Controllable drug release of electrospun thermoresponsive poly(N-isopropylacrylamide)/poly(2-acrylamido-2- methylpropanesulfonic acid) nanofibers

Adipose-Derived Stem Cells Based on Electrospun Biomimetic Scaffold Mediated Endothelial Differentiation Facilitating Regeneration and Repair of Abdominal Wall Defects via HIF-1α/VEGF Pathway

Application of synthetic or biological meshes is the main therapy for the repair and reconstruction of abdominal wall defects, a common disease in surgery. Currently, no ideal materials are available, and there is an urgent need to find appropriate ones to satisfy clinical needs. Electrospun scaffolds have drawn attention in soft tissue reconstruction. In this study, we developed a novel method to fabricate a composite electrospun scaffold using a thermoresponsive hydrogel, poly (N-isopropylacrylamide)-block-poly (ethylene glycol), and a biodegradable polymer, polylactic acid (PLA). This scaffold provided not only a high surface area/volume ratio and a three-dimensional fibrous matrix but also high biocompatibility and sufficient mechanical strength, and could simulate the native extracellular matrix and accelerate cell adhesion and proliferation. Furthermore, rat adipose-derived stem cells (ADSCs) were seeded in the composite electrospun scaffold to enhance the defect repair and regeneration by directionally inducing ADSCs into endothelial cells. In addition, we found early vascularization in the process was regulated by the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathway. In our study, overexpression of HIF-1α/VEGF in ADSCs using a lentivirus system promoted early vascularization in the electrospun scaffolds. Overall, we expect our composite biomimetic scaffold method will be applicable and useful in abdominal wall defect regeneration and repair in the future.

Bioresponsive Hybrid Nanofibers Enable Controlled Drug Delivery through Glass Transition Switching at Physiological Temperature

To avoid excessive usage of antibiotics and antimicrobial agents, smart wound dressings permitting controlled drug release for treatment of bacterial infections are highly desired. In search of a sensitive stimulus to activate drug release under physiological conditions, we found that the glass transition temperature (T_g) of a polymer or polymer blend can be an ideal parameter because a thermal stimulus can regulate drug release at the physiological temperature of 37 °C. A well-tuned T_g for a controlled drug release from fibers at 37 °C was achieved by varying the blending ratio of Eudragit® RS 100 and poly(methyl methacrylate). Octenidine, an antimicrobial agent often used in wound treatment, was encapsulated into the polymer blend during the electrospinning process and evaluated for its controlled release based on modulation of temperature. The thermal switch of the nanofibrous membranes can be turned "on" at physiological temperature (37 °C) and "off" at room temperature (25 °C), conferring a controlled release of octenidine. It was found that octenidine can be released in an amount at least 8.5 times higher (25 mg·L^-1) during the "on" stage compared to the "off" stage after 24 h, which was regulated by the wet T_g (34.8-36.5 °C). The "on"/"off" switch for controlled drug release can moreover be repeated at least 5 times. Furthermore, the fabricated nanofibrous membranes displayed a distinctive antibacterial activity, causing a log3 reduction of the viable cells for both Gram negative and positive pathogens at 37 °C, when the thermal switch was "on". This study forms the groundwork for a treatment concept where no external stimulus is needed for the release of antimicrobials at physiological conditions, and will help reduce the overuse of antibiotics by allowing controlled drug release.

The Effect of Molecular Properties on Active Ingredient Release from Electrospun Eudragit Fibers

The formation of nanoscale fibers from pH-sensitive polymers is a route which has been widely explored for targeted drug delivery. In particular, the Eudragit L100 and S100 families of polymers have received significant attention for this purpose. However, while in some cases it is shown that making drug-loaded Eudragit polymers effectively prevents drug release in low-pH media where the polymer is insoluble, this is not always the case, and other studies have reported significant amounts of drug release at acidic pHs. In this study, we sought to gain insight into the factors influencing the release of active ingredients from Eudragit S100 (ES100) fibers. A family of materials was prepared loaded with the model active ingredients (AIs) benzoic acid, 1-naphthoic acid, 1-naphthylamine, and 9-anthracene carboxylic acid. Analogous systems were prepared with an AI-loaded core and an ES100 sheath. The resultant fibers were smooth and cylindrical in the majority of cases, and X-ray diffraction and differential scanning calorimetry showed them to comprise amorphous solid dispersions. When AI release from the monolithic fibers was probed, it was found that there was significant release at pH 1 in all cases except with 9-anthracene carboxylic acid. Analysis of the results indicated that both the molecular weight of the AI and its acidity/basicity are important in controlling release, with lower molecular weight AIs and basic species released more quickly. The same release trends are seen with the core/shell fibers, but AI release at pH 1 is attenuated. The most significant change between the monolithic and core/shell systems was observed in the case of 1-naphthylamine. Mathematical equations were devised to connect molecular properties and AI release under acidic conditions.

