Elution Conditions Research Articles

Development and Validation of an Analytical Procedure for the Determination of Caffeic Acid in Nonea rossica Herb by HPLC

INTRODUCTION. According to the literature, alcoholic extracts of Nonea rossica Steven have anticoagulant, antimicrobial, and antifungal properties, which may be due to the presence of caffeic acid and its derivatives in the plant. The standardisation of this herbal drug requires the development of an analytical procedure for the quantitative determination of caffeic acid, and the most promising method for this is high-performance liquid chromatography (HPLC).AIM. This study aimed to develop and validate an analytical procedure for the quantitative determination of caffeic acid in Nonea rossica herb by HPLC.MATERIALS AND METHODS. The study focused on the aerial parts of Nonea rossica plants collected in a steppificated meadow in the Novosibirsk Region during the flowering stage. The study used an Agilent 1100 Series HPLC system equipped with a Zorbax SB-C18 column (150 × 2.1 mm, 3.5 μm) and a detector operating at a wavelength of 330 nm.RESULTS. The authors selected chromatographic conditions to obtain one peak per one molecular form of caffeic acid, acceptable resolution of the extract components, and the maximum intensity of the analyte peak. The gradient elution conditions developed in this study were as follows: a two-component mobile phase, including a 0.01 M aqueous solution of KH2PO4 with a pH of 2.70 (Solvent A) and methanol (Solvent B), and a flow rate of 0.25 mL/min. Under these conditions, caffeic acid eluted at 13.5 minutes, and the total analysis time was 60 minutes. The analytical procedure was validated for its specificity, analytical range, detection limit, quantitation limit, accuracy, repeatability, and intralaboratory precision.CONCLUSIONS. The developed and validated analytical procedure for the quantitative determination of caffeic acid in Nonea rossica herb by HPLC provides results with a relative standard deviation of ≤5.0%. The analytical procedure can be used to standardise the herbal drug Noneae rossicae herba for further use in medicinal practice.

Novel Mesoporous Cetyltrimethylammonium Bromide-Modified Magnetic Nanomaterials for Trace Extraction and Analysis of Bisphenol Endocrine Disruptors in Diverse Liquid Matrices

In this study, Fe3O4 was used as a magnetic core, combined with the characteristics of mesoporous adsorbents, to prepare a novel magnetic mesoporous composite material named MMC. Cetyltrimethylammonium bromide (CTAB) and tetraethyl orthosilicate (TEOS) were used as functional monomers, and a simple etching method was employed. The resulting MMC was used as an effective adsorbent for the magnetic solid-phase extraction of trace residues of six bisphenol endocrine disruptors (bisphenol A, bisphenol B, bisphenol C, bisphenol F, bisphenol AF, and bisphenol AP) from environmental water and food samples. Characterization results indicated that the surface of MMC exhibited a distinct wormhole-like mesoporous structure, with the successful incorporation of CTAB functional groups and Si-OH. The crystal structure of Fe3O4 remained stable throughout the preparation process. Mapping analysis confirmed the uniform distribution of CTAB functional groups without aggregation and demonstrated high magnetic intensity, enabling rapid separation and collection under an external magnetic field. Extraction and elution conditions were optimized, and tests were conducted for interfering substances such as humic acid, glucose, fructose, and sucrose under optimal parameters. The results showed that recovery rates were not significantly affected. The quality evaluation of the method demonstrated good linearity, a broad linear range, low limits of detection and quantification, and satisfactory recovery rates. Blank and spiked analyses were conducted for seven real samples, including environmental water (rivers and lakes) and food samples (dairy, juice, and carbonated beverages), with satisfactory spiked recovery rates achieved. Thus, the developed analytical method enables the analysis and detection of trace residues of various bisphenol pollutants in complex matrices, such as environmental water and food samples, providing a valuable reference for trace analysis of similar contaminants in complex matrices.

IgG-Binding Peptidomimetic Mixed-Charge Polymer-Modified Resins for Chromatographic Purification of Antibodies.

The process of antibody purification using Fc affinity ligands such as protein A, G, and L faces several challenges including high cost, low stability, and loss of antibody activity due to harsh elution conditions. Here, we describe a chromatographic purification of antibodies utilizing a pH-responsive mixed-charge polymer that mimics the IgG-binding peptide (Z34C) derived from the B domain of protein A. The protein A mimetic resins were prepared by modifying the surface of a TOYOPEARL, methacrylate resin with a polymer that mimics the amino acid sequence of Z34C and the functions of histidine and acidic and neutral amino acids using histamine methacrylamide (HisMA), methacrylic acid, and neutral monomers. The therapeutic monoclonal antibody (mAb), rituximab, was retained on the column at pH 7 and eluted under mildly acidic conditions at pH 5 using a protein A mimetic resin (HisMA20-EEMA) optimized for antibody interaction. The injected antibodies were selectively captured on the column by hydrophobic and electrostatic interactions with the protein A mimetic polymer under neutral conditions and eluted by electrostatic repulsion under acidic conditions. The HisMA20-EEMA column successfully purified mAbs from mixtures with BSA, mouse ascites fluid, and hybridoma cell culture supernatant. In addition, the HisMA20-EEMA column consistently achieved 90% antibody recovery in 100 consecutive purifications from cell culture supernatant. The antibody purification method presented in this study is low cost, highly durable, easy to synthesize, and allows for mild elution conditions. The results demonstrate that the approach of mimicking IgG-binding peptides with mixed-charge polymers is useful for the development of column packing materials for antibody purification.

