Menglin Chen

Chitosan/siRNA Nanoparticles Encapsulated in PLGA Nanofibers for siRNA Delivery

Composite nanofibers of biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) encapsulating chitosan/siRNA nanoparticles (NPs) were prepared by electrospinning. Acidic/alkaline hydrolysis and a bulk/surface degradation mechanism were investigated in order to achieve an optimized release profile for prolonged and efficient gene silencing. Thermo-controlled AFM in situ imaging not only revealed the integrity of the encapsulated chitosan/siRNA polyplex but also shed light on the decreasing T(g) of PLGA on the fiber surfaces during release. A triphasic release profile based on bulk erosion was obtained at pH 7.4, while a triphasic release profile involving both surface erosion and bulk erosion was obtained at pH 5.5. A short alkaline pretreatment provided a homogeneous hydrolysis and consequently a nearly zero-order release profile. The interesting release profile was further investigated for siRNA transfection, where the encapsulated chitosan/siRNA NPs exhibited up to 50% EGFP gene silencing activity after 48 h post-transfection on H1299 cells.

Light-Driven Wettability Changes on a Photoresponsive Electrospun Mat

Novel nanofibers of biodegradable polycaprolactone (PCL) modified with light-responsive azobenzene were prepared by electrospinning upon a facile one-pot reaction. The surface chemistry of the nanofibers was probed by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Both XPS and ToF-SIMS spectra proved the successful conjugation of azobenzene with PCL. ToF-SIMS not only enabled chemical mapping but also provided morphology information, supplementary to scanning electron microscopy (SEM). The large, reversible, and light-responsive wettability changes of the functional fibrous surfaces were further demonstrated using UV-vis spectroscopy and contact angle (CA) measurements.

Direct electrospinning of Ag/polyvinylpyrrolidone nanocables

Core-sheath silver nanowire/polyvinylpyrrolidone (AgNW/PVP) nanocables have been fabricated via an efficient single-spinneret electrospinning method. The core-sheath structure is revealed by combining several characterization methods. A possible formation mechanism of the AgNW/PVP nanocable involving a strong stretching during the electrospinning process is proposed. Further, electrical measurements were performed on AgNW/PVP nanocables as well as bare AgNWs, which indicated the nanocables became insulating due to the isolation of highly conductive AgNWs by insulating PVP sheath. Therefore, the described fabrication method holds potential for the fabrication of low-cost metal/polymer composite materials for nanoelectronic applications in general.

A high efficiency H2S gas sensor material: paper like Fe2O3/graphene nanosheets and structural alignment dependency of device efficiency

Fe2O3/graphene was synthesized successfully by a super critical CO2-assisted thermal method and further made into paper-like nanosheets by directed-flow, vertical assembly of individual Fe2O3/graphene nanosheets under a controlled magnetic field. Characterization of the samples was carried out by both electron microscopy and X-ray photoelectron spectroscopy. The sensor materials outperform many other paper-like materials for H2S gas detection. In addition, vertically and horizontally aligned nanosheets were used as sensing materials to detect H2S gas along with chemiluminescence measurements. Importantly, the nanoscale Fe2O3/graphene sheets with the vertical arrangement are more beneficial than the nanosheets with the horizontal arrangement in terms of sensitivity.

Electrospun Nanofibers‐Mediated On‐Demand Drug Release

A living system has a complex and accurate regulation system with intelligent sensor-processor-effector components to enable the release of vital bioactive substances on demand at a specific site and time. Stimuli-responsive polymers mimic biological systems in a crude way where an external stimulus results in a change in conformation, solubility, or alternation of the hydrophilic/hydrophobic balance, and consequently release of a bioactive substance. Electrospinning is a straightforward and robust method to produce nanofibers with the potential to incorporate drugs in a simple, rapid, and reproducible process. This feature article emphasizes an emerging area using an electrospinning technique to generate biomimetic nanofibers as drug delivery devices that are responsive to different stimuli, such as temperature, pH, light, and electric/magnetic field for controlled release of therapeutic substances. Although at its infancy, the mimicry of these stimuli-responsive nanofibers to the function of the living systems includes both the fibrous structural feature and bio-regulation function as an on demand drug release depot. The electrospun nanofibers with extracellular matrix morphology intrinsically guide cellular drug uptake, which will be highly desired to translate the promise of drug delivery for the clinical success.

