Electrochemical detection of proteins using nanoparticles: applications to diagnostics

Metal-organic frameworks for pharmaceutical and biomedical applications

Metal-organic framework (MOF) materials provide unprecedented opportunities for evaluating valuable compounds for various medical applications. MOFs merged with biomolecules, used as novel biomaterials, have become particularly useful in biological environments. Bio-MOFs can be promising materials in the global to avoid utilization above toxicological substances. Bio-MOFs with crystallin and porosity nature offer flexible structure via bio-linker and metal node variation, which improves their wide applicability in medical science.

Enhancing the electrocatalytic activity of palladium nanocluster tags by selective introduction of gold atoms: Application for a wound infection biomarker detection

In this work, an unprecedented study exploring the role that slight changes into the Pd/Au proportion have in the electrocatalytic activity of bimetallic Pd-AuNPs toward the oxygen reduction reaction (ORR) is conducted. In particular, a careful control of the amount of Au atoms introduced in the cluster and the evaluation of the optimum Pd:Au ratio for getting the maximum catalytic activity is performed for the first time. First, PdNPs are synthesized by alcohol reduction in the presence of polyvinylpyrrolidone, and gold atoms are selectively introduced on vertex or corner positions of the cluster in different amounts following a galvanic substitution procedure. Average elemental analysis done relying on EDX spectroscopy allows to evaluate the Pd:Au ratio in the Pd-AuNPs obtained. Lineal sweep voltammetry and chronoamperometry are used for the evaluation of the Pd-AuNPs electrocatalytic activity toward ORR at a neutral pH compared to PdNPs and AuNPs alone. Our results indicate that, the synergy between both metals is strongly enhanced when the amount of gold is controlled and occupies the more reactive positions of the cluster, reaching a maximum activity for the NPs containing a 30% of gold, while an excess of this metal leads to a decrease in such activity, as a shelter of the PdNPs is achieved. Chronoamperometric analysis allows the quantification of the optimal Pd-AuNPs at over 6 × 10⁹ NPs/mL levels. Such optimal Pd-AuNPs were used as tags, taking advantage of the bio-functionalities of gold present in the cluster, in a proof-of-concept electrochemical immunosensor for the detection of hyaluronidase wound infection biomarker, using magnetic beads as platforms. Hyaluronidase was detected at levels as low as 50 ng/mL (0.02 U/mL; 437 U/mg) with good reproducibility (RSD below 8%) and selectivity (evaluated against bovine serum albumin, immunoglobulin G and lysozyme). The low matrix effects inherent to the use of magnetic bead platforms allowed us to discriminate between wound exudates with both sterile and infected ulcers without sample pre-treatment. This novel electrocatalytic immunoassay has the advantage, over common methods for NP tags electrochemical detection, of the signal generation in the same neutral medium where the immunoassay takes place (10 mM PBS pH 7.4), avoiding the use of additional and hazardous reagents, bringing it closer to their use as point-of-care devices. Overall, our findings may be of great interest not only for biosensing, but also for applications such as energy converting on fuel cells, in which the ORR has a pivotal role.

A Comprehensive Review of Metal-Organic Framework: Synthesis, Characterization, and Investigation of Their Application in Electrochemical Biosensors for Biomedical Analysis

Many studies have addressed electrochemical biosensors because of their simple synthesis process, adjustability, simplification, manipulation of materials' compositions and features, and wide ranges of detection of different kinds of biomedical analytes. Performant electrochemical biosensors can be achieved by selecting materials that enable faster electron transfer, larger surface areas, very good electrocatalytic activities, and numerous sites for bioconjugation. Several studies have been conducted on the metal-organic frameworks (MOFs) as electrode modifiers for electrochemical biosensing applications because of their respective acceptable properties and effectiveness. Nonetheless, researchers face challenges in designing and preparing MOFs that exhibit higher stability, sensitivity, and selectivity to detect biomedical analytes. The present review explains the synthesis and description of MOFs, and their relative uses as biosensors in the healthcare sector by dealing with the biosensors for drugs, biomolecules, as well as biomarkers with smaller molecular weight, proteins, and infectious disease.

Gold nanoparticles-based assays for biodetection in urine

Urine is a biofluid easy to collect through a non-invasive technique that allows collecting a large volume of sample. The use of urine for disease diagnosis is not yet well explored. However, it has gained attention over the last three years. It has been applied in the diagnosis of several illnesses such as kidney disease, bladder cancer, prostate cancer and cardiovascular diseases. In the last decade, gold nanoparticles (Au NPs) have attracted attention in biosensors' development for the diagnosis of diseases due to their electrical and optical properties, ability to conjugate with biomolecules, high sensitivity, and selectivity. Therefore, this article aims to present a comprehensive view of state of the art on the advances made in the quantification of analytes in urinary samples using AuNPs based assays, with a focus on protein analysis. The type of diagnosis methods, the Au NPs synthesis approaches and the strategies for surface modification aiming at selectivity towards the different targets are highlighted.

