Fabrication Of Immunosensors Research Articles

Fabrication of a Label-Free Immunosensor Using Surface-Engineered AuPt@GQD Core-Shell Nanocomposite for the Selective Detection of Trace Levels of Escherichia coli from Contaminated Food Samples.

Fabrication of label-free immunosensors is highly necessitated due to their simplicity, cost-effectiveness, and robustness. Herein, we report the facile development of a label-free, direct, rapid, capacitive immunosensor for ultrasensitive and rapid recognition of trace levels of Escherichia coli from contaminated food samples. This was achieved using gold platinum core-shell nanoparticles loaded with graphene quantum dots (AuPt@GQDs) that were utilized as electrode modifiers. The incorporation of GQDs to the surface of AuPt core-shell nanoparticles was performed using the "greener" probe-sonication method. The electrochemical properties of AuPt@GQDs, determined using cyclic voltammetry and electrochemical impedance spectroscopy, suggested the optimized loading concentration of AuPt to be 0.05% in the core-shell nanocomposite to exhibit the highest current response. Furthermore, immobilization of anti-E. coli monoclonal antibodies (anti-E. coli mAb) onto the surface of modified electrodes was performed using amine coupling. The high specific binding of E. coli cells onto the surface of the immuno-electrode was measured as a direct function of change in transient capacitance with time that was measured at low and high frequencies. The resultant immunosensor (bovine serum albumin/anti-E. coli mAb/AuPt0.05@GQDs/FTO) demonstrated a detection range (5 to 4.5 × 103 cells/mL), with the detection limit as low as 1.5 × 102 cells/mL, and an excellent sensitivity ∼171,281.40 μF-1 mL cells-1 cm-2 without the use of any labels (R2-0.99). These findings were further verified using real sample analysis wherein the immuno-electrode demonstrated outstanding sensitivity, the highest noticed so far. More interestingly, the high resuability ∼48 weeks (RSD-5.92%) and excellent reproducibility in detection results (RSD ∼ 9.5%) testify its potential use in a clinical setting. The results reveal the usefulness of the surface-engineered AuPt@GQDs core-shell nanocomposite as an electrode modifier that can be used for the development of newer on-site monitoring devices to estimate trace levels of pathogens present as contaminants in food samples.

An ultrasensitive electrochemical immunosensor based on meso-PdN NCs and Au NPs/N-CNTs for quantitative cTnI detection

Electrochemical immunosensors have gained considerable attention in detecting human disease markers due to their excellent specificity, high sensitivity, and facile operation. Herein, a rational-designed sandwich-type electrochemical immunosensor is constructed for the sensitive detection of cardiac troponin I (cTnI) using nitrogen-doped carbon nanotubes loaded with gold nanoparticles (Au NPs/N-CNTs) as substrate and highly active mesoporous palladium-nitrogen nanocubes (meso-PdN NCs) as secondary antibody markers. Benefitting from its large specific surface area (638.04 m2 g−1) and high nitrogen content, novel polydopamine (PDA)/ halloysite nanotubes (HNTs) hybrid derived one-dimensional (1D) N-CNTs can provide more binding sites for the in-situ growth of Au NPs to connect Ab1. Furthermore, as an ideal substrate material, Au NPs/N-CNTs exhibit finely tuned mesoporous structures and outstanding conductivity, which facilitate the mass and electron transfer during the electrocatalysis process. Besides, highly concave surfaces and crystalline mesopores of meso-PdN NCs expose more surfaces and crevices, providing abundant reactive sites for H2O2 reduction. Remarkably, the as-obtained immunosensor presented a wide linear range (from 10 fg mL−1 to 100 ng mL−1) and an excellent low detection limit (9.85 fg mL−1). This study may offer new insights into the precise fabrication of efficient electrochemical immunosensors for various clinical diagnosis applications.

