Advances in Understanding the Molecular Structures and Functionalities of Biodegradable Zein-Based Materials Using Spectroscopic Techniques: A Review

Abstract

Zein's amphiphilic properties, film forming capability, and biodegradability make it a highly demanded polymer for fabrication of packaging materials, production of drug carrier nanoparticles, scaffolds in tissue engineering, and formation of biodegradable platforms for biosensors including microfluidic devices. Zein properties can be improved by chemical modifications, which are often analyzed with spectroscopic techniques. However, there is not a consensus on the structure of zein. For this reason, in this Review the aim is to compile the recent studies conducted on zein-based products and compare them under five main spectroscopic techniques: Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, circular dichroism (CD), X-ray diffraction (XRD) and atomic force microscopy (AFM). This Review serves as a library of recent zein studies and helps readers to have a better perception of contradictions in the literature to take their studies one step further.

High Strength Adhesives from Catechol Cross‐Linking of Zein Protein and Plant Phenolics

“…Fourier transform infrared (FTIR) spectroscopy can provide some molecular information regarding cross‐linking reactions that may have taken place during adhesive curing . Regions of particular importance are those characteristic for zein protein, catechol, and combinations thereof ( Figure ) . During catechol cross‐linking, CC, CC, CO, and CN bonds are most likely to form which may correspond to peaks observed below 1000 cm −1 .…”

“…Browning of catechol indicates oxidation through air exposure, self-polymerization to polycatechol, and cross-linking. [44] Regions of particular importance are those characteristic for zein protein, [18,45] catechol, [42] and combinations thereof (Figure 7). The exact chemistry of natural phenolic compounds can be complex [43] and encompasses a variety of degradation, crosslinking, and polymerization reactions.…”

“…Research published more recently suggests that applications of zein may also be found in high end products. For example the amphiphilic and added antibacterial properties of modified zein make this protein useful for nutrient encapsulation and drug delivery pharmaceuticals, biomedicals, food products and food packaging, and green materials chemistry . For designing strong adhesives or coatings, zein needs to be formulated for water resistance.…”

Preparation of composite zein/natural resin nanoparticles

“…Commercial zein, however, is almost exclusively α-zein, consisting of two polypeptide chains of 19 kg mol -1 and 22 kg mol -1 . 4,5 Zein is a prolamin. It is therefore insoluble in water, and soluble in concentrated aqueous ethanol (60-90 % ethanol).…”

“…The images of zein/shellac dispersions at various pHs (3)(4)(5)(6)(7)(8)(9)(10)(11) and at different zein/shellac mass ratio (1/0, 0.8/0.2, 0.5/0.5 and 0/1) are shown in Fig. 4.…”