Fabrication and characterization of electrospun PCL/Antheraea pernyisilk fibroin nanofibrous scaffolds

Silk fibroin-derived electrospun materials for biomedical applications: A review

Electrospinning is a versatile technique for fabricating polymeric fibers with diameters ranging from micro- to nanoscale, exhibiting multiple morphologies and arrangements. By combining silk fibroin (SF) with synthetic and/or natural polymers, electrospun materials with outstanding biological, chemical, electrical, physical, mechanical, and optical properties can be achieved, fulfilling the evolving biomedical demands. This review highlights the remarkable versatility of SF-derived electrospun materials, specifically focusing on their application in tissue regeneration (including cartilage, cornea, nerves, blood vessels, bones, and skin), disease treatment (such as cancer and diabetes), and the development of controlled drug delivery systems. Additionally, we explore the potential future trends in utilizing these nanofibrous materials for creating intelligent biomaterials, incorporating biosensors and wearable sensors for monitoring human health, and also discuss the bottlenecks for its widespread use. This comprehensive overview illuminates the significant impact and exciting prospects of SF-derived electrospun materials in advancing biomedical research and applications.

Synthesis and Characterization of ABA-Type Triblock Copolymers Using Novel Bifunctional PS, PMMA, and PCL Macroinitiators Bearing p-xylene-bis(2-mercaptoethyloxy) Core

Syntheses of novel bifunctional poly(methyl methacrylate) (PMMA)-, poly(styrene) (PS)-, and (poly ε-caprolactone) (PCL)-based atom transfer radical polymerization (ATRP) macroinitiators derived from p-xylene-bis(1-hydroxy-3-thia-propanoloxy) core were carried out to obtain ABA-type block copolymers. Firstly, a novel bifunctional ATRP initiator, 1,4-phenylenebis(methylene-thioethane-2,1-diyl)bis(2-bromo-2-methylpropanoat) (PXTBR), synthesized the reaction of p-xylene-bis(1-hydroxy-3-thia-propane) (PXTOH) with α-bromoisobutryl bromide. The PMMA and PS macroinitiators were prepared by ATRP of methyl methacrylate (MMA) and styrene (S) as monomers using (PXTBR) as the initiator and copper(I) bromide/N,N,N',N″,N″-pentamethyldiethylenetriamine (CuBr/PMDETA) as a catalyst system. Secondly, di(α-bromoester) end-functionalized PCL-based ATRP macronitiator (PXTPCLBr) was prepared by esterification of hydroxyl end groups of PCL-diol (PXTPCLOH) synthesized by Sn(Oct)2-catalyzed ring opening polymerization (ROP) of ε-CL in bulk using (PXTOH) as initiator. Finally, ABA-type block copolymers, PXT(PS-b-PMMA-b-PS), PXT(PMMA-b-PS-b-PMMA), PXT(PS-b-PCL-b-PS), and PXT(PMMA-b-PCL-b-PMMA), were synthesized by ATRP of MMA and S as monomers using PMMA-, PS-, and PCL-based macroinitiators in the presence of CuBr/PMDETA as the catalyst system in toluene or N,N-dimethylformamide (DMF) at different temperatures. In addition, the extraction abilities of PCL and PS were investigated under liquid-liquid phase conditions using heavy metal picrates (Ag+, Cd2+, Cu2+, Hg2+, Pb2+, and Zn2+) as substrates and measuring with UV-Vis the amounts of picrate in the 1,2-dichloroethane phase before and after treatment with the polymers. The extraction affinity of PXTPCL and PXTPS for Hg2+ was found to be highest in the liquid-liquid phase extraction experiments. Characterizations of the molecular structures for synthesized novel initiators, macroinitiators, and the block copolymers were made by spectroscopic (FT-IR, ESI-MS, 1H NMR, 13C NMR), DSC, TGA, chromatographic (GPC), and morphologic SEM.