Nafion-based label-free immunosensor as a reliable warning system: The case of AFB1 detection in cattle feed

This study presents a simple method for the rapid and versatile fabrication of label-free immunosensors on Nafion-modified screen-printed platforms. Herein, Nafion is exploited both as an immobilization matrix and as a weak (unexpectedly) electrochemical enhancer for the first time. The electrochemical characteristics in terms of diffusivity and conductivity of thin cation-exchange polymer membrane-modified screen-printed electrodes were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The free electrode surface area, the diffusion coefficient, the peak-to-peak separation, the heterogeneous electron transfer constant, and the charge transfer resistance for Nafion-modified and bare SPE have been calculated and compared. Then, Nafion-SPEs were employed to develop a competitive label-free immunoassay for the quantitative detection of Aflatoxin B1. Morphological characterization of the proposed immunosensor was performed using Scanning Electron Microscopy, and its analytical performance was evaluated using square wave voltammetry as a detection technique and [Fe(CN)6]3−/4− as a redox probe. The immunosensor showed satisfactory results in spiked cattle feed in terms of limit of detection (3.8 ngmL−1), linear range (LR 10–100 ngmL−1), sensitivity (33.0 ngmL−1) and reproducibility (RSD%<10%). The comparison of performance to that of a labelled immunosensor and a conventional chromatographic technique revealed a strong correlation between the respective results, but with shorter analysis time for the proposed tool. Furthermore, The present study achieved evidence of the dependability of the proposed method, proving that its use as an early warning system for the detection of AFB1 in cattle feed is something doable and not an abstract idea.

Trends in advanced materials for the fabrication of insulin electrochemical immunosensors

Trends in advanced materials for the fabrication of insulin electrochemical immunosensors

Electrochemical sensing of trypanosome- and flavivirus-related neglected tropical diseases

Virus infections and parasitic diseases that are often found in tropical countries represent a large burden on societies in those regions but are unfortunately rarely studied by electrochemistry. These neglected tropical diseases (NTDs) are a concerning issue, especially in developing nations because a challenged healthcare system often negatively affects the economy. Besides the exploration of new treatment strategies, the development of early diagnostic methods is crucial to attenuate negative impacts related to NTDs. This review highlights the most recent developments of electrochemical biosensing efforts for five NTDs, Chagas disease, leishmaniasis, sleeping sickness, dengue fever and Zika virus infection, which affect a number of Latin American, African, and Asian countries. Special focus is placed on the design and fabrication of genosensors and immunosensors, designed as innovative and promising diagnostic tools with the potential of being integrated into portable systems to advance the development of point-of-care devices.

Advanced Materials for Immunosensing of Pharmaceutical and Drug Compounds

Real-time and accurate levels of pharmaceuticals undertake critical effects in the therapy process. Thus, reliable detection of pharmaceuticals is important for regulating the proper concentration of them to enhance the effectiveness and to decrease possible side effects. However, the development of new reliable sensory systems is the main prerequisite for the mentioned aims. Immunosensors can be regarded as an effective tool due to their sensitivity and unique specificity originating from the intrinsic nature of the antigen-antibody interaction. This review reports material tendencies in the development of immunosensors for pharmaceuticals (veterinary and human) which have been reported in the last few years. Carbon-based (graphene, graphene oxide, carbon nanotubes, etc.), gold, and magnetic materials are the main materials for the fabrication of pharmaceutical immunosensors. Also, this review reports benefits and limitations on the reported immunosensor and mechanism and analytical performance of the immunoplatforms to address future researches.

Bovine Serum Albumin-Dependent Charge-Transfer Kinetics Controls the Electrochemical Immunosensitive Detection: Vibrio cholerae as a Model Bioanalyte.

