Polymers

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10 pages, 1647 KiB

Open AccessArticle

Enzymatic Synthesis of Formate Ester through Immobilized Lipase and Its Reuse

by Yesol Baek, Jonghwa Lee, Jemin Son, Taek Lee, Abdus Sobhan, Jinyoung Lee, Sang-Mo Koo, Weon Ho Shin, Jong-Min Oh and Chulhwan Park

Polymers 2020, 12(8), 1802; https://doi.org/10.3390/polym12081802 - 11 Aug 2020

Cited by 24 | Viewed by 3720

Abstract

Octyl formate is an important substance used in the perfume industry in products such as cosmetics, perfumes, and flavoring. Octyl formate is mostly produced by chemical catalysts. However, using enzymes as catalysts has gathered increasing interest due to their environment-friendly proprieties. In the [...] Read more.

Octyl formate is an important substance used in the perfume industry in products such as cosmetics, perfumes, and flavoring. Octyl formate is mostly produced by chemical catalysts. However, using enzymes as catalysts has gathered increasing interest due to their environment-friendly proprieties. In the present study, we aimed to identify the optimal conditions for the synthesis of octyl formate through immobilized enzyme-mediated esterification. We investigated the effects of enzymatic reaction parameters including the type of immobilized enzyme, enzyme concentration, molar ratio of reactants, reaction temperature, and type of solvent using the optimization method of one factor at a time (OFAT). The maximum conversion achieved was 96.51% with Novozym 435 (15 g/L), a 1:7 formic acid to octanol ratio, a reaction temperature of 40 °C, and with 1,2-dichloroethane as solvent. Moreover, we demonstrated that the Novozym 435 can be reused under the optimal conditions without affecting the octyl formate yield, which could help reduce the economic burden associated with enzymatic synthesis. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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16 pages, 2944 KiB

Open AccessArticle

Revealing the Influence of the Degumming Process in the Properties of Silk Fibroin Nanoparticles

by Guzmán Carissimi, A. Abel Lozano-Pérez, Mercedes G. Montalbán, Salvador D. Aznar-Cervantes, José Luis Cenis and Gloria Víllora

Polymers 2019, 11(12), 2045; https://doi.org/10.3390/polym11122045 - 09 Dec 2019

Cited by 47 | Viewed by 4576

Abstract

Several studies have stated that the process used for sericin removal, or degumming, from silk cocoons has a strong impact in the silk fibroin integrity and consequently in their mechanical or biochemical properties after processing it into several biomaterials (e.g. fibers, films or [...] Read more.

Several studies have stated that the process used for sericin removal, or degumming, from silk cocoons has a strong impact in the silk fibroin integrity and consequently in their mechanical or biochemical properties after processing it into several biomaterials (e.g. fibers, films or scaffolds) but still, there is a lack of information of the impact on the features of silk nanoparticles. In this work, silk cocoons were degummed following four standard methods: autoclaving, short alkaline (Na₂CO₃) boiling, long alkaline (Na₂CO₃) boiling and ultrasounds. The resultant silk fibroin fibers were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate and used for nanoparticle synthesis by rapid desolvation in polar organic solvents. The relative efficiencies of the degumming processes and the integrity of the resulting fibroin fibers obtained were analyzed by mass loss, optical microscopy, thermogravimetric analysis, infrared spectroscopy and SDS-PAGE. Particle sizes and morphology were analyzed by Dynamic Light Scattering and Field Emission Scanning Electronic Microscopy. The results showed that the different treatments had a remarkable impact on the integrity of the silk fibroin chains, as confirmed by gel electrophoresis, which can be correlated with particle mean size and size distribution changes. The smallest nanoparticles (156 ± 3 nm) and the most negative Z potential (−30.2 ± 1.8 mV) were obtained with the combination of long treatment (2 h) of boiling in alkaline solution (Na₂CO₃ 0.02 eq/L). The study confirms that parameters of the process, such as composition of the solution and time of the degumming step, must be controlled in order to reach an optimum reproducibility of the nanoparticle production. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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12 pages, 5543 KiB

Open AccessArticle

Fabrication of Silk Fibroin/Graphene Film with High Electrical Conductivity and Humidity Sensitivity

by Haoran Zhang, Juntao Zhao, Tieling Xing, Shenzhou Lu and Guoqiang Chen

Polymers 2019, 11(11), 1774; https://doi.org/10.3390/polym11111774 - 28 Oct 2019

Cited by 29 | Viewed by 4787

Abstract

Silk fibroin (SF) is a natural material with good biocompatibility and excellent mechanical properties, which are complementary to graphene with ultrahigh electrical conductivity. In this study, to maximally combine graphene and silk fibroin, a well-dispersed silk fibroin/graphene suspension was successfully prepared in a [...] Read more.

