Enhanced stability of rubbery amylose-rich maize starch films plasticized with a combination of sorbitol and glycerol

Reactive extrusion fabrication of thermoplastic starch with Ca2+ heterodentate coordination structure for harvesting multiple-reusable PBAT/TPS films

Creating multiple-reusable PBAT/TPS (PT) films presents a novel solution to reduce carbon emissions from disposable packaging, addressing challenges like the high creep of PBAT and the glycerol migration of TPS. Consequently, adopting reactive extrusion to fabricate reversible cross-linking TPS with high shape memory performance, low migration, and homogeneous dispersion in PBAT matrix was a fascinating strategy. Herein, starch, glycerol and CaCl2 (calcium chloride) were extruded to fabricate TPS-Ca with Ca2+ heterodentate coordination structure and confirmed by XPS, 1H NMR and temperature-dependent FTIR. The results of DMA, dynamic rheology, flow activation energy and SEM revealed that TPS-Ca exhibited significant temperature-sensitive reversible properties and robust melt flow capability, enabling micro-nano scale dispersion in PBAT. Noteworthy, PBAT/TPS-Ca (PT-Ca) would recover 100 % length within 20 s by microwave heating after being loaded under the hygrothermal environment. Meanwhile, the migration weight of glycerol decreased from 2.5 % to 1.2 % for the heat-moisture-treated PBAT/TPS (HPT) and PBAT/TPS-Ca (HPTCa). Remarkably, the tensile strength and elongation at the break of HPT-Ca increased to 20.0 MPa and 924 %, respectively, due to reduced stress concentration sites in the phase interface. In summary, our study provides a streamlined strategy for fabricating multiple-reusable PT, offering a sustainable solution to eliminate carbon emissions linked to disposable plastic.

Recent Advances in Starch-Based Blends and Composites for Bioplastics Applications

Environmental pollution by synthetic polymers is a global problem and investigating substitutes for synthetic polymers is a major research area. Starch can be used in formulating bioplastic materials, mainly as blends or composites with other polymers. The major drawbacks of using starch in such applications are water sensitivity and poor mechanical properties. Attempts have been made to improve the mechanical properties of starch-based blends and composites, by e.g., starch modification or plasticization, matrix reinforcement, and polymer blending. Polymer blending can bring synergetic benefits to blends and composites, but necessary precautions must be taken to ensure the compatibility of hydrophobic polymers and hydrophilic starch. Genetic engineering offers new possibilities to modify starch inplanta in a manner favorable for bioplastics applications, while the incorporation of antibacterial and/or antioxidant agents into starch-based food packaging materials brings additional advantages. In conclusion, starch is a promising material for bioplastic production, with great potential for further improvements. This review summarizes the recent advances in starch-based blends and composites and highlights the potential strategies for overcoming the major drawbacks of using starch in bioplastics applications.

Tetramethylammonium Hydroxide-doped Starch Film as a Colorimetric Sensor for Trinitrotoluene Detection

A tetramethylammonium hydroxide (TMAH)-doped starch film was developed for trinitrotoluene (TNT) detection. A purple Janowsky anion was obtained from the reaction of TNT with released TMAH. When the film was used in conjunction with digital image colorimetry (DIC), rapid quantitative analysis of TNT was achieved. The Red-Green-Blue (RGB) intensities analyzed from digital photographs of the purple product were used to establish calibration curves for TNT. A wide linear range (2.5 to 50 mgL^-1) with good linearity (R² > 0.99) was achieved for the quantification of TNT. Good precision (1.73 to 3.74%RSD) was obtained for inter-day tests (n = 5). The films were applied to test four post-blast soil samples and two positive results were observed. The concentrations quantified by DIC were in good agreement with spectrophotometry. The film was able to be stored in a freezer for 3 months with <4.3% change in performance.

Adjustment of triple shellac coating for precise release of bioactive substances with different physico-chemical properties in the ileocolonic region

Formulations for the controlled release of substances in the human terminal ileum and colon are essential to target the gut microbiome and its interactions with the intestinal mucosa. In contrast to pharmaceutical enteric coatings, reliable food-grade alternatives are still scarce. Shellac coatings have been used for various active ingredients, but their stability is affected by the physicochemical properties of the encapsulated substances. It is well known, that shellac release can be modulated by an acidic subcoating. Here, we hypothesized that a triple shellac coating with an adjusted intermediate coating (acidic or alkaline) can be effectively used to counteract the differences in pH value of various encapsulated substances, allowing a precise targeting of the desired release pH value. First, the system was tested with riboflavin 5'-monophosphate sodium salt dihydrate (RMSD) as a characteristic model substance. Secondly, it was transferred to nicotinic acid (NA) and nicotinamide (NAM) as bioactive compounds with different physio-chemical properties: NAM, an alkaline crystalline and highly water-soluble substance, led to a premature release from conventional shellac microcapsules, whereas RMSD and NA with their medium solubility and neutral to acidic pH properties delayed the shellac dissolution. A precise modulation of the release profile of each substance was possible by the addition of different intermediate subcoatings: an acidic layer with citric acid counteracted the premature release of the alkaline and highly soluble NAM. In contrast, an alkaline sodium bicarbonate intermediate subcoating enhanced shellac swelling and delayed the release of NA and RMSD. In conclusion, the novel triple-layer shellac coating provides a much higher adaptability and reliability for nutritional formulations aiming at a targeted release in the ileocolonic region.

