Surface plasmon resonance biosensor for the accurate and sensitive quantification of O-GlcNAc based on cleavage by β-D-N-acetylglucosaminidase

Recent development of analytical methods for disease-specific protein O-GlcNAcylation

The enzymatic modification of protein serine or threonine residues by N-acetylglucosamine, namely O-GlcNAcylation, is a ubiquitous post-translational modification that frequently occurs in the nucleus and cytoplasm. O-GlcNAcylation is dynamically regulated by two enzymes, O-GlcNAc transferase and O-GlcNAcase, and regulates nearly all cellular processes in epigenetics, transcription, translation, cell division, metabolism, signal transduction and stress. Aberrant O-GlcNAcylation has been shown in a variety of diseases, including diabetes, neurodegenerative diseases and cancers. Deciphering O-GlcNAcylation remains a challenge due to its low abundance, low stoichiometry and extreme lability in most tandem mass spectrometry. Separation or enrichment of O-GlcNAc proteins or peptides from complex mixtures has been of great interest because quantitative analysis of protein O-GlcNAcylation can elucidate their functions and regulatory mechanisms in disease. However, valid and specific analytical methods are still lacking, and efforts are needed to further advance this direction. Here, we provide an overview of recent advances in various analytical methods, focusing on chemical oxidation, affinity of antibodies and lectins, hydrophilic interaction, and enzymatic addition of monosaccharides in conjugation with these methods. O-GlcNAcylation quantification has been described in detail using mass-spectrometric or non-mass-spectrometric techniques. We briefly summarized dysregulated changes in O-GlcNAcylation in disease.

AuNPs and 2D functional nanomaterial-assisted SPR development for the cancer detection: a critical review

Cancer ranks as a leading cause of death and a huge obstacle to rising life expectancy. If cancers are spotted early there's a high chance of survival. The conventional methods relying on the phenotypic features of the tumor are not powerful to the early screening of cancer. Cancer biomarkers are capable of indicating specific cancer states. Current biochemical assay suffers from time and reagents consuming and discontinuous monitoring. Surface plasmon resonance (SPR) technology, a refractive index-based optical biosensor, has significant promise in biomarker detection because of its outstanding features of label-free, sensitivity, and reliability. The nanomaterial features exotic physical and chemical property work on the process of transferring biorecognition event into SPR signal and hence is functioned as signal enhancer. In this review, we mainly discussed the mechanism of gold nanoparticles (AuNPs) and two-dimensional (2D) functional nanomaterial for improving the SPR signal. We also introduced AuNPs and 2D nanomaterial assisted SPR technology in determining cancer biomarker. Last but not least, we discussed the challenges and outlooks of the aforementioned reformative SPR technology for cancer biomarker determination in the clinical trial.

An overview of tools to decipher O-GlcNAcylation from historical approaches to new insights

O-GlcNAcylation is a post-translational modification which affects approximately 5000 human proteins. Its involvement has been shown in many if not all biological processes. Variations in O-GlcNAcylation levels can be associated with the development of diseases. Deciphering the role of O-GlcNAcylation is an important issue to (i) understand its involvement in pathophysiological development and (ii) develop new therapeutic strategies to modulate O-GlcNAc levels. Over the past 30 years, despite the development of several approaches, knowledge of its role and regulation have remained limited. This review proposes an overview of the currently available tools to study O-GlcNAcylation and identify O-GlcNAcylated proteins. Briefly, we discuss pharmacological modulators, methods to study O-GlcNAcylation levels and approaches for O-GlcNAcylomic profiling. This review aims to contribute to a better understanding of the methods used to study O-GlcNAcylation and to promote efforts in the development of new strategies to explore this promising modification.

