Properties and Applications of Nanoparticles from Plant Proteins

Nanoparticles from plant proteins are preferred over carbohydrates and synthetic polymeric-based materials for food, medical and other applications. In addition to their large availability and relatively low cost, plant proteins offer higher possibilities for surface modifications and functionalizing various biomolecules for specific applications. Plant proteins also avoid the immunogenic responses associated with the use of animal proteins. However, the sources of plant proteins are very diverse, and proteins from each source have distinct structures, properties and processing requirements. While proteins from corn (zein) and wheat (gliadin) are soluble in aqueous ethanol, most other plant proteins are insoluble in aqueous conditions. Apart from zein and gliadin nanoparticles (which are relatively easy to prepare), soy proteins, wheat glutenin and proteins from several legumes have been made into nanoparticles. The extraction of soluble proteins, hydrolyzing with alkali and acids, conjugation with other biopolymers, and newer techniques such as microfluidization and electrospraying have been adopted to develop plant protein nanoparticles. Solid, hollow, and core-shell nanoparticles with varying sizes and physical and chemical properties have been developed. Most plant protein nanoparticles have been used as carriers for drugs and as biomolecules for controlled release applications and for stabilizing food emulsions. This review provides an overview of the approaches used to prepare nanoparticles from plant proteins, and their properties and potential applications. The review’s specific focus is on the preparation methods and applications, rather than the properties of the proteins, which have been reported in detail in other publications.

Cellulose Nanocrystals and Corn Zein Oxygen and Water Vapor Barrier Biocomposite Films

Cellulose nanocrystals (CNC) are well-suited to the preparation of biocomposite films and packaging material due to its abundance, renewability, biodegradability, and favorable film-forming capacity. In this study, different CNC and corn zein (CZ) composite films were prepared by adding CZ to the CNC suspension prior to drying, in order to change internal structure of resulting films. Films were developed to examine their performance as an alternative water vapor and oxygen-barrier for flexible packaging industry. Water vapor permeability (WVP) and oxygen transmission rate (OTR) of the biocomposite films decreased significantly in a specific ratio between CNC and CZ combined with 1,2,3,4-butane tetracarboxylic acid (BTCA), a nontoxic cross linker. In addition to the improved barrier properties, the incorporation of CZ benefitted the flexibility and thermal stability of the CNC/CZ composite films. The toughness increased by 358%, and Young’s modulus decreased by 32% compared with the pristine CNC film. The maximum degradation temperature increased by 26 °C, compared with that of CNC film. These results can be attributed to the incorporation of a hydrophobic protein into the matrix creating hydrophobic interactions among the biocomposite components. SEM and AFM analysis indicated that CZ could significantly affect the CNC arrangement, and the film surface topography, due to the mechanical bundling and physical adsorption effect of CZ to CNC. The presented results indicate that CNC/CZ biocomposite films may find applications in packaging, and in multi-functionalization materials.

Air-Jet Spun Corn Zein Nanofibers and Thin Films with Topical Drug for Medical Applications

Diabetic patients are especially susceptible to chronic wounds of the skin, which can lead to serious complications. Sodium citrate is one potential therapeutic molecule for the topical treatment of diabetic ulcers, but its viability requires the assistance of a biomaterial matrix. In this study, nanofibers and thin films fabricated from natural corn zein protein are explored as a drug delivery vehicle for the topical drug delivery of sodium citrate. Corn zein is cheap and abundant in nature, and easily extracted with high purity, while nanofibers are frequently cited as ideal drug carriers due to their high surface area and high porosity. To further reduce costs, the 1-D nanofibers in this study were fabricated through an air jet-spinning method rather than the conventional electrospinning method. Thin films were also created as a comparative 2-D material. Corn zein composite nanofibers and thin films with different concentration of sodium citrate (1–30%) were analyzed through FTIR, DSC, TGA, and SEM. Results reveal that nanofibers are a much more effective vehicle than films, with the ability to interact with sodium citrate. Thermal analysis results show a stable material with low degradation, while FTIR reveals strong control over the protein secondary structures and hold of citrate. These tunable properties and morphologies allow the fibers to provide a sustained release of citrate and then revert to their structure prior to citrate loading. A statistical analysis via t-test confirmed a significant difference between fiber and film drug release. A biocompatibility study also confirms that cells are much more tolerant of the porous nanofiber structure than the nonporous protein films, and lower percentages of sodium citrate (1–5%) were outperformed to higher percentages (15–30%). This study demonstrated that protein-based nanofiber materials have high potential as vehicles for the delivery of topical diabetic drugs.