Plasticizing Effects of Polyamines in Protein-Based Films

Mohammed Sabbah,C Giosafatto,Marilena Esposito,Prospero Di Pierro,Raffaele Porta,Loredana Mariniello,Carlos Regalado-Gonzales

doi:10.3390/ijms18051026

Abstract

Zeta potential and nanoparticle size were determined on film forming solutions of native and heat-denatured proteins of bitter vetch as a function of pH and of different concentrations of the polyamines spermidine and spermine, both in the absence and presence of the plasticizer glycerol. Our results showed that both polyamines decreased the negative zeta potential of all samples under pH 8.0 as a consequence of their ionic interaction with proteins. At the same time, they enhanced the dimension of nanoparticles under pH 8.0 as a result of macromolecular aggregations. By using native protein solutions, handleable films were obtained only from samples containing either a minimum of 33 mM glycerol or 4 mM spermidine, or both compounds together at lower glycerol concentrations. However, 2 mM spermidine was sufficient to obtain handleable film by using heat-treated samples without glycerol. Conversely, brittle materials were obtained by spermine alone, thus indicating that only spermidine was able to act as an ionic plasticizer. Lastly, both polyamines, mainly spermine, were found able to act as “glycerol-like” plasticizers at concentrations higher than 5 mM under experimental conditions at which their amino groups are undissociated. Our findings open new perspectives in obtaining protein-based films by using aliphatic polycations as components.

Highlights

The interest in protein-based films and coatings has increased considerably over recent years due to their advantages with respect to the conventional petroleum derived materials and to other biodegradable materials made of polysaccharides and/or lipids [1,2]
Our recent studies demonstrated the effectiveness of the aliphatic diamine putrescine, as well as of the polyamine (PA) spermidine (SPD), as alternative plasticizers for pectin edible films [9]
The changes of zeta potential and Z-average of the nanoparticles occurring in the BV protein concentrate (BVPC) film forming solutions (FFSs) were investigated at different pH values and different SPD and SPM concentrations, both in the absence and presence of GLY

Summary

Introduction

The interest in protein-based films and coatings has increased considerably over recent years due to their advantages with respect to the conventional petroleum derived materials and to other biodegradable materials made of polysaccharides and/or lipids [1,2]. One of the main additives of all bio-based edible films is the plasticizer, which is generally a small molecule such as glycerol (GLY) or sorbitol. Our recent studies demonstrated the effectiveness of the aliphatic diamine putrescine, as well as of the polyamine (PA) spermidine (SPD), as alternative plasticizers for pectin edible films [9]. Since the biosynthesis of PAs was shown to decrease with age, their content in the diet seems to be important in maintaining the full functionality of the different tissues in the elderly [19]. The very low toxicity of PAs, attested by an acute oral toxicity of 0.6 g/kg in rats [20] and by an LD50 value higher than 2 g/kg in mice [21], indicated their possible addition to film forming solutions (FFSs) in obtaining safe edible biobased materials

Methods

Results

Conclusion