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Polymers
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Protein Biopolymer
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Protein Biopolymer

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Biomacromolecules, Biobased and Biodegradable Polymers".

Deadline for manuscript submissions: closed (31 August 2018) | Viewed by 97676

Special Issue Editor

Prof. Dr. Xiao Hu

E-Mail Website1 Website2
Guest Editor
Department of Physics and Astronomy, College of Science and Mathematics, Rowan University, Glassboro, NJ 08028, USA
Interests: polymer; biomaterials; biomacromolecules; regenerative medicine; drug delivery; nanotechnology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to protein biopolymers. Typical protein polymers include animal proteins (e.g., silk, keratin, collagen, elastin, resilin, reflectin), plant proteins (e.g., corn zein, soy, wheat gluten), as well as their related protein peptides derived from recombinant biotechnology. Compared to synthetic plastics, protein polymers have advantages of being biocompatible, biodegradable and sustainable with tunable mechanical strength and water solubility. These proteins can be fabricated into functional materials such as films, gels, particles, fibers, or composites, and are widely used for different applications, including tissue regeneration, drug delivery, antibody and vaccine storage, disease model, flexible biosensor, green plastics, biophotonics, and nano-biotechnology.

The aim of this Special Issue is to discuss their design, synthesis, characterization, manufacturing or modeling, as well as their various physical and chemical applications in biomedical and green industry fields. Both research and review articles are welcome.

Dr. Xiao Hu
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Protein biopolymer
  • Protein film, fiber, foam, gel, particle, sensor, device, and composite
  • Biomacromolecules and functional materials
  • Polymer design and characterization
  • Protein physical and chemical properties

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Published Papers (17 papers)

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Research

12 pages, 3696 KiB  
Article
Comparative Investigation of Thermal and Structural Behavior in Renewably Sourced Composite Films of Even-Even Nylons (610 and 1010) with Silk Fibroin
by Kayla A. Callaway, Ye Xue, Vincent Altimari, Guoxiang Jiang and Xiao Hu
Polymers 2018, 10(9), 1029; https://doi.org/10.3390/polym10091029 - 15 Sep 2018
Cited by 5 | Viewed by 4815
Abstract
As the average life expectancy continues to increase, so does the need for resorbable materials designed to treat, augment, or replace components and functions of the body. Naturally occurring biopolymers such as silks are already attractive candidates due to natural abundance and high [...] Read more.
As the average life expectancy continues to increase, so does the need for resorbable materials designed to treat, augment, or replace components and functions of the body. Naturally occurring biopolymers such as silks are already attractive candidates due to natural abundance and high biocompatibility accompanied by physical properties which are easily modulated through blending with another polymer. In this paper, the authors report on the fabrication of biocomposite materials made from binary blends of Bombyx mori silk fibroin (SF) protein and renewably sourced low molecular weight nylon 610 and high molecular weight nylon 1010. Films were characterized using scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results of this study demonstrated that enhanced structural and thermal properties were achievable in composite films SF-N610/N1010 due to their chemical similarity and the possible formation of hydrogen bonds between nylon and silk molecular chains. This study provides useful insight into the sustainable design of functional composite materials for biomedical and green technologies. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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11 pages, 7667 KiB  
Article
Extraction of Keratin from Rabbit Hair by a Deep Eutectic Solvent and Its Characterization
by Dongyue Wang, Xu-Hong Yang, Ren-Cheng Tang and Fan Yao
Polymers 2018, 10(9), 993; https://doi.org/10.3390/polym10090993 - 06 Sep 2018
Cited by 44 | Viewed by 8055
Abstract
Keratin from a variety of sources is one of the most abundant biopolymers. In livestock and textile industries, a large amount of rabbit hair waste is produced every year, and therefore it is of great significance to extract keratin from waste rabbit hair [...] Read more.
