SPI-based Films Research Articles

Sacrificial hydrogen bonds enhance the performance of covalently crosslinked composite films derived from soy protein isolate and dialdehyde starch

Soy protein films have the advantage of being eco-friendly and renewable, but their practical applications are hindered by the mechanical properties. The exceptional tensile strength and fracture toughness of natural silk stem from sacrificial hydrogen bonds it contains that effectively dissipates energy. In this study, we draw inspiration from silk's structural principles to create biodegradable films based on soy protein isolate (SPI). Notably, composite films containing sodium lignosulfonate (LS) demonstrate exceptional strain at break (up to 153%) due to the augmentation of reversible hydrogen bonding, contrasted to films with the addition of solely dialdehyde starch (DAS). The enhancement of tensile strength is realized through a combination of Schiff base cross-linking and sacrificial hydrogen bonding. Furthermore, the incorporation of LS markedly improves the films' ultraviolet (UV) blocking capabilities and hydrophobicity. This innovative design strategy holds great promise for advancing the production of eco-friendly SPI-based films that combine strength and toughness.

Advancing soy protein isolate-ulvan film physicochemical properties and antioxidant activities through strategic high-pressure homogenization technique

Soy protein-based films often exhibit poor properties, including limited mechanical strength, stability, and bioactivity, which hinder their extensive application in the food industry, particularly in edible packaging. To enhance the properties of soy protein-based films, we employed high-pressure homogenization (HPH) to modify the soybean protein isolate (SPI) molecules and sought to cross-link SPI with ulvan polysaccharide, which possesses distinctive bioactivities. The results confirmed that soluble ulvan polysaccharides were incorporated into the cross-linking system through hydrogen bonding. Results indicated that HPH treatment enhanced SPI's solubility and surface hydrophobicity (H0), promoting hydrogen bonding and hydrophobic interactions between SPI and ulvan, as evidenced by ζ-potential and turbidity measurements. Structural and microstructural analyses of both individual SPI and composite films, using FT-IR, XRD, CD and SEM, demonstrated a high compatibility between HPH-treated SPI and ulvan. The incorporation of ulvan reduced the films' tensile strength (TS), but higher pressure significantly improved it (p < 0.05). Post-HPH modification, the films exhibited increased contact angle and swelling capacity (p < 0.05), indicating enhanced hydrophobicity. Higher pressure treatments resulted in more opaque and yellowish films, thereby diminishing ultraviolet light transmission. Thermal stability analyses, via TGA-DSC, showed that U-HSPI films had improved thermal stability compared to pure SPI films. Moreover, ulvan inclusion boosted the antioxidant capacity of SPI films, especially after HPH treatment. Overall, this study confirms that HPH modification substantially influences the properties and activities of SPI-based films, and the complex films based on SPI and ulvan with improved physicochemical and antioxidant properties exhibit a great potential in the food packaging field.

Preparation of strong soy protein composite materials with thermal conductivity and biodegradability by constructing nanophase enhanced organic-inorganic hybrid structure

The development of multifunctional films with high strength, biodegradability, and excellent thermal conductivity has drawn increasing interest. In this study, inspired by the unique hybrid structure of oysters, a nanophase-reinforced organic–inorganic hybrid structure was built using polydopamine modified boron nitride (BN@PDA), soy protein isolate (SPI), dialdehyde cellulose (DAC), and polyethylene glycol (PEG) to develop a strong soy protein film with multifunctionalities. The resultant films displayed excellent thermal diffusion ability and exhibited high tensile strength (24.03 MPa) and thermal conductivity (TC, 2.96 W·m−1·K−1) under low BN load (<0.5%). Meanwhile, the formation of non-covalent cross-linking and organic–inorganic hybrid structure endowed the films with superior flexibility. Importantly, owing to the selection of bio-based materials for preparation, the SPI-based films exhibited good biodegradability. It is believed that this study provides a creative perspective for the development of value-added multifunctional film materials and has good application prospects in advanced bio-based thermal conductive materials.

Soy protein isolate film activated by black seed oil nanoemulsion as a novel packaging for shelf-life extension of bulk bread.

