Cereal seed storage proteins: structures, properties and role in grain utilization

Storage proteins account for about 50% of the total protein in mature cereal grains and have important impacts on their nutritional quality for humans and livestock and on their functional properties in food processing. Current knowledge of the structures and properties of the prolamin and globulin storage proteins of cereals and their mechanisms of synthesis, trafficking and deposition in the developing grain is briefly reviewed here. The role of the gluten proteins of wheat in determining the quality of the grain for breadmaking and how their amount and composition can be manipulated leading to changes in dough mixing properties is also discussed.

Development of zein nanoparticles coated with carboxymethyl chitosan for encapsulation and controlled release of vitamin D3

In this study, zein nanoparticles coated with carboxymethyl chitosan (CMCS) were prepared to encapsulate vitamin D3 (VD3). VD3 was first encapsulated into zein nanoparticles using a low-energy phase separation method and coated with CMCS simultaneously. Then, calcium was added to cross-link CMCS to achieve thicker and denser coatings. The nanoparticles with CMCS coatings had a spherical structure with particle size from 86 to 200 nm. The encapsulation efficiency was greatly improved to 87.9% after CMCS coating, compared with 52.2% for that using zein as a single encapsulant. The physicochemical properties were characterized by differential scanning calorimetry and Fourier transform infrared spectroscopy. Nanoparticles with coatings provided better controlled release of VD3 in both PBS medium and simulated gastrointestinal tract. Photostability against UV light was significantly improved after encapsulation. Encapsulation of hydrophobic nutrients in zein nanoparticles with CMCS coatings is a promising approach to enhance chemical stability and controlled release property.

Pickering Emulsion Gels Prepared by Hydrogen-Bonded Zein/Tannic Acid Complex Colloidal Particles

Food-grade colloidal particles and complexes, which are formed via modulation of the noncovalent interactions between macromolecules and natural small molecules, can be developed as novel functional ingredients in a safe and sustainable way. For this study was prepared a novel zein/tannic acid (TA) complex colloidal particle (ZTP) based on the hydrogen-bonding interaction between zein and TA in aqueous ethanol solution by using a simple antisolvent approach. Pickering emulsion gels with high oil volume fraction (φ(oil) > 50%) were successfully fabricated via one-step homogenization. Circular dichroism (CD) and small-angle X-ray scattering (SAXS) measurements, which were used to characterize the structure of zein/TA complexes in ethanol solution, clearly showed that TA binding generated a conformational change of zein without altering their supramolecular structure at pH 5.0 and intermediate TA concentrations. Consequently, the resultant ZTP had tuned near neutral wettability (θ(ow) ∼ 86°) and enhanced interfacial reactivity, but without significantly decreased surface charge. These allowed the ZTP to stabilize the oil droplets and further triggered cross-linking to form a continuous network among and around the oil droplets and protein particles, leading to the formation of stable Pickering emulsion gels. Layer-by-layer (LbL) interfacial architecture on the oil-water surface of the droplets was observed, which implied a possibility to fabricate hierarchical interface microstructure via modulation of the noncovalent interaction between hydrophobic protein and natural polyphenol.

Antioxidant activity of zein hydrolysates in a liposome system and the possible mode of action

Maize zein was hydrolyzed for 0.5-5 h by alcalase or papain. Protein solubility increased (P < 0.05) with the degree of hydrolysis (DH) and was higher for alcalase-hydrolyzed zein than for papain-hydrolyzed zein. The zein hydrolysates with both enzymes consisted mostly of small peptides or amino acids nondetectable by 15% acrylamide gel electrophoresis. Alcalase-hydrolyzed zein exhibited a stronger (P < 0.05) antioxidant activity than papain-hydrolyzed zein, as indicated by peroxide and thiobarbituric acid-reactive substance values in a liposome-oxidizing system. Zein hydrolysates possessed strong Cu(2+) chelation ability and marked reducing power, both of which were accentuated with hydrolysis time. The protein hydrolysates also showed strong radical-scavenging ability, which was not influenced by hydrolysis time. The antioxidant activity of alcalase-hydrolyzed zein at some specific low concentrations was close or comparable to those of butylated hydroxyanisole, alpha-tocopherol, and ascorbate. Although intact zein displayed an antioxidative effect, it was far less potent than hydrolyzed zein. The results demonstrated that enzyme-hydrolyzed zein can act as a metal ion chelator or a hydrogen donor, as well as a radical stabilizer to inhibit lipid oxidation. The effectiveness of the protein hydrolysates appeared to depend on both the concentration and the peptide/amino acid composition of the soluble protein fraction.