Keratin from a variety of sources is one of the most abundant biopolymers. In livestock and textile industries, a large amount of rabbit hair waste is produced every year, and therefore it is of great significance to extract keratin from waste rabbit hair in terms of the treatment and utilization of wastes. In this study, a novel, eco-friendly and benign choline chloride/oxalic acid deep eutectic solvent at a molar ratio of 1:2 was applied to dissolve waste rabbit hair, and after dissolution keratin was separated by dialysis, filtration, and freeze-drying. The dissolution temperature effect was discussed, and the resulting keratin powder was characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, protein electrophoresis, thermogravimetry and differential scanning calorimetry, and amino acid analysis. During the dissolution process, the α-helix structure of rabbit hair was deconstructed, and the disulfide bond linkages were broken. The solubility of rabbit hair was significantly enhanced by increasing dissolution temperature, and reached 88% at 120 °C. The keratin produced by dissolving at 120 °C displayed flaky powders after freeze-drying, and had a molecular weight ranging from 3.8 to 5.8 kDa with a high proportion of serine, glutamic acid, cysteine, leucine, and arginine. Such features of molecular weight and amino acid distribution provide more choices for the diverse applications of keratin materials. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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14 pages, 4285 KiB  
Article
The Effect of Thermo-Chemical Treatment on the Water Resistance of Defatted Soybean Flour-Based Wood Adhesive
by Binghan Zhang, Jin Li, Yufei Kan, Jianfang Gao, Yuehong Zhang and Zhenhua Gao
Polymers 2018, 10(9), 955; https://doi.org/10.3390/polym10090955 - 28 Aug 2018
Cited by 20 | Viewed by 5831
Abstract
The aim of this study was to effectively improve the water resistance of a defatted soybean flour (DSF)-based adhesive by subjecting DSF to thermo-chemical treatment in the presence of sodium dodecyl sulfate (SDS), and then the crosslinking with epichlorohydrin-modified polyamide (EMPA). The effect [...] Read more.
The aim of this study was to effectively improve the water resistance of a defatted soybean flour (DSF)-based adhesive by subjecting DSF to thermo-chemical treatment in the presence of sodium dodecyl sulfate (SDS), and then the crosslinking with epichlorohydrin-modified polyamide (EMPA). The effect of thermo-chemical treatment on the structures and properties of the DSF and DSF-based adhesive were investigated by plywood evaluation, boiling-water-insoluble content, and acetaldehyde value measurements, as well as FTIR, X-ray photoelectron spectroscopic (XPS), X-ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), and rheology analyses. The test results revealed that the water resistance of the DSF-based adhesive was significantly improved, attributed to the formation of a solid three-dimensional crosslinked network structure resulted from the repolymerization of DSF, the Maillard reaction between the protein and carbohydrate, and chemical crosslinking between the crosslinker and DSF. Moreover, SDS destroyed the hydrophobic interactions within protein and inhibited macromolecular aggregations during the thermal treatment. Therefore, more reactive groups buried within the globular structure of the soybean protein component of DSF could be released, which supported the repolymerization, Maillard reaction, and chemical crosslinking of DSF, thereby leading to an improved crosslinking density of the cured DSF-based adhesive. In addition, the adhesive composed of thermo-chemically treated DSF and EMPA exhibited preferable viscosity and viscosity stability suitable for the production of wood composites. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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14 pages, 2545 KiB  
Article
Responsive Protein Hydrogels Assembled from Spider Silk Carboxyl-Terminal Domain and Resilin Copolymers
by Fang Luo, Zhi-Gang Qian and Xiao-Xia Xia
Polymers 2018, 10(8), 915; https://doi.org/10.3390/polym10080915 - 14 Aug 2018
Cited by 13 | Viewed by 4727
Abstract
Responsive protein hydrogels are known to respond to target external stimuli that cause changes in their properties, attracting considerable attention for diverse applications. Here we report the design and recombinant biosynthesis of protein copolymers via genetic fusion of repeating units of resilin with [...] Read more.
