morphological and mechanical characterization of exosome loaded microneedle patches

Microneedle Patches for Sustained Delivery of Exosomes in Biomedical Applications

Exosomes, which are small vesicles released by cells into the extracellular matrix, have been proposed as potential biotherapeutics and drug delivery vectors for the treatment of several diseases and cancers1. During their biogenesis process, exosomes encapsulate various biologically active molecules from within the cells, including functional proteins and nucleic acids2. As a result, when taken up by recipient cells during the transport process, exosomes have the ability to modulate gene expression and cellular functions in the target cells3. As a kind of natural information messenger, exosomes have been fully taken advantage of in tissue regeneration, immune regulation, and as a delivery carrier4. Through engineering techniques, specific ligands can be enriched on the surface of exosomes, enabling the induction or inhibition of signaling events in recipient cells or targeting specific cell types5. Chemotherapeutic agents can also be loaded into exosomes for cancer treatment6. Moreover, exosomes have the ability to cross the blood-brain barrier for therapeutic cargo delivery, making them highly promising for the treatment of brain disorders7. Compared to liposomes, exosomes exhibit enhanced cellular uptake and improved biocompatibility8. They are capable of efficiently entering other cells while demonstrating better tolerance and lower toxicity9. However, the traditional bolus injection of exosomes is prone to sequestration and rapid clearance by the liver, kidneys, and spleen in the bloodstream10. Moreover, exosomes have poor stability in vitro and are susceptible to storage conditions, which restrict their clinical applications11.
Microneedles, an array of micrometric-sized needle tips, have the capability to penetrate physiological barriers for the delivery of small molecule drugs12, proteins13, nucleic acids14, and nanomedicines15. Microneedles are precisely engineered to target lesions on the skin surface, and their dispersed tips ensure uniform drug distribution at the targeted site, thus amplifying their therapeutic impact16. The design and material composition of microneedles facilitate&#160;the dry storage of bioactive substances such as proteins and nucleic acids, enhancing their stability17. Traditional injection methods have a relatively short duration of action and can cause pain, inducing fear in patients18. The micrometer-sized length of microneedle minimizes tissue trauma and prevents nerve stimulation, thereby eliminating pain and improving patient compliance19. Additionally, the user-friendly nature of microneedles allows patients to self-administer the treatment without the need for specialized personnel16. In addition to the skin, microneedles can also be used in tissues such as the eyes20, oral mucosa21, heart22, and blood vessels23. The application of microneedles for the clinical delivery of exosomes provides a promising and prospective strategy.
Hence, we introduce an exosome-loaded microneedle (exo@MN) patch and disclose its fabrication method. The microneedle patches were fabricated using a two-step casting method, along with centrifugation and vacuum drying, which promotes the aggregation of exosomes at the microneedle tips, thereby enhancing delivery efficiency. Both the needle tips and backing were constructed using materials that exhibit excellent biocompatibility and water solubility. Trehalose and hyaluronic acid (HA) were incorporated as tip materials to provide protection for the exosomes, and polyvinylpyrrolidone (PVP) dissolved in absolute ethanol was chosen as the backing material. The morphology of the microneedle patch was characterized using microscopy and scanning electron microscope&#160;(SEM). The mechanical testing of the microneedle was assessed using a tensile meter to confirm their capability to penetrate the skin, and the release rate on pig skin was investigated to be 60 s. Furthermore, the morphology, size, and protein content of both fresh exosomes and exosomes in exo@MN were characterized using transmission electron microscope&#160;(TEM), nanoparticle tracking analysis (NTA), and western blotting (WB). The internalization of exosomes by dendritic cells (DCs) was characterized using confocal laser scanning microscope&#160;(CLSM), and the maturation of DCs was evaluated through flow cytometry. The morphological characterization and biological functions of the two types of exosomes are essentially consistent.

Author Spotlight: Innovative Microneedle-Based Strategies for Enhanced Exosome Delivery and Stability

Fabrication and Characterization of Microneedle Patches for Loading and Delivery of Exosomes

My research focused on the efficient development of exosomes, the development of the microneedle strategy can increase exsome stability, enhance provide more possibility for the clinical application of exosomes. We will successfully develop the for advanced microneedle delivery systems. Those include self-healing porous microneedles for sustained drug delivery, ultrasound microneedle device for rapid loading and delivery of drugs, and cryomicroneedles for delivery of living cell, and sugar microneedles for delivery of exosomes.We use microneedle to pierce the biological barrier and then deliver exocells directly to the vector area efficiently. By storing them dry, we enhance their stability, making them precise, easy, and convenient for both clinical and home use. My lab, we focused on key technologies for developing the advanced microneedle-based delivery systems and that can load and deliver various therapeutics.Includes MRA, small molecular drug, antibodies, cell, and exosome. We are also investigate their chemical and physical properties and therapeutic efficacy in different biomedical applications.

