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

Deadline for manuscript submissions: closed (10 November 2023) | Viewed by 25698

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Dr. In Chul Um

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Department of Biofibers and Biomaterials Science, Kyungpook National University, Daegu, Republic of Korea
Interests: silk; biopolymer; natural fiber; non-woven fabric; wet-spinning; electro-spinning
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Special Issue Information

Dear Colleagues,

Recently, protein-based biopolymers such as silk fibroin, silk sericin, wool keratin, collagen, gelatin, soy protein, etc. have attracted researchers’ attention because they have unique properties, including good biocompatibility, excellent cytocompatibility, and biodegradability. Owing to these useful properties, studies on the protein-based polymers have been extensively performed to apply them to various products, including cosmetics, biomedical products, and ecofriendly products.

In this Special Issue, researchers from both academia and industry are invited to submit their latest studies on protein-based biopolymers. The objective of this Special Issue is to provide a platform for knowledge and experience exchange on the preparation, structure, properties, and applications of protein-based biopolymers.

Dr. In Chul Um
Guest Editor

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Keywords

extraction and preparation of protein-based biopolymers
structural characterization and evaluation of properties of protein-based materials
application of protein-based polymers
protein-based materials from agricultural products
fabrication of protein-based polymers in various forms, including fiber, film, sponge, powder, gel, nonwoven, and textile
silk fibroin, silk sericin, spider silk, collagen, gelation, keratin, soy protein

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Published Papers (10 papers)

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Research

13 pages, 2787 KiB

Open AccessArticle

Structural Characteristics and Properties of Redissolved Silk Sericin

by Hye Gyeoung Lee, Mi Jin Jang, Byung-Dae Park and In Chul Um

Polymers 2023, 15(16), 3405; https://doi.org/10.3390/polym15163405 - 14 Aug 2023

Cited by 5 | Viewed by 1808

Abstract

Silk sericin has garnered the attention of researchers as a promising biomaterial because of its good biocompatibility and high water retention. However, despite its useful properties, the poor storage stability of sericin has restricted its extensive use in biorelated applications. This study extracted sericin from silkworm cocoon, dried and stored it as a solid, and then dissolved it in hot water conditions to improve the storage stability of sericin for its use. The dissolution behavior of the extracted sericin solids was examined in conjunction with the structural characteristics and properties of dissolved sericin. Consequently, the results of solution viscosity, gel strength, crystallinity index, and thermal decomposition temperature indicated that the molecular weight (MW) of the dissolved sericin remained constant until a dissolution time of 5 min, following which deterioration was observed. The optimum condition of dissolution of the extracted sericin solid was 5 min at 90 °C. Conclusively, the extracted sericin could be stored in a dry state and dissolved to prepare redissolved sericin aqueous solution with the same MW as extracted sericin, thereby improving the storage stability of the sericin aqueous solution. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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17 pages, 6221 KiB

Open AccessArticle

Polycaprolactone Electrospun Nanofiber Membrane with Skin Graft Containing Collagen and Bandage Containing MgO Nanoparticles for Wound Healing Applications

by Sadegh Nikfarjam, Yaqeen Aldubaisi, Vivek Swami, Vinay Swami, Gang Xu, Melville B. Vaughan, Roman F. Wolf and Morshed Khandaker

Polymers 2023, 15(9), 2014; https://doi.org/10.3390/polym15092014 - 24 Apr 2023

Cited by 7 | Viewed by 2414

Abstract

The objective of this study was to create a nanofiber-based skin graft with an antimicrobial bandage that could accelerate the healing of an open wound while minimizing infection. To this end, we prepared a bi-layer construct where the top layer acts as bandage, and the bottom layer acts as a dermal equivalent graft. A collagen (CG) gel was combined without and with an electrospun polycaprolactone (PCL) membrane to prepare CG and CG-PCL dermal equivalent constructs. The antibacterial properties of PCL with and without an antibacterial agent (MgO nanoparticles) against Staphylococcus aureus (ATCC 6538) was also examined. Human dermal fibroblasts were cultured in each construct to make the dermal equivalent grafts. After culturing, keratinocytes were plated on top of the tissues to allow growth of an epidermis. Rheological and durability tests were conducted on in vitro dermal and skin equivalent cultures, and we found that PCL significantly affects CG-PCL graft biological and mechanical strength (rheology and durability). PCL presence in the dermal equivalent allowed sufficient tension generation to activate fibroblasts and myofibroblasts in the presence of transforming growth factor-beta. During culture of the skin equivalents, optical coherence tomography (OCT) showed layers corresponding to dermal and epidermal compartments in the presence or absence of PCL; this was confirmed after fixed specimens were histologically sectioned and stained. MgO added to PCL showed antibacterial activity against S. aureus. In vivo animal studies using a rat skin model showed that a polycaprolactone nanofiber bandage containing a type I collagen skin graft has potential for wound healing applications. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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13 pages, 2008 KiB

