Ethyl salicylate has been used as a model liquid lipophilic drug for studies of loading of poly(e-caprolactone) microspheres by swelling. Loading has been performed in the following way . Poly(e-microspheres) (5.4 mg, Dn = 0.62 pm, Dw/Dn = 1.5) were suspended in a 7:3 vol/vol ethanol/water mixture containing various amounts of ethyl salicylate (from 1.5 to 50 pL). Total volume
of the mixture was 1 mL. Microspheres were incubated in this mixture for 48 h. Thereafter, they were isolated by centrifugation. Drug loading was determined from the difference in ethyl salicylate concentration in solution before and after incubation with microspheres. The content of ethyl salicylate in poly(e-caprolactone) microspheres as a function of the initial drug concentration in solution is shown in Fig. 29. It is worth noting that in the case of investigated drug with relatively low water solubility the loading of microspheres approached 30 wt %.
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