Capillary electrophoresis with laser-induced fluorescence detection for laboratory diagnosis of galactosemia

Single-atom Nanozymes for Biomedical Applications： Recent Advances and Challenges

Nanozymes have received extensive attention in the fields of sensing and detection, medical therapy, industry, and agriculture thanks to the combination of the catalytic properties of natural enzymes and the physicochemical properties of nanomaterials, coupled with superior stability and ease of preparation. Despite the promise of nanozymes, conventional nanozymes are constrained by their oversized size and low catalytic capacity in sophisticated practical application environments. single-atom nanozymes (SAzymes) were characterized as nanozymes with high catalytic efficiency by uniformly distributed single atoms as catalysis sites, thus effectively addressing the defects of conventional nanozymes. This paper reviews the activity improvement scheme and catalytic mechanism of SAzymes and highlights the latest research progress of SAzymes in the fields of biomedical sensing and therapy. Eventually, the challenges and future directions of SAzymes are discussed in this paper.

Combining First and Second-Tier Newborn Screening in a Single Assay Using High-Throughput Chip-Based Capillary Electrophoresis Coupled to High-Resolution Mass Spectrometry

BACKGROUND

Most first-tier newborn screening (NBS) biomarkers are evaluated by a 2-min flow injection analysis coupled to tandem mass spectrometry (FIA-MS/MS) assay. The absence of separation prior to MS/MS analysis can lead to false positives and inconclusive results due to interferences by nominal isobars and isomers. Therefore, many presumptive positive specimens require confirmation by a higher specificity second-tier assay employing separations, which require additional time and resources prior to patient follow-up.

METHODS

A 3.2-mm punch was taken from dried blood spot (DBS) specimens and extracted using a solution containing isotopically labeled internal standards for quantification. Analyses were carried out in positive mode using a commercially available microfluidic capillary electrophoresis (CE) system coupled to a high-resolution mass spectrometer (HRMS).

RESULTS

The CE-HRMS platform quantified 35 first- and second-tier biomarkers from a single injection in <2-min acquisition time, thus, successfully multiplexing first- and second-tier NBS for over 20 disorders in a single DBS punch. The CE-HRMS platform resolved problematic isobars and isomers that affect first-tier FIA-MS/MS assay specificity, while achieving similar quantitative results and assay linearity.

CONCLUSIONS

Our CE-HRMS assay is capable of multiplexing first- and second-tier NBS biomarkers into a single assay with an acquisition time of <2 min. Such an assay would reduce the volume of false positives and inconclusive specimens flagged for second-tier screening.

Voltammetric Determination of Phenylalanine Using Chemically Modified Screen-Printed Based Sensors

This paper describes the sensitive properties of screen-printed carbon electrodes (SPCE) modified by using three different electroactive chemical compounds: Meldola’s Blue, Cobalt Phthalocyanine and Prussian Blue, respectively. It was demonstrated that the Prussian Blue (PB) modified SPCE presented electrochemical signals with the highest performances in terms of electrochemical process kinetics and sensitivity in all the solutions analyzed. PB-SPCE was demonstrated to detect Phe through the influence it exerts on the redox processes of PB. The PB-SPCE calibration have shown a linearity range of 0.33–14.5 µM, a detection limit (LOD) of 1.23 × 10−8 M and the standard deviation relative to 3%. The PB-SPCE sensor was used to determine Phe by means of calibration and standard addition techniques on pure samples, on simple pharmaceutical samples or on multicomponent pharmaceutical samples. Direct determination of the concentration of 4 × 10−6–5 × 10−5 M Phe in KCl solution showed that the analytical recovery falls in the range of 99.75–100.28%, and relative standard deviations in the range of 2.28–3.02%. The sensors were successfully applied to determine the Phe in pharmaceuticals. The validation of the method was performed by using the FTIR, and by comparing the results obtained by PB-SPCE in the analysis of three pharmaceutical products of different concentrations with those indicated by the producer.

Peroxidase-like activity of Fe-N-C single-atom nanozyme based colorimetric detection of galactose

Single atom nanozymes are the artificial enzymes with enzyme-like activity, which have attracted a great deal attention in recent years due to their unique merits such as remarkable stability, excellent atom utilization and low cost. Herein, a convenient and sensitive colorimetric strategy was developed for the sensing of galactose based on Fe-N-C single-atom nanozyme (Fe-SAzyme). The Fe-SAzyme was prepared through "isolation-pyrolysis" method that exhibited intrinsic peroxidase mimicking activity, which can quickly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue-colored oxTMB in the presence of hydrogen peroxide (H₂O₂). Galactose can be oxidized by galactose oxidase (Gal Ox) to generate H₂O₂, and Fe-SAzyme can be utilized for quantitative colorimetric detection of galactose. A good linearity between absorbance and the galactose concentration in the range of 50-500 μM was obtained with a detection limit of (LOD) 10 μM. The Fe-SAzyme based colorimetric strategy offered a rapid, convenient and economic way for galactose quantification detection, which could be used as an alternative method for galactosemia diagnosis.

Microchip in situ electrosynthesis of silver metallic oxide clusters for ultra-FAST detection of galactose in galactosemic newborns' urine samples

This work describes for the first time the coupling of microfluidic chips (MC) to electrosynthetized silver metallic oxide clusters (AgMOCs). As an early demonstration of this novel approach, the ultrafast detection of galactose in galactosemic newborns' urine samples is proposed. AgMOCs were in situ electrosynthetized on integrated microchip platinum electrodes using a double pulse technique and characterized in full using scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques revealing the presence of silver oxides and electrocatalysis towards galactose as a galactosemia biomarker. Galactose detection in galactosemic newborns' urine samples proceeded in less than 30 s, differentiating between ill and healthy urine samples and requiring negligible urine sample consumption. The significance of the newborns' urine samples confirmed the analytical potency of the MC-AgMOCs approach for future implementation of screening for rare disease diagnosis such as galactosemia.

