Preparation of two zwitterionic polymer functionalized stationary phases and comparative evaluation under mixed-mode of reversed phase/ hydrophilic interaction/ion exchange chromatography

Zwitterions are a promising choice to prepare separation materials because of their hydrophilicity and biocompatibility. We described the preparation of two zwitterionic polymer functionalized stationary phases and evaluation under mixed-mode chromatography. A zwitterionic monomer, S-(4-vinylbenzyl) cysteine (SVC), was synthesized and bonded to silica via reversible addition fragmentation chain transfer (RAFT) polymerization to afford a zwitterionic stationary phase, Sil-SVC. A hydrophobic monomer, N-(4-phenylbutan-2-yl) acrylamide (NPA), was copolymerized with SVC onto the stationary phase (Sil-SVCNPA) for comparison. The stationary phases were characterized with FT-IR, TGA, EA, and zeta-potential measurements. Mobile phase composition (ACN content, pH and salt concentration) was varied to study the retention property. Linear solvation energy relationship and Van't Hoff plot were used to investigate the retention mechanism and how chromatographic conditions influenced it. Both stationary phases showed a mixed-mode of RPLC/HILIC/IEC and satisfactory performance in separating hydrophobic analytes (alkylbenzenes and polycyclic aromatic hydrocarbons), hydrophilic nucleotide and bases, and anions, high column efficiency of 60,000 plates·m-1 was achieved. In summary, zwitterionic polymers are attractive options to prepare stationary phases and the retention property can be easily regulated by copolymer.

Inside-Out Oriented Choline Phosphate-Based Biomimetic Magnetic Nanomaterials for Precise Recognition and Analysis of C-Reactive Protein

Phospholipid-based materials exhibit great application potential in the fields of chemistry, biology, and pharmaceutical sciences. In this study, an inside-out oriented choline phosphate molecule, 2-{2-(methacryloyloxy)ethyldimethylammonium}ethyl n-butyl phosphate (MBP), was proposed and verified as a novel ligand of C-reactive protein (CRP) to enrich the functionality of these materials. Compared with phosphorylcholine (PC)-CRP interactions, the binding between MBP and CRP was not affected by the reverse position of phosphate and choline groups and even found more abundant binding sites. Thus, high-density MBP-grafted biomimetic magnetic nanomaterials (MBP-MNPs) were fabricated by reversible addition-fragmentation chain transfer polymerization based on thiol-ene click chemistry. The novel materials exhibited multifunctional applications for CRP including purification and ultrasensitive detection. On the one hand, higher specificity, recovery (90%), purity (95%), and static binding capacity (198.14 mg/g) for CRP were achieved on the novel materials in comparison with traditional PC-based materials, and the enriched CRP from patient serum can maintain its structural integrity and bioactivity. On the other hand, the CRP detection method combining G-quadruplex and thioflavin T developed with MBP-MNPs showed a lower detection limit (10 pM) and wider linear range (0.1-50 nM) than most PC-functionalized analytical platforms. Therefore, the inside-out oriented choline phosphate can not only precisely recognize CRP but also be combined with biomimetic nanomaterials to provide high application potential.

Layer-by-layer coating and chemical cross-linking of multilayer polysaccharides on silica for mixed-mode HPLC application

A facile, controllable and environmentally friendly method for fabricating a novel polysaccharide-silica composite stationary phase (SiO₂@(HA-CS)₁₂) was developed in this report. Two natural polysaccharides (hyaluronan acid and chitosan) were controllably coated on the silica surface using a layer-by-layer assembly technique, and then the polysaccharide shell was chemically cross-linked to improve the stability. The column efficiency of the SiO₂@(HA-CS)₁₂ column reached 74 000 plates per m in HILIC mode and 20 100 plates per m in IEC mode, which indicates great potential for separating polar and charged samples.