This work investigates how bovine serum albumin (BSA), a commonly used protein in the fabrication of electrochemical immunosensors, can impact on the sensitivity of detection when integrated with antibody (Ab) pre-encapsulated with (i) insulating polyacrylonitrile (PAN) fibre (i.e., GCE-PAN-Ab-BSA immunosensor) or (ii) conducting PAN-grafted iron (II) phthalocyanine (FePc) (i.e., GCE-PAN@FePc-Ab-BSA immunosensor), using Vibrio cholerae toxin as a case study bioanalyte. Both immunosensors show different charge-transfer kinetics that strongly impact on their immunosensitive detection. From the electrochemical data, GCE-PAN-Ab-BSA is more insulating with the presence of BSA, while the GCE-PAN@FePc-Ab-BSA is more conducting with BSA. The CV of the GCE-PAN-Ab-BSA is dominated by radial diffusion process, while that of the GCE-PAN@FePc-Ab-BSA is planar diffusion process. The behaviour of GCE-PAN@FePc-Ab-BSA has been associated with the facile coordination of BSA and FePc that permits co-operative charge-transport of the redox probe, while that of the GCE-PAN-Ab-BSA is related to the interaction-induced PAN-BSA insulating state that suppresses charge-transport. As a consequence of these different interaction processes, GCE-PAN-Ab-BSA immunosensor provides higher electroanalytical performance for the detection of Vibrio cholerae toxin (with sensitivity of 16.12 Ω/log [VCT, g/mL] and limit of detection (LoD) of 3.20 × 10−13 g/mL compared to those of the GCE-PAN@FePc-Ab-BSA (4.16 Ω/log (VCT, g mL−1) and 2.00 × 10−12 g/mL). The study confirms the need for a thorough understanding of the physico-chemistries of the electrode platforms for the construction of immunosensors. Although this work is on immunosensors for cholera infection, it may well apply to other immunosensors.Graphical

Hollow performances quenching label of Au NPs@CoSnO3 nanoboxes-based sandwich photoelectrochemical immunosensor for sensitive CYFRA 21-1 detection

In this work, a fire-new “signal-off” type photoelectrochemical (PEC) immunosensor based on bismuth sulfide/iodine doped bismuth oxychloride (Bi2S3/I:BiOCl) heterostructure as a platform and Au nanoparticles loaded hollow CoSnO3 nanoboxes (Au NPs@CoSnO3) as quenching label was designed, for sensitive detection of CYFRA 21-1. The I:BiOCl with flower-like structure could supply high specific surface area for loading nanometer materials. Then, Bi2S3 was formed in-situ by S2− adsorption on the surface of I:BiOCl by dangling bond of Bi3+, but did not change the flower-like structure of I:BiOCl. Then, n-type Bi2S3 and p-type I:BiOCl heterostructure showed good photoelectric behavior by providing an additional electric field to accelerate electron-hole separation. Furthermore, the production process of the heterostructure was simple, fast, low temperature, and without complex raw materials. The Au NPs@CoSnO3 with good photocatalytic activity could strongly compete with Bi2S3/I:BiOCl for electron donor of ascorbic acid (AA). Meanwhile, the CoSnO3 with hollow structure made the quenching effect more significant by the light-scattering effect that enhanced the light absorption capacity and shorten distance of carrier transport. Under optimal conditions, this proposed strategy displayed the low detection limit of 30 fg/mL, with a high linearity range from 100 fg/mL to 100 ng/mL for tumor markers CYFRA 21-1. Simultaneously, it also exhibited excellent specificity and acceptable stability, which might provide a new perspective for the fabrication of other PEC immunosensors with heterostructure simple synthesis and hollow materials.

Protection, disinfection, and immunization for healthcare during the COVID-19 pandemic: Role of natural and synthetic macromolecules

The world is trying to improve public health while the outbreak of the COVID-19 is at its worst. So far, countless people have died from the COVID-19 disease and it is still a serious threat to human health. Synthetic and natural polymers are unavoidable materials in the healthcare sector. During the COVID-19 outbreak, diverse medical equipment and devices were designed and developed by using these macromolecules for the protection, disinfection, and immunization applications. Synthetic polymers such as polypropylene, polystyrene, poly(lactic acid), poly(ethylene terephthalate), and so forth have been successfully applied for the design and fabrication of diverse face masks, shields, anti-viral coatings, as well as diagnostic kits. Natural polymers having great features such as biodegradability and environmentally friendly are made from algae, plants, and animals. These polymers including sodium alginate, chitosan, cellulose, and gums have been shown a critical role in the fabrication of personal protective equipment, immunosensors, and anti-viral spray for control and fight against COVID-19. Besides, the problem of plastic waste can be solved by replacing them with natural polymers. This mini-review aims to show the application of polymer-based materials during the COVID-19 epidemic.

