Table 1.
Summary of polymer concentrations and flow rates used to produce double-walled PLLA(PLGA) microspheres. The calculation of PLLA:PLGA mass ratio is based on the assumption that the volumes of polymer and solvent in the solution are additive. The following constant density values are used: ρPLLA = 1.34 g/cm3, ρPLGA = 1.24 g/cm3 and ρDCM = 1.33 g/cm3.
| Sample | PLLA shell concentration (% (w/v)) |
PLGA core concentration (% (w/v)) |
PLLA shell flow rate (ml/h) |
PLGA core flow rate (ml/h) |
PLLA:PLGA polymer mass ratio |
Mean diameter (µm) |
Full PLGA encapsulation (Yes/No) |
|---|---|---|---|---|---|---|---|
| A1 | 5 | 20 | 12 | 4 | 0.46:0.54 | 50.1 ± 3.6 | No |
| A2 | 5 | 20 | 24 | 4 | 0.63:0.37 | 57.2 ± 2.0 | No |
| A3 | 5 | 20 | 36 | 4 | 0.72:0.28 | 74.9 ± 4.2 | Yes |
| B1 | 5 | 30 | 12 | 4 | 0.37:0.63 | 49.2 ± 2.3 | No |
| B2 | 5 | 30 | 24 | 4 | 0.54:0.46 | 59.6 ± 3.6 | No |
| B3 | 5 | 30 | 36 | 4 | 0.64:0.36 | 66.1 ± 2.5 | Yes |
| C1 | 5 | 40 | 12 | 4 | 0.32:0.68 | 58.7 ± 1.6 | No |
| C2 | 5 | 40 | 24 | 4 | 0.49:0.51 | 65.6 ± 1.3 | No |
| C3 | 5 | 40 | 36 | 4 | 0.59:0.41 | 74.0 ± 2.7 | No |