A lable-free SPR biosensor based on one peptide sequence with three recognition sites for O-GlcNAc transferase detection

Abnormal O-linked N-acetylglucosamine (O-GlcNAc) concentrations have been associated with many diseases, but the lack of accurate detection method limited O-GlcNAc to be used as a biomarker in clinical diagnosis. Then O-GlcNAc transferase (OGT) has drawn researchers' attention as it closed related to the level of O-GlcNAc and be considered to be a promising new target for diseases diagnosis. Nevertheless, the existing OGT detection methods are either need labeling or the sensitity can not meet the needs of clinic testing. Herein, a label-free and sensitive SPR biosensor was developed for accurate detection of OGT based on a multi-functional peptide. The designed peptide contains three recognition sites, one is the cleavage site of protease K, one is the O-GlcNAcylated site by OGT, and another is six histidine which be used as the signal report probe to recognize Ni²⁺. The immobilized peptide would be cleavaged by proteinase K, then the His-tag residue part will leave the surface of Au film, resulting less His-tag could bind to Ni²⁺ and a small SPR signal would be record. If the peptide is O-GlcNAcylated by OGT, the cleaving reaction would be limited due to the adjacent site of O-GlcNAcylation. Then more His-tag can be left on the Au film and a bigger SPR signal could be record, this signal is associated with the concentration of OGT. Utilizing the change of the peptide configuration as a signal report probe for OGT detection not only avoids labeling of peptide, but also makes the method more sensitive. The determination linear range of OGT is from 2.00 × 10^-13 to 5.00 × 10^-8 M with a detection limit of 1.19 × 10^-13 M, and the separation of two enzyme reactions ensured the high selectivity of the method. Finally, the sensing system was successfully used for OGT detection in blood samples with satisfied recovery. In summary, the label-free SPR platform for accurate detection of OGT in real samples is helpful to promote OGT serve as a biomarker for early clinical diagnosis of O-GlcNAc related diseases.

Recent Progress in Optical Sensors for Biomedical Diagnostics

In recent years, several types of optical sensors have been probed for their aptitude in healthcare biosensing, making their applications in biomedical diagnostics a rapidly evolving subject. Optical sensors show versatility amongst different receptor types and even permit the integration of different detection mechanisms. Such conjugated sensing platforms facilitate the exploitation of their neoteric synergistic characteristics for sensor fabrication. This paper covers nearly 250 research articles since 2016 representing the emerging interest in rapid, reproducible and ultrasensitive assays in clinical analysis. Therefore, we present an elaborate review of biomedical diagnostics with the help of optical sensors working on varied principles such as surface plasmon resonance, localised surface plasmon resonance, evanescent wave fluorescence, bioluminescence and several others. These sensors are capable of investigating toxins, proteins, pathogens, disease biomarkers and whole cells in varied sensing media ranging from water to buffer to more complex environments such as serum, blood or urine. Hence, the recent trends discussed in this review hold enormous potential for the widespread use of optical sensors in early-stage disease prediction and point-of-care testing devices.

A surface plasmon resonance immunoassay for the rapid analysis of methamphetamine in forensic oral fluid

Background

Current chromatographic methods applied for the forensic analysis of methamphetamine are costly, time‐consuming, and require complicated pretreatment procedures. Thus, the rapid detection of methamphetamine is a critical and unmet need. In this study, a surface plasmon resonance (SPR) system based on indirect inhibitive immunoassay was designed for the analysis of methamphetamine in forensic oral fluid samples.

Methods

For the inhibition immunoassay, the diluted oral fluid was mixed with methamphetamine antibody and then injected into the SPR sensor chip. The biosensor chip was constructed by covalently immobilizing of methamphetamine‐bovine serum albumin conjugate onto a carboxymethyl dextran surface at an optimized pH. The concentration of antibody was also optimized.

Results

The SPR biosensor showed good sensitivity with a limit of detection of 0.44 ng/mL and was comparable or lower than the pre‐existing methods. The method was finally tested using oral fluid samples from 20 suspected drug abusers in forensic cases, and it provided an acceptable recovery of 113.2%, indicating good anti‐interference capability of the SPR sensor.

Conclusion

The SPR biosensor was rapid, reproducible, and had a great potential approach for the forensic detection of methamphetamine.