Facile In Situ Assembly of Nanofibers within Three-Dimensional Porous Matrices with Arbitrary Characteristics for Creating Biomimetic Architectures.

It is challenging to recapitulate the natural extracellular matrix's hierarchical nano/microfibrous three-dimensional (3D) structure with multilevel pores, good mechanical and hydrophilic properties, and excellent bioactivity for designing and developing advanced biomimetic materials. This work reports a new facile strategy for the scalable manufacturing of such a 3D architecture. Natural polymers in an aqueous solution are interpenetrated into a 3D microfibrous matrix with arbitrary shapes and property characteristics to self-assemble in situ into a nanofibrous network. The collagen fiber-like hierarchical structure and interconnected multilevel pores are achieved by self-assembly of the formed nanofibers within the 3D matrix, triggered by a simple cross-linking treatment. The as-prepared alginate/polypropylene biomimetic matrices are bioactive and have a tunable mechanical property (compressive modulus from ∼17 to ∼24 kPa) and a tunable hydrophilicity (water contact angle from ∼94° to 63°). This facile and versatile strategy allows eco-friendly and scalable manufacturing of diverse biomimetic matrices or modification of any existing porous matrices using different polymers.

Strontium-doped mesoporous bioglass nanoparticles for enhanced wound healing with rapid vascularization.

Tissue engineered skin and its substitutes have a promising future in wound healing. However, enabling fast formation of blood vessels during the wound healing process is still a huge challenge to the currently available wound substitutes. In this work, active mesoporous bioglass nanoparticles with a high specific surface area and doped with strontium (Sr) were fabricated for rapid microvascularization and wound healing. The as-prepared bioglass nanoparticles with Sr ions significantly promoted the proliferation of fibroblasts and microvascularization of human umbilical vein endothelial cells in vitro. Silk fibroin sponges encapsulating the nanoparticles accelerated wound healing by promoting the formation of blood vessels and epithelium in vivo. This work provides a strategy for the design and development of active biomaterials for enhancing wound healing by rapid vascularization and epithelial reconstruction.

Hyalase-Mediated Cascade Degradation of a Matrix Barrier and Immune Cell Penetration by a Photothermal Microneedle for Efficient Anticancer Therapy.

For melanoma with high lethality and metastasis rate, traditional therapy has limited effects; local photothermal therapy (PTT) synergetic with immune therapy for cancer treatment can perhaps improve the situation. However, because of the natural existence of the tumor matrix barrier, the penetration depth of drugs and immune cells often dampens the efficacy of cancer treatment. Herein, we report an innovative synergetic PTT and immune therapy through dissolving microneedles for the codelivery of the hyaluronidase-modified semiconductor polymer nanoparticles containing poly(cyclopentadithiophene-alt-benzothiadiazole) and immune adjuvant polyinosinic-polycytidylic acid (PIC). Benefiting from the dissolution of an extracellular matrix of hyaluronidase, the semiconductor polymer nanoparticles and PIC penetrate the tumor deeply, under synergetic therapy with PTT, activating the immune cells and enhancing the T-cell immune response for inhibition of tumor growth and metastasis. This study provides a promising platform for effective melanoma treatment and a novel strategy to overcome the stromal barrier.

Bioactive hierarchical silk fibers created by bioinspired self-assembly.

Artificial recapitulation of the hierarchy of natural protein fibers is crucial to providing strategies for developing advanced fibrous materials. However, it is challenging due to the complexity of the natural environment. Inspired by the liquid crystalline spinning of spiders, we report the development of natural silk-like hierarchical fibers, with bundles of nanofibrils aligned in their long-axis direction, by self-assembly of crystallized silk fibroin (SF) droplets. The formation of self-assembled SF fibers is a process of coalesced droplets sprouting to form a branched fibrous network, which is similar to the development of capillaries in our body. The as-assembled hierarchical SF fibers are highly bioactive and can significantly enhance the spreading and growth of human umbilical vein endothelial cells compared to the natural SF fibers. This work could help to understand the natural silk spinning process of spiders and provides a strategy for design and development of advanced fibrous biomaterials for various applications.

