Dye leaching from a doped sol-gel is eliminated by conjugation to a dendrimer

The extent of leaching of dye molecules following encapsulation into sol-gel glasses was investigated. Covalent attachment of erythrosin isothiocyanate (EITC) to a polyamidoamine generation 4 (PAMAM) dendrimer, having a molecular weight of 14,215 Da, eliminated all detectable leaching from hydrated monoliths prepared from tetramethylorthosilicate (TMOS). In contrast, a prior study showed that significant leaching takes place when the dye is conjugated to 70 kDa dextran. To eliminate dye leaching via attachment to a macromolecular carrier, an inherently globular macromolecule having an organized secondary structure is therefore required.