Incorporating redox-sensitive nanogels into bioabsorbable nanofibrous membrane to acquire ROS-balance capacity for skin regeneration

Abstract

Facing the high incidence of skin diseases, it is urgent to develop functional materials with high bioactivity for wound healing, where reactive oxygen species (ROS) play an important role in the wound healing process mainly via adjustment of immune response and neovasculation. In this study, we developed a kind of bioabsorbable materials with ROS-mediation capacity for skin disease therapy. Firstly, redox-sensitive poly(N-isopropylacrylamide-acrylic acid) (PNA) nanogels were synthesized by radical emulsion polymerization method using a disulfide molecule as crosslinker. The resulting nanogels were then incorporated into the nanofibrous membrane of poly(_l-lactic acid) (PLLA) via airbrushing approach to offer bioabsorbable membrane with redox-sensitive ROS-balance capacity. In vitro biological evaluation indicated that the PNA-contained bioabsorbable membrane improved cell adhesion and proliferation compared to the native PLLA membrane. In vivo study using mouse wound skin model demonstrated that PNA-doped nanofibrous membranes could promote the wound healing process, where the disulfide bonds in them were able to adjust the ROS level in the wound skin for mediation of redox potential to achieve higher wound healing efficacy.

Keywords: Nanofibrous membrane; Polylactide; ROS-Balance capacity; Redox sensitivity; Skin regeneration.

Graphical abstract

Scheme 1

The schematic diagram on fabrication of redox-sensitive nanofibrous polylactide membrane and its ROS-balance capacity for promotion of wound healing process.

Fig. 1

Structural characterization of PLLA and PNA nanogels. (a) NMR of PLLA; TEM micrographs of PNA nanogels before (b) and after (c) treatment with 5 mM GSH for 1 h.

Fig. 2

SEM micrographs of the nanofibrous membranes: (a) PLLA, (b) 5% PNA, (c) 10% PNA, (d) 20% PNA. Scale bars: 5 μm.

Fig. 3

Mechanical properties of PLLA and PNA-doped nanofibrous membranes: (a) tensile curves and (b) Young's modulus at different PNA doping concentrations; (c) FTIR spectra of PNA nanogels, as well as PLLA and PNA-dopped nanofibrous membranes; (d) The effect of PNA nanogel amount on the water contact angles of PNA-doped nanofibrous membranes. Data are represented as mean ± SD (n = 3).

Fig. 4

The biocompatibility of PNA nanogels and membranes: (a) Cell viability of L929 cells treated with PNA nanogels for 2 d. (b) Cell proliferation of L929 cells cultured with PLLA and PNA-doped nanofibrous membranes for 1 d and 3 d. Data are represented as mean ± SD (n = 3).

Fig. 5

Fluorescent images of L929 cells on PLLA and PNA-doped nanofibrous membranes after 1 d incubation. Scale bars:25 μm.

Fig. 6

Healing process evaluation of skin wound after treatment with different samples. (a) representative digital photos of wound area of mice treated with control, PLLA, 5% PNA, 10% PNA or 20% PNA; (b) the simulated unhealed skin areas of the mice, and (c) the unhealed ratios of the mice after treatment. Data are represented as mean ± SD (n = 6). *P < 0.05, **P < 0.01, ***P < 0.001.

Fig. 7

The histological evaluation of skin wound after treatment with samples (Control, PLLA and 20% PNA). Hematoxylin-eosin (H&E) staining sections of skin wound for (a) 7 d, (b) 14 d and (c) 19 d.

Fig. 8

Optical in vivo imaging showing intensity and durability of ROS fluorescence signals: (a) ROS production was monitored by DCFH-DA. (b) The integrated relative ROS fluorescent intensity was quantified at different time points. Data are represented as mean ± SD (n = 3). *P < 0.05, **P < 0.01, ***P < 0.001.

Fig. 9

The redox-balance activity of PNA nanogels: (a) Quantitative analysis of the ROS level by fluorescence measurement. (b) GSH content analysis by spectrophotometer. Data are represented as mean ± SD (n = 5). *P < 0.05, **P < 0.01, ***P < 0.001.