Nanobody-based electrochemical competitive immunosensor for the detection of AFB1 through AFB1-HCR as signal amplifier

An Electrochemical Immunosensor Based on Chitosan-Graphene Nanosheets for Aflatoxin B1 Detection in Corn

We reported a highly efficient electrochemical immunosensor utilizing chitosan-graphene nanosheets (CS-GNs) nanocomposites for the detection of aflatoxin B1 (AFB1) in corn samples. The CS-GNs nanocomposites, serving as a modifying layer, provide a significant specific surface area and biocompatibility, thereby enhancing both the electron transfer rate and the efficiency of antibody immobilization. The electrochemical characterization was conducted utilizing both differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Moreover, the antibody concentration, pH, antibody immobilization time, and immunoreaction time, were optimized. The results showed that the current change (ΔI) before and after the immunoreaction demonstrated a strong linear relationship (R2=0.990) with the AFB1 concentration, as well as good specificity and stability. The linear range extended from 0.05 to 25 ng/mL, with a detection limit of 0.021 ng/mL (S/N=3). The immunosensor exhibited a recovery rate ranging from 97.3% to 101.4% in corn samples, showing a promising performance using an efficient method, and indicating a remarkable prospect for the detection of fungal toxins in grains.

A nanobody inhibitor of Fascin-1 actin-bundling activity and filopodia formation

Fascin-1-mediated actin-bundling activity is central to the generation of plasma membrane protrusions required for cell migration. Dysregulated formation of cellular protrusions is observed in metastatic cancers, where they are required for increased invasiveness, and is often correlated with increased Fascin-1 abundance. Therefore, there is interest in generating therapeutic Fascin-1 inhibitors. We present the identification of Nb 3E11, a nanobody inhibitor of Fascin-1 actin-bundling activity and filopodia formation. The crystal structure of the Fascin-1/Nb 3E11 complex reveals the structural mechanism of inhibition. Nb 3E11 occludes an actin-binding site on the third β-trefoil domain of Fascin-1 that is currently not targeted by chemical inhibitors. Binding of Nb 3E11 to Fascin-1 induces a conformational change in the adjacent domains to stabilize Fascin-1 in an inhibitory state similar to that adopted in the presence of small-molecule inhibitors. Nb 3E11 could be used as a tool inhibitor molecule to aid in the development of Fascin-1 targeted therapeutics.

Tuning Nanobodies' Bioactivity: Coupling to Ultrasmall Gold Nanoparticles Allows the Intracellular Interference with Survivin

Nanobodies are highly affine binders, often used to track disease-relevant proteins inside cells. However, they often fail to interfere with pathobiological functions, required for their clinical exploitation. Here, a nanobody targeting the disease-relevant apoptosis inhibitor and mitosis regulator Survivin (SuN) is utilized. Survivin's multifaceted functions are regulated by an interplay of dynamic cellular localization, dimerization, and protein-protein interactions. However, as Survivin harbors no classical "druggable" binding pocket, one must aim at blocking extended protein surface areas. Comprehensive experimental evidence demonstrates that intracellular expression of SuN allows to track Survivin at low nanomolar concentrations but failed to inhibit its biological functions. Small angle X-ray scattering of the Survivin-SuN complex locates the proposed interaction interface between the C-terminus and the globular domain, as such not blocking any pivotal interaction. By clicking multiple SuN to ultrasmall (2 nm) gold nanoparticles (SuN-N), not only intracellular uptake is enabled, but additionally, Survivin crosslinking and interference with mitotic progression in living cells are also enabled. In sum, it is demonstrated that coupling of nanobodies to nanosized scaffolds can be universally applicable to improve their function and therapeutic applicability.

In situ synthesized eRAFT polymers for highly sensitive electrochemical determination of AFB1 in foods and herbs

An electrochemical sensor based on environmentally friendly eRAFT polymerization was developed for the detection of aflatoxin B₁ (AFB₁) in food and herbal medicine. Two biological probes, aptamer (Ap) and antibody (Ab), were used to specifically recognize AFB₁, and a large number of ferrocene polymers were grafted on the electrode surface by eRAFT polymerization, which greatly improved the specificity and sensitivity of the sensor. The detection limit of AFB₁ was 37.34 fg/mL. In addition, the recovery rate was 95.69% to 107.65% and the RSD was 0.84% to 4.92% by detecting 9 spiked samples. The delighted reliability of this method was verified by HPLC-FL.