Reducing, radical scavenging, and chelation properties of in vitro digests of alcalase-treated zein hydrolysate

The objective of the study was to assess the antioxidant potential of alcalase-treated zein hydrolysate (ZH) during a two-stage (1 h of pepsin --> 0.5-2 h of pancreatin, 37 degrees C) in vitro digestion. Sephadex gel filtration and high-performance size exclusion chromatography were used to separate ZH into fractions. The amino acid composition, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+*)) and 1,1-diphenyl-2-picrylhydrazyl (DPPH*) free radical scavenging activity, reducing power, and Cu (2+) chelation ability were tested to determine the antioxidant efficacy of ZH. Results showed that in vitro digests of ZH contained up to 16.5% free amino acids, with short peptides (<500 Da) making up the rest of the mass. The ABTS(+*) scavenging activity of ZH was decreased by 27% (P<0.05) after pepsin treatment but was fully recovered upon subsequent pancreatin digestion, while the DPPH* scavenging activity of ZH was substantially less than ABTS(+*) scavenging activity and showed a 7-fold reduction following pancreatin treatment. The reducing power of ZH increased 2-fold (P<0.05) following pancreatin digestion when compared with nondigested ZH. The ability of ZH to sequester Cu (2+) was reduced by pepsin digestion but was reestablished following pancreatin treatment. The antioxidant activity demonstrated by in vitro digests of ZH (1-8 mg/mL) was comparable to or exceeded (P<0.05) that of 0.1 mg/mL of ascorbic acid or BHA. The results suggested that dietary zein alcalase hydrolysate may have the benefit to promote the health of the human digestive tract.

Sodium caseinate stabilized zein colloidal particles

The present work deals with the preparation and stabilization of zein colloidal particles using sodium caseinate as electrosteric stabilizer. Colloidal particles with well-defined size range (120-150 nm) and negative surface potential (-29 to -47 mV) were obtained using a simple antisolvent precipitation method. Due to the presence of caseinate, the stabilized colloidal particles showed a shift of isoelectric point (IEP) from 6.0 to around pH 5.0 and thus prevent the aggregation of zein near its native IEP (pH 6.2). The particles also showed good stability to varying ionic strength (15 mM-1.5 M NaCl). Furthermore, stabilized particles retained the property of redispersibility after drying. In vitro protein hydrolysis study confirmed that the presence of caseinate did not alter the digestibility of zein. Such colloidal particles could potentially serve as all-natural delivery systems for bioactive molecules in food, pharmaceutical, and agricultural formulations.

Fluorescence quenching study of resveratrol binding to zein and gliadin: Towards a more rational approach to resveratrol encapsulation using water-insoluble proteins

Several health benefits have been ascribed to consumption of resveratrol, a polyphenol that can be extracted from grape skins. However, its use as a nutraceutical ingredient is compromised by its low water solubility, chemical stability, and bioavailability. Encapsulation of resveratrol in protein nanoparticles can be used to overcome these issues. Fluorescence quenching experiments were used to study the interaction of resveratrol with gliadin and zein. Resveratrol interacted with both proteins, but the binding constant was higher for zein than for gliadin at 35 °C. Furthermore, binding between resveratrol and gliadin increased at higher temperatures, which was not observed for zein. Analysis of the thermodynamic parameters suggested that resveratrol-gliadin binding mainly occurs through hydrophobic interactions while the binding with zein is predominantly mediated through hydrogen bonds. These results help rationalise ingredient selection and production of protein nanoparticles and microparticles for encapsulation, protection and release of resveratrol and potentially other bioactive compounds.

Microspheres of corn protein, zein, for an ivermectin drug delivery system

A novel microsphere drug delivery system of ivermectin (IVM) using hydrophobic protein zein was prepared by the phase separation method and characterized by a scanning electron microscope and laser light scattering particle size analyzer. Releases of model drug IVM from zein microspheres, tabletted microspheres and pepsin degradation of tabletted microspheres were also performed in vitro to investigate the mechanism of model drug release. The results show that the zein microspheres and tabletted microspheres are suitable for use as a sustained-release form of IVM. The microspheres may also be useful in drug targeting system since the diameter of the microspheres is appropriate for phagocytosis by macrophages. Moreover, the release of IVM from enzymatic degraded tabletted microspheres shows a zero-order release, implying a potential application in tissue engineering for preparing scaffold, which is composed of microspheres encapsulating bioactive components for stimulating cell differentiation and proliferation.