Silk fibroin (SF) is a natural material with good biocompatibility and excellent mechanical properties, which are complementary to graphene with ultrahigh electrical conductivity. In this study, to maximally combine graphene and silk fibroin, a well-dispersed silk fibroin/graphene suspension was successfully prepared in a simple and effective way. Then we prepared a flexible conductive SF/graphene film with a minimum resistance of 72.1 ± 4.7 Ω/sq by the casting method. It was found that the electrical conductivity of the SF/graphene film was related to the water content of the film, and the variation was more than 200 times. Therefore, it will play an important role in the field of humidity sensors. It also has excellent mechanical properties in both wet and dry states. These unique features make this material a promising future in the fields of biomedical applications, wearable sensors, and implantable internal sensors. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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17 pages, 3948 KiB

Open AccessArticle

Tailoring Cod Gelatin Structure and Physical Properties with Acid and Alkaline Extraction

by Svetlana R. Derkach, Yuliya A. Kuchina, Andrey V. Baryshnikov, Daria S. Kolotova and Nikolay G. Voron’ko

Polymers 2019, 11(10), 1724; https://doi.org/10.3390/polym11101724 - 21 Oct 2019

Cited by 45 | Viewed by 4663

Abstract

Gelatin (G) was extracted from the skin of Atlantic cod at different pH of the aqueous phase (pH 3, 4, 5, 8 and 9) and at a temperature of 50 ± 1 °C. The yield of gelatin (G3, G4, G5, G8, and G9, [...] Read more.

Gelatin (G) was extracted from the skin of Atlantic cod at different pH of the aqueous phase (pH 3, 4, 5, 8 and 9) and at a temperature of 50 ± 1 °C. The yield of gelatin (G3, G4, G5, G8, and G9, respectively) was 49–55% of the dry raw material. The influence of extraction pH on the physicochemical and functional properties of gelatin was studied. Sample G5 was characterized by higher protein content (92.8%) while lower protein content was obtained for sample G3 (86.5%) extracted under more aggressive conditions. Analysis of the molecular weight distribution showed the presence of α- and β-chains as major components; the molecular weight of the samples ranged between 130 and 150 kDa, with sample G5 having the highest molecular weight. IR spectra of all samples had absorption bands characteristic of fish gelatin. The study of the secondary structure demonstrated higher amounts of ordered triple collagen-like helices for G5 extracted under mild conditions. Accordingly, sample G5 formed gels with high values for the storage modulus and gelling and melting temperatures, which decrease as pH changes into acidic or alkaline regions. In addition, the differential scanning calorimetry data showed that G5 had a higher glass transition temperature and melting enthalpy. Thus, cod skin is an excellent source of gelatin with the necessary physicochemical and functional properties, depending on the appropriate choice of aqueous phase pH for the extraction. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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16 pages, 3928 KiB

Open AccessArticle

Study on the Preparation and Conjugation Mechanism of the Phosvitin-Gallic Acid Complex with an Antioxidant and Emulsifying Capability

by Bin Jiang, Xiaojing Wang, Linlin Wang, Shuang Wu, Dongmei Li, Chunhong Liu and Zhibiao Feng

Polymers 2019, 11(9), 1464; https://doi.org/10.3390/polym11091464 - 07 Sep 2019

Cited by 3 | Viewed by 2422

Abstract

To develop a novel emulsifier with an antioxidant capacity, a phosvitin-gallic acid (Pv–GA) complex was prepared via a free-radical method. This emulsifier characterizes some key technologies. Changes in the molecular weight of the Pv–GA complex were analyzed by sodium dodecyl sulfate polyacrylamide gel [...] Read more.