Paper disc interfaced Prussian blue nanocube modified immunodevice for electrochemical detection of diverse biomarker at point of care

The detection of specific biomarkers is used in various phases of the diagnosis of plant and human diseases, from prognosis to monitoring. Herein, we report a Prussian blue nanocube-modified immunodevice interfaced with a paper disc for the detection of plant biomarkers via streptavidin-biotin recognition. The detection ability of the immunodevice was assessed using Potato virus X as a model biomarker and analyzed using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The immunodevice displayed excellent performance for Potato virus X detection with a detection limit of 0.92 nM (3S/N). The selectivity of the fabricated Potato virus X immunodevice was investigated using closely associated antigens, such as potato aucuba mosaic virus, Potato virus Y, and Potato virus A. The Potato virus X immunodevice exhibited ∼ 90 % recovery in spiked complex plant samples with a relative error of ∼ 9 %. Furthermore, the immunodevice was used to screen for Potato virus X in 10 samples from potato tubers and leaves. The paper-disc-interfaced immunodevice was also evaluated by detecting other biomarkers, such as potato aucuba mosaic virus in plant diseases and C-reactive protein in human ones. This immunodevice may allow the on-site monitoring of diverse biomarkers by simplifying the current point of care diagnostic tools.

An electrochemical biosensor for the detection of aflatoxin B1 based on the specific aptamer and HCR biological magnification

Aflatoxin B1 (AFB1) is a highly toxic mycotoxin, which causes severe acute or cumulative poisoning. Therefore, it is important to develop sensitive and selective detection methods for AFB1 for the safety of food and medicinal herbs. Herein, we have developed a "signal-on" electrochemical aptasensor based on the high specificity of the aptamer and hybridization chain reaction (HCR) biological amplification for AFB1 detection. In this work, thiol-modified complementary DNA (cDNA) immobilized on the surface of a gold electrode (GE) served as an initiator DNA. When AFB1 was present, it competed with the cDNA for binding to the aptamers, which resulted in the detaching of aptamers from the cDNA-aptamer duplexes. Then, the single-stranded cDNA acted as an initiator to trigger the HCR signal amplification. Therefore, long double-stranded DNA (dsDNA) products were produced, which could load large amounts of methylene blue (MB) molecules to generate a distinct electrochemical signal. Under the optimized conditions, the proposed electrochemical aptasensor achieved the ultrasensitive detection of AFB1 with a linear detection range of 0.01-100 pg mL^-1, and a limit of detection (LOD) down to 2.84 fg mL^-1. Furthermore, the electrochemical aptasensor was successfully applied for detecting AFB1 in corn and two kinds of traditional Chinese medicine samples, indicating the potential value for AFB1 detection in practical samples.

A Novel Cost-Effective Nanobody against Fumonisin B1 Contaminations: Efficacy Test in Dairy Milk and Chickens

BACKGROUND

Fumonisin B1 (FB1) is a secondary metabolite produced mainly by Fusarium verticillioides or Fusarium proliferatum. It poses a huge threat to the sustainable animal industry and human health as well via food chains (egg, meat and milk). Although E. coli-expressed nanobodies are documented for diagnostic applications, nanobodies remain elusive as FB1 detoxifiers in feed and food.

RESULTS

In the present study, the E. coli-expressed nanobody was assessed to remove FB1 in fresh milk, embryonated eggs and broilers. Firstly, 2 alpacas received intramuscularly FB1-adjuvanted BSA 6 times, and then the variable domain of the heavy-chain antibody (VHH) of fb1 genes were amplified to clone into the pCANTAB 5 E vector in order to generate a VHH-FB1 phage antibody display library, yielding 3.4 × 10¹⁰ capacity with 96.7% positivity. Afterwards, 5 anti-FB1 nanobodies were expressed and identified. Furthermore, maximal 43.2% FB1 was removed from milk by 1:2000 concentration of nanobody 5 (Nb5). Furthermore, SPF-embryonated eggs were inoculated into albumens with nanobody-treated FB1. The Nb5 group yielded an 83.3% hatching rate, higher body weight, lower gizzard ulceration and fewer FB1 residuals. In order to warrant the above results, 50 broilers aged 10 days were received orally with 20 ppm of FB1 for 20 days. At the same time, birds were fed orally with 50 μg of Nb5 or bivalent nanobody 11 (BiNb11). Finally, the Nb5 group showed a higher relative body weight gain and lower gastric ulcerations and fewer inflammations in the thymus and bursa.