Fabrication and characterization of antioxidant pickering emulsions stabilized by zein/chitosan complex particles (ZCPs)

Lipid peroxidation in oil-in-water (o/w) emulsions leads to rancidity and carcinogen formation. This work attempted to protect lipid droplets of emulsions from peroxidation via manipulation of the emulsions' interface framework using dual-function zein/CH complex particles (ZCPs). ZCP with intermediate wettability was fabricated via a simple antisolvent approach. Pickering emulsions were produced via a simple and inexpensive shear-induced emulsification technique. ZCP was irreversibly anchored at the oil-water interface to form particle-based network architecture therein, producing ultrastable o/w Pickering emulsions (ZCPEs). ZCPE was not labile to lipid oxidation, evidenced by low lipid hydroperoxides and malondialdehyde levels in the emulsions after thermally accelerated storage. The targeted accumulation of curcumin, a model antioxidant, at the interface was achieved using the ZCP as interfacial vehicle, forming antioxidant shells around dispersed droplets. The oxidative stability of ZCPEs was further improved. Interestingly, no detectable hexanal peak appeared in headspace gas chromatography of the Pickering emulsions. The novel interfacial architecture via the combination of steric hindrance from ZCP-based membrane and interfacial cargo of curcumin endowed the emulsions with favorable oxidative stability. This study opens a promising pathway for producing antioxidant emulsions via the combination of Pickering stabilization mechanism and interfacial delivery of antioxidant.

Basic study of corn protein, zein, as a biomaterial in tissue engineering, surface morphology and biocompatibility

The zein films, were prepared for culturing human liver cells (HL-7702) and mice fibroblast cells (NIH3T3), while the Corning microplate and polylactic acid (PLA) were chosen as controls. The surface morphology of zein films prepared by two different methods was studied by scanning electron microscope (SEM), which revealed that the zein films were composed of particles of diameter 100-500 and 500-2500 nm, respectively. The biocompatibility of zein films was assessed by attachment, extensibility and proliferation of cells on them. Our study indicated that over 60% of both HL-7702 cells and NIH3T3 cells could attach to the Corning microplate, zein films and PLA at 3h after seeding. The concentration and particle sizes for preparing zein films did not seem to affect the proliferation of the cells tested. There were no significant differences in the proliferation of both HL-7702 cells and NIH3T3 cells between the Corning microplate and two kinds of zein films, except that the zein film composed of smaller particles at the lowest concentration exhibited a very good ability for proliferation of both the cells, while PLA was a poor matrix in the latter period of the cell proliferation. This preliminary study demonstrates that zein is a promising biomaterial with good biocompatibility for the development of tissue engineering.

Fabrication of Zein/Pectin Hybrid Particle-Stabilized Pickering High Internal Phase Emulsions with Robust and Ordered Interface Architecture

Diets containing partially hydrogenated oils (PHOs) expose the human body to trans fatty acids, thus endangering cardiovascular health. Pickering high internal phase emulsions (HIPEs) is a promising alternative of PHOs. This work attempted to construct stable Pickering HIPEs by engineering interface architecture through manipulating the interfacial, self-assembly, and packing behavior of zein particles using the interaction between protein and pectin. Partially wettable zein/pectin hybrid particles (ZPHPs) with three-phase contact angles ranging from 84° to 87° were developed successfully. ZPHPs were irreversibly anchored at the oil-water interface, resulting in robust and ordered interfacial structure, evidenced by the combination of LB-SEM and CLSM. This situation helped to hold a percolating 3D oil droplet network, which facilitated the formation of Pickering HIPEs with viscoelasticity, excellent thixotropy (>91.0%), and storage stability. Curcumin in HIPEs was well protected from UV-induced degradation and endowed HIPEs with ideal oxidant stability. Fabricated Pickering HIPEs possess a charming application prospect in foods and the pharmaceutical industry.