To develop a novel emulsifier with an antioxidant capacity, a phosvitin-gallic acid (Pv–GA) complex was prepared via a free-radical method. This emulsifier characterizes some key technologies. Changes in the molecular weight of the Pv–GA complex were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) and the matrix-assisted laser desorption/ionization time of light mass spectrometry (MALDI-TOF-MS). Fourier transform infrared spectroscopy (FTIR) indicated that C=O, C–N and N–H groups were also likely to be involved in the formation of the complex. A redshift was obtained in the fluorescence spectrogram, thereby proving that the covalent combination of Pv and GA was a free radical-forming complex. The results indicated that Pv and GA were successfully conjugated. Meanwhile, the secondary structure of Pv showed significant changes after conjugation with GA. The antioxidant activity and emulsifying properties of the Pv–GA complex were studied. The antioxidant activity of the Pv–GA complex proved to be much higher than that of the Pv, via assays of the scavenging activities of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals and because of their ability to reduce power. The emulsification activity of the Pv–GA complex was also slightly higher than that of Pv. To function with the most demanding antioxidant and emulsification activities, the optimum conjugation condition was Pv (5 mg/mL) conjugated 1.5 mg/mL GA. Furthermore, the mechanism of Pv–GA conjugation was studied. This study indicated that GA could quench the inner fluorescence of Pv, and this quenching was static. There was a strong interaction between GA and Pv, which was not obviously affected by the temperature. Furthermore, several binding sites were close to 1, indicating that there was an independent class of binding sites on Pv for GA at different temperatures. The conjugation reaction was a spontaneous reaction, and the interaction forces of GA and Pv were hydrogen bonds and van der Waals force. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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16 pages, 2204 KiB

Open AccessArticle

Ultrasonic Thermal-Assisted Extraction of Phosvitin from Egg Yolk and Evaluation of Its Properties

by Bin Jiang, Linlin Wang, Xiaojing Wang, Shuang Wu, Dongmei Li, Chunhong Liu and Zhibiao Feng

Polymers 2019, 11(8), 1353; https://doi.org/10.3390/polym11081353 - 15 Aug 2019

Cited by 12 | Viewed by 3485

Abstract

Phosvitin (Pv) is the principal phosphoprotein in chicken egg yolk and the most highly phosphorylated protein in nature. Pv is a good natural food antioxidant and emulsifier. However, the current extraction methods present disadvantages of complicated operation and are time-consuming. In this paper, [...] Read more.

Phosvitin (Pv) is the principal phosphoprotein in chicken egg yolk and the most highly phosphorylated protein in nature. Pv is a good natural food antioxidant and emulsifier. However, the current extraction methods present disadvantages of complicated operation and are time-consuming. In this paper, Pv was extracted from the egg yolk by ultrasonic thermal-assisted extraction (UTAE). The effects of heating time, ultrasonic power and ultrasonic time on the extraction of Pv were investigated by a single factor. The purity of Pv, ratio of nitrogen to phosphorus (N/P), and activity were used as evaluation indexes. An efficient extraction of Pv was achieved when the sample was heated for 15 min at 80 °C and then processed for 10 min of ultrasonic treatment with an ultrasonic power of 600 W. Under optimal conditions, the purity and activity of Pv were 80% and 98%, respectively, whereas the ratio of N/P was 3.1. The obtained Pv was identified by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), Fluorescence analyses, fourier-transform infrared (FT-IR), and liquid chromatography-nanoelectrospray ionization mass spectrometry (Nano LC-ESI-MS/MS) analysis. The results showed there is no significant difference in the properties of Pv obtained by UTAE and Pv standard. The developed extraction approach is a simple, industrial compatible method without the use of any organic solvents. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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12 pages, 4513 KiB

Open AccessArticle

Steady-State Behavior and Endothelialization of a Silk-Based Small-Caliber Scaffold In Vivo Transplantation

by Helei Li, Yining Wang, Xiaolong Sun, Wei Tian, Jingjing Xu and Jiannan Wang

Polymers 2019, 11(8), 1303; https://doi.org/10.3390/polym11081303 - 03 Aug 2019

Cited by 16 | Viewed by 3390

Abstract

A silk-based small-caliber tubular scaffold (SFTS), which is fabricated using a regenerated silk fibroin porous scaffold embedding a silk fabric core layer, has been proved to possess good cell compatibility and mechanical properties in vitro. In this study, the endothelialization ability and the [...] Read more.

