Physicochemical Evaluation of L-Ascorbic Acid and Aloe vera-Containing Polymer Materials Designed as Dressings for Diabetic Foot Ulcers

Abstract

Hydrogels belong to the group of polymers that are more and more often considered as innovative dressing materials. It is important to develop materials showing the most advantageous properties from the application viewpoint wherein in the case of hydrogels, the type and the amount of the crosslinking agent strongly affect their properties. In this work, PVP-based hydrogels containing Aloe vera juice and L-ascorbic acid were obtained via UV-induced polymerization. Next, their surface morphology (via both optical, digital and scanning electron microscope), sorption capacity, tensile strength, and elongation were characterized. Their structure was analyzed via FT-IR spectroscopy wherein their impact on the simulated body liquids was verified via regular pH and temperature measurements of these liquids during hydrogels' incubation. It was demonstrated that as the amount of the crosslinker increased, the polymer structure was more wrinkled. Next, hydrogels showed relatively smooth and only slightly rough surface, which was probably due to the fact that the modifiers filled also the outer pores of the materials. Hydrogels demonstrated buffering properties in all incubation media, wherein during the incubation the release of Aloe vera juice probably took place as evidenced by the decrease in the pH of the incubation media and the disappearance of the absorption band deriving from the polysaccharides included in the composition of this additive. Next, it was proved that as the amount of the crosslinker increased, hydrogels' crosslinking density increased and thus their swelling ratio decreased. Hydrogels obtained using a crosslinking agent with higher average molecular weight showed higher swelling ability than the materials synthesized using crosslinker with lower average molecular weight. Moreover, as the amount of the crosslinking agent increased, the tensile strength of hydrogels as well as their percentage elongation also increased.

Keywords: Aloe vera; L-ascorbic acid; crosslinking agent; crosslinking density; dressings; elongation; hydrogels; surface roughness; swelling ability; tensile strength.

Figure 1

Optical image of sample 575/7.5 (a), 575/10.0 (b), and 575/12.5 (c).

Figure 2

Optical image of sample 700/7.5 (a), 700/10.0 (b), and 700/12.5 (c).

Figure 3

3D view and the roughness profile (along the red line) of sample 575/7.5.

Figure 4

3D view and the roughness profile (along the red line) of sample 575/10.0.

Figure 5

3D view and the roughness profile (along the red line) of sample 575/12.5.

Figure 6

3D view and the roughness profile (along the red line) of sample 700/7.5.

Figure 7

3D view and the roughness profile (along the red line) of sample 700/10.0.

Figure 8

3D view and the roughness profile (along the red line) of sample 700/12.5.

Figure 9

SEM image of sample 575/7.5 (a), 575/10.0 (b), and 575/12.5 (c).

Figure 10

SEM image of sample 700/7.5 (a), 700/10.0 (b), and 700/12.5 (c).

Figure 11

pH and temperature measurements during incubation of hydrogels in distilled water.

Figure 12

pH and temperature measurements during incubation of hydrogels in SBF.

Figure 13

pH and temperature measurements during incubation of hydrogels in Ringer liquid.

Figure 14

pH and temperature measurements during incubation of hydrogels in hemoglobin.

Figure 15

FT-IR spectra of PVP-based hydrogels without any additives.

Figure 16

FT-IR spectra showing the impact of the incubation on the structure of sample 575/7.5 (a), 575/10.0 (b), and 575/12.5 (c).

Figure 16

FT-IR spectra showing the impact of the incubation on the structure of sample 575/7.5 (a), 575/10.0 (b), and 575/12.5 (c).

Figure 17

FT-IR spectra showing the impact of the incubation on the structure of sample 700/7.5 (a), 700/10.0 (b), and 700/12.5 (c).

Figure 18

Results of investigations on sorption properties of hydrogels in distilled water (a), SBF (b), Ringer liquid (c), and hemoglobin (d).

Figure 18

Results of investigations on sorption properties of hydrogels in distilled water (a), SBF (b), Ringer liquid (c), and hemoglobin (d).

Figure 19

Stress–strain curves of hydrogel samples obtained using various amount of PEGDA 575 (a) and PEGDA 700 (b).

Figure 20

Mechanical characteristics of hydrogels, i.e., the tensile strength (a), and percentage elongation (b).