Electrochemical synthesis of phosphorus and sulfur co-doped graphene quantum dots as efficient electrochemiluminescent immunomarkers for monitoring okadaic acid

In this study, water-dispersed, uniform-sized phosphorus and sulfur co-doped graphene quantum dots (P, S-GQDs) were prepared by the one-step electrolysis of a graphite rod in an alkaline solution containing sodium phytate and sodium sulfide. Compared with GQDs and mono-doped GQDs (P-GQDs and S-GQDs), the P, S-GQDs dramatically improved the electrochemiluminescence (ECL) performance. Therefore, they were used as bright ECL signaling markers through conjugation with a monoclonal antibody against okadaic acid (anti-OA-MAb). Moreover, as an effective matrix for OA immobilization, the carboxylated multiwall carbon nanotubes-poly(diallyldimethylammonium) chloride-Au nanocluster (CMCNT-PDDA-AuNCs) composite promoted electron transfer and enlarged the surface area. Owing to the multiple amplifications, a competitive indirect ECL immunosensor for highly sensitive quantitation of OA has been developed. Under the optimized conditions, the 50% inhibitory concentration (IC50) of the immunosensor was 0.25 ng mL−1, and its linear range was 0.01–20 ng mL−1 with a low detection limit of 0.005 ng mL−1. Finally, the proposed ECL sensor was successfully utilized to detect OA contents in mussel samples. Therefore, this study provides new insights into the designation of ECL luminophores and expands application of co-doped GQDs in fabrication of ECL immunosensors for shellfish toxin determination.

Single-step functionalization of poly-catecholamine nanofilms for ultra-sensitive immunosensing of ubiquitin carboxyl terminal hydrolase-L1 (UCHL-1) in spinal cord injury

Rapid, selective, and ultra-sensitive detection of brain and spinal cord injury markers in bodily fluids is an unmet clinical need. In this work, Polycatecholamine as a rich source of amine moieties was used for single-step fabrication of ultrasensitive immunosensors for the detection of Ubiquitin carboxyl-terminal hydrolase (UCHL-1) biomarker of brain and spinal cord injuries and address the clinical need. The surface of graphene electrodes was modified by electropolymerizing aqueous solution of dopamine (DA) and norepinephrine (NE) monomers for generating polycatecholamines nanofilms on the surface of graphene screen printed electrodes (GSPE) in a single functionalization step. Amine moieties of the polymer allowed immobilization of UCHL-1 antibody on the electrode. The single-step modification of GSPE offered a simple, ultrasensitive, and stable production of immunosensors for the detection of UCHL-1. The operational range of the UCHL-1 immunosensor developed with Polynorepinephrine pNE-modified is 0.1 pg mL−1 – 105 pg mL−1 (LOD: 1.91 pg mL−1), and 1 pg mL−1 – 105 pg mL−1 (LOD: 0.70 pg mL−1) with Polydopamine (pDA) modification, satisfying the clinical range. Both pNE and pDA modified immunosensors, detected UCHL-1 spiked in phosphate buffer saline, artificial cerebrospinal fluid, and serum. Along with the sensitive detections, selective performances were recorded in the above matrices in the presence of interfering neurotransmitters GABA and Glutamate as well as glial fibrillary acidic protein (GFAP). Upon testing clinical samples of spinal cord injury patients and healthy controls, both pNE and pDA immunosensors, delivered a comparable response for UCHL-1, thereby, making immunosensors useful for clinical settings.

