Morphology-Dependent Electrochemistry of Cytochrome c at Au Colloid-Modified SnO2 Electrodes

Sensitive detection of SARS-CoV-2 spike protein based on electrochemical impedance spectroscopy of Fe3O4@SiO2–Au/GCE biosensor

Highly contagious COVID-19 disease is caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which poses a serious threat to global public health. Therefore, the development of a fast and reliable method for the detection of SARS-CoV-2 is an urgent research need. The Fe3O4@SiO2–Au is enriched with a variety of functional groups, which can be used to fabricate a sensitive electrochemical biosensor by biofunctionalization with angiotensin-converting enzyme 2 (ACE2). Accordingly, we developed a novel electrochemical sensor by chemically modifying a glassy carbon electrode (GCE) with Fe3O4@SiO2–Au nanocomposites (hereafter Fe3O4@SiO2–Au/GCE) for the rapid detection of S-protein spiked SARS-CoV-2 by electrochemical impedance spectroscopy (EIS). The new electrochemical sensor has a low limit detection (viz., 4.78 pg/mL) and a wide linear dynamic range (viz., 0.1 ng/mL to 10 μg/mL) for detecting the EIS response signal of S-protein. The robust Fe3O4@SiO2–Au/GCE biosensor has high selectivity, stability, and reproducibility for the detection of S-protein with good recovery of saliva samples.

Molecularly imprinted electrochemical sensor for the ultrasensitive detection of cytochrome c

Cytochrome c (Cyt c) is an important biomarker for the early stage of apoptosis that plays a role in the diagnosis and therapy of several diseases including cancer. Here, an electrochemical sensor based on molecularly imprinted polymer (MIP) for the ultrasensitive detection of Cyt c is studied. It is prepared by electropolymerization of o-phenylenediamine in the presence of Cyt c as template, followed by solvent extraction, resulting in the formation of Cyt c recognition sites. The MIP is characterised by cyclic voltammetry and differential pulse voltammetry, using ferrocenecarboxylic acid as redox probe. Voltammetric data indicates that the MIP-sensor behaves as an electrode with partially blocked surface. The partition isotherm obtained fits the Langmuir model, indicating a high affinity for Cyt c, with an association constant K_a = 5 × 10 ¹¹ M^-1. DPV measurements allow to achieve extremely high analytical sensitivity and low detection limit, in the femtomolar range, with negligible unspecific adsorption. Satisfactory analytical recovery tests performed in the presence of possible interfering proteins and in diluted human serum confirmed the selectivity of the MIP-sensor as well as its potential applicability for real samples analysis.

The role of band structure in Co- and Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ perovskite semiconductor to design an electrochemical aptasensing platform: application in label-free detection of ochratoxin A using voltammetry

Nanocomposites can offer a platform to conjugate biorecognition features of aptamer with unique size-dependent properties of a given material, which can autoprobe the binding event based on their electroactive characteristics. Herein, we design electroactive switchable aptamer probes based on co-doped single-phase semiconducting materials employing the cyclic voltammetry method to record the current signal at each step of electrochemical characterization. To do so, we utilized a facile hydrothermal method assisted by co-precipitation method such as Co-Fe-co-doped Ba_0.5Sr_0.5Zr_0.1Y_0.1O_3-δ (CF-BSZY) and tuned the alignment of the energy band structure of the material to amplify the output of the electrochemical signal. At various steps, changes occurred in the electrochemical properties at the surface of CF-BSZY. The binding of the ssDNA with prepared materials enhances the current signal by the interaction with the target (ochratoxin A (OTA)) depressing the current signal and facilitating the construction of a novel design of electrochemical aptasensor. As a proof of concept, an electrochemical aptasensor for the detection of ochratoxin A (OTA) in rice samples has been developed. The electrochemical aptasensor provides a limit of detection (LOD) of 0.00012 μM (0.12 nM), with a linear range from 0.000247 to 0.74 μM and sound OTA recovery in real samples. The developed aptasensor is simply designed and is free of oligonucleotide labeling or decorative nanoparticle modifications. The proposed mechanism is generic in principle with the potential to translate any type of aptamer and target binding event into a detectable signal; hence, it can be largely applied to various bioreceptor recognition phenomena for subsequent applications.