Development of an immobilized Mycobacterium tuberculosis purine nucleoside phosphorylase platform for ligand fishing and inhibition assays

Purine nucleoside phosphorylase (PNP) from Mycobacterium tuberculosis (MtPNP) plays a crucial role in purine metabolism, making it an attractive target for developing new tuberculosis treatments. In this study, we developed a ligand screening platform using MtPNP covalently immobilized on magnetic particles (MtPNP-MPs). The immobilization process achieved a high enzyme loading and preserved the enzyme catalytic activity, enabling its use in both activity and affinity-based screening assays. The activity of MtPNP-MPs was monitored by quantifying hypoxanthine released from inosine phosphorolysis, and kinetic studies revealed Michaelis-Menten behavior for inosine and inorganic phosphate substrates, with KM values comparable to those of free MtPNP. A proof-of-concept inhibitor study using the transition state analog DI4G demonstrated the platform capability for recognizing and characterizing inhibitors, yielding an IC50 value of 91.4 nM and a competitive inhibition mechanism with a Ki of 69.2 nM. Furthermore, the MtPNP-MPs exhibited high stability, retaining over 80 % of their activity after six months of storage and more than 90 % after five consecutive reaction cycles, highlighting their potential for reuse in high-throughput assays. We optimized key parameters for ligand fishing assay, including the amount of MtPNP-MPs, incubation time, and elution conditions. While higher organic solvent concentrations and longer elution times improved ligand isolation, these conditions also reduced enzyme activity. This trade-off between ligand isolation yield and enzyme reusability suggests that elution conditions should be tailored based on the ligand binding strength. Overall, this study establishes the MtPNP-MPs platform as a versatile tool for ligand identification and inhibitor characterization, with promising applications in the screening of complex libraries, such as natural products, for bioactive compounds.

Determination of seven phenoxy carboxylic acid herbicides in water using dispersive solid phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry based on metal-organic framework composite aerogel

Phenoxy carboxylic acid herbicides (PCAs) are difficult to degrade and, thus, pose significant threats to the environment and human health. The limit for 2,4-dichlorophenoxyacetic acid is 30 μg/L in China's standards for drinking water quality, 70 μg/L in the United States' drinking water standards, and 30 μg/L in the World Health Organization's guidelines for drinking water quality. Therefore, the development of an effective detection method for trace PCAs in water is a crucial endeavor. Metal-organic frameworks (MOFs) are novel porous materials that possess advantages such as a large specific surface area, adjustable pore size, and abundant active sites. They exhibit excellent adsorption capability for various compounds. However, the applications of MOFs as adsorbents are limited. For example, the process of isolating powdered MOFs from aqueous solutions is laborious, and microporous MOFs exhibit limited surface affinity, which decreases their mass transfer efficiency in the liquid phase. MOF crystals can be embedded in a substrate to overcome these limitations. Aerogels are obtained by drying hydrogels, which are hydrophilic polymers with a three-dimensional crosslinked network structure. Spongy aerogel materials exhibit unique structural properties such as high porosity, large pore volume, ultralow density, and easy tailorability. When MOFs are combined with an aerogel, their efficient and selective adsorption properties are preserved. In addition, MOF aerogels exhibit a hierarchical porous structure, which enhances the affinity and mass transfer efficiency of the MOF for target molecules. At present, MOF aerogels are primarily prepared by freeze-drying or using supercritical carbon dioxide. These drying processes require significant amounts of energy and time. Hence, the development of greener and more efficient methods to prepare skeleton aerogels is urgently needed. In this study, we prepared an environment-friendly aerogel at ambient temperature and pressure without the use of specialized drying equipment. This ambient-dried MOF composite aerogel was then used for the dispersive solid phase extraction (DSPE) of seven PCAs from environmental water, followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The key parameters affecting the efficiency of DSPE, including the extraction conditions, ratio of MIL-101(Fe)-NH2 to sodium alginate, pH of the aqueous samples, extraction time, ionic strength (salinity), and elution conditions, such as the elution solvent ratio, elution time, and elution volume, were investigated to obtain optimal extraction efficiency. The adsorbent could adsorb the target contaminants within 12 min, and the analytes could be completely desorbed within 30 s by elution with 4 mL of 1.5% (v/v) formic acid in methanol solution. The water samples could be analyzed without pH adjustment. The main adsorption mechanisms were electrostatic interactions and π-π conjugation. Thus, a new method based on MOF aerogels coupled with UHPLC-MS/MS was developed for the determination of the seven PCA residues in water. The calibration curves for the seven PCAs showed good linearity (r2≥0.9986), with limits of detection (LODs) and quantification (LOQs) ranging from 0.30 to 1.52 ng/L and from 1.00 to 5.00 ng/L, respectively. Good intra- and inter-day precision values of 6.5%-17.1% and 7.4%-19.4%, respectively, were achieved under low (8 ng/L), medium (80 ng/L), and high (800 ng/L) spiking levels. The developed method was applied to the detection of PCAs in surface water, seawater, and waste leachate, and the detected mass concentrations ranged from 0.6 to 19.3 ng/L. Spiked recovery experiments were conducted at mass concentrations of 8, 80, and 800 ng/L, and the recoveries ranged from 61.7% to 120.3%. The proposed method demonstrates good sensitivity, precision, and accuracy, and has potential applications in the detection of trace PCAs in environmental water.