Responsive protein hydrogels are known to respond to target external stimuli that cause changes in their properties, attracting considerable attention for diverse applications. Here we report the design and recombinant biosynthesis of protein copolymers via genetic fusion of repeating units of resilin with spider silk carboxyl-terminal (CT) domain. The resulting copolymers were thermoresponsive in aqueous solutions, and formed reversible hydrogels at low temperatures and irreversible hydrogels at high temperatures within minutes, a peculiar dual thermogelation feature endowed by the CT domain. The incorporation of resilin blocks upshifted the temperature range of reversible gelation and hydrogel stiffness, whereas the temperature of irreversible gelation was differentially affected by the length of the resilin blocks. In addition, sodium chloride and potassium phosphate at moderate concentrations downregulated both the reversible and irreversible gelation temperatures and hydrogel mechanical properties, proving the salts as another level of control over dual thermogelation. Surprisingly, the copolymers were prone to gelate at body temperature in a time-dependent manner, and the resulting hydrogels were pH-responsive to release a highly polar model drug in vitro. The newly developed resilin-CT copolymers and the multistimuli-responsive hydrogels may be potentially useful in biomedicine, such as for drug delivery. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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12 pages, 4516 KiB  
Article
Compatibility Evaluation of Non-Woven Sheet Composite of Silk Fibroin and Polyurethane in the Wet State
by Derya Aytemiz, Yasuhiro Fukuda, Akira Higuchi, Atsushi Asano, Chikako T. Nakazawa, Tsunenori Kameda, Taiyo Yoshioka and Yasumoto Nakazawa
Polymers 2018, 10(8), 874; https://doi.org/10.3390/polym10080874 - 06 Aug 2018
Cited by 18 | Viewed by 4436
Abstract
SF/polyurethane composite non-woven sheet was fabricated to evaluate the cardiovascular tissue engineering materials in the wet state. The compatibility and microstructure analyses were carried out on the fabricated SF/polyurethane composite non-woven sheet by thermal analysis and solid-state NMR analysis in the wet state. [...] Read more.
SF/polyurethane composite non-woven sheet was fabricated to evaluate the cardiovascular tissue engineering materials in the wet state. The compatibility and microstructure analyses were carried out on the fabricated SF/polyurethane composite non-woven sheet by thermal analysis and solid-state NMR analysis in the wet state. To evaluate the modulus of elasticity, a tensile test was performed and supported with dynamic viscoelasticity and mechanical analysis. Results showed that SF/polyurethane composites form domains within the non-woven sheet and are in a finely dispersed state while maintaining their structures at a scale of several tens of nm. Moreover, an increase of the loss tangent with low elastic modulus proved that a micromolecular interaction occurs between silk fibroin (SF) and polyurethane molecules. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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14 pages, 4273 KiB  
Article
Confirmation of Bioinformatics Predictions of the Structural Domains in Honeybee Silk
by Andrea L. Woodhead, Andrew T. Church, Trevor D. Rapson, Holly E. Trueman, Jeffrey S. Church and Tara D. Sutherland
Polymers 2018, 10(7), 776; https://doi.org/10.3390/polym10070776 - 16 Jul 2018
Cited by 4 | Viewed by 3304
Abstract
Honeybee larvae produce a silk made up of proteins in predominantly a coiled coil molecular structure. These proteins can be produced in recombinant systems, making them desirable templates for the design of advanced materials. However, the atomic level structure of these proteins is [...] Read more.
Honeybee larvae produce a silk made up of proteins in predominantly a coiled coil molecular structure. These proteins can be produced in recombinant systems, making them desirable templates for the design of advanced materials. However, the atomic level structure of these proteins is proving difficult to determine: firstly, because coiled coils are difficult to crystalize; and secondly, fibrous proteins crystalize as fibres rather than as discrete protein units. In this study, we synthesised peptides from the central structural domain, as well as the N- and C-terminal domains, of the honeybee silk. We used circular dichroism spectroscopy, infrared spectroscopy, and molecular dynamics to investigate the folding behaviour of the central domain peptides. We found that they folded as predicted by bioinformatics analysis, giving the protein engineer confidence in bioinformatics predictions to guide the design of new functionality into these protein templates. These results, along with the infrared structural analysis of the N- and C-terminal domain peptides and the comparison of peptide film properties with those of the full-length AmelF3 protein, provided significant insight into the structural elements required for honeybee silk protein to form into stable materials. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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12 pages, 4082 KiB  
Article
Facile Preparation of Highly Stretchable and Recovery Peptide-Polyurethane/Ureas
by Lin Gu, Yuanzhang Jiang and Jinlian Hu
Polymers 2018, 10(6), 637; https://doi.org/10.3390/polym10060637 - 08 Jun 2018
Cited by 7 | Viewed by 3938
Abstract
In this work, a new class of highly stretchable peptide-polyurethane/ureas (PUUs) were synthesized containing short β-sheet forming peptide blocks of poly(γ-benzyl-l-glutamate)-b-poly(propylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PPG-b-PBLG), isophorone diisocyanate as [...] Read more.