CONCLUSIONS

Based on the above evidence, the Nb5 nanobody may be considered as an additional FB1 detoxifier, contributing to FB1 decontamination.

Novel Sensor Approaches of Aflatoxins Determination in Food and Beverage Samples

The rapid quantification of toxins in food and beverage products has become a significant issue in overcoming and preventing many life-threatening diseases. Aflatoxin-contaminated food is one of the reasons for primary liver cancer and induces some tumors and cancer types. Advancements in biosensors technology have brought out different analysis methods. Therefore, the sensing performance has been improved for agricultural and beverage industries or food control processes. Nanomaterials are widely used for the enhancement of sensing performance. The enzymes, molecularly imprinted polymers (MIP), antibodies, and aptamers can be used as biorecognition elements. The transducer part of the biosensor can be selected, such as optical, electrochemical, and mass-based. This review explains the classification of major types of aflatoxins, the importance of nanomaterials, electrochemical, optical biosensors, and QCM and their applications for the determination of aflatoxins.

Detection of Acrylamide in Foodstuffs by Nanobody-Based Immunoassays

Acrylamide is toxic aliphatic amide formed via the Maillard reaction between asparagine and reducing sugars during thermal processing of food. Herein, a specific nanobody termed Nb-7E against the acrylamide derivative xanthyl acrylamide (XAA) was isolated from an immunized phage display library and confirmed to be able to detect acrylamide. First, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was established for acrylamide with a limit of detection (LOD) of 0.089 μg/mL and working range from 0.23 to 5.6 μg/mL. Furthermore, an enhanced electrochemical immunoassay (ECIA) was developed based on the optimized reaction conditions. The LOD was as low as 0.033 μg/mL, threefold improved compared to that of ic-ELISA, and a wider linear detection range from 0.39 to 50.0 μg/mL was achieved. The average recoveries ranged from 88.29 to 111.76% in spiked baked biscuits and potato crisps. Finally, the analytical performance of the ECIA was validated by standard ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS).

Antibody-receptor bioengineering and its implications in designing bioelectronic devices

Antibodies play a crucial role in the defense mechanism countering pathogens or foreign antigens in eukaryotes. Its potential as an analytical and diagnostic tool has been exploited for over a century. It forms immunocomplexes with a specific antigen, which is the basis of immunoassays and aids in developing potent biosensors. Antibody-based sensors allow for the quick and accurate detection of various analytes. Though classical antibodies have prolonged been used as bioreceptors in biosensors fabrication due to their increased fragility, they have been engineered into more stable fragments with increased exposure of their antigen-binding sites in the recent era. In biosensing, the formats constructed by antibody engineering can enhance the signal since the resistance offered by a conventional antibody is much more than these fragments. Hence, signal amplification can be observed when antibody fragments are utilized as bioreceptors instead of full-length antibodies. We present the first systematic review on engineered antibodies as bioreceptors with the description of their engineering methods. The detection of various target analytes, including small molecules, macromolecules, and cells using antibody-based biosensors, has been discussed. A comparison of the classical polyclonal, monoclonal, and engineered antibodies as bioreceptors to construct highly accurate, sensitive, and specific sensors is also discussed.

Nanobody-based label-free photoelectrochemical immunoassay for highly sensitive detection of SARS-CoV-2 spike protein

Until now, COVID-19 caused by SARS-CoV-2 is engulfing the worldwide and still ranging to date, continuing to threaten the public health. The main challenge facing COVID-19 epidemic is short of fast-response and high-efficiency methods to determine SARS-CoV-2 viral pathogens. Herein, a nanobody-based label-free photoelectrochemical (PEC) immunosensor has been fabricated for rapidly detecting SARS-CoV-2 spike protein. As a small-size and high-stability antibody, nanobody was directly and well immobilized with Au nanoparticles and TiO₂ spheres by the interaction. Au deposited TiO₂ nanomaterial possessed 8.5 times photoelectric performance in comparison with TiO₂ in the presence of electron donor owing to surface plasma resonance effect of Au. Based on the steric hindrance effect, this immunoassay platform realized the linear detection from 0.015 to 15000 pg mL⁻¹, and a limit of detection was low as 5 fg mL⁻¹. The label-free PEC immunoassay design provides a new idea for convenient, rapid, and efficient test of SARS-CoV-2 spike protein and broadens further application of nanobody as an identification agent to specific biomarkers.

