Melt electrowritten poly-lactic acid /nanodiamond scaffolds towards wound-healing patches

Abstract

Multifunctional wound dressings, enriched with biologically active agents for preventing or treating infections and promoting wound healing, along with cell delivery capability, are highly needed. To address this issue, composite scaffolds with potential in wound dressing applications were fabricated in this study. The poly-lactic acid/nanodiamonds (PLA/ND) scaffolds were first printed using melt electrowriting (MEW) and then coated with quaternized β-chitin (QβC). The NDs were well-dispersed in the printed filaments and worked as fillers and bioactive additions to PLA material. Additionally, they improved coating effectiveness due to the interaction between their negative charges (from NDs) and positive charges (from QβC). NDs not only increased the thermal stability of PLA but also benefitted cellular behavior and inhibited the growth of bacteria. Scaffolds coated with QβC increased the effect of bacteria growth inhibition and facilitated the proliferation of human dermal fibroblasts. Additionally, we have observed rapid extracellular matrix (ECM) remodeling on QβC-coated PLA/NDs scaffolds. The scaffolds provided support for cell adhesion and could serve as a valuable tool for delivering cells to chronic wound sites. The proposed PLA/ND scaffold coated with QβC holds great potential for achieving fast healing in various types of wounds.

Keywords: Melt electrowriting; Nanodiamonds; Quaternized β-chitin; Wound healing.

Graphical abstract

Fig. 1

Physical properties of preheated PLA and PLA/ND composite for 0, 0.5, 1, 2, and 3 h. a) Heating curve of DSC. b) Weight loss and decomposition temperature shown by TGA. c) Variation of the molecular weight. d) Curve of complex viscosity dependence on angular frequency.

Fig. 2

Physicochemical characterization of materials. a) FTIR spectra and b) ¹H NMR spectra of QβC and untreated β-chitin, the degree of quaternization of QβC is 36.7 %. c) Zeta potential of QβC and NDs.

Fig. 3

a) Macroscopic views and corresponding SEM images of PLA, C/PLA, PLA/ND, and C/PLA/ND scaffolds, images of low magnification show the uniformity of the printed scaffolds, the images at high magnification show the surface roughness of single fiber. b) Cross-section SEM and TEM images of C/PLA/ND scaffolds. These images indicate the decent distribution of NDs inside and on the surface of PLA fibers. c-g) KPFM measurement of surface potential distribution on PLA-based scaffolds: c) PLA, d) QβC-coated PLA, e) PLA/ND, f) QβC-coated PLA/ND. g) ESP of control samples PLA and PLA/ND melts and PLA, QβC-coated PLA, PLA/ND, QβC-coated PLA/ND scaffolds. h) Wettability of scaffolds. The result shows a sharp increase in hydrophilicity of the C/PLA/ND scaffold compared to other groups.

Fig. 4

a) and b) Live/dead staining of S. aureus and E. Coli on these scaffolds after 7-h co-incubation. Dead bacteria shown as red dots were highlighted by red arrows. c) Viability of the two bacteria on PLA-based scaffolds after 7 h. d) and e) the proliferation at various times up to 7 h of co-culture of S. aureus and E. coli with scaffolds. Here * indicates p < 0.05, ** means p < 0.01, *** means p < 0.001 and **** means p < 0.0001. (For interpretation of the references to color/colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5

Cell performance on the printed scaffolds. a) Live and dead staining (green for live cells and red means dead cells) of NHDF-Ad cells on scaffolds after 1-day, 3-day, 7-day, and 14-day cultures to assess cell viability. b) Cell numbers on these scaffolds at day 1 to assess initial cell attachment. c) Cell metabolic activity on the scaffolds growing after day 1, day 3, and day 7 tested by AlamarBlue assay. (For interpretation of the references to color/colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 6

Cell attachment on the scaffolds at day 1. Cell nuclei (blue, marked with red arrows), F-actin (green, marked with red arrows), and focal adhesive protein-vinculin (red, marked with white arrows) were stained to show the cell adhesion on different scaffolds. Scale bar: 50 μm. Bright-field images of the scaffolds are presented with increased brightness (40 %) for better visibility. (For interpretation of the references to color/colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 7

Expression of wound contraction protein (Alpha -SMA in green) and ECM remodeling protein (collagen I) on the different examined scaffolds at day 7. Cell nuclei were marked in blue, the gray images showed a bright field, and F-actin was labeled in red. Scale bar: 50 μm. Bright-field images of the scaffolds are presented with increased brightness (40 %) for better visibility. (For interpretation of the references to color/colour in this figure legend, the reader is referred to the Web version of this article.)