Nanostructures for Biosensing, with a Brief Overview on Cancer Detection, IoT, and the Role of Machine Learning in Smart Biosensors

Biosensors are essential tools which have been traditionally used to monitor environmental pollution and detect the presence of toxic elements and biohazardous bacteria or virus in organic matter and biomolecules for clinical diagnostics. In the last couple of decades, the scientific community has witnessed their widespread application in the fields of military, health care, industrial process control, environmental monitoring, food-quality control, and microbiology. Biosensor technology has greatly evolved from in vitro studies based on the biosensing ability of organic beings to the highly sophisticated world of nanofabrication-enabled miniaturized biosensors. The incorporation of nanotechnology in the vast field of biosensing has led to the development of novel sensors and sensing mechanisms, as well as an increase in the sensitivity and performance of the existing biosensors. Additionally, the nanoscale dimension further assists the development of sensors for rapid and simple detection in vivo as well as the ability to probe single biomolecules and obtain critical information for their detection and analysis. However, the major drawbacks of this include, but are not limited to, potential toxicities associated with the unavoidable release of nanoparticles into the environment, miniaturization-induced unreliability, lack of automation, and difficulty of integrating the nanostructured-based biosensors, as well as unreliable transduction signals from these devices. Although the field of biosensors is vast, we intend to explore various nanotechnology-enabled biosensors as part of this review article and provide a brief description of their fundamental working principles and potential applications. The article aims to provide the reader a holistic overview of different nanostructures which have been used for biosensing purposes along with some specific applications in the field of cancer detection and the Internet of things (IoT), as well as a brief overview of machine-learning-based biosensing.

Solution-gated graphene transistor based sensor for histamine detection with gold nanoparticles decorated graphene and multi-walled carbon nanotube functionalized gate electrodes

In order to achieve accurate detection and evaluation of the freshness of fish samples, high sensitivity and selectivity of histamine sensors based on solution-gated graphene transistors (SGGT) have been successfully developed. By using graphene (Gra), multi-walled carbon nanotubes (MWNT) and gold nanoparticles (AuNP) to functionalize the gate electrode, the electrocatalytic performance of the device can be significantly improved. We have found that graphene, MWNT and AuNP modified SGGT sensors exhibit an ultra-low detection limit of 100 nM for histamine, a linear range of 3 μM-100 μM. We have also demonstrated that the SGGT-based histamine sensor has a high recovery rate and is capable of assessing the histamine content of actual fish samples in a fast and accurate manner. Considering the superior performance of the SGGT-based histamine sensor, it can be readily extended to histamine determination in many other real food samples for their freshness assessment.

Dual-modal label-free genosensor based on hemoglobin@gold nanocluster stabilized graphene nanosheets for the electrochemical detection of BCR/ABL fusion gene

For the first time, we have successfully synthesized stable graphene nanosheets from graphite powder through sonication in the hemoglobin-capped gold nanoclusters (Hb@AuNCs) solution for biosensing application. This approach, as a simple method for the exfoliation and fragmentation of graphite in a nanocluster solution, enabled us to produce stable aqueous graphene dispersions at low cost and without the need for hazardous chemicals or tedious experimental procedures. In this method, Hb@AuNCs were used not only as stabilizing agent of graphene through non-covalent bonding, but also as dispersing agent of few-layer graphene nanosheets. The Hb@AuNCs stabilized graphene (Hb@AuNCs-G) was characterized by high resolution transmission electron microscopy (HRTEM), zeta-sizer and Raman spectroscopy. Then, the graphene nanosheets were applied as a novel versatile electrochemical platform for ultrasensitive biosensing of short DNA species of chronic myelogenous leukemia (CML) based on the "signal off" and "signal on" strategies. For this purpose, a single strand DNA (ssDNA) was immobilized on the Hb@AuNCs-G/AuNPs modified electrode surface and acted as the biorecognition element. Methylene blue (MB), as the signaling probe, was then intercalated into the ssDNA. The intercalated MB was liberated upon interaction with the synthetic complementary DNA (cDNA, target), thereby resulting in the apparent reduction of MB redox signal. This designed "signal off" sensing system enabled the voltammetric determination of the target cDNA over a dynamic linear range (DLR) of 0.1 fM to 10 pM with a limit of detection (LOD) of 0.037 fM. In the "signal on" strategy, the response to the cDNA was detected by monitoring the change in the electron transfer resistance (R_ct) using the ferro/ferricyanide system as a redox probe. The charge transfer resistance of the probe was found to increase linearly with increasing concentration of target cDNA in the range of 0.1 fM-10 pM with a limit of detection of 0.030 fM. Finally, the selectivity and feasibility of genosensor was evaluated by the analysis of derived nucleotides from mismatched sequences and the clinical samples of patients with leukemia as real samples, respectively.