In this work, a new class of highly stretchable peptide-polyurethane/ureas (PUUs) were synthesized containing short β-sheet forming peptide blocks of poly(γ-benzyl-l-glutamate)-b-poly(propylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PPG-b-PBLG), isophorone diisocyanate as the hard segment, and polytetramethylene ether glycol as the soft phase. PBLG-b-PPG-b-PBLG with short peptide segment length (<10 residues) was synthesized by amine-initiated ring opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydrides (BLG-NCA), which shows mixed α-helix and β-sheet conformation, where the percent of β-sheet structure was above 48%. Morphological studies indicate that the obtained PUUs show β-sheet crystal and nanofibrous structure. Mechanical tests reveal the PUUs display medium tensile strength (0.25–4.6 MPa), high stretchability (>1600%), human-tissue-compatible Young’s modulus (226–513 KPa). Furthermore, the shape recovery ratio could reach above 85% during successive cycles at high strain (500%). In this study, we report a facile synthetic method to obtain highly stretchable and recovery peptide-polyurethane/urea materials, which will have various potential applications such as wearable and implantable electronics, and biomedical devices. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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13 pages, 6957 KiB  
Article
Gluten Polymer Networks—A Microstructural Classification in Complex Systems
by Isabelle Lucas, Thomas Becker and Mario Jekle
Polymers 2018, 10(6), 617; https://doi.org/10.3390/polym10060617 - 05 Jun 2018
Cited by 28 | Viewed by 6223
Abstract
A classification of gluten polymer networks would support a better understanding of structure-function relationships of any gluten polymer material and thus, the control of processing properties. However, quantification and interpretation of the gluten network structures is challenging due to their complexity. Thus, the [...] Read more.
A classification of gluten polymer networks would support a better understanding of structure-function relationships of any gluten polymer material and thus, the control of processing properties. However, quantification and interpretation of the gluten network structures is challenging due to their complexity. Thus, the network formation was altered by specific gluten-modifying agents (glutathione, ascorbic acid, potassium bromate, glucose oxidase, transglutaminase, bromelain) in this study in order to clarify if structural alterations can be detected on a microstructural level and to specify different polymer arrangements in general. Microstructure analysis was performed by confocal laser scanning microscopy followed by quantification with protein network analysis. It was shown that alterations in gluten microstructure could be elucidated according to the kind of modification in cross-linking (disulphide, (iso) peptide, dityrosyl). Linear correlations of structural network attributes among each other were found, leading to an assertion in general: the higher the branching rate, the thinner the protein threads and the larger the interconnected protein aggregate. Considering the morphological attribute lacunarity, a quantitative classification of different gluten arrangements was established. These assertions were extended by using unspecific gluten-modifying agents in addition to the specific ones. Ultimately, five network types were proposed based on diverse polymer arrangements. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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9 pages, 1676 KiB  
Article
Preparation, Structure, and Properties of Silk Fabric Grafted with 2-Hydroxypropyl Methacrylate Using the HRP Biocatalyzed ATRP Method
by Jinqiu Yang, Shenzhou Lu, Tieling Xing and Guoqiang Chen
Polymers 2018, 10(5), 557; https://doi.org/10.3390/polym10050557 - 21 May 2018
Cited by 9 | Viewed by 4211
Abstract
Atom transfer radical polymerization (ATRP) is a “living”/controlled radical polymerization, which is also used for surface grafting of various materials including textiles. However, the commonly used metal complex catalyst, CuBr, is mildly toxic and results in unwanted color for textiles. In order to [...] Read more.