Electrohydrodynamic methods for the development of pulmonary drug delivery systems

Electrospinning and electrospraying are two highly versatile and scalable electrohydrodynamic methods, which have attracted considerable attention during the last years towards the fabrication of polymer-based drug delivery systems. The latter may be obtained in the form of nano- or microfibers (via electrospinning) or as drug-loaded nano- and microparticles (via electrospraying). This review article begins with an introduction on the basic principles and the important influencing parameters governing the electrospinning/electrospraying processes, followed by an overview on their use for the development of nano/microfibers and nano/microparticles destined for use in pharmaceutical applications. Focus is given on research efforts targeting in the formulation of drug delivery systems and devices designed for pulmonary drug delivery applications thus emphasizing on the potential use of electrospinning and electrospraying in the area of inhaled medicines.

A thermosensitive drug delivery system prepared by blend electrospinning

In this study, the thermosensitive polymer poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) was synthesized and electrospun into fibers by blending with ethyl cellulose (EC). Fibers were additionally prepared loaded with ketoprofen (KET) as a model drug. Smooth cylindrical fibers could generally be observed by electron microscopy, although there were some beads and fused fibers visible in the KET-loaded materials. KET was found to be amorphously distributed in the fibers on the basis of X-ray diffraction data. From water contact angle measurements, it was clear that the wettability of the EC/PDEGMA systems changed as the temperature increased, with the fibers becoming markedly more hydrophobic. In vitro drug release studies showed that KET was released over a prolonged period of time with the fibers having different profiles at 25 and 37°C, reflecting their thermosensitive properties. Furthermore, the materials were found to have good biocompatibility towards L929 fibroblasts. Thus, the fibers prepared in this work have potential as smart stimuli-responsive drug delivery systems.

Bicomponent electrospun scaffolds to design extracellular matrix tissue analogs

In the last decade, bicomponent fibers have been proposed to fabricate bio-inspired systems for tissue repair, regenerative medicine, medical healthcare and clinical applications. In comparison with monocomponent fibers, key advantage concerns their ability of self-adapting to the physiological conditions through an extended pattern of signals--morphological, chemical and physical ones--confined at the single fiber level. Hydrophobic/hydrophilic phases may be variously organized by tuneable processing modes (i.e., blending, core/shell, interweaving) thus offering different benefits in terms of biological activity, fluid sorption and molecular transport properties (first generation). The possibility to efficiently graft cell-adhesive proteins and peptide sequences onto the fiber surface mediated by spacers or impregnating hydrogels allows to trigger cell late activities by a controlled and sustained release in vitro of specific biomolecules (i.e., morphogens, growth factors). Here, we introduce an overview of current approaches based on bicomponent fiber use as extra cellular matrix analogs with cell-instructive functions and hierarchal organization of living tissues.

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.

Nanofiber for cardiovascular tissue engineering

INTRODUCTION

Organ/tissue replacement therapy is inherently difficult for application in the tissue engineering field due to immune rejection that limits the long-term efficacy of implanted devices. As the application of tissue engineering in the biomedical field has steadily expanded, stem cells have emerged as a viable option to promote the immune acceptance of implantable devices and to expedite alleviation of the pathological conditions. With various novel scaffolds being introduced, nanofibers which have a three-dimensional architecture can be considered as an efficient carrier for stem cells.

AREAS COVERED

This article reviews the novel tissue engineering processes involved with nanofiber and stem cells. Topics such as the fabrication of nanofiber via electrospinning techniques, the interaction between nanofiber scaffold and specific cell and advanced techniques to enhance the stability of stem cells are delineated in detail. In addition, cardiovascular applications of nanofiber scaffolds loaded with stem cells are examined from a clinical perspective.

EXPERT OPINION

Electrospun nanofibers have been intensively explored as a tool for the architecture control of cardiovascular tissue engineering due to their tunable physicochemical properties. The modification of nanofiber with biological cues, which provide rapid differentiation of stem cells into a specific lineage and protect stem cells under the harsh conditions (i.e., hypoxia), will significantly enhance therapeutic efficacies of transplanted cells. A combination of nanofiber carriers and stem cell therapy for tissue regeneration seems to pose enormous potential for the treatment of cardiac diseases including atherosclerosis and myocardial infarction.

Self-assembly and controlled release behaviour of the water-insoluble drug nifedipine from electrospun PCL-based polyurethane nanofibres

OBJECTIVES

Electrospun micro- and nanofibres are increasingly being investigated for drug delivery. The components of nanofibres are important influences on the drug release behaviour. The aim of this study was to investigate the self-assembly and release behaviour of drug from nanofibres.

METHODS

Water-insoluble drug nifedipine (NIF)-loaded nanofibres with polymeric carrier of polycaprolactone (PCL)-based polyurethane (PU) were fabricated by electrospinning. The morphology of the nanofibres and the composite nanofibres with NIF were examined by scanning electron microscopy (SEM). The interactions between NIF and PU were followed by Fourier-transform infrared spectroscopy, and the elemental composition on the surface of the nanofibres was characterized by X-ray photoelectron spectroscopy. The release behaviour of NIF from nanofibres was observed by SEM (contacted with or without a drop of ethanol), and demonstrated by UV-Vis spectroscopy.

KEY FINDINGS

In-vitro drug release studies revealed that a self-assembly process of NIF particles might be achieved within the body of the nanofibres. The electrospun nanofibre was an ideal drug carrier compared with a spin-coated film and could achieve controlled release of drug.

CONCLUSIONS

The electrospinning technique could be used to fabricate a polymeric carrier that might have potential applications in the biomedical field.