Microdetermination of Sialic Acids in Blood Samples by Hydrophilic Interaction Chromatography Coupled to Post-column Derivatization and Fluorometric Detection

N-glycolylneuraminic acid in red meat and processed meat is a health concern: A review on the formation, health risk, and reduction

One of the most consistent epidemiological associations between diet and human disease risk is the impact of consuming red meat and processed meat products. In recent years, the health concerns surrounding red meat and processed meat have gained worldwide attention. The fact that humans have lost the ability to synthesize N-glycolylneuraminic acid (Neu5Gc) makes red meat and processed meat products the most important source of exogenous Neu5Gc for humans. As our research of Neu5Gc has increased, it has been discovered that Neu5Gc in red meat and processed meat is a key factor in many major diseases. Given the objective evidence of the harmful risk caused by Neu5Gc in red meat and processed meat to human health, there is a need for heightened attention in the field of food. This updated review has several Neu5Gc aspects given including biosynthetic pathway of Neu5Gc and its accumulation in the human body, the distribution of Neu5Gc in food, the methods for detecting Neu5Gc, and most importantly, a systematic review of the existing methods for reducing the content of Neu5Gc in red meat and processed meat. It also provides some insights into the current status and future directions in this area.

Chimeric antigen receptor T cells targeting the GM3(Neu5Gc) ganglioside

Chimeric antigen receptor (CAR) T cell technology has ushered in a new era of immunotherapy, enabling the targeting of a broad range of surface antigens, surpassing the limitations of traditional T cell epitopes. Despite the wide range of non-protein tumor-associated antigens, the advancement in crafting CAR T cells for these targets has been limited. Owing to an evolutionary defect in the CMP-Neu5Ac hydroxylase (CMAH) that abolishes the synthesis of CMP-Neu5Gc from CMP-Neu5Ac, Neu5Gc is generally absent in human tissues. Despite this, Neu5Gc-containing antigens, including the ganglioside GM3(Neu5Gc) have consistently been observed on tumor cells across a variety of human malignancies. This restricted expression makes GM3(Neu5Gc) an appealing and highly specific target for immunotherapy. In this study, we designed and evaluated 14F7-28z CAR T cells, with a targeting unit derived from the GM3(Neu5Gc)-specific murine antibody 14F7. These cells exhibited exceptional specificity, proficiently targeting GM3(Neu5Gc)-expressing murine tumor cells in syngeneic mouse models, ranging from B cell malignancies to epithelial tumors, without compromising safety. Notably, human tumor cells enhanced with murine Cmah were effectively targeted and eliminated by the 14F7 CAR T cells. Nonetheless, despite the detectable presence of GM3(Neu5Gc) in unmodified human tumor xenografts, the levels were insufficient to trigger a tumoricidal T-cell response with the current CAR T cell configuration. Overall, our findings highlight the potential of targeting the GM3(Neu5Gc) ganglioside using CAR T cells across a variety of cancers and set the stage for the optimization of 14F7-based therapies for future human clinical application.

Designing stimuli-responsive upconversion nanoparticles based on a mimetic immunoassay for potential accurate diabetic nephropathy diagnosis

Diabetic nephropathy (DN) is the most common microvascular complication associated with incurable diabetes. The gold standard diagnostic method for DN is based on the detection of proteinuria but it overlooks cases of non-proteinuria (NP-DN). To address this limitation, urinary sialic acid (SA) has been confirmed as an effective biomarker for various DNs. Herein, we constructed an ultrasensitive non-proteinuria assay platform to accurately diagnose DN within 20 min. This platform utilized the ninhydrin reaction between acidic ninhydrin and urinary sialic acid (SA) as an effective biomarker for various DNs. A compound with a maximum absorption peak at 470 nm was produced in this reaction and contributed to the fluorescence decrease of the blue-emission core-shell upconverting nanoparticles through the inner filter effect (IFE). By integrating the inner filter effect (IFE) with a mimetic immunoassay, the imperceptible color was converted into highly sensitive fluorescence signals. This protocol shows a stable and high sensitivity with a detection limit of 20 nmol L-1 and provides 100% positive prediction for urine samples, demonstrating its potential for clinical diagnosis and long-term monitoring of DN.