Constructing 3D Macroporous Microfibrous Scaffolds with a Featured Surface by Heat Welding and Embossing.

Three-dimensional (3D) microfibrous scaffolds hold great promise for biomedical applications due to their good mechanical properties and biomimetic structure similar to that of the fibrous natural extracellular matrix. However, the large diameter and smooth surface of microfibers provide limited cues for regulating cell activity and behaviors. In this work, we report a facile heat-welding-and-embossing strategy to develop 3D macroporous microfibrous scaffolds with a featured surface topography. Here, solid monosodium glutamate (MSG) particles with crystalline ridge-like surface features play a key role as templates in both the formation of scaffold pores and the surface embossing of scaffold fibers when short thermoplastic polypropylene microfibers were heat-welded. The embossing process can be programmed by adjusting heating temperatures and MSG/fiber ratios. Compared to traditional 3D microfibrous scaffolds, the as-welded 3D scaffolds show higher compressive strength and modulus. Taking mouse C2C12 myoblasts as a model cell line, the scaffolds with embossed surface features significantly promoted the growth of cells, interactions of cells and scaffolds, and formation of myotubes. The findings indicate that the as-prepared 3D scaffolds are a good platform for cell culture study. The facile strategy can be applied to fabricate different fibrous scaffolds by changing the combination of templates and thermoplastic polymer fibers with a melting temperature lower than that of the template. The obtained insights in this work could provide a guide and inspiration for the design and fabrication of functional 3D fibrous scaffolds.

Helicobacter pylori Ribosomal Protein-A2 Peptide/Silk Fibroin Nanofibrous Composites as Potential Wound Dressing.

Although different kinds of antibacterial formulas have been explored against bacterial infections, the development of both biocompatible and efficiently antibacterial matrices is still a challenge. In this study, we report a novel HPRP-A2 antimicrobial peptide/silk fibroin (SF) composite nanofibrous matrix fabricated by an all-aqueous electrospinning process (HPRP-A2 is an antibacterial peptide originated from Helicobacter pylori). The HPRP-A2/SF composite nanofibers had a round and smooth morphology. The incorporation of HPRP-A2 had little influence on both the morphology and biocompatibility of the SF nanofibers. Interestingly, the composite nanofibrous matrices showed an impressive antimicrobial activity against both Gram-positive and Gram-negative bacteria. Furthermore, the HPRP-A2/SF composite nanofibers showed excellent performance on accelerating healing of wound according to the data of animal experiment. Considering the facile and all-aqueous process, the HPRP-A2/SF composite nanofibrous matrices could be a promising candidate for antibacterial or wound management applications.

Fabrication of a cost-effective lemongrass (Cymbopogon citratus) membrane with antibacterial activity for dye removal.

Dye wastewater has attracted much attention due to its severe environmental and health problems. The main challenge of separating dyes from wastewater, using adsorption, is developing a functional adsorbent that is cost-effective and sustainable. In this work, we have fabricated a novel low-cost membrane with antibacterial properties from naturally sustainable lemongrass (LG). Lemongrass was cut and milled into powder, then dissolved to prepare a lemongrass membrane. Graphene oxide (GO) was also included to prepare a LG/GO composite membrane. The physiochemical and antibacterial properties of membranes were evaluated and their dye adsorption capability was examined using methylene blue (MB) dye at different concentrations. The kinetic study revealed that the MB adsorption process complied with the pseudo second-order model. The lemongrass membrane showed a rough surface morphology, high reduced modulus and hardness, yet comparable dye adsorption to the LG/GO composite membrane. Considering the natural sustainability of lemongrass as an abundant cellulosic resource, its excellent dye adsorption, antibacterial properties and low cost as well as the facile fabrication technology, the lemongrass membrane could be a promising candidate for dye removal from wastewater with easy separation after use.

Yolk-porous shell nanospheres from siliver-decorated titanium dioxide and silicon dioxide as an enhanced visible-light photocatalyst with guaranteed shielding for organic carrier.

