MALDI-readable array platform for affinity capture screening

A. Dikmans, R. Frank; with Institutes IOT, IMT, HTEE and IPC of TU-Braunschweig

Planar arrays of synthetic probe molecules have been advanced during the last decade primarily towards massive miniaturisation and parallelisation to allow a very sensitive detection of analyte molecules directly on the surface. A significant widening of the scope of applications of such arrays is concerned with their utilisation as a multiplexed affinity capture tool for non-labelled analyte molecules that would need further analytical investigations for their identification. This requires, however, a different optimisation of the array properties which includes that the captured analytes must be available for subsequent manipulations and analytical methods. For one of such challenging goals, we want to implement in-situ matrix assisted laser desorption mass spectroscopy (MALDI-MS) to determine the molecular weight of captured analytes as big as e.g. antibodies (about 120,000 Dalton) directly from the array surface.

Previous work by our research group in this area has led to the construction of the BioDisc-Synthesizer (rapid 100 Hz nL-dispensing of reagents with ink jet valves), that utilises a novel type of array format based on the Compact Disc (r/φ-array), and the development of a MALDI-MS compatible array-synthesis substrate consisting of a polyacrylate grafted conductive plastic disc (28). The current state of this development is a uniformly derivatised surface of the CD substrate suffering, however, from severe limitations in array density and reproducibility, due to undesired lateral movement of delivered reagent droplets and liquid spreading. These limitations should be overcome by employing a micro-structured or “patterned” surface with a defined “liquid-capturing”, functionalised spot array. Currently, the instrument is capable of placing 2500 droplets of about 3 nl within 25 sec. Our goal is to increase this to at least 10.000 if not 40.000 droplets per disc.


Left: working principle of the BioDisc synthesizer. 1: CD-type support; 2: Axis of rotation; 3: Spots; 4: Jib range for ink-jet heads; 5: Swivel axis for ink-jet heads; 6: Feed pipe for reagents; 7: Holder for ink-jet heads; 8: Ink-jet head; 9: Zero-position; 10: Rotary angle of the support (array-coordinateφφ ); 11: Rotary angle of ink-jet heads (array-coordinate r). Right: View of a spotted BioDisc.



The focus of the project funded by VW Foundation is on a new class of area-selective surface modification processes, based on atmospheric pressure microplasmas, which will integrate surface treatment and lateral microstructuring within one process to generate distinct hydrophilic spots separated by hydrophobic barriers. The long-term goal of the joint effort of five research groups is to gain sufficient knowledge about the scientific and technical aspects of these methods to allow a well-founded assessment of their technological potential for microproduction processes and their applications, specifically towards the production of micro-patterned functionalised surfaces.