Portable and selective colorimetric film and digital image colorimetry for detection of iron

Iron is an important trace element in environmental and biological systems, the development of simple and selective methods for the determination of iron is important. In this work, completely biodegradable tapioca starch was introduced as the substrate to entrap standard chromogenic probes (1,10-phenanthroline) for fabrication of a novel colorimetric sensor for ferrous. A clear plasticized thin film from tapioca starch was fabricated inside a small plastic tube as a portable test kit. A red complex was obtained by exposing the film to a ferrous solution, while no color changes were obtained with various other ions, indicating excellent selectivity. The developed films were applied in conjunction with a digital image colorimetry for quantification of ferrous. Calculated molecular absorption of the red complex showed the widest linear range (0 to 10 mg L^-1) with good linearity (R² < 0.9934) with ferrous concentrations. The developed method provided good inter-day precision (1.75 to 3.97%RSD, 5 days 15 sensors), good accuracy (+2.35% to +4.57% relative error), and low detection limit (0.09 ± 0.01 mg L^-1). The concentrations of ferrous ion in soil and water samples quantified by the developed method were not significantly different from atomic absorption spectrophotometry at 95% confidence level. The films were stable for at least three months.

Transient Biocompatible Polymeric Platforms for Long-Term Controlled Release of Therapeutic Proteins and Vaccines

Polymer-based interpenetrating networks (IPNs) with controllable and programmable degradation and release kinetics enable unique opportunities for physisorption and controlled release of therapeutic proteins or vaccines while their chemical and structural integrities are conserved. This paper presents materials, a simple preparation method, and release kinetics of a series of long-term programmable, biocompatible, and biodegradable polymer-based IPN controlled release platforms. Release kinetics of the gp41 protein was controlled over a 30-day period via tuning and altering the chemical structure of the IPN platforms. Post-release analysis confirmed structural conservation of the gp41 protein throughout the process. Cell viability assay confirmed biocompatibility and non-cytotoxicity of the IPNs.

Supercritical CO2 foaming of thermoplastic materials derived from maize: proof-of-concept use in mammalian cell culture applications

BACKGROUND

Foams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds.

METHODOLOGY/PRINCIPAL FINDINGS

We used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams.

CONCLUSIONS/SIGNIFICANCE

We conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods.

Reduced expression of starch branching enzyme IIa and IIb in maize endosperm by RNAi constructs greatly increases the amylose content in kernel with nearly normal morphology

RNAi technology was applied to suppress the expression of starch branching enzyme IIa and IIb and to increase amylose content in maize endosperm, and stably inherited high-amylose maize lines were obtained. Amylose is an important material for industries and in the human diet. Maize varieties with endosperm amylose content (AC) of greater than 50 % are termed amylomaize, and possess high industrial application value. The high-amylose trait is controlled by multi-enzyme reaction and intricate gene-environment interaction. Starch branching enzymes are key factors for regulating the branching profiles of starches. In this paper, we report the successful application of RNAi technology for improving amylose content in maize endosperm through the suppression of the ZmSBEIIa and ZmSBEIIb genes by hairpin SBEIIRNAi constructs. These SBEIIRNAi transgenes led to the down-regulation of ZmSBEII expression and SBE activity to various degrees and altered the morphology of starch granules. Transgenic maize lines with AC of up to 55.89 % were produced, which avoided the significant decreases in starch content and grain yield that occur in high-amylose ae mutant. Novel maize lines with high AC offer potential benefits for high-amylose maize breeding. A comparison of gene silencing efficiency among transgenic lines containing different hpSBEIIRNA constructs demonstrated that (1) it was more efficient to use both ZmSBEIIa and ZmSBEIIb specific regions than to use the conserved domain as the inverted repeat arms; (2) the endosperm-specific promoter of the 27-kDa γ-zein provided more efficient inhibition than the CaMV 35S promoter; and (3) inclusion of the catalase intron in the hpSBEIIRNA constructs provided a better silencing effect than the chalcone synthase intron in the hpRNA construct design for suppression of the SBEII subfamily in endosperm.

Mechanical properties and total hydroxycinnamic derivative release of starch/glycerol/Melissa officinalis extract films

The aim of this study was to investigate the mechanical properties of starch/glycerol/Melissa officinalis, a topical drug delivery system for labial herpes treatment. Four films were prepared with different concentrations of starch, glycerol, and Melissa officinalis extract. The results revealed that increasing the glycerol concentration in the film reduced elasticity modulus and tensile strength, exhibiting a plasticizing effect. The increase in free volume resulted in increased release of hydroxycinnamic derivatives expressed as rosmarinic acid.

