On-line immunoaffinity capillary electrophoresis based on magnetic beads for the determination of alpha-1 acid glycoprotein isoforms profile to facilitate its use as biomarker

The Use of Extraction on C18-Silica-Modified Magnetic Nanoparticles for the Determination of Ciprofloxacin and Ofloxacin in Meat Tissues

A simple, fast, and low-cost method of extraction using magnetic nanoparticles was developed for sample preparation in the determination of ciprofloxacin and ofloxacin in meat tissues with the use of capillary electrophoresis. This study is the first utilization of silica-coated magnetic nanoparticles with attached C18 chains to extract fluoroquinolones from meat tissues. This method is therefore characterized by a very simple sample preparation procedure, but on the other hand, by satisfactory precision and accuracy. Magnetic nanoparticles with an appropriately modified surface were placed in an Eppendorf tube, then conditioned with methanol, next rinsed with water and, finally, a homogenized tissue sample was added. At the neutral pH of the sample solution, these compounds do not have a charge and are able to adsorb on the modified particles. After extraction, the nanoparticles were dried and, then, desorption of analytes was conducted with the use of a mixture of 0.1 mol/L HCl and acetonitrile (1:1). This approach made it possible to purify the sample matrix and to obtain satisfactory LOQ levels for the method using the CE technique with UV-Vis detection. In this method, the LOD and LOQ values for both analytes were 0.04 nmol/g tissue and 0.15 nmol/g tissue, respectively. The calibration curves were linear in the entire concentration range, and the accuracy and the recovery of the method were at the satisfactory levels. The square value of the linear correlation coefficients (R2) for Cpx and Ofx were 0.9995 and 0.9992, respectively. The precision value of the method was within the range of 3-11% and accuracy was in the range of 93-110%.

Advancements in portable instruments based on affinity-capture-migration and affinity-capture-separation for use in clinical testing and life science applications

The shift from testing at centralized diagnostic laboratories to remote locations is being driven by the development of point-of-care (POC) instruments and represents a transformative moment in medicine. POC instruments address the need for rapid results that can inform faster therapeutic decisions and interventions. These instruments are especially valuable in the field, such as in an ambulance, or in remote and rural locations. The development of telehealth, enabled by advancements in digital technologies like smartphones and cloud computing, is also aiding in this evolution, allowing medical professionals to provide care remotely, potentially reducing healthcare costs and improving patient longevity. One notable POC device is the lateral flow immunoassay (LFIA), which played a major role in addressing the COVID-19 pandemic due to its ease of use, rapid analysis time, and low cost. However, LFIA tests exhibit relatively low analytical sensitivity and provide semi-quantitative information, indicating either a positive, negative, or inconclusive result, which can be attributed to its one-dimensional format. Immunoaffinity capillary electrophoresis (IACE), on the other hand, offers a two-dimensional format that includes an affinity-capture step of one or more matrix constituents followed by release and electrophoretic separation. The method provides greater analytical sensitivity, and quantitative information, thereby reducing the rate of false positives, false negatives, and inconclusive results. Combining LFIA and IACE technologies can thus provide an effective and economical solution for screening, confirming results, and monitoring patient progress, representing a key strategy in advancing diagnostics in healthcare.

CE-MS for Proteomics and Intact Protein Analysis

This chapter aims to explore various parameters involved in achieving high-end capillary electrophoresis hyphenated to mass spectrometry (CE-MS) analysis of proteins, peptides, and their posttranslational modifications. The structure of the topics discussed in this book chapter is conveniently mapped on the scheme of the CE-MS system itself, starting from sample preconcentration and injection techniques and finishing with mass analyzer considerations. After going through the technical considerations, a variety of relevant applications for this analytical approach are presented, including posttranslational modifications analysis, clinical biomarker discovery, and its growing use in the biotechnological industry.

Glycoprotein analysis using lectin microcolumns and capillary electrophoresis: Characterization of alpha1-acid glycoprotein by combined separation methods

Separations based on combinations of 2.1 mm I.D. high-performance affinity microcolumns and capillary electrophoresis were developed and used to characterize the glycoforms of an intact glycoprotein. Human alpha₁-acid glycoprotein (AGP) was used as a model analyte due to its heterogeneous glycosylation resulting from variations in its degree of branching, fucosylation, and number of sialic acids. Three separation formats were examined based on microcolumns that contained the lectins concanavalin A (Con A) or Aleuria aurantia lectin (AAL). These microcolumns were used with one another or in combination with capillary electrophoresis. N-Glycan analysis of the non-retained and retained AGP fractions was carried out by using PNGase F digestion and nanoflow electrospray ionization mass spectrometry. Con A microcolumns were found to selectively enrich AGP that contained bi-antennary N-glycans, while AAL microcolumns retained AGP with fucose-containing N-glycans. Results from these separation methods indicated that fucosylation of the N-linked glycans was more abundant when a high degree of branching was present in AGP. Sialic acid residues were more abundant when higher degrees of branching and more fucose residues were present in AGP. The separation and analysis methods that were developed could be used with relatively small amounts of AGP and can be adapted for use with other intact glycoproteins.

