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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