Highly sensitive immunosensing platform for one-step detection of genetically modified crops

The wide cultivation of genetically modified (GM) insect-resistant crops has raised concerns on the risks to the eco-environment resulting from a release of Cry proteins. Therefore, it is vital to develop a method for the quantification of GM crops. Herein, A highly sensitive immunosensing platform has been developed for both colorimetric and chemiluminescent (CL) detection of Cry 1Ab using dual-functionalized gold nanoparticles (AuNPs) as signal amplification nanoprobes for the first time. In this work, anti-Cry 1Ab monoclonal antibody and horseradish peroxidase (HRP) are simultaneously functionalized on the surface of AuNPs with an exceptionally simple synthesis method. Combined with immunomagnetic separation, this immunosensing platform based on colorimetric method could detect Cry 1Ab in one step in a linear range from 1.0 to 40 ng mL⁻¹ within 1.5 h, with a limit of detection of 0.50 ng mL⁻¹. The sensitivity of fabricated nanoprobes was 15.3 times higher than that using commercial HRP-conjugated antibody. Meanwhile, the fabricated nanoprobes coupled with CL detection was successfully applied for Cry 1Ab detection with a minimum detection concentration of 0.050 ng mL⁻¹ within a linear range of 0.10–20 ng mL⁻¹. The proposed approach was validated with genuine GM crops, and the results showed a good correlation coefficient of 0.9906 compared to those of a commercial ELISA kit. Compared with ELISA, the developed immunosensing platform significantly simplified the assay procedure and shortened the analytical time, thus providing a new platform for the detection of genetically modified crops with high sensitivity, rapidity and simplicity.

Gold Nanoparticle Size-Dependent Enhanced Chemiluminescence for Ultra-Sensitive Haptoglobin Biomarker Detection

Bovine mastitis (BM) is a frequent disease in the dairy industry that causes staggering economical losses due to decreased milk production and increased health care costs. Traditionally, BM detection depends on the efficacy and reliability of analytical techniques that measure somatic cell counts (SCC), detect pathogens, and reveal inflammatory status. Herein, we demonstrate the detection of bovine haptoglobin, a well-documented acute phase protein for evaluating BM clinical status, by utilizing hemoglobin-binding capacity within luminol chemiluminescence (CL) system. The resulting haptoglobin–hemoglobin complex reduces the CL signal proportionally to inherent haptoglobin concentrations. Different sizes of cross-linked gold nanoparticles (GNPs) were examined for enhanced CL (eCL) signal amplification, presenting over 30-fold emitted radiation enhancement for optimized size within real milk samples with respect to nanoparticle-free assay. The eCL values were proportionally related to nanoparticle size and content, influenced by SCC and pathogen type (e.g., Escherichia coli and coagulase-negative staphylococci). The optimized bioassay showed a broad linear response (1 pg mL⁻¹–10 µg mL⁻¹) and minute detection limit of 0.19 pg mL⁻¹, while presenting quantitative performance in agreement with commercial ELISA kit. Finally, the resulting optimized eCL concept offers an efficient label-free detection of haptoglobin biomarker, offering means to diagnose the severity of the associated diseases.