Application of Nanomaterials for Coping with Mycotoxin Contamination in Food Safety: From Detection to Control

Mycotoxins, which are toxic secondary metabolites produced by fungi, are harmful to humans. Mycotoxin-induced contamination has drawn attention worldwide. Consequently, the development of reliable and sensitive detection methods and high-efficiency control strategies for mycotoxins is important to safeguard food industry safety and public health. With the rapid development of nanotechnology, many novel nanomaterials that provide tremendous opportunities for greatly improving the detection and control performance of mycotoxins because of their unique properties have emerged. This review comprehensively summarizes recent trends in the application of nanomaterials for detecting mycotoxins (fluorescence, colorimetric, surface-enhanced Raman scattering, electrochemical, and point-of-care testing) and controlling mycotoxins (inhibition of fungal growth, mycotoxin absorption, and degradation). These detection methods possess the advantages of high sensitivity and selectivity, operational simplicity, and rapidity. With research attention on the control of mycotoxins and the gradual excavation of the properties of nanomaterials, nanomaterials are also employed for the inhibition of fungal growth, mycotoxin absorption, and mycotoxin degradation, and impressive controlling effects are obtained. This review is expected to provide the readers insight into this state-of-the-art area and a reference to design nanomaterials-based schemes for the detection and control of mycotoxins.

Recent Progress in Rapid Determination of Mycotoxins Based on Emerging Biorecognition Molecules: A Review

Mycotoxins are secondary metabolites produced by fungal species, which pose significant risk to humans and livestock. The mycotoxins which are produced from Aspergillus, Penicillium, and Fusarium are considered most important and therefore regulated in food- and feedstuffs. Analyses are predominantly performed by official laboratory methods in centralized labs by expert technicians. There is an urgent demand for new low-cost, easy-to-use, and portable analytical devices for rapid on-site determination. Most significant advances were realized in the field bioanalytical techniques based on molecular recognition. This review aims to discuss recent progress in the generation of native biomolecules and new bioinspired materials towards mycotoxins for the development of reliable bioreceptor-based analytical methods. After brief presentation of basic knowledge regarding characteristics of most important mycotoxins, the generation, benefits, and limitations of present and emerging biorecognition molecules, such as polyclonal (pAb), monoclonal (mAb), recombinant antibodies (rAb), aptamers, short peptides, and molecularly imprinted polymers (MIPs), are discussed. Hereinafter, the use of binders in different areas of application, including sample preparation, microplate- and tube-based assays, lateral flow devices, and biosensors, is highlighted. Special focus, on a global scale, is placed on commercial availability of single receptor molecules, test-kits, and biosensor platforms using multiplexed bead-based suspension assays and planar biochip arrays. Future outlook is given with special emphasis on new challenges, such as increasing use of rAb based on synthetic and naïve antibody libraries to renounce animal immunization, multiple-analyte test-kits and high-throughput multiplexing, and determination of masked mycotoxins, including stereoisomeric degradation products.

Covalently grafting first-generation PAMAM dendrimers onto MXenes with self-adsorbed AuNPs for use as a functional nanoplatform for highly sensitive electrochemical biosensing of cTnT

