactive surface area and improved efficiency in the I−/I3− redox pair activity compared to PPy-CR. Following extended storage under ambient conditions, PPy-CR-AuNP maintained a better mass transport and electron transfer at the electrode-electrolyte interface. The DSSC employing PPy-CR-AuNP as counter electrode exhibited a 12.5% enhancement in efficiency, lower electron transport time, higher electron recombination time and electron collection efficiency of up to 89%. Moreover, the electron decay rate was found to be 12.5% lower compared to the DSSC with PPy-CR electrode. These results demonstrated that PPy-CR-AuNP is an appropriate candidate for DSSC.

An electrochemical biosensor based on graphene intercalated functionalized black phosphorus/gold nanoparticles nanocomposites for the detection of bacterial enzyme

Sortase A (Srt A) is a key enzyme that catalyzes the covalent anchoring of surface proteins to the bacterial cell wall and plays a dominant role in the late stage of Gram-positive bacterial infections. Achieving activity detection of Srt A and inhibitors screening is important for the treatment of Gram-positive bacterial infections and novel antibacterial drugs research. Here, an electrochemical sensor pattern is proposed. Black phosphorus (BP) is a novel graphite-like two-dimensional material with excellent electrochemical properties. However, the extremely poor environmental stability limits its practical application. The surface modification of BP using graphene oxide (GO) significantly improves the stability, and obtained partially reduced graphite oxide functionalized BP composites combine both electrical conductivity and stability. In this paper, we develop an electrochemical biosensor based on partially reduced graphite oxide functionalized BP /gold nanoparticles (p-rGO-BP/AuNPs) nanocomposites for detecting Srt A activity. The assay utilizes two peptide chains, P1 (CLPETG) and P2 (GGGGG), which can be linked by the presence of Srt A. At the same time, the process is monitored by differential pulse voltammetry (DPV). The sensor showed good selectivity and stability with a linear dynamic range of 1 pM-100 nM and a detection limit (LOD) of 0.65 pM. In addition, the method was successfully used to detect Srt A in complex samples and estimate the half-inhibitory concentration (IC50) of Srt A inhibitors (curcumin, dihydromyricetin and rutin).

Clay-based durable catalyst membranes of porous layered double hydroxide and gold nanoparticle nanocomposites for fast and continuous-flow reactions

We synthesized the hybrid catalyst of a porous layered double hydroxide (LDH) decorated with ultrasmall Au nanoparticles. The porous LDH was prepared by coprecipitation and ethanol washing, producing thin LDH nanoplatelets. Thereafter, spray drying was carried out, affording a few hundred nm of the hydrangea-like structure of the LDH with an extensive open network and a Brunauer–Emmett–Teller surface area of 386 m2/g. Its sizable open frame and active hydroxide surface enabled the uniform decoration of average 4-nm-diameter Au nanoparticles (Au/P-LDH) through one-pot chemical reduction using NaBH4 at room temperature. We applied the Au/P-LDH for the fabrication of catalyst membranes, which are potentially valuable for the continuous flow of catalytic reactions, e.g., the hydrogenation of p-nitrophenol. This study suggested that their porous structure and active Au nanoparticle catalyst allowed fast and mass catalytic functions by simple filtration without washing or catalyst recovery steps. We found no significant damage to the hybrid membrane during the reactions with a few liters; thus, we expect strong bindings of the Au nanoparticles on the surface of the porous LDH.

PCR- and label-free SARS-CoV-2 electrochemical immunosensor

Cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are still ubiquitously persistent, as new variants have emerged worldwide. Furthermore, severity and infectiousness are still not fully understood. Therefore, an imperative need still exists for more and better viral detection and diagnosis tools. Nanostructured electrochemical biosensors have shown outstanding features for highly sensitive Coronavirus disease 2019 (COVID-19) detection and diagnosis. This work reports on an electrochemical immunosensor based on nanocomposite-decorated screen-printed carbon electrodes (SPCE) for one-step detection of the spike protein by differential pulse voltammetry (DPV) without the need for enzymatic or PCR amplification. The SPCEs were decorated with graphene quantum dots (GQDs) coexisting with gold and platinum nanoparticle nanocomposite (GQDs@AuPt), improving their conductive properties and offering a high surface area and available carboxylic groups for the covalent immobilization of capture recombinant antibodies. As a result, the biosensor demonstrated high sensitivity and specificity in detecting spike protein by DPV in a linear range from 0.05 to 1.5 µg/mL and with a LOD of 60.14 ng/mL (0.78 nM). In addition, its potential application was demonstrated by detecting eleven positive concerning four negative nasopharyngeal swab samples from patients with COVID-19 and healthy individuals previously analyzed by the RT-PCR gold standard.

