Leilei Zhang

Coaxial electrospray of microparticles and nanoparticles for biomedical applications

Coaxial electrospray is an electrohydrodynamic process that produces multilayer microparticles and nanoparticles by introducing coaxial electrified jets. In comparison with other microencapsulation/nanoencapsulation processes, coaxial electrospray has several potential advantages such as high encapsulation efficiency, effective protection of bioactivity and uniform size distribution. However, process control in coaxial electrospray is challenged by the multiphysical nature of the process and the complex interplay of multiple design, process and material parameters. This paper reviews the previous works and the recent advances in design, modeling and control of a coaxial electrospray process. The review intends to provide general guidance for coaxial electrospray and stimulate further research and development interests in this promising microencapsulation/nanoencapsulation process.

Multifunctional microbubbles for image-guided antivascular endothelial growth factor therapy.

We synthesize multifunctional microbubbles (MBs) for targeted delivery of antivascular endothelial growth factor (antiVEGF) therapy with multimodal imaging guidance. Poly-lactic-co-glycolic acid (PLGA) MBs encapsulating Texas Red dye are fabricated by a modified double-emulsion process. Simultaneous ultrasound and fluorescence imaging are achieved using Texas Red encapsulated MBs. The MBs are conjugated with Avastin, an antiVEGF antibody for treating neovascular age-related macular degeneration (AMD). The conjugation efficiency is characterized by enzyme-linked immunosorbent assay (ELISA). The efficiency for targeted binding of Avastin-conjugated MBs is characterized by microscopic imaging. Our work demonstrates the technical potential of using multifunctional MBs for targeted delivery of antiVEGF therapy in the treatment of exudative AMD.

Coaxial Electrospray of Ranibizumab-Loaded Microparticles for Sustained Release of Anti-VEGF Therapies

Age-related macular degeneration (AMD) is the leading cause of vision loss and blindness in people over age 65 in industrialized nations. Intravitreous injection of anti-VEGF (vascular endothelial growth factor) therapies, such as ranibizumab (trade name: Lucentis), provides an effective treatment option for neovascular AMD. We have developed an improved coaxial electrospray (CES) process to encapsulate ranibizumab in poly(lactic-co-glycolic) acid (PLGA) microparticles (MPs) for intravitreous injection and sustained drug release. This microencapsulation process is advantageous for maintaining the stability of the coaxial cone-jet configurations and producing drug-loaded MPs with as high as 70% encapsulation rate and minimal loss of bioactivitiy. The utility of this emerging process in intravitreous drug delivery has been demonstrated in both benchtop and in vivo experiments. The benchtop test simulates ocular drug release using PLGA MPs encapsulating a model drug. The in vivo experiment evaluates the inflammation and retinal cell death after intravitreal injection of the MPs in a chick model. The experimental results show that the drug-load MPs are able to facilitate sustained drug release for longer than one month. No significant long term microglia reaction or cell death is observed after intravitreal injection of 200 μg MPs. The present study demonstrates the technical feasibility of using the improved CES process to encapsulate water-soluble drugs at a high concentration for sustained release of anti-VEGF therapy.

Experimental design and instability analysis of coaxial electrospray process for microencapsulation of drugs and imaging agents

Abstract. Recent developments in multimodal imaging and image-guided therapy requires multilayered microparticles that encapsulate several imaging and therapeutic agents in the same carrier. However, commonly used microencapsulation processes have multiple limitations such as low encapsulation efficiency and loss of bioactivity for the encapsulated biological cargos. To overcome these limitations, we have carried out both experimental and theoretical studies on coaxial electrospray of multilayered microparticles. On the experimental side, an improved coaxial electrospray setup has been developed. A customized coaxial needle assembly combined with two ring electrodes has been used to enhance the stability of the cone and widen the process parameter range of the stable cone-jet mode. With this assembly, we have obtained poly(lactide-co-glycolide) microparticles with fine morphology and uniform size distribution. On the theoretical side, an instability analysis of the coaxial electrified jet has been performed based on the experimental parameters. The effects of process parameters on the formation of different unstable modes have been studied. The reported experimental and theoretical research represents a significant step toward quantitative control and optimization of the coaxial electrospray process for microencapsulation of multiple drugs and imaging agents in multimodal imaging and image-guided therapy.