A silk-based small-caliber tubular scaffold (SFTS), which is fabricated using a regenerated silk fibroin porous scaffold embedding a silk fabric core layer, has been proved to possess good cell compatibility and mechanical properties in vitro. In this study, the endothelialization ability and the steady-state blood flow of SFTSs were evaluated in vivo by implanting and replacing a common carotid artery in a rabbit. The results of the color doppler ultrasound and angiographies showed that the blood flow was circulated in the grafts without aneurysmal dilations or significant stenoses at any time point, and ran stronger and close to the autologous blood vessel from one month after implantation. The SFTSs presented an initial tridimensionality without being distorted or squashed. SEM and immunohistochemistry results showed that a clear and discontinuous endodermis appeared after one month of implantation; when implanted for three months, an endothelial layer fully covered the inner surface of SFTSs. RT-PCR results indicated that the gene expression level of CD31 in SFTSs was 45.8% and 75.3% by that of autologous blood vessels at 3 months and 12 months, respectively. The VEGF gene showed a high expression level that continued to increase after implantation. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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Review

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12 pages, 2094 KiB

Open AccessReview

Enzymatic Protein Biopolymers as a Tool to Synthetize Eukaryotic Messenger Ribonucleic Acid (mRNA) with Uses in Vaccination, Immunotherapy and Nanotechnology

by Fabiola Urbina, Sebastián Morales-Pison and Edio Maldonado

Polymers 2020, 12(8), 1633; https://doi.org/10.3390/polym12081633 - 23 Jul 2020

Cited by 8 | Viewed by 3351

Abstract

Multi-subunit enzymes are protein biopolymers that are involved in many cellular processes. The enzyme that carries out the process of transcription of mRNAs is RNA polymerase II (RNAPII), which is a multi-subunit enzyme in eukaryotes. This protein biopolymer starts the transcription from specific [...] Read more.

Multi-subunit enzymes are protein biopolymers that are involved in many cellular processes. The enzyme that carries out the process of transcription of mRNAs is RNA polymerase II (RNAPII), which is a multi-subunit enzyme in eukaryotes. This protein biopolymer starts the transcription from specific sites and is positioned by transcription factors, which form a preinitiation complex (PIC) on gene promoters. To recognize and position the RNAPII and the transcription factors on the gene promoters are needed specific DNA sequences in the gene promoters, which are named promoter elements. Those gene promoter elements can vary and therefore several kinds of promoters exist, however, it appears that all promoters can use a similar pathway for PIC formation. Those pathways are discussed in this review. The in vitro transcribed mRNA can be used as vaccines to fight infectious diseases, e.g., in immunotherapy against cancer and in nanotechnology to deliver mRNA for a missing protein into the cell. We have outlined a procedure to produce an mRNA vaccine against the SARS-CoV-2 virus, which is the causing agent of the big pandemic, COVID-19, affecting human beings all over the world. The potential advantages of using eukaryotic RNAPII to synthetize large transcripts are outlined and discussed. In addition, we suggest a method to cap the mRNA at the 5′ terminus by using enzymes, which might be more effective than cap analogs. Finally, we suggest the construction of a future multi-talented RNAPII, which would be able to synthetize large mRNA and cap them in the test tube. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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28 pages, 3825 KiB

Open AccessReview

Protein–Polysaccharide Composite Materials: Fabrication and Applications

by Elizabeth J. Bealer, Shola Onissema-Karimu, Ashley Rivera-Galletti, Maura Francis, Jason Wilkowski, David Salas-de la Cruz and Xiao Hu

Polymers 2020, 12(2), 464; https://doi.org/10.3390/polym12020464 - 17 Feb 2020

Cited by 116 | Viewed by 14147

Abstract

Protein–polysaccharide composites have been known to show a wide range of applications in biomedical and green chemical fields. These composites have been fabricated into a variety of forms, such as films, fibers, particles, and gels, dependent upon their specific applications. Post treatments of [...] Read more.

Protein–polysaccharide composites have been known to show a wide range of applications in biomedical and green chemical fields. These composites have been fabricated into a variety of forms, such as films, fibers, particles, and gels, dependent upon their specific applications. Post treatments of these composites, such as enhancing chemical and physical changes, have been shown to favorably alter their structure and properties, allowing for specificity of medical treatments. Protein–polysaccharide composite materials introduce many opportunities to improve biological functions and contemporary technological functions. Current applications involving the replication of artificial tissues in tissue regeneration, wound therapy, effective drug delivery systems, and food colloids have benefited from protein–polysaccharide composite materials. Although there is limited research on the development of protein–polysaccharide composites, studies have proven their effectiveness and advantages amongst multiple fields. This review aims to provide insight on the elements of protein–polysaccharide complexes, how they are formed, and how they can be applied in modern material science and engineering. Full article

(This article belongs to the Special Issue Protein Biopolymer II)

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