A portable electrochemical immunosensor for highly sensitive point-of-care testing of genetically modified crops

The wide cultivation of genetically modified (GM) crops has raised concerns on the risks to humans and the environment. 5-enolpyruvylshikimate-3-phosphate synthase isolated from Agrobacterium species strain CP4 (CP4-EPSPS) protein is most widely present in these crops. Therefore the measurement of CP4-EPSPS sensitively in a point-of-care testing (POCT) manner for the screening of transgenic plants is demanded. To date the development of quantitative POCT system has not yet been reported. In presented study, an electrochemical immunosensor towards CP4-EPSPS has been fabricated by integrating a portable bioanalytical device with a disposable screen-printed carbon electrode (SPCE) for POCT of GM crops. The dual-functionalized AuNPs were used as nanoprobes and prepared by simultaneously tagging horseradish peroxidase (HRP) and antibody on AuNPs with an exceptionally simple protocol. The sensitivity of the developed nanoprobe-based immunosensor was 62.5-fold higher than that using HRP-labeled antibody. As a result, the proposed immunosensor using SPCE could detect CP4-EPSPS down to 0.050 ng mL^-1 with the linear range of 0.10-10 ng mL^-1 within 65 min. In addition, the developed method has been validated with genuine GM crops and the results show a good correlation coefficient of 0.9909 compared with those of a commercial ELISA kit. Therefore, this portable electrochemical immunosensor is suitable for rapid and sensitive detection and provides a convenient and reliable platform for POCT assay.

Applications of Gold Nanoparticles in Non-Optical Biosensors

Due to their unique properties, such as good biocompatibility, excellent conductivity, effective catalysis, high density, and high surface-to-volume ratio, gold nanoparticles (AuNPs) are widely used in the field of bioassay. Mainly, AuNPs used in optical biosensors have been described in some reviews. In this review, we highlight recent advances in AuNP-based non-optical bioassays, including piezoelectric biosensor, electrochemical biosensor, and inductively coupled plasma mass spectrometry (ICP-MS) bio-detection. Some representative examples are presented to illustrate the effect of AuNPs in non-optical bioassay and the mechanisms of AuNPs in improving detection performances are described. Finally, the review summarizes the future prospects of AuNPs in non-optical biosensors.

Continuous synthesis of gold nanoparticles in micro- and millifluidic systems

Gold nanomaterials have diverse applications ranging from healthcare and nanomedicine to analytical sciences and catalysis. Microfluidic and millifluidic reactors offer multiple advantages for their synthesis and manufacturing, including controlled or fast mixing, accurate reaction time control and excellent heat transfer. These advantages are demonstrated by reviewing gold nanoparticle synthesis strategies in flow devices. However, there are still challenges to be resolved, such as reactor fouling, particularly if robust manufacturing processes are to be developed to achieve the desired targets in terms of nanoparticle size, size distribution, surface properties, process throughput and robustness. Solutions to these challenges are more effective through a coordinated approach from chemists, engineers and physicists, which has at its core a qualitative and quantitative understanding of the synthesis processes and reactor operation. This is important as nanoparticle synthesis is complex, encompassing multiple phenomena interacting with each other, often taking place at short timescales. The proposed methodology for the development of reactors and processes is generic and contains various interconnected considerations. It aims to be a starting point towards rigorous design procedures for the robust and reproducible continuous flow synthesis of gold nanoparticles.

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Fluorimetric Studies of a Transmembrane Protein and Its Interactions with Differently Functionalized Silver Nanoparticles

Transmembrane proteins play important roles in intercellular signaling to regulate interactions among the adjacent cells and influence cell fate. The study of interactions between membrane proteins and nanomaterials is paramount for the design of nanomaterial-based therapies. In the present work, the fluorescence properties of the transmembrane receptor Notch2 have been investigated. In particular, the steady-state and time-resolved fluorescence methods have been used to characterize the emission of tryptophan residues of Notch2 and then this emission is used to monitor the effect of silver colloids on protein behavior. To this aim, silver colloids are prepared with two different methods to make sure that they bear hydrophilic (citrate ions, C-AgNPs) or hydrophobic (dodecanethiol molecules, D-AgNPs) capping agents. The preparation procedures are tightly controlled to obtain metal cores with similar size distributions (7.4 ± 2.5 and 5.0 ± 0.8 nm, respectively), thus, making the comparison of the results easier. The occurrence of strong interactions between Notch2 and D-AgNPs is suggested by the efficient and statistically relevant quenching of the stationary protein emission already at low nanoparticle (NP) concentrations (ca. 12% quenching with [D-AgNPs] = 0.6 nM). The quenching becomes even more pronounced (ca. 60%) when [D-AgNPs] is raised to 8.72 nM. On the other hand, the addition of increasing concentrations of C-AgNPs to Notch2 does not affect the protein fluorescence (intensity variations below 5%) indicating that negligible interactions are taking place. The fluorescence data, recorded in the presence of increasing concentrations of silver nanoparticles, are then analyzed through the Stern-Volmer equation and the sphere of action model to discuss the nature of interactions. The effect of D-AgNPs on the fluorescence decay times of Notch2 is also investigated and a decrease in the average decay time is observed (from 4.64 to 3.42 ns). The observed variations of the stationary and time-resolved fluorescence behavior of the protein are discussed in terms of static and collisional interactions. These results document that the capping shell is able to drive the protein-particle interactions, which likely have a hydrophobic nature.

