LEGO MINDSTORMS Fraction Collector: A Low-Cost Tool for a Preparative High-Performance Liquid Chromatography System

Establishing aqueous two-phase flotation coupled with preparative high performance liquid chromatography and its application for the purification of astragalin from Flaveria bidentis

The strategy of aqueous two-phase flotation (ATPF) followed by preparative high performance liquid chromatography (prep-HPLC) was established and used for the separation of astragalin from Flaveria bidentis. In the ATPF, the effects of sublation solvent, solution pH, (NH4)2SO4 concentration in aqueous solution, cosolvent, N2 flow rate, flotation time and volumes of the PEG phase on the recovery of astragalin were investigated in detail, and the optimal conditions of ATPF were selected: 50 wt% PEG1000 ethanol solvent as the flotation solvent, pH 4, 350 g/L of (NH4)2SO4 concentration in 5 % ethanol aqueous phase, 40 mL/min of N2 flow rate, 30 min of flotation time, 10.0 mL of flotation solvent volume and twice. After ATPF enrichment, the flotation product was further purified by prep-HPLC. As determined by HPLC, the purity of astragalin was 98.8 %.

Streamlining regular liquid chromatography with MALDI-TOF MS and NMR spectroscopy using automatic full-contact splitless spotting interface and flash-tap fractioning collection

BACKGROUND

High-resolution matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and nuclear magnetic resonance (NMR) spectroscopy are powerful tools to identify unknown psychoactive substances. However, in complex matrices, trace levels of unknown substances usually require additional fractionation and concentration. Specialized liquid chromatography systems are necessary for both techniques. The small flow rate of nano LC, typically paired with MALDI-TOF MS, often results in prolonged fractionation times. Conversely, the larger flow rate of semi-preparative LC, used for NMR analysis, can be time-consuming and labor-intensive when concentrating samples. To address these issues, we developed an integrated automatic system that integrated to regular LC.

RESULT

Automatic spot collector (ASC) and automatic fraction collector (AFC) were present in this study. The ASC utilized in-line matrix mixing, full-contact spotting and real time heating (50 °C), achieving great capacity of 5 μL droplet on MALDI plate, high recovery (76-116%) and rapid evaporation in 2 min. The analytes were concentrated 4-8 times, forming even crystallization, reaching the detection limit at the concentration of 50 μg L-1 for 12 psychoactive substances in urine. The AFC utilizes flexible tubing which flash-tapped the microtube's upper rim (3 mm depth) instead of reaching the bottom. This method prevents sample loss and minimizes the robotic arm's movement, providing a high fractionating speed at 6 s 12 psychoactive compounds were fractionated in a single round analysis (recovery: 81%-114%). Methamphetamine and nitrazepam obtained from drug-laced coffee samples were successful analyzed with photodiode array (PDA) after one AFC round and NMR after five rounds.

SIGNIFICANCE

The ASC device employed real-time heating, in-line matrix mixing, and full-contact spotting to facilitate the samples spotting onto the MALDI target plate, thereby enhancing detection sensitivity in low-concentration and complex samples. The AFC device utilized the novel flash-tapping method to achieve rapid fractionation and high recovery rate. These devices were assembled using commercially available components, making them affordable (400 USD) for most laboratories while still meeting the required performance for advanced commercialized systems.

An open-source smart fraction collector for isocratic preparative liquid chromatography

Preparative liquid chromatography is a technique for separating complex samples or isolating pure compounds from complex extracts. It involves eluting samples through a packed column and selectively collecting or isolating the separated bands in a sequence of fractions. Depending on the column length and the sample complexity, a large number of fractions may be obtained, making fraction collection a laborious and time-consuming process. Manual fraction collection is also tedious, error-prone, less reproducible, and susceptible to contamination. Several commercial and lab-made solutions are available for automated fraction collection, but most systems do not synchronize with the instrument detector and collect fractions at fixed volumes or time intervals. We have assembled a low-cost Arduino-based smart fraction collector that can record the signal from the UV-vis detector of the chromatography instrument and enable the automated selective collection of the targeted bands. The system consists of a robot equipped with position sensors and a 3-way solenoid valve that switches the column effluent between the waste or collection positions. By proper programming, an Arduino board records the detector response and actuates the solenoid valve, the position sensors, and the stepper motors to collect the target chromatographic bands.

