Really Small Beads
At Miltenyi Biotec, scientists are also heeding the call for high-throughput biological sample preparation and automation, with a technology that enables both biomolecule purification and cell sorting.
At about 50 nm in diameter, Miltenyi Biotec’s beads are much smaller than most magnetic beads for biomagnetic separations applications. Beads are applied to the biological sample in suspension while the magnetic separation is performed by placing the columns in a magnet. Following a series of wash steps, researchers can elute the desired biomolecules or cells off the column by displacing the column from the magnetic field.
For cell-sorting applications, smaller beads have an advantage over large beads by exerting faster binding kinetics and not precipitating out of solution. Moreover, they carry a smaller magnetic moment on the cell, allowing an almost quantitative magnetic labeling according to the number of surface receptors similar to that of a single antibody.
They show less cross-linking on the cell surface, and sorted cells are directly compatible with flow cytometry without the need of bead detachment, says Andreas Bosio, head of R&D, stem cells, neuroscience and molecular biology at Miltenyi Biotec.
The beads are nontoxic and degradable, composed of an iron oxide core with a dextran coating that enables functionalization with antibodies for the capture of specific cell types. Customers can run columns manually or purchase an instrument such as the MultiMACS or the AutoMACS for higher throughput and automation.
One interesting feature of Miltenyi Biotec’s instruments is the ability to connect directly to a flow cytometer for highly sensitive analysis of enriched cells, a combination that has been integrated in the MACSQuant. Also, the company offers a comprehensive portfolio of cell-separation products that enable the sorting of all types of cells, including blood cells and tissue-derived cells.
Tissue-derived cells, such as cancer cells in a tissue biopsy, present a unique set of separation challenges due to the cells being associated with the tissue, Bosio says. The firm’s latest instrument for tissue dissociation, known as the gentleMACS Octo Dissociator, performs both mechanical and enzymatic dissociation simultaneously and allows the user to select from a series of programs or to develop customized protocols for unique applications.
Of particular interest to researchers in clinical settings is a fully integrated instrument known as the CliniMACS Prodigy, which was introduced this year. The CliniMACS Prodigy carries samples through from separation to cell culture, containing all the necessary features for many applications in clinical cell therapy, which has been a hot research area recently, Bosio notes.
Although flow-assisted cell sorting has been the go-to technology for cell sorting for several decades, magnetic cell sorting (MACS) has begun making strides in the field in recent years. It’s just a matter of time, Bosio says, before MACS becomes even more well-known, due to its simplicity, reproducibility, and potential for use with more complex cell samples.