Controlled release of insulin through hydrogels of (acrylic acid)/trimethylolpropane triacrylate


Hydrogels of poly(acrylic acid) crosslinked with trimethylolpropane triacrylate (TMPTA) were produced through solution polymerization. After these hydrogels were loaded with insulin solution, they evidenced swelling. Experiments of controlled release of insulin through the hydrogels were performed in acidic and basic media in order to evaluate the rates of release of this protein provided by the referred copolymer. Additionally, a mathematical description of the system based on differential mass balance was made and simulated in MATLAB. The model consists of a system of differential equations which was solved numerically. As expected, the values of swelling index at the equilibrium and the rates of insulin release were inversely proportional to the degree of crosslinking. The mathematical model provided reliable predictions of release profiles with fitted values of diffusivity of insulin through the hydrogels in the range of 6.0 × 10−7–1.3 × 10−6 cm2/s. The fitted and experimental values of partition coefficients of insulin between the hydrogel and the medium were lower for basic media, pointing out good affinity of insulin for these media in comparison to the acidic solutions.

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av :

Surface area of the hydrogel per unit of volume (cm−1)

\( C_{A}^{I} \) :

Insulin concentration inside the hydrogel (phase I) (IU/cm3)

\( C_{A,eq}^{II} \) :

Concentration of insulin in phase II in equilibrium with \( \left. {C_{A}^{I} } \right|_{r = R} \)

\( C_{A,i}^{I} \) :

Concentration of insulin in ‘i’ position inside the hydrogel (IU/cm3)

\( C_{A,initial}^{I} \) :

Initial insulin concentration inside the hydrogel (phase I) (IU/cm3)

\( C_{A}^{II} \) :

Insulin concentration in the receiving medium (phase II) (IU/cm3)

DA :

Diffusion coefficient of insulin inside the swollen hydrogel (cm2/s)


Insulin units

kc :

Mass transfer coefficient of insulin in the receiving solution (cm/s)

K P :

Partition coefficient of insulin between phases I and II


Number of points used in the method of lines


Radial direction (cm)


Radius of the hydrogel (cm)


Swelling index


Time of release (s)

VI :

Volume of phase I (cm3)


Volume of phase II (cm3)

wd :

Weight of dried hydrogel (g)

wsw :

Weight of swollen hydrogel (g)


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The authors wish to thank FAPESP (Grant Number 2012/11532-0), CNPq (Grant Number 304321/2011-7) and CAPES for the support.

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Correspondence to Leandro G. Aguiar.

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Raymundi, V.C., Aguiar, L.G., Souza, E.F. et al. Controlled release of insulin through hydrogels of (acrylic acid)/trimethylolpropane triacrylate. Heat Mass Transfer 52, 2193–2201 (2016).

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  • Acrylic Acid
  • Control Release
  • Naltrexone
  • Methacrylic Acid
  • Cupric Sulfate