Incorporation of food-grade antimicrobial compounds into biodegradable packaging films

Lysozyme and nisin are both antimicrobial proteins effective against gram-positive bacteria. The use of these antimicrobials in combination with chelating agents displays increased effectiveness against gram-negative bacteria. Packaging films with lysozyme or nisin incorporated into the film structure were tested separately for inhibition against Lactobacillus plantarum. Both lysozyme and nisin were used in combination with EDTA in films and were evaluated for inhibition against Escherichia coli. Two packaging film-forming methods were used to incorporate lysozyme or nisin into biodegradable protein films to determine if antimicrobial properties could be induced in the film. Heat-press and casting methods were used to produce films made from soy protein and corn zein. Circular samples were cut from the finished films, which were then placed on a bacterial lawn, incubated, and measured for any zones of inhibition. Both cast and heat-press films with added lysozyme or nisin formed excellent films and exhibited inhibition of bacterial growth. The lysozyme and nisin retained their bacteriocidal properties throughout both the heat-press and cast film-forming processes. The cast films exhibited larger inhibitory zones, as compared to the heat-press films, when the same levels of lysozyme or nisin were incorporated. L. plantarum was inhibited by films containing nisin or lysozyme. The addition of EDTA increased the inhibitory effect of films against E. coli.

Nanoscale characterization of zein self-assembly

Zein, a major protein of corn, is rich in α-helical structure. It has an amphiphilic character and is capable of self-assembly. Zein can self-assemble into various mesostructures that may find applications in food, agricultural, and biomedical engineering. Understanding the mechanism of zein self-assembly at the nanoscale is important for further development of zein structures. In this work, high-resolution transmission electron microscopy (TEM) images revealed nanosize zein stripes, rings, and discs containing a 0.35 nm periodicity, which is characteristic of β-sheet. TEM images were interpreted in terms of the transformation of original α-helices into β-sheet conformation after evaporation-induced self-assembly (EISA). The presence of β-sheet was also detected by circular dichroism (CD) spectroscopy. Zein β-sheets self-assembled into stripes, which curled into rings. Rings formed discs and eventually spheres. The formation of zein nanostructures was believed to be the result of β-sheet orientation, alignment, and packing.

Effects of multi-frequency power ultrasound on the enzymolysis and structural characteristics of corn gluten meal

The aim of this study was to investigate the effect of multi-frequency power ultrasound (sweeping frequency and pulsed ultrasound (SFPU) and sequential dual frequency ultrasound (SDFU)) on the enzymolysis of corn gluten meal (CGM) and on the structures of the major protein fractions (zein, glutelin) of CGM. The results showed that multi-frequency power ultrasound pretreatments improved significantly (P<0.05) the degree of hydrolysis and conversion rate of CGM. The changes in UV-Vis spectra, fluorescence emission spectra, surface hydrophobicity (H0), and the content of SH and SS groups indicated unfolding of zein and glutelin by ultrasound. The circular dichroism analysis showed that both pretreatments decreased α-helix and increased β-sheet of glutelin. The SFPU pretreatment had little impact on the secondary structure of zein, while the SDFU increased the α-helix and decreased the β-sheet remarkably. Scanning electron microscope indicated that both pretreatments destroyed the microstructures of glutelin and CGM, reduced the particle size of zein despite that the SDFU induced aggregation was observed. In conclusion, multi-frequency power ultrasound pretreatment is an efficient method in protein proteolysis due to its sonochemistry effect on the molecular conformation as well as on the microstructure of protein.

Peptide fractionation and free radical scavenging activity of zein hydrolysate

Alcalase-treated zein hydrolysate (ZH) was separated by gel filtration, ultrafiltration, and reversed-phase HPLC, and the scavenging activities for 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*+), 1,1-diphenyl-2-picrylhydrazyl (DPPH*), and superoxide anion (O2*-) radicals of different peptide fractions were measured to establish the antioxidant efficacy. Results showed that the ability to stabilize water-soluble free radicals (ABTS*+) by ZH components was insensitive to the peptide size, whereas that against ethanol-soluble free radicals (DPPH*) and O2*- was molecular weight dependent. Antioxidative peptides of <1 kDa were further separated by HPLC into 30 components, of which those with great hydrophobicity exhibited strong DPPH* and O2*- scavenging ability and those with intermediate hydrophobicity displayed the maximum ABTS*+ scavenging activity. Two dominant components (fractions 8 and 17) were further purified and identified by LC-PDA-ESI-MS to be Tyr-Ala and Leu-Met-Cys-His, respectively. The results demonstrated that the free radical scavenging activity of ZH depended on the radical species and was strongly related to the molecular weight and hydrophobicity of the constituting peptides.