Fabrication and Characterization of Electrospun Poly(Caprolactone)/Tannic Acid Scaffold as an Antibacterial Wound Dressing

Antibacterial wound dressings are promising materials to treat infected skin wounds, which greatly affect the wound-healing process. In this study, tannic acid (TA), a natural antibacterial agent, was successfully loaded by electrospinning into poly(caprolactone) (PCL) fibers in a high concentration. It is suggested that the addition of TA was beneficial for producing uniform and continuous PCL nanofibers. Hydrogen bonds existed between the PCL and TA molecules based on the analysis of FTIR spectra and DSC results. The interactions and continuous network improved the mechanical properties of the scaffolds. Meanwhile, increasing the amount of TA also enhanced the hydrophilicity and water absorption capacity of the scaffold, both of which are beneficial for accelerating wound healing. Moreover, a burst release of the TA in the initial stage and a controlled, steady release behavior over time contributed to the highly antibacterial properties of the PCL/TA scaffolds. The fabrication of the composite scaffold supplies a facile, efficient, and controllable approach to address the issue of antibacterial treatment in wound dressing.

A Compilation of Study Models for Dental Pulp Regeneration

Efforts to heal damaged pulp tissue through tissue engineering have produced positive results in pilot trials. However, the differentiation between real regeneration and mere repair is not possible through clinical measures. Therefore, preclinical study models are still of great importance, both to gain insights into treatment outcomes on tissue and cell levels and to develop further concepts for dental pulp regeneration. This review aims at compiling information about different in vitro and in vivo ectopic, semiorthotopic, and orthotopic models. In this context, the differences between monolayer and three-dimensional cell cultures are discussed, a semiorthotopic transplantation model is introduced as an in vivo model for dental pulp regeneration, and finally, different animal models used for in vivo orthotopic investigations are presented.

Ancient fibrous biomaterials from silkworm protein fibroin and spider silk blends: Biomechanical patterns

Silkworm silk protein fibroin and spider silk spidroin are known biocompatible and natural biodegradable polymers in biomedical applications. The presence of β-sheets in silk fibroin and spider spidroin conformation improves their mechanical properties. The strength and toughness of pure recombinant silkworm fibroin and spidroin are relatively low due to reduced molecular weight. Hence, blending is the foremost approach of recent studies to optimize silk fibroin and spidroin's mechanical properties. As summarised in the present review, numerous research investigations evaluate the blending of natural and synthetic polymers. The effects of blending silk fibroin and spidroin with natural and synthetic polymers on the mechanical properties are discussed in this review article. Indeed, combining natural and synthetic polymers with silk fibroin and spidroin changes their conformation and structure, fine-tuning the blends' mechanical properties. STATEMENT OF SIGNIFICANCE: Silkworm and spider silk proteins (silk fibroin and spidroin) are biocompatible and biodegradable natural polymers having different types of biomedical applications. Their mechanical and biological properties may be tuned through various strategies such as blending, conjugating and cross-linking. Blending is the most common method to modify fibroin and spidroin properties on demand, this review article aims to categorize and evaluate the effects of blending fibroin and spidroin with different natural and synthetic polymers. Increased polarity and hydrophilicity end to hydrogen bonding triggered conformational change in fibroin and spidroin blends. The effect of polarity and hydrophilicity of the blending compound is discussed and categorized to a combinatorial, synergistic and indirect impacts. This outlook guides us to choose the blending compounds mindfully as this mixing affects the biochemical and biophysical characteristics of the biomaterials.

Nonmulberry silk fibroin-based biomaterials: Impact on cell behavior regulation and tissue regeneration

Silk fibroin (SF) is a promising biomaterial due to its good biocompatibility, easy availability, and high mechanical properties. Compared with mulberry silk fibroin (MSF), nonmulberry silk fibroin (NSF) isolated from typical nonmulberry silkworm silk exhibits unique arginine-glycine-aspartic acid (RGD) sequences with favorable cell adhesion enhancing effect. This inherent property probably makes the NSF more suitable for cell culture and tissue regeneration-related applications. Accordingly, various types of NSF-based biomaterials, such as particles, films, fiber mats, and 3D scaffolds, are constructed and their application potential in different biomedical fields is extensively investigated. Based on these promising NSF biomaterials, this review firstly makes a systematical comparison between the molecular structure and properties of MSF and typical NSF and highlights the unique properties of NSF. In addition, we summarize the effective fabrication strategies from degummed nonmulberry silk fibers to regenerated NSF-based biomaterials with controllable formats and their recent application progresses in cell behavior regulation and tissue regeneration. Finally, current challenges and future perspectives for the fabrication and application of NSF-based biomaterials are discussed. Related research and perspectives may provide valuable references for designing and modifying effective NSF-based and other natural biomaterials. STATEMENT OF SIGNIFICANCE: There exist many reviews about mulberry silk fibroin (MSF) biomaterials and their biomedical applications, while that about nonmulberry silk fibroin (NSF) biomaterials is scarce. Compared with MSF, NSF exhibits unique arginine-glycine-aspartic acid sequences with promising cell adhesion enhancing effect, which makes NSF more suitable for cell culture and tissue regeneration related applications. Focusing on these advanced NSF biomaterials, this review has systematically compared the structure and properties of MSF and NSF, and emphasized the unique properties of NSF. Following that, the effective construction strategies for NSF-based biomaterials are summarized, and their recent applications in cell behavior regulations and tissue regenerations are highlighted. Furthermore, current challenges and future perspectives for the fabrication and application of NSF-based biomaterials were discussed.