Peroxidase-like activity of 2',7'-difluorofluorescein and its application for galactose detection

The peroxidase-like activity of 2',7'-difluorofluorescein (DFF), was investigated using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate in the presence of H₂O₂. DFF could catalyze oxidization of TMB by H₂O₂ to produce a blue colored oxidation product. Effect of various reaction conditions, such as pH, temperature, H₂O₂ concentration and reaction time on the catalytic activity of DFF was studied. The peroxidase-like activity of DFF was found to follow Michaelis-Menten kinetics, and its catalysis accorded with ping-pong mechanism. The calculated kinetic parameters (K_cat) of DFF catalysis showed higher peroxidase-like activity than fluorescein and 2',7'-dichlorofluorescein (DCF). According to the radical capture and electron spin resonance (ESR) spectroscopy results, we confirmed that hydroxyl radical (•OH) is the active specie of catalytic process. It is known that the oxidation of galactose by galactose oxidase (GAOx) enzyme leads to the formation of H₂O₂, the H₂O₂ released in this reaction was consequently quantified using DFF as peroxides mimics and TMB as the chromogen. Thus, a combination of above two reactions was exploited to establish a method for galactose detection. Under the optimum conditions, the linear range of this method was from 10 μM to 20 mM with the detection limit down to 3 μM. Moreover, the developed method was applied to detect galactose in urine samples. Our work will facilitate the utilization of DFF intrinsic peroxidase-like activity in medical diagnostics and biotechnology.

Vertically-Oriented and Shape-Tailored Electrocatalytic Metal Nanowire Arrays for Enzyme-Free Galactosemia Rapid Diagnosis

Metallic catalytic nanowires such as nickel and copper nanowires (NWs) for electrochemical detection of carbohydrates involved in metabolic rare diseases are proposed. NWs were electrodeposited using a polycarbonate membrane template, which was cut with the desired shape, stuck in double-sided adhesive tape, pasted into a non-conductive substrate and in situ removed. This simple and versatile approach allowed to obtain NWs vertically oriented (v-NWs), which are contained in the double-sided adhesive tape, becoming highly versatile. The high specific surface of working electrode in which the transduction is supported exclusively by the nanomaterial yielded a high analytical performance [extremely low fouling for galactose (RSD<2 %; n=25)]. Likewise, v-NWs exhibited a superior analytical performance with respect to commercial sputtered thick-film electrodes showing also a clear advantage related with the price, as well as with non-need clean room facilities. The analytical potency of the new approach was clearly demonstrated towards the fast and reliable diagnosis of galactosemia using precious newborn urine samples compared to standard clinical diagnosis. These results revealed new opportunities for future enzyme-free diagnosis and development of future point-of-care applications.

Aqueous normal phase retention of nucleotides on silica hydride-based columns: method development strategies for analytes relevant in clinical analysis

An aqueous normal phase HPLC method coupled with UV or ESI/MS detection was used for the determination of a wide variety of nucleotides, essential in metabolomics studies. Fifteen nucleotides were tested in clinically relevant mixtures at levels of 100 microg/mL for UV detection and 1 microg/mL for ESI-MS detection. Analysis times for all protocols developed were less than 20 min. The chromatographic conditions were changed to achieve optimized retention and separation of the nucleotides studied. The aqueous normal phase-HPLC methods were developed utilizing two columns, one having a minimally modified hydride surface another having an undecanoic acid moiety on a hydride surface. Volatile, low ionic strength mobile phases were used. Negative ion mode ESI-MS at near neutral pH mobile phase, combined with a TOF detector provided a highly sensitive and specific method, which is equally suitable for quadrupole and ion trap instruments.

Sensitive determination of carbohydrates labelled withp-nitroaniline by capillary electrophoresis with photometric detection using a 406 nm light-emitting diode

p-Nitroaniline was explored as a derivatising reagent for UV absorbance detection of carbohydrates after separation by CE. This derivatising agent has three advantages: first, it has excellent water solubility; second, it has high molar absorptivity; and third, it is possible to obtain sensitive detection using a UV or blue light-emitting diode (LED) as the light source. The labelling reaction took less than 30 min to complete with high reaction yield. The separation process was modelled and optimised using an artificial neural network. Nine carbohydrates were separated by a CE system within 16 min using a 0.17 M boric acid buffer at pH 9.7. On-column LED detection at 406 nm allowed the detection of carbohydrates with good detection limits (<1.1 microM or 8.8 fmol) and reproducible quantification in the concentration range of 2.6-200 microM. This method was applied successfully to the determination of component carbohydrates in some food samples.

Micellar electrokinetic chromatographic and capillary zone electrophoretic methods for screening urinary biomarkers of human disorders: a critical review of the state-of-the-art

Human urine plays a central role in clinical diagnostic being one of the most-frequently used body fluid for detection of biological markers. Samples from patients with different diseases display patterns of biomarkers that differ significantly from those obtained from healthy subjects. The availability of fast, reproducible, and easy-to-apply analytical techniques that would allow identification of a large number of these analytes is thus highly desiderable since they may provide detailed information about the progression of a pathological process. From among the variety of methods so far applied for the determination of urinary metabolites, capillary electrophoresis, both in the capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) modes, represents a robust and reliable analytical tool widely used in this area. The aim of the present article is to focus the interest of the reader on recent applications of MEKC and CZE in the field of urinary biomarkers and to discuss advantages and/or limitations of each mode.