Gamma irradiation and microemulsion assisted synthesis of monodisperse flower-like platinum-gold nanoparticles/reduced graphene oxide nanocomposites for ultrasensitive detection of carcinoembryonic antigen

The platinum-gold (PtAu)/reduced graphene oxide (rGO) nanocomposites were obtained via the gamma irradiation assisted by microemulsion while PtAu NPs showed the monodispersed flower-like shape with small-sized (below 15 nm). Gamma irradiation controlled the reduction of graphene oxide and PtAu NPs meanwhile the microemulsion endowed PtAu NPs with porous monodisperse flower-like structure and inhibited the agglomeration of nanoparticles. The size of PtAu NPs was limited by confinement effects of graphene oxide and fragmentation ability of gamma irradiation. An ultra-sensitive, label-free immunosensor was developed on the base of above rGO supported PtAu alloy nanoparticles for the determination of carcinoma embryonic antigen (CEA). The flower-like PtAu/rGO nanocomposites had a higher faradaic current than other nanocomposites, and the obtained PtAu NPs/rGO nanocomposites not only improve the electrocatalytic activity and increase the electrode surface area in nanoscale dimension, but also provide a stable and biocompatible matrix for the convenient conjugation of antibody, thus providing a high-efficiency immunoassay platform. The developed immunosensor showed excellent performance for the detection of CEA with a low detection limit of 7 fg·mL−1 and a wide dynamic range from 10 fg·mL−1 to 1 × 108 fg·mL−1. In addition, the immunosensor system showed high specificity with the interference of ascorbic acid, bovine serum albumin, L-tryptophan and alpha fetal protein. The contribution of this work lies in the research of the synergistic effect of gamma irradiation and microemulsion in the formation of flower-like PtAu NPs/rGO nanoparticles applied in preparation of immunosensor. In view of the versatility of self-assembled nanoparticles, this strategy has great application prospects in fabrication of immunosensors and other biological devices.

Ultrasensitive immunoassay of carcinoma antigen 125 in untreated human plasma samples using gold nanoparticles with flower like morphology: A new platform in early stage diagnosis of ovarian cancer and efficient management

Ovarian cancer, as one of the most life-threatening malignancies among women worldwide, is usually diagnosed at the late stage despite up regulation of molecular markers such as carcinoma antigen 125 (CA 125) at the early stages of the malignancy. CA 125 is the only tumor marker recommended for clinical use in the diagnosis and management of ovarian cancer. The potential role of CA-125 for the early detection of ovarian cancer is controversial and has not yet been adopted for widespread screening efforts in asymptomatic women. Therefore, early detection of CA 125 in human biofluids is highly demanded. In the present study, a novel method was proposed for the fabrication of electrochemical immunosensor based reduced graphene oxide (RGO). Cysteamine capped gold nanoparticle (Cys-AuNPs) were deposited over the surface of ERGO probe using electrophoretic deposition method. These Cys-AuNPs/ERGO probes provide the favorable sites to attach the monoclonal antibody specific to CA 125 antigen. Cyclic voltammetry (CV), and square wave voltammetry (SWV) were applied for the electrochemical recognition of the biolayer. The represented signals demonstrates excellent figure of merits and good capability of the engineered immunosensor towards sensitive detection of CA 125. Quantitative measurements of CA 125 in human plasma samples have been demonstrated, showing the potential of the practical application of this novel immunosensor for the analysis of this biomarker in blood serum samples. This immunosensor has the ability of direct electron transfer as compared to earlier reported electrochemical immunosensors based electrochemical methods. Further, this immunosensor provides a very suitable and convenient alternative to replace the expensive commercially available methods such as immunohistochemistry. The following regression equation between the electrochemical current response and the CA 125 concentration range from 0.1 to 400 U/mL was found. The low limit of quantification for this immunosensor was 0.1 U/mL. To the best of our knowledge, this is the first reported on the direct immobilization of antibody on the surface of Cys-AuNPs/ERGO for fabrication of immunosensors.

