What liquids can we dispense, print, spot?
All kinds of Samples
A broad variety of liquids, solutions and even suspensions can be dispensed with our different microdispensing technologies. Limit number is defined by their dynamic viscosity. If that is too high, the flow resistance becomes too high, and the result is a dripping tip or blocked flow path, instead of droplet ejection.
Non-contact dispensing requires a minimum velocity with which the liquid flows through the outlet orifice of the dispensing tip. Note: Said velocity refers to distance/time and not to volume/time (flow rate). As a rule of thumb, 50% glycerol in water (V/V), which at 20°C has dynamic viscosity of 8.36 mPas, can be considered a safe upper limit.
The surface tension of the liquid to be dispensed plays a role too, but a less pronounced one. A high solvent-vapour pressure can be a problem for concentrated solutions. If a solid compound were dissolved, clogging caused by precipitation of it would need to be avoided. If a liquid that is too viscous is part of the solution, e.g. glycerol, its concentration may not become too high at the outlet of the tip by solvent evaporation.
Of course, toxicity of the liquid, solution or suspension to be dispensed needs to be considered as well. Most of our customers dispense low-viscous, aqueous solutions of biomolecules, such as nucleic acids, peptides and proteins. However, organic solvents and other chemical molecules are being dispensed by some, too.
- Peptides, including chemically synthesised libraries, glycopeptides and enzymatic digests of proteins
- Proteins, including antibodies, antigens, allergens, glycoproteins and enzyme
- All kinds of chemical reagents
- Carbohydrates, including glycans and glycoconjugates
- Nucleic acids, including DNA and RNA oligomers, PCR products and extracts
- Dyes and other functional molecules
- Living cells, including bacteria, yeast and mammalian cells
- Stable suspensions of nano and small microparticles
- Solvents and mixtures thereof
Allergens cause allergic reactions, which are in most cases an undesired immune response triggered by the presence of antibodies that bind to them. These antibodies can easily be detected by a secondary (e.g. anti-human IGG or IGE) antibody. For that reason, microarrays of many or all known allergens are a powerful tool for allergy testing. These are also produced with the aid of non-contact microdispensing.
Antibodies can be detected with the antigens to which they specifically and strongly bind. Once captured, their presence is detected with a labelled secondary antibody. In medicine, this is taken advantage of, for instance, in the confirmation of a virus infection in the past or the effectiveness of a vaccination.
Autoantibodies play an important role in autoimmune diseases, and they can be screened for by examining blood samples with high-density antigen arrays. Their production is another good example of the use of non-contact microdispensing.
With only a few exceptions, all nucleic acid solutions are well suited for non-contact microdispensing. Typical applications are the production of oligonucleotide microarrays for the detection of virus particles, bacteria, other microbiological species and biological food contamination.
Proteins and Peptides
Many, but not all, peptide and protein solutions are well suited to non-contact microdispensing. Too much detergent - leading to foam formation - can be a problem, as well as too high of a viscosity. In those cases, proper choice of solvent or optimisation of buffer composition are typical measures. Peptide and protein solutions are microdispensed for the generation of microarrays in biochips, for their implementation in biosensors and lab-on-a-chip devices, and for implementation in other diagnostic or bioanalytical formats.
A typical application for peptide arrays is epitope mapping and control of the binding specificity of a selected antibody. Among proteins, antibodies can be considered a class of their own. They are being used for the detection of viruses, bacteria, biological markers, drugs, staining tissue for cancer diagnosis, etc. Serum albumin and casein are proteins that are often used to block hydrophobic surfaces (to make them hydrophilic) in plastic-based biochips. Enzymes can be an important part for the conversion or degradation of target molecules.