Developments in on-line, post separation sample manipulation in the last 22 years: Pharmaceutical and biomedical applications

On-line post separation sample manipulation is a powerful approach increasing the sensitivity and selectivity in chemical analysis. Post separation sample manipulation includes the treatment of the analytes after their separation through a suitable separation technique, mainly liquid chromatography and capillary electrophoresis. Typically, post separation approaches include either the addition of a reagent/solvent to derivatize the analyte/enhance the sensitivity, pH change, or the conversion of the analyte through a photochemical/electrochemical system (reagent-free systems). This review focuses on the developed methods using post-column manipulation of sample with pharmaceuticals and biomedical applications, covering the period from 2000 to midle-2023. Chemistries combined with fluorescence, UV-vis and mass spectrometric detection are discussed employing both liquid chromatography and electrophoretic techniques for separation. Noteworthy instrumental modifications are also discussed.

Characterization of novel antibodies that recognize sialylated keratan sulfate and lacto-N-fucopentaose I on human induced pluripotent cells: comparison with existing antibodies

This report describes the isolation and characterization of two new antibodies, R-6C (IgM) and R-13E (IgM), which were generated in C57BL/6 mice (Mus musculus) using the Tic (JCRB1331) human induced pluripotent cell (hiPSC) line as an antigen, and their comparisons with two existing antibodies, R-10G (IgG1) and R-17F (IgG1). Their epitopes were studied by western blotting after various glycosidase digestions, binding analyses using enzyme-linked immunosorbent assays (ELISAs) and microarrays with various synthetic oligosaccharides. The minimum epitope structures identified were: Siaα2-3Galβ1-3GlcNAc(6S)β1-3Galβ1-4GlcNAc(6S)β1 (R-6C), Fucα1-2Galβ1-3GlcNAcβ1-3Galβ1 (R-13E), Galβ1-4GlcNAc(6S)β1-3Galβ1-4GlcNAc(6S)β1 (R-10G), and Fucα1-2Galβ1-3GlcNAβ1-3Galβ1-4Glc (lacto-N-fucopentaose I) (R-17F). Most glycoprotein epitopes are expressed as O-glycans. The common feature of these epitopes is the presence of an N-acetyllactosamine type 1 structure (Galβ1-3GlcNAc) at their nonreducing termini, followed by a type 2 structure (Galβ1-4GlcNAc); this arrangement comprises a type 1-type 2 motif. This motif is also shared by TRA-1-60, a traditional onco-fetal antigen. In contrast, the R-10G epitope has a type 2-type 2 motif. Among these antibodies, R-17F and R-13E exhibit cytotoxic activity toward hiPSCs. R-17F and R-13E exhibit extremely high similarity in the amino acid sequences in their complementarity-determining regions (CDRs), which is consistent with their highly similar glycan recognition. These antibodies are excellent tools for investigating the biological functions of glycoconjugates in hiPSCs/hESCs; they could be useful for the selection, isolation and selective killing of such undifferentiated pluripotent stem cells.

Lanthanide Complexes for Tumor Diagnosis and Therapy by Targeting Sialic Acid

Sialic acid (SA) is overexpressed on cell membranes of tumor cells, and increased serum SA concentration has been observed in tumor-bearing patients. Herein, a series of lanthanide-containing bimetallic complexes (TDA-M-Lns) for targeting SA were prepared via coordination among luminescent lanthanide ions (Ln³⁺ = Tb³⁺, Eu³⁺, Dy³⁺, or Sm³⁺), metal ion quenchers (M²⁺ = Cu²⁺ or Co²⁺), and the organic ligand 2,2'-thiodiacetic acid (TDA). SA can competitively coordinate with Ln³⁺, resulting in the "signal-on" of the Ln³⁺. Therefore, the TDA-M-Lns can be simply used for cost-saving detection of SA in the blood samples. Among the TDA-M-Lns, TDA-Co-Eu showed the highest sensitivity to detect SA in the blood of tumor-bearing mice. Furthermore, the TDA-Co-Eu was successfully used to target SA and deposit Eu³⁺ on the surfaces of tumor cells for the inhibition of tumor cell growth and migration. The therapeutic effect of TDA-Co-Eu on a Balb/c mouse liver tumor model was evaluated. It was proved that TDA-Co-Eu can be applied for SA detection as well as for inhibiting tumor growth.