Extraction of Penicillin G From Dairy Products Using Deep Eutectic Solvent/Alginate Beads Enhanced via Layered Double Hydroxides.

A new nanocomposite based on alginate microbeads impregnated with novel strontium-aluminum layered double hydroxide (Sr-Al LDH) incorporated with choline chloride-urea deep eutectic solvent (ChCl-U DES) was introduced. The microbeads and LDH were characterized by adsorption/desorption isotherms, Fourier-transform infrared spectroscopy, SEM, and x-ray diffraction. The adsorbent was employed for determining penicillin G (PENG) using dispersive solid-phase extraction prior to HPLC analysis. The extraction efficiency of the adsorbent, compared with that of unmodified alginate, showed a 2.5-fold increase. Significant parameters, including elution conditions, sorbent composition and mass, adsorption time, and sample pH, were optimized. The LOD was 0.4µg kg-1, and the linear range was 1.4-500µg kg-1. The LOQ (1.4 µg kg-1) was lower than the established maximum level for PENG by the European Union (4 µg kg-1). Enrichment factor and synthesis reproducibility were also investigated. The method's accuracy was evaluated through PENG analysis in dairy products and water, with recoveries of 81%-107% (RSDs<7.6%). The procedure's greenness was assessed using the Analytical Eco-scale and achieved excellent green credentials. To the best of our knowledge, this is the first report on the synthesis and application of a novel alginate composite for the extraction of PENG from dairy and water samples.

LC-MS-Based Simultaneous Determination of Biomarkers in Dried Urine Spots for the Detection of Cofactor-Dependent Metabolic Disorders in Neonates.

Deficiency of cofactors for various enzymes can lead to inborn errors of metabolism. These conditions frequently occur as seizures, which lead to permanent brain damage. Newborn screening for biomarkers associated with these disorders can help in early detection and treatment. Our objective was to establish a liquid chromatography mass spectrometry technique for quantifying biomarkers in dried urine spots to detect specific vitamin-responsive inborn errors metabolism. Biomarkers were extracted from dried urine spots using a methanol:0.1% v/v formic acid solution (75:25) containing an internal standard mixture. Separation was achieved using a Luna PFP column (150mm×4.6mm, 3µm) under gradient elution conditions. The LC-MS technique was validated as per ICH M10 guidelines. Urine samples from healthy newborns in Udupi district, South India, were analyzed to establish reference values for these biomarkers. The method demonstrated excellent linearity (R2>0.99) with low limits of quantification: 0.1µg/mL for leucine, isoleucine, valine, proline, hydroxyproline, methylmalonic acid, and 3-hydroxyisovaleric acid; 0.01µg/mL for pipecolic acid and α-aminoadipic semialdehyde; and 0.03µg/mL for piperideine-6-carboxylate. Interconvertibility between urine and dried urine spot assays was observed from the results of the regression and Bland-Altman analyses. Reference intervals for these biomarkers in the Udupi neonatal population were established using the validated dried urine spot method.

