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Updated: May 25, 2026

The Quantification of Injectability by Mechanical Testing
Published on: May 13, 2020
Characterization and evaluation of β-glucan formulations as injectable implants for protein and peptide delivery
Simone Jacobs1, Craig R Bunt, Zimei Wu
1Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany.
Context:
Injectable implants are biodegradable, syringeable formulations that are injected as liquids, but form a gel inside the body due to a change in pH, ions or temperature.
Objective:
To investigate the effect of polymer concentration, pH, ions and temperature on the gel formation of β-glucan, a natural cell-wall polysaccharide derived from barley, with particular emphasis on two-phase system formation after addition of dextran or PEG.
Materials And Methods:
Oscillation viscometry was used to evaluate the gel character by measuring flow index (N), storage (G') and loss (G") moduli. Two-phase systems were further characterized for hardness and syringeability using a texture analyzer. Finally, in vitro release characteristics were determined using Franz diffusion cells.
Results:
Oscillation viscometry revealed that only addition of dextran or PEG resulted in distinct gel formation. This was seen by a decrease in N after polymer addition. Moreover, hardness (in g) of the gels increased significantly (p < 0.001) from 3.65 ± 0.43 to 34.30 ± 8.90 (dextran) and 805.80 ± 5.30 (PEG) 24 h after polymer addition. In vitro release profiles showed significantly (p < 0.05) reduced AUC(0-8 h), k and percentage of drug released from two-phase systems compared to β-glucan dispersions, with the PEG system resulting in the lowest amount released over 8 h (15.1 ± 1.6%).
Discussion:
The unfavorable mixing enthalpy and higher water affinity of PEG resulted in the formation of a dense β-glucan gel.
Conclusion:
1.5% (w/w) β-glucan combined with PEG at a ratio of 1:3 seemed to be the most promising injectable formulation with respect to fastest gel formation, increased hardness and sustained release.
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