A nagging problem for the decompostion of photocatalyst organic carrier can be expected to be resolved by shielding effect from our yolk-porous shell nanospheres. The nanospheres were synthesized by a facile strategy: polyporrole (PPy) and silver were deposited together on TiO2 by chemical oxidative polymerization; then PPy/Ag-coated TiO2 nanoparticles were encapsulated in silicon dioxide (SiO2) shell with polyethylene glycol (PEG) as a pore-forming agent via sol-gel method based on hydrolysis of tetraethyl orthosilicate (TEOS). After removing intermediary PPy between yolk and shell by calcination and washing off PEG in shell, yolk-porous shell (SiO2@void@Ag/TiO2) nanospheres were formed. The voids in SiO2@void@Ag/TiO2 can serve as photocatalytic reactors. The channels in porous shell at outer layer provide passages for light transmission, dye molecule accessing and degradants out. More importantly, the euphotic and porous shell exhibited an impressive protection to organic carrier, lest unfavorable decomposition occurred. Yolk-porous shell nanospheres showed commendable performance with >99.5% of dye removal efficiency under 3 h visible light irradiation, higher than pristine TiO2 and Ag/TiO2 nanoparticles, due to the synergy effect of robust adsorption capacity and photocatalysis. Our work could provide a good strategy for developing novel carrier-based photocatalysts for environmental remediation application, which can be readily extended to the combination of other nanophotocatalysts and organic carriers for enhancing sustainable photocatalytic performance.

Creating Biomimetic Anisotropic Architectures with Co-Aligned Nanofibers and Macrochannels by Manipulating Ice Crystallization.

The continuous evolution of tissue engineering scaffolds has been driven by the desire to recapitulate structural features and functions of the natural extracellular matrix (ECM). However, it is still an extreme challenge to create a three-dimensional (3D) scaffold with both aligned nanofibers and aligned interconnected macrochannels to mimic the ECM of anisotropic tissues. Here, we develop a facile strategy to create such a scaffold composed of oriented nanofibers and interconnected macrochannels in the same direction, with various natural polymers typically used for tissue regeneration. The orientation of nanofibers and interconnected macrochannels can be easily tuned by manipulating ice crystallization. The scaffold demonstrates both structural and functional features similar to the natural ECM of anisotropic tissues. Taking silk fibroin as an example, the scaffold with radially oriented nanofibers and interconnected macrochannels is more efficient for capturing cells and promoting the growth of both nonadherent embryonic dorsal root ganglion neurons (DRGs) and adherent human umbilical vein endothelial cells (HUVECs) compared to the widely used scaffold types. Interestingly, DRGs and neurites on the SF scaffold demonstrate a 3D growth mode similar to that of natural nerve tissues. Furthermore, the coaligned nanofibers and macrochannels of the scaffold can direct HUVECs to assemble into blood vessel-like structures and their collagen deposition in their arrangement direction. The strategy could inspire the design and development of multifunctional 3D scaffolds with desirable structural features for engineering different tissues.

Manipulating the fractal fiber network of a molecular gel with surfactants.

Supramolecular assembly governs the formation and properties of many soft materials. Hence, it is significant to develop convenient approaches to control the assembly process. In this work, it is demonstrated that by using surfactants consisting of a sorbitan group (either ethoxylated or not) and an aliphatic chain, as additives, the fractal fiber network structure of a π gelator (with two alkyl chains) can be engineered. The two surfactants, which have the same hydrophobic tails but different hydrophilic heads, demonstrate different effects on the fiber network of the gelator. The surfactant with a large hydrophilic head (ethoxylated sorbitan) promotes fiber tip branching and that with a smaller hydrophilic head (non-ethoxylated sorbitan) enhances fiber side branching. Fractal analysis based on the Avrami model also demonstrates enhancement of fiber branching by the surfactants. Furthermore, the fluorescence emission of the gelator is enhanced by more than 30%. The observations have significant implications in engineering a class of supramolecular materials.

Silk patterns made by direct femtosecond laser writing.