A Two-Dimensional Affinity Capture and Separation Mini-Platform for the Isolation, Enrichment, and Quantification of Biomarkers and Its Potential Use for Liquid Biopsy

Biomarker detection for disease diagnosis, prognosis, and therapeutic response is becoming increasingly reliable and accessible. Particularly, the identification of circulating cell-free chemical and biochemical substances, cellular and subcellular entities, and extracellular vesicles has demonstrated promising applications in understanding the physiologic and pathologic conditions of an individual. Traditionally, tissue biopsy has been the gold standard for the diagnosis of many diseases, especially cancer. More recently, liquid biopsy for biomarker detection has emerged as a non-invasive or minimally invasive and less costly method for diagnosis of both cancerous and non-cancerous diseases, while also offering information on the progression or improvement of disease. Unfortunately, the standardization of analytical methods to isolate and quantify circulating cells and extracellular vesicles, as well as their extracted biochemical constituents, is still cumbersome, time-consuming, and expensive. To address these limitations, we have developed a prototype of a portable, miniaturized instrument that uses immunoaffinity capillary electrophoresis (IACE) to isolate, concentrate, and analyze cell-free biomarkers and/or tissue or cell extracts present in biological fluids. Isolation and concentration of analytes is accomplished through binding to one or more biorecognition affinity ligands immobilized to a solid support, while separation and analysis are achieved by high-resolution capillary electrophoresis (CE) coupled to one or more detectors. When compared to other existing methods, the process of this affinity capture, enrichment, release, and separation of one or a panel of biomarkers can be carried out on-line with the advantages of being rapid, automated, and cost-effective. Additionally, it has the potential to demonstrate high analytical sensitivity, specificity, and selectivity. As the potential of liquid biopsy grows, so too does the demand for technical advances. In this review, we therefore discuss applications and limitations of liquid biopsy and hope to introduce the idea that our affinity capture-separation device could be used as a form of point-of-care (POC) diagnostic technology to isolate, concentrate, and analyze circulating cells, extracellular vesicles, and viruses.

Capillary electrophoresis-based immunoassay and aptamer assay: A review

Over the last two decades, the group of techniques called affinity probe CE has been widely used for the detection and the determination of several types of biomolecules with high sensitivity. These techniques combine the low sample consumption and high separation power of CE with the selectivity of the probe to the target molecule. The assays can be defined according to the type of probe used: CE immunoassays, with an antibody as the probe, or aptamer-based CE, with an aptamer as the probe. Immunoassays are generally divided into homogeneous and heterogeneous groups, and homogeneous variant can be further performed in competitive or noncompetitive formats. Interacting partners are free in solution at homogeneous assay, as opposed to heterogeneous analyses, where one of them is immobilized onto a solid support. Highly sensitive fluorescence, chemiluminescence or electrochemical detections were typically used in this type of study. The use of the aptamers as probes has several advantages over antibodies such as shorter generation time, higher thermal stability, lower price, and lower variability. The aptamer-based CE technique was in practice utilized for the determination of proteins in biological fluids and environmentally or clinically important small molecules. Both techniques were also transferred to microchip. This review is focused on theoretical principles of these techniques and a summary of their applications in research.

Clinical and pharmaceutical applications of affinity ligands in capillary electrophoresis: A review

Affinity capillary electrophoresis (ACE) is a separation technique that combines a biologically-related binding agent with the separating power and efficiency of capillary electrophoresis. This review will examine several classes of binding agents that have been used in ACE and applications that have been described for the resulting methods in clinical or pharmaceutical analysis. Binding agents that will be considered are antibodies, aptamers, lectins, serum proteins, carbohydrates, and enzymes. This review will also describe the various formats in which each type of binding agent has been used in CE, including both homogeneous and heterogeneous methods. Specific areas of applications that will be considered are CE-based immunoassays, glycoprotein/glycan separations, chiral separations, and biointeraction studies. The general principles and formats of ACE for each of these applications will be examined, along with the potential advantages or limitations of these methods.