This paper investigates the addition of lecithin-emulsified black seed oil (BSO) nanoemulsions (LNEO) and whey protein isolate-stabilized Pickering emulsions (WPEO) to soy protein isolate (SPI)-based films and their effect on improving the shelf life of bread slices. The half-life of antioxidant activity, water vapor permeability, biodegradability, density, color difference, and film thickness significantly increased (p < .05) when BSO was added. However, the incorporation of BSO significantly reduced the solubility, tensile strength, strain to break (except for WPEO), and transparency (p < .05) of the samples. The interaction between SPI film and BSO-loaded nanocarriers, as well as the morphological properties of films, was evaluated using FT-IR and FE-SEM. SPI-based films containing LNEO-5% and WPEO-5% were selected based on their mechanical and barrier properties. The effect of films on the shelf life of bread slices was investigated for 17 days of storage. LNEO samples obtained the most acceptable results in the bread in terms of sensory evaluation and color properties. According to the results, bread slices packed in SPI film containing LNEO-5% showed no signs of mold growth until the 17th day of storage, whereas the sample packed in a low-density polyethylene bag began to corrupt on the 6th day. This study highlights the potential of BSO-loaded SPI films as a novel active packaging for the bakery industry.

A novel active packaging film containing citronella oil: Preparation, characterization, antimicrobial activity and application in grape preservation

In this study, citronella oil (CO) was incorporated into soy protein isolate (SPI) to prepare antimicrobial protein films capable of inhibiting the growth of spoilage microorganisms on food packaging and providing effective preservation of food products. The morphological, physical and functional properties of the antimicrobial protein films were characterized and investigated by different characterization tools. The SEM results showed that the surface of the films was relatively smooth and flat. FTIR and XRD analyses indicated that CO was uniformly distributed in SPI with good compatibility. Under UV light, the films containing CO showed moderate light transmission and better UV-blocking properties than the SPI-based films. The addition of CO improves the hydrophobic property of the films, and the water content of the film containing 3 % CO is reduced to 20 % compared with that of the SPI film with 27.5 %. The DMA showed that the prepared films had good tensile, swelling and relaxation properties. Antimicrobial protein films containing 3 % CO showed high antimicrobial activity against S. aureus and E. coli. It was also found that the film with 3 % CO had a survival rate of more than 70 % and an apoptosis rate of 5.3 % for BEAS-2B cells after 48 h, indicating that such films are safe. Moreover, the film with 3 % CO showed good freshness and storage capacity with a weight loss of 44.16 % after the grapes had been packed for 7 days. These good physical properties and functional properties suggest that films containing CO have great potential for food packaging applications.

Xanthoceras sorbifolia Husk Extract Incorporation for the Improvement in Physical and Antioxidant Properties of Soy Protein Isolate Films.

With the increasing awareness of ecological and environmental protection, the research on eco-friendly materials has experienced a considerable increase. The objective of our study was to explore a novel soy protein isolate (SPI) film functionalized with antioxidants extracted from Xanthoceras sorbifolia husk (XSHE) as bio-based active packaging films. The films were evaluated in light of their structure, physical machinery, and antioxidant performance using advanced characterization techniques. The FTIR and microscopy results revealed the hydrogen-bond interaction between the SPI and XSHE and their good compatibility, which contributed to the improvement in various properties of the composite films, such as tensile strength (TS), UV blocking, and the water barrier property. As the XSHE content increased to 5%, the TS of the films dramatically increased up to 7.37 MPa with 47.7% and the water vapor permeability decreased to 1.13 × 10-10 g m m-2 s-1 Pa-1 with 22.1%. Meanwhile, the introduction of XSHE caused further improvement in the antioxidant capacity of films, and the release of active agents from films was faster and higher in 10% ethanol than it was in a 50% ethanol food simulant. Overall, SPI-based films functionalized with XSHE demonstrated promising potential applications in food packaging.

Effects of polyvinyl alcohol incorporation on the physical and antioxidant properties of soy protein isolate/Xanthoceras sorbifolia husk extract active films

