Preparation of fiber-microsphere scaffolds for loading bioactive substances in gradient amounts

Potent Particle-Based Vehicles for Growth Factor Delivery from Electrospun Meshes: Fabrication and Functionalization Strategies for Effective Tissue Regeneration

Functionalization of electrospun meshes with growth factors (GFs) is a common strategy for guiding specific cell responses in tissue engineering. GFs can exert their intended biological effects only when they retain their bioactivity and can be subsequently delivered in a temporally controlled manner. However, adverse processing conditions encountered in electrospinning can potentially disrupt GFs and diminish their biological efficacy. Further, meshes prepared using conventional approaches often promote an initial burst and rely solely on intrinsic fiber properties to provide extended release. Sequential delivery of multiple GFs─a strategy that mimics the natural tissue repair cascade─is also not easily achievable with traditional fabrication techniques. These limitations have hindered the effective use and translation of mesh-based strategies for tissue repair. An attractive alternative is the use of carrier vehicles (e.g., nanoparticles, microspheres) for GF incorporation into meshes. This review presents advances in the development of particle-integrated electrospun composites for safe and effective delivery of GFs. Compared to traditional approaches, we reveal how particles can protect GF activity, permit the incorporation of multiple GFs, decouple release from fiber properties, help achieve spatiotemporal control over delivery, enhance surface bioactivity, exert independent biological effects, and augment matrix mechanics. In presenting innovations in GF functionalization and composite engineering strategies, we also discuss specific in vitro and in vivo biological effects and their implications for diverse tissue engineering applications.

Electrohydrodynamic atomization: A two-decade effort to produce and process micro-/nanoparticulate materials

Electrohydrodynamic atomization (EHDA), also called electrospray technique, has been studied for more than one century. However, since 1990s it has begun to be used to produce and process micro-/nanostructured materials. Owing to the simplicity and flexibility in EHDA experimental setup, it has been successfully employed to generate particulate materials with controllable compositions, structures, sizes, morphologies, and shapes. EHDA has also been used to deposit micro- and nanoparticulate materials on surfaces in a well-controlled manner. All these attributes make EHDA a fascinating tool for preparing and assembling a wide range of micro- and nanostructured materials which have been exploited for use in pharmaceutics, food, and healthcare to name a few. Our goal is to review this field, which allows scientists and engineers to learn about the EHDA technique and how it might be used to create, process, and assemble micro-/nanoparticulate materials with unique and intriguing properties. We begin with a brief introduction to the mechanism and setup of EHDA technique. We then discuss issues critical to successful application of EHDA technique, including control of composition, size, shape, morphology, structure of particulate materials and their assembly. We also illustrate a few of the many potential applications of particulate materials, especially in the area of drug delivery and regenerative medicine. Next, we review the simulation and modeling of Taylor cone-jet formation for a single and co-axial nozzle. The mathematical modeling of particle transport and deposition is presented to provide a deeper understanding of the effective parameters in the preparation, collection and pattering processes. We conclude this article with a discussion on perspectives and future possibilities in this field.

Fibre–Microsphere Membranes with Continuous BMP-2 Gradients with Potential Applications in Interface-tissue Engineering

Functional gradient scaffolds play an important role in interface-tissue engineering, because of the gradual transition of both physical and chemical properties in interface tissues such as bone–cartilage, bone–ligament, and bone–tendon. In this study, a poly(l-lactide-co-glycolide) fibre–microsphere membrane with continuous-gradient bone morphogenic protein-2 (BMP-2) distribution was developed by a combined technique of electrospinning and electrospraying. The fibre–microsphere membrane had a ‘sandwich’ structure, in which the electrosprayed poly(l-lactide-co-glycolide) microspheres loaded with BMP-2 showed a gradient distribution in amount between two pieces of electrospun fibrous membranes. Proliferation of preosteoblast MC3T3-E1 cells cultured on the fibre–microsphere membrane for 21 days demonstrated a bioactivity response to the released amount of BMP-2 in a gradient mode. The study suggested that the technique of electrospinning combined with electrospraying is an effective way to prepare functional gradient membranes with potential applications in bone–interface tissue regeneration.