Silk patterns in a film of amorphous water-soluble fibroin are created by tailored exposure to femtosecond-laser pulses (1030 nm/230 fs) without the use of photo-initiators. This shows that amorphous silk can be used as a negative tone photo-resist. It is also shown that water insoluble crystalline silk films can be precisely ablated from a glass substrate achieving the patterns of crystalline silk gratings on a glass substrate. Bio-compatible/degradable silk can be laser structured to achieve conformational transformations as demonstrated by infrared spectroscopy.

Green electrospun grape seed extract-loaded silk fibroin nanofibrous mats with excellent cytocompatibility and antioxidant effect.

Silk fibroin (SF) from Bombyx mori has an excellent biocompatibility and thus be widely applied in the biomedical field. Recently, various SF-based composite nanofibers have been developed for more demanding applications. Additionally, grape seed extract (GSE) has been demonstrated to be powerful on antioxidation. In the present study, we dedicate to fabricate a GSE-loaded SF/polyethylene oxide (PEO) composite nanofiber by green electrospinning. Our results indicated the successful loading of GSE into the SF/PEO composite nanofibers. The introduction of GSE did not affect the morphology of the SF/PEO nanofibers and GSE can be released from the nanofibers with a sustained manner. Furthermore, comparing with the raw SF/PEO nanofibrous mats, the GSE-loaded SF/PEO nanofibrous mats significantly enhanced the proliferation of the skin fibroblasts and also protected them against the damage from tert-butyl hydroperoxide-induced oxidative stress. All these findings suggest a promising potential of this novel GSE-loaded SF/PEO composite nanofibrous mats applied in skin care, tissue regeneration and wound healing.

Green electrospun pantothenic acid/silk fibroin composite nanofibers: fabrication, characterization and biological activity.

Silk fibroin (SF) from Bombyx mori has many established excellent properties and has found various applications in the biomedical field. However, some abilities or capacities of SF still need improving to meet the need for using practically. Indeed, diverse SF-based composite biomaterials have been developed. Here we report the feasibility of fabricating pantothenic acid (vitamin B5, VB5)-reinforcing SF nanofibrous matrices for biomedical applications through green electrospinning. Results demonstrated the successful loading of D-pantothenic acid hemicalcium salt (VB5-hs) into resulting composite nanofibers. The introduction of VB5-hs did not alter the smooth ribbon-like morphology and the silk I structure of SF, but significantly decreased the mean width of SF fibers. SF conformation transformed into ß-sheet from random coil when composite nanofibrous matrices were exposed to 75% (v/v) ethanol vapor. Furthermore, nanofibers still remained good morphology after being soaked in water environment for five days. Interestingly, as-prepared composite nanofibrous matrices supported a higher level of cell viability, especially in a long culture period and significantly assisted skin cells to survive under oxidative stress compared with pure SF nanofibrous matrices. These findings provide a basis for further extending the application of SF in the biomedical field, especially in the personal skin-care field.

Vitamin E-loaded silk fibroin nanofibrous mats fabricated by green process for skin care application.

In the present study, we reported fabrication and skin benefit of a novel vitamin E (VE)-loaded silk fibroin (SF) nanofibrous mats. RRR-α-Tocopherol polyethylene glycol 1000 succinate (VE TPGS), a water-soluble derivative of VE, was incorporated into SF nanofiber successfully by aqua solution electrospinning for the first time. Morphology of the composite nanofibers changed with the different amount of VE TPGS: a ribbon-like shape for lower loading dose of VE TPGS, while a round shape for higher loading dose (more than 4% (wt/wt) based on the weight of SF). After treated with 75% (v/v) ethanol vapor, the composite nanofibrous mats showed an excellent water-resistant ability. In vitro study disclosed a sustained release behavior of VE TPGS disassociated from the nanofibrous mats. The mouse skin fibroblasts (L929 cells) cultured on the VE-loaded SF nanofibrous mats spread and proliferated much better than on cover slips. Moreover, the incorporation of VE TPGS was found strengthening the ability of SF nanofibrous mats on protecting the cells against oxidation stress induced by tert-butyl hydroperoxide. Our data presented impressive skin benefits of this VE-loaded SF nanofibrous mats, suggesting a promising applicative potential of this novel product on personal skin care, tissue regeneration and other related area.

