Microneedles

Author

Pharm. Gita Parviz

"Microneedle patch or pen is a novel method designed for topical drug delivery."

Title: | What is microneedles? | Types of microneedles | Comparing to conventional drug administration methods, what are the microneedles’ superiorities? | What are the possible medical applications for microneedles? | What are under review or currently approved drug delivery systems in the form of microneedles?

What is microneedles?

Microneedle patch or pen is a novel method designed for topical drug delivery. The boldest difference between the microneedle-based drug delivery systems and other conventional drug administration methods is their appearance. The microneedle patches are made of two major portions: the underlying flat base and micron-sized needles elongated perpendicular to the supporting base in which active pharmaceutical agent is either loaded inside, adhered to the surface of the extended needles, or applied following the microneedling process, whereas microneedle (or microneedling) pen is a pen-shaped equipment accessorized with various needle sizes and pin numbers cosmetologically used. In topical drug administration, local or systemic, stratum corneum, the outermost skin layer built of dead cells acting as a protective barricade, is the therapy efficacy limiting factor and the premise behind this manner is enabling direct drug delivery into the deep layers beneath the stratum corneum. The targeted effect can be either local or systemic; while cosmetological usages demand deep local administration, generalized internal outcome is achievable if the drug reaches the blood circulation. The size of needles varies in the range of 0.15 – 2.5 millimeter depending to the thickness of stratum corneum and the purposed application.

Types of microneedles

Solid microneedles

Primarily made of metal, ceramic, glass or silicon, solid microneedles can be installed on microneedle patch or pen and are used for channel creation. These needles don’t carry intended active agent; therefore, it should be applied after the microneedling process. High drug concentration can be applied for several hours following the procedure. It might be necessary to combine the main drug with a pore opener to prolong the therapy duration. Cosmetology is the main usage area for solid microneedles.

Coated microneedles

Coated microneedles are solid microneedles coated with a water-based matrix containing the active agent. The outstanding advantage of the coated microneedles is the rapid onset; however, the efficacy duration is practically short and, in most cases, deliverable drug concentration is not enough.

Polymeric microneedles

Dissolving microneedles

Cellulose-based polymers and saccharides (e.g. carboxymethyl cellulose (CMC) and sucrose, respectively) are water-soluble and biodegradable biomaterials frequently preferred in dissolving microneedles’ production. The intended active agent is dissolved inside the needle’s formulation and released concurrent with needle dissolution. In this system, the drug release rate can be adjusted via dissolution rate; microneedles made of fast-dissolved biomaterials have faster and shorter action.

Hydrogel microneedles

Similar to dissolving, hydrogel microneedles are composed of water-friendly polymers. On the other hand, the drug release process isn’t empowered via dissolution, it is the result of osmotic pressure difference created between the extracellular space and the hydrogel. These microneedles have slow degradation rate and are capable of including high drug concentration.

Comparing to conventional drug administration methods, what are the microneedles’ superiorities?

⇒ Reduction of pain, discomfort, skin irritation, and the risk of infection

⇒ Cost-friendly

⇒ Enhancement of the drug amount available for the action

⇒ Lower drug-induced toxicity

⇒ Maintenance of constant blood drug concentration for several days

What are the possible medical applications for microneedles?

Cancer therapy

Patient compliance and life quality improvement are the outstanding demands of cancerous patients. The delivery of neoplastic agents via painless microneedle patches can cover both previously mentioned requirements.

Vaccination

The route of administration for a successful vaccination is highly crucial. Theoretically, vaccination through skin would be feasible if the active agent reached the underlying muscular cells. The presence of stratum corneum is the limiting factor in this hypothesis that can be resolved with the aid of microneedles. As a result, vaccination with dissolving microneedle patches has been a rising trend in the medical world.

Insulin delivery

Studies show that insulin-loaded microneedles that dissolves rapidly within an hour can be a proper replacement for annoying daily insulin injections. It has been demonstrated that, comparing to conventional insulin pen, insulin-carrying microneedle patch suppresses blood glucose much faster followed by uncomplicated patient recovery.

treatment of infectious diseases

Viral infections

Many topically applied antiviral agents, such as acyclovir and long-acting antiretroviral (ARV) medicines, have poor therapeutic outcomes since they cannot penetrate into the deep layers which are the main target region; therefore, the incorporation of these agents in the microneedle patches increases the drug concentration in the demanded area and consequently ameliorates the clinical outcomes.

Bacterial infections

Antibiotics that are loaded in the dissolving microneedles can be a feasible replacement for invasive drug delivery routes such as intravenous injection. Being cost-effective, painless, not requiring professional intervention, and easy to apply are patient-related benefits. Moreover, having control on the drug release rate is the pharmaceutical advantage of these systems.

What are under review or currently approved drug delivery systems in the form of microneedles?

⇒ Dermaroller® (Wolfenbütel, Germany)

⇒ MicroHyala® (CosMED, Kyoto, Japan)

⇒ The MicronJet600® (NanoPass, Is microneedle-based Qtrypta® patch for the delivery of zolmitriptan

⇒ The MicronJet600® (NanoPass, Israel) microneedle system

⇒ Nanopatch® developed at the University of Queensland

⇒ Vaxxas nanotech needle-free vaccines

Currently, the utilization of microneedles in various medical aspects is being investigated. The numerous superiorities of this drug delivery system to the old-fashion administration routes are undeniable. Consequently, we can say that microneedle patches will replace the conventional drug delivery methods in the close future.