Biological Efficacy Comparison of Natural Tussah Silk and Mulberry Silk Nanofiber Membranes for Guided Bone Regeneration

Biopolymer nanofiber membranes are attracting interest as promising biomaterial scaffolds with a remarkable range of structural and functional performances for guided bone regeneration (GBR). In this study, tussah silk nanofiber (TSn) and Bombyx mori silk nanofiber (BSn) membranes were prepared by physical shearing. The diameters of the TSn and BSn membranes were 146.09 ± 63.56 and 120.99 ± 91.32 nm, respectively. TSn showed a Young's modulus of 3.61 ± 0.64 GPa and a tensile strength of 74.27 ± 5.19 MPa, which were superior to those of BSn, with a Young's modulus of 0.16 ± 0.03 GPa and a tensile strength of 4.86 ± 0.61 MPa. The potential of TSn and BSn membranes to guide bone regeneration was explored. In vitro, the TSn membrane exhibited significantly higher cell proliferation for MC3T3-E1 cells than the BSn membrane. In a cranial bone defect in a rat model, the TSn and BSn membranes displayed superior bone regeneration compared to the control because the membrane prevented the ingrowth of soft tissue to the defective area. Compared to the BSn membrane, the TSn membrane improved damaged bone regeneration, presumably due to its superior mechanical properties, high osteoconductivity, and increased cell proliferation. The TSn membrane has a bionic structure, excellent mechanical properties, and greater biocompatibility, making it an ideal candidate for GBR.

A critical analysis of research methods and biological experimental models to study pulp regeneration

With advances in knowledge and treatment options, pulp regeneration is now a clear objective in clinical dental practice. For this purpose, many methodologies have been developed in attempts to address the putative questions raised both in research and in clinical practice. In the first part of this review, laboratory‐based methods will be presented, analysing the advantages, disadvantages, and benefits of cell culture methodologies and ectopic/semiorthotopic animal studies. This will also demonstrate the need for alignment between two‐dimensional and three‐dimensional laboratory techniques to accomplish the range of objectives in terms of cell responses and tissue differentiation. The second part will cover observations relating to orthotopic animal studies, describing the current models used for this purpose and how they contribute to the translation of regenerative techniques to the clinic.

Robust Nanofiber Mats Exfoliated From Tussah Silk for Potential Biomedical Applications

Nanofibers as elements for bioscaffolds are pushing the development of tissue engineering. In this study, tussah silk was mechanically disintegrated into nanofibers dispersed in aqueous solution which was cast to generate tussah silk fibroin (TSF) nanofiber mats. The effect of treatment time on the morphology, structure, and mechanical properties of nanofiber mats was examined. SEM indicated decreasing diameter of the nanofiber with shearing time, and the diameter of the nanofiber was 139.7 nm after 30 min treatment. These nanofiber mats exhibited excellent mechanical properties; the breaking strength increased from 26.31 to 72.68 MPa with the decrease of fiber diameter from 196.5 to 139.7 nm. The particulate debris was observed on protease XIV degraded nanofiber mats, and the weight loss was greater than 10% after 30 days in vitro degradation. The cell compatibility experiment confirmed adhesion and spreading of NIH-3T3 cells and enhanced cell proliferation on TSF nanofiber mats compared to that on Bombyx mori silk nanofiber mats. In conclusion, results indicate that TSF nanofiber mats prepared in this study are mechanically robust, slow biodegradable, and biocompatible materials, and have promising application in regenerative medicine.