Rapid on-site detection of illicit drugs in urine using C18 pipette-tip based solid-phase extraction coupled with a miniaturized mass spectrometer

Drug abuse is a social issue worldwide, and there is an increasing demand for on-site rapid detection of illicit drugs. In this study, a rapid and simple analytical method for the detection of 6-monoacetylmorphine (6-MAM), methamphetamine (MA), methylenedioxymethamphetamine (MDMA), ketamine (K), norketamine (NK), and cocaine (COC) in urine was developed. The developed method combines C18 pipette-tip based solid-phase extraction (C18 PT-SPE) with a miniaturized mass spectrometer (miniMS), exhibiting remarkable simplicity, high sensitivity, and strong reliability, compared with the conventional method. The optimal extraction and elution conditions for C18 PT-SPE were considered as 9 and 3 aspirating-dispensing cycles, respectively. The miniMS parameters including spray voltage, isolation potential, and collision-induced dissociation energy for the detection of these six illicit drugs were optimized using a nano-electrospray ionization method. The limit of detection (LOD), limit of quantification (LOQ), linear range, and linearity for the analysis of six illicit drugs in urine with the proposed C18 PT-SPE-miniMS method were determined. Except for the LOD of K and COC was determined as 0.5 and 0.25 ng mL−1 respectively, and the LOD of 6-MAM MA, MDMA, and NK was determined as 1 ng mL−1. This method enables rapid on-site detection, providing easier operation, lower cost, and better portability compared to conventional methods, making it a potential tool in drug crime investigation and forensic science.

Multiscale simulation of liquid chromatography: Effective diffusion in macro–mesoporous beds and the B-term of the plate height equation

We performed multiscale simulations of analyte sorption and diffusion in hierarchical porosity models of monolithic silica columns for reversed-phase liquid chromatography to investigate how the mean mesopore size of the chromatographic bed and the analyte-specific interaction with the chromatographic interface influence the analyte diffusivity at various length scales. The reproduced experimental conditions comprised the retention of six analyte compounds of low to moderate solute polarity on a silica-based, endcapped, C18 stationary phase with water‒acetonitrile and water–methanol mobile phases whose elution strength was varied via the volumetric solvent ratio. Detailed information about the analyte-specific interfacial dynamics received from molecular dynamics simulations was incorporated through appropriate linker schemes into Brownian dynamics diffusion simulations in three hierarchical porosity models received from physical reconstructions of silica monoliths with a mean macropore size of 1.23 µm and mean mesopore sizes of 12.3, 21.3, or 25.7 nm. The mean mesopore size was found to have a similar influence on the effective mesopore diffusivity as the analyte polarity and the mobile-phase elution strength, which together determine the analyte residence time on a column. A smaller mesopore size attenuated the increase of the effective mesopore diffusivity with increasing mobile-phase elution strength significantly. The effective bed diffusivity was limited by the analyte residence time rather than by morphological details of the mesopore space. The stronger an analyte was retained by the chromatographic interface inside the mesopores, the slower became the mass transfer between the pore space hierarchies and the lower was the effective bed diffusivity. The B-terms of the plate height equation were finally generated with the bed diffusivities and phase-based retention factors derived from the hierarchical porosity models using additional information about the stationary-phase limit obtained from the analysis of analyte–bonded phase contacts. The B-terms highlight analyte- and mobile phase-specific behavior relevant to isocratic and gradient elution conditions in chromatographic practice. In particular, U-shaped B-term curves are observed due to the dominating contribution of the retention factor and the bed diffusivity to the B-term at low and high elution strength of the mobile phase, respectively.

Comprehensive Coverage of Glycolysis and Pentose Phosphate Metabolic Pathways by Isomer-Selective Accurate Targeted Hydrophilic Interaction Liquid Chromatography-Tandem Mass Spectrometry Assay.

The accurate liquid chromatography-tandem mass spectrometry analysis of phosphorylated isomers from glycolysis and pentose phosphate pathways is a challenging analytical problem in metabolomics due to extraction problems from the biological matrix, adherence to stainless steel surfaces leading to tailing in LC, and incomplete separation of hexose and pentose phosphate isomers. In this study, we present a targeted HILIC-ESI-MS/MS method based on a BEH amide fully porous 1.7 μm particle column with an inert surface coating of column hardware and multiple reaction monitoring (MRM) acquisition fully covering the glycolysis and pentose phosphate pathway metabolites. To minimize contact of the phosphorylated analytes with stainless steel surfaces, a μ-ESI-MS probe with a hybrid electrode made of PEEKsil was employed. Optimized HILIC gradient elution conditions with 100 mM ammonium formate (pH 11) provided the separation of hexose monophosphate and pentose phosphate isomers. To ensure good retention time repeatability in HILIC, perfluoroalkoxy alkane bottles were used for the mobile phase (with sd over 60 runs between 0.01 and 0.02 min). For the quantitative assay, the U-13C-labeled cell extract was spiked prior to extraction by metal oxide-based affinity chromatography (MOAC) with TiO2 beads. The concentrations of the 24 targets were quantified in HeLa and human embryonic kidney (HEK293) cells. Erastin-induced ferroptosis in HEK293 cells was accompanied by enhanced levels of fructose-1,6-bis-phosphate, 2- and 3-phosphoglycerate, and 2,3-bis-phosphoglycerate.

