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Transdermal drug delivery systems: silicone adhesives for transdermal patches

Our study with more than 20 active ingredients shows that silicone gel adhesives enable targeted drug release – rapid, delayed or constant.

Download study here

Our study reveals how silicone gel adhesives are transforming the release of active ingredients – in cosmetics, nutraceuticals and pharmaceuticals. Release properties can be tailored: steady release, burst release or long-term release.

When it comes to hydrophobic actives, we developed silicone adhesives allowing good mixability and superior release rates, outshining commercially available products.

Study results: silicone gel adhesives for transdermal patches

Here is a summary of our study:

Study focus:

  • New silicone formulations to improve active ingredient release
  • Compatibility with common active ingredients (e.g. caffeine, vitamin E, niacinamide, curcumin, melatonin, retinol/vitamin A1, dexamethasone, ibuprofen; more than 20 substances tested in total)

Key findings

  • Medical silicone gel adhesives are suited for transdermal patches:
    • Stable embedding of active ingredients
    • No phase separation or curing issues
  • Our silicone-based systems showed above-average release against commercial benchmarks
  • Individual release profiles are possible, covering:
    • Steady release
    • Burst release for high active ingredient delivery immediately after application
    • Sustained release for even, long-term delivery

Download the complete study.

Review and evaluation of transdermal drug delivery systems

For the benchmark studies on transdermal drug delivery systems using silicone gel adhesives, our researchers from the WACKER Health Care Competence Center in Ann Arbor, USA, examined the following questions:

  • Substances: Which active ingredients can be integrated into silicone gel adhesives?
  • Processes: How can the active ingredient be integrated as homogeneously as possible?
  • Transdermal drug delivery: How does the active ingredient diffuse from the silicone gel matrix?
  • Customization: Which release profiles can be achieved? (Intended rate of release/treatment goals)

The team used a silicone layer that is a maximum 300 micrometers thin. The Franz diffusion cell methodology was used to evaluate the skin penetration and the release of more than 20 active ingredients.

“We were able to demonstrate an above-average release of 20 active ingredients from the silicone gel matrix. Moreover, we could show that silicone gel adhesives are suitable for the development of novel release profiles.”
Dr. Ufuk Karabiyik, Leading Researcher, Health Care Competence Center in Ann Arbor, USA

Optimum release for medical patches and beauty pads

In many applications, the steady release over time of the active ingredients is important. Silicone gels are ideal for such applications and are therefore a promising alternative to existing pressure-sensitive adhesives.

Transdermal patches deliver active ingredients such as hormones steadily over time.

Administering a cosmetic, nutraceutical, or pharmaceutical active ingredient by means of a transdermal patch or topical ways has several advantages:

  • The active ingredient is steadily absorbed by the patient’s skin.
  • Thus, the medication enters the bloodstream directly.
  • This helps eliminate gastrointestinal side effects.
  • Patches do not need to be replaced frequently.
  • This in turn improves patient compliance.

Today’s dressings can do more than just cover and protect wounds. Equipped as transdermal patches, they have functional layers that can store and release different kinds of active ingredients.

This opens up new possibilities for:

  • Medical applications (e.g. hormone therapy, pain management, treating Alzheimer’s disease)
  • Non-prescription applications (e.g. over-the-counter active ingredients, dietary supplements, herbal remedies)
  • Cosmetic and wellness applications (e.g. anti-aging)
  • Orthotic applications (skin care for an artificial limb)

Predominant types of transdermal patch designs:

Drug-in-adhesive

Reservoir patch design

Sample of SILPURAN® medical silicone adhesive, coated to PU laminate

WACKER has developed a process for systematically manufacturing and testing silicone adhesives for transdermal drug delivery systems. For the tests, we used silicone gel adhesives from the SILPURAN® product portfolio.

They are:

  • Skin-friendly, bio-compatible
  • Anti-allergenic
  • Breathable, odorless
  • Easy to remove and reposition
  • Adjustable in terms of adhesion
  • Adjustable in terms of release of drugs and active ingredients

WACKER’s SILPURAN® silicone gel adhesives are categorized as addition-curing room-temperature vulcanizing silicones (RTV silicones). They consist of two components: the silicone rubber base and the crosslinker.

SILPURAN® silicone gels

  • Form particularly soft vulcanizates
  • Cure precisely at room temperature
  • Show a high degree of purity
  • Secure excellent mechanical strength of the finished product
  • Contain a platinum catalyst (reactivity must be taken into account by processors)

Transdermal patches are increasingly being used for non-prescription and cosmetic applications. WACKER therefore focused on developing silicone gels that can be used for administering the most common substances.

The goal was to achieve maximum and tailored release properties while maintaining the structural integrity of the adhesive coating. The active compound was embedded to a silicone gel matrix that is a maximum 300 micrometers thin.

More than 20 active ingredients have been tested:

  • Therapeutic drugs, e.g. dexamethasone, ibuprofen
  • Non-steroidal anti-inflammatory drugs, e.g. diclofenac
  • Antimicrobial active ingredients
  • Over-the-counter (OTC) active ingredients, such as caffeine and melatonin
  • Dietary supplements, e.g. curcumin
  • Vitamins, e.g. vitamin E, niacinamide (vitamin B3), retinol (vitamin A) and vitamin C
  • Active ingredients commonly utilized for personal care and wellness applications
  • Herbal remedies

We evaluated:

  • Skin permeation (rate at which the incorporated compounds are released and absorbed by the skin)
  • Customized drug release profile
  • Diffusion of active ingredients
  • Optimized adhesive properties (tack, peel and shear)

From raw material to analysis: process for manufacturing and evaluating silicone adhesives for transdermal therapeutic systems.

Download the complete study.

Transdermal drug delivery systems

PDF 7.6 MB English

The Franz diffusion cell method is often used to study skin penetration and the release of active ingredients from various formulations – including transdermal patches.

The release rates were quantified using either the Franz cell methodology or the orbital shaker method.

The Franz diffusion cell system is designed to simulate the behavior of active compounds and formulations when applied to the skin.

In this system, the test sample is placed in contact with a membrane, and the rate of transfer is determined by collecting the permeate on the opposite side of the membrane.

For limited penetration studies, we employed the Strat-M® membrane for transdermal diffusion testing.

Download the complete study.

Transdermal drug delivery systems

PDF 7.6 MB English
“Patches coated with silicone gel adhesives can be customized to the intended rate of release of the active ingredient. Thus, they can be tailored to the treatment goals of the respective application. What’s more, silicone gels display good skin compatibility.”
Dr. Ming Guo, Senior Scientist, Health Care Competence Center in Ann Arbor, USA

Download the complete study here!

Download

  • Silicone gel adhesives for transdermal delivery
  • Product development approach
  • Study design and results
  • Release profiles of retinol (vitamin A1), vitamin B3, vitamin E, caffeine, melatonin and green tea (partly in comparison with commercial patches)

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