Abstract
The presence of catechol groups in hydrogels, either grafted to the constituting polymers or added in the gel formulation allow to increase the adhesion strength of such hydrogels. In this investigation, we add pyrocatechol (1,2-benzenediol) and pyrogallol (1,2,3-benzenetriol) in gelatin solution to form hydrogels using sodium periodate as an oxidant with the aim to induce interactions between pyrocatechol/pyrogallol and the gelatin chains. The gelation kinetics of the hydrogels as well as their adhesion strength and toughness are evaluated as a function of the concentration in NaIO4 for a constant concentration-10 mM-in pyrocatechol/pyrogallol. It came out that the addition of pyrogallol to gelatin (10% w/v) did not improve the adhesion strength on stainless steel when compared to a pristine gelatin gel. As an interesting finding, the addition of pyrocatechol to gelatin allowed for a major improvement of the adhesive strength between two stainless steel plates and allowed to stabilize the gel up to 50°C. However, the pyrogallol modified gelatin gels displayed no thermal stabilization compared to pristine gelatin. The major differences between pyrocatechol and pyrogallol modified gels are explained on the basis of the electrophilicity of the oxidized polyphenols. In addition, the self-healing behavior of the gelatin based gels was investigated as a function of their composition.
Highlights
In the last years tissue adhesives and glues (Duarte et al, 2012) have attracted major attention because they potentially allow to overcome the intrinsic drawbacks of sutures, namely damage on the neighboring tissues, foreign body reaction, aesthetic reasons and so on
It first appears that the gelation kinetics of the gelatin + pyrogallol + NaIO4 system are continuous curves (Figure 1A) whereas some marked discontinuities are observed for the gelatin + pyrocatechol + NaIO4 systems (Figure 1B)
The discontinuities observed during the monitoring of the gelation of the gelatin + pyrocatechol + NaIO4 systems, more frequent for higher concentrations in NaIO4, are not due to a permanent slippage of the hydrogels on the stainless steel plate: they constitute only transient events before restoration of the storage and loss moduli (Figure 1B)
Summary
In the last years tissue adhesives and glues (Duarte et al, 2012) have attracted major attention because they potentially allow to overcome the intrinsic drawbacks of sutures, namely damage on the neighboring tissues, foreign body reaction, aesthetic reasons and so on. Tissue adhesives have gained much interest during that time because they allow to overcome most of the drawbacks displayed by sutures (Rahimnejad and Zhong, 2017). Nitrodopamine modified 4 arm PEG was mixed with a solution containing Fe3+ cations to reach an Fe/nitrodopamine ratio equal to 3 in order to induce gelation through metal coordination. The same 4 arm PEG modified with dopamine and mixed with collagen and hydroxyapatite displayed better adhesion performance under wet conditions than cyanoacrylates (Feng et al, 2017)
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