The design and development of biomass-based films have attracted extensive attention with the increasing demand for novel biodegradable food packaging materials. Herein, soy protein isolate (SPI) and the extracts of the waste Xanthoceras sorbifolia husk were mixed to fabricate composite films via a casting method. Polyvinyl alcohol (PVA) was further incorporated to establish ternary composite films, and the influence of PVA content (0%, 0.2%, 0.4%, 0.6%, and 0.8% w/v) on the film performance was well evaluated. The characterizations including scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), and X-ray diffraction (XRD) demonstrated the excellent compatibility and intermolecular interactions among the components after introducing appropriate PVA. Compared with the control film, the water barrier, mechanical and UV-blocking properties of the composite films were greatly improved due to the presence of PVA, especially at 0.6%. The tensile strength and the water vapor permeability of the reinforced films with 0.6% PVA addition was 10.83 MPa and 0.95 × 10−10 g m m−2 s−1 Pa−1, increased by 47% and reduced by 16%, respectively. The composite films also exhibited excellent DPPH and ABTS radical scavenging capacity. Thus, the functional SPI-based films provide a feasible route for the fabrication of composite films applied for potential active packaging applications.

Insight into the formation mechanism of soy protein isolate films improved by dialdehyde starch with different degrees of aldehyde substitution

Protein and polysaccharide materials are gaining attention as potential solutions for environmental pollution and reducing dependence on fossil resources. In this research, films were formed by crosslinking soy protein isolate (SPI) with dialdehyde starch (DAS) of varying aldehyde group contents. The aim was to evaluate the influence of the content/degree of aldehyde groups of DAS upon the basic properties of SPI-based films and propose a formation mechanism. Results showed that adding DAS improved the hydrophobicity, UV-blocking properties, and thermal stability of the films. The tensile strength of the film was increased from 2.95 to 7.94 MPa. The reaction between DAS and SPI formed Schiff base reactions and covalent imine bonds (CN), along with a network of hydrogen bonds. In addition, atomic force microscopy indicated that the addition of DAS resulted in an increase in the surface roughness of the films to 19.2 nm, favoring hydrophobicity and UV-barrier properties. These results provide a solid theoretical basis for further research on SPI-DAS composites.

Development and evaluation of soybean protein isolate–based antibacterial nanocomposite films containing nano-TiO2

Designing soy protein isolate (SPI)-based composite films with great antibacterial properties and high ultraviolet (UV)-shielding remains an intractable challenge. This study aimed to blend nano-TiO2 particles (1%−4% w/w SPI) with soybean protein isolate (SPI) to form a composite film using the casting method to improve the properties of the SPI-based film. Dynamic light scattering showed that nano-TiO2 was well-embedded in the SPI in the film solution. Scanning electron microscopy, x-ray diffraction and fourier-transform infrared spectroscopy also revealed a strong intermolecular interaction between nano-TiO2 and SPI. Further, nano-TiO2 (3% w/w SPI) composite had obviously enhanced color and ultraviolet-shielding properties compared with the SPI film. Is hydrophobicity contact angle was two times that of SPI film, the tensile strength increased twofold, and the water vapor permeability was one-third of the SPI film. Additionally, the bacteriostatic effects of nano-TiO2 on Escherichia coli (E. coli) and Bacillus cereus (B. cereus) were concentration- and time-dependent. Collectively, an appropriate increase in the nano-TiO2 content (3%) significantly improved the properties and promisingly extended the shelf life of SPI-based films prone to microbial spoilage, suggesting its potential application in the packaging industry.

Influence mechanism of wheat bran cellulose and cellulose nanocrystals on the storage stability of soy protein isolate films: Conformation modification and molecular interaction perspective

This study aims to elucidate the changes and corresponding mechanisms of storage stability of soy protein isolate (SPI) films strengthened via wheat bran cellulose (WBC) and cellulose nanocrystals (CNC). The incorporation of WBC and CNC improved the mechanical strength, water resistance, water vapor and visible light barrier abilities of stored SPI-based films to varying degrees. Higher crystallinity and lower water mobility were observed in the composite films. WBC molecules reduced the irregular pores and cracks within the internal structure of the film through physical filling and non-covalent interactions, involving hydrogen bond and van der Waals force. In contrast, uniformly distributed CNC cross-linked with amino acid residues at specific binding sites under non-covalent forces. Furthermore, CNC induced the secondary conformation of proteins to transform from α-helix to β-sheet and enhanced the hydrophobic interaction, which promoted the establishment of a stable network structure and thus extended the storage stability of SPI-based films.

Research on the Properties of Zein, Soy Protein Isolate, and Wheat Gluten Protein-Based Films Containing Cellulose Nanocrystals.

