Effects of copolymer component on the properties of phosphorylcholine micelles

Figures & data

Figure 1 FTIR spectra of (A) PCL₂₀-ss-PMPC₅, (B) PCL₂₀-ss-PMPC₁₀ and (C) PCL₄₀-ss-PMPC₁₀.

Abbreviations: FTIR, Fourier transform infrared; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide.

Table 1 Synthesis and characteristics of polymers

Sample	CL	MPC	Mna (g/mol)	Mnb (g/mol)	Mwb (g/mol)	PDIb	Tc (°C)	Tm (°C)	ΔHf (J/g)	Xc (%)
PCL20-ss-iBuBr	22	–	2,800	5,600	8,300	1.45	30.08	51.76	67.51	48.46
PCL40-ss-iBuBr	45	–	5,400	8,900	15,100	1.69	32.25	54.49	64.60	46.37
PCL20-ss-PMPC5	22	5	4,300	–	–	–	27.37	53.03	42.41	30.45
PCL20-ss-PMPC10	22	10	6,000	–	–	–	N/A	53.89	4.205	3.02
PCL40-ss-PMPC10	45	10	8,700	–	–	–	18.86	55.13	23.36	16.77
PCL20-PMPC10	20	9	5,000	–	–	–	18.86	45.08	24.09	17.29

Notes:

a Calculated from ¹H·NMR.

b Calculated from GPC. “–” means the item could not be measured.

Abbreviations: CL, ε-caprolactone; GPC, gel permeation chromatography; MPC, 2-methacryloyloxyethyl phosphorylcholine; Mn, number-average molecular weight; Mw, weight-average molecular weight; PDI, polydispersity index; T_c, crystallization temperature; T_m, melting temperature; ΔH_f, melting enthalpy; X_c, degree of crystallinity; N/A, not applicable; PCL-ss-iBuBr, poly(ε-caprolactone) with OH-ss-iBuBr opening-ring polymerization; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly (2-methacryloyloxyethyl phosphorylcholine) without disulfide.

Figure 2 ¹H NMR spectra of (A) PCL₂₀-ss-PMPC₅, (B) PCL₂₀-ss-PMPC₁₀ and (C) PCL₄₀-ss-PMPC₁₀ in CDCl₃ and CD₃OD (v/v =2:1).

Abbreviations: NMR, nuclear magnetic resonance; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide.

Figure 3 DSC curve of different polymers for heating (A) and cooling (B).

Abbreviations: PCL-ss-iBuBr, poly(ε-caprolactone) with OH-ss-iBuBr opening-ring polymerization; DSC, differential scanning calorimetry; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide.

Table 2 Preparation and characteristics of blank micelles and DOX-loaded micelles

Samplea	CMC (mg/L)	Kv (10^5)	Diameter (nm)	PDI	DLC (%)	DLE (%)
PCL20-ss-PMPC5	1.58	4.26	88.41±0.15	0.269±0.010	–	–
PCL20-ss-PMPC10	3.55	3.38	53.72±0.23	0.087±0.006	–	–
PCL40-ss-PMPC10	1.26	5.19	55.76±0.43	0.220±0.008	–	–
PCL20-PMPC10	2.88	3.26	50.84±0.68	0.127±0.013	–	–
PCL20-ss-PMPC5/DOXb	–	–	74.69±0.69	0.132±0.018	6.85±0.41	36.78±2.37
PCL20-ss-PMPC10/DOXb	–	–	48.35±1.31	0.149±0.011	7.16±0.33	38.54±1.91
PCL40-ss-PMPC10/DOXb	–	–	54.37±0.66	0.205±0.012	4.98±0.43	26.18±2.37
PCL20-PMPC10/DOXb	–	–	48.37±0.98	0.125±0.008	6.44±0.57	34.40±3.25

Notes:

a Blank micelles and drug-loaded micelles were prepared with PBS, and the final concentration of the polymer was 0.5 mg/mL.

b The feed mass ratio of polymer/DOX was ~5/1. “–” means that the item does not exist or could not be measured for the sample.

Abbreviations: DOX, doxorubicin; CMC, critical micelle concentration; K_v, partition equilibrium constant; PDI, polydispersity index; DLC, drug-loading content; DLE, drug-loading efficiency; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide; PBS, phosphate-buffered saline.

Figure 4 Measurement of CMC for different block polymers.

Abbreviations: CMC, critical micelle concentration; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide.

Figure 5 Size distribution of blank micelles (A) and DOX-loaded micelles (B). Diameter change of PCL₂₀-ss-PMPC₁₀ (C) and PCL₂₀-PMPC₁₀ (D) micelles in response to 10 mM DTT under 37°C measured by DLS.

Abbreviations: DOX, doxorubicin; DTT, DL-dithiothreitol; DLS, dynamic light scattering; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide.

Figure 6 In vitro drug release of PCL-ss-PMPC/DOX micelles (A–C) and PCL-PMPC micelles (D) in PBS (pH =7.4, 0.01 M) with 10 mM DTT or without DTT at 37°C.

Abbreviations: DOX, doxorubicin; PBS, phosphate-buffered saline; DTT, DL-dithiothreitol; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide.

Figure 7 In vitro cytotoxicity of blank and DOX-loaded micelles.

Notes: Cell viability of HeLa cells (A) and L929 cells (B) incubated with different blank micelles for 72 h at 37°C in 5% CO₂ atmosphere. Cell viability of HeLa cells and L929 cells incubated with different DOX-loaded micelles for 48 and 96 h (n=5, SD <0.06; *P<0.05, **P<0.01, ***P<0.001) (C). In vitro cytotoxicity of different DOX-loaded micelles with various DOX concentrations incubated with HeLa cells (D).

Abbreviations: DOX, doxorubicin; IC₅₀, half inhibitory concentration; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide.

Figure 8 Cellular uptake and intracellular drug release by CLSM (A) and FCM (B).

Note: HeLa cells were incubated with DOX-loaded micelles with the final DOX concentration of 10 μg/mL at 37°C for 2 or 5 h.

Abbreviations: CLSM, confocal laser scanning microscopy; FCM, flow cytometry; DOX, doxorubicin; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide; PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide.

Scheme 1 Illustration for intracellular drug delivery of reduction-responsive micelles with bioinspired phosphorylcholine as hydrophilic chains.

Abbreviations: PCL-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) without disulfide; PCL-ss-PMPC, poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) with disulfide.