A-262 Novel Hepatitis C Virus External Quality Control that is Stable at Ambient Temperature and Suitable For Use in Low-Resource Settings

Abstract Background Notwithstanding the WHO’s initiative to eliminate viral hepatitis by 2030, there are currently 58 million individuals infected with Hepatitis C Virus (HCV). 73% of infected individuals live in low- and middle-income countries (LMIC) where conventional diagnostics are inaccessible due to high costs and lack of trained personnel. The emergence of low-complexity Point of Care tests is critical for improving accessibility and reducing the spread of infection. Additionally, there is a need for external quality controls (EQC) that monitor the accuracy of test results. Given that LMIC have limited access to laboratory equipment, EQC must have simplified handling procedures and storage conditions. Unfortunately, these materials are not available at scale. Microbix strived to develop HCV EQC swab formulations that are stable at ambient temperature. Since this format deviates from standard HCV diagnostic workflows, we sought to establish a simple yet reproducible workflow that can be followed by laboratories worldwide. Methods Microbix developed HCV swab-based EQC that are stable when stored at 2-30°C. The contrived specimens are formulated with protected synthetic HCV whole-genome nucleic acid and human cells. The formulation was quantified via ddPCR and benchmarked against the WHO HCV standard using Xpert® HCV Viral Load Fingerstick Assay. Sample performance was evaluated with various elution buffers (PrimeStore® MTM, eNAT®, TE buffer, Microbix’s proprietary buffer) and handling procedures that require minimal use of laboratory equipment. Each EQC workflow was assessed based on its ability to consistently demonstrate a viral load of 100-200 IU/mL when tested on Cepheid’s platform. Results The EQC tested positive for HCV when eluted in each buffer and processed using a hand-mixing procedure. Only the workflows that used PrimeStore® MTM or eNAT® consistently reported a viral load between 100-200 IU/mL. Conclusions Microbix developed an HCV swab-based EQC that is stable at ambient temperature; however, we observed that consistent elution conditions are imperative for achieving reproducible results. Our findings demonstrate that a universal workflow should be followed to standardize results across testing sites as deviations in elution buffers, volumes, and handling procedures can influence test outcomes.

Accurate determination of three new antihypertensive drugs illegally added to food using ultra-high performance liquid chromatography-tandem mass spectrometry

Effective strategies are required to address food safety issues related to the illegal addition of antihypertensive drugs to food and claims of antihypertensive function. In this study, a novel ultra-high performance liquid chromatography-triple-quadrupole mass spectrometry (UHPLC-MS/MS) method was developed for the simultaneous determination of three antihypertensive drugs (azilsartan, candesartan cilexetil, and lacidipine) in 12 food matrices (pressed candies, solid beverages, alternative teas, tea drinks, biscuits, jellies, mixed liquors, oral liquids, medicinal teas, tablets, hard capsules, and soft capsules). Initially, mass spectrometry parameters, such as the collision energies of the three antihypertensive drugs, were optimized. Subsequently, the response intensities and chromatographic separation conditions of the three drugs in different mobile phases were compared. In addition, to enhance the recoveries, various extraction solvents and purification methods, including solid-phase extraction (SPE) columns and the QuEChERS technique, were investigated. In the developed method, sample determination involved three steps. First, the sample was extracted using 0.2% (v/v) formic acid in acetonitrile and then filtered using high-speed centrifugation, in addition, the extracted solution of alternative tea and medicinal tea was purified using the QuEChERS technique. Second, the supernatant was diluted with water, and filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane. Finally, the analytes were separated on an Agilent Eclipse Plus RRHD C18 column (50 mm×2.1 mm, 1.8 μm) using a 5 mmol/L ammonium formate aqueous solution and acetonitrile as the mobile phases under gradient elution conditions and then detected using UHPLC-MS/MS with positive electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. Quantitative analysis was performed using a matrix-matched external standard method. Methodological validation showed good linear relationships for all three antihypertensive drugs in the investigated concentration ranges, with correlation coefficients (r2) greater than 0.996. The limit of detection (LOD) and limit of quantification (LOQ) of lacidipine were 0.02 mg/kg and 0.04 mg/kg, respectively, whereas those of the other two drugs were 0.01 mg/kg and 0.02 mg/kg, respectively. In the 12 food matrices, the average recoveries of the drugs ranged from 86.6% to 107.5% with relative standard deviations (RSDs) of 1.1%-10.9% (n=6) at low, medium, and high spiked levels. Furthermore, this method was successfully applied to the analysis of real food samples. Overall, the newly developed method is simple, rapid, sensitive, accurate, and suitable for the qualitative and quantitative determination of antihypertensive drugs in different food matrices. This work could provide technical support for food safety agencies in implementing measures against the illegal addition of antihypertensive drugs to food.