Application of Capillary Electrophoresis with Laser-Induced Fluorescence to Immunoassays and Enzyme Assays

Capillary electrophoresis using laser-induced fluorescence detection (CE-LIF) is one of the most sensitive separation tools among electrical separation methods. The use of CE-LIF in immunoassays and enzyme assays has gained a reputation in recent years for its high detection sensitivity, short analysis time, and accurate quantification. Immunoassays are bioassay platforms that rely on binding reactions between an antigen (analyte) and a specific antibody. Enzyme assays measure enzymatic activity through quantitative analysis of substrates and products by the reaction of enzymes in purified enzyme or cell systems. These two category analyses play an important role in the context of biopharmaceutical analysis, clinical therapy, drug discovery, and diagnosis analysis. This review discusses the expanding portfolio of immune and enzyme assays using CE-LIF and focuses on the advantages and disadvantages of these methods over the ten years of existing technology since 2008.

A critical retrospective and prospective review of designs and materials in in-line solid-phase extraction capillary electrophoresis

Several strategies have been developed to decrease the concentration limits of detection (LODs) in capillary electrophoresis (CE). Nowadays, chromatographic-based preconcentration using a microcartridge integrated in the separation capillary for in-line solid-phase extraction capillary electrophoresis (SPE-CE) is one of the best alternatives for high throughput and reproducible sample clean-up and analyte preconcentration. This review covers different designs (geometrical configurations, with frits or fritless, capillary types, compatibility with commercial instrumentation, etc.) and materials (sorbents, supports, affinity ligands, etc.) applied for almost 30 years to prepare in-line SPE-CE microcartridges (i.e. analyte concentrators), with emphasis on the conventional unidirectional configuration in capillary format. Advantages, disadvantages and future perspectives are analyzed in detail to provide the reader a wide overview about the great potential of this technique to enhance sensitivity and address trace analysis.

On-Line Immunoaffinity Solid-Phase Extraction Capillary Electrophoresis-Mass Spectrometry for the Analysis of Serum Transthyretin

The analysis of low abundant proteins in biological fluids by capillary electrophoresis (CE) is particularly problematic due to the typically poor concentration limits of detection of microscale separation techniques. Another important issue is sample matrix complexity that requires an appropriate cleanup. Here, we describe an on-line immunoaffinity solid-phase extraction capillary electrophoresis-mass spectrometry (IA-SPE-CE-MS) method for the immunoextraction, preconcentration, separation, detection, and characterization of serum transthyretin (TTR). TTR is a protein biomarker related to diverse types of amyloidosis, such as familial amyloidotic polyneuropathy type I (FAP-I), which is the most common hereditary systemic amyloidosis.

Sensitivity Enhancement in Capillary Electrophoresis Using Magnetic Particles as Solid-Phase Extraction Sorbents for the Determination of Drugs of Abuse in Urine

Over the last few years, different types of magnetic particles have been investigated and successfully used in sample preparation, of which iron oxides are the most popular, due to their low price and low toxicity. For analytical purposes, these particles have always been modified and functionalized with different materials to improve their stability and introduce new surface properties. Here we describe the preparation of silica-coated iron oxide particles functionalized with C₁₈ and their application as solid-phase extraction sorbents coupled in-line with capillary electrophoresis for determining drugs of abuse in human urine.

Glycoform analysis of alpha1-acid glycoprotein based on capillary electrophoresis and electrophoretic injection

A method based on capillary electrophoresis (CE) with electrophoretic injection and absorbance detection was developed for the direct analysis of AGP glycoforms in human serum. Electrophoretic injection of AGP was performed in the reversed-polarity mode of CE with a capillary coated with poly(ethylene oxide) and that had minimal electroosmotic flow. This situation created an essentially stationary interface between the sample and running buffer during injection and sample stacking. This approach allowed an 11,000-fold increase in sample loading for a 5min injection versus hydrodynamic injection and without introducing any significant levels of extra band-broadening. This method was used with sample pretreatment methods based on acid precipitation and desalting to examine AGP glycoforms in only 65μL of serum. A limit of detection of 2.1-11.3nM was obtained for the major AGP glycoform bands in serum, and the sample pretreatment method gave a recovery of 72.3-80.9% for these glycoforms. The precision for the migration times was ±0.08-0.13% and the precision for the peak areas was ±0.34-1.18% when using serum samples and an internal standard. This method was used for both normal pooled serum and serum from individuals with systemic lupus erythematosus. Results were obtained in a separation time of 25min and allowed the comparison of up to eleven glycoform bands in these samples. A similar approach may be useful in examining additional glycoproteins in serum or other types of biological samples.