2D MXene-Ti₃C₂T_χ has demonstrated promising application prospects in various fields; however, it fails to function properly in biosensor setups due to restacking and anodic oxidation problems. To expand beyond these existing limitations, an effective strategy to for modifying the MXene by covalently grafting first-generation poly(amidoamine) dendrimers onto an MXene in situ (MXene@PAMAM) was reported herein. When used as a conjugated template, the MXene not only preserved the high conductivity but also conferred a specific 2D architecture and large specific surface areas for anchoring PAMAM. The PAMAM, an efficient spacer and stabilizer, simultaneously suppressed the substantial restacking and oxidation of the MXene, which endowed this hybrid with improved electrochemical performance compared to that of the bare MXene in terms of favorable conductivity and stability under anodic potential. Moreover, the massive amino terminals of PAMAM offer abundant active sites for adsorbing Au nanoparticles (AuNPs). The resulting 3D hierarchical nanoarchitecture, AuNPs/MXene@PAMAM, had advanced structural merits that led to its superior electrochemical performance in biosensing. As a proof of concept, this MXene@PAMAM-based nanobiosensing platform was applied to develop an immunosensor for detecting human cardiac troponin T (cTnT). A fast, sensitive, and highly selective response toward the target in the presence of a [Fe(CN)₆]^3-/4- redox marker was realized, ensuring a wide detection of 0.1-1000 ng/mL with an LOD of 0.069 ng/mL. The sensor's signal only decreased by 4.38% after 3 weeks, demonstrating that it exhibited satisfactory stability and better results than previously reported MXene-based biosensors. This work has potential applicability in the bioanalysis of cTnT and other biomarkers and paves a new path for fabricating high-performance MXenes for biomedical applications and electrochemical engineering.

A sensitive electrochemical immunosensing interface for label-free detection of aflatoxin B1 by attachment of nanobody to MWCNTs-COOH@black phosphorene

A label-free electrochemical immunosensor has advantages of real-time and rapid detection, but it is weak in detection of small molecular toxins such as aflatoxin B₁ (AFB₁). The greatest obstacle to achieving this is that small molecules bound to a common immunosensing interface cannot interfere with electron transfer effectively and the detection signal is so weak. Therefore, a sensitive electrochemical immunosensing interface for small molecules is urgently needed. Here, we employed functionalized black phosphorene (BP) as electrode modification materials and anti-AFB₁ nanobody (Nb) as a biorecognition element to construct a very sensitive immunosensing interface towards small molecular AFB₁. The BP functionalized by carboxylic multi-walled carbon nanotubes (MWCNTs-COOH) via P-C bonding behaved with a satisfactory stability and good catalytic performance for the ferricyanide/ferrocyanide probe, while the small-sized Nb showed good compatibility with the functionalized BP and also had less influence on electron transfer than monoclonal antibody (mAb). Expectedly, the as-prepared immunosensing interface was very sensitive to AFB₁ detection by differential pulse voltammetry (DPV) in a redox probe system. Under optimized conditions, a linear range from 1.0 pM to 5.0 nM and an ultralow detection limit of 0.27 pM were obtained. Additionally, the fabricated immunosensor exhibited satisfactory stability, specificity, and reproducibility. The strategy proposed here provides a more reliable reference for label-free sensing of small molecules in food samples.

Carbon-Based Nanocomposite Smart Sensors for the Rapid Detection of Mycotoxins

Carbon-based nanomaterials have become the subject of intensive interest because their intriguing physical and chemical properties are different from those of their bulk counterparts, leading to novel applications in smart sensors. Mycotoxins are secondary metabolites with different structures and toxic effects produced by fungi. Mycotoxins have low molecular weights and highly diverse molecular structures, which can induce a spectrum of biological effects in humans and animals even at low concentrations. A tremendous amount of biosensor platforms based on various carbon nanocomposites have been developed for the determination of mycotoxins. Therefore, the contents of this review are based on a balanced combination of our own studies and selected research studies performed by academic groups worldwide. We first address the vital preparation methods of biorecognition unit (antibodies, aptamers, molecularly imprinted polymers)-functionalized carbon-based nanomaterials for sensing mycotoxins. Then, we summarize various types of smart sensors for the detection of mycotoxins. We expect future research on smart sensors to show a significant impact on the detection of mycotoxins in food products.