Osteoblast-derived extracellular matrix coated PLLA/silk fibroin composite nanofibers promote osteogenic differentiation of bone mesenchymal stem cells

Poly-L-lactic acid (PLLA) is one of the most commonly used synthetic materials for regenerative medicine, and silk fibroin (SF) is a natural protein with excellent biocompatibility. Combination of PLLA and SF in a proper proportion by electrospinning may generate composite nanofibers that could meet the requirements of scaffolding in bone tissue engineering. The application of PLLA/SF nanofibrous scaffold for osteogenesis is well established in vitro and in vivo. However, PLLA/SF nanofibrous scaffold does not have an ideal ability to promote cell adhesion, proliferation, and differentiation. Extracellular matrix (ECM) plays a critical role in modulating cellular behavior. However, the role of combination of natural ECM with nanofibrous scaffold in regulating osteogenic differentiation is unclear. In this study, we aimed to develop a novel composite PLLA/SF nanofibrous scaffold coated with osteoblast-derived extracellular matrix (O-ECM/PLLA/SF) and analyze the effects of the modified scaffold on osteogenic differentiation of BMSCs. The surface structural features and compositions of the O-ECM/PLLA/SF scaffold were characterized by SEM and immunofluorescence staining. The capacities of the O-ECM/PLLA/SF scaffold to induce osteogenic differentiation of BMSCs were investigated by alkaline phosphatase (ALP) and alizarin red staining (ARS). The results showed BMSCs cultured on O-ECM/PLLA/SF scaffold significantly increased osteogenic differentiation compared with cells cultured individually on a scaffold or O-ECM. Collectively, these findings indicate that O-ECM-coated nanofibrous scaffold can be a promising strategy for osteogenic differentiation of BMSCs, opening a new possibility of utilizing composite scaffolds for bone tissue engineering.

PCL/Andiroba Oil (Carapa guianensis Aubl.) Hybrid Film for Wound Healing Applications

Developing a biomimetic material to wound care is an emerging need for the healing process. Poly (ε-caprolactone) (PCL) is a polymer with the necessary dressing's requirements often used in medicine. Their surface, physic-chemical and biological properties can be modified by adding bioactive compounds, such as andiroba seed oil (Carapa guianensis). This Amazonian natural plant has medicinal and pharmacological properties. For this purpose, PCL polymeric films incorporated with andiroba oil were investigated. The synthesis of hybrids materials was carried out in the solvent casting method. Thermal properties were evaluated using thermogravimetric analysis (TGA/DTGA) and differential scanning calorimetry (DSC). The solvent type on the surface and hydrophilicity of samples was studied using a scanning electron microscope (SEM). Additionally, contact angle measurements, functional groups analysis, fluid absorption capacity, and cell viability were performed. The results demonstrated the influences of andiroba oil under the morphology and thermal properties of the polymeric matrix; the hydrophilicity of the hybrid film obtained by acetic acid was reduced by 13%; the porosity decreased as the concentration of oil increased, but its higher thermal stability. The L929 cell line's proliferation was observed in all materials, and it presented nontoxic nature. It was demonstrated the ability of PCL hybrid film as a matrix for cell growth. Then, the materials were proved potential candidates for biomedical applications.

Electrospun regenerated Antheraea pernyi silk fibroin scaffolds with improved pore size, mechanical properties and cytocompatibility using mesh collectors

Generally, electrospun silk fibroin scaffolds collected by traditional plates present limited pore size and mechanical properties, which may restrict their biomedical applications. Herein, regenerated Antheraea pernyi silk fibroin (RASF) with excellent inherent cell adhesion property was chosen as a raw material and the conductive metal meshes were used as collectors to prepare modified RASF scaffolds by electrospinning from its aqueous solution. A traditional intact plate was used as a control. The morphology and mechanical properties of the obtained scaffolds were investigated. Schwann cells were further used to assess the cytocompatibility and cell migration ability of the typical scaffolds. Interestingly, compared with the traditional intact plate, the mesh collector with an appropriate gap size (circa 7 mm) could significantly improve the pore size, porosity and mechanical properties of the RASF scaffolds simultaneously. In addition, the scaffold collected under this condition (RASF-7mmG) showed higher cell viability, deeper cell permeation and faster cell migration of Schwann cells. Combined with the excellent inherent properties of ASF and the obviously enhanced scaffold cytocompatibility and mechanical properties, the RASF-7mmG scaffold is expected to be a candidate with great potential for biomedical applications.