Plant protein films are a research hotpot in the current food packaging field for their renewable and bio-compatibility, and further improving the physicochemical properties of plant protein films in combination with biodegradable materials is of great significance. In this study, we selected cellulose nanocrystals (CNC) to modify the protein films with soybean protein isolate (SPI), wheat gluten protein (WGP), and Zein, and the physicochemical properties were studied. The results showed that the hardness and opacity of Zein-based films decreased by 16.61% and 54.12% with the incorporation of CNC, respectively. The SPI-based films performed with lower hardness and higher tensile strength. The thickness and opacity of WGP-based films increased by 39.76% and 214.38% after combination with CNC, respectively. Accordingly, this study showed that CNC could largely modify the physicochemical properties of the plant protein films, which provided a reference for the preparation of modified plant protein films using biodegradable materials.

Investigation of Potential Use of Soybean Protein Isolate–Chinese Bayberry Tannin Extract Cross-Linked Films in Packaging Applications

The possibility of using commercial bayberry tannin (BT) from a Chinese source as a cross-linker and functional additive to develop soybean protein isolate (SPI)-based films was explored in this study by using the solvent casting method. In particular, the impacts of BT loading on the tensile strength, microstructure, thermal stability, water resistance and antioxidant capacity were fully investigated. The results reveal that SPI incorporated with BT yielded a phenolic–protein hybrid whose relevant films exhibited an improvement in tensile strength of around two times greater compared with native SPI as a result of the formed interactions and covalent cross-links, which could be proven using FTIR spectroscopy. The introduction of BT also led to the compact microstructure of SPI–BT films and enhanced the thermal stability, while the water vapor permeability was reduced compared with the control SPI film, especially at high loading content of tannin. Additionally, the use of BT significantly promoted the antioxidant capacity of the SPI-based films according to DPPH radical scavenging assay results. On this basis, Chinese bayberry tannin is considered a promising natural cross-linker and multifunctional additive that can be dedicated to developing protein-derived films with antioxidant activity for food packaging applications.

Tough and strong biomimetic soy protein films with excellent UV-shielding performance

To develop strong and tough bio-based composite films as replacements for synthetic polymer films is challenging. Based on the strong adhesion of the comb-like structure of geckos’ feet or pressure-sensitive resins on substrates, a comb-like polymer-aminated dialdehyde starch (A-DAS) was designed and prepared from polyamide polyamine polymer and dialdehyde starch via a Schiff-based reaction, and then combined with soy protein isolate (SPI) to develop a protein-based film. The comb-like A-DAS exhibited strong adhesion with SPI molecules by forming multiple hydrogen bonds, which created a noncovalent network that improved both the strength and toughness of the resultant film. The results showed that after integrating A-DAS (SPI:A-DAS weight ratio of 2:1), the tensile strength of the film dramatically increased by 1072.2% to 25.09 MPa, which is markedly better than that of other reported protein-based films. The toughness of the SPI/A-DAS film increased to 16.74 MJ/m 3 . Notably, the modified film could block 100% of the ultraviolet transmittance (<400 nm) owing to the imine group in A-DAS. This strategy offers a simple and effective way to construct strong and tough composite materials with ultraviolet-barrier performance, indicating potential applications in tissue engineering, hydrogels, and coating modification. • A high-performance SPI-based film was prepared inspired by gecko feet and PSAs. • Strong hydrogen bonds promoted the toughness of the SPI-based film. • The tensile strength and toughness of the films improved by 1072.2% and 307.3%. • The SPI-based film exhibited UV-shielding properties for packaging.

Eco-friendly soy protein isolate-based films strengthened by water-soluble glycerin epoxy resin

Soy protein isolate (SPI) have very scanty applications due to its weak resistance towards water and minimal strength. Chemical cross-linking modification is the most potent way to enhance performance of soy protein, meanwhile, glycerin is generally needed to be added as toughening agent in the preparation of soy protein adhesive. Glycerin epoxy resin (GER) is a water-soluble epoxy resin can be used to reduce volume of glycerin (GLY) addition throughout production of SPI-based films. It also ameliorates tensile strength and water resisting property of films. Mechanical performance of films was examined with universal testing machine. Compared with the untreated SPI-based film, the addition amounts of GER and GLY were 45% and 5% of SPI, respectively, the tensile modulus and tensile strength of SPI-based films were increased by 245.6% and 180.0%, respectively, as well as tensile strength reached 11.2 MPa. The elongation at break was lowered 50.6%, but the strain still close to 150.0%. The 24-h water absorption of SPI-based films was reduced by 51.5%, from 194.2% to 94.1% with GER addition for 35% of SPI. In addition, GER and SPI have stunning compatibility, GER may have promising application prospects in the industrial preparation of soy protein adhesives.