Atom transfer radical polymerization (ATRP) is a “living”/controlled radical polymerization, which is also used for surface grafting of various materials including textiles. However, the commonly used metal complex catalyst, CuBr, is mildly toxic and results in unwanted color for textiles. In order to replace the transition metal catalyst of surface-initiated ATRP, the possibility of HRP biocatalyst was investigated in this work. 2-hydroxypropyl methacrylate (HPMA) was grafted onto the surface of silk fabric using the horseradish peroxidase (HRP) biocatalyzed ATRP method, which is used to improve the crease resistance of silk fabric. The structure of grafted silk fabric was characterized by Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, thermogravimetic analysis, and scanning electron microscopy. The results showed that HPMA was successfully grafted onto silk fabric. Compared with the control silk sample, the wrinkle recovery property of grafted silk fabric was greatly improved, especially the wet crease recovery property. However, the whiteness, breaking strength, and moisture regain of grafted silk fabric decreased somewhat. The present work provides a novel, biocatalyzed, environmentally friendly ATRP method to obtain functional silk fabric, which is favorable for clothing application and has potential for medical materials. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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12 pages, 5153 KiB  
Article
Silk Composite with a Fluoropolymer as a Water-Resistant Protein-Based Material
by Keiji Numata, Nao Ifuku and Akira Isogai
Polymers 2018, 10(4), 459; https://doi.org/10.3390/polym10040459 - 21 Apr 2018
Cited by 9 | Viewed by 5725
Abstract
Silk-based materials are water-sensitive and show different physical properties at different humidities and under wet/dry conditions. To overcome the water sensitivity of silk-based materials, we developed a silk composite material with a fluoropolymer. Blending and coating the silk protein-based materials, such as films [...] Read more.
Silk-based materials are water-sensitive and show different physical properties at different humidities and under wet/dry conditions. To overcome the water sensitivity of silk-based materials, we developed a silk composite material with a fluoropolymer. Blending and coating the silk protein-based materials, such as films and textiles, with the fluoropolymer enhanced the surface hydrophobicity, water vapor barrier properties, and size stability during shrinkage tests. This material design with a protein biopolymer and a fluoropolymer is expected to broaden the applicability of protein-based materials. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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13 pages, 47371 KiB  
Article
Fabrication and In Vitro Characterization of Electrochemically Compacted Collagen/Sulfated Xylorhamnoglycuronan Matrix for Wound Healing Applications
by Lingzhi Kang, Xiao Liu, Zhilian Yue, Zhi Chen, Chris Baker, Pia C. Winberg and Gordon G. Wallace
Polymers 2018, 10(4), 415; https://doi.org/10.3390/polym10040415 - 09 Apr 2018
Cited by 23 | Viewed by 6442
Abstract
Skin autografts are in great demand due to injuries and disease, but there are challenges using live tissue sources, and synthetic tissue is still in its infancy. In this study, an electrocompaction method was applied to fabricate the densely packed and highly ordered [...] Read more.
Skin autografts are in great demand due to injuries and disease, but there are challenges using live tissue sources, and synthetic tissue is still in its infancy. In this study, an electrocompaction method was applied to fabricate the densely packed and highly ordered collagen/sulfated xylorhamnoglycuronan (SXRGlu) scaffold which closely mimicked the major structure and components in natural skin tissue. The fabricated electrocompacted collagen/SXRGlu matrices (ECLCU) were characterized in terms of micromorphology, mechanical property, water uptake ability and degradability. The viability, proliferation and morphology of human dermal fibroblasts (HDFs) cells on the fabricated matrices were also evaluated. The results indicated that the electrocompaction process could promote HDFs proliferation and SXRGlu could improve the water uptake ability and matrices’ stability against collagenase degradation, and support fibroblast spreading on the ECLCU matrices. Therefore, all these results suggest that the electrocompacted collagen/SXRGlu scaffold is a potential candidate as a dermal substitute with enhanced biostability and biocompatibility. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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11 pages, 3567 KiB  
Article
Silk Fibroin/Polyvinyl Pyrrolidone Interpenetrating Polymer Network Hydrogels
by Dajiang Kuang, Feng Wu, Zhuping Yin, Tian Zhu, Tieling Xing, Subhas C. Kundu and Shenzhou Lu
Polymers 2018, 10(2), 153; https://doi.org/10.3390/polym10020153 - 06 Feb 2018
Cited by 28 | Viewed by 6368
Abstract
Silk fibroin hydrogel is an ideal model as biomaterial matrix due to its excellent biocompatibility and used in the field of medical polymer materials. Nevertheless, native fibroin hydrogels show poor transparency and resilience. To settle these drawbacks, an interpenetrating network (IPN) of hydrogels [...] Read more.
