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.

Hollow Au/Polypyrrole Capsules to Form Porous and Neural Network-Like Nanofibrous Film for Wearable, Super-Rapid, and Ultrasensitive NH3 Sensor at Room Temperature.

Wearable conducting polymer-based NH3 sensors are highly desirable in real-time environmental monitoring and human health protection but still a challenge for their relatively long response/recovery time and moderate sensitivity at room temperature. Herein, we present an effective route to fulfill this challenge by constructing porous and neural network-like Au/polypyrrole (Au/PPy) electrospun nanofibrous film with hollow capsular units for NH3 sensor. Taking the unique architecture and synergistic effect between Au and PPy, our sensor exhibits not only super-rapid response/recovery time (both ∼7 s), faster than all reported sensors, but also stable and ultrahigh sensitivity (response reaches ∼2.3 for 1 ppm NH3) at room temperature even during repeated deformation. Furthermore, good selectivity has been also achieved. These outstanding properties make our sensor hold great potential in real-time NH3-related disease diagnosis and environmental monitoring at room temperature.

Natural Melanin/Polyurethane Composites as Highly Efficient Near-Infrared-Photoresponsive Shape Memory Implants.

Natural melanin is recognized as a biocompatible photothermal agent because of its biologically derived nature and efficient photothermal conversion ability. Here, yak hair melanin (YM) is added to polyurethane (PU) for the fabrication of NIR-photoresponsive shape memory implants. The in vitro toxicity of the YM/PU composites is carried out by exposing them to human mesenchymal stem cells (hMSCs) and mouse fibroblast (L929) cells lines for 24 h, while the in vivo toxicity is investigated by implanting the YM/PU composites in the mouse for two months. No significant differences on cell viability, blood chemistry, hematology, and histological results are observed between YM/PU composites and control groups, suggesting their excellent biocompatibility. The biostability of the YM/PU composites is confirmed by monitoring their in vitro degradation for 12 weeks. The YM/PU column implanted in the back subcutis or vagina of the mouse rapidly recovered to its original state within 60 s under a very low NIR laser (808 nm, 0.5 W/cm2) intensity, which is much lower than the general laser intensity for photothermal cancer therapy (1-2 W/cm2). This work confirms the applicability of the YM/PU composites as long-term implant materials and expedites the use of YM/PU composites as cost-effective candidates for biomedical applications.

Fluorine-Free Superhydrophobic Coatings with pH-induced Wettability Transition for Controllable Oil-Water Separation.

We present a simple, environmentally friendly approach to fabricating superhydrophobic coatings with pH-induced wettability transition. The coatings are prepared from a mixture of silica nanoparticles and decanoic acid-modified TiO2. When the coating is applied on cotton fabric, the fabric turns superhydrophobic in air but superoleophilic in neutral aqueous environment. It is permeable to oil fluids but impermeable to water. However, when the coated fabric is placed in basic aqueous solution or ammonia vapor, it turns hydrophilic but underwater superoleophobic, thus allowing water to penetrate through but blocking oil. Therefore, such a unique, selective water/oil permeation feature makes the treated fabric have capability to separate either oil or water from a water-oil mixture. It may be useful for development of smart oil-water separators, microfluidic valves, and lab-on-a-chip devices.

Biodegradable Eri silk nanoparticles as a delivery vehicle for bovine lactoferrin against MDA-MB-231 and MCF-7 breast cancer cells.

This study used the Eri silk nanoparticles (NPs) for delivering apo-bovine lactoferrin (Apo-bLf) (~2% iron saturated) and Fe-bLf (100% iron saturated) in MDA-MB-231 and MCF-7 breast cancer cell lines. Apo-bLf and Fe-bLf-loaded Eri silk NPs with sizes between 200 and 300 nm (±10 nm) showed a significant internalization within 4 hours in MDA-MB-231 cells when compared to MCF-7 cells. The ex vivo loop assay with chitosan-coated Fe-bLf-loaded silk NPs was able to substantiate its future use in oral administration and showed the maximum absorption within 24 hours by ileum. Both Apo-bLf and Fe-bLf induced increase in expression of low-density lipoprotein receptor-related protein 1 and lactoferrin receptor in epidermal growth factor (EGFR)-positive MDA-MB-231 cells, while transferrin receptor (TfR) and TfR2 in MCF-7 cells facilitated the receptor-mediated endocytosis of NPs. Controlled and sustained release of both bLf from silk NPs was shown to induce more cancer-specific cytotoxicity in MDA-MB-231 and MCF-7 cells compared to normal MCF-10A cells. Due to higher degree of internalization, the extent of cytotoxicity and apoptosis was significantly higher in MDA-MB-231 (EGFR+) cells when compared to MCF-7 (EGFR-) cells. The expression of a prominent anticancer target, survivin, was found to be downregulated at both gene and protein levels. Taken together, all the observations suggest the potential use of Eri silk NPs as a delivery vehicle for an anti-cancer milk protein, and indicate bLf for the treatment of breast cancer.

