3582437623

Wrocław University of Technology

POTENTIAL USE OF HYDROGEL CONTAC LENSES IN DRUG

DELIVERY

Magdalena BAJGROWICZ, Barbara KMIECIK, Jerzy DETNA

e-mail: [e-mail]

Department of Mechanics, Materials Science and Engineering, Wrocław University of Technology, ul. Smoluchowskiego 25, Wrocław, 50-370, Poland

HYDROGELCLs

INTRODUCTION

Nowadays 90% of drugs used to treat eye infections are delivered in a form of eye drops. This method is however very inefficient. Average drug residence time on a surface of the eye is 2-5 min¹. Therefore, the estimated amount of medicine that is absorbed by the cornea during that time is only 1-7% of applied dose, while the rest is washed out by continuous tear flow. That can cause some undesirable side effects and leads to drug wastage. Another disadvantage of eye drops is the fact that to achieve therapeutic drug concentrations over required period of time, drug must be applied very frequently in smali doses, even during nights, what causes patients discomfort especially during sleep². Therefore there is a need for a new drug delivery device that would increase the residence time of the drug in the tear film and provide slow sustained release over reguired period of time.

ADVANTAGES OF CONTACT LENSES

CONTACT LENSES    .

WITH DRUG ■-* \    ->

DRUG PART1CLES    10 MINUTES    2 HOURS    8HOURS

Fig. 1 . Difference between eye drops and contact lens application. (http://ijhas.in/)

•    Limiting pre-corneal drug loss.

•    Creating a reservoir of the drug on the eye surface, so that the drug residence time is prolonged.

•    Over 50% of the drugs released from a CL can diffuse into the cornea, which is at least 35 times morę efficient than eye drops³.

•    Increased efficiency (reduced concentrations of a drug).

•    Decreased potential for side effects as less drug is absorbed to the bloodstream.

•    Elimination of freguent application.

Fig. 2. Drug concentration in a tear film while using eye drops and contact lenses (http://auburn.edu/research/dynamic-dosing-with-contact-lenses/)

CONTACT LENSES MATERIALS

Hydrogel is a water-swollen, and cross-linked polymeric network produced by the simple reaction of one or morę monomers⁴. Hydrogel materials have the ability to absorb and release the incorporated drug or other substances in continuous or controlled manner. The most commonly used polymer is pHEMA poly(2-hydroxyethyl methacrylate).

Depending on the properties of the polymer (polymers) used, the amount of absorbed/released drug is different. FDA divides hydrogel CLs into 4 groups according to their water content and iconicity (tab. 1). Both these parameters determine materiaPs usefulness as drug delivery device.

Tab. 1. FDA contact lenses gropus

łonie lenses tend to attach morę drug than non-ionic lenses. The reason for that is because ionic lenses contain negatively charged polymers which attract positively charged groups (e.g. amino groups) of drugs. Water content can also influence the absorption process. The higher water content the bigger volume of drug solution can be accumulated inside of the lens. In practise ionicity has stronger influence that water content.

Hydrogels currently belong to the popular forms of the drug applied externally. They are widely used in pharmaceutical industry as drug carriers, wound treatments, capsules matrices and coatings⁵.

SILICONE HYDROGEL CLs

In silicone-hydrogel materials, silicone rubber is combined with conventional hydrogel monomers. The silicone component of these lens materials provides extremely high oxygen permeability7, but the water content is very Iow what limits their use in clinical practice. Silicone hydrogel CLs perform much worse release than hydrogel lenses.

FINAŁ REMARKS

>    Although CLs have been proposed as potential drug carriers in 1965⁶ there is still no commercial products available on a market.

>    FDA created special group called therapeutic contact lenses including Pure Vision (Bausch&Lomb), Acuvue 2 (Vistakon), Acuvue Oasys (Vistakon) and Air Optix Night & Day (lAlcon).

>    Futurę research should focus not only on creating new CLs materiał, but also on new measurement systems. Only that would provide reliable data.

RGP RIGID GAS PERMEABLE CLs

RGP lenses are madę of silicone and methacrylic acid polymers, known as silicone acrylates with addition of hydrophilic monomers like fluorinated monomers or n-vinyl pyrrolidone (PVP).

Unfortunately, the raw materiał is naturally hydrophobic, has poor wetting attributes, leading to limited use of these lenses as drug carriers. Adding hydrophilic monomers significantly improves wetting characteristics, but the water content of RPG lenses is still much lower when compared with other soft contact lenses. Low water content and low comfort results in classifying them as poor candidates for drug delivery purposes.

REFERENCES

[1]    Gulsen, D., & Chauhan, A. (2004). Ophthalmic drug delivery through contact lenses. Investigative Ophthalmology & Visual Science, 45(7), 2342-7

[2]    GG, L. G. (1993). Continuous drug delivery through the use of disposable contact lenses. Optom VisSci, 70,1012-8.

[3]    Phan, C.-M., Subbaraman, L., Liu, S., Gu, F., & Jones, L. (2014). In vitro uptake and release of natamycin Dex-b-PLA nanoparticles from model contact lens materials. Journal of Biomaterials Science. Polymer Edition, 25(1), 18-31.

[4]    Ahmed, E. M. (2013). Hydrogel: Preparation, characterization, and applications. Journal of Advanced Research, 6(2), 105-121.

[5]    Tyliszczak B, P. K. (2007). Charakterystyka matryc hydrożelowych - zastosowania biomedyczne superabsorbentówpolimerowych. Czasopismo Techniczne, 1.

[6]    Bourlais, C. L., Acar, L., Zia, H., Sado, P. A., Needham, T., & Leverge, R. (1998). Ophthalmic drug delivery systems-recent advances. Progress in Retinal and Eye Research, 77(1), 33-58.

[7]    16. Sweeney D, Fonn D, E. K. (2006). Silicone hydrogels: the evolution of revolution. Contact Lens Spectrum.