Open AccessArticle

Nucleus-Targeting Nanoplatform Based on Dendritic Peptide for Precise Photothermal Therapy

by Wen-Song Wang, Xiao-Yu Ma, Si-Yao Zheng, Si Chen, Jin-Xuan Fan, Fan Liu and Guo-Ping Yan

Polymers 2023, 15(7), 1753; https://doi.org/10.3390/polym15071753 - 31 Mar 2023

Cited by 2 | Viewed by 1739

Abstract

Photothermal therapy directly acting on the nucleus is a potential anti-tumor treatment with higher killing efficiency. However, in practical applications, it is often difficult to achieve precise nuclear photothermal therapy because agents are difficult to accurately anchor to the nucleus. Therefore, it is urgent to develop a nanoheater that can accurately locate the nucleus. Here, we designed an amphiphilic arginine-rich dendritic peptide (RDP) with the sequence CRRK(RRCG(Fmoc))₂, and prepared a nucleus-targeting nanoplatform RDP/I by encapsulating the photothermal agent IR780 in RDP for precise photothermal therapy of the tumor nucleus. The hydrophobic group Fmoc of the dendritic peptide provides strong hydrophobic force to firmly encapsulate IR780, which improves the solubility and stability of IR780. Moreover, the arginine-rich structure facilitates cellular uptake of RDP/I and endows it with the ability to quickly anchor to the nucleus. The nucleus-targeting nanoplatform RDP/I showed efficient nuclear enrichment ability and a significant tumor inhibition effect. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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14 pages, 3591 KiB

Open AccessArticle

Electrospun Silk Fibroin-CNT Composite Fibers: Characterization and Application in Mediating Fibroblast Stimulation

by Rathnayake A. C. Rathnayake, Shinhae Yoon, Shuyao Zheng, Elwin D. Clutter and Rong R. Wang

Polymers 2023, 15(1), 91; https://doi.org/10.3390/polym15010091 - 26 Dec 2022

Cited by 3 | Viewed by 3111

Abstract

Electrospinning is a simple, low-cost, and highly efficient technique to generate desirable nano/microfibers from polymer solutions. Silk fibroin (SF), a biopolymer found in Bombyx mori cocoons, has attracted attention for various biomedical applications. In this study, functionalized CNT was incorporated in SF to generate biocomposite fibers by electrospinning. The electrospun (E-spun) fibers were well aligned with morphology mimicking the locally oriented ECM proteins in connective tissues. While as-spun fibers dissolved in water in just two minutes, ethanol vapor post-treatment promoted β-sheet formation leading to improved fiber stability in an aqueous environment (>14 days). The addition of a minute amount of CNT effectively improved the E-spun fiber alignment and mechanical strength while retained high biocompatibility and biodegradability. The fibers’ electrical conductivity increased by 13.7 folds and 21.8 folds, respectively, in the presence of 0.1 w% and 0.2 w% CNT in SF fibers. With aligned SF-CNT 0.1 % fibers as a cell culture matrix, we found electrical stimulation effectively activated fibroblasts from patients of pelvic organ prolapse (POP), a connective tissue disorder. The stimulation boosted the fibroblasts’ productivity of collagen III (COLIII) and collagen I (COLI) by 74 folds and 58 folds, respectively, and reduced the COLI to COLIII ratio favorable for tissue repair. The developed material and method offer a simple, direct, and effective way to remedy the dysfunctional fibroblasts of patients for personalized cell therapeutic treatment of diseases and health conditions associated with collagen disorder. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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17 pages, 5170 KiB

Open AccessArticle

Effect of Extraction Ingredients on the Conformation and Stability of Silk Sericin (SS)