Surface Engineering of Gold Nanorods for Cytochrome c Bioconjugation: An Effective Strategy To Preserve the Protein Structure

The surface of gold nanorods (Au NRs) has been appropriately engineered to achieve a suitable interface for bioconjugation with horse heart cytochrome c (HCc). HCc, an extensively studied and well-characterized protein, represents an ideal model for nanoparticle (NP)-protein conjugation studies because of its small size, high stability, and commercial availability. Here, the native state of the protein has been demonstrated for the first time, by means of Raman spectroscopy, to be retained upon conjugation with the anisotropic Au nanostructures, thus validating the proposed protocol as specifically suited to mostly preserve the plasmonic properties of the NRs and to retain the structure of the protein. The successful creation of such bioconjugates with the retention of the protein structure and function along with the preservation of the NP properties represents a challenging but essential task, as it provides the only way to access functional hybrid systems with potential applications in biotechnology, medicine, and catalysis. In this perspective, the organic capping surrounding the Au NRs plays a key role, as it represents the functional interface for the conjugation step. Cetyltrimethylammonium bromide-coated Au NRs, prepared by using a seed-mediated synthetic route, have been wrapped with polyacrylic acid (PAA) by means of electrostatic interactions following a layer-by-layer approach. The resulting water-dispersible negatively charged AuNRs@PAA NPs have then been electrostatically bound to the positively charged HCc. The bioconjugation procedure has been thoroughly monitored by the combined analysis of UV-vis absorption, resonance Raman and Fourier transform infrared spectroscopies, transmission electron microscopy microscopy, and ζ-potential, which verified the successful conjugation of the protein to the nanorods.

Molecular Dynamics Simulation of a RNA Aptasensor

Single-stranded RNA aptamers have emerged as novel biosensor tools. However, the immobilization procedure of the aptamer onto a surface generally induces a loss of affinity. To understand this molecular process, we conducted a complete simulation study for the Flavin mononucleotide aptamer for which experimental data are available. Several molecular dynamics simulations (MD) of the Flavin in complex with its RNA aptamer were conducted in solution, linked with six thymidines (T6) and, finally, immobilized on an hexanol-thiol-functionalized gold surface. First, we demonstrated that our MD computations were able to reproduce the experimental solution structure and to provide a meaningful estimation of the Flavin free energy of binding. We also demonstrated that the T6 linkage, by itself, does not generate a perturbation of the Flavin recognition process. From the simulation of the complete biosensor system, we observed that the aptamer stays oriented parallel to the surface at a distance around 36 Å avoiding, this way, interaction with the surface. We evidenced a structural reorganization of the Flavin aptamer binding mode related to the loss of affinity and induced by an anisotropic distribution of sodium cationic densities. This means that ionic diffusion is different between the surface and the aptamer than above this last one. We suggest that these findings might be extrapolated to other nucleic acids systems for the future design of biosensors with higher efficiency and selectivity.