N-glycosylation modulates enzymatic activity of Trypanosoma congolense trans-sialidase

Trypanosomes cause the devastating disease trypanosomiasis, in which the action of trans-sialidase (TS) enzymes harbored on their surface is a key virulence factor. TS enzymes are N-glycosylated, but the biological functions of their glycans have remained elusive. In this study, we investigated the influence of N-glycans on the enzymatic activity and structural stability of TconTS1, a recombinant TS from the African parasite Trypanosoma congolense. We expressed the enzyme in Chinese hamster ovary Lec1 cells, which produce high-mannose type N-glycans similar to the TS N-glycosylation pattern in vivo. Our MALDI-TOF mass spectrometry data revealed that up to eight putative N-glycosylation sites were glycosylated. In addition, we determined that N-glycan removal via endoglycosidase H_f treatment of TconTS1 led to a decrease in substrate affinity relative to the untreated enzyme but had no impact on the conversion rate. Furthermore, we observed no changes in secondary structure elements of hypoglycosylated TconTS1 in CD experiments. Finally, our molecular dynamics simulations provided evidence for interactions between monosaccharide units of the highly flexible N-glycans and some conserved amino acids located at the catalytic site. These interactions led to conformational changes, possibly enhancing substrate accessibility and enzyme–substrate complex stability. The here-observed modulation of catalytic activity via N-glycans represents a so-far-unknown structure–function relationship potentially inherent in several members of the TS enzyme family.

Glycan Epitopes on 201B7 Human-Induced Pluripotent Stem Cells Using R-10G and R-17F Marker Antibodies

We developed two human-induced pluripotent stem cell (hiPSC)/human embryonic stem cell (hESC)-specific glycan-recognizing mouse antibodies, R-10G and R-17F, using the Tic (JCRB1331) hiPSC line as an antigen. R-10G recognizes a low-sulfate keratan sulfate, and R-17F recognizes lacto-N-fucopentaose-1. To evaluate the general characteristics of stem cell glycans, we investigated the hiPSC line 201B7 (HPS0063), a prototype iPSC line. Using an R-10G affinity column, an R-10G-binding protein was isolated from 201B7 cells. The protein yielded a single but very broad band from 480 to 1236 kDa by blue native gel electrophoresis. After trypsin digestion, the protein was identified as podocalyxin by liquid chromatography/mass spectrometry. According to Western blotting, the protein reacted with R-10G and R-17F. The R-10G-positive band was resistant to digestion with glycan-degrading enzymes, including peptide N-glycanase, but the intensity of the band was decreased significantly by digestion with keratanase, keratanase II, and endo-β-galactosidase, suggesting the R-10G epitope to be a keratan sulfate. These results suggest that keratan sulfate-type epitopes are shared by hiPSCs. However, the keratan sulfate from 201B7 cells contained a polylactosamine disaccharide unit (Galβ1-4GlcNAc) at a significant frequency, whereas that from Tic cells consisted mostly of keratan sulfate disaccharide units (Galβ1-4GlcNAc(6S)). In addition, the abundance of the R-10G epitope was significantly lower in 201B7 cells than in Tic cells.

Long-wavelength Fluorogenic Derivatization of Aryl Halides Based on the Formation of Stilbene by Heck Reaction with Vinylbenzenes

The long-wavelength fluorogenic derivatization method for aryl halides was developed based on stilbene formation by the Heck coupling reaction between aryl halides and vinylbenzenes in the presence of palladium(II) acetate as a catalyst. Fluorescent maximum wavelengths of the derivative obtained by the proposed reaction were 365 - 450 nm, which were 50 - 100 nm longer than those of the biphenyl derivatives formed with our previously developed fluorogenic derivatization method. Also, by the investigation using vinylbenzenes containing electron-donating or -withdrawing functional groups, it was found that an internal charge transfer system could contribute to extend the emission wavelength of the derivative. Furthermore, the proposed reaction was applied to develop a pre-column derivatization HPLC with fluorescence detection method for aryl bromides using 4-vinylanisole. p-Substituted aryl bromide derivatives (i.e., p-bromobenzonitrile, p-bromoanisole, bromobenzene, p-bromobenzoic acid ethyl ester, p-bromotoluene) were successfully detected within 40 min with the detection limit of 0.007 - 0.264 μM. Despite the short reaction time of 10 min, the reaction yields for p-bromoanisole and bromobenzene were good at 101 and 87%, respectively.