Microspheres With Fluorescent Tags

Carboxylic groups at the surface of poly(l,l-lactide) and poly(e-caprolactone) microspheres could be used for covalent immobilization of fluorescent tags with amino and hydrazine reactive groups. Activation of microspheres and immobilization of 6-aminoquinoline and Lucifer yellow is illustrated in Scheme 7. A typical recipe for attachment of fluorophores (e.g., Lucifer yellow) follows. To a suspension of poly(l,l-lactide) microspheres (9.2 mg, Dn = 2.73 |m) in phosphate buffer (0.325 mL, pH 7.4) containing 0.17% (wt/vol) of SDS the following solutions was added 50 |L of 1-ethyl-3-(3-dimehylaminopropyl)car-bodiimine (concentration 20 mg/mL), 50 |l of water solution of N-hydroxysul-fosuccinimide (concentration 50 mg/mL), and 0.53 mL of water solution of Lucifer yellow (concentration 1 mg/mL). The suspension was gently shaken for 24 h at room temperature. Thereafter, the unbound label was removed by several repeated isolations of microspheres by centrifugation and resuspension in pure water. Figure 32 shows a microscopic picture of fluorescent poly(l,l-lactide) microspheres labeled with Lucifer yellow.

FIG. 32 Fluorescent poly(l,l-lactide) microspheres labeled with Lucifer yellow.

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