Silk fibroin hydrogel is an ideal model as biomaterial matrix due to its excellent biocompatibility and used in the field of medical polymer materials. Nevertheless, native fibroin hydrogels show poor transparency and resilience. To settle these drawbacks, an interpenetrating network (IPN) of hydrogels are synthesized with changing ratios of silk fibroin/N-Vinyl-2-pyrrolidonemixtures that crosslink by H2O2 and horseradish peroxidase. Interpenetrating polymer network structure can shorten the gel time and the pure fibroin solution gel time for more than a week. This is mainly due to conformation from the random coil to the β-sheet structure changes of fibroin. Moreover, the light transmittance of IPN hydrogel can be as high as more than 97% and maintain a level of 90% within a week. The hydrogel, which mainly consists of random coil, the apertures inside can be up to 200 μm. Elastic modulus increases during the process of gelation. The gel has nearly 95% resilience under the compression of 70% eventually, which is much higher than native fibroin gel. The results suggest that the present IPN hydrogels have excellent mechanical properties and excellent transparency. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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21 pages, 2810 KiB  
Article
Proteins as Nano-Carriers for Bioactive Compounds. The Case of 7S and 11S Soy Globulins and Folic Acid Complexation
by María Emilia Ochnio, Jimena H. Martínez, Mariana C. Allievi, Marcos Palavecino, Karina D. Martínez and Oscar E. Pérez
Polymers 2018, 10(2), 149; https://doi.org/10.3390/polym10020149 - 05 Feb 2018
Cited by 33 | Viewed by 4330
Abstract
Isolated 7S and 11S globulins obtained from defeated soy flour were complexated with folic acid (FA) in order to generate nano-carriers for this important vitamin in human nutrition. Fluorescence spectroscopy and dynamic light scattering were applied to follow the nano-complexes formation and for [...] Read more.
Isolated 7S and 11S globulins obtained from defeated soy flour were complexated with folic acid (FA) in order to generate nano-carriers for this important vitamin in human nutrition. Fluorescence spectroscopy and dynamic light scattering were applied to follow the nano-complexes formation and for their characterization. Fluorescence experimental data were modeled by the Stern-Volmer and a modified double logarithm approach. The results obtained confirmed static quenching. The number of binding sites on the protein molecule was ~1. The values obtained for the binding constants suggest a high affinity between proteins and FA. Particle size distribution allowed to study the protein aggregation phenomenon induced by FA bound to the native proteins. Z-average manifested a clear trend to protein aggregation. 11S-FA nano-complexes resulted in more polydispersity. ζ-potential of FA nano-complexes did not show a remarkable change after FA complexation. The biological activity of nano-complexes loaded with FA was explored in terms of their capacity to enhance the biomass formation of Lactobacillus casei BL23. The results concerning to nano-complexes inclusion in culture media showed higher bacterial growth. Such a result was attributed to the entry of the acid by the specific receptors concomitantly by the peptide receptors. These findings have technological impact for the use of globulins-FA based nano-complexes in nutraceutical, pharmaceutical and food industries. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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15 pages, 43967 KiB  
Article
Vascular Cell Co-Culture on Silk Fibroin Matrix
by Fangfang Tu, Yunfei Liu, Helei Li, Pange Shi, Yunxia Hao, Yue Wu, Honggen Yi, Yin Yin and Jiannan Wang
Polymers 2018, 10(1), 39; https://doi.org/10.3390/polym10010039 - 01 Jan 2018
Cited by 15 | Viewed by 4900
Abstract
Silk fibroin (SF), a natural polymer material possessing excellent biocompatibility and biodegradability, and has been widely used in biomedical applications. In order to explore the behavior of vascular cells by co-culturing on regenerated SF matrix for use as artificial blood vessels, human aorta [...] Read more.