A new design concept for knitted external vein-graft support mesh.

Autologous vein-graft failure significantly limits the long-term efficacy of coronary artery bypass procedures. The major cause behind this complication is biomechanical mismatch between the vein and coronary artery. The implanted vein experiences a sudden increase (10-12 fold) in luminal pressures. The resulting vein over-distension or 'ballooning' initiates wall thickening phenomenon and ultimate occlusion. Therefore, a primary goal in improving the longevity of a coronary bypass procedure is to inhibit vein over-distension using mechanical constriction. The idea of using an external vein-graft support mesh has demonstrated sustained benefits and wide acceptance in experimental studies. Nitinol based knitted structures have offered more promising mechanical features than other mesh designs owing to their unique loosely looped construction. However, the conventional plain knit construction still exhibits limitations (radial compliance, deployment ease, flexibility, and bending stresses) which limit this design from proving its real clinical advantage. The new knitted mesh design presented in this study is based on the concept of composite knitting utilising high modulus (nitinol and polyester) and low modulus (polyurethane) material components. The experimental comparison of the new design with a plain knit design demonstrated significant improvement in biomechanical (compliance, flexibility, extensibility, viscoelasticity) and procedural (deployment limit) parameters. The results are indicative of the promising role of new mesh in restoring the lost compliance and pulsatility of vein-graft at high arterial pressures. This way it can assist in controlled vein-graft remodelling and stepwise restoration of vein mechanical homoeostasis. Also, improvement in deployment limit parameter offers more flexibility for a surgeon to use a wide range of vein diameters, which may otherwise be rendered unusable for a plain knit mesh.

A superamphiphobic coating with an ammonia-triggered transition to superhydrophilic and superoleophobic for oil-water separation.

Superhydrophilic and superoleophobic materials are very attractive for efficient and cost-effective oil-water separation, but also very challenging to prepare. Reported herein is a new superamphiphobic coating that turns superhydrophilic and superoleophobic upon ammonia exposure. The coating is prepared from a mixture of silica nanoparticles and heptadecafluorononanoic acid-modified TiO2 sol by a facile dip-coating method. Commonly used materials, including polyester fabric and polyurethane sponge, modified with this coating show unusual capabilities for controllable filtration of an oil-water mixture and selective removal of water from bulk oil. We anticipate that this novel coating may lead to the development of advanced oil-water separation techniques.

Fabrication of boron nitride nanotube-gold nanoparticle hybrids using pulsed plasma in liquid.

Plasma, generated in liquid at atmospheric pressure by a nanosecond pulsed voltage, was used to fabricate hybrid structures from boron nitride nanotubes and gold nanoparticles in deionized water. The pH was greatly reduced, conductivity was significantly increased, and concentrations of reactive oxygen and nitrogen species in the water were increased by the plasma treatment. The treatment reduced the length of the nanotubes, giving more individual cuplike structures, and introduced functional groups onto the surface. Gold nanoparticles were successively assembled onto the functionalized surfaces. The reactive species from the liquid plasma along with the nanosecond pulsed electric field seem to play a role in the shortening and functionalization of the nanotubes and the assembly of gold nanoparticles. The potential for targeted drug delivery was tested in a preliminary investigation using doxorubicin-loaded plasma-treated nanotubes which were effective at killing ∼99% of prostate cancer cells.

Graphene oxide nanoparticles for enhanced photothermal cancer cell therapy under the irradiation of a femtosecond laser beam.

Nano-sized graphene and graphene oxide (GO) are promising for biomedical applications, such as drug delivery and photothermal therapy of cancer. It is observed in this work that the ultrafast reduction of GO nanoparticles (GONs) with a femtosecond laser beam creates extensive microbubbling. To understand the surface chemistry of GONs on the microbubble formation, the GONs were reduced to remove most of the oxygen-containing groups to get reduced GONs (rGONs). Microbubbling was not observed when the rGONs were irradiated by the laser. The instant collapse of the microbubbles may produce microcavitation effect that brings about localized mechanical damage. To understand the potential applications of this phenomenon, cancer cells labeled with GONs or rGONs were irradiated with the laser. Interestingly, the microbubbling effect greatly facilitated the destruction of cancer cells. When microbubbles were produced, the effective laser power was reduced to less than half of what is needed when microbubbling is absent. This finding will contribute to the safe application of femtosecond laser in the medical area by taking advantage of the ultrafast reduction of GONs. It may also find other important applications that need highly localized microcavitation effects.

A review of optical imaging and therapy using nanosized graphene and graphene oxide.