Morphological and Mechanical Characterization of Exosome Loaded Microneedle Patches

To begin, prepare the exosome loaded microneedle patch and paste its backing onto a 45-degree inclined surface. Position the patch under a stereo microscope. Turn on the illuminator and capture the morphology of the patch using a four times objective lens.For mechanical testing, cut out a three-by-three array from the patch and place it with the tips facing upwards on the rigid platform of a tensile meter. Adjust the height of the probe to bring it close to the needle tips without touching them. Set the parameters to stop automatically when the pressure reaches 20 Newton.Compress the needle tips vertically at a 0.5 millimeter per minute speed before recording the load versus displacement profile. The tips in the exosome loaded microneedle patch exhibited a conical shape arranged in a 10-by-10 array with sharp and intact needle tips. The tip of the microneedle can withstand the force of two Newtons, allowing it to penetrate through the skin barrier.

morphological-mechanical-characterization-exosome-loaded-microneedle

Research

JoVE Journal

Bioengineering

Exosomes, as emerging &#34;next-generation&#34; biotherapeutics and drug delivery vectors, hold immense potential in diverse biomedical fields, ranging from drug delivery and regenerative medicine to disease diagnosis and tumor immunotherapy. However, the rapid clearance by traditional bolus injection and poor stability of exosomes restrict their clinical application. Microneedles serve as a solution that prolongs the residence time of exosomes at the administration site, thereby maintaining the drug concentration and facilitating sustained therapeutic effects. In addition, microneedles also possess the ability to maintain the stability of bioactive substances. Therefore, we introduce a microneedle patch for loading and delivering exosomes and share the methods, including isolation of exosomes, fabrication, and characterization of exosome-loaded microneedle patches. The microneedle patches were fabricated using trehalose and hyaluronic acid as the tip materials and polyvinylpyrrolidone as the backing material through a two-step casting method. The microneedles demonstrated robust mechanical strength, with tips able to withstand 2 N. Pig skin was used to simulate human skin, and the tips of microneedles completely melted within 60 s after skin puncture. The exosomes released from the microneedles exhibited morphology, particle size, marker proteins, and biological functions comparable to those of fresh exosomes, enabling dendritic cells uptake and promoting their maturation.

Exosomes possess significant clinical potential, but their practical application is limited due to easy in vivo clearance and poor stability. Microneedles present a solution by enabling localized delivery by puncturing physiological barriers and dry-state preservation, thereby addressing the limitations of exosome administration and expanding their clinical utility.

Exosomes, as emerging &#34;next-generation&#34; biotherapeutics and drug delivery vectors, hold immense potential in diverse biomedical fields, ranging ...

Isolation of Exosomes from Mouse Ovarian Epithelial Cancer Cells for Generating Microneedle Patch

To begin, take cultured mouse ovarian epithelial cancer cells. Remove the culture medium from the Petri dishes and wash twice with DPBS. Add 20 milliliters of Dulbecco's Modified Eagle Medium without FBS and penicillin-streptomycin solution.Incubate at 37 degrees Celsius and 5%carbon dioxide for 48 hours. Then collect the cell culture supernatant from 20 Petri dishes of 15-centimeter diameter. Centrifuge at 300 G for 10 minutes at four degrees Celsius and collect the supernatant.Centrifuge the supernatant at 2, 000 G for 10 minutes at four degrees Celsius, and collect the supernatant to remove cellular debris. Now turn on the vacuum pump and connect it to the air inlet of the vacuum filtration system. Filter the supernatant through the 0.22-micron polyethersulfone membrane to remove vesicles or impurities larger than 0.22 microns.Add 15 milliliters of the filtered supernatant to the inner tube of the 100-kilodalton ultrafiltration tube. Centrifuge at 3, 500 G for 10 minutes at four degrees Celsius. Then remove the liquid from the outer tube.Next, collect the liquid from the inner tube. Add one milliliter of DPBS to the inner tube. Pipette repeatedly to resuspend exosomes, and then collect them.Centrifuge the liquid at 10, 000 G for 60 minutes at four degrees Celsius. Transfer the supernatant to a six-milliliter quick-snap centrifuge tube and seal it with a heat sealer. Cut open the tube after ultracentrifuging the supernatant for two hours.Once the supernatant is removed, resuspend the pellet in 100 microliters of DPBS to obtain the exosome solution.

Fabrication of Microneedle Using Exosomes Isolated from Mouse Ovarian Epithelial Cancer Cells

To begin, mix components A and B of polydimethylsiloxane, or PDMS, in a ratio of 10 to one. After stirring the mixture well, pour the mixture into a master mold. Place the PDMS mold under a pressure of one pound per square inch for 15 minutes to remove air bubbles.Cure the PDMS mold at 60 degrees Celsius for two hours. De-mold to obtain the production mold of the microneedle. Then, clean the production mold with ultra pure water before use.Quantify the protein content of the prepared exosome solution using a BCA assay kit. Add an appropriate amount of DPBS to the exosome solution. Now, prepare a solution of 200 milligrams per milliliter of trehalose using DPBS as the solvent.Stir for 20 minutes to ensure full dissolution. Next, prepare a solution of hyaluronic acid and polyvinylpyrrolidone, or PVP, using DPBS and ethanol as the solvent, respectively. Stir overnight to ensure full dissolution.Mix the exosome solution and trehalose solution in an equal ratio. Add an equal volume of hyaluronic acid solution and mix thoroughly to obtain the tip solution. Using a plasma cleaner, process the surface of the PDMS mold for 30 seconds at a low grade to enhance its hydrophilicity.Add 40 microliters of the tip solution to the PDMS mold. Centrifuge at 3, 000G for three minutes at room temperature to ensure the liquid fills the needle layer of the mold. Remove excess liquid from the mold and dry at room temperature in a vacuum drying oven for one day.Then, add 200 microliters of PVP solution to the PDMS mold. Centrifuge at 3, 000G for three minutes at room temperature to ensure the liquid fills the mold's backing layer. After drying the mold for one day, de-mold to obtain the exosome-loaded microneedle's patch.