Silk fibroin (SF), a natural polymer material possessing excellent biocompatibility and biodegradability, and has been widely used in biomedical applications. In order to explore the behavior of vascular cells by co-culturing on regenerated SF matrix for use as artificial blood vessels, human aorta vascular smooth muscle cells (HAVSMCs) were co-cultured with human arterial fibroblasts (HAFs) or human umbilical vein endothelial cells (HUVECs) on SF films and SF tubular scaffolds (SFTSs). Analysis of cell morphology and deoxyribonucleic acid (DNA) content showed that HUVECs, HAVSMCs and HAFs adhered and spread well, and exhibited high proliferative activity whether cultured alone or in co-culture. Immunofluorescence and scanning electron microscopy (SEM) analysis showed that HUVECs and HAFs co-existed well with HAVSMCs on SF films or SFTSs. Cytokine expression determined by reverse transcription-polymerase chain reaction (RT-PCR) indicated that the expression levels of α-smooth muscle actin (α-SMA) and smooth muscle myosin heavy chain (SM-MHC) in HAVSMCs were inhibited on SF films or SFTSs, but expression could be obviously promoted by co-culture with HUVECs or HAFs, especially that of SM-MHC. On SF films, the expression of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (CD31) in HUVECs was promoted, and the expression levels of both increased obviously when co-cultured with HAVSMCs, with the expression levels of VEGF increasing with increasing incubation time. The expression levels of VEGF and CD31 in cells co-cultured on SFTSs improved significantly from day 3 compared with the mono-culture group. These results were beneficial to the mechanism analysis on vascular cell colonization and vascular tissue repair after in vivo transplantation of SFTSs. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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3483 KiB  
Article
Biosynthesis and Characterization of Recombinant Silk-Like Polypeptides Derived from the Heavy Chain of Silk Fibrion
by Yue Wu, Zhao Kang, Zhifang Tian, Mingyang Wu and Jiannan Wang
Polymers 2017, 9(12), 669; https://doi.org/10.3390/polym9120669 - 03 Dec 2017
Cited by 13 | Viewed by 5717
Abstract
In order to investigate the impacts on the structure and biomedical function of typical fragments derived from repetitive and non-repetitive regions of the Bombyx mori silk fibroin heavy chain, several block combination genes (gs16f1, gs16f4, gs16f8, and gs16f12) were designed, cloned [...] Read more.
In order to investigate the impacts on the structure and biomedical function of typical fragments derived from repetitive and non-repetitive regions of the Bombyx mori silk fibroin heavy chain, several block combination genes (gs16f1, gs16f4, gs16f8, and gs16f12) were designed, cloned into a fusion protein expression vector tagged with glutathione S-transferase (GST), and expressed in Escherichia coli. Fusion proteins GST-GS16F1, GST-GS16F4, and GST-GS16F8 were purified by GST affinity chromatography, and single bands were identified by SDS-PAGE. Under optimal initial cell density, in ducer concentration and induction expression time, the yield of purified GST-GS16F1, GST-GS16F4, and GST-GS16F8 per liter of bacterial culture reached 79, 53, and 28 mg, respectively. Mass spectrometry revealed molecular weights for GST-GS16F1, GST-GS16F4, and GST-GS16F8 of 37.7, 50.0, and 65.7 kDa, respectively, consistent with the theoretical values of 37.4, 49.4, and 65.5 kDa. Similarly, measured values of pI were 5.35, 4.5, and 4.2 for the fusion proteins, consistent with predicted values of 5.34, 4.44, and 4.09. CD spectra showed the molecular conformation of GS16F1 was mainly β-sheet structure, while more stable α-helix structure formed in GS16F4 and GS16F8. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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6923 KiB  
Article
Restoration of Impaired Metabolic Energy Balance (ATP Pool) and Tube Formation Potential of Endothelial Cells under “high glucose”, Diabetic Conditions by the Bioinorganic Polymer Polyphosphate
by Xiaohong Wang, Maximilian Ackermann, Meik Neufurth, Shunfeng Wang, Qiang Li, Qingling Feng, Heinz C. Schröder and Werner E. G. Müller
Polymers 2017, 9(11), 575; https://doi.org/10.3390/polym9110575 - 04 Nov 2017
Cited by 12 | Viewed by 6597
Abstract
Micro-vascularization is a fast, energy-dependent process that is compromised by elevated glucose concentrations such as in diabetes mellitus disease. Here, we studied the effect of the physiological bioinorganic polymer, polyphosphate (polyP), on the reduced ATP content and impaired function of endothelial cells cultivated [...] Read more.
