Microneedles are getting popular for delivery of drugs, vaccines and growth factors. it is cheap and painless. It is being increasingly used by Cosmetic Physicians to deliver Vit C to stimulate extracellular matrix proteins (collagen) in the skin.
This paper might be helpful, plz check out.
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Article Challenges and Opportunities in dermal/transdermal Delivery
Transdermal drug delivery system has now becoming more and more important to deliver different drugs in an effective and quick manner with minimal side effects and maximum bioavailability. But, the success of this type of drug delivery system has been severely limited by the inability of most drugs to enter the skin at therapeutically useful rates. Recently, the use of micron-scale needles in increasing skin permeability has been introduced and shown to dramatically increase transdermal delivery, especially for macromolecules. With the advent of micro-electro mechanical systems (MEMS), the field of transdermal drug delivery has seen the emergence of new technologies to bypass the skin’s protective barriers. These are designed in order to reduce pain upon injection, and reduce infection risks and skin irritations at the injection site. Microneedles (MN) can be classified into hollow or solid types. Hollow needles allow the injection of a fluid into the skin. Solid needles are used, either as a pretreatment to make the skin permeable to drugs, or in combination with a coating. Dissolvable needles have also been developed recently. For all those MN types, insuring correct insertion into the skin with a reasonable force is very important, not only for proper administration, but also regarding pain.
MNs have been used to increase the permeability of countless drug molecules. From the permeability experiments it has been shown that an increase in insertion force increased the amount of drug permeation. Thus, an insufficient force may not help the drug to pass through the skin regardless of the geometry of the MNs. Hence, the length of the MN and the force applied on the MNs are important factors that can greatly affect the permeation, subsequently sub or supra-therapeutic concentration of the drug.
There is a phenomenon referred to as “bed of nails” that was born from the observation that, when needles are placed too close to each other, they fail to pierce the skin. While the phenomenon has not been extensively documented in the context of microneedle insertion, some papers mention it.
Delivery of drugs by transdermal route adds the potential for side effects in the form of skin irritation at the delivery site, which is true for MN also. Skin irritation reactions include irritant contact dermatitis (ICD), an inflammatory response caused by repeated or direct exposure of the skin to weak irritants, and allergic contact dermatitis (ACD), delayed, T-cell-mediated inflammatory response to a specific allergen. ICD reactions range from erythema and scaling to necrotic burns while ACD reactions include erythema, edema and occasionally vesiculation. Additionally, the onset of ACD reactions is highly variable, and is dependent on the irritant that initiated the reaction and the individual who expresses the allergic response.
For further information, please consult:
1. Teo A, Shearwood C, Ng K, Lu J, Moochhala S, “Transdermal microneedles for drug delivery applications”. Materials Sci Eng, 2006, B 132, pp 151–154.
2. Stoeber B, Liepmann D, “Arrays of hollow out-of-plane microneedles for drug delivery”. J Microelectromechanical Systems, 2005, Vol 14, pp 472–479.
3. Yung K, Xu Y, Liu H, Tam K, Ko S, Kwan F, Lee Y, “Sharp-tipped plastic hollow microneedle array by microinjection moulding”. J Micromechanical Microeng, 2012, Vol 22, p 1–10.
4. Cheung K, Han T, Das DB. Effect of Force of Microneedle Insertion on the Permeability of Insulin in Skin. J Diabetes Sci Technol. 2014 May; 8(3): 444–452.
Transdermal drug delivery
Mark R. Prausnitz1 and Robert Langer2
Abstract
Transdermal drug delivery has made an important contribution to medical practice, but has yet to fully achieve its potential as an alternative to oral delivery and hypodermic injections. First-generation transdermal delivery systems have continued their steady increase in clinical use for delivery of small, lipophilic, low-dose drugs. Second-generation delivery systems using chemical enhancers, non-cavitational ultrasound and iontophoresis have also resulted in clinical products; the ability of iontophoresis to control delivery rates in real time provides added functionality. Third-generation delivery systems target their effects to skin’s barrier layer of stratum corneum using microneedles, thermal ablation, microdermabrasion, electroporation and cavitational ultrasound. Microneedles and thermal ablation are currently progressing through clinical trials for delivery of macromolecules and vaccines, such as insulin, parathyroid hormone and influenza vaccine. Using these novel second- and third-generation enhancement strategies, transdermal delivery is poised to significantly increase impact on medicine.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2700785/
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