Microneedles and manufacturing method thereof

Injectable microneedles with a porous, water-soluble sacrificial layer that leaves only the tip inside the body

This technology features microneedles composed of a tip containing active ingredients and a porous, water-soluble or hydrolyzable polymer sacrificial layer. These are inserted into the body individually via an injector. The sacrificial layer is designed to dissolve faster than the active ingredients, ensuring only the tip remains within the tissue.

Conventional microneedles require support structures like substrates or patches, which can be uncomfortable as they must remain on the skin while the active ingredients are released. Furthermore, external forces or muscle movement during or after application can shift the microneedles, making it difficult to ensure consistent drug delivery.

This technology precisely separates the tip from the injector by controlling the porosity, pore size, and distribution of the sacrificial layer, which regulates the dissolution rate in the body and resistance to insertion impact. It is manufactured by sequentially filling a mold with the tip and sacrificial layer materials, then bonding the injector using a photocurable medium. Applicable for intradermal vaccine and drug delivery, as well as cosmetic ingredient delivery, it enables stable, long-term sustained release without the need for a patch.

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Key Features:

• Microneedles with tips containing active ingredients that are individually inserted into the body via an injector
• A sacrificial layer comprising a porous, water-soluble or hydrolyzable polymer that contacts the tip and serves as an intermediate bonding medium at the end of the injector
• A sacrificial layer structure that dissolves faster than the active ingredients in biological tissue, with a dissolution rate controlled by its porosity, pore size, and distribution
• A process of forming the tip with an active ingredient mixture in a portion of the mold's intaglio pattern and filling the remainder with polymer to form the sacrificial layer

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This invention was developed with support from the Ministry of Health and Welfare for establishing the production process of silk fibroin microneedle meshes using transfer molding and 3D dispensing techniques, as well as for engineering analysis of device and vascular tissue penetration.

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