Low-cost modular chromatography column rack and vial holders

Gravity-driven chromatography columns are used in scientific, engineering, medical, and industrial fields to separate desired compounds from solutions. Running multiple columns simultaneously saves time and improves procedural consistency. Though column chromatography is widely used, to meet their laboratory needs many investigators must resort to designing and fabricating custom racks for holding their chromatography columns. We have created a robust column rack design, with collection vial holders, that is easily made, inexpensive to build, and may be easily adapted to fit experimental needs. The column holder can be made to hold various sizes of columns (and can be interchanged as necessary); the height of columns above collection vials can be precisely set; and the design is modular, so the rack and vial holders can be expanded to accommodate the desired numbers of columns and the numbers and sizes of vials used to collect fractions eluted from each column. Importantly, the rack is made of inexpensive, readily-available materials and the fabrication is straightforward. Here we present details of the rack's features, a list of materials, and instructions for making it. We hope our design will help investigators who perform gravity-driven column chromatography.

Open source fraction collector/MALDI spotter for proteomics

We describe a complete open-source hardware/software solution for high performance thermostatted peptide fraction collection to support mass spectrometry experiments with complex proteomes. The instrument is easy to assemble using parts readily available through retail channels at a fraction of the cost compared to typical commercial systems. Control software is written in Python allowing for rapid customization. We demonstrate several useful applications, including the automated deposition of LC separated peptides for matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) as well as collection and concatenation of peptide fractions from nanoflow HPLC separations.

LIFGO: A modular laser-induced fluorescence detection system based on plug-in blocks

In this work, a laser-induced fluorescence (LIF) detection system built in a modular assembling mode was developed based on commercial LEGO blocks and 3D printed blocks. We designed and fabricated a variety of 3D printed building blocks fixed with optical components, including laser light source, filters, lens, dichroic mirror, photodiode detector, and control circuits. Utilizing the relatively high positioning precision of the plug-in blocks, a modular construction strategy was adopted using the flexible plug-in combination of the blocks to build a highly sensitive laser-induced fluorescence detection system, LIFGO. The LIFGO system has a simple structure which could be constructed by inexperienced users within 3 h. We optimized the structure and tested the performance of the LIFGO system, and its detection limits for sodium fluorescein solution in 100 μm i.d. and 250 μm i.d. capillaries were 7 nM and 0.9 nM, respectively. Based on the LIFGO system, we also built a simple capillary electrophoresis (CE) system and applied it to the analysis of DNA fragments to demonstrate its application possibility in biochemical analysis. The separation of 7 fragments in DL500 DNA markers were completed in 600 s. Because of the features of low cost (less than $100) and easy-to-build construction, we introduced the LIFGO system to the experimental teaching of instrumental analysis for undergraduate students. The modular construction form of the LIF detection system greatly reduces the threshold of instrument construction, which is conducive to the popularization of the LIF detection technique in routine laboratories as well as the reform of experimental teaching mode.

Microliter-level multi-channel fraction collector for high-throughput separation system

High-performance liquid chromatography (HPLC) plays an important role in analytical applications. To perform high-throughput analysis, especially multi-channel separation, numerous fractions need to be collected. However, multi-channel fraction collector has not been commercialized. Therefore, here we present a multi-channel fraction collector fabricated by 3D-printing technology that can adapt to various kinds of HPLC applications. The collector can perform high accuracy microliter-level fraction cutting for narrow-bore or capillary columns as well as conventional columns. Hundreds of fractions can be collected in a single LC run within 1 hour to meet the demands of high-throughput separation. The collector mainly consists of several environmental-friendly 3D-printed parts and other parts are also easy to purchase, making it possible for researchers to construct it in any kind of lab at a very low price. The automated integrated controller and programs are also introduced to fit different collecting and further analysis requirements. In this work, the structure, functions and automation process of the collector are described in detail, which offers a powerful tool for further development on high-throughput separation.

Low-cost, scalable, and automated fluid sampling for fluidics applications

We present colosseum, a low-cost, modular, and automated fluid sampling device for scalable fluidic applications. The colosseum fraction collector uses a single motor, can be built for less than $100 using off-the-shelf and 3D-printed components, and can be assembled in less than an hour. Build Instructions and source files are available at https://doi.org/10.5281/zenodo.4677604.