Regenerated silk fibroin nanofibrous matrices treated with 75% ethanol vapor for tissue-engineering applications.

As an excellent biocompatible and biodegradable protein polymer, silk fibroin (SF) has found wide applications, particularly serving as therapeutic agent for tissue-engineering applications, on which both post-spin treatment and sterilization processing are crucial to drug-loaded matrices. To find a safe, effective and appropriate post-spin treatment and sterilization approach for drug-loaded biomaterial matrices is one of the major problems in the field of tissue engineering at present. In this work, a simple, safe and effective approach skillfully integrating post-spin treatment with sterilization processing was developed to drug-loaded SF nanofibrous matrices. Electrospun SF nanofibrous matrices from its aqueous solution were post-treated with 75% ethanol vapor. (13)C-NMR and WAXD analysis demonstrated that such post-spin treatment rendered the structure of SF nanofibrous matrices transform from the silk I form to the silk II form. Furthermore, biological assays suggested that as-treated SF nanofibrous matrices significantly promoted the development of murine connective tissue fibroblasts. Skillfully integrated with novel sterilization processing, 75% ethanol vapor treatment could be a potential approach to designing and fabricating diverse drug-loaded SF nanofibrous matrices serving as therapeutic agents for tissue-engineering applications in that it can effectively protect the drug from losing compared with traditional post-spin treatment and sterilization processing.

Electrospun biomimic nanofibrous scaffolds of silk fibroin/hyaluronic acid for tissue engineering.

This study aimed to fabricate nanofibrous scaffolds which could biomimic the natural extracellular matrix from aqueous solutions of silk fibroin and hyaluronic acid blends (SF/HA) by means of electrospinning. Scanning electronic microscopy results indicated that electrospun SF/HA nanofibers were ribbon-shaped and their average width obviously decreased with the increase of HA content. However, there is no fiber observed when the volume of HA further increased to 50% of overall volume. After being treated with 75% ethanol vapor for 24 h, the fibers still remained their fibrous morphologies and presented good capability of water-resistance. Fourier transform infrared attenuated total reflectance spectroscopy, (13)C-CP-MAS nuclear magnetic resonance and differential scanning calorimetry results revealed that HA did not induce SF conformation from random coil to ß-sheet. SF conformation converted from random coil to ß-sheet after being treated with 75% ethanol vapor. Cell viability studies demonstrated that SF/HA nanofibrous scaffolds significantly promoted cell proliferation. Electrospun SF/HA nanofibers may provide an ideal biomimic tissue-engineering scaffold or vehicle for water-soluble drugs.

Crosslinking of poly(L-lactide) nanofibers with triallyl isocyanutrate by gamma-irradiation for tissue engineering application.

The radiation crosslinked poly(L-lactide) (PLLA) electrospun nanofibers have been developed with improved thermal stability and mechanical properties. Trially isocyanurate (TAIC) were added into PLLA solution at different weight ratios (1, 3, and 5%) and electrospun into nanofibrous mats, the mats were then irradiated by gamma ray at different radiation doses (5, 10, and 25 kGy) to crosslink the PLLA chains. Their surface morphology, thermal properties, mechanical properties, and biodegradation properties were investigated and compared before and after gamma irradiation. Furthermore, the in vitro biocompatibilities were also evaluated by using mouse L929 fibroblasts. The results indicated that the efficient crosslinking networks can be generated when the TAIC content is higher than 3%. The thermal stability and tensile mechanical properties were significantly increased at higher irradiation dose of 10 and 25 kGy. However, radiation dose at 25 kGy have an adverse effect on the thermal stability of crosslinked samples due to thermal degradation induced by irradiation, the crosslinked samples irradiated at 10 kGy exhibited the best enzymatic degradation. The in vitro results also revealed that the crosslinked PLLA/TAIC composite nanofibers did not induce cytotoxic effects and are suitable for cell growth. Therefore, the crosslinked PLLA nanofibers are one of the promising materials for future tissue engineering applications.

