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. 2024 Sep 25;22(10):434.
doi: 10.3390/md22100434.

Phycocyanin-Loaded Alginate-Based Hydrogel Synthesis and Characterization

Diana-Ioana Buliga  1 , Alexandra Mocanu  1   2 , Edina Rusen  1 , Aurel Diacon  3 , Gabriela Toader  3 , Oana Brincoveanu  2   4 , Ioan Călinescu  1 , Aurelian Cristian Boscornea  1
Affiliations

Phycocyanin-Loaded Alginate-Based Hydrogel Synthesis and Characterization

Diana-Ioana Buliga et al. Mar Drugs. .

Abstract

Phycocyanin was extracted from Spirulina platensis using conventional extraction (CE), direct ultrasonic-assisted extraction (direct UAE), indirect ultrasonic-assisted extraction (indirect UAE), and microwave-assisted extraction (MAE) methods at different temperatures, extraction intervals, stirring rate, and power intensities while maintaining the same algae to solvent ratio (1:15 w/v). The optimization of the extraction parameters indicated that the direct UAE yielded the highest phycocyanin concentration (29.31 ± 0.33 mg/mL) and antioxidant activity (23.6 ± 0.56 mg TE/g algae), while MAE achieved the highest purity (Rp = 0.5 ± 0.002). Based on the RP value, phycocyanin extract obtained by MAE (1:15 w/v algae to solvent ratio, 40 min, 40 °C, and 900 rpm) was selected as active compound in an alginate-based hydrogel formulation designed as potential wound dressings. Phycocyanin extracts and loaded hydrogels were characterized by FT-IR analysis. SEM analysis confirmed a porous structure for both blank and phycocyanin loaded hydrogels, while the mechanical properties remained approximately unchanged in the presence of phycocyanin. Phycocyanin release kinetics was investigated at two pH values using Zero-order, First-order, Higuchi, and Korsmeyer-Peppas kinetics models. The Higuchi model best fitted the experimental results. The R2 value at higher pH was nearly 1, indicating a superior fit compared with lower pH values.

Keywords: Spirulina platensis; microwave extraction; phycocyanin extract; release mechanism; ultrasonic extraction.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Influence of time, temperature and rotation speed on the extracted phycocyanin content using MAE and on the antioxidant activity.
Figure 2
Figure 2
Influence of time, temperature and power input on the extracted phycocyanin content and on the antioxidant activity (expressed as mg TE/g alga) using an ultrasonic probe in continuous mode.
Figure 3
Figure 3
Influence of time, temperature and power input on the extracted phycocyanin content and on the antioxidant activity (expressed as mg TE/g alga) using an ultrasonic bath.
Figure 4
Figure 4
Influence of time and temperature on the extracted phycocyanin content using CE methods and comparison with the unconventional equivalents.
Figure 5
Figure 5
FT-IR spectra of the extracts (conv—conventional, MW—MAE, US-sd—1 s ON 1 s OFF direct sonication, US-b—indirect sonication, US-sc—continuous direct sonication).
Figure 6
Figure 6
FT-IR analysis of the blank, phycocyanin loaded hydrogels and MW extracted phycocyanin.
Figure 7
Figure 7
SEM images of polymer-alginate-based structure at a magnification of 5000× (a), 10000× (b), and 20000× (c).
Scheme 1
Scheme 1
Rubber-like behavior of the polymer-based hydrogel loaded with phycocyanin.
Figure 8
Figure 8
Stress-strain plots for equilibrium swelled hydrogels submitted to compression tests.
Figure 9
Figure 9
Graphical representation of zero-order kinetics (a), first-order kinetics (b), Higuchi kinetics (c), and Korsmeyer-Peppas kinetics (d) for the phycocyanin release at pH = 7.45.
Figure 10
Figure 10
Graphical representation of zero-order kinetics (a), first-order kinetics (b), Higuchi kinetics (c), and Korsmeyer-Peppas kinetics (d) for the phycocyanin release at pH = 6.5.
Figure 11
Figure 11
Calibration curve for phycocyanin in phosphate buffer solution.
See this image and copyright information in PMC

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