µDrop: a system for high-throughput small-angle X-ray scattering measurements of microlitre samples

Abstract

An automatic sample changer system for measurements of large numbers of liquid samples – the µDrop Sample Changer – is presented. It is based on a robotic arm equipped with a pipetting mechanism, which is combined with a novel drop-based sample holder. In this holder a drop of liquid is suspended between two parallel plates by surface tension. The absence of a transfer line benefits the cleaning, improving the background as well as making it faster and more efficient than most comparable capillary-based systems. The µDrop Sample Changer reaches cycle times below 35 s and can process up to 480 samples in a single run. Sample handling is very reliable, with a drop misplacement chance of about 0.2%. Very low sample volumes (<20 µl) are needed and repeatable measurements were performed down to 6 µl. Using measurements of bovine serum albumin and lysozyme, the performance of the instrument and quality of the gathered data of low and high concentrations of proteins are presented. The temperature of samples can also be controlled during storage and during measurement, which is demonstrated by observing a phase transition of a mesophase-forming lipid solution. The instrument has been developed for use in small-angle X-ray scattering experiments, which is a well established technique for measuring (macro-)molecules. It is commonly used in biological studies, where often large sets of rare samples have to be measured.

Bridging the Antimicrobial Activity of Two Lactoferricin Derivatives in E. coli and Lipid-Only Membranes

“…SAXS patterns were recorded using a Pilatus 1 M detector (Dectris, Baden-Daettwil, Switzerland) in the q -range from 0.1 to 5 nm −1 , and further processed with FIT2D ( 35 ). A custom-build cell, termed “nanodrop,” was used, allowing for precise measurements of very small volumes (10 μl) ( 36 ). Measurements were performed at a lipid concentration of 20 mg/ml (24.5−27.9 mM depending on the used membrane mimic) at 37°C.…”

Microfluidic Formulation of DNA-Loaded Multicomponent Lipid Nanoparticles for Gene Delivery

“…Synchrotron small single X-ray scattering (SAXS) measurements were performed at the Austrian SAXS station of the synchrotron light source ELETTRA (Trieste, Italy) by using an automatic sample changer system [ 54 ]. Calibration of the detector (Pilatus3 1 M, Dectris, Baden, Switzerland) was carried out by using silver behenate powder (d-spacing = 58.376), q-range was set within 0.05 and 1.5 nm −1 , exposure times were 10 s (no radiation damage was detected) and temperature was controlled in the vicinity of the capillary.…”

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“…[ 26 ] Measurements were carried out at 20 °C in an auto‐sampler developed in the beamline: the μ‐Drop sample changer μDrop: a system for high‐throughput SAXS measurements of microliter samples. [ 27 ] The μ‐Drop system had several advantages over a capillary based setup, the most important being that because just a single drop was placed, the used volume was 15 μL in a capillaries of 1.5 mm outer diameter/0.01 mm wall thickness made from borosilicate (Hilgenberg, Maisfeld, Germany), enclosed within a thermostatic compartment connected to an external circulation bath and a thermal probe for temperature control. A Pilatus3 1 M detector system based on the CMOS hybrid pixel technology recorded the bidimensional patterns, stored in TIF format and then processed with FIT2D [ 28 ] and Igor Pro (WaveMetrics, Lake Oswego, OR, USA) software.…”