Electrospun silk fibroin-hydroxybutyl chitosan nanofibrous scaffolds to biomimic extracellular matrix.

Silk fibroin (SF)-hydroxybutyl chitosan (HBC) blend nanofibrous scaffolds were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM by electrospinning. SEM results showed that the average nanofibrous diameter increased when the content of HBC was raised from 20% to 100%. Whereas water contact angle measurements confirmed that SF/HBC nanofibrous scaffolds with different weight ratios were of good hydrophilicity. Both the tensile strength and the elongation at break were improved obviously when the weight ratio of SF to HBC was 20:80. (13)C-NMR clarified that SF and HBC molecules existed in H-bond interactions, but HBC did not induce SF conformation to transform from random coil form to ß-sheet structure. Moreover, the use of genipin vapour not only induced conformation of SF to convert from random coil to ß-sheet structure but also acted as a cross-linking agent for SF and HBC. Cell viability studies demonstrated that SF/HBC nanofibrous scaffolds presented good cellular compatibility. Thus, electrospun SF/HBC blended nanofibres may provide an ideal biomimic tissue-engineering scaffold.

Fabrication of chitosan/silk fibroin composite nanofibers for wound-dressing applications.

Chitosan, a naturally occurring polysaccharide with abundant resources, has been extensively exploited for various biomedical applications, typically as wound dressings owing to its unique biocompatibility, good biodegradability and excellent antibacterial properties. In this work, composite nanofibrous membranes of chitosan (CS) and silk fibroin (SF) were successfully fabricated by electrospinning. The morphology of electrospun blend nanofibers was observed by scanning electron microscopy (SEM) and the fiber diameters decreased with the increasing percentage of chitosan. Further, the mechanical test illustrated that the addition of silk fibroin enhanced the mechanical properties of CS/SF nanofibers. The antibacterial activities against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) were evaluated by the turbidity measurement method; and results suggest that the antibacterial effect of composite nanofibers varied on the type of bacteria. Furthermore, the biocompatibility of murine fibroblast on as-prepared nanofibrous membranes was investigated by hematoxylin and eosin (H&E) staining and MTT assays in vitro, and the membranes were found to promote the cell attachment and proliferation. These results suggest that as-prepared chitosan/silk fibroin (CS/SF) composite nanofibrous membranes could be a promising candidate for wound healing applications.

Genipin-crosslinked silk fibroin/hydroxybutyl chitosan nanofibrous scaffolds for tissue-engineering application.

To improve water-resistant ability and mechanical properties of silk fibroin (SF)/hydroxybutyl chitosan (HBC) nanofibrous scaffolds for tissue-engineering applications, genipin, glutaraldehyde (GTA), and ethanol were used to crosslink electrospun nanofibers, respectively. The mechanical properties of nanofibrous scaffolds were obviously improved after 24 h of crosslinking with genipin and were superior to those crosslinked with GTA and ethanol for 24 h. SEM indicated that crosslinked nanofibers with genipin and GTA vapor had good water-resistant ability. Characterization of the microstructure (porosity and pore structure) demonstrated crosslinked nanofibrous scaffolds with genipin and GTA vapor had lager porosities and mean diameters than those with ethanol. Characterization of FTIR-ATR and (13)C NMR clarified both genipin and GTA acted as crosslinking agents for SF and HBC. Furthermore, genipin could induce SF conformation from random coil or α-helix to ß-sheet. Although GTA could also successfully crosslink SF/HBC nanofibrous scaffolds, in long run, genipin maybe a better method due to lower cytotoxicity than GTA. Cell viability studies and wound-healing test in rats clarified that the genipin-crosslinked SF/HBC nanofibrous scaffolds had a good biocompatibility both in vitro and in vivo. These results suggested that genipin-crosslinked SF/HBC nanofibrous scaffolds might be potential candidates for wound dressing and tissue-engineering scaffolds.