Controlled Morphing of Microbubbles to Beaded Nanofibers via Electrically Forced Thin Film Stretching

Integrating Chinese Herbs and Western Medicine for New Wound Dressings through Handheld Electrospinning

In this nanotechnology era, nanostructures play a crucial role in the investigation of novel functional nanomaterials. Complex nanostructures and their corresponding fabrication techniques provide powerful tools for the development of high-performance functional materials. In this study, advanced micro-nanomanufacturing technologies and composite micro-nanostructures were applied to the development of a new type of pharmaceutical formulation, aiming to achieve rapid hemostasis, pain relief, and antimicrobial properties. Briefly, an approach combining a electrohydrodynamic atomization (EHDA) technique and reversed-phase solvent was employed to fabricate a novel beaded nanofiber structure (BNS), consisting of micrometer-sized particles distributed on a nanoscale fiber matrix. Firstly, Zein-loaded Yunnan Baiyao (YB) particles were prepared using the solution electrospraying process. Subsequently, these particles were suspended in a co-solvent solution containing ciprofloxacin (CIP) and hydrophilic polymer polyvinylpyrrolidone (PVP) and electrospun into hybrid structural microfibers using a handheld electrospinning device, forming the EHDA product E3. The fiber-beaded composite morphology of E3 was confirmed through scanning electron microscopy (SEM) images. Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis revealed the amorphous state of CIP in the BNS membrane due to the good compatibility between CIP and PVP. The rapid dissolution experiment revealed that E3 exhibits fast disintegration properties and promotes the dissolution of CIP. Moreover, in vitro drug release study demonstrated the complete release of CIP within 1 min. Antibacterial assays showed a significant reduction in the number of adhered bacteria on the BNS, indicating excellent antibacterial performance. Compared with the traditional YB powders consisting of Chinese herbs, the BNS showed a series of advantages for potential wound dressing. These advantages include an improved antibacterial effect, a sustained release of active ingredients from YB, and a convenient wound covering application, which were resulted from the integration of Chinese herbs and Western medicine. This study provides valuable insights for the development of novel multiscale functional micro-/nano-composite materials and pioneers the developments of new types of medicines from the combination of herbal medicines and Western medicines.

Dual-Step Controlled Release of Berberine Hydrochloride from the Trans-Scale Hybrids of Nanofibers and Microparticles

In this nano era, nanomaterials and nanostructures are popular in developing novel functional materials. However, the combinations of materials at micro and macro scales can open new routes for developing novel trans-scale products with improved or even new functional performances. In this work, a brand-new hybrid, containing both nanofibers and microparticles, was fabricated using a sequential electrohydrodynamic atomization (EHDA) process. Firstly, the microparticles loaded with drug (berberine hydrochloride, BH) molecules in the cellulose acetate (CA) were fabricated using a solution electrospraying process. Later, these microparticles were suspended into a co-dissolved solution that contained BH and a hydrophilic polymer (polypyrrolidone, PVP) and were co-electrospun into the nanofiber/microparticle hybrids. The EHDA processes were recorded, and the resultant trans-scale products showed a typical hybrid topography, with microparticles distributed all over the nanofibers, which was demonstrated by SEM assessments. FTIR and XRD demonstrated that the components within the hybrids were presented in an amorphous state and had fine compatibility with each other. In vitro dissolution tests verified that the hybrids were able to provide the designed dual-step drug release profiles, a combination of the fast release step of BH from the hydrophilic PVP nanofibers through an erosion mechanism and the sustained release step of BH from the insoluble CA microparticles via a typical Fickian diffusion mechanism. The present protocols pave a new way for developing trans-scale functional materials.

The Effect of the PVA/Chitosan/Citric Acid Ratio on the Hydrophilicity of Electrospun Nanofiber Meshes

In this study, scaffolds were prepared via an electrospinning method for application in oral cavities. The hydrophilicity of the fiber mesh is of paramount importance, as it promotes cell spreading; however, the most commonly used polyvinyl alcohol (PVA) and other hydrophilic fiber meshes immediately disintegrate in aqueous media. In contrast, the excessive hydrophobicity of the scaffolds already inhibits cells adhesion on the surface. Therefore, the hydrophilicity of the fiber meshes needed to be optimized. Scaffolds with different polyvinyl alcohol (PVA)/chitosan/citric acid ratios were prepared. The addition of chitosan and the heat initiated cross-linkage of the polymers via citric acid enhanced the scaffolds' hydrophobicity. The optimization of this property could be followed by contact angle measurements, and the increased number of cross-linkages were also supported by IR spectroscopy results. The fibers' physical parameters were monitored via low-vacuum scanning electron microscopy (SEM) and atomic force microscopy (AFM). As biocompatibility is essential for dental applications, Alamar Blue assay was used to prove that meshes do not have any negative effects on dental pulp stem cells. Our results showed that the optimization of the fiber nets was successful, as they will not disintegrate in intraoral cavities during dental applications.