Precision medicine, bioanalytics and nanomaterials: toward a new generation of personalized portable diagnostics

The customization of disease treatment focused on genetic, environmental and lifestyle factors of individual patients, including tailored medical decisions and treatments, is identified as precision medicine. This approach involves the combination of various aspects such as the collection and processing of a large amount of data, the selection of optimized and personalized drug dosage for each patient and the development of selective and reliable analytical tools for the monitoring of clinical, genetic and environmental parameters. In this context, miniaturized, compact and ultrasensitive bioanalytical devices play a crucial role for achieving the goals of personalized medicine. In this review, the latest analytical technologies suitable for providing portable and easy-to-use diagnostic tools in clinical settings will be discussed, highlighting new opportunities arising from nanotechnologies, offering peculiar perspectives and opportunities for precision medicine.

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors

Electrochemical immunosensors, EIs, are systems that combine the analytical power of electrochemical techniques and the high selectivity and specificity of antibodies in a solid phase immunoassay for target analyte. In EIs, the most used transducer platforms are screen printed electrodes, SPEs. Some characteristics of EIs are their low cost, portability for point of care testing (POCT) applications, high specificity and selectivity to the target molecule, low sample and reagent consumption and easy to use. Despite all these attractive features, still exist one to cover and it is the enhancement of the sensitivity of the EIs. In this review, an approach to understand how this can be achieved is presented. First, it is necessary to comprise thoroughly all the complex phenomena that happen simultaneously in the protein-surface interface when adsorption of the protein occurs. Physicochemical properties of the protein and the surface as well as the adsorption phenomena influence the sensitivity of the EIs. From this point, some strategies to suppress non-specific binding, NSB, of proteins onto electrode surfaces in order to improve the sensitivity of EIs are mentioned.

Nanobiosensors in diagnostics

Medical diagnosis has been greatly improved thanks to the development of new techniques capable of performing very sensitive detection and quantifying certain parameters. These parameters can be correlated with the presence of specific molecules and their quantity. Unfortunately, these techniques are demanding, expensive, and often complicated. On the other side, progress in other fields of science and technology has contributed to the rapid growth of nanotechnology. Although being an emerging discipline, nanotechnology has raised huge interest and expectations. Most of the enthusiasm comes from new possibilities and properties of nanomaterials. Biosensors (simple, robust, sensitive, cost-effective) combined with nanomaterials, also called nanobiosensors, are serving as bridge between advanced detection/diagnostics and daily/routine tests. Here we review some of the latest applications of nanobiosensors in diagnostics field.

Detection of parathyroid hormone-like hormone in cancer cell cultures by gold nanoparticle-based lateral flow immunoassays

Parathyroid hormone-like hormone (PTHLH) exerts relevant roles in progression and dissemination of several tumors. However, factors influencing its production and secretion have not been fully characterized. The main limitation is the lack of specific, sensitive and widely available techniques to detect and quantify PTHLH. We have developed a lateral flow immunoassay using gold nanoparticles label for the fast and easy detection of PTHLH in lysates and culture media of three human cell lines (HaCaT, LA-N-1, SK-N-AS). Levels in culture media and lysates ranged from 11 to 20 ng/mL and 0.66 to 0.87 μg/mL respectively. Results for HaCaT are in agreement to the previously reported, whereas LA-N-1 and SK-N-AS have been evaluated for the first time. The system also exhibits good performance in human serum samples. This methodology represents a helpful tool for future in vitro and in vivo studies of mechanisms involved in PTHLH production as well as for diagnostics. From the Clinical Editor: Parathyroid Hormone-like Hormone (PTHLH) is known to be secreted by some tumors. However, the detection of this peptide remains difficult. The authors here described their technique of using gold nanoparticles as label for the detection of PTHLH by Lateral-flow immunoassays (LFIAs). The positive results may also point a way to using the same technique for the rapid determination of other relevant cancer proteins.