Simultaneous determination of 102 synthetic cannabinoids in electronic cigarette oil by liquid chromatography-tandem mass spectrometry

Synthetic cannabinoids (SCs), which are among the most widely abused new psychoactive substances, are much more potent and have greater efficacy than natural cannabis. SCs can be disguised in various ways and are commonly sold in the form of electronic cigarette oil. SCs belong to a large family with structures consisting of a core with substituents, linker, ring with substituents, and tail. New SCs can be developed by adding substituents, such as halogen, alkyl, and alkoxy groups, to the aromatic ring system or by changing the alkyl chain length. Since the emergence of so-called first-generation SCs, subsequent developments have led to eighth-generation indole/indazole amide-based SCs. As of July 1, 2021, the entire category of SCs was added to the list of controlled substances, but implementation requires urgent improvements in detection technologies. Typically, each method is limited to a few SCs. Owing to the vast number of chemically diverse SCs and their fast update speed, the determination and identification of various types of SCs using a single method is challenging. Therefore, rapid, sensitive, and accurate quantitative methods that includes various types of SCs must be developed to meet the demand for the qualitative and quantitative analysis of new SCs in seized electronic cigarette oil. In this study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of 102 SCs in electronic cigarette oil. The mass spectrometry and liquid-phase conditions influencing SC separation and determination were optimized. Using the external standard method, 102 SCs were successfully identified in electronic cigarette oil. The samples were extracted using methanol. Target analytes were separated on a Shimadzu Shim-pack GIST-HP C18 AQ column (100 mm×2.1 mm, 1.9 μm) at a column temperature of 40 ℃. The mobile phases consisted of (A) 0.1% formic acid aqueous solution and (B) methanol-acetonitrile (1∶1, v/v). The gradient elution conditions were as follows: 0-8 min, 55%A-15%A; 8-15 min, 15%A; 15-16 min, 15%A-55%A; 16-18 min, 55%A. The flow rate was 0.4 mL/min and the injection volume was 1 μL. Operating in the multiple reaction monitoring mode, the 102 SCs were identified within 18 min. Each SC exhibited a good linear relationship in the range of 1-100.0 μg/L with a correlation coefficient (r)≥0.9915. The limits of detection were 0.01-0.30 μg/L and the limits of quantification were 0.04-0.99 μg/L, which meet the requirements for analyzing SCs in actual samples. Precision was determined using standard solutions with 2, 10, and 50 μg/L of the SCs. The precisions (n=6) were 0.3%-6.0%. The recoveries of the 102 SCs, as evaluated by spiking electronic cigarette oil at low (2 μg/mL), medium (10 μg/mL), and high (50 μg/mL) levels, were 80.1%-119.8%. Good performance was observed for the analysis of real samples. The developed method is accurate, rapid, sensitive, and effective for the determination of the 102 SCs in electronic cigarette oil, satisfying the requirements for practical qualitative and quantitative analysis.

Peptide ligands for the affinity purification of adenovirus from HEK293 and vero cell lysates

Adenovirus (AdVs) is the viral vector of choice in vaccines and oncolytic applications owing to its high transduction activity and inherent immunogenicity. For decades, AdV isolation has relied on ultracentrifugation and ion-exchange chromatography, which are not suitable to large-scale production and struggle to deliver sufficient purity. Immunoaffinity chromatography resins of recent introduction feature high binding capacity and selectivity, but mandate harsh elution conditions (pH 3.0), afford low yield (< 20%), and provide limited reusability. Seeking a more efficient and affordable alternative, this study introduces the first peptide affinity ligands for AdV purification. The peptides were identified via combinatorial selection and in silico design to target hexons, the most abundant proteins in the adenoviral capsid. Selected peptide ligands AEFFIWNA and TNDGPDYSSPLTGSG were conjugated on chromatographic resins and utilized to purify AdV serotype 5 from HEK293 and Vero cell lysates. The peptide-functionalized resins feature high binding capacity (> 1010 active virions per mL at the residence time of 2 min), provide high yield (> 50%) and up to 100-fold reduction of host cell proteins and DNA. Notably, the peptide ligands enable gentle elution conditions (pH 8) that prevent the “shedding” of penton and fiber proteins, thus affording intact adenovirus particles with high cell-transduction activity. The study of the peptide ligands by surface plasmon resonance and molecular docking and dynamics simulations confirmed the selective targeting of hexon proteins and elucidated the molecular-level mechanisms underlying binding and release. Collectively, these results demonstrate the strong promise of peptide ligands presented herein for the affinity purification of AdVs from cell lysates.

Light-Activated Molecular Purification (LAMP) of Recombinant Proteins.