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

T-Shaped Microfluidic Junction Processing of Porous Alginate-Based Films and Their Characteristics

In this work, highly monodisperse porous alginate films from bubble bursting were formed on a glass substrate at ambient temperature, by a T-shaped microfluidic junction device method using polyethylene glycol (PEG) stearate and phospholipid as precursors in some cases. Various polymer solution concentrations and feeding liquid flow rates were applied for the generation of monodisperse microbubbles, followed by the conversion of the bubbles to porous film structures on glass substrates. In order to compare the physical properties of polymeric solutions, the effects of alginate, PEG stearate (surfactant), and phospholipid concentrations on the flowability of the liquid in a T-shaped microfluidic junction device were studied. To tailor microbubble diameter and size distribution, a method for controlling the thinning process of the bubbles' shell was also explored. In order to control pore size, shape, and surface as well as internal structure morphologies in the scalable forming of alginate polymeric films, the effect of the feeding liquid's flow rate and concentrations of PEG-stearate and phospholipid was also studied. Digital microscopy images revealed that the as-formed alginate films at the flow rate of 100 µL·min-1 and the N2 gas pressure of 0.8 bar have highly monodisperse microbubbles with a polydispersity index (PDI) of approximately 6.5%. SEM captures also revealed that the as-formed alginate films with high PDI value have similar monodisperse porous surface and internal structure morphologies, with the exception that the as-formed alginate films with the help of phospholipids were mainly formed under our experimental environment. From the Fourier-transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements, we concluded that no chemical composition changes, thermal influence, and crystal structural modifications were observed due to the T-shaped microfluidic junction device technique. The method used in this work could expand and enhance the use of alginate porous films in a wide range of bioengineering applications, especially in tissue engineering and drug delivery, such as studying release behaviors to different internal and surface morphologies.

Solid drug particles encapsulated bead-on-string nanofibers: the control of bead number and its corresponding release profile

Bead-on-string nanofibers are explored as potential carriers of micro-level solid drug particles in recent years in drug release and tissue engineering. The special alternating distribution of nanoscale fiber and micro beads satisfied the fully encapsulation of particle drugs and the corresponding sustained release. Antibiotic drug tetracycline hydrochloride (TCH) was used as solid model drug particles. The present study fabricated poly (lactic-co-glycolic acid) (PLG A) bead-on-string nanofibers with different TCH loading rates for the controlled drug delivery. Bead number (BN), as one of the crucial factors that determine the encapsulation capability, was successfully controlled by tailoring the electrospinning parameters: voltage, flow rate and distance. The in vitro release experiment analyze by UV-Visible light spectrophotometer indicated that the bead-on-string nanofiber with more BN would increase the total release quantity of TCH. The drug released from bead-on-string nanofibers was mainly driven by classical Fickian diffusion. PLGA bead-on-string nanofibers suggest the potential as promising substrate for solid drug particles delivery applications.

Robot-aided electrospinning toward intelligent biomedical engineering

The rapid development of robotics offers new opportunities for the traditional biofabrication in higher accuracy and controllability, which provides great potentials for the intelligent biomedical engineering. This paper reviews the state of the art of robotics in a widely used biomaterial fabrication process, i.e., electrospinning, including its working principle, main applications, challenges, and prospects. First, the principle and technique of electrospinning are introduced by categorizing it to melt electrospinning, solution electrospinning, and near-field electrospinning. Then, the applications of electrospinning in biomedical engineering are introduced briefly from the aspects of drug delivery, tissue engineering, and wound dressing. After that, we conclude the existing problems in traditional electrospinning such as low production, rough nanofibers, and uncontrolled morphology, and then discuss how those problems are addressed by robotics via four case studies. Lastly, the challenges and outlooks of robotics in electrospinning are discussed and prospected.