An ultrasensitive electrochemical immunosensor for CA72-4 based on a signal amplification strategy of MoS2 nanoflower-supported Au nanoparticles

Accurate detection of cancer antigen 72-4 (CA72-4), a tumor-associated glycoprotein, is of great significance for gastric cancer diagnosis and immunotherapy monitoring. Modification of noble metal nanoparticles on transition metal dichalcogenides can significantly enhance functions, such as electron transport. Molybdenum disulfide gold nanoparticles nanocomposites (MoS2-Au NPs) were prepared in this study and a series of characterization studies were carried out. In addition, a label-free, highly sensitive electrochemical immunosensor molybdenum disulfide -Au nanoparticles/Glassy carbon electrode (MoS2-Au NPs/GCE) was also prepared and used for the detection of CA72-4. The electrochemical performance of the immunosensor was characterized by electrochemical techniques, such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The results indicated that better MoS2-Au NPs nanomaterials have been synthesized, and the prepared electrochemical immunosensor, MoS2-Au NPs/GCE, showed excellent electrochemical performance. The sensor exhibited high detection sensitivity under optimal conditions, including an incubation time of 30 min, an incubation temperature of 25 °C, and a pH of 7.0. The electrochemical immunosensor also had a low detection limit of 2.0 × 10−5 U/mL (S/N = 3) in a concentration range of 0.001–200 U/mL, with good selectivity, stability, and repeatability. In conclusion, this study provided a theoretical basis for the highly sensitive detection of tumor markers in clinical biological samples.

Gold-oxoborate nanocomposite-coated orthodontic brackets gain antibacterial properties while remaining safe for eukaryotic cells.

The study's main objective is to limit bacterial biofilm formation on fixed orthodontic appliances. Bacterial biofilm formation on such devices (e.g., brackets) causes enamel demineralization, referred to as white spot lesions (WSL). WSL is significant health, social and economic problem. We provide a nanotechnology-based solution utilizing a nanocomposite of gold nanoparticles embedded in a polyoxoborate matrix (BOA: B-boron, O-oxygen, A-gold, Latin aurum). The nanocomposite is fully inorganic, and the coating protocol is straightforward, effective, and ecologically friendly (low waste and water-based). Prepared coatings are mechanically stable against brushing with a toothbrush (up to 100 min of brushing). Bacteria adhesion and antibacterial properties are tested against Streptococcus mutans-common bacteria in the oral cavity. BOA reduces the adhesion of bacteria by around 78%, that is, from around 7.99 × 105 ± 1.33 × 105 CFU per bracket to 1.69 × 105 ± 3.07 × 104 CFU per bracket of S. mutans detached from unmodified and modified brackets, respectively. Modified fixed orthodontic brackets remain safe for eukaryotic cells and meet ISO 10993-5:2009 requirements for medical devices. The gathered data show that BOA deposited on orthodontic appliances provides a viable preventive measure against bacteria colonization, which presents frequent and significant complications of orthodontic treatment.

Reduced Graphene Oxide‐Gold Nanoparticle Nanohybrid Modified Cost‐Effective Paper‐Based Biosensor for Procalcitonin Detection

AbstractThe present study reports the fabrication of reduced graphene oxide (rGO)/gold nanoparticles (AuNP) nanocomposites modified cellulose fiber paper‐based electrochemical biosensor for procalcitonin (PCT) biomarker detection. PCT is a biomarker specific for bacterial infection (BI) detection and has gained much attention as a potential solution to the problems associated with determining appropriate antibiotic use. In sepsis and other severe infections, serum PCT levels increase to values above 100 ng mL−1 in response to pro‐inflammatory stimulation. The structural and morphological characterization of the rGO‐AuNP composite are investigated using UV‐Vis spectroscopy, FTIR spectroscopy, X‐ray diffraction, and scanning electron microscopy. Monoclonal antibodies specific to PCT were covalently immobilized onto the rGO‐AuNP nanocomposite modified paper to fabricate an electrochemical biosensor. The fabricated biosensor exhibits linearity in the PCT concentration range 10 −15×103 pg mL−1, with a low detection limit 10 pg mL−1. Furthermore, the proposed biosensor also exhibited good selectivity and could detect PCT biomarkers even in the presence of other interfering electroactive species such as glucose, oxalic acid, and urea. The proposed CF‐based biosensor has been proven as an accelerated simple point‐of‐care (POC) exploratory approach for early PCT diagnosis in inadequate areas with limited production facilities, computational techniques, and highly skilled experts.

Study of the effects of Au@ZIF-8 on metabolism in mouse RAW 264.7 macrophages.

Mass spectrometry-based metabolomics plays a vital role in discovering new markers and revealing the unpredictable biological effects of external stimuli. However, the current metabolomics research on materials is still in its infancy, and in-depth research on possible toxic mechanisms is lacking. In this study, a nanocomposite of gold nanoparticles (AuNPs)-zeolite-imidazole framework-8 (ZIF-8) (Au@ZIF-8) was designed to investigate its effects on metabolism in mouse RAW 264.7 macrophages. The successful synthesis of Au@ZIF-8 was confirmed by transmission electron microscopy (TEM) and elemental analysis. The changes in the metabolic activity of mouse RAW 264.7 macrophages at different concentrations of Au@ZIF-8 and different treatment times were investigated, and their influence on the morphological changes and behavior of RAW 264.7 cells was discussed. In addition, ultrahigh-performance liquid chromatography quadrupole-orbital high-resolution mass spectrometry (UHPLC/Q-Orbitrap HRMS) was used to study the metabolic effects of Au@ZIF-8 on RAW 264.7 cells, and the results showed different metabolites being expressed at different reaction times. After 4, 8 and 24h of treatment, the differential expression of 14, 16, and 16 metabolites, respectively, was detected. Twenty-five candidate key metabolites were identified from the results of the expression patterns and metabolic pathways. These metabolites are related to glutamine metabolism, the tricarboxylic acid cycle and glycolytic metabolic pathways, which may provide insight into the treatment of diseases caused and progressed by glutamine metabolism. This study also indicates the effectiveness of high-resolution LC-MS in revealing the nanotoxicity mechanism of Au@ZIF-8.