Tannic acid-loaded zinc- and copper-doped mesoporous bioactive glass nanoparticles: Potential antioxidant nanocarriers for wound healing

Abstract

Polyphenols such as tannic acid (TA) with antibacterial and antioxidant activities have recently attracted significant attention for wound healing applications. Mesoporous bioactive glass nanoparticles (MBGNs) have also garnered considerable interest to be employed as nanocarriers of therapeutic biomolecules. This study focuses on the fabrication of TA-loaded MBGNs which were doped with two well-known biologically active elements, copper (Cu) and zinc (Zn). The effect of TA loading on the antioxidant and biological properties of the nanoparticles was investigated in the context of potential wound healing applications. As proven with various techniques, TA was successfully loaded on CuMBGNs and ZnMBGNs. With increasing TA concentration, the phenolic content in the nanoparticles was found to increase and CuMBGNs-TA and ZnMBGNs-TA were found to possess 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The nanoparticles not only showed biocompatibility towards normal human dermal fibroblast (NHDF) cells, but they were also found to be hemocompatible. In comparison to CuMBGNs-TA leachates resulting in in vitro wound closure rate of ∼66 %-∼83 %, the dissolution products of ZnMBGNs-TA led to higher wound closure rate (>90 %). Our results demonstrate that CuMBGNs or ZnMBGNs are suitable nanocarriers for antioxidant TA and are candidates to promote wound healing.

Keywords: Copper; Mesoporous bioactive glass nanoparticles; Tannic acid; Wound healing; Zinc.

Graphical abstract

Fig. 1

Schematic showing the preparation of TA-loaded CuMBGNs and ZnMBGNs.

Fig. 2

a) N₂ adsorption-desorption isotherms of TA-loaded and unloaded CuMBGNs and ZnMBGNs. b) Pore size distribution curves of CuMBGNs-30TA and ZnMBGNs-30TA.

Fig. 3

a-c) XRD patterns; d-f) TGA curves and g-i) FTIR spectra of TA-loaded and unloaded nanoparticles. j) FESEM images of ZnMBGNs and CuMBGNs before and after loading with TA (Scale bar: 200 nm). k) EDX analysis of ZnMBGNs-50TA and CuMBGNs-50TA.

Fig. 4

The cumulative TA release profile from a) TA-loaded Cu-MBGNs and b) TA-loaded ZnMBGNs in DPBS. (c) Total phenolic content and (d) DPPH radical scavenging activity of different nanoparticles investigated. Data were analyzed using one-way ANOVA (Tukey Test). Error bars show the mean ± standard deviation (samples in triplicates and four replicates). The symbol (∗) demonstrates the significant differences between two samples of CuMBGNs-30TA and CuMBGNs-50TA or ZnMBGNs-30TA and ZnMBGNs-50TA at p < 0.05.

Fig. 5

a) Hemolysis ratios (%) of TA, ZnMBGNs and CuMBGNs before and after loading. The solid line specifies the hemolysis ratio of 5 %. (b) aPTT and (c) PT of PPP after incubation with 1 mg/mL nanoparticles. Data were analyzed using one-way ANOVA (Tukey Test). Error bars show the mean ± standard deviation. The experiments were performed using blood from three donors and were performed in triplicate for each sample. The significant differences (p < 0.05) are marked by (∗) as compared to PPP pure.

Fig. 6

NHDF cell viability after treatment with the extracts of a) CuMBGNs and TA-loaded CuMBGNs; and b) ZnMBGNs and TA-loaded ZnMBGNs for 48 h at different concentrations: 1 mg/mL, 2 mg/mL and 5 mg/mL. The dashed line specifies the level of cell viability of a biocompatible material (70 %) according to international standard. Data were analyzed using one-way ANOVA (Tukey Test). Error bars illustrate the mean ± standard deviation (samples in triplicates). The significance differences marked by (∗) are displayed in comparison to the control.

Fig. 7

Fluorescence microscopy images showing NHDF cells stained with DAPI (blue), Calcein AM (green) and rhodamine-phalloidin (red) after 48 h treatment with dissolution products of ZnMBGNs, ZnMBGNs-TA, CuMBGNs and CuMBGNs-TA at a concentration of 1 mg/mL (Scale bar = 100 μm).

Fig. 8

a) Wound closure ratios of NHDF cells after exposure to leaching products of CuMBGNs-TA and ZnMBGNs-TA at a concentration of 1 mg/mL. Data were analyzed using one-way ANOVA (Tukey Test). Error bars display the mean ± standard deviation (samples in four replicates). The significance differences marked by (∗) are demonstrated as compared to the control; b) microscopy images of the scratch areas at time 0 h and after 24 h treatment.