by Munguti Peter Muindi, Ji Hae Lee, HaeYong Kweon and Muo Kasina

Polymers 2022, 14(19), 4118; https://doi.org/10.3390/polym14194118 - 1 Oct 2022

Cited by 1 | Viewed by 1665

Abstract

Silk sericin (SS) has different physicochemical properties depending on the extraction technique. In this study, SS was isolated in the presence of ingredients, including 5 to 10% ethanol (EtOH) and 5 to 10% glycine. Furthermore, temperature conditions of 80 °C, 100 °C, and 120 °C were used for 1, 3, and 5 h to evaluate the extraction rates. The extraction, gelation, structural, and cytotoxicity properties of SS extracted under different conditions were investigated. Extraction at 100 °C and 120 °C were found to have the highest SS yield, with 80 °C being the lowest. SS isolated at 100 °C and 120 °C for 1 and 3 h in water, and EtOH gelled at 4 °C in 2 to 3 days and 37 °C in 40 min. Glycine SS extracts were obtained at 100 °C and 120 °C for 1 h, gelled at 4 °C for 20 days and 37 °C for 16 h. SS was observed at 80 °C, with no gelation occurring. Glycine SS extracts obtained for 3, and 5 h at 120 °C showed no gelation. Circular dichroism (CD) results show glycine in SS induces α-helix and random coil structure. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and fast performance liquid chromatography (FPLC) were used to quantify the molecular weight distribution at 63 and 70 kDa, respectively. The MMT assay (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) revealed no cytotoxicity in macrophage RAW 264.7 cells treated with this method SS; these findings present the significance and possibility of using selected extraction ingredients in SS that allow for the application of native SS at an initial extraction viscosity. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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18 pages, 5955 KiB

Open AccessArticle

Effects of Radiation on Cross-Linking Reaction, Microstructure, and Microbiological Properties of Whey Protein-Based Tissue Adhesive Development

by Ning Liu, Guorong Wang and Mingruo Guo

Polymers 2022, 14(18), 3805; https://doi.org/10.3390/polym14183805 - 12 Sep 2022

Cited by 1 | Viewed by 2122

Abstract

Whey proteins are mainly a group of small globular proteins. Their structures can be modified by physical, chemical, and other means to improve their functionality. The objectives of this study are to investigate the effect of radiation on protein–protein interaction, microstructure, and microbiological properties of whey protein–water solutions for a novel biomaterial tissue adhesive. Whey protein isolate solutions (10%, 27%, 30%, 33%, and 36% protein) were treated by different intensities (10–35 kGy) of gamma radiation. The protein solutions were analyzed for viscosity, turbidity, soluble nitrogen, total plate count, and yeast and mold counts. The interactions between whey proteins were also analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and scanning electron microscopy. The viscosity of protein solution (27%, w/w) was increased by the treatment of gamma radiation and by the storage at 23 °C. The 35 kGy intensity irradiated soluble nitrogen (10%, w/w) was reduced to about half of the sample treated by 0 kGy gamma radiation. The effects of gamma radiation and storage time can significantly increase the viscosity of whey protein solutions (p < 0.05). Radiation treatment had significant impact on soluble nitrogen of whey protein solutions (p < 0.05). SDS-PAGE results show that the extent of oligomerization of whey protein isolate solutions are increased by the enhancement in gamma radiation intensity. Photographs of SEM also indicate that protein–protein interactions are induced by gamma radiation in the model system. Consistent with above results, the bonding strength increases by the addition of extent of gamma radiation and the concentration of glutaraldehyde. Our results revealed that the combination of gamma-irradiated whey protein isolate solutions and glutaraldehyde can be used as a novel biomaterial tissue adhesive. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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12 pages, 2397 KiB

Open AccessArticle

Silk Fibroin Conjugated with Heparin Promotes Epithelialization and Wound Healing

by Rikako Hama, Derya Aytemiz, Kelvin O. Moseti, Tsunenori Kameda and Yasumoto Nakazawa

Polymers 2022, 14(17), 3582; https://doi.org/10.3390/polym14173582 - 30 Aug 2022

Cited by 5 | Viewed by 2457

Abstract

Silk fibroin (SF) has attracted attention as a base biomaterial that could be suitable in many applications because of its shape and structure. Highly functional SF has been developed to promote tissue regeneration with heparin conjugation. However, the hydrophobic three-dimensional structure of SF makes it difficult to bind to high-molecular-weight and hydrophilic compounds such as heparin. In this study, sufficient heparin modification was achieved using tyrosine residues as reaction points to improve cellular response. As it was considered that there was a trade-off between the improvement of water wettability and cell responsiveness induced by heparin modification, influences on the structure, and mechanical properties, the structure and physical properties of the SF conjugated with heparin were extensively evaluated. Results showed that increased amounts of heparin modification raised heparin content and water wettability on film surfaces even though SF formation was not inhibited. In addition, the proliferation of endothelial cells and fibroblasts were enhanced when a surface with sufficient heparin assumed its potential in assisting wound healing. This research emphasizes the importance of material design focusing on the crystal structure inherent in SF in the development of functionalized SF materials. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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14 pages, 2482 KiB

Open AccessArticle

Porous Bilayer Vascular Grafts Fabricated from Electrospinning of the Recombinant Human Collagen (RHC) Peptide-Based Blend

by Thi My Do, Yang Yang and Aipeng Deng

Polymers 2021, 13(22), 4042; https://doi.org/10.3390/polym13224042 - 22 Nov 2021

Cited by 13 | Viewed by 2929

Abstract

Cardiovascular diseases, including coronary artery and peripheral vascular pathologies, are leading causes of mortality. As an alternative to autografts, prosthetic grafts have been developed to reduce the death rate. This study presents the development and characterization of bilayer vascular grafts with appropriate structural and biocompatibility properties. A polymer blend of recombinant human collagen (RHC) peptides and polycaprolactone (PCL) was used to build the inner layer of the graft by electrospinning and co-electrospinning the water-soluble polyethylene oxide (PEO) as sacrificial material together with PCL to generate the porous outer layer. The mechanical test demonstrated the bilayer scaffold’s appropriate mechanical properties as compared with the native vascular structure. Human umbilical vein endothelial cells (HUVEC) showed enhanced adhesion to the lumen after seeding on nanoscale fibers. Meanwhile, by enhancing the porosity of the microfibrous outer layer through the removal of PEO fibers, rat smooth muscle cells (A7r5) could proliferate and infiltrate the porous layer easily. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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20 pages, 6337 KiB

Open AccessArticle

Antitumor Activity of Rosmarinic Acid-Loaded Silk Fibroin Nanoparticles on HeLa and MCF-7 Cells

by Marta G. Fuster, Guzmán Carissimi, Mercedes G. Montalbán and Gloria Víllora

Polymers 2021, 13(18), 3169; https://doi.org/10.3390/polym13183169 - 18 Sep 2021

Cited by 33 | Viewed by 3003

Abstract

Rosmarinic acid (RA), one of the most important polyphenol-based antioxidants, has drawn increasing attention because of its remarkable bioactive properties, including anti-inflammatory, anticancer and antibacterial activities. The aim of this study was to synthesize and characterize RA-loaded silk fibroin nanoparticles (RA-SFNs) in terms of their physical–chemical features and composition, and to investigate their antitumor activity against human cervical carcinoma and breast cancer cell lines (HeLa and MCF-7). Compared with the free form, RA bioavailability was enhanced when the drug was adsorbed onto the surface of the silk fibroin nanoparticles (SFNs). The resulting particle diameter was 255 nm, with a polydispersity index of 0.187, and the Z-potential was −17 mV. The drug loading content of the RA-SFNs was 9.4 wt.%. Evaluation of the in vitro drug release of RA from RA-SFNs pointed to a rapid release in physiological conditions (50% of the total drug content was released in 0.5 h). Unloaded SFNs exhibited good biocompatibility, with no significant cytotoxicity observed during the first 48 h against HeLa and MCF-7 cancer cells. In contrast, cell death increased in a concentration-dependent manner after treatment with RA-SFNs, reaching an IC₅₀ value of 1.568 and 1.377 mg/mL on HeLa and MCF-7, respectively. For both cell lines, the IC₅₀ of free RA was higher. The cellular uptake of the nanoparticles studied was increased when RA was loaded on them. The cell cycle and apoptosis studies revealed that RA-SFNs inhibit cell proliferation and induce apoptosis on HeLa and MCF-7 cell lines. It is concluded, therefore, that the RA delivery platform based on SFNs improves the antitumor potential of RA in the case of the above cancers. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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12 pages, 15129 KiB

Open AccessArticle

Effect of Relative Humidity on the Electrospinning Performance of Regenerated Silk Solution

by Bo Kyung Park and In Chul Um

Polymers 2021, 13(15), 2479; https://doi.org/10.3390/polym13152479 - 28 Jul 2021

Cited by 14 | Viewed by 2996

Abstract

Recently, the electrospun silk web has been intensively studied in terms of its biomedical applications, including tissue engineering scaffolds, due to its good biocompatibility, cytocompatibility, and biodegradability. In this study, the effect of relative humidity (RH) conditions on the morphology of electrospun silk fiber and the electrospinning production rate of silk solution was examined. In addition, the effect of RH on the molecular conformation of electrospun silk web was examined using Fourier transform infrared (FTIR) spectroscopy. As RH was increased, the maximum electrospinning rate of silk solution and fiber diameter of the resultant electrospun silk web were decreased. When RH was increased to 60%, some beads were observed, which showed that the electrospinnability of silk formic acid solution deteriorated with an increase in RH. The FTIR results showed that electrospun silk web was partially β-sheet crystallized and RH did not affect the molecular conformation of silk. Full article

(This article belongs to the Special Issue Protein-Based Biopolymers)

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