Functional Properties of Gelatin-Alginate Hydrogels for Use in Chronic Wound Healing Applications

Abstract

In this study, a hydrogel material based on porcine gelatin and sodium alginate was synthesized for use as a dressing for chronic wound treatment. The hydrogels were covalently cross-linked using polyethylene glycol diglycidyl ether (PEGDE 500), and the interaction between the components was confirmed via FTIR. The properties of the resulting hydrogels were examined, including gel-fraction volume, swelling degree in different media, mechanical properties, pore size, cytotoxicity, and the ability to absorb and release analgesics (lidocaine, novocaine, sodium diclofenac). The hydrogel's resistance to enzymatic action by protease was enhanced both through chemical cross-linking and physical interactions between gelatin and alginate. The absorption capacity of the hydrogels, reaching 90 g per dm² of the hydrogel dressing, indicates their potential for absorbing wound exudates. It was demonstrated that the antiseptic (chlorhexidine) contained in the structured gelatin-alginate hydrogels can be released into an infected substrate, resulting in a significant inhibition of pathogenic microorganisms (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Aspergillus niger). These results clearly demonstrate that the obtained hydrogel materials can serve as non-traumatic dressings for the treatment of chronic and/or infected wounds.

Keywords: crosslinking; drug delivery; gelatin; hydrogel; sodium alginate; wound dressing.

Figure 1

A scheme of the combined gelatin–alginate hydrogel synthesis.

Figure 2

The viscosity of a mixture of 1% aqueous polymer solutions vs. their ratio.

Figure 3

Gel-fraction values of the hydrogel obtained at different PEGDE 500/gelatin–alginate weight ratios. (*—unstructured gelatin-sodium alginate mixture).

Figure 4

The FTIR spectra of the PEGDE 500, alginate, gelatin, and gel fraction of the reaction product isolated after structuring gelatin–alginate.

Figure 5

The force transmitted by the hydrogel under uniaxial compression at a strain of 4.5 mm. (For hydrogels obtained at 20 °C *—hydrogels are destroyed under compression, and the rest of the samples remained intact).

Figure 6

Strain (amplitude sweep) for gelatin–alginate hydrogels crosslinked with different amounts of PEGDE 500 at a temperature of 20 °C (a) and 37 °C (b).

Figure 7

A frequency sweep for gelatin–alginate hydrogels crosslinked with different amounts of PEGDE 500 at a temperature of 20 °C (a) and 37 °C (b).

Figure 8

The viscoelastic characteristics of gelatin–alginate hydrogels crosslinked with different amounts of PEGDE 500 at a temperature of 20 °C (a) and 37 °C (b).

Figure 9

The loss tangent (mechanical loss coefficient tg δ = G″/G′) of hydrogels at different ratios of the structuring agent PEGDE 500 to the gelatin–alginate blend at 20 °C and 37 °C (a). The dependence of the mechanical loss coefficient on temperature for hydrogels with varying ratios of the structuring agent PEGDE 500 to the gelatin–alginate blend (b).

Figure 10

A temperature sweep for gelatin–alginate hydrogels at different ratios of the structuring agent PEGDE 500 to the gelatin–alginate blend.

Figure 11

SEM images of gelatin–alginate hydrogels at different ratios of the structuring agent PEGDE 500 to the gelatin–alginate blend: 1:1 (a); 1:2 (b); 1:3 (c); 1:5 (d); 1:5 (e); and 1:15 (f), swollen twice their original size in water.

Figure 12

The enzymatic degradation of hydrogels at 20 °C: 1—unstructured gelatin; 2, 3, 4—gelatin–alginate hydrogels with a ratio of structuring PEGDE 500 to a gelatin–alginate base of 1:2, 1:3, and 1:5, respectively.

Figure 13

Kinetics of the drug release into phosphate-buffered saline (PBS) and into a 0.001% protease solution in PBS at 37 °C: lidocaine hydrochloride (a); novocaine (b); diclofenac sodium salt (c); and chlorhexidine digluconate (d).

Figure 13

Kinetics of the drug release into phosphate-buffered saline (PBS) and into a 0.001% protease solution in PBS at 37 °C: lidocaine hydrochloride (a); novocaine (b); diclofenac sodium salt (c); and chlorhexidine digluconate (d).