What solvent(s) will microspheres tolerate?
Microspheres are generally suspended in deionized water or a biologic buffer (e.g. borate buffer). Compatibility of microspheres and solvents will depend upon their respective solubility parameters (SPs) (numeric values). Numbers that are near one another indicate solubility, whereas disparate numbers indicate solvent resistance, or insolubility. For example, the SP of polystyrene is 9.1; if the SP of a solvent is very similar, e.g. in the range of ~8.6-9.6, it will probably dissolve the microsphere with ease. If the SP is <7 or >11, it may swell the polymer, or dissolve only with extended exposure and/or heat. Microspheres that are crosslinked (e.g. DVB is commonly utilized to “crosslink” polystyrene), will possess some solvent resistance. A listing of common solvents and non-solvents of polystyrene is provided for convenience. Solubility parameters of other solvents and polymers may be obtained from the literature, e.g. Polymer Handbook, J. Brandrup and E.H. Immergut (Eds).