"Green" Flexible Electronics: Biodegradable and Mechanically Strong Soy Protein-Based Nanocomposite Films for Human Motion Monitoring.

Soy protein isolate (SPI) is envisioned as a promising alternative to fabricate "green" flexible electronics, showing great potential in the field of flexible wearable electronics. However, it is challenging to simultaneously achieve conductive film-based human motion-monitoring strain sensors with reliable fatigue resistance, robust mechanical property, environmental degradability, and sensing capability of human motions. Herein, we prepared a series of SPI-based nanocomposite films by embedding a surface-hydroxylated high-dielectric constant inorganic filler, BaTiO3, (HBT) as interspersed nanoparticles into a biodegradable SPI substrate. In particular, the fabricated film comprising 0.5 wt % HBT and glycerin (GL), namely, SPI-HBT0.5-GL0.5, presents multifunctional properties, including a combination of excellent toughness, tensile strength, conductivity, translucence, recyclability, and excellent thermal stability. Meanwhile, this multifunctional film could be simply degraded in phosphate buffered saline solution and does not cause any pollution to the environment. Attractively, wearable sensors prepared with this particular material (SPI-HBT0.5-GL0.5) displayed excellent biocompatibility, prevented the occurrence of an immune response, and could accurately monitor various types of human joint motions and successfully remain operable after 10,000 cycles. These properties make the developed SPI-based film a great candidate in formulating biobased and multifunctional wearable electronics.

Microwave induced construction of multiple networks for multifunctional soy protein-based materials

Petroleum-based plastics are useful but pose a great threat to the environment and human health. It is challenged for developing alternative materials to completely replace those plastics. In this work, soy protein (SPI) based films with excellent mechanical, biodegradable, and excellent UV-shielding were developed. The SPI-based films were crosslinked by ester bonds under microwave induction to form a strong chemical bond network, and by hyperbranched polyamide ester to form a large amount of hydrogen bonding interactions, realizing both high strength and toughness. The strong covalent bond crosslinks maintain the integrity of the network during the stretching process, and the weakly interactions from hydrogen bonds dissipate stretching energy. The material exhibits super strong tensile strength at 20.3 MPa and superior toughness at 16.6 MJ m−3. Furthermore, the material owns the features of biodegradable and excellent UV-shielding. It may be used as sustainable packing material due to its biodegradable feature and low-cost processing.

Evaluation of Interactions Between Carboxymethylcellulose and Soy Protein Isolate and their Effects on the Preparation and Characterization of Composite Edible Films

Interactions between carboxymethylcellulose (CMC) and soy protein isolate (SPI) were assessed to determine their effects on the physicochemical and morphological properties of SPI-based films. The protein-polysaccharide interactions were investigated by measuring zeta potentials, showing a dependence on the pH, ionic strength and polysaccharide concentration. SPI-based films were prepared with different CMC concentrations (0–0.5%) at pH 11 and the pH of biopolymer coacervation (pHc). The addition of CMC improved mechanical strengths of all films, but films prepared at pHc showed a reduction in percentage of elongation at break, becoming more brittle than at pH 11. The water vapor permeability did not show a strict dependence on the CMC concentration or pH, while the oxygen permeability of films prepared at pH 11 decreased with the addition of CMC until reaching a minimal value at 0.375% CMC. These results reveal the significant effects of SPI-CMC interactions on the formation and properties of films, indicating the potential of this approach to better tailor edible films and coatings for specific applications.

Preparation, characterization and application of SPI-based blend film with antioxidant activity

To investigate the effect of ferulic acid (0, 2.0, 4.0, 6.0 and 8.0 % w/w) as antioxidant and cross-linking agent on the properties of soy protein isolate (SPI)/cellulose nanofiber/ferulic acid blend films, the mechanical properties, barrier properties, antioxidant activity of the blend films were evaluated, and its Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were characterized. Pork wrapped with different blend films were further evaluated with peroxide value and thiobarbituric acid reacting substances. The result showed that the elongation at breakage, water vapor permeability and oxygen permeability of the blend films with 4.0 % ferulic acid decreased by 69.76 %, 90.91 % and 77.55 %, respectively. Moreover, the blend film effectively delayed lipid oxidation process of pork by scavenging free radicals and blocking water, oxygen and ultraviolet light. This study provides a theoretical basis for SPI-based film to prolonging the shelf life of pork.

