Biomolecular analysis and biological tissue diagnostics by electrospray ionization with a metal wire inserted gel-loading tip.

A metal wire-inserted disposable gel-loading tip was examined as an electrospray emitter. Its performance was similar to that of conventional electrospray ionization (ESI) with a relatively low flow rate (~100 nL/min) and without the need for solvent pumps. It was also used as an emitter for solid probe-assisted ESI (SPA-ESI) (e.g., biofluid was sampled from the biological tissue by a needle and was inserted into the solvent-preloaded gel-loading tip). Selective detection of lipids and proteins, such α and β chains of hemoglobin could be accomplished by choosing appropriate solvents. A suitable protocol for cancer diagnosis was established by this method. A good figure of merit of this method is its applicability to biological tissue diagnostics with high cost efficiency and on a disposable basis.