Protein-based pickering emulsion and oil gel prepared by complexes of zein colloidal particles and stearate

This paper describes the successful preparation of a protein-based Pickering emulsion, with superior stability against both coalesence and creaming, through a novel strategy of facilitating the formation of protein particles and small molecular weight surfactant complexes; these complexes are able to overcome multiple challenges including limited solubility, poor diffusive mobility, and low interfacial loading. Soluble complexes of water-insoluble corn protein, zein colloidal particles, and surfactant sodium stearate (SS) were fabricated by simple ultrasonication. Gel trapping technology combined with SEM was applied to characterize the adsorbed particles monolayer at the oil-water interface; results revealed an enhanced adsorption and targeted accumulation of zein particles at the interface with the increase of SS concentration. Partial unfolding of zein particles modified by SS above its critical complexation concentration triggered the aggregation and close packing of particles at the oil-water interface and endowed a steric barrier against the coalescence of oil droplets. Moreover, protein-based oil gels without oil leakage were obtained by one-step freeze-drying of the zein-stabilized Pickering emulsions, which could be developed to a viable strategy for structuring liquid oils into semisolid fats without the use of saturated or trans fats.

Recent advances in food-packing, pharmaceutical and biomedical applications of zein and zein-based materials

Zein is a biodegradable and biocompatible material extracted from renewable resources; it comprises almost 80% of the whole protein content in corn. This review highlights and describes some zein and zein-based materials, focusing on biomedical applications. It was demonstrated in this review that the biodegradation and biocompatibility of zein are key parameters for its uses in the food-packing, biomedical and pharmaceutical fields. Furthermore, it was pointed out that the presence of hydrophilic-hydrophobic groups in zein chains is a very important aspect for obtaining material with different hydrophobicities by mixing with other moieties (polymeric or not), but also for obtaining derivatives with different properties. The physical and chemical characteristics and special structure (at the molecular, nano and micro scales) make zein molecules inherently superior to many other polymers from natural sources and synthetic ones. The film-forming property of zein and zein-based materials is important for several applications. The good electrospinnability of zein is important for producing zein and zein-based nanofibers for applications in tissue engineering and drug delivery. The use of zein's hydrolysate peptides for reducing blood pressure is another important issue related to the application of derivatives of zein in the biomedical field. It is pointed out that the biodegradability and biocompatibility of zein and other inherent properties associated with zein's structure allow a myriad of applications of such materials with great potential in the near future.

Three-dimensional structure of maize alpha-zein proteins studied by small-angle X-ray scattering

alpha-zeins of maize (Zea mays) that are storage proteins contain nine or ten tandem repeats comprising of about 20 amino acids. Small-angle X-ray scattering (SAXS) of alpha-zeins was measured in 70% (v/v) aqueous ethanol containing beta-mercaptoethanol or without reagent in a protein concentration range of 2.0 to 40.0 mg/ml. The overall radius of gyration of whole particles, Rg, and the corresponding radius of gyration of the cross-section, Rc, of reduced alpha-zeins are 4.00 +/- 0.03 nm and 1.39 +/- 0.05 nm, respectively, in the 70% (v/v) aqueous ethanol containing 2% (v/v) beta-mercaptoethanol. Analyses using the Rg and Rc values indicate that reduced alpha-zeins exist as asymmetric particles with the length of about 13 nm in the solution. A structural model is developed under assumption that each of tandem repeats units forms single alpha-helix and they are joined by glutamine-rich 'turns' or loops, as employed by Argos et al., [Argos, O., Pedersen, K., Marks, M.D. and Larkins, B.A. (1982) J. Biol. Chem. 257, 9984-9990] and Garratt et al. [Garratt, R., Oliva, G., Caracelli, I., Leite, A. and Arruda, P. (1993) Proteins Struc. Func. Genet. 15, 88-99], and that the longest dimension of 13 nm comes from linear stacking of the anti-parallel helices of tandem repeat in the direction perpendicular to the helical axis. The resultant model is presented by an elongated prism-like shape with an approximate axial ratio of 6:1.