The production of recombinant proteins has become a focal point in biotechnology, with potential applications in catalysis, therapeutics, and diagnostics. Before their application, these proteins undergo cumbersome downstream processing, including multiple resin-based chromatography steps (ion exchange or affinity-based) to isolate the protein of interest from host cell proteins, which are more abundant. These methods often involve (1) nonspecific binding of host cell proteins onto the resin, (2) a trial and error approach in determining elution conditions for the protein of interest, and (3) complex functionalization of the resin. These processes are also further supplemented with additional processing steps including buffer exchange through dialysis or desalting. Despite the prevalence and need for proteins, challenges persist in optimizing elution conditions and minimizing downstream processing steps, which contribute to the overall cost, impeding their translation into the market. To address these challenges, there has been a growing interest in stimuli-responsive purification systems, which allow for precise control and modulation of the purification process for protein recovery by altering their properties or behavior in response to specific external conditions, such as heat, light, or chemicals. We have developed a light-activated molecular purification (LAMP) system, a stimuli-responsive chromatography technique where the purification of recombinant proteins is triggered by light. We employed a photocleavable protein (PhoCl1) that binds specifically to Ni-NTA resin through a hexa-histidine tag at its N-terminus. We harnessed the ability of PhoCl1 to undergo photocleavage into two fragments for the development of LAMP. To demonstrate LAMP, the protein of interest (POI) is genetically fused to the C-terminus of PhoCl1. The exposure to 405 nm light (1.5 mW cm-2 for 12 h) results in the release of POI into the supernatant. We showcased the potential of LAMP by purifying highly charged green fluorescent proteins and an enzyme, riboflavin kinase. Our custom-built violet light LED setup achieved more than 50% light-induced photocleavage of the fusion constructs, resulting in the release of more than 30% of the POI into the supernatant, with the remainder retained within the resin. All the proteins purified using LAMP were more than 90% pure. Moreover, the comparison of the riboflavin kinase purified through LAMP and the traditional chromatography (Ni-NTA affinity method) revealed no significant changes in the activity levels. These highlight the broad potential of LAMP in providing a facile, yet robust stimuli-responsive protein purification technique, which leverages the potential of light to purify the proteins and overcome the limitations of current conventional chromatography systems.

Detection of low-copy proteins in proteomic studies: issues and solutions.

Detection of low-copy proteins in complex biological samples is one of the most important issues of modern proteomics. The main reason for inefficient detection of low protein concentrations is the insufficient sensitivity of mass spectrometric detectors and the high dynamic range of protein concentrations. In this study we have investigated the possibilities and limitations of a targeted mass spectrometric analysis using the reconstructed system of standard proteins UPS1 (Universal Proteomic Standard 1) as an example. The study has shown that the sensitivity of the method is affected by the concentration of target proteins of the UPS1 system, as well as by a high level of biological noise modelled by proteins of whole E. coli cell lysate. The limitations of the method have been overcome by concentrating and pre-fractionating the sample peptides in a reversed phase chromatographic system under alkaline elution conditions. Proteomic analysis of the biological sample (proteins of the human hepatocellular carcinoma cell line HepG2 encoded by genes of human chromosome 18) showed an increase in the sensitivity of the method as compared to the standard targeted mass spectrometric analysis. This culminated in registration of 94 proteins encoded by genes located on human chromosome18.

Serotype-agnostic affinity purification of adeno-associated virus (AAV) via peptide-functionalized chromatographic resins

Adeno-associated viruses (AAVs) have emerged as a prominent family of vectors for gene delivery, providing therapeutic options to diseases once deemed incurable. At the same time, they necessitate efficient and affordable purification methods that can be platformed to serve all AAV serotypes. Current chromatographic tools, while affording high product purity, fail to bind certain serotypes, provide limited yield and lifetime, and impose harsh elution conditions that can compromise the vector's activity and safety. Addressing these challenges, this work demonstrates the application of new peptide ligands as the first serotype-agnostic technology for AAV purification by affinity chromatography. Our study reveals a pH-dependent affinity interaction: AAV2, AAV3, AAV6, AAV9, and AAVrh.10 are effectively captured at neutral pH, while binding AAV1, AAV5, AAV7, and AAV8 is stronger in a slightly acidic environment. The elution of bound AAVs was achieved using magnesium chloride at neutral pH for all serotypes, consistently affording capsid yields above 50% and genome yields above 80%, together with a >100-fold reduction in host cell proteins and nucleic acids. In particular, peptide ligand A10 exhibited remarkable binding capacity (> 1014 vp per mL of resin) and purification performance for all AAV serotypes, demonstrating broad applicability for gene therapy manufacturing. Finally, this work introduces novel alkaline-stable variants of A10 and demonstrates their use as the first affinity ligands capable of performing multiple cycles of AAV2, AAV8, and AAV9 purification with intermediate caustic cleaning without loss of capacity or product quality. Collectively, these results demonstrate the promise of this technology to further the impact and affordability of gene therapy.