Chemiluminescence of off-line and on-line gold nanoparticle-catalyzed luminol system in the presence of flavonoid

It was found that flavonoids could remarkably inhibit the chemiluminescence (CL) intensity of an off-line gold nanoparticle (AuNP)-catalyzed luminol-H₂ O₂ CL system. By contrast, flavonoids enhanced the CL intensity of an on-line AuNP-catalyzed luminol-H₂ O₂ CL system. In the off-line system, the AuNPs were prepared beforehand, whereas in the on-line system, AuNPs were produced by on-line mixing of luminol prepared in a buffer solution of NaHCO₃  - Na₂ CO₃ and HAuCl₄ with no need for the preliminary preparation of AuNPs. The on-line system had prominent advantages over the off-line system, namely a lowering of the background noise and improvements in the stability of the CL system. The results show that differences in the signal suppression effect of flavonoids on the off-line AuNP-catalyzed CL system are influenced by the combined action of a free radical scavenging effect and occupy-sites function; the latter was proved to be predominant using controlled experiments. Enhancement of the on-line system was ascribed to the presence of flavonoids promoting the on-line formation of AuNPs, which better catalyzed the luminol-H₂ O₂ CL reaction, and the enhancement activity of the six flavonoids increased with the increase in reducibility. This work broadens the scope of practical applications of an AuNP-catalyzed CL system.

Electrochemical Characterization of Ultrathin Cross-Linked Metal Nanoparticle Films

Here we report the preparation, characterization, and electrochemical study of conductive, ultrathin films of cross-linked metal nanoparticles (NPs). Nanoporous films ranging from 40 to 200 nm in thickness composed of gold and platinum NPs of ∼5 nm were fabricated via a powerful layer-by-layer spin coating process. This process allows preparation of uniform NP films as large as 2 × 2 cm(2) with precise control over thickness, structure, and electrochemical and electrocatalytic properties. Gold, platinum, and bimetallic NP films were fabricated and characterized using cyclic voltammetry, scanning electron microscopy, and conductance measurements. Their electrocatalytic activity toward the oxygen reduction reaction (ORR) was investigated. Our results show that the electrochemical activity of such NP films is initially hindered by the presence of dense thiolate cross-linking ligands. Both electrochemical cycling and oxygen plasma cleaning are effective means in restoring their electrochemical activity. Gold NP films have higher electric conductivity than platinum possibly due to more uniform film structure and closer particle-particle distance. The electrochemical and electrocatalytic performance of platinum NP films can be greatly enhanced by the incorporation of gold NPs. This work focuses on electrochemical characterization of cross-linked NP films and demonstrates several unique properties. These include quick and easy preparation, ultrathin and uniform film thickness, tunable structure and composition, and transferability to many other substrates.

Electrochemiluminescence of Supramolecular Nanorods and Their Application in the "On-Off-On" Detection of Copper Ions

In this work, an "on-off-on" switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu(2+) ) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10-perylenetetracarboxylic acid (PTCA) and aniline. The initial "signal-on" state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co-reaction accelerator. In addition, ECL quencher probes (Fc-NH2 /Cu-Sub/nano-Au) were fabricated by immobilizing aminoferrocene (Fc-NH2 ) on Cu-substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu-enzyme strand to form Cu(2+) -specific DNAzyme. Similarly, the "signal-off" state was obtained by the high quenching effect of Fc-NH2 on the ECL of the excited-state PTCA ((1) PTCA*). As expected, the second "switch-on" state could achieved by incubating with the target Cu(2+) , owing to the Cu(2+) -specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (ΔIECL ) before and after incubating with the target Cu(2+) , the prepared Cu(2+) -specific DNAzyme-based biosensor was used for the determination of Cu(2+) concentrations with high sensitivity, excellent selectivity, and good regeneration.

Functional core/shell drug nanoparticles for highly effective synergistic cancer therapy

Gold (Au)-nanoshelled 10-hydroxycamptothecin nanoparticles (HCPT NPs) are developed with combination of photothermal therapy and chemotherapy for highly effective cancer therapy. The strong near-infrared (NIR) absorbance from Au nanoshells endows the nanocomposites photothermal effects and on-demand drug release. Notably, the drug-loading content reaches up to 63.7 wt%, which is much higher than that in the previously reported nanovehicles systems. Both in vitro and in vivo studies indicate that the combined local specific chemotherapy with external NIR photothermal therapy demonstrates a synergistic effect, which is significantly better than either of them alone. More importantly, due to the high drug-loading content and efficient photothermal effects of the nanocomposites, 100% in vivo tumor elimination is achieved at a low laser irradiation power density of 1 W cm(-) (2) without weight loss and tumor recurrence. No obvious systematic toxicity is observed for the injected mice, indicating the good biocompatibility of this kind of multifunctional drug nanocomposites. This work highlights the great potential of drug-nanostructure-based multifunctional core/shell nanpocomposite for highly efficient cancer therapy.