Zein-Based Nanoparticles Improve the Oral Bioavailability of Resveratrol and Its Anti-inflammatory Effects in a Mouse Model of Endotoxic Shock

Resveratrol offers pleiotropic health benefits including a reported ability to inhibit lipopolysaccharide (LPS)-induced cytokine production. The aim of this work was to prepare, characterize, and evaluate a resveratrol nanoparticulate formulation based on zein. For this purpose, the oral bioavailability of the encapsulated polyphenol as well as its anti-inflammatory effects in a mouse model of endotoxic shock was studied. The resveratrol-loaded nanoparticles displayed a mean size of 307 ± 3 nm, with a negative zeta potential (-51.1 ± 1.55 mV), and a polyphenol loading of 80.2 ± 3.26 μg/mg. In vitro, the release of resveratrol from the nanoparticles was found to be pH independent and adjusted well to the Peppas-Sahlin kinetic model, suggesting a mechanism based on the combination of diffusion and erosion of the nanoparticle matrix. Pharmacokinetic studies demonstrated that zein-based nanoparticles provided high and prolonged plasma levels of the polyphenol for at least 48 h. The oral bioavailability of resveratrol when administered in these nanoparticles increased up to 50% (19.2-fold higher than for the control solution of the polyphenol). Furthermore, nanoparticles administered daily for 7 days at 15 mg/kg were able to diminish the endotoxic symptoms induced in mice by the intraperitoneal administration of LPS (i.e., hypothermia, piloerection, and stillness). In addition, serum tumor necrosis factor-alpha (TNF-α) levels were slightly lower (approximately 15%) than those observed in the control.

Structural characterization of alpha-zein

A variety of published physical measurements, computational algorithms, and structural modeling methods have been used to create a molecular model of 19 kDa alpha-zein (Z19). Zetaeins are water-insoluble storage proteins found in corn protein bodies. Analyses of the protein sequence using probability algorithms, structural studies by circular dichroism, infrared spectroscopy, small-angle X-ray scattering (SAXS), light scattering, proton exchange, NMR, and optical rotatory dispersion experiments suggest that Z19 has approximately 35-60% helical character, made up of nine helical segments of about 20 amino acids with glutamine-rich "turns" or "loops". SAXS and light-scattering experiments suggest that in alcohol/water mixtures alpha-zein exists as an oblong structure with an axial ratio of approximately 6:1. Furthermore, ultracentifugation, birefringence, dielectric, and viscosity studies indicate that alpha-zein behaves as an asymmetric particle with an axial ratio of from 7:1 to 28:1. Published models of alpha-zein to date have not been consistent with the experimental data, and for this reason the structure was re-examined using molecular mechanics and dynamics simulations creating a new three-dimensional (3D) structure for Z19. From the amino acid sequence and probability algorithms this analysis suggested that alpha-zein has coiled-coil tendencies resulting in alpha-helices with about four residues per turn in the central helical sections with the nonpolar residue side chains forming a hydrophobic face inside a triple superhelix. The nine helical segments of the 19 kDa protein were modeled into three sets of three interacting coiled-coil helices with segments positioned end to end. The resulting structure lengthens with the addition of the N- and C-terminal sections, to give an axial ratio of approximately 6 or 7:1 in agreement with recent experiments. The natural carotenoid, lutein, is found to fit into the core of the triple-helical segments and help stabilize the configuration. Molecular dynamics simulations with explicit methanol/water molecules as solvent have been carried out to refine the 3D structure.

Genomics analysis of genes expressed in maize endosperm identifies novel seed proteins and clarifies patterns of zein gene expression

We analyzed cDNA libraries from developing endosperm of the B73 maize inbred line to evaluate the expression of storage protein genes. This study showed that zeins are by far the most highly expressed genes in the endosperm, but we found an inverse relationship between the number of zein genes and the relative amount of specific mRNAs. Although alpha-zeins are encoded by large multigene families, only a few of these genes are transcribed at high or detectable levels. In contrast, relatively small gene families encode the gamma- and delta-zeins, and members of these gene families, especially the gamma-zeins, are highly expressed. Knowledge of expressed storage protein genes allowed the development of DNA and antibody probes that distinguish between closely related gene family members. Using in situ hybridization, we found differences in the temporal and spatial expression of the alpha-, gamma-, and delta-zein gene families, which provides evidence that gamma-zeins are synthesized throughout the endosperm before alpha- and delta-zeins. This observation is consistent with earlier studies that suggested that gamma-zeins play an important role in prolamin protein body assembly. Analysis of endosperm cDNAs also revealed several previously unidentified proteins, including a 50-kD gamma-zein, an 18-kD alpha-globulin, and a legumin-related protein. Immunolocalization of the 50-kD gamma-zein showed this protein to be located at the surface of prolamin-containing protein bodies, similar to other gamma-zeins. The 18-kD alpha-globulin, however, is deposited in novel, vacuole-like organelles that were not described previously in maize endosperm.

