Magnetic Sperms

Although my experiments almost fill all my time, I can still be able to read some late and interesting papers. This letter to Langmuir (ASAP Article, DOI: 10.1021/la061988z), for instance, represented a study on the behavior of sperm cells that had uptaken some magnetic particles. As the title indicates, the author found that 'Loading Magnetic Nanoparticles into Sperm Cells Does Not Affect Their Functionality'.

The magnetic nanoparticles, iron oxide (Fe₃O₄) were coated with poly(vinyl alcohol) (PVA), which had been shown to serve as a delivery system for magnetic drugs and was not cytotoxic for the cells studied. When bovine sperm cells were incubated with the magnetite-PVA colloidal solution, the nanoparticles adhered to cell surface immediately, as indicated by the dramatic drop of Fe₃O₄ in supemated percentage. Then the nanoparticles were believed to be internalized into cells via fluid phase endocytosis, where PVA improved the nonspecific, endocytosis-based nanoparticle uptake to cells, and a linear particle uptake showed at 50-140 min of incubation period. It can be imagined that, after penetration, some particles would bind to intracellular organelles, besides those that are free. To determine this discrepancy, two additives were added into the solution at the end of incubation: Digitonin, which releases of the free particles, and SDS (sodium dodecyl sulfate), which releases both the bound and free particles. By determining the released particles after these two treatments the author was able to evaluate the percentage of the particles bound to the organelles.

Particularly, binding of the particles to the acrosome, which plays a central role in the penetration into the zona pellucida via the acrosome reaction (more details) was found. This fact raise immediately the question whether the magnetic particles bound to the acrosome affects its activity. Thus, the motility and the acrosome reaction of the magnetic sperm cells were determined. The results were negative, compared with the blank controls. Both the acrosome reaction and the EGF-receptor ability of the magnetized sperms were similar to the control.

What is really interesting of this paper is an issue the author did not discuss - the potential applications. In a natural fertilization, the sperms are swimming randomly and occasionally some will reach the oocyte. By magnetizing the sperms, we can render them the potential to converge toward a predetermined target, which may be favorable in some circumstances by increase of the fertilization possibility, although it may seem autocratic, the sperms just rotating their tails in vain in this case.