Castaneroxy A From the Leaves of Castanea sativa Inhibits Virulence in Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) represents one of the most serious infectious disease concerns worldwide, with the CDC labeling it a "serious threat" in 2019. The current arsenal of antibiotics works by targeting bacterial growth and survival, which exerts great selective pressure for the development of resistance. The development of novel anti-infectives that inhibit quorum sensing and thus virulence in MRSA has been recurrently proposed as a promising therapeutic approach. In a follow-up of a study examining the MRSA quorum sensing inhibitory activity of extracts of Italian plants used in local traditional medicine, 224C-F2 was reported as a bioactive fraction of a Castanea sativa (European chestnut) leaf extract. The fraction demonstrated high activity in vitro and effective attenuation of MRSA pathogenicity in a mouse model of skin infection. Through further bioassay-guided fractionation using reverse-phase high performance liquid chromatography, a novel hydroperoxy cycloartane triterpenoid, castaneroxy A (1), was isolated. Its structure was established by nuclear magnetic resonance, mass spectrometry and X-ray diffraction analyses. Isomers of 1 were also detected in an adjacent fraction. In a series of assays assessing inhibition of markers of MRSA virulence, 1 exerted activities in the low micromolar range. It inhibited agr::P3 activation (IC₅₀ = 31.72 µM), δ-toxin production (IC₅₀ = 31.72 µM in NRS385), supernatant cytotoxicity to HaCaT human keratinocytes (IC₅₀ = 7.93 µM in NRS385), and rabbit erythrocyte hemolytic activity (IC₅₀ = 7.93 µM in LAC). Compound 1 did not inhibit biofilm production, and at high concentrations it exerted cytotoxicity against human keratinocytes greater than that of 224C-F2. Finally, 1 reduced dermonecrosis in a murine model of MRSA infection. The results establish 1 as a promising antivirulence candidate for development against MRSA.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Fractionated charge variants of biosimilars: A review of separation methods, structural and functional analysis

The similarity between originator and biosimilar monoclonal antibody candidates are rigorously assessed based on primary, secondary, tertiary, quaternary structures, and biological functions. Minor differences in such parameters may alter target-binding, potency, efficacy, or half-life of the molecule. The charge heterogeneity analysis is a prerequisite for all biotherapeutics. Monoclonal antibodies are prone to enzymatic or non-enzymatic structural modifications during or after the production processes, leading to the formation of fragments or aggregates, various glycoforms, oxidized, deamidated, and other degraded residues, reduced Fab region binding activity or altered FcR binding activity. Therefore, the charge variant profiles of the monoclonal antibodies must be regularly and thoroughly evaluated. Comparative structural and functional analysis of physically separated or fractioned charged variants of monoclonal antibodies has gained significant attention in the last few years. The fraction-based charge variant analysis has proved very useful for the biosimilar candidates comprising of unexpected charge isoforms. In this report, the key methods for the physical separation of monoclonal antibody charge variants, structural and functional analyses by liquid chromatography-mass spectrometry, and surface plasmon resonance techniques were reviewed.

Nonlinear behavior in preparative liquid chromatography: A method-development case study for hydroxytyrosol purification

Preparative liquid chromatography has become an important purification method owing to its advantages of high separation efficiency, good reproducibility, and low solvent consumption. Because overloading in preparative liquid chromatography must be performed to increase the throughput in a cycle, nonlinear chromatographic behavior is observed. Therefore, it is crucial to carefully study nonlinear chromatography for the purification of a given product, which facilitates the efficient optimization of the purification parameters. In this work, a method for the development of a purification method using preparative liquid chromatography based on nonlinear chromatography is proposed. Hydroxytyrosol was selected as the subject for method demonstration. Using methanol and ethanol as organic modifiers, the optimum flow rate was determined on three commercial columns entitled C₈ TDE, C₁₈ ME, and C₁₈ TDE, respectively. The curves were fitted with the van Deemter equation, with thorough analysis of the A, B, and C terms. Adsorption isotherms were subsequently studied to explore the distribution of solutes between the stationary and mobile phases at equilibrium. C₁₈ TDE, 5 vol% ethanol-water, and 0.2 mL/min were selected as the optimal separation material, elution solvent, and flow rate, respectively. Purification of hydroxytyrosol was tentatively confirmed on a C₁₈ TDE column with 1.6% sample loading, 90.98% recovery, and 98.01% purity.