Heparin-loaded zein microsphere film and hemocompatibility

Zein was studied as a drug-eluting coating film composed of zein microspheres for cardiovascular devices (e.g. stent). In vitro 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) analysis showed that both zein film and its degraded product had better biocompatibility compared with Corning culture plate on the growth of human umbilical veins endothelial cells (HUVECs, p<0.05, n=6), and the effect of zein degraded product on HUVECs was dose-dependent. The best result was obtained at 0.3 mg/ml of the addition. The encapsulation efficiency of heparin and heparin loading varied with the amount of both zein and heparin, and the highest encapsulation efficiency (heparin 1.33 mg/ml and zein 16 mg/ml) was 22.77+/-1.33% (n=3). Scanning electron microscope (SEM) observation indicated that the zein film was made of microspheres in diameter from nano- to micrometer, which could be controlled. Sizes of heparin-loaded zein microspheres changed before and after release of heparin because of conglutination among zein microspheres. Release rate of heparin from microsphere film reached to 33.5+/-1.2% within 12 h, and began to get into subsequent "slow release" phase; about 55% of the entrapped heparin was released after 20 days. Both zein film and heparin-loaded zein microsphere film were effective in suppressing platelet adhesion, and the heparin-loaded film showed a better anticoagulation as determined with thrombin time (TT) assay. These results suggest that zein film could be used directly as a new type of coating material for its better biocompatibility with HUVECs. Moreover, the heparin-loaded zein microsphere film can significantly improve the hemocompatibility.

Mechanical properties and in vitro biocompatibility of porous zein scaffolds

A porous scaffold utilizing hydrophobic protein zein was prepared by the salt-leaching method for tissue engineering. The scaffolds possessed a total porosity of 75.3-79.0%, compressive Young's modulus of (28.2+/-6.7)MPa-(86.6+/-19.9)MPa and compressive strength of (2.5+/-1.2)MPa-(11.8+/-1.7)MPa, the percentage degradation of 36% using collagenase and 89% using pepsin during 14 days incubation in vitro. The morphology of pores located on the surface and within the porous scaffolds showed good pore interconnectivity by scanning electron microscopy (SEM). Rat mesebchymal stem cells (MSCs) could adhere, grow, proliferate and differentiate toward osteoblasts on porous zein scaffold. With the action of dexamethasone, the cells showed a relative higher activity of alkaline phosphatase (ALP) and a higher proliferating activity (p<0.05) than those of MSCs without dexamethasone.

Fabrication and Characterization of Layer-by-Layer Composite Nanoparticles Based on Zein and Hyaluronic Acid for Codelivery of Curcumin and Quercetagetin

The utilization of layer-by-layer composite nanoparticles fabricated from zein and hyaluronic acid (HA) for the codelivery of curcumin and quercetagetin was investigated. A combination of hydrophobic effects and hydrogen bonding was responsible for the interaction of zein with both curcumin and quercetagetin inside the nanoparticles. Electrostatic attraction and hydrogen bonding were mainly responsible for the layer-by-layer deposition of hyaluronic acid on the surfaces of the nanoparticles. The secondary structure of zein was altered by the presence of the two nutraceuticals and HA. The optimized nanoparticle formulation contained relatively small particles ( d = 231.2 nm) that were anionic (ζ = -30.5 mV). The entrapment efficiency and loading capacity were 69.8 and 2.5% for curcumin and 90.3 and 3.5% for quercetagetin, respectively. Interestingly, the morphology of the nanoparticles depended on their composition. In particular, they changed from coated nanoparticles to nanoparticle-filled microgels as the level of HA increased. The nanoparticles were effective at reducing light and thermal degradation of the two encapsulated nutraceuticals and remained physically stable throughout 6 months of long-term storage. In addition, the nanoparticles were shown to slowly release the nutraceuticals under simulated gastrointestinal tract conditions, which may help improve their oral bioavailability. In summary, we have shown that layer-by-layer composite nanoparticles based on zein and HA are an effective codelivery system for two bioactive compounds.