Coaxial electrospun poly(lactic acid)/silk fibroin nanofibers incorporated with nerve growth factor support the differentiation of neuronal stem cells

Coaxial electrospinning is an explicit method for encapsulation of protein drugs, and the process could preserve the bioactivity of the molecules. In this study, coaxial electrospinning was used to fabricate Poly(Lactic Acid)/Silk Fibroin/Nerve Growth Factor (PS/N) by encapsulating nerve growth factor (NGF) along with Silk Fibroin (SF) as the core of the scaffold. Air plasma treatment was applied to PS/N scaffold to improve the surface hydrophilicity without causing any damage to the nanofibers. Surface characterization of the plasma treated PS/N scaffold (p-PS/N) was carried out by Atomic Force Microscopy, X-ray Photoelectron Spectroscopy and water contact angle test. PC12 cells cultured on both PS/N and p-PS/N scaffolds using Differentiation Medium devoid of NGF expressed neurofilament 200 protein on day 8, suggesting the differentiation potential of PC12 on both the scaffolds. By day 11, the cells cultured on p-PS/N scaffolds using the Differentiation Medium devoid of NGF showed elongated neurites with the length up to 95 μm. Our results suggested the sustained release of NGF, thus demonstrating the fact that the bioactivity of NGF was retained. The p-PS/N scaffolds were able to support the attachment and differentiation of PC12 cells, with ability to function as suitable substrates for nerve tissue engineering.

Enhanced Catalytic Activity of Lipase Encapsulated in PCL Nanofibers

Use of biocatalysis for industrial synthetic chemistry is on the verge of significant growth. Enzyme immobilization as an effective strategy for improving the enzyme activity has emerged from developments especially in nanoscience and nanotechnology. Here, lipase from Burkholderia cepacia (LBC), as an example of the luxuriant enzymes, was successfully encapsulated in polycaprolactone (PCL) nanofibers, proven by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Evaluated in both organic and aqueous medium, the activation factor of the encapsulated enzymes in the hydrolysis reaction was generally higher than that in the transesterification reaction. Enhanced catalytic activities were found when 5-20 w/w % of LBC was loaded. The effect of different solvents pretreatment on the activity of immobilized LBC was also investigated. The highest activation factor was found up to 14 for the sample containing acetone-treated LBC/PCL (10 w/w %). The encapsulated lipase reserved 50% of its original activity after the 10th run in the transesterification reaction in hexane medium. The mechanism of activation of lipase catalytic ability based on active PCL nanofiberous matrix is proposed.

Ag–CuFe2O4 magnetic hollow fibers for recyclable antibacterial materials

Copper ferrite (CuFe2O4) magnetic hollow fibers were prepared by applying an organic sol-thermal decomposition method, and silver nanoparticles were subsequently loaded on the fibers by calcination. The Ag-CuFe2O4 fibers exhibited excellent antibacterial efficacy against four different bacteria (E. coli, S. typhi, S. aureus and V. parahaemolyticus) with consistent results. Typical ferromagnetism behavior exhibited from the Ag-CuFe2O4 fibers enables their feasible recyclability.

Electrospun UV-responsive supramolecular nanofibers from a cyclodextrin–azobenzene inclusion complex

A combination of the unique hosting properties of cyclodextrins (CDs) and the peculiar UV-responsive trans–cis isomerization of the guest molecule azobenzene has endowed light-responsibility of the inclusion complex (IC). The IC of 4-aminoazobenzene (AAB) and hydroxypropyl-β-cyclodextrin (HPβCD), with its inherent viscosity from hydrogen bondings between CDs and π–π stacking between AABs, was electrospun into nanofibers from water without using any carrier polymer matrix. The integrity of electrospun ICs was proven by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), together with Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The homogeneous distribution of HPβCD–AAB-IC was confirmed by surface chemistry mapping using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The UV response of ICs prior to, during and post electrospinning was investigated. UV irradiation prior to electrospinning caused precipitation of AAB from the aqueous IC solution. UV irradiation during electrospinning flight demonstrated the interruption of ICs and consequently broader diameter distributions were obtained. Post-spinning UV irradiation induced topography and adhesion force changes on the electrospun nanofiber surfaces, demonstrated by in situ atomic force microspectroscopy (AFM) quantitative nanomechanical mapping. The present study is the first case where the supramolecule with stimuli response was electrospun into nanofibers with retained activity.

Electrospun PCL/PEO coaxial fibers for basic fibroblast growth factor delivery

The poor innate healing capacity of fibroblastic tissues, such as pelvic floor fascia, is attributed to the scarcity of fibroblasts to produce collagen, as the main collagen producing cells. Coaxial electrospun PCL/PEO fibers containing basic fibroblast growth factor (FGF-2) were evaluated for the local and temporal delivery of FGF-2 for promoting fibroblast proliferation. PCL/PEO coaxial fibers with a highly porous surface were successfully developed using coaxial electrospinning. The diameter of the PCL/PEO microfibers produced by coaxial electrospinning could be tuned by the electrospinning parameters. XPS surface chemistry probing and CA wettability analysis confirmed that the outer surface of the coaxial fibers is PCL. The protein was successfully encapsulated and a sustained release was observed over more than 9 days. In vitro, PCL/PEO coaxial fibers supported fibroblast cell adhesion. In addition, PCL/PEO coaxial fibers containing FGF-2 significantly enhanced fibroblast cell viability and proliferation. Further, Coll-I expression was significantly expressed after day 1 while down-regulated after day 9 compared to the control group. These results indicate that coaxial polymeric fibers allow local and sustained growth factor delivery with prolonged efficacy and longevity for connective tissue regeneration.