Glycoform analysis of alpha1-acid glycoprotein by capillary electrophoresis

A relatively fast and reproducible CE separation was developed for the glycoform analysis of α1-acid glycoprotein (AGP). Factors that were considered included the pH for this separation and various techniques for coating the capillary and/or to minimize electroosmotic flow and protein adsorption. Optimum resolution of the AGP glycoforms was obtained at pH 4.2 with a running buffer containing 0.1% Brij 35 and by using static and dynamic coatings of PEO on the capillary. These conditions made it possible to separate nine AGP glycoform bands in about 20min. The limit of detection (based on absorbance measurements) ranged from 0.09 to 0.38μM for these AGP glycoform bands, and the linear range extended up to a total AGP concentration of at least 240μM. The migration times for the glycoform bands had typical within-day and day-to-day precisions of ±0.16-0.23% or less, respectively, on a single treated capillary and the variation between capillaries was ±0.56% or less. A charge ladder approach was employed to examine the mass or charge differences in the glycoforms that made up these bands, giving a good fit to a model in which the neighboring bands differed by one charge (e.g., from a sialic acid residue) and had an average mass difference of approximately 0.7-0.9kDa. The approaches used to develop this separation method are not limited to AGP but could be extended to the analysis of other glycoproteins by CE.

Recent applications of CE- and HPLC-MS in the analysis of human fluids

The present review intends to cover the literature on the use of CE-/LC-MS for the analysis of human fluids, from 2010 until present. It has been planned to provide an overview of the most recent practical applications of these techniques to less extensively used human body fluids, including, bronchoalveolar lavage fluid, synovial fluid, nipple aspirate, tear fluid, breast fluid, amniotic fluid, and cerumen. Potential pitfalls related to fluid collection and sample preparation, with particular attention to sample clean-up procedures, and methods of analysis, from the research laboratory to a clinical setting will also be addressed. While being apparent that proteomics/metabolomics represent the most prominent approaches for global identification/quantification of putative biomarkers for a variety of human diseases, evidence is also provided of the suitability of these sophisticated techniques for the detection of heterogeneous components carried by these fluids.

Utilization of magnetic nanobeads for analyzing haptoglobin in human plasma as a marker of Alzheimer's disease by capillary electrophoretic immunoassay with laser-induced fluorescence detection

Alzheimer's disease (AD) is a neurodegenerative disorder resulting from an impaired cholinergic function with loss of cognitive activity in the brain. Haptoglobin is a useful biomarker for AD analysis. Compared to the conventional enzyme-linked immunosorbent assay for haptoglobin analysis, the proposed immunoassay procedure reduces sample analysis time by approximately 55 min. Therefore, immunoassay was coupled with capillary electrophoresis (CE) to determine haptoglobin concentrations indirectly by using magnetic nanobeads (MBs) as a support and laser-induced fluorescence detection. In human plasma sample, the haptoglobin was immobilized on the MBs and reacted with the purified anti-haptoglobin antibody. The optimum separation time for the analyte was shorter than 6 min at 25 °C with a fused-silica capillary column of 40.2 cm × 50 μm ID (effective length 30 cm) and a run buffer containing 25 mM phosphate (pH 8.0) with 0.01% poly(ethylene oxide) (PEO). When using Atto 495 NHS ester as an internal standard (IS) (250.0 ng mL(-1)), the linear range of the proposed method for indirect determination of haptoglobin was 0.2-3.0 mg mL(-1). The method was further used to monitor the course of AD in patients with behavioral and psychological symptoms of dementia (BPSD).

A microfluidic device containing membrane-immobilized antibodies for successively capturing cytosolic enzymes

A microfluidic device containing membrane-immobilized anti-esterase (ES) antibodies and anti-lactate dehydrogenase (LDH) antibodies was prepared. The membrane was prepared by transferring antibodies that had been separated by non-denaturing two-dimensional electrophoresis to a polyvinylidene difluoride membrane, which was then stained and cut into small pieces (16 mm(2)). In this microfluidic device, >0.014 Unit mL(-1) of the purified porcine carboxylesterase was specifically captured by membrane-immobilized anti- ES antibodies and >147 Unit mL(-1) of purified porcine LDH was specifically captured by membrane-immobilized anti-LDH antibodies. Furthermore, ES and LDH in micro-scale aliquots of porcine liver cytosol were successively captured by membrane-immobilized antibodies in the device, and the enzyme activities were quantitatively analyzed by spectrofluorometry. The results indicate that the microfluidic device containing membrane-immobilized antibodies can be used to investigate the activities of several types of intact enzymes.