Alzheimer's disease biomarkers detection in human samples by efficient capturing through porous magnetic microspheres and labelling with electrocatalytic gold nanoparticles

A nanobiosensor based on the use of porous magnetic microspheres (PMM) as efficient capturing/pre-concentrating platform is presented for detection of Alzheimer's disease (AD) biomarkers. These PMMs prepared by a multistep swelling polymerization combined with iron oxide precipitation afford carboxyl functional groups suitable for immobilization of antibodies on the particle surface allowing an enhanced efficiency in the capturing of AD biomarkers from human serum samples. The AD biomarkers signaling is produced by gold nanoparticle (AuNP) tags monitored through their electrocatalytic effect towards hydrogen evolution reaction (HER). Novel properties of PMMs in terms of high functionality and high active area available for enhanced catalytic activity of the captured AuNPs electrocatalytic tags are exploited for the first time. A thorough characterization by scanning transmission electron microscope in high angle annular dark field mode (STEM-HAADF) demonstrates the enhanced ability of PMMs to capture a higher quantity of analyte and consequently of electrocatalytic label, when compared with commercially available microspheres. The optimized and characterized PMMs are also applied for the first time for the detection of beta amyloid and ApoE at clinical relevant levels in cerebrospinal fluid (CSF), serum and plasma samples of patients suffering from AD.

Ultrasensitive and real-time detection of proteins in blood using a potentiometric carbon-nanotube aptasensor

Potentiometric sensing represents the preferred technique in many routine measurements of pH and ions. Unfortunately, the simplicity of the technique has not been exploited so far in high throughput biomolecular sensing. In this work, we demonstrate the capabilities of the hybrid functional material carbon nanotubes/aptamer for the creation of a new generation of nuclease-resistant aptasensors using the potentiometric transduction capabilities of single-walled carbon nanotubes in combination with the recognition capabilities of a protein-specific RNA aptamer. The aptasensor was used to detect and identify disease-related proteins at attomolar concentration values in a rapid and non-expensive way. The variable surface glycoprotein from African Trypanosomes was chosen as an ideal model system for a pathogenic exoantigen protein in a clinical sample. Variations in the electromotive force are achieved in real-time upon the direct addition of diluted real blood samples containing the target protein thus eliminating the need of preliminary matrix removal. This work would open the door to real-time diagnostic assays for a wide range of diseases, but also to the rapid molecular detection of several proteins in truly customizable protein biosensing platforms.

Simple monitoring of cancer cells using nanoparticles

Here we present a new strategy for a simple and fast detection of cancer circulating cells (CTCs) using nanoparticles. The human colon adenocarcinoma cell line (Caco2) was chosen as a model CTC. Similarly to other adenocarcinomas, colon adenocarcinoma cells have a strong expression of EpCAM, and for this reason this glycoprotein was used as the capture target. We combine the capturing capability of anti-EpCAM functionalized magnetic beads (MBs) and the specific labeling through antibody-modified gold nanoparticles (AuNPs), with the sensitivity of the AuNPs-electrocatalyzed hydrogen evolution reaction (HER) detection technique. The fully optimized process was used for the electrochemical detection of Caco2 cells in the presence of monocytes (THP-1), other circulating cells that could interfere in real blood samples. Therefore we obtained a novel and simple in situ-like sensing format that we applied for the rapid quantification of AuNPs-labeled CTCs in the presence of other human cells.

Magnetic particles in ultrasensitive biomarker protein measurements for cancer detection and monitoring

IMPORTANCE OF THE FIELD: Devices for the reliable detection of panels of biomarker proteins facilitated by magnetic bead-based technologies have the potential to greatly improve future cancer diagnostics. The reason for this review is to highlight promising research on emerging procedures for protein capture, transport and detection featuring magnetic particles. AREAS COVERED IN THIS REVIEW: The review covers applications of magnetic particles in protein immunoassays in emerging research and commercial methods, and stresses multiplexed protein assays for reliable future cancer diagnostics. Research literature over the past dozen years has been surveyed and specific examples are presented in detail. EXPERT OPINION: Magnetic particles are important components of emerging protein detection systems. They need to be integrated into simple inexpensive systems for accurate, sensitive detection of fully validated panels of biomarker proteins to be widely useful in clinical cancer diagnostics.

A nanochannel/nanoparticle-based filtering and sensing platform for direct detection of a cancer biomarker in blood

A rapid nanochannel-based immunoassay capable of the filtering and subsequent detection of proteins in whole blood without any sample preparation is described. This is accomplished by using a nanoporous/nanochannel membrane modified with antibodies, the conductivity of which toward a redox indicator is tuned by primary and secondary immunoreactions with proteins and gold nanoparticles. This interesting nanopore blockage by gold nanoparticles is enhanced by silver deposition that further decreases the diffusion of the signaling indicator through the nanochannel. The efficiency of the nanochannels to act as immunoreaction platforms including the use of nanoparticles is also monitored by microscopic techniques. Successful detection of immunoglobulins including a cancer biomarker is achieved in buffer as well as in whole blood. This system constitutes an efficient immunoassay capable of detecting up to 52 U mL(-1) of CA15-3. The developed nanochannel/nanoparticle-based device can be used for several other proteins and extended also to DNA detection with interest not only for diagnostics but also environmental monitoring, food analysis, safety, and security applications.