Controlled Release Multiparticulate Beads Coated with Starch Acetate: Material Characterization, and Identification of Critical Formulation and Process Variables

The objectives of the present investigation were to prepare and characterize starch acetate (SA) with high degree of substitution (dS) and to study its prospect as film-forming agent in a controlled-release multiparticulate drug delivery system. As a part of the development process by quality by design, the objectives also included identification of critical formulation and process variables that affect the release of a drug. SA, a relatively new polymer, was characterized because it showed good film-forming properties. SA with dS 2.9 was synthesized from corn starch by paste disruption technique. It was compared with the raw material, starch, by Fourier transform infrared spectroscopy, X-ray diffraction, and molecular mass analysis. Viscosity of SA solution increased logarithmically with the polymer concentration. At higher polymer concentrations (1.5-5.0%), the solutions showed pseudoplastic behavior. Among the plasticizers tested, triacetin and triethyl citrate yielded free films with acceptable mechanical properties. The glass transition temperature (Tg) of the films could be well controlled by these plasticizers. Unplasticized film showed a Tg of 31.8 degrees C. A trend was found that increase in triacetin concentration in SA films resulted in increase in permeability coefficient for tritiated water. Scanning electron microscopic photographs showed a clear and smooth plasticized film compared to rough unplasticized film. Dyphylline-loaded beads were coated with highly substituted SA to evaluate the main effects of the formulation and process variables on the release of the drug and to figure out the reliability of the screening design. A seven-factor, twelve-run Plackett-Burman screening design was used. The response variables were cumulative percent of drug released in 0.5, 1, 4, 8, and 12 hr. Quantitative evaluation of the design revealed that coating weight gain, plasticizer concentration, and post-drying temperature had greater influence on the drug release than the others. The main effects on drug release after 12 hr decreased in the following order: coating weight gain (-7.81), plasticizer concentration (4.96), postdrying temperature (-2.51), SA concentration (-0.80), inlet temperature (0.51), postdrying time (-0.31), and atomizing pressure (-0.28).

Alginate-magnesium aluminum silicate films: Effect of plasticizers on film properties, drug permeation and drug release from coated tablets

The effect of hydrophilic plasticizers, namely glycerin and polyethylene glycol 400 (PEG400), on physicochemical properties of sodium alginate-magnesium aluminum silicate (SA-MAS) microcomposite films was characterized and application of the films for controlling drug release from tablets was evaluated as well. The plasticizers could possibly interact with SA or MAS by formation of hydrogen bonding, as revealed using FTIR spectroscopy. PXRD studies presented that glycerin or PEG400 could intercalate into the silicate layers of MAS and higher crystallinity of the films with PEG400 was obtained. This led to a different thermal behavior of the films. Glycerin gave more flexibility of the films than PEG400. Incorporation of plasticizers into the films did not affect water uptake in acid medium, but increasing an erosion of the films because of the leaching of the plasticizers. Water vapor permeability of the films decreased with increasing amount of plasticizers in the range of 10-30% (w/w). Diffusion coefficient (D) of acetaminophen (ACT) across the films in acid medium increased with addition of the plasticizers because the leaching of plasticizers could reduce tortuosity of aqueous pore channels of the films. The tablets coated with plasticized films had a quite smooth surface without defect as shown by SEM. The ACT release profiles from the coated tablets showed a zero-order release kinetic with drug diffusion mechanism across in situ insoluble composite films in acid medium, and coating film swelling and erosion mechanism in pH 6.8 phosphate buffer. Moreover, neither the release rate nor the release pattern of the ACT coated tablets was obviously changed. The findings show that glycerin or PEG400 could improve physicochemical properties of the SA-MAS films and the plasticized films could control the drug release from tablets in gastro-intestinal condition.

Solid-state and mechanical properties of aqueous chitosan-amylose starch films plasticized with polyols

The film-forming ability of chitosan and binary mixtures of chitosan and native amylose corn starch (Hylon VII) was evaluated with free films prepared by a casting/solvent evaporation method. Unplasticized and plasticized free chitosan films in aqueous acetic acid and respective films containing a mixture of chitosan and native amylose starch in acetic acid were prepared. Glycerol, sorbitol, and i-erythritol were used as plasticizers. Solid-state and mechanical properties of the films were studied by powder x-ray diffractometry (XPRD), differential scanning calorimetry (DSC), and a materials testing machine. The films composed of a mixture of chitosan and native amylose starch in acetic acid were clear and colorless. A plasticizer concentration of 20% wt/wt (of the polymer weight) was sufficient to obtain flexible films with all samples tested. X-ray diffraction patterns and DSC thermograms indicated an amorphous state of the films independent of the type of plasticizer used. In conclusion, incorporation of native amylose corn starch into chitosan films improves the consistency and the mechanical properties of the films.