Build, Share and Remix: 3D Printing for Speeding Up the Innovation Cycles in Ambient Ionisation Mass Spectrometry (AIMS)

Toward an open-source 3D-printable laboratory

Premise

Low-cost, repairable lab equipment is rare within the biological sciences. By lowering the costs of entry using 3D printing and open-source hardware, our goal is to empower both amateur and professional scientists to conduct research.

Methods

We developed a modular system of 3D-printable designs called COBLE (Collection of Bespoke Laboratory Equipment), including novel and remixed 3D-printable lab equipment that can be inexpensively printed, assembled, and repaired for a fraction of the cost of retail equivalents.

Results

Here we present novel tools that utilize 3D printing to enable a wide range of scientific experiments. We include additional resources for scientists and labs that are interested in utilizing 3D printing for their research.

Discussion

By describing the broad potential that 3D-printed designs can have in the biological sciences, we hope to inspire others to implement and improve upon these designs, improving accessibility and enabling science for all.

OpenASAP: An affordable 3D printed atmospheric solids analysis probe (ASAP) mass spectrometry system for direct analysis of solid and liquid samples

Atmospheric Solids Analysis Probe (ASAP) mass spectrometry is a versatile technique allowing direct sampling of solid and liquid samples, but its adoption is limited due to the high cost of commercial ASAP systems. To address this, we present OpenASAP, an open-source ASAP system for mass spectrometers that can be fabricated for $20 or less using 3D-printing. Our design is readily adaptable to instruments from different manufacturers and can be produced with a variety of additive manufacturing techniques on consumer-grade 3D-printers. The probe allows for rapid sampling of solid and liquid samples without sample preparation, making it useful for high throughput screening, investigating spatial localization and function of analytes in biological samples, and incorporating mass spectrometry in instructional settings. We demonstrate its effectiveness by obtaining mass spectra of three natural product standards at levels as low as 10 ng/ml in liquid samples, and detecting these metabolites in microbial cultures that are difficult to analyze due to complex sample matrices or analyte properties. Furthermore, we demonstrate direct sampling of thin layer chromatography (TLC) spots of these cultures.

A 3D-printed sub-atmospheric pressure electrospray ionization source for robust, facile, and flexible mass spectrometry analysis

The operation and performance of electrospray ionization (ESI) is affected by the surrounding environment. In this study, a compact sub-atmospheric pressure ESI (SAP-ESI) source was designed and fabricated using the 3D printing method. This source has a simple structure and is easy to operate, as the sample solution and auxiliary gas are continuously sucked into the source through the pressure difference. The compact and enclosed ionization chamber can reduce the fluctuation of the surrounding gas flow to ensure a remarkably stable (< 3%) electrospray. Moreover, the source can offer variable SAP conditions for ESI analysis. The yield of analyte ions increases with decreasing pressure, while the production of background ions is suppressed under these conditions. In the analysis of protein samples, SAP-ESI can increase the yield and charge state of ions, which may be due to the reduction of proton transfer between charged proteins and surrounding gas. The SAP-ESI source was then used to continuously monitor the extract aqueous solution of tea leaves, and to detect the carbendazim residues on the apple surface by coupling with the liquid extraction surface analysis technique. Experimental results demonstrate that the developed SAP-ESI is a stable, practical, and versatile ionization technique.

3D printer platform and conductance feedback loop for automated imaging of uneven surfaces by liquid microjunction-surface sampling probe mass spectrometry

RATIONALE

Molecular imaging of samples using mass spectrometric techniques, such as matrix-assisted laser desorption ionization or desorption electrospray ionization, requires the sample surface to be even/flat and sliced into thin sections (c. 10 μm). Furthermore, sample preparation steps can alter the analyte composition of the sample. The liquid microjunction-surface sampling probe (LMJ-SSP) is a robust sampling interface that enables surface profiling with minimal sample preparation. In conjunction with a conductance feedback system, the LMJ-SSP can be used to automatically sample uneven specimens.

METHODS

A sampling stage was built with a modified 3D printer where the LMJ-SSP is attached to the printing head. This setup can scan across flat and even surfaces in a predefined pattern ("static sampling mode"). Uneven samples are automatically probed in "conductance sampling mode" where an electric potential is applied and measured at the probe. When the probe contacts the electrically grounded sample, the potential at the probe drops, which is used as a feedback signal to determine the optimal position of the probe for sampling each location.

RESULTS

The applicability of the probe/sensing system was demonstrated by first examining the strawberry tissue using the "static sampling mode." Second, porcine tissue samples were profiled using the "conductance sampling mode." With minimal sample preparation, an area of 11 × 15 mm was profiled in less than 2 h. From the obtained results, adipose areas could be distinguished from non-adipose parts. The versatility of the approach was further demonstrated by directly sampling the bacteria colonies on agar and resected human kidney (intratumoral hemorrhage) specimens with thicknesses ranging from 1 to 4 mm.

CONCLUSION

The LMJ-SSP in conjunction with a conductive feedback system is a powerful tool that allows for fast, reproducible, and automated assessment of uneven surfaces with minimal sample preparation. This setup could be used for perioperative assessment of tissue samples, food screening, and natural product discovery, among others.