Nanomaterial-Based Electrochemical Immunosensors for Clinically Significant Biomarkers

Nanotechnology has played a crucial role in the development of biosensors over the past decade. The development, testing, optimization, and validation of new biosensors has become a highly interdisciplinary effort involving experts in chemistry, biology, physics, engineering, and medicine. The sensitivity, the specificity and the reproducibility of biosensors have improved tremendously as a result of incorporating nanomaterials in their design. In general, nanomaterials-based electrochemical immunosensors amplify the sensitivity by facilitating greater loading of the larger sensing surface with biorecognition molecules as well as improving the electrochemical properties of the transducer. The most common types of nanomaterials and their properties will be described. In addition, the utilization of nanomaterials in immunosensors for biomarker detection will be discussed since these biosensors have enormous potential for a myriad of clinical uses. Electrochemical immunosensors provide a specific and simple analytical alternative as evidenced by their brief analysis times, inexpensive instrumentation, lower assay cost as well as good portability and amenability to miniaturization. The role nanomaterials play in biosensors, their ability to improve detection capabilities in low concentration analytes yielding clinically useful data and their impact on other biosensor performance properties will be discussed. Finally, the most common types of electroanalytical detection methods will be briefly touched upon.

Enhanced effect of aggregated gold nanoparticles on luminol chemiluminescence system and its analytical application

Some organic compounds containing groups of OH, NH2, or SH, which could induce the aggregation of gold nanoparticles (AuNPs), were observed to enhance effectively the luminol-H2O2-2.6 nm AuNPs CL system. It was found that the aggregation of AuNPs was an important effect factor for the catalytic activity of AuNPs on luminol CL system. The aggregated AuNPs could effectively enhance luminol CL signal compared with the dispersed one. The enhanced effect was closely related to the sizes of AuNPs. Among the studied AuNPs with seven sizes, 2.6 nm AuNPs had the greatest enhancement effect on luminol CL system after its aggregation. The CL enhancement mechanism was investigated, and the marked enhancement of aggregated 2.6 nm AuNPs for luminol CL system was supposed to originate from the decrease of AuNPs' surface negative charge density compared to its dispersed state. For the luminol-H2O2-2.6 nm AuNPs CL system in the presence of organic compounds containing groups of OH, NH2, or SH, more than one factor played the role in influencing the CL intensity. It was found that the enhanced effect of aggregated 2.6 nm AuNPs induced by such organic compounds was much more significant than the inhibition effect of reducing groups of OH, NH2, or SH, which made it applicable for the determination of this kind of compounds.

Amperometric detection of dopamine in human serum by electrochemical sensor based on gold nanoparticles doped molecularly imprinted polymers

In this work, a highly sensitive and selective biomimetic electrochemical sensor for the amperometric detection of trace dopamine (DA) in human serums was achieved by gold nanoparticles (AuNPs) doped molecularly imprinted polymers (MIPs). Functionalized AuNPs (F-AuNPs), a novel functional monomer bearing aniline moieties on the surface of the AuNPs, were prepared via a direct synthesis method and then used to fabricate the conductive MIPs film on the modified electrode by electropolymerization method in the presence of DA and p-aminobenzenethiol (p-ATP). The obtained electrochemical sensor based on the conductive film of AuNPs doped MIPs (AuNPs@MIPs) could effectively minimize the interferences caused by ascorbic acid (AA) and uric acid (UA). The linear range for amperometric detection of DA was from 0.02 μmol L(-1) to 0.54 μmol L(-1) with the detection limit of 7.8 nmol L(-1) (S/N=3). Furthermore, the AuNPs@MIPs modified electrode (AuNPs@MIES) was successfully employed to detect trace DA in different human serums.