Graphene immunosensors for okadaic acid detection in seawater

In this work, we report the fabrication of immunosensors based on field effect transistors with graphene (Gr-FET) for the detection of okadaic acid (OA) in real seawater samples. OA is a marine toxin, and specifically a diarrheic shellfish poison produced by the dinoflagellate species Dinophysis and Prorocentrum. The analytical results obtained with fabricated Gr-FET were compared with those obtained with a traditional methodology (enzyme-linked immunosorbent assay, ELISA) in order to validate the immunosensors for OA detection. Standard solutions of OA with concentrations between 0.05 and 300ngmL−1 were tested to construct the calibration curve and four spiked real seawater samples were used to validate the immunosensors. With the obtained good reproducibility (0.54–2.19%) and repeatability (0.05–2.06%) as well as low limit of detection (0.05ngmL−1) and adequate recovery range (98.2–100.7%), the proposed immunosensors are useful for the detection of OA in real seawater samples and could be advantageously extended for detection of other toxins or agents of marine environmental pollution.

Immunosensor for Pancreatic Cancer Based on Electrospun Nanofibers Coated with Carbon Nanotubes or Gold Nanoparticles.

We report the fabrication of immunosensors based on nanostructured mats of electrospun nanofibers of polyamide 6 and poly(allylamine hydrochloride) coated either with multiwalled carbon nanotubes (MWCNTs) or gold nanoparticles (AuNPs), whose three-dimensional structure was suitable for the immobilization of anti-CA19-9 antibodies to detect the pancreatic cancer biomarker CA19-9. Using impedance spectroscopy, the sensing platform was able to detect CA19-9 with a detection limit of 1.84 and 1.57 U mL–1 for the nanostructured architectures containing MWCNTs and AuNPs, respectively. The high sensitivity achieved can be attributed to the irreversible adsorption between antibodies and antigens, as confirmed with polarization-modulated infrared reflection absorption spectroscopy. The adsorption mechanism was typical Langmuir–Freundlich processes. The high sensitivity and selectivity of the immunosensors were also explored in tests with blood serum from patients with distinct concentrations of CA19-9, for which the impedance spectra data were processed with a multidimensional projection technique. The robustness of the immunosensors in dealing with patient samples without suffering interference from analytes present in biological fluids is promising for a simple, effective diagnosis of pancreatic cancer at early stages.

Deep UV hardening of photoresist for shaping of graphene and lift-off fabrication of back-gated field effect biosensors by ion-milling and sputter deposition

The development of microfabrication techniques compatible with scalable production processes of semiconductor industry is of crucial importance for the technological exploitation of graphene. We report here a novel technique for the photolithographic fabrication of back-gated field-effect transistor immunosensors using chemical vapor deposited (CVD) graphene. The CVD graphene was transferred following polymer assisted method and shaped by ion-milling rather than conventional oxygen plasma etching. A deep UV hardening technique was applied, respectively, before the ion milling shaping of graphene channels and before the deposition of Cr/Au layers for the lift-off fabrication of FET electrodes to ensure the removability of the photoresist. The quality of resulting graphene FET was confirmed by Raman spectroscopy, optical spectroscopy and the detection towards an ultralow concentration of human chorionic gonadotropin. SEM cross-sectional analysis revealed that the deep UV (DUV) hardening process prevents the formation of a post-etching residue shell at the high local temperature during the ion-milling process or sputtering deposition and hence maintain the integrity and significantly improve the removability of the photoresist without the need of using sonication. By using this ion-milling shaped and lift-off fabricated graphene immunosensor, a limit-of-detection of 6 pg/ml has been achieved with a detection range from 1 pg/ml to 100 ng/ml for the label-free detection of hCG.

Amperometric biosensor based on a single antibody of dual function for rapid detection of Streptococcus agalactiae

Pathogenic bacteria are responsible for several diseases in humans and in a variety of hosts. Detection of pathogenic bacteria is imperative to avoid and/or fight their potential harmful effects. This work reports on the first amperometric biosensor for the rapid detection of Streptococcus agalactiae (S. agalactiae). The biosensor relies on a single biotinylated antibody that immobilizes the bacteria on a screen-printed carbon electrode while is further linked to a streptavidin-conjugated HRP reporter. The biotinylated antibody provides selectivity to the biosensor whereas serves as an anchoring point to the reporter for further amplification of the electrochemical signal. The resultant immunosensor is simple, responds rapidly, and allows for the selective and highly sensitive quantification of S. agalactiae cells in a concentration range of 101–107CFUml−1, with a detection limit of 10CFUml−1. The approach not only enables a rapid detection and quantification of S. agalactiae in environmental samples but also opens up new opportunities for the simple fabrication of electrochemical immunosensors for different target pathogens.

