Fostering kappa (κ)-carrageenan hydrogels with the power of a natural crosslinker: a comparison between tender coconut water and potassium chloride (KCl) for therapeutic applications

Abstract

This study investigated the potential of tender coconut water as a natural alternative to potassium chloride (KCl) to crosslink κ-carrageenan hydrogels. κ-Carrageenan hydrogels crosslinked with tender coconut water, KCl, and their combination were formulated with diclofenac sodium as model drug, and their morphology, chemical bonding, compressive strength, water uptake capacity, degradation resistance, and cytotoxicity were assessed. The results showed that crosslinking κ-carrageenan hydrogels with both tender coconut water and KCl increased their compressive strength by up to 450%, provided excellent water retention capacity, and resulted in only 5% degradation after 20 days. Scanning electron microscopy revealed that crosslinking the hydrogel with both tender coconut water and KCl compacted its morphological structure, which remained biocompatible when tested with 3T3 cells. Infrared analysis confirmed that incorporated diclofenac sodium remained inert during preparation of the hydrogel matrices. Furthermore, the in vitro release behavior and antimicrobial properties of the hydrogels were assessed. The drug release profile from hydrogels crosslinked with both tender coconut water and KCl was sustained over 24 h. Such hydrogels also showed a unique antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)-with the activity against E. coli being more pronounced. In conclusion, these results confirm that crosslinking with tender coconut water and KCl is a superior alternative to just with KCl for κ-carrageenan hydrogels.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-025-04254-0.

Keywords: Antibacterial activity; Biocompatibility; Diclofenac sodium; Drug delivery; Polymer matrix; Polysaccharides; Tissue engineering.

Fig. 1

SEM micrographs of κ-carrageenan hydrogels crosslinked with a) tender coconut water, (b) tender coconut water and loaded with diclofenac sodium, (c) KCl, (d) KCl and loaded with diclofenac sodium, (e) tender coconut water and KCl, and (f) tender coconut water and KCl and loaded with diclofenac sodium

Fig. 2

FTIR spectrum of κ-carrageenan hydrogels crosslinked using a tender coconut water with/without diclofenac sodium, b KCl with/without diclofenac sodium and c tender coconut water and KCl with/without diclofenac sodium

Fig. 3

a, b Compressive behavior and strength of the uncrosslinked and crosslinked κ-carrageenan hydrogels, respectively and c Plot of energy absorbed by the hydrogels till the first peak in the load vs. displacement curve

Fig. 4

The swelling behavior of the uncrosslinked and crosslinked κ-carrageenan hydrogels

Fig. 5

The in vitro degradation behavior of the uncrosslinked and crosslinked κ-carrageenan hydrogels at pH 7.4

Fig. 6

a Graph showing 3T3% cell viability of the uncrosslinked and crosslinked κ-carrageenan hydrogels. Each value is expressed as mean ± S.D., n = 3 independent experiments. b Live/dead images of 3T3 fibroblast cells cultured on the uncrosslinked and crosslinked κ-carrageenan hydrogels after one and three days

Fig. 7

The in-vitro diclofenac sodium release profile from the uncrosslinked and crosslinked κ-carrageenan hydrogels at pH 7.4

Fig. 8

The zone of inhibition of a–c Staphylococcus aureus and d–f Escherichia coli exhibited by the uncrosslinked and crosslinked κ-carrageenan hydrogels. The ‘Test’ refers to a crosslinked hydrogel loaded with diclofenac sodium and the ‘ + ve Control’ refers to the crosslinked hydrogel loaded with tetracycline