Hydrogel Microneedle Patch Technology

Hydrogel microneedles are mechanically strong enough to penetrate the skin and absorb tissue fluid upon implantation, resulting in the swelling of the polymer and the subsequent formation of a continuous, unblockable hydrogel duct, which opens a diffusion channel for drug release and allows the drug to be released and exert its therapeutic effect in the body. The gelation of hydrogel can be achieved by various mechanisms, including physical cross-linking of polymer chains, electrostatic interactions and covalent chemical cross-linking, and finally forming a hydrophilic polymer network that absorbs water and swells, which has a porous structure and can encapsulate the drug to reduce the loss of drug during transportation and enhance the therapeutic effect of the drug.

Fig. 1 Schematic illustration of the microneedle sensor patch. (Zhang et al., 2022)

Preparation of Hydrogel Microneedles

Hydrogel microneedles have a variety of preparation methods, which vary with the hydrogel material and cross-linking mechanism. The preparation materials include natural polymers (e.g. hyaluronic acid, gelatin, agar, etc.) and synthetic polymers (e.g. polyvinyl alcohol, sodium polyacrylate, methacrylic acid polymers, etc.), which can be physically cross-linked, electrostatically cross-linked or chemically cross-linked to form hydrogels, and finally hydrogel microneedles are prepared by the template method.

Advantages of Hydrogel Microneedles

Hydrogel microneedles can be loaded on the back to greatly increase the drug loading capacity, there is no drug homogeneity problem, and it can be completely removed after use without residue in the body. The preparation process of hydrogel microneedles is similar to that of soluble microneedles in terms of convenience, speed and processability, and low cost of preparation. Hydrogel microneedles can increase the drug delivery capacity and also achieve controlled drug release by regulating the crosslinking network. Since hydrogels can aspirate tissue fluids, they can also be used to extract tissue fluids for biochemical assays. Hydrogel microneedles can also be used in wound dressings, where their adhesive effect can be improved by processing the microneedle structure.

Applications of Hydrogel Microneedles

• Treatment of tumors

Tumor treatment methods include surgical resection, chemotherapy and radiation therapy, etc. Surgical resection is extremely harmful to patients and has the risk of easy recurrence. As a new generation of transdermal drug delivery method, hydrogel microneedle can overcome the barrier of skin stratum corneum and create a series of microchannels for effective drug penetration.

• Treatment of diabetes mellitus

Diabetes is one of the most common chronic diseases, and its blood glucose levels are difficult to control. Patients need to test their blood glucose levels daily and take regular insulin injections or medications to continuously control their blood glucose levels. The testing of hydrogel microneedles can achieve painless sampling and control the release of insulin.

• Rheumatoid arthritis

Rheumatoid arthritis is a systemic disease involving multiple joints, with an extremely complex etiology and pathogenesis, involving multiple joints at the site of onset. Early drug treatment is mostly oral, but long-term use of anti-rheumatic drugs can have significant toxic side effects. Hydrogel microneedles can be used as a carrier for drugs and protein inhibitors, penetrating the keratin layer of the skin to deliver targeted therapeutic drugs or protein inhibitors, reducing the adverse effects of drugs on the gastrointestinal tract.

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