An Innovative Nanobody-Based High-Biocompatibility Gold Interdigitated Microelectrode Electrochemical Bioimpedance Sensor for the Ultrasensitive Detection of Difenacoum in Human Serum

Difenacoum (DIF) is one of the most widely used anticoagulant rodenticides. However, accidental or intentional ingestion of DIF seriously threatens humans and other non-target species. Therefore, a rapid and sensitive detection method to quantify DIF is urgently needed. In this study, one anti-DIF nanobody (Nb) was assembled on the surface of a gold interdigitated microelectrode (IDME) using an Au–S bond to fabricate a bioimpedance sensor. To improve the immobilization amount of Nbs on the electrode, a polycrystalline gold IDME was prepared to provide a larger surface and better biocompatibility. Thus, a novel and ultrasensitive bioimpedance sensor based on electrochemical impedance spectroscopy (EIS) was designed for the determination of DIF, and it displayed good reproducibility and stability in human serum. The proposed bioimpedance sensor displayed a wide working range, between 0.1–1000 pg/mL, with a limit of detection (LOD) of 0.1 pg/mL of DIF. This method exhibited excellent performance, good sensitivity, and reproducibility and achieved the highest sensitivity of all currently existing methods used to quantify DIF. The highly sensitive DIF detection of this proposed bioimpedance sensor indicates its potential as an efficacious approach for DIF monitoring in human serum with high accuracy and precision.

Recent Achievements in Electrochemical and Surface Plasmon Resonance Aptasensors for Mycotoxins Detection

Mycotoxins are secondary metabolites of fungi that contaminate agriculture products. Their release in the environment can cause severe damage to human health. Aptasensors are compact analytical devices that are intended for the fast and reliable detection of various species able to specifically interact with aptamers attached to the transducer surface. In this review, assembly of electrochemical and surface plasmon resonance (SPR) aptasensors are considered with emphasis on the mechanism of signal generation. Moreover, the properties of mycotoxins and the aptamers selected for their recognition are briefly considered. The analytical performance of biosensors developed within last three years makes it possible to determine mycotoxin residues in water and agriculture/food products on the levels below their maximal admissible concentrations. Requirements for the development of sample treatment and future trends in aptasensors are also discussed.

Interaction between the functionalized probes: The depressed efficiency of dual-amplification strategy on ratiometric electrochemical aptasensor for aflatoxin B1

Signal amplification is one of the most effective ways to develop the high-performance electrochemical sensors. However, it can be more complicated for ratiometric detections. Herein, a ratiometric electrochemical aptasensor for aflatoxin B1 (AFB1) was proposed by taking advantage of a dual-amplification strategy by coupling of DNA walker (DW) with hybridization chain reaction (HCR). The special binding of AFB1 with ferrocene (Fc)-labelled aptamer triggers DW on hairpin DNA (hDNA) tracks to produce abundant double-stranded DNA (dsDNA). HCR-based strand amplification occurs on these dsDNA to absorb more methylene blue (MB). Then current ratio of MB (I_MB) and Fc (I_Fc) is designed as a yardstick to detect AFB1. Our experiments reveal that the interaction between Fc and MB (i.e., steric hindrance, electron mediator) varies. In addition to steric hindrance, the presence of MB also acts as electron mediator, thereby facilitating the electron transfer between Fc and electrode. Such combined effect consequently depresses the efficiency of dual-amplification strategy to improve the detection. The developed ratiometric electrochemical aptasensor allows the accurate detection of AFB1 in the 0.003-3 pg mL^-1 range. Our work has shed light on the amplification strategy for ratiometric sensing, and provided a new route in integrating different amplification strategies.

Nanobodies targeting immune checkpoint molecules for tumor immunotherapy and immunoimaging (Review)

The immune checkpoint blockade is an effective strategy to enhance the anti-tumor T cell effector activity, thus becoming one of the most promising immunotherapeutic strategies in the history of cancer treatment. Several immune checkpoint inhibitor have been approved by the FDA, such as anti-CTLA-4, anti-PD-1, anti-PD-L1 monoclonal antibodies. Most tumor patients benefitted from these antibodies, but some of the patients did not respond to them. To increase the effectiveness of immunotherapy, including immune checkpoint blockade therapies, miniaturization of antibodies has been introduced. A single-domain antibody, also known as nanobody, is an attractive reagent for immunotherapy and immunoimaging thanks to its unique structural characteristic consisting of a variable region of a single heavy chain antibody. This structure confers to the nanobody a light molecular weight, making it smaller than conventional antibodies, although remaining able to bind to a specific antigen. Therefore, this review summarizes the production of nanobodies targeting immune checkpoint molecules and the application of nanobodies targeting immune checkpoint molecules in immunotherapy and immunoimaging.