Nanosized graphene and graphene oxide (GO) are photoluminescent due to the presence of bandgaps and edges/defects. The excellent photostability of these nanomaterials makes them superior to molecular dyes for biological imaging. They can also produce intensive heat under laser irradiation, enabling them to serve as photothermal agents for cancer treatment. In this work, recent studies on the photoluminescence of these materials, their applications for biological imaging and photothermal cancer therapy are reviewed. Properties of laser, particularly the temporal property (continuous wave or pulsed), affect its interaction with materials. Therefore, the photoluminescence and photothermal effects, as well as their applications under both single (one)-photon (continuous wave laser) and two-photon (pulsed laser) excitation were summarized and analyzed. Synergistic therapy which combines chemotherapy and photothermal therapy using these materials is also reviewed. Finally, critical issues and challenges for further research and in medical applications of these materials are analyzed.

Apatite-coated three-dimensional fibrous scaffolds and their osteoblast response.

Apatite was applied onto the fiber surface of an interbonded three-dimensional polycaprolactone fibrous scaffold through a vacuum nitrogen plasma pretreatment followed by immersion in a simulated body fluid. The plasma pretreatment improved the wettability and accelerated apatite deposition on the fiber surface. The apatite coating was proven to be biocompatible to fibroblast cells without any cytotoxicity. Two osteoblast cell lines, human fetal osteoblast cells (hFOB1.19) and human osteosarcoma cells (Saos-2), were used for evaluating the cell response of the fibrous matrices. The apatite coating showed enhanced cell attachment for both hFOB1.19 and Saos-2 cells. In comparison to the uncoated fibrous scaffolds, the apatite-coated fibrous matrix had an improved hFOB1.19 cell proliferation for at least 2 weeks. Enhanced cell differentiation was also observed on the apatite-coated fibrous matrix primarily on the third, 10th, and 14th days of culture. Saos-2 cells showed improved proliferation in the apatite-coated matrix mainly on days 3 and 14, but the differentiation was increased only on the third day of culture.

Biofunctionalization of 3D nylon 6,6 scaffolds using a two-step surface modification.

Nylon is a relatively inert polymer. The ability to easily functionalize nylon with biomolecules will improve the utilization of nylon in biological systems. A potential use of the biofunctionalized nylon scaffolds is in devices for cell therapeutics that can specifically select cells present in small numbers, such as hematopoietic stem cells. This study developed a versatile and simple two-step technique combining oxygen plasma treatment with wet silanization to graft biomolecules onto nylon 6,6 3D porous scaffolds. Scaffolds that were exposed to oxygen plasma exhibited up to 13-fold increase in silane attachment ((3-mercaptopropyl)trimethoxysilane/(3-aminopropyl)trimethoxysilane) compared to untreated scaffolds. To address the limitation of nondestructive characterization of the surface chemistry of 3D scaffolds, fluorescent CdSe/ZnS nanoparticles were used as a reporting tool for -NH2 functionalized surfaces. Scaffolds that were covalently bound with neutravidin protein remained stable in phosphate buffered saline up to four months. Functionality of the neutravidin-grafted scaffolds was demonstrated by the specific binding of CD4 cells to the scaffold via CD4-specific antibody. Ultimately, these neutravidin-functionalized 3D nylon scaffolds could be easily customized on demand utilizing a plethora of biotinylated biomolecules (antibodies, enzymes and proteins) to select for specific cell of interest. This technique can be extended to other applications, including the enhancement of cell-scaffold interactions.

Ingrowth of human mesenchymal stem cells into porous silk particle reinforced silk composite scaffolds: An in vitro study.

Silk fibroin protein is biodegradable and biocompatible, exhibiting excellent mechanical properties for various biomedical applications. However, porous three-dimensional (3-D) silk fibroin scaffolds, or silk sponges, usually fall short in matching the initial mechanical requirements for bone tissue engineering. In the present study, silk sponge matrices were reinforced with silk microparticles to generate protein-protein composite scaffolds with desirable mechanical properties for in vitro osteogenic tissue formation. It was found that increasing the silk microparticle loading led to a substantial increase in the scaffold compressive modulus from 0.3 MPa (non-reinforced) to 1.9 MPa for 1:2 (matrix:particle) reinforcement loading by dry mass. Biochemical, gene expression, and histological assays were employed to study the possible effects of increasing composite scaffold stiffness, due to microparticle reinforcement, on in vitro osteogenic differentiation of human mesenchymal stem cells (hMSCs). Increasing silk microparticle loading increased the osteogenic capability of hMSCs in the presence of bone morphogenic protein-2 (BMP-2) and other osteogenic factors in static culture for up to 6 weeks. The calcium adsorption increased dramatically with increasing loading, as observed from biochemical assays, histological staining, and microcomputer tomography (µCT) analysis. Specifically, calcium content in the scaffolds increased by 0.57, 0.71, and 1.27 mg (per µg of DNA) from 3 to 6 weeks for matrix to particle dry mass loading ratios of 1:0, 1:1, and 1:2, respectively. In addition, µCT imaging revealed that at 6 weeks, bone volume fraction increased from 0.78% for non-reinforced to 7.1% and 6.7% for 1:1 and 1:2 loading, respectively. Our results support the hypothesis that scaffold stiffness may strongly influence the 3-D in vitro differentiation capabilities of hMSCs, providing a means to improve osteogenic outcomes.