Micro-vascularization is a fast, energy-dependent process that is compromised by elevated glucose concentrations such as in diabetes mellitus disease. Here, we studied the effect of the physiological bioinorganic polymer, polyphosphate (polyP), on the reduced ATP content and impaired function of endothelial cells cultivated under “high glucose” (35 mM diabetes mellitus conditions) concentrations. This high-energy biopolymer has been shown to provide a source of metabolic energy, stored in its phosphoanhydride bonds. We show that exposure of human umbilical vein endothelial cells (HUVEC cells) to “high glucose” levels results in reduced cell viability, increased apoptotic cell death, and a decline in intracellular ATP level. As a consequence, the ability of HUVEC cells to form tube-like structures in the in vitro cell tube formation assay was almost completely abolished under “high glucose” conditions. Those cells were grown onto a physiological collagen scaffold (collagen/basement membrane extract). We demonstrate that these adverse effects of increased glucose levels can be reversed by administration of polyP to almost normal values. Using Na-polyP, complexed in a stoichiometric (molar) ratio to Ca2+ ions and in the physiological concentration range between 30 and 300 µM, an almost complete restoration of the reduced ATP pool of cells exposed to “high glucose” was found, as well as a normalization of the number of apoptotic cells and energy-dependent tube formation. It is concluded that the adverse effects on endothelial cells caused by the metabolic energy imbalance at elevated glucose concentrations can be counterbalanced by polyP, potentially opening new strategies for treatment of the micro-vascular complications in diabetic patients. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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Article
Biocompatible Silk/Polymer Energy Harvesters Using Stretched Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) Nanofibers
by Raghid Najjar, Yi Luo, Dave Jao, David Brennan, Ye Xue, Vince Beachley, Xiao Hu and Wei Xue
Polymers 2017, 9(10), 479; https://doi.org/10.3390/polym9100479 - 30 Sep 2017
Cited by 23 | Viewed by 9774
Abstract
Energy harvested from human body movement can produce continuous, stable energy to portable electronics and implanted medical devices. The energy harvesters need to be light, small, inexpensive, and highly portable. Here we report a novel biocompatible device made of poly (vinylidene fluoride-co [...] Read more.
Energy harvested from human body movement can produce continuous, stable energy to portable electronics and implanted medical devices. The energy harvesters need to be light, small, inexpensive, and highly portable. Here we report a novel biocompatible device made of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers on flexible substrates. The nanofibers are prepared with electrospinning followed by a stretching process. This results in aligned nanofibers with diameter control. The assembled device demonstrates high mechanical-to-electrical conversion performance, with stretched PVDF-HFP nanofibers outperforming regular electrospun samples by more than 10 times. Fourier transform infrared spectroscopy (FTIR) reveals that the stretched nanofibers have a higher β phase content, which is the critical polymorph that enables piezoelectricity in polyvinylidene fluoride (PVDF). Polydimethylsiloxane (PDMS) is initially selected as the substrate material for its low cost, high flexibility, and rapid prototyping capability. Bombyx Mori silkworm silk fibroin (SF) and its composites are investigated as promising alternatives due to their high strength, toughness, and biocompatibility. A composite of silk with 20% glycerol demonstrates higher strength and larger ultimate strain than PDMS. With the integration of stretched electrospun PVDF-HFP nanofibers and flexible substrates, this pilot study shows a new pathway for the fabrication of biocompatible, skin-mountable energy devices. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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