Aliphatic polyester terpolymers for stent coating and drug elution: Effect of polymer composition on drug solubility and release

Figures & data

Table 1.  Poly(L-lactide-co-ε-caprolactone-co-glycolide) copolymers prepared.

Terpolymer	Mon:init:cat	LA:CL:GA feed ratio	Polymer composition	Mn (g/mole)	Mw (g/mole)	PDI	Tg* (°C)
1	750:1:0.2	65:20:15	61:21:18	13,000	22,000	1.63	26
2	750:1:0.2	60:25:15	60:17:23	25,000	41,000	1.67	30
3	4600:0:1	65:20:15	68:18:14	61,000	101,000	1.65	32
4	750:1:0.2	75:20:5	77:17:6	13,000	23,000	1.83	35
5	4100:1:2	76:19:5	78:18:4	50,000	130,000	2.61	37

*T_g value for the second heating run.

Figure 1.  (a) ¹H NMR and (b) ¹³C NMR spectra of poly(L-lactide-co-ε-caprolactone-co-glycolide) terpolymer (Table 1, entry 5).

Figure 2.  DSC thermogram (10°C/min) of terpolymer 5: (a) first heating run; (b) second heating run.

Figure 3.  SEM images of LA:CL:GA terpolymer coated stents, using (a) terpolymer 2 (60:17:23) and (b) terpolymer 4 (77:17:6). Cracks in the coating of (b) are indicated by the arrows.

Table 2.  Coating integrity and drug release with terpolymers containing a drug-to-polymer ratio of 1–3.^a

Terpolymer^b	Mw (g/mole)	Coating integrity	Drug release (%)
			day 1	day 3
1^c	22,000	good	58	84
2^c	41,000	good	38	53
3^d	101,000	good	18	33
4^c	23,000	sticky/cracked	22	34
5^c	130,000	good	16	18

^aEverolimus release was performed in porcine serum.

^bsame polymers from Table 1.

^c1 wt% polymer coated from 9:1 acetone:MIBK.

^d2 wt% polymer coated from 4:1 acetone:MIBK.

Figure 4.  On-stent drug release profile of a terpolymer coating with a LA:CL:GA composition of 68:18:14, and a molecular weight of 61,000 g/mole (Table 1, entry 3), using drug-to-polymer (d/p) ratios of 1/1, 1/2, and 1/3.

Figure 5.  Drug release profile with a d/p = 1/3 of terpolymers with similar LA:CL:GA compositions and different molecular weights (M_w): σ 22,000 g/mole (Table 1, entry 1) and θ 41,000 g/mole (Table 1, entry 2).