Polydopamine-based surface modification for the development of peritumorally activatable nanoparticles

Abstract

Purpose: To create poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), where a drug-encapsulating NP core is covered with polyethylene glycol (PEG) in a normal condition but exposes a cell-interactive TAT-modified surface in an environment rich in matrix metalloproteinases (MMPs).

Methods: PLGA NPs were modified with TAT peptide (PLGA-pDA-TAT NPs) or dual-modified with TAT peptide and a conjugate of PEG and MMP-substrate peptide (peritumorally activatable NPs, PANPs) via dopamine polymerization. Cellular uptake of fluorescently labeled NPs was observed with or without a pre-treatment of MMP-2 by confocal microscopy and flow cytometry. NPs loaded with paclitaxel (PTX) were tested against SKOV-3 ovarian cancer cells to evaluate the contribution of surface modification to cellular delivery of PTX.

Results: While the size and morphology did not significantly change due to the modification, NPs modified with dopamine polymerization were recognized by their dark color. TAT-containing NPs (PLGA-pDA-TAT NPs and PANPs) showed changes in surface charge, indicative of effective conjugation of TAT peptide on the surface. PLGA-pDA-TAT NPs and MMP-2-pre-treated PANPs showed relatively good cellular uptake compared to PLGA NPs, MMP-2-non-treated PANPs, and NPs with non-cleavable PEG. After 3 h treatment with cells, PTX loaded in cell-interactive NPs showed greater toxicity than non-interactive ones as the former could enter cells during the incubation period. However, due to the initial burst drug release, the difference was not as clear as microscopic observation.

Conclusions: PEGylated polymeric NPs that could expose cell-interactive surface in response to MMP-2 were successfully created by dual modification of PLGA NPs using dopamine polymerization.

Fig. 1

Schematic diagram of a peritumorally activatable nanoparticle (PANP).

Fig. 2

Schematic diagram of preparation of NPs used in this study.

Fig. 3

Scanning electron micrographs of PLGA, PLGA-pDA, and PLGA-pDA-TAT NPs.

Fig. 4

Drug release kinetics from PTX/PLGA NPs, PTX/PLGA-pDA-TAT NPs, PTX/PLGA-PEG NPs, and PTX/PANPs. Each data point represents an average and standard deviation of at least 3 identically and independently prepared samples (ANOVA, Tukey test means comparison, p<0.05).

Fig. 5

Cellular uptake of *PLGA, *PLGA-pDA, and *PLGA-pDA-TAT NPs. NPs were added to SKOV-3 cells in culture medium supplemented with 10% FBS. NP: green fluorescence signal from NPs; Nu: nuclei stained with Draq5; Tm: transmission image; Overlay: overlay of NP, Nu and Tm. Magnification: 600×. Scale bar = 40 μm.

Fig. 6

(A) A representative flow cytometry overlay histogram showing fluorescence intensity of SKOV-3 cells treated with *PLGA, *PLGA-pDA, and *PLGA-pDA-TAT NPs. (B) Geometric mean fluorescence intensity (GMFI) of SKOV-3 cells treated with *PLGA, *PLGA-pDA, and *PLGA-pDA-TAT NPs. Data are expressed averages and standard deviations of 3 tests performed with identically and independently prepared samples. *: p<0.05 by Tukey test means comparison (difference from control was not indicated).

Fig. 7

Viability of SKOV-3 cells treated with PTX/PLGA NPs or PLGA/PLGA-pDA-TAT NPs. Data are expressed as averages with standard deviations of 3 identically and independently prepared samples. (For IC₅₀ calculation, see Supporting Table).

Fig. 8

Cellular uptake of *PANPs and *PLGA-PEG NPs with or without MMP-2 pre-treatment. Scale bar = 20 μm.

Fig. 9

A representative flow cytometry overlay histograms showing fluorescence intensity of SKOV-3 cells treated with *PLGA-PEG and *PANP NPs. (A) Without MMP-2 treatment and (B) with MMP-2 treatment. (C) Geometric mean fluorescence intensity (GMFI) of SKOV-3 cells treated with *PLGA-PEG and *PANP NPs. Data are expressed averages and standard deviations of 3 tests performed with identically and independently prepared samples. *: p<0.05 by one-tailed t-test.

Fig. 10

Viability of SKOV-3 cells treated with PTX/PANPs or PTX/PLGA-PEG NPs with or without MMP-2 pre-treatment. Data are expressed as averages with standard deviations of 3 identically and independently prepared samples. *: p<0.05 by Tukey test means comparison.