Development of Magnetic Porous Polymer Composite for Magnetic Solid Phase Extraction of Three Fluoroquinolones in Milk.

In this study, a magnetic porous polymer composite with both hydrophilic and hydrophobic groups was synthesized for magnetic solid phase extraction (MSPE) of milk substrates. Optimization was conducted on various parameters, including adsorption dose, solution pH, adsorption time, and some elution conditions. Coupled with a high-performance liquid chromatography fluorescence detector, a novel MSPE method for determination of norfloxacin (NFX), ciprofloxacin (CIP), and enrofloxacin (ENR) in milk was developed based on magnetic metal organic framework polystyrene polymer (Fe3O4@MOF@PLS) as adsorbent. The Fe3O4@MOF@PLS exhibited significantly improved adsorption performance compared to MOF and PLS. Under optimized experimental conditions, the method exhibited good linearity for the three fluoroquinolones (FQs) in the range of 0.5-1000 μg/kg, with limit of detections (LODs) ranging from 0.21 to 1.33 μg/kg, and limit of quantitations (LOQs) from 0.71 to 4.42 μg/kg. The relative standard deviation (RSD) for the three FQs were 3.4-8.8%. The recoveries of three FQs in milk samples ranged from 84.2% to 106.2%. This method was successfully applied to the detection of three FQs in 20 types of milk, demonstrating its simplicity, speed, and effectiveness in analyte enrichment and separation. The method presented advantages in adsorbent dosage, adsorption time, LODs, and LOQs, making it valuable for the analysis and detection of FQs in milk.

Optimization of the polishing process by integrating experimental design and high-throughput screening

Complex bispecific antibody formats tend to form more product-related impurities than monoclonal antibodies. The primary constraints are yield and purity in the polishing stage. The purpose of this study was to enhance the understanding of the optimal working window for four mixed-mode resins and to reduce the burden of resin screening and parameter optimization during process development. This study optimized the loading and elution conditions of four different mixed-mode cationic resins to enhance the yield and purity by integrating Design of Experiments with High-Throughput Screening. It was observed that despite being weakly acidic mixed-mode cationic resins, these four resins exhibited significant differences in their adsorption and elution performances and varied tolerances to salt concentrations. Capto MMC demonstrated strong hydrophobicity, while the performance profiles of MX-Trp-650 M and Nuvia cPrime were similar, with Nuvia cPrime showing superior purification effects. Eshmuno CMX, by extending its side chain ligand, achieved higher binding efficiency and capacity. Through the optimization of salt concentrations or the application of dual-gradient elution strategies, the target protein with high yield (77 %) and purity over 99 % was successfully obtained. This research not only provides in-depth insights into the application of mixed-mode chromatography in the biopharmaceutical field but also offers practical optimization strategies for the industrial-scale purification of bispecific antibodies.

Peptide ligands for the universal purification of exosomes by affinity chromatography.

Exosomes are gaining prominence as vectors for drug delivery, vaccination, and regenerative medicine. Owing to their surface biochemistry, which reflects the parent cell membrane, these nanoscale biologics feature low immunogenicity, tunable tissue tropism, and the ability to carry a variety of payloads across biological barriers. The heterogeneity of exosomes' size and composition, however, makes their purification challenging. Traditional techniques, like ultracentrifugation and filtration, afford low product yield and purity, and jeopardizes particle integrity. Affinity chromatography represents an excellent avenue for exosome purification. Yet, current affinity media rely on antibody ligands whose selectivity grants high product purity, but mandates the customization of adsorbents for exosomes with different surface biochemistry while their binding strength imposes elution conditions that may harm product's activity. Addressing these issues, this study introduces the first peptide affinity ligands for the universal purification of exosomes from recombinant feedstocks. The peptides were designed to (1) possess promiscuous biorecognition of exosome markers, without binding process-related contaminants and (2) elute the product under conditions that safeguard product stability. Selected ligands SNGFKKHI and TAHFKKKH demonstrated the ability to capture of exosomes secreted by 14 cell sources and purified exosomes derived from HEK293, PC3, MM1, U87, and COLO1 cells with yields of up to 80% and up-to 50-fold reduction of host cell proteins (HCPs) upon eluting with pH gradient from 7.4 to 10.5, recommended for exosome stability. SNGFKKHI-Toyopearl resin was finally employed in a two-step purification process to isolate exosomes from HEK293 cell fluids, affording a yield of 68% and reducing the titer of HCPs to 68 ng/mL. The biomolecular and morphological features of the isolated exosomes were confirmed by analytical chromatography, Western blot analysis, transmission electron microscopy, nanoparticle tracking analysis.