Effects of pH-sensitive chain length on release of doxorubicin from mPEG-b-PH-b-PLLA nanoparticles

Figures & data

Figure 1 Mean diameters of nanoparticles of mPEG₄₅-PH₁₅-PLLA₈₂ (A) and mPEG₄₅-PH₃₀-PLLA₈₂ (B), and zeta potential of mPEG₄₅-PH₁₅-PLLA₈₂ (C) and mPEG₄₅-PH₃₀-PLLA₈₂ (D) nanoparticles at different pH values.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)-poly(L-lactide).

Figure 2 Transmission electron microscopic images of nanoparticles at different pH levels. (A) and (B) are mPEG₄₅-PH₁₅-PLLA₈₂ nanoparticles. (C) and (D) are mPEG₄₅-PH₃₀-PLLA₈₂ nanoparticles. The pH value of (A) and (C) was 5.0 and that of (B) and (D) was 7.4.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)- poly(L-lactide).

Figure 3 Release profiles of doxorubicin-loaded mPEG₄₅-PH₁₅-PLLA₈₂ and mPEG₄₅- PH₃₀-PLLA₈₂ nanoparticles at different pH values.

Abbreviations: DOX, doxorubicin; mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)-poly(L-lactide).

Figure 4 Cell viability of mPEG₄₅-PH₁₅-PLLA₈₂ and mPEG₄₅-PH₃₀-PLLA₈₂ nanoparticles incubated with NIH 3T3 fibroblasts for 24 hours.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)- poly(L-lactide).

Figure 5 Cell viability of mPEG₄₅-PH₁₅-PLLA₈₂ and mPEG₄₅-PH₃₀-PLLA₈₂ nanoparticles incubated with HepG2 cells for 24 hours.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)- poly(L-lactide).

Figure 6 Confocal microscopy photographs of HepG2 cells incubated with doxorubicin-loaded nanoparticles. (A1–A4) doxorubicin for 0.5 hours; (B1–B4) doxorubicin-loaded mPEG₄₅-PH₁₅-PLLA₈₂ nanoparticles for 0.5 hours; (C1–C4) doxorubicin-loaded mPEG₄₅-PH₃₀-PLLA₈₂ nanoparticles for 0.5 hours; (D1–D4) doxorubicin hydrochloride for 0.5 hours; (E1–E4) doxorubicin for 6 hours; (F1–F4) doxorubicin-loaded mPEG₄₅-PH₁₅-PLLA₈₂ nanoparticles for 6 hours; (G1–G4) doxorubicin-loaded mPEG₄₅- PH₃₀-PLLA₈₂ nanoparticles for 6 hours; (H1–H4) doxorubicin hydrochloride for 6 hours. Note: The four photographs from left to right are red doxorubicin, stained nucleus, bright field, and overlapped graphs.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)- poly(L-lactide).

Figure 7 Flow cytometry results of doxorubicin, doxorubicin hydrochloride, and doxorubicin-loaded mPEG₄₅-PH₁₅-PLLA₈₂ and mPEG₄₅-PH₃₀-PLLA₈₂ nanoparticles incubated with HepG2 cells at 37°C for 6 hours (doxorubicin concentration 10 μg/mL).

Notes: 1, control; 2, doxorubicin; 3, doxorubicin hydrochloride; 4, doxorubicin-loaded mPEG₄₅-PH₁₅-PLLA₈₂ nanoparticles; 5, doxorubicin-loaded mPEG₄₅-PH₃₀- PLLA₈₂ nanoparticles.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)- poly(L-lactide).

Figure 8 Morphology of HepG2 cells incubated with doxorubicin-loaded nanoparticles, the time was 36 hours and the concentration of doxorubicin was 15 μg/mL. (A) Cell culture plate, (B) doxorubicin hydrochloride, (C) doxorubicin, (D) doxorubicin-loaded mPEG₄₅-PH₁₅-PLLA₈₂ nanoparticles, and (E) doxorubicin-loaded mPEG₄₅-PH₃₀-PLLA₈₂ nanoparticles.

Abbreviation: mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)-poly(L-lactide).

Figure 9 In vitro antitumor activity of doxorubicin-loaded nanoparticles incubated with HepG2 cells, drug concentration was 15 μg/mL.

Abbreviations: DOX, doxorubicin; mPEG-PH-PLLA, methoxyl poly(ethylene glycol)-poly(L-histidine)-poly(L-lactide).

Figure 10 In vitro antitumor activity of doxorubicin-loaded nanoparticles with different drug concentrations, incubation time was 36 hours.

Abbreviations: DOX, doxorubicin; mPEG-PH-PLLA, methoxyl poly(ethylene glycol)- poly(L-histidine)-poly(L-lactide).

Figure S1 The synthetic route of mPEG-PH-PLLA triblock copolymer.

Abbreviations: NHS, N-Hydroxysuccinimide; DCC, N,N’-Dicyclohexylcarbodiimide; MEE, methoxyethoxyethanol.

Figure S2 The ¹H NMR spectra of mPEG₄₅-NH₂, mPEG₄₅-PH₃₀ and mPEG₄₅-PH₃₀-PLLA₈₂.

Abbreviation: ppm, parts per million.

Table S1 Characterizations of mPEG-PH-PLLA triblock copolymer nanoparticles

Sample	Receiveda	Designedb	Mnc	DLC (%)	EE (%)
1	mPEG45-PH15-PLLA82	mPEG45-PH17-PLLA82	10388	9.6	24.5
2	mPEG45-PH30-PLLA82	mPEG45-PH39-PLLA82	12668	13.2	27.7

Notes:

a The repeated units of L-histidine in the copolymers were calculated from ¹H NMR spectra of mPEG-PH diblock copolymers;

b the designed feeding dose;

c calculated from ¹H NMR spectra of mPEG-PH-PLLA tiblock copolymers.

Abbreviations: DLC, drug loading content; EE, encapsulation efficiency; Mn, number average molecular weight.