Cubic Cu2O nanoframes with a unique edge-truncated structure and a good electrocatalytic activity for immunosensor application

In this work, an ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA). Gold nanoparticles decorated 3-aminopropyltriethoxysilane functionalized graphene sheets (Au@APTES-GS) with a large specific surface area, good biocompatibility and superior electron transfer ability were employed as the matrix. In addition, cubic Cu2O nanoframes with hollow edges were employed as the label for the first time. Scanning electron microscope (SEM) images were used to confirm the nanostructure of Au@APTES-GS and Cu2O. Using square wave voltammetry (SWV) to monitor the electrocatalytic process, the signal amplification mechanism of the matrix and the label were explored successfully. Here we find that the unique edge-truncated structure of Cu2O nanoframes can load with a larger amount of redox mediators, ferrocenecarboxylic acid (Fc-COOH), offering a higher electrochemical signal response. Apart from that, Cu2O nanoframes have a good electrocatalytic activity towards the Fc-COOH and hydrogen peroxide (H2O2), making a contribution to further enhance the sensitivity of the fabricated immunosensor. Under optimal conditions, the proposed immunosensor achieved an ultrasensitive and specific detection of PSA, and displayed acceptable reproducibility, selectivity and stability. This work may provide an effective method for the clinical monitoring of tumor markers and demonstrate the potential application promising of nanoframes in the fabrication of immunosensors.

Analytical Chemistry at the Laboratoire d'Electrochimie Physique et Analytique

The Laboratoire d'Electrochimie Physique et Analytique (LEPA) has moved to the new Energypolis campus in Sion. This laboratory is involved in energy research in particular by studying charge transfer reactions at soft interfaces and developing interfacial redox electrocatalysis, by pioneering the concept of photo-ionic cells and by integrating redox flow batteries for the production of hydrogen at the pilot scale. Nonetheless, this laboratory has a long tradition in analytical chemistry with the development of microfabrication techniques such as laser photo-ablation, screen-printing and more recently inkjet printing for the design and fabrication of biosensors and immunosensors. As shown in the present review, the laboratory has recently pioneered new technologies for electrochemical and mass spectrometry imaging and for the screening of allergy in patients. The role of the laboratory in the Valais landscape will be to foster the collaboration with the HES to develop teaching and research in analytical chemistry as this field is a major source of employment for chemists.

Construction of dentate bonded TiO2-CdSe heterostructures with enhanced photoelectrochemical properties: versatile labels toward photoelectrochemical and electrochemical sensing.

A facile synthetic route for TiO2-CdSe heterostructures was proposed based on dentate binding of TiO2 to carboxyl. Carboxyl functionalized CdSe quantum dots (CF-CdSe QDs) were successfully bonded onto TiO2 nanoparticles (NPs), which could significantly improve the photoelectrochemical (PEC) properties of TiO2 NPs. This is ascribed to the fact that CdSe QDs with a narrow band gap could be stimulated under visible light irradiation, and the energy levels of TiO2 NPs and CF-CdSe QDs are aligned with an electrolyte solution. High resolution transmission electron microscopy images revealed the heterostructures of the TiO2-CdSe composites. Ultraviolet visible spectroscopy, photoluminescence emission spectroscopy and electrochemical impedance spectroscopy analysis exhibited that the prepared TiO2-CdSe heterostructures have improved light absorption, charge separation efficiency and electron transfer ability in the visible light region. TiO2-CdSe heterostructures were used as versatile labels for fabrication of PEC and electrochemical immunosensors, and human immune globulin G (HIgG) was used as a model analyte. The immunosensor showed high sensitivity, a low detection limit and a wide linear range, which could be applied in practical serum sample analysis. The constructed TiO2-CdSe heterostructures would have potential applications in photocatalysis, aptasensors, cytosensors and other areas of nanotechnology.