Hydroxypropyl methylcellulose or soy protein isolate‐based edible, water‐soluble, and antioxidant films for safflower oil packaging

Edible, water-soluble, heat-sealable, and antioxidant films were developed from hydroxypropyl methylcellulose (HPMC) or soy protein isolate (SPI) and applied as safflower oil packaging. A 0.1 or 0.2% DL-α-tocopherol acetate (VE) and 0 or 0.25% oleic acid were added into film formulations to provide antioxidant and hydrophobic properties, respectively, using a 23 factorial design. Films were analyzed for appearance, microstructure, water and oil sensitivity, mechanical properties, and antioxidant functionality. Subsequently, a completely randomized design was implemented for incorporating 2, 4, or 6% cellulose nanocrystals (CNCs, w/w dry weight polymer) for improving film mechanical and barrier properties. HPMC-based films achieved full dissolution in water at <55 °Cunder 5min, while SPI-based films disintegrated in water up to 90 °C. Oleic acid significantly increased (P <0.05) heat sealability of SPI film from 78 to 143N/m and elongation at break from 36% to 88%, but decreased tensile strength and heat sealability of HPMC films by 55% and 41%, respectively. As safflower oil packaging, after 60 days of storage at 35 °C, oil contained in SPI-based pouch had the lowest peroxide values, 8.1 ± 0.9mEq/kg. Based on barrier, mechanical, and antioxidant capacity evaluations, HPMC film with 0.1% VE and SPI film with 0.25% oleic acid and 0.1% VE were incorporated with CNC. SPI/CNC films did not show observable trends, but HPMC/2% CNC film exhibited significantly improved mechanical and barrier properties, with oxygen permeability of 5.0mL mm/m2 day kPa. The developed films are a promising packaging alternative to decrease plastic waste, extend shelf life of lipid-based foods, and increase consumer convenience. PRACTICAL APPLICATION: Individually packaged, single-use pouches of sauce or oil are common for seasoning instant and frozen foods, creating unnecessary plastic waste. Edible, water-soluble packaging with antioxidant functionality would reduce plastic waste, extend shelf life by preventing oxidation, and increase consumer convenience. The biopolymeric films and pouches developed in this study have unique properties from water solubility across a wide range of temperatures, resistance to oil, high oxygen barrier, and good heat sealability, providing a variety of potential applications for promoting sustainable food packaging.

Self-healable and biodegradable soy protein-based protective functional film with low cytotoxicity and high mechanical strength

Soy protein isolate (SPI) is a natural organic polymer, being used to prepare protective functional materials due to its sustainability, abundance, and easy processing. However, the protective effect of unmodified SPI films is significantly limited due to its poor mechanical properties, irreversible damage, and monotone functionality. Herein, high-flowability polyethyleneimine (PEI) was used to improve the dynamic properties of the protein matrix and cross-linking, and the phenolic hydrogen bonding of polydopamine (PDA) was used to develop a facile strategy for fabricating SPI-based films with satisfactory self-healing properties, high strength, excellent UV barrier performance, and remarkable fluorescence for the heavy metal detection. PEI disrupted the strong hydrogen bonds between protein molecules, causing them to be aggregated due to the PDA cross-linking. Thus, the phenols of PDA formed hydrogen bonds and constructed a reversible network, which endowed the SPI-PEI-PDA films with excellent self-healing properties. Because the hyperbranched PEI imparted the films with more cavities, the microcracks caused by external forces were blunted. Due to the further PDA crosslinking, the SPI-PEI-PDA films exhibited high mechanical strength. The SPI-PEI-PDA films also showed outstanding UV barrier performance and fluorescence properties for the heavy metal detection due to the bionic melanin-like characteristic of PDA andthe Michael addition reaction between the reactants. Additionally, SPI-PEI-PDA films demonstrated the low toxicity in vitro and in vivo, as well as the favorable biodegradability. These films improved the adaptability and safety of protective materials and could greatly promote functionalapplications of other biopolymer-based materials.