Alireza MehrdadfarTransport Phenomena in Biological system

Dec. 7, 2013

Professor: Dr. Osfouri

Modeling of Hydrogels in Controlled release in Drug Delivery

Drug release mechanisms for HydrogelDiffusion Swelling

IntroductionHydrogelDesign & modelling criteria

for hydrogels in drug delivery formulations

OverviewKey findings / results

Results 1Results 2

Conclusion

Fit of the model to the experimentally determined

Conclusion

Since the establishment of the first synthetic hydrogels by Wichterle and Lim in 1954

the growth of hydrogel technologies has advanced many fields ranging from food additives to pharmaceuticals to biomedical implants

A successful drug delivery device relies not only on intelligent network design but also on accurate a priori mathematical modeling of drug release profiles.

In a complimentary fashion, a quantitative mathematical understanding of material properties, interaction parameters, kinetic events, and transport phenomena within complex hydrogel systems assists network design by identifying the key parameters and mechanisms that govern the rate and extent of drug release

Introduction

Hydrogels are polymeric networks that absorb large quantities of water while remaining insoluble in aqueous solutions due to chemical or physical crosslinking of individual polymer chains.

For example, hydrogels are excellent candidates for encapsulating bio macromolecules including proteins and DNA due to their lack of hydrophobic interactions which can denature these fragile species

Hydrogel

Hydrogel

Vp ratio of polymer volume

Vg swollen gel volume

Hydrogel

M¯ n is the average molecular weight of the linear

polymer chains, ν¯ is the specific volume of the

polymer, V1 is the molar volume of water, and χ12 is

the polymer–water interaction parameter

polymer volume fraction in the swollen state

number average molecular weight

between crosslinks

network mesh size

Hydrogel

Modelling & Design criteria for hydrogels Drug delivery

Molecule release mechanisms for hydrogelModelling

Swelling-controlledDiffusion-controlled

Diffusion-controlled delivery systems

Diffusion-controlled is the most widely applicable mechanism for describing drug release from hydrogels. Fick's law of diffusion with either constant or variable diffusion coefficients is commonly used in modeling diffusion-controlled release.

Diffusion-controlled hydrogel delivery systems can be either reservoir or matrix systems

For a reservoir system

Diffusion-controlled delivery systems

For a matrix system

From solving two system

Power law function

Swelling-controlled delivery systems

In diffusion-controlled delivery systems, the time-scale of drug

diffusion, t, (where t=δ(t)2 /D and δ(t) is the time-dependent

thickness of the swollen phase) is the rate-limiting step while in

swelling-controlled delivery systems the time-scale for polymer

relaxation (λ) is the rate limiting step. The Deborah number (De) is

used to compare these two time-scales

Power law function

Diffusion-controlled delivery systems

a sequential layer model

Releases The drug release kinetics of propranolol hydrochloride

in 0.1Mphosphate buffer (pH 7.4)

Fit of the model to the experimentally determined

Hydrogels have played a very important role in biomedical applications. With increasing efforts devoted to controlled molecule release, the applications of hydrogels will continue to grow in the future.

Proper network design and accurate mathematical modeling are keys to tuning the drug release rates as well as to modulating tissue regeneration.

Conclusion

J. Siepmann, N.A. Peppas, Modeling of drug release from delivery systems based on hydroxypropyl methylcellulose (HPMC), Adv. Drug Deliv. Rev. 48 (2001) 139–157.

Chien-Chi Lin, Andrew T. Metters , Hydrogels in controlled release formulations: Network design and mathematical modeling, Adv. Drug Deliv. Rev. 58 (2006) 1379–1408.

References

The End