Comprehensive O-Glycosylation Analysis of the SARS-CoV-2 Spike Protein with Biomimetic Trp-Arg Materials

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a serious public health threat. Most vaccines against SARS-CoV-2 target the highly glycosylated spike protein (S). A good knowledge of the glycosylation profile of this protein is key to successful vaccine development. Unlike the 22 confirmed N-glycosylation sites on SARS-CoV-2 S, only a few O-glycosylation sites on this protein have been reported. This difference is mainly ascribed to the extremely low stoichiometry of O-glycosylation. Herein, we designed the biomimetic materials, Trp-Arg (WR) monomer-grafted silica microspheres (designated as WR-SiO₂), and these biomimetic materials can enrich N- and O-linked glycopeptides with high selectivity. And WR-SiO₂ can resist the nonglycopeptides' interference with the 100 molar fold of BSA during O-linked glycopeptide enrichment. We utilized WR-SiO₂ to comprehensively analyze the O-glycosylation profile of recombinant SARS-CoV-2 S. Twenty-seven O-glycosylation sites including 18 unambiguous sites are identified on SARS-CoV-2 S. Our study demonstrates that the biomimetic polymer can offer specific selectivity for O-linked glycopeptides and pave the way for O-glycosylation research in biological fields. The O-glycosylation profile of SARS-CoV-2 S might supplement the comprehensive glycosylation in addition to N-glycosylation of SARS-CoV-2 S.

Preparation and evaluation of maltose modified polymer-silica composite based on cross-linked poly glycidyl methacrylate as high performance liquid chromatography stationary phase

A new maltose modified polymer-silica composite was fabricated and applied as high performance liquid chromatography (HPLC) stationary phase. The cross-linked poly glycidyl methacrylate (pGMA) layer was chemically bonded to the outer surface as well as pore inner surface of silica beads via in-situ polymerization, and then maltose was modified onto the polymer layer via a [3 + 2] "click" reaction. The porous spherical silica (4 μm diameter) with 300 Å pore size was selected as the matrix so that the 3.25 nm-thick polymer layer fabricated on the pore inner surface would not affect its permeability. The typical 'U-shape' retention curves indicated a mixed-mode retention mechanism of the as-synthesized stationary phase. Both polar and non-polar analytes could be well separated on the stationary phase with column efficiency reaching 123809 plates/m for guanosine in hydrophilic interaction liquid chromatography (HILIC) mode and 46808 plates/m for fluorene in reversed-phase liquid chromatography (RPLC) mode, respectively. Nucleotides and their bases were baseline separated with good peak shape without any buffer salt in mobile phase, suggesting the effective shielding of the silanol groups. The packing material also showed excellent chromatographic repeatability with intraday RSDs of the retention time of five nucleosides less than 0.048% (n = 3) and interday RSDs less than 0.33% (n = 7) and great pH stability (from 1.5 to 10.2). Finally, the stationary phase was applied to the separation of ginseng extract.

Synthesis of molecular brushes by telomerization

This work reports the straightforward synthesis of molecular brushes by telomerization from polythiol multifunctional macrotransfer agents.

Recent development in liquid chromatography stationary phases for separation of Traditional Chinese Medicine components

Traditional Chinese Medicine (TCM) is an ancient medical practice which has been used to prevent and cure diseases for thousands of years. TCMs are frequently multi-component systems with mainly unidentified constituents. The study of the chemical compositions of TCMs remains a hotspot of research. Different strategies have been developed to manage the significant complexity of TCMs, in an attempt to determine their constituents. Reversed-phase liquid chromatography (RPLC) is still the method of choice for the separation of TCMs, but has many problems related to limited selectivity. Recently, enormous efforts have been concentrated on the development of efficient liquid chromatography (LC) methods for TCMs, based on selective stationary phases. This can improve the resolution and peak capacity considerably. In addition, high-efficiency stationary phases have been applied in the analysis of TCMs since the invention of ultra high-performance liquid chromatography (UHPLC). This review describes the advances in LC methods in TCM research from 2010 to date, and focuses on novel stationary phases. Their potential in the separation of TCMs using relevant applications is also demonstrated.