Novel coaxial atomization processes for microfabrication of multi-layered biodegradable microcapsules

Experimental and theoretical studies on coaxial atomization process of fabricating multifunctional microcapsules were performed to overcome the limitation of commonly used microfabrication processes. The coaxial electrospray was first developed, and then a novel process named coaxial electro-flow focusing which combined coaxial electrospray with coaxial flow focusing was proposed. The process was characterized by the formation of a coaxial liquid jet in the core of a high-speed co-flowing gas stream under an axial electric field and the breakup of the liquid jet into fine microcapsules. The effects of main process parameters on the meniscus attached to the mouth of the coaxial needle were tested. A theoretical model was further implemented for instability analysis of the coaxial jet to guide the process control and optimization. As a result, stable cone-jet configurations in a wide range of process parameters and microcapsules with good morphologies were obtained. The reported research represents the first step toward quantitative control and optimization of the coaxial atomization process for the microfabrication of multifunctional microcapsules in multimodal imaging and image-guided therapy.

Coaxial electrospray for multimodal imaging and image-guided therapy

Recent development in multimodal imaging and image-guided therapy requires multifunctional microparticles that encapsulate several imaging and therapeutic agents in the same carrier for simultaneous detection and treatment of the diseases. However, commonly used microfabrication processes for these microparticles have multiple limitations such as the low encapsulation efficiency and the loss of bioactivity for the encapsulated biological cargos. To overcome these limitations, we have carried out both the experimental and the theoretical studies on coaxial electrospray of poly(lactide-co-glycolide) PLGA microparticles. On the experimental side, a coaxial electrospray setup has been developed and tested. The setup consists of a customized coaxial needle assembly, two ring electrodes, two high-voltage power supplies, two syringe infusion pumps, a particle collection reservoir, and a process monitoring system. On the theoretical side, a classical normal mode method has been used for instability analysis of the coaxial electrified jet based on the experimental parameters. The effects of different dimensionless process parameters on the formation of different unstable modes have also been studied. The reported research represents the first step toward the quantitative control and optimization of the coaxial electrospray process for the fabrication of multifunctional microparticles in multimodal imaging and image-guided therapy.

Electrospray of multifunctional microparticles for image-guided drug delivery

Anti-VEGF therapies have been widely explored for the management of posterior ocular disease, like neovascular age-related macular degeneration (AMD). Loading anti-VEGF therapies in biodegradable microparticles may enable sustained drug release and improved therapeutic outcome. However, existing microfabrication processes such as double emulsification produce drug-loaded microparticles with low encapsulation rate and poor antibody bioactivity. To overcome these limitations, we fabricate multifunctional microparticles by both single needle and coaxial needle electrospray. The experimental setup for the process includes flat-end syringe needles (both single needle and coaxial needle), high voltage power supplies, and syringe pumps. Microparticles are formed by an electrical field between the needles and the ground electrode. Droplet size and morphology are controlled by multiple process parameters and material properties, such as flow rate and applied voltage. The droplets are collected and freezing dried to obtain multifunctional microparticles. Fluorescent beads encapsulated poly(DL-lactide-co-glycolide) acid (PLGA) microparticles are injected into rabbits eyes through intravitreal injection to test the biodegradable time of microparticles.

Precision molding of optics: a review of its development and applications

Compression molding of precision optics is gradually becoming a viable manufacturing process for low cost high performance optical elements. In this process, a glass preform in the form of gob or disk is heated rapidly above its glass transition temperature then pressed between two optical mold halves to finish dimensions. The molded lens is first cooled slowly then at a fast cooling rate to room temperature to complete the process. For more than a decade, the authors have conducted a collaborated research in glass molding using both experiments and numerical modeling. In this presentation, we will discuss the recent work in molding of both conventional glass optics and extreme high temperature glass optics – fused silica material. In addition, development of graphene like coatings for precision glass molding will also be described.

Bevacizumab (Avastin) conjugated microbubbles for anti-VEGF treatment of neovascular age-related macular degeneration

Bevacizumab (Avastin) has been used as one of the anti-VEGF therapies to manage neovascular age-related macular degeneration (AMD). The drug delivery system for bevacizumab needs to be improved in order to decrease the frequency of injection and reduce the adverse effects. In our study, bevacizumab was conjugated with poly (lactic-co-glycolic acid) (PLGA) microbubbles by activating carboxyl functional groups. The averaged size of microbubbles was estimated 1.055±0.258μm, allowing for ultrasound guided drug delivery. The binding efficiency between bevacizumab and microbubbles was evaluated in an enzyme-linked immunosorbent assay plate. The test results demonstrated the potential of using PLGA microbubbles to deliver bevacizumab with imaging guidance.