Taguchi's methods to optimize the properties and bioactivity of 3D printed polycaprolactone/mineral trioxide aggregate scaffold: Theoretical predictions and experimental validation

Mineral trioxide aggregate (MTA) can provide bioactivity to poly-caprolactone (PCL), which is an inert polymer used to print scaffolds. However, testing all combinations of scaffold characteristics (e.g., composition, pore size, and distribution) to optimize properties of scaffolds is time-consuming and costly. The Taguchi's methods can identify characteristics that have major influences on the properties of complex designs, hence decreasing the number of combinations to be tested. The objective was to assess the potential of Taguchi's methods as a predictive tool for the optimization of bioactive scaffold printed using electro-hydro dynamic jetting. A three-level approach assessed the influence of PCL/MTA proportion, pore size, fiber dimension and number of layers in pH, degradation rate, porosity, yield strength, and Young's modulus. Data were analyzed using Tukey's honest significant difference test, analysis of mean and signal-to-noise ratio (S/N) test. Cytocompatibility and differentiation potential were assessed for 5 and 30 days using dental pulp stem cells and analyzed with one-way analysis of variance (proliferation) or Mann-Whitney (qPCR). The S/N ratio and analysis of mean showed that fiber diameter and composition were the most influential characteristics in all properties. The experimental data confirmed that the addition of MTA to PCL increased the pH and scaffold degradation. Only PCL and PCL with 4% MTA allowed cell proliferation. The latter increased the genetic expression of ALP, COL-1, OCN, and MSX-1. The theoretical predictions were confirmed by the experiments. The Taguchi's identified the inputs that can be disregarded to optimize 3D printed meshed bioactive scaffolds.

Scaffolding polymeric biomaterials: Are naturally occurring biological macromolecules more appropriate for tissue engineering?

Nowadays, tissue and organ failures resulted from injury, aging accounts, diseases or other type of damages is one of the most important health problems with an increasing incidence worldwide. Current treatments have limitations including, low graft efficiency, shortage of donor organs, as well as immunological problems. In this context, tissue engineering (TE) was introduced as a novel and versatile approach for restoring tissue/organ function using living cells, scaffold and bioactive (macro-)molecules. Among these, scaffold as a three-dimensional (3D) support material, provide physical and chemical cues for seeding cells and has an essential role in cell missions. Among the wide verity of scaffolding materials, natural or synthetic biopolymers are the most commonly biomaterials mainly due to their unique physicochemical and biological features. In this context, naturally occurring biological macromolecules are particular of interest owing to their low immunogenicity, excellent biocompatibility and cytocompatibility, as well as antigenicity that qualified them as popular choices for scaffolding applications. In this review, we highlighted the potentials of natural and synthetic polymers as scaffolding materials. The properties, advantages, and disadvantages of both polymer types as well as the current status, challenges, and recent progresses regarding the application of them as scaffolding biomaterials are also discussed.

Regenerated Antheraea pernyi Silk Fibroin/Poly(N-isopropylacrylamide) Thermosensitive Composite Hydrogel with Improved Mechanical Strength

At present, Antheraea pernyi silk fibroin (ASF) has attracted research efforts to investigate it as a raw material for fabrication of biomedical devices because of its superior cytocompatibility. Nevertheless, native ASF is not easily processed into a hydrogel without any crosslinking agent, and a single hydrogel shows poor mechanical properties. In this paper, a series of ASF/poly (N-isopropylacrylamide) (PNIPAAm) composite hydrogels with different ASF contents were manufactured by a simple in situ polymerization method without any crosslinking agent. Meanwhile, the structures, morphologies and thermal properties of composite hydrogels were investigated by XRD, FTIR, SEM, DSC and TGA, respectively. The results indicate that the secondary structure of silk in the composite hydrogel can be controlled by changing the ASF content and the thermal stability of composite hydrogels is enhanced with an increase in crystalline structure. The composite hydrogels showed similar lower critical solution temperatures (LCST) at about 32 °C, which matched well with the LCST of PNIPAAm. Finally, the obtained thermosensitive composite hydrogels exhibited enhanced mechanical properties, which can be tuned by varying the content of ASF. This strategy to prepare an ASF-based responsive composite hydrogel with enhanced mechanical properties represents a valuable route for